Pushpendra

2006-10-13T23:31:00.000-07:00

Pushpendra

Why ...................................
Once, Newton came to India and watched a few tamil movies that had his head spinning. He was convinced that all his logic and laws in physics were just a huge pile of junk and apologized for everything he had done.

In the movie of Rajanikanth, Newton was confused to such an extent that he went Paranoid. Here are a few scenes
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1) Rajanikanth has a Brain Tumor which, according to the doctors can't be cured and his death is imminent. In one of the fights, our great Rajanikanth is shot in the head. To everybody's surprise, the bullet passes through his ears taking away the tumor along with it and he is cured! Long Live Rajanikanth!

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2) In another movie, Rajanikanth is confronted with 3 gangsters. Rajanikanth has a gun but unfortunately only one bullet and a knife.

Guess, what he does?

He throws the knife at the middle gangster? & shoots the bullet towards the knife. The knife cuts the bullet into 2 pieces, which kills both the gangsters on each side of the middle gangster & the knife kills the middle one.

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3) Rajanikanth is chased by a gangster. Rajanikanth has a revolver but no bullets in it. Guess, what he does. Nah? not even in your remotest imaginations.

He waits for the gangster to shoot. As soon as the gangster shoots, Rajanikanth opens the bullet compartment of his revolver and catches the bullet. Then, he closes the bullet compartment and fires his gun. Bang... the gangster dies...

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This was too much for our Newton to take! He was completely shaken and decided to go back. But he happened to see another movie for one last time, and thought that at least one movie would follow his theory of physics.

The whole movie goes fine and Newton is happy that all in the world hasn't changed. Oops, not so fast!

The 'climax' finally arrives.

Rajanikanth gets to know that the villain is on the other side of a very high wall. So high that Rajanikanth can't jump even if he tries like one of those superman techniques that our heroes normally use.

Rajanikanth has to desperately kill the villain because it's the climax. (Newton dada is smiling since it is virtually impossible?)

Rajanikanth suddenly pulls two guns from his pockets. He throws one gun in the air and when the gun has reached above the height of the wall, he uses the second gun and shoots at the trigger of the first gun in air.

The first gun fires off and the villain is dead.

Newton commits suicide...

2006-01-28T01:41:00.000-08:00

Pushpendra
Speed Reading - Radically Increasing Your Reading Speed By Pushpendra Singh
Speed Reading helps you to read and understand text more quickly. It is an essential skill in any environment where you have to master large volumes of information quickly, as is the norm in fast-moving professional environments.

The Key Insight
The most important trick about speed reading is to know what information you want from a document before you start reading it: if you only want an outline of the issue that the document discusses, then you can skim the document very quickly and extract only the essential facts. If you need to understand the real detail of the document, then you need to read it slowly enough to fully understand it.
You will get the greatest time savings from speed reading by learning to skim excessively detailed documents.

Technical Issues
Even when you know how to ignore irrelevant detail, there are other technical improvements you can make to your reading style which will increase your reading speed.

Most people learn to read the way young children read - either letter-by-letter, or word-by-word. For most adults, this is probably not the case - think about how your eye muscles are moving now. You will probably find that you are fixing your eyes on one block of words, then moving your eyes to the next block of words, and so on. You are reading blocks of words at a time, not individual words one-by-one. You may also notice that you do not always go from one block to the next: sometimes you may move back to a previous block if you are unsure about something.

A skilled reader will read many words in each block. He or she will only dwell on each block for an instant, and will then move on. Only rarely will the reader's eyes skip back to a previous block of words. This reduces the amount of work that the reader's eyes have to do. It also increases the volume of information that can be examined in a period of time.

A poor reader will become bogged down, spending a lot of time reading small blocks of words. He or she will skip back often, losing the flow and structure of the text and overall understanding of the subject. This irregular eye movement will make reading tiring. Poor readers tend to dislike reading, and may find it harder to concentrate and understand written information.

Speed reading aims to improve reading skills by:
increasing the number of words read in each block
reducing the length of time spent reading each block, and
reducing the number of times your eyes skip back to a previous sentence.
These are explained below:
Increasing the number of words in each block:This needs a conscious effort. Try to expand the number of words that you read at a time. Practice will help you to read faster. You may also find that you can increase the number of words read by holding the text a little further from your eyes. The more words you can read in each block, the faster you will read!
Reducing Fixation Time:The minimum length of time needed to read each block is probably only a quarter of a second. By pushing yourself to reduce the time you take, you will get better at picking up information quickly. Again, this is a matter of practice and confidence.
Reducing Skip-Back:To reduce the number of times that your eyes skip back to a previous sentence, run a pointer along the line as you read. This could be a finger, or a pen or pencil. Your eyes will follow the tip of your pointer, smoothing the flow of your reading. The speed at which you read using this method will largely depend on the speed at which you move the pointer.
You will be able to increase your reading speed a certain amount on your own by applying speed reading techniques.

What you don't get out of self-study is the use of specialist reading machines and the confidence gained from successful speed-reading - this is where a good one-day course can revolutionize your reading skills.

Key points:
By speed reading you can read information more quickly. You may also get a better understanding of it as you will hold more of it in short term memory.

2006-01-28T01:37:00.000-08:00

Pushpendra

A Powerful Approach to Note Taking By pushpendra Singh
Mind Maps are very important techniques for improving the way you take notes. By using Mind Maps you show the structure of the subject and linkages between points, as well as the raw facts contained in normal notes. Mind Maps hold information in a format that your mind will find easy to remember and quick to review.
Popularized by Tony Buzan, Mind Maps abandon the list format of conventional note taking. They do this in favor of a two-dimensional structure. A good Mind Map shows the 'shape' of the subject, the relative importance of individual points and the way in which one fact relates to other.
Mind Maps are more compact than conventional notes, often taking up one side of paper. This helps you to make associations easily. If you find out more information after you have drawn the main Mind Map, then you can easily integrate it with little disruption.

Mind Maps are also useful for:
summarizing information
consolidating information from different research sources
thinking through complex problems, and
presenting information that shows the overall structure of your subject
Mind Maps are also very quick to review, as it is easy to refresh information in your mind just by glancing at one.

Mind Maps can also be effective mnemonics. Remembering the shape and structure of a Mind Map can provide the cues necessary to remember the information within it. They engage much more of the brain in the process of assimilating and connecting facts than conventional notes.

Drawing Basic Mind MapsThis site was researched and planned using Mind Maps. They are too large to publish here, however part of one is shown below. This shows research into time management skills:

To make notes on a subject using a Mind Map, draw it in the following way:
Write the title of the subject in the center of the page, and draw a circle around it. This is shown by the circle marked 1 in the figure 1.
For the major subject subheadings, draw lines out from this circle. Label these lines with the subheadings. These are shown by the lines marked 2 in figure 1.
If you have another level of information belonging to the subheadings above, draw these and link them to the subheading lines. These are shown by the lines marked 3 in figure 1.
Finally, for individual facts or ideas, draw lines out from the appropriate heading line and label them. These are shown by the lines marked 4 in figure 1.
As you come across new information, link it in to the Mind Map appropriately
complete Mind Map may have main topic lines radiating in all directions from the center. Sub-topics and facts will branch off these, like branches and twigs from the trunk of a tree. You do not need to worry about the structure produced, as this will evolve of its own accord.

Note that the idea of 'levels' in Figure 1 is only used to help show how the Mind Map was created. All we are showing is that major headings radiate from the center, with lower level headings and facts branching off from the higher level headings.

While drawing Mind Maps by hand is appropriate in many cases, software tools like MindGenius improve the process by helping to you to produce high quality Concept Maps, which can easily be edited and redrafted.

Improving your Mind MapsYour Mind Maps are your own property: once you understand how to make notes in the Mind Map format, you can develop your own conventions to take them further. The following suggestions may help to increase their effectiveness:
Use single words or simple phrases for information: Most words in normal writing are padding, as they ensure that facts are conveyed in the correct context, and in a format that is pleasant to read. In your own Mind Maps, single strong words and meaningful phrases can convey the same meaning more potently. Excess words just clutter the Mind Map.
Print words: Joined up or indistinct writing can be more difficult to read.
Use color to separate different ideas: This will help you to separate ideas where necessary. It also helps you to visualize of the Mind Map for recall. Color also helps to show the organization of the subject.
Use symbols and images: Where a symbol or picture means something to you, use it. Pictures can help you to remember information more effectively than words.
Using cross-linkages: Information in one part of the Mind Map may relate to another part. Here you can draw in lines to show the cross-linkages. This helps you to see how one part of the subject affects another.
Key points:
Mind Maps provide an extremely effective method of taking notes. They show not only facts, but also the overall structure of a subject and the relative importance of individual parts of it. Mind Maps help you to associate ideas and make connections that might not otherwise make.

2006-01-09T19:26:00.000-08:00

Pushpendra
How to increase you creativity skill
By Pushpendra Singh

Creativity Tools - An Introduction...
The tools in this section can help you to become more creative. They are designed to help you devise creative and imaginative solutions to problems, and help you to spot opportunities that you might otherwise miss.

The section describes the following techniques:
Improving a product or service - Reversal and SCAMPER
Creating new products, services & strategies:Attribute Listing, Morphological Analysis & Matrix Analysis
Generating many radical ideas - Brainstorming
Making creative leaps - Random Input
Widening the search for solutions - Concept Fan
Looking at problems from different perspectives - Reframing Matrix
Carrying out thought experiments - Provocation
A simple process for creativity - DO IT
A powerful integrated problem solving process - Simplex
Subconscious problem solving
Before you continue, it is important to understand what we mean by creativity, as there are two completely different types. The first is technical creativity, where people create new theories, technologies or ideas. This is the type of creativity we discuss here. The second is artistic creativity, which is more born of skill, technique and self-expression. Artistic creativity is beyond the scope of these articles.

Many of the techniques in this chapter have been used by great thinkers to drive their creativity. Albert Einstein, for example, used his own informal variant of Provocation to trigger ideas that lead to the Theory of Relativity.

Approaches to CreativityThere are two main strands to technical creativity: programmed thinking and lateral thinking. Programmed thinking relies on logical or structured ways of creating a new product or service. Examples of this approach are Morphological Analysis and the Reframing Matrix.

The other main strand uses 'Lateral Thinking'. Examples of this are Brainstorming, Random Input and Provocation. Lateral Thinking has been developed and popularized by Edward de Bono, whose books you can find in the appropriate articles.

Programmed Thinking & Lateral Thinking
Lateral thinking recognizes that our brains are pattern recognition systems, and that they do not function like computers. It takes years of training before we learn to do simple arithmetic - something that computers do very easily. On the other hand, we can instantly recognize patterns such as faces, language, and handwriting. The only computers that begin to be able to do these things do it by modeling the way that human brain cells work . Even then, computers will need to become more powerful before they approach our ability to handle patterns.

The benefit of good pattern recognition is that we can recognize objects and situations very quickly. Imagine how much time would be wasted if you had to do a full analysis every time you came across a cylindrical canister of effervescent fluid. Most people would just open their can of fizzy drink. Without pattern recognition we would starve or be eaten. We could not cross the road safely.

Unfortunately, we get stuck in our patterns. We tend to think within them. Solutions we develop are based on previous solutions to similar problems. Normally it does not occur to us to use solutions belonging to other patterns.

We use lateral thinking techniques to break out of this patterned way of thinking.

Lateral thinking techniques help us to come up with startling, brilliant and original solutions to problems and opportunities.

It is important to point out that each type of approach has its strength. Logical, disciplined thinking is enormously effective in making products and services better. It can, however, only go so far before all practical improvements have been carried out. Lateral thinking can generate completely new concepts and ideas, and brilliant improvements to existing systems. In the wrong place, however, it can be sterile or unnecessarily disruptive.

Taking the best of each...
A number of techniques fuse the strengths of the two different strands of creativity. Techniques such as the Concept Fan use a combination of programmed and lateral thinking. Do it and Min Basadur's Simplex embed the two approaches within problem solving processes. While these may be considered 'overkill' when dealing with minor problems, they provide excellent frameworks for solving difficult and serious ones.

The Creative Frame of MindOften the only difference between creative and uncreative people is self-perception. Creative people see themselves as creative and give themselves the freedom to create. Uncreative people do not think about creativity and do not give themselves the opportunity to create anything new.

Being creative may just be a matter of setting aside the time needed to take a step back and allow yourself to ask yourself if there is a better way of doing something. Edward de Bono calls this a 'Creative Pause'. He suggests that this should be a short break of maybe only 30 seconds, but that this should be a habitual part of thinking. This needs self-discipline, as it is easy to forget.

Another important attitude-shift is to view problems as opportunities for improvement. While this is something of a cliché, it is true. Whenever you solve a problem, you have a better product or service to offer afterwards.

Using CreativityCreativity is sterile if action does not follow from it. Ideas must be evaluated, improved, polished and marketed before they have any value. Other sections of Mind Tools lay out the evaluation, analysis and planning tools needed to do this. They also explain the time and stress management techniques you will need when your creative ideas take off.
Reversal - Improving Products and Services

How to use tool:
Reversal is a good tool for improving a product or a service. To use it, ask the opposite of the question you want to ask, and apply the results.

Example:
Imagine that you want to improve the response of a service center. Using Reversal you would ask 'How would I reduce customer satisfaction?'. After considering this question you might give the following answers:
Not answering the phone when customers call
Not returning phone calls
Have people with no product knowledge answering the phone
Use rude staff
Give the wrong advice
Etc.
After using Reversal, you would ensure that appropriate staff members were handling incoming phone calls efficiently and pleasantly. You would set up training programs to ensure that they were giving accurate and effective advice.

Key Points:
Reversal is a good, easy process for improving products and services. You use it by asking the exact opposite of the question you want answered, and then apply the results appropriately.
SCAMPER - A tool for generating new products and services

How to use tool:
SCAMPER is a checklist that helps you to think of changes you can make to an existing product to create a new one. You can use these changes either as direct suggestions or as starting points for lateral thinking.

The changes SCAMPER stands for are:
S - Substitute - components, materials, people
C - Combine - mix, combine with other assemblies or services, integrate
A - Adapt - alter, change function, use part of another element
M - Modify - increase or reduce in scale, change shape, modifyattributes (e.g. colour)
P - Put to another use
E - Eliminate - remove elements, simplify, reduce to core functionality
R - Reverse - turn inside out or upside down, also use of Reversal.

Example:
As an example, imagine that you are a manufacturer of nuts and bolts, and you were looking for new products. SCAMPER would give you:
Substitute - use of high tech materials for niche markets, such as high speed steel? Carbon fiber? Plastics? Glass? Non-reactive material?
Combine - integrate nut and bolt? Bolt and washer? Bolt and spanner?
Adapt - put Allen key or Star head on bolt? Countersink head?
Modify - produce bolts for watches or bridges? Produce different shaped bolts (e.g. screw in plugs)? Pre-painted green bolts?
Put to another use - bolts as hinge pins? As axles?
Eliminate - Eliminate nuts, washers, heads, thread, etc.
Reverse - make dies as well as bolts, make bolts that cut threads for themselves in material, etc.
Using SCAMPER here has helped you define possible new products. Many of the ideas may be impractical or may not suit the equipment used by the manufacturer. However some of these ideas could be good starting points for new products.

SCAMPER was created by Michael Mikalko in his book book ' Thinkertoys.
Key points:
SCAMPER is an acronym for Substitute, Combine, Adapt, Modify, Put to another use, Eliminate, Reverse. This is a list of changes that you could make to existing products and services to open up new opportunities

Attribute Listing, Morphological Analysis & Matrix Analysis
- Tools for creating new products & services

Attribute Listing, Morphological Analysis and Matrix Analysis are good techniques for finding new combinations of products or services. They are sufficiently similar to be discussed together. We use Attribute Listing and Morphological Analysis to generate new products and services.

Draw up a table using these attributes as column headings. Write down as many variations of the attribute as possible within these columns. This might be an exercise that benefits from Brainstorming. The table should now show all possible variations of each attribute.

Now select one entry from each column. Either do this randomly or select interesting combinations. By mixing one item from each column, you will create a new mixture of components. This is a new product, service or strategy.

Finally, evaluate and improve that mixture to see if you can imagine a profitable market for it.

Example:
Imagine that you want to create a new lamp. The starting point for this might be to carry out a morphological analysis. Properties of a lamp might be power supply, bulb type, light intensity, size, style, finish, material, shade, etc.

You can set these out as column headings on a table, and then brainstorm variations:

Power Supply
Bulb Type
Light Intensity
Size
Style
Finish
Material
Battery
Halogen
Low
Very Large
Modern
Black
Metal
Mains
Bulb
Medium
Large
Antique
White
Ceramic
Solar
Daylight
High
Medium
Roman
Metallic
Concrete
Generator
Colored
Variable
Small
Art Nouveau
Terracotta
Bone
Crank

Hand held
Industrial
Enamel
Glass
Gas

Ethnic
Natural
Wood
Oil/Petrol

Fabric
Stone
Flame

Plastic

Interesting combinations might be:
Solar powered/battery, medium intensity, daylight bulb - possibly used in clothes shops to allow customers to see the true color of clothes.
Large hand cranked arc lights - used in developing countries, or far from a mains power supply
A ceramic oil lamp in Roman style - used in themed restaurants, resurrecting the olive oil lamps of 2000 years ago
A normal table lamp designed to be painted, wallpapered or covered in fabric so that it matches the style of a room perfectly
Some of these might be practical, novel ideas for the lighting manufacturer. Some might not. This is where the manufacturer's experience and market knowledge are important.
Key points:
Morphological Analysis, Matrix Analysis and Attribute Listing are useful techniques for making new combinations of products, services and strategies.

You use the tools by identifying the attributes of the product, service or strategy you are examining. Attributes might be components, assemblies, dimensions, color, weight, style, speed of service, skills available, etc.

Use these attributes as column headings. Underneath the column headings list as many variations of that attribute as you can.

You can now use the table by randomly selecting one item from each column, or by selecting interesting combinations of items. This will give you ideas that you can examine for practicality.
Notes:
Attribute Listing focuses on the attributes of an object, seeing how each attribute could be improved.
Morphological Analysis uses the same basic technique, but is used to create a new product by mixing components in a new way.
Matrix Analysis focuses on businesses. It is used to generate new approaches, using attributes such as market sectors, customer needs, products, promotional methods, etc.

Brainstorming - Generating many radical ideas

How to use tool:
Brainstorming is an excellent way of developing many creative solutions to a problem. It works by focusing on a problem, and then coming up with very many radical solutions to it. Ideas should deliberately be as broad and odd as possible, and should be developed as fast as possible. Brainstorming is a lateral thinking process (see the introduction to this chapter for further information). It is designed to help you break out of your thinking patterns into new ways of looking at things.

During brainstorming sessions there should be no criticism of ideas. You are trying to open possibilities and break down wrong assumptions about the limits of the problem. Judgments and analysis at this stage will stunt idea generation.

Ideas should only be evaluated once the brainstorming session has finished - you can then explore solutions further using conventional approaches.

If your ideas begin to dry up, you can 'seed' the session with, for example, a random word (see Random Input).

Individual BrainstormingWhen you brainstorm on your own you will tend to produce a wider range of ideas than with group brainstorming - you do not have to worry about other people's egos or opinions, and can therefore be more freely creative. You may not, however, develop ideas as effectively as you do not have the experience of a group to help you.

When Brainstorming on your own, it can be helpful to use Concept Maps to arrange and develop ideas.

Group Brainstorming Group brainstorming can be very effective as it uses the experience and creativity of all members of the group. When individual members reach their limit on an idea, another member's creativity and experience can take the idea to the next stage. Therefore, group brainstorming tends to develop ideas in more depth than individual brainstorming.

Brainstorming in a group can be risky for individuals. Valuable but strange suggestions may appear stupid at first sight. Because of such, you need to chair sessions tightly so that uncreative people do not crush these ideas and leave group members feeling humiliated.

To run a group brainstorming session effectively, do the following:
Define the problem you want solved clearly, and lay out any criteria to be met.
Keep the session focused on the problem
Ensure that no one criticizes or evaluates ideas during the session. Criticism introduces an element of risk for group members when putting forward an idea. This stifles creativity and cripples the free running nature of a good brainstorming session.
Encourage an enthusiastic, uncritical attitude among members of the group. Try to get everyone to contribute and develop ideas, including the quietest members of the group
Let people have fun brainstorming. Encourage them to come up with as many ideas as possible, from solidly practical ones to wildly impractical ones. Welcome creativity.
Ensure that no train of thought is followed for too long
Encourage people to develop other people's ideas, or to use other ideas to create new ones
Appoint one person to note down ideas that come out of the session. A good way of doing this is to use a flip chart. This should be studied and evaluated after the session.

Where possible, participants in the brainstorming process should come from as wide a range of disciplines as possible. This brings a broad range of experience to the session and helps to make it more creative.
Key points:
Brainstorming is a way of generating radical ideas. During the brainstorming process there is no criticism of ideas, as free rein is given to people's creativity. Criticism and judgment cramp creativity.
The Reframing Matrix - Looking at problems with a different perspective

How to use tool:
A Reframing Matrix is a simple technique that helps you to look at business problems from a number of different viewpoints. It expands the range of creative solutions that you can generate.

The approach relies on the fact that different people with different experience approach problems in different ways. What this technique helps you to do is to put yourself into the minds of different people and imagine the solutions they would come up with.

We do this by putting the question to be asked in the middle of a grid. We use boxes around the grid for the different perspectives. This is just an easy way of laying the problem out, so if it does not suit you, change it.

We will look at two different approaches to the reframing matrix - you could, however, use this approach in many different ways.

The 4 Ps ApproachThis relies on looking at a problem from different perspectives within a business. The 4 Ps approach looks at problems from the following viewpoints:
Product perspective: Is there something wrong with the product?
Planning perspective: Are our business plans or marketing plans at fault?
Potential perspective: If we were to seriously increase our targets, how would we achieve these increases?
People perspective: Why do people choose one product over another?
An example of this approach is shown below:
The 'Professions Approach'Another approach to using a reframing matrix is to look at the problem from the viewpoints of different specialists. The way, for example, that a doctor looks at a problem would be different from the approach a civil engineer would use. This would be different from a sales manager's perspective.

The idea of the Reframing Matrix was devised by Michael Morgan in his book ‘ Creating Workforce Innovation ’.
Key points:
The Reframing Matrix is a formal technique used to look at problems from different perspectives. It helps to expand the number of options open to you for solving a problem.

You draw up a reframing matrix by posing a question in a box in the middle of a piece of paper. You then draw a grid around it. Each cell will contain approaches to the problem, seen from one perspective.

One way of using the technique is the '4 Ps' approach. This looks at the problem from the following viewpoints: Product, Planning, Potential and People. Another set of perspectives is to ask your self how different professionals would approach the problem. Useful professions to consider would be medical doctors, engineers, systems analysts, sales managers, etc.
Concept Fan - Widening the Search for Solutions

How to use tool:
The Concept Fan is a way of finding different approaches to a problem when you have rejected all obvious solutions. It develops the principle of 'taking one step back' to get a broader perspective.

To start a Concept Fan, draw a circle in the middle of a large piece of paper. Write the problem you are trying to solve into it. To the right of it radiate lines representing possible solutions to the problem.
It may be that the ideas you have are impractical or do not really solve the problem. If this is the case, take a 'step back' for a broader view of the problem.

Do this by drawing a circle to the left of the first circle, and write the broader definition into this new circle. Link it with an arrow to show that it comes from the first circle:

Use this as a starting point to radiate out other ideas:

If this does not give you enough new ideas, you can take yet another step back (and another, and another…):
The idea of the Concept Fan was devised by Edward de Bono in his book 'Serious Creativity' - this is one of the books reviewed on right-hand side of this page. The book shows how to use many similar tools.

Key points:
The Concept Fan is a useful technique for widening the search for solutions when you have rejected all obvious approaches. It gives you a clear framework within which you can take 'one step back' to get a broader view of a problem.

To start a concept fan, write the problem in the middle of a piece of paper. Write possible solutions to this problem on lines radiating from this circle.

If no idea is good enough, redefine the problem more broadly. Write this broader definition in a circle to the left of the first one. Draw an arrow from the initial problem definition to the new one to show the linkage between the problems. Then radiate possible solutions from this broader definition.

Keep on expanding and redefining the problem until you have a useful solution.

Random Input - Making Creative Leaps

Random Input is a lateral thinking tool. It is very useful when you need fresh ideas or new perspectives during problem solving.

As explained in the introduction to this chapter, we tend to think by recognizing patterns. We react to these patterns based on past experience and extensions to that experience. Sometimes, though, we get stuck inside them. Within a particular pattern there may be no good solution to a particular sort of problem.

Random input is a technique for linking another thinking pattern into the one we are using. Along with this new pattern comes all the experience you have connected to it.
How to use tool:
To use Random Input, select a random noun from either a dictionary or a pre-prepared word list. It often helps if the noun is something that can be seen or touched (e.g. 'helicopter', 'dog') rather than a concept (e.g. 'fairness'). Use this noun as the starting point for brainstorming your problem.

You may find that you get good insights if you select a word from a separate field in which you have some expertise.

If you choose a good word, you will add a range of new ideas and concepts to your brainstorming. While some will be useless, hopefully you will gain some good new insights into your problem. If you persist, then at least one of these is likely to be a startling creative leap.

Example:
Imagine that you are thinking about the problem of reducing car pollution. So far in thinking through the problem you have considered all the conventional solutions of catalytic conversion and clean fuels.

Selecting a random noun from the titles of the books in a bookcase you might see the word 'Plants'. Brainstorming from this you could generate a number of new ideas:
Plant trees on the side of roads to convert CO2 back into oxygen
Similarly, pass exhaust gases through a soup of algae to convert CO2 back into oxygen. Perhaps this is how an 'air scrubber' in a space craft works?
Put sulfur-metabolizing bacteria into an exhaust gas processor to clean up exhaust gases. Would nitrogen compounds fertilize these bacteria?
Another meaning of 'Plant' is factory. Perhaps exhaust gases could be collected in a container, and sent to a special plant to be cleaned? Perhaps you could offload these gases at the same time as you fill up with fuel?
These ideas are very raw. Some may be wrong or impractical. One of them might be original and the basis of some useful development.

Key points:
Random input is an excellent way of getting new perspectives on a problem. It often leads to startling creative leaps.

It provides an easy way of breaking out of restrictive thinking patterns. It helps you to link in whole ranges of new solutions that you would not otherwise associate with the problem.

The best words to use are concrete nouns, which may come from areas in which you have some expertise. Nouns should not, however, come from the same field as the problem you are considering, as the whole idea of Random Input is to link in new thinking patterns, not to stay inside old ones.
Provocation -Carrying Out Thought Experiments

How to use tool:
Provocation is an important lateral thinking technique. Just like Random Input, it works by moving your thinking out of the established patterns that you use to solve problems.

As explained earlier, we think by recognizing patterns and reacting to them. These reactions come from our past experiences and logical extensions to those experiences. Often we do not think outside these patterns. While we may know the answer as part of a different type of problem, the structure of our brains makes it difficult for us to link this in.

Provocation is one of the tools we use to make links between these patterns.

We use it by making deliberately stupid statements (Provocations), in which something we take for granted about the situation is not true. Statements need to be stupid to shock our minds out of existing ways of thinking. Once we have made a provocative statement, we then suspend judgment and use that statement to generate ideas. Provocations give us original starting points for creative thinking.

As an example, we could make a statement that 'Houses should not have roofs'. Normally this would not be a good idea! However this leads one to think of houses with opening roofs, or houses with glass roofs. These would allow you to lie in bed and look up at the stars.

Once you have made the Provocation, you can use it in a number of different ways, by examining:
The consequences of the statement
What the benefits would be
What special circumstances would make it a sensible solution
The principles needed to support it and make it work
How it would work moment-to-moment
What would happen if a sequence of events was changed
Etc.
You can use this list as a checklist.

Edward de Bono has developed and popularize use of Provocation by using the word 'Po'. 'Po' stands for 'Provocative operation'. As well as laying out how to use Provocation effectively, he suggests that when we make a Provocative statement in public the we label it as such with 'Po' (e.g. 'Po: the earth is flat'). This does rely on all members of your audience knowing about Provocation!

Edward de Bono's books explore this sort of technique in detail - we review one of them, Serious Creativity, on our right hand sidebar.

As with other lateral thinking techniques, Provocation does not always produce good or relevant ideas. Often, though, it does. Ideas generated using Provocation are likely to be fresh and original.

Example:
The owner of a video-hire shop is looking at new ideas for business to compete with the Internet. She starts with the provocation 'Customers should not pay to borrow videos'.

She then examines the provocation:
Consequences: The shop would get no rental revenue and therefore would need alternative sources of cash. It would be cheaper to borrow the video from the shop than to download the film or order it from a catalogue.
Benefits: Many more people would come to borrow videos. More people would pass through the shop. The shop would spoil the market for other video shops in the area.
Circumstances: The shop would need other revenue. Perhaps the owner could sell advertising in the shop, or sell popcorn, sweets, bottles of wine or pizzas to people borrowing films. This would make her shop a one-stop 'Night at home' shop. Perhaps it would only lend videos to people who had absorbed a 30-second commercial, or completed a market research questionnaire.
After using the Provocation, the owner of the video shop decides to run an experiment for several months. She will allow customers to borrow the top ten videos free (but naturally will fine them for late returns). She puts the videos at the back of the shop. In front of them she places displays of bottles of wine, soft drinks, popcorn and sweets so that customers have to walk past them to get to the videos. Next to the film return counter she sells merchandise from the top ten films being hired.

If the approach is a success she will open a pizza stand inside the shop.
Key points:
Provocation is an important lateral thinking technique that helps to generate original starting points for creative thinking.

To use provocation, make a deliberately stupid comment relating to the problem you are thinking about. Then suspend judgment, and use the statement as the starting point for generating ideas.

DO IT - A Simple Process for Creativity

How to use tool:
DO IT is a process for creativity.

Techniques outlined earlier in this chapter focus on specific aspects of creative thinking. DO IT bundles them together, and introduces formal methods of problem definition and evaluation. These help you to get the best out of the creativity techniques.

DO IT is an acronym that stands for:
D - Define problem
O - Open mind and apply creative techniques
I - Identify best solution
T - Transform

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These stages are explained in more detail below:

1. Define ProblemThis section concentrates on analyzing the problem to ensure that the correct question is being asked. The following steps will help you to do this:
Check that you are tackling the problem, not the symptoms of the problem. To do this, ask yourself why the problem exists repeatedly until you get to the root of it.
Lay out the bounds of the problem. Work out the objectives that you must achieve and the constraints that you are operating under.
Where a problem appears to be very large, break it down into smaller parts. Keep on going until each part is achievable in its own right, or needs a precisely defined area of research to be carried out. See Drill-Down for a detailed description of this process.
Summarize the problem in as concise a form as possible. Robert W. Olsen suggests that the best way to do this is to write down a number of 2 word problem statements and choose the best one.
2. Open Mind and Apply Creative TechniquesOnce you know the problem that you want to solve, you are ready to start generating possible solutions. It is very tempting just to accept the first good idea that you come across. If you do this, you will miss many even better solutions.

At this stage of DO IT we are not interested in evaluating ideas. Instead, we are trying to generate as many different ideas as possible. Even bad ideas may be the seeds of good ones.

You can use the whole battery of creativity techniques covered earlier in this section to search for possible solutions. Each tool has its particular strengths and benefits, depending on the problems that you want to solve. While you are generating solutions, remember that other people will have different perspectives on the problem, and it will almost certainly be worth asking for the opinions of your colleagues as part of this process.

3. Identify the Best SolutionOnly at this stage do you select the best of the ideas you have generated. It may be that the best idea is obvious. Alternatively, it may be worth examining and developing a number of ideas in detail before you select one.

The Decision Making Techniques section of Mind Tools explains a range of excellent decision making techniques. Decision Tree Analysis and Force Field Analysis are particularly useful. These will help you to choose between the solutions available to you.

When you are selecting a solution, keep in mind your own or your organization's goals. Often Decision Making becomes easy once you know these.

4. TransformHaving identified the problem and created a solution to it, the final stage is to implement this solution. This involves not only development of a reliable product from your idea, but all the marketing and business side as well. This may take a great deal of time and energy.

Many very creative people fail at this stage. They will have fun creating new products and services that may be years ahead of what is available on the market. They will then fail to develop them, and watch someone else make a fortune out of the idea several years later.

The first stage in transforming an idea is to develop an Action Plan for the transformation. This may lead to creation of a Business or Marketing Plan. Once you have done this, the work of implementation begins!

DO IT was devised by Robert W Olsen in his book ‘The Art of Creative Thinking’.
Key points:
DO IT is a structured process for creativity. Using DO IT ensures that you carry out the essential groundwork that helps you to get the most out of creativity tools.

These steps are:
Problem Definition: During this stage you apply a number of techniques to ensure that you are asking the right question.
Open Mind: Here you apply creativity techniques to generate as many answers as possible to the question you are asking. At this stage you are not evaluating the answers.
Identify the best solution: Only at this stage do you select the best solutions from the ones you came up with in step 2. Where you are having difficulty in selecting ideas, use formal techniques to help.
Transform: The final stage is to make an Action Plan for the implementation of the solution, and to carry it out. Without implementation, your creativity is sterile.

Simplex - A Powerful Integrated Problem-Solving Process

How to use tool:
Simplex is an industrial-strength creativity tool. It takes the approach of DO IT to the next level of sophistication.

Rather than seeing creativity as a single straight-line process, Simplex sees it as the continuous cycle it should be. Completion and implementation of one cycle of creativity leads straight into the next cycle of creative improvement.

Simplex uses the following eight stages:

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These are explained below:

1. Problem findingOften finding the right problem to solve is the most difficult part of the creative process. When using Simplex, actively seek problems out. Wherever they exist you have opportunities for change and improvement.

Problems may be obvious, or can be flushed out using trigger questions like the ones below:
What would your customers want you to improve?
What could they be doing better if we could help them?
Who else could we help using our core competences?
What small problems do we have which could grow into bigger ones?
What slows our work or makes it more difficult? What do we often fail to achieve?
How can we improve quality?
What are our competitors doing that we could do?
What is frustrating and irritating?
These questions deal with problems that exist now. It is also useful to try to look into the future. Think about how you expect markets and customers to change over the next few years; the problems you may experience as your organization expands; and social, political and legal changes that may affect it.

At this stage you may not have enough information to formulate your problem precisely. Do not worry about this until step 3!

2. Fact FindingThe next stage is to find out as much information relating to the problem as possible.

This gives you the depth of knowledge you need to:
Use the best ideas your competitors have had
Understand customers needs in more detail
Know what has already been tried
Fully understand any processes, components, services or technologies that you may need to use
Ensure that the benefits of solving the problem will be worth the effort you will put into it
This stage also involves assessing the quality of the information that you have. Here it is worth listing your assumptions and checking that they are correct.

3. Problem definitionBy the time you reach this stage, you should know roughly what the problem is and should have a good understanding of the facts relating to it. From here the thing to do is to crystallize the exact problem or problems you want to solve.

It is important to solve a problem at the right level. If you ask questions that are too broad, then you will never have enough resources to answer them effectively. If you ask questions that are too narrow, you may end up fixing symptoms of a problem, rather than the problem itself.

Min Basadur (who created the Simplex Process) suggests using the question 'Why?' to broaden a question, and 'What's stopping you?' to narrow it.

For example, if your problem is one of trees dying, ask 'Why do I want to keep trees healthy?'. This might broaden the question to 'How can I maintain the quality of our environment?'.

A 'What's stopping you?' here could be 'I do not know how to control a disease killing the tree'.

Big problems are normally made up of many smaller ones. This is the stage at which you can use a technique like Drill-Down to break the problem down to its component parts.

4. Idea findingThe next stage is to generate as many ideas as possible. Ways of doing this range from asking other people for their opinions, through programmed creativity tools and lateral thinking techniques to brainstorming.

Do not evaluate ideas during this stage. Instead, concentrate on generating many ideas as possible. Bad ideas often trigger good ones.

5. Selection & EvaluationOnce you have a number of possible solutions to your problem, it is time to select the best one.

The best solution may be obvious. If it is not, then it is important to think through the criteria you will use to select the best idea. The Decision Making Techniques section of Mind Tools lays out a number of good methods for this. Particularly useful techniques may be Decision Trees, Paired Comparison Analysis and Grid Analysis.

Once you have selected an idea, develop it as far as possible. It is then essential to evaluate it to see if it is good enough to be considered worth using. It is important not to let your ego get in the way of your common sense. If your idea does not give big enough benefit, then either see if you can generate more ideas, or restart the whole process. You can waste years of your life developing creative ideas that no-one wants.

There are two excellent techniques for doing this. One is Edward de Bono's 6 Thinking Hats, which is an excellent tool for qualitative analysis. The other is Cost/Benefit Analysis, which gives you a good basis for financially based decisions.

6. PlanningOnce you have selected an idea, and are confident that your idea is worthwhile, then it is time to plan its implementation.

The best way of doing this is to set this out as an Action Plan, which lays out the who, what, when, where, why and how of making it work. For large projects it may be worth using more formal planning techniques.

7. Sell IdeaUp to this stage you may have done all this work on your own or with a small committee. Now you will have to sell the idea to the people who must support it. This might be your boss, a bank manager or other people involved with the project.

In selling the project you will have to address not only the practicality of the project, but also things such internal politics, hidden fear of change, etc.

8. ActionFinally, after all the creativity and preparation, comes action! This is where all the careful work and planning pays off.

Once the action is firmly under way, return to stage 1, Problem Finding, to continue improving your idea.

Min Basadur's book, The Power of Innovation, explores this process in much more detail - the book is reviewed on the right hand side bar.
Key points:
The Simplex Process is a powerful, sophisticated approach to innovation. It is suitable for projects and organizations of almost any scale.

The Process is an eight-stage cycle. Upon completion of the eight stages you start it again to find and solve another problem. This helps to ensure continuous improvement.

Stages in the process are:
Problem finding
Fact finding
Problem Definition
Idea Finding
Selection and Evaluation
Planning
Selling of the Idea
Action
By moving through these stages you ensure that you solve the most significant problems with the best solutions available to you. This process can help you to be intensely creative.

2006-01-05T18:54:00.000-08:00

Pushpendra
How a Liquid Propellant Rocket Works
Liquid fueled rockets were first theorized by Tsiolkozsi in "Investigation of Interplanetary Space by Means of Reactive Devices, " published in 1896. His idea was realized 27 years later when Robert H.Goddard launched the first liquid fueled rocket. The complexity of the liquid rocket engine has helped to create the cliché of the "rocket scientist" and there is no doubt the builders of the liquid fueled rocket engine were highly intelligent. But the liquid rocket, as we know it today, is the sum of a century of rocket scientists' contributions to the constantly developing field. Liquid fueled rockets propelled the Russians and Americans deep into the space age with the mighty Energiya SL-17 and Saturn V rockets. The high thrust capacities of these rockets, having given man passage into the heavens, epoch the development of the rocket. More advanced propulsion systems have been developed, but it will many years before the dominance of the liquid fueled rocket will wane. The "giant step... mankind" took on July 21, 1969, as Armstrong stepped onto the moon, was a step granted by the 8 million pounds of thrust garnered by the stepping stone of the Saturn V rocket.
Function: As with conventional solid fuels rockets, liquid fueled rockets burn a fuel and an oxidizer. The apparent distinction is the liquid state of the fuel and the oxidizer. Several layers of complexity are added to this rather innocent looking point. The unfolding performed here will illuminate the necessity for this complexity.
There are two metal tanks holding the fuel and oxidizer respectively. Due to properties of these two liquids, they are typically loaded into their tanks just prior to launch. The separate tanks are necessary, for many liquid fuels burn upon contact. Upon a set launching sequence two valves open, allowing the liquid, hitherto blocked, to flow down the pipe-work. If these valves simply opened allowing the liquid propellants to flow into the combustion chamber at their own leisure, a weak (if any at all) thrust production would incur as well as an unstable flow rate (leading to a unstable thrust rate). Two solutions have been devised to solve this problem: (1) a pressurized gas feed and (2) a turbopump feed.
The simpler of the two, the pressurized gas feed, adds a tank of high pressure gas to the propulsion system. The gas, an unreactive, inert, and light gas (such as helium), is held and regulated, under intense pressure, by a valve/regulator. The purpose of this gas is maintain a pressure forced flow of the liquid propellants, pushing them out, as one might expend liquids from a straw by blowing into it. As noted, more than a valve is needed to execute this operation in a rocket, thus the regulator controls the amount of gas flowing into each propellant tank. If the gas was controlled only by a valve, opened during the initial launch sequence, the gas would flow to form an equilibrium of pressures in the gas tank, the piping, and the propellant tanks. This is problem. Although the gas tank will be able to withstand the equilibrium pressure, the piping and the propellant tanks might not and the rupture ensuing will cause a conflagration of failure. One could use propellant tank able to bear such pressures but the mass of these tanks would be exorbitant. Thus, the regulator controls a flow that maintains a constant pressure within the propellant tanks--a situation solving the problem of fuel transfer. The constant force (pressure) exerted on the surface of the propellants will give a constantly regulated flow as they are pushed into the combustion chamber. The regulator functions to maintain these constant flows by adjusting the flow of the gas entering the propellant tanks. The gas flow must constantly be regulated; as pressure is fed into the propellant tanks, to compensate for the fuel leaving, pressure is removed from the gas storage tank. And this gas is progressively being sent into the propellant tanks, as more of this low-pressure gas is necessary to maintain a constant pressure within the propellant tanks. The pressure of a gas is indirectly related to the volume the gas occupies. This law explains how the pressure decreases in the gas supply tank (whose volume does not change), and how this action can maintain a constant pressure inside the propellant tanks (whose volumes increase, as the liquid propellants exit, with the influx the gas in effect replacing the fuel). Given this criteria the flow of propellants is ultimately controlled by the pressure the system is set to maintain. Thus, a high rate of propellant flow is achieved by simply increasing the set pressure of the system.
The second, and often preferred, solution to the fuel transfer problem is a turbopump. A turbopump is the same as regular pump in function and bypasses a gas-pressurized system by sucking out the propellants and accelerating them into the combustion chamber. The idea seems simple but the implementation of it not. The gas-pressurized method worked because great pressures could be easily stored in the gas storage tank, but in the turbopump model the pump has to do all the work. And energy to run the turbopump must generated. The large propellant tanks looming over the turbopump suggest a source of stored energy. To convert this chemically stored energy to productive pump energy a miniature rocket engine is added (yes, one is not enough). This small engine typically uses the same propellants as the main rocket but at a much lower thrust production due to decreased size. The exhaust (or thrust) of this engine beats down upon a turbine (a propeller-like disk with hundreds of blades), causing it to spin rapidly. This action converts the chemical energy into the mechanical energy the turbopump needs to operate. A shaft, connected to the rotating turbine, spreads in opposite directions to two additional turbines. The rotation of these turbines, controlled by a gear train (a set of gears) along the shaft, controls the flow of the propellants the spinning of the turbines induces. This configuration is analogous to a high power waterwheel accelerating the water in a stream, where the stream in the turbopump model is the piping that leads to the combustion chamber. Note that the three turbines in this model are enclosed and entirely isolated from one another connected only by the shaft. Also note that the blades on the on the outer two turbines (the propellant accelerating turbines) are both powered, via the same shaft, by the interior, rocket powered turbine.
Now that the propellants are being gushed into the combustion chamber we run into more complications. As the oxidizer and fuel are mixed and ignited inside the combustion chamber thrust is created. Ultimately this thrust will push the rocket upwards but while inside the thrust wants to push everywhere, even into the piping the propellant is coming out of. The intense pressure created in this converging section of the propulsion system must be accounted for in determining rate of propellant flow and combustion chamber shear strength. If the rate of propellant flow is to small the propellant will not be bale to enter the combustion chamber--a problem avoided by the proper use of a gas-pressurized or turbopump system. If the combustion chambers integrity cannot maintain burn-time pressures the engine will explode, thus high-strength (although heavy) steel or an alloyed metal (composed of several metals; lighter) or composite material is used. Another problem is the intense heat created by combustion of the fuel and oxidizer. This is usually solved by circulating the propellants around the exterior of the combustion chamber and nozzle. The propellants are (as will be seen in the following paragraph) extremely cold and they evaporate slightly, as the flow over the hot surface of the combustion chamber, absorbing some of the engine's heat. This evaporation actually has three effects: (1) as mentioned, evaporative cooling, (2) increase in propellant flow (from increase in total pressure of increased volume evaporated gas), and (3) catalytic (although temperature of the relatively adiabatic system might increase, the creation of more gaseous reactants (which burn more efficiently) will probably improve overall performance).
Liquid Oxygen is the most common oxidizer used. Other oxidizers used in liquid propellant rockets includeing: hydrogen peroxide (95%, H2O2), nitric acid (HNO3), and liquid fluorine. Of these choices liquid fluorine, given a control fuel, produces the highest specific impulse (amount of thrust per unit propellant). But due to difficulties in handling this corrosive element, and due to the high temperatures it burns at, liquid fluorine is rarely used in modern liquid fueled rockets. At STP (standard temperature, 25 degrees Celsius, and pressure, 1 ATM or 760 torr) oxygen and fluorine are gaseous elements. This state could be used, and combustion would occur, but the amount of gaseous oxygen or fluorine, storable in the oxidizer tank, would be insufficient in producing useful thrust. Thus, the temperatures of these gases are significantly reduced, thereby changing into a liquid state. And it is in this form that the oxidizers must be used. The reason for this is simply that the atoms of oxygen or fluorine are much closer to one another in the liquid state-the oxidizer is more concentrated and thus more useful. The liquid fuels often used include: liquid hydrogen, liquid ammonia (NH3), hydrazine (N2H4), and kerosene (hydrocarbon).
Advantages/Disadvantages: Liquid propellant rockets are the most powerful (in terms gross thrust) propulsion systems available. They are also among the most variable, that is to say, adjustable given a large array of valves and regulators to control and augment rocket performance. Unfortunately the last point makes liquid propellant rockets intricate and complex. Not that this scares away the designers (they are "rocket scientists") but what it does do is lower reliability. A real modern liquid bipropellant engine has thousands of piping connections carrying various cooling, fueling, or lubricating fluids. Also the various sub-parts such as the turbopump or regulator consist of a separate vertigo of pipes, wires, control valves, temperature gauges and support struts. Given this myriad of parts, the chance of one integral function failing is large. Thus, many rockets are rated in terms of reliability--one of the reasons for the Titan series' popularity. As noted before the liquid oxygen is the most commonly used oxidizer, but it too has its drawbacks. To achieve the liquid state of this element, a temperature of -183 degrees Celsius must be obtained--conditions under which oxygen readily evaporates, losing a large sum of oxidizer just while loading. Nitric acid, another powerful oxidizer, contains 76% oxygen, is in its liquid state at STP, and has a high specific gravity--all great advantages. The latter point is a measurement similar to density and as it rises higher so to does the propellant's performance. But, nitric acid is hazardous in handling (mixture with water produces a strong acid) and produces harmful by-products in combustion with a fuel, thus its use is limited.

2006-01-05T18:47:00.000-08:00

Composite Solid Propellant By Pushpendra Singh

Solid propellants of the composite type, containing separate fuel (or reducer, chemically) and oxidiser (in a separate compound) intimately mixed, replaced the simple double-base propellants to a considerable extent, especially for large non-military motors. The organic fuel material is initially in a liquid or semi-liquid form that can set to a solid (binder). Among the earliest substances used were asphalt and various synthetic rubbers. While generally not considered as composite, black powder was in fact the oldest composite propellant. Before 1940 black powder, in common use, was nearly synonymous with the words 'rocket motor' .
While working on the theory of rocket propulsion for his doctoral thesis in 1937, Frank Malina mentioned to Fritz Zwicky of Caltech some difficulties he was having in his study. Zwicky exploded with the opinion that Malina was wasting his time on an impossible subject. For, he said, Malina must realise

that a rocket could not operate in space as it required the atmosphere to push against to provide thrust! By 1940 he realised that he was mistaken.
At Guggenheim Aeronautical Laboratory, California Institute of Technology (GALCIT),in 1939, one of the first objectives was to develop a solid propellant rocket unit capable of delivering a constant thrust on the order of 1000 pounds for a period of 10 to 30 seconds. As far as is known, no black powder or smokeless powder rocket had ever been constructed to meet these specifications of thrust and duration. Experts consulted by Malina, John Parsons, and Forman were very dubious about the possibility of doing so.
Preliminary experiments made by Parson and Forman with pressed solid propellant charges restricted to burn cigarette-fashion appeared to support this view. It was generally believed that the combustion chamber pressure of a restricted burning solid rocket unit would continue to rise from the moment of ignition until any combustion chamber of reasonable weight would burst. In other words, it was thought that such combustion was inherently unstable.
The GALCIT group's mentor, Professor Theodore von Karman, in the spring of 1940, had to listen to both the opinions of the experts and to the explosions of Parson's rockets. One evening at home Von Karman wrote down four differential equations describing the operation of an ideal restricted burning motor, and asked Malina to solve them. It was found that, theoretically, a restricted burning unit would maintain a constant chamber pressure as long as the ratio of the area of the throat of the exhaust nozzle to the burning area of the propellant charge remained constant, that is, the process was stable. Experimental verification of the theory was soon obtained.
Although there have been centuries of experiments with black powder rocket, and several investigators used smokeless powder and Ballistite in rockets between about 1918 and 1939, none of these rockets had the thrust and duration required for the aircraft "super-performance" applications. Parsons and Forman in 1938 built and tested a smokeless powder constant-volume combustion motor similar to the one that had been used by Goddard. They concluded after these tests that the mechanical complications of constructing an engine using successive impulses to obtain thrust durations of over 10 seconds was impractical. Upon Parson's recommendation, they concentrated their efforts on the development of a motor provided with a restricted burning powder charge that would burn at one end only at constant pressure to provide a constant thrust.
Parsons started with the traditional sky rocket. This type of pyrotechnic device was propelled by a black powder charge pressed into a cardboard combustion chamber with a conical hole in its centre. The gases escaped through a rounded clay orifice. Its efficiency was very, very low, but it was reliable. The conical hole in the charge was believed to be the secret that kept the charge from burning down the sides of the container or to produce chamber pressures that would burst the container. The longest duration of thrust of this motor did not exceed about 1 second.
During 1939 and 1940, various mixtures based on black powder and mixtures of black powder with smokeless powder were tested in 1 in. and 3 in. diameter chambers. The charge for the 3 in. chamber was made up of 6 in. long pellets compressed at around 6,500 psi., and coated with various substances to form a solid or liquid seal between the charge and the walls of the chamber. The charge of the 1 in. chamber was pressed directly into the chamber in small increments at pressures between 7,700 and 12,000 psi. Most of the tests of these charges ended in an explosion.
Mechanical causes for failures, such as burning of the charge on the surface next to the wall because of leakage, transfer of heat down the walls sufficient to ignite the sides of the charge, and cracking of the charge under combustion pressure, were suspected. However, there were those who were convinced that the combustion process of a restricted burning charge in a rocket motor was basically unstable. Only after von Karman and Malina proved the process was stable in their analysis of the characteristics of the ideal solid propellant rocket motor in the spring of 1940 was a concentrated effort was made to study the mechanical causes of failure.
Hundred of tests were then made with different powder mixtures, using black powder as the basic ingredient, with various loading techniques and various motor designs. The dependence of chamber pressure on the ratio of chamber cross section area to nozzle throat area was determined for each specific powder mixture.
By the spring of 1941 the results were sufficiently encouraging to schedule flight tests of an aircraft equipped with solid propellant rockets specially designed for it. The propellant charge used in the Ercoupe motor was a type of amide black powder designated as GALCIT 27 (amide: organic compound containing carbon, hydrogen, oxygen, and nitrogen. Some examples: HCONH2, CH3CONH2, C6H13CONH2). The 2 lb. charge was pressed into the combustion chamber, which had a blotting paper liner, in 22 increments by a plunger with a conical nose shape at a pressure of 18 tons. The diameter of the charge was 1.75 in. and its length varied between 10 and 11 in. The motor was designed to deliver about 28 lb. thrust for about 12 seconds.
Eighteen rocket motors were delivered every other day for the first tests at March Field, California, about an hour's drive from the project. During the first phase of the flight tests one motor failed explosively in a static test and one while Ercoupe was in level flight. Thereafter, 152 motors were used in succession without explosive failure. The motors were prepared by Parsons, Forman, and Fred Miller.
On August 16, 1941, Boushey made the first take-off of the Ercoupe with six JATOs firing. The first American manned flight of an aircraft propelled by rocket thrust alone was made by Boushey on August 23, 1941. The propeller of the Ercoupe was removed and 12 JATO units installed, of which only 11 functioned. The Ercoupe was pulled by a truck to a speed of about 25 m.p.h. before the JATOs were ignited. The airplane left the ground and reached an altitude of about 20 ft. This flight was not originally scheduled but the group could not resist the opportunity to make the improvised demonstration of the future possibility of rocket propulsion.
Frank Malina noted that it was most fortunate that the flight tests were carried out close to the location of the project, which permitted the rocket motors to be fired within a few days from the time they were charged with propellant. Following the flight tests, it was found that after the motors were exposed to simulated storage and temperature conditions over several days they exploded in most cases. It was evident that either the blotting paper liner or the mechanical characteristics of the propellant were unsatisfactory.
But the Navy Department regarded the successful Ercoupe tests with much interest from the point of view of application of rockets for assisted take-off of aircraft from aircraft carriers. Upon the urging of Lt. C.F. Fischer of the Bureau of Aeronautics, who had witnessed the tests, a contract was placed by the Navy with the Project in early 1942 for the development of a 200 lb. thrust, 8 second unit. The unit was designated by the acronym JATO for Jet Assisted Take-Off (sometime RATO), and this designation is still used.
This Navy contract came in the midst of the explosive failure of the JATO unit developed for the Ercoupe tests. All efforts to improve the amide-black powder propellant and loading techniques of the motor developed for Ercoupe tests failed to meet specified storage conditions ranging from Alaska to Africa. Investigations of motors using Ballistite also proved negative, mainly because of its ambient temperature sensitivity (variation of its rate of burning and thrust with ambient temperature).
Thus, the spring of 1942 was one of desperation for those concerned with development of a reliable solid propellant JATO unit. They knew that theoretically it was possible to construct such an engine, but no one came forward with a promising idea until June, when Parsons, no doubt after communing with his poetic spirits, suggested trying a radical new propellant. It would consist of potassium perchlorate (KClO4- in place of potassium nitrate KNO3: saltpetre), as oxidiser, common asphalt as used on roads as a binder and fuel. These could be cast, after being mixed, into a combustion chamber.
A test of the propellant, designated GALCIT 53, was quickly made and the results were so promising that work on other propellant types was dropped for a long time. Parsons was assisted in the development of the asphalt base propellant by Mills and Fred Miller. After due study of the origin of the ideas for the new propellant, Parsons was recognised as its inventor and a patent was granted in his name.
At first, the Ordnance Department objected strongly to the use of potassium perchlorate as an oxidiser because it had proved unsafe in the past. Parsons realised that their objection was no longer valid, since way had been found to produce the material with a minimum purity of 99%. Impurities in the form of dangerous chlorates (KClO3) had been practically eliminated. Sodium and potassium chlorates were used with dinitrotoluen in explosives (know as cheddites in French), also with perchlorates and various hydrocarbons-vaseline-,castor oil, and nitro. Potassium chlorate was also used as oxidiser in matches with phosphorus sesquisulfide P4S3 or tetraphosphorus trisulfide as the active fuel.
The ruling of the Ordnance Department was thereafter changed, allowing the use of this kind of solid oxidiser. The Navy contract for 100 JATO units delivering 200 lb. thrust for 8 seconds was successfully completed, with GALCIT 53 as the propellant. Production of service-type units for the Navy began shortly thereafter at the Aerojet Engineering Corporation (organised at the end of 1941 and formally incorporated on March 19, 1942 with the GALCIT members Von Karman, Malina, Haley, Parsons, Forman, and Summerfield).
The project carried out extensive studies on asphalt-base propellants in the following years. A detailed report released in May 1944 on the propellant GALCIT 61-C by Mills give the following composition: 76% potassium perchlorate and 24% fuel. The fuel component was 70% Texaco No. 18 asphalt and 30% Union Oil Company Pure Penn SAE No. 10 lubricating oil. The fuel was liquefied at about 275°F, the pulverised potassium perchlorate added to it, and the mixture thoroughly stirred. The mixture was then poured into the combustion chamber, which had been previously lined with a material similar to the fuel component, and allowed to cool and become hard. This propellant, when burned at a chamber pressure of 2,000 psi., had a chamber temperature of 3,000-3,500°F, a specific impulse of 186, and an exhaust velocity of about 5,900 ft. per sec. Storage temperature limits were from -9 deg F to 120 deg F. GALCIT 61-C was developed in 1943 and used in service JATO units by the Navy until the end of World War II. The propellant is also used on the Private A and F research rockets.
IMPROVEMENTS
Solid propellants utilising potassium perchlorate as oxidiser produced dense clouds of white smoke (potassium chloride-KCl, like sodium chloride-NaCl, common salt), which the Navy did not like at all. Some months after GALCIT 53 was developed, Parsons informed the Project weekly research conference that he had eliminated the smoke problem by replacing potassium perchlorate with ammonium perchlorate (NH4ClO4). Navy rocket experts were immediately invited to visit the Project for a demonstration:
"When they arrived we posted ourselves some distance from the test pit, the red flag was run up, and Parsons gave the order for his latest creation to be fired. We beheld a big cloud of with smoke and Parsons with a look of surprise on his face. He sheepishly explained that the smoke must have been caused by the humidity, for the air had been very dry on the days they had made tests before".
Ammonium perchlorate does reduce the amount of smoke produced if the air is dry, but it produces undesirable chloride in the jet. In fact Cl and H in NH4ClO4 may combine to form HCl, hydrogen chloride or hydrochloric acid with water. But that is the base of modern composite propellants.
The project also studied the possible use of other fuels instead of asphalt, such as Napalm (sodium palmitate = NaPalm - first tried as a high temperature, high energy propellant), gelled hydrocarbons, gelled wax mixtures, and butyl rubber. A continuation of studies of the last material later led Charles Bartley, under the JPL-ORDCIT Project in 1945, to the discovery of the advantages of the castable elastomeric (polysulfide rubber) material called Thiokol. This discovery became the basis of solid propellant manufacture by the Thiokol Chemical Corporation. The Air Force Material Command terminated work by the Project on solid propellant motors on June 30, 1944. The Ordnance Department, however, continued the work for long range missile applications.
During the course of this research, engineers were provided with methods of motor component design when the following characteristics of the propellant to be used were known:
Sensitivity of the propellant to ambient temperature during combustion.
Combustion pressure limit below which the propellant burns in irregular manner.
Combustion pressure limit above which the propellant burns in an unpredictable manner.
Storage characteristics of the propellant charge from the point of view of minimum and maximum ambient temperatures allowed and possible decomposition of the propellant with prolonged storage.
Ignition temperature of the propellant.
Rate of burning of the propellant as function of the combustion pressure.
Performance characteristics of the propellant to produce rocket thrust.
The great progress made in the scientific design of solid propellant rocket motors in comparison with the empirical, traditional, method used in previous centuries can be appreciated by reference to the text "Jet Propulsion" prepared for the course at Caltech at the request of the Air Technical Service Command in 1943 and continued in the following years. The debate on the superiority of solid vs. liquid propellant rocket engines for boosters of space vehicles still rages today (but environmental considerations now favour liquid propellants).
Sponsorship of solid-propellant research was taken over by the ORDCIT Project from the Air Force Materiel Command on July 1, 1944. By this time, JPL had made the following fundamental contributions to the design and construction of long-duration solid-propellant engines:
Theory: Von Karman-Malina theory of constant-thrust long- duration engines (1940)
Propellant development:
Parsons' break-away from Ballistite with amide black powder (1940)
Parsons' introduction of perchlorates as an oxidiser (1942).
Parsons' introduction of asphalt as fuel-binder with perchlorates; the invention of a castable case- bonded composite propellant charge (1942).
Engine component design
Parsons' design of a restricted-burning (case- bounded) propellant charge with amine black powder (1940).
Malina-Mills design of a safety pressure relief valve (1942).
Mills' review of various types of burning surfaces of a charge and theoretical confirmation that the surface of a cigarette-type burning charge was stable (1943).
After the successful JATO development with the asphalt- perchlorate propellant in 1942, Mills sought a fuel-binder for the perchlorate superior to asphalt. In 1944, Charles Bartley joined Mills' group, and in 1945 introduced as a replacement for asphalt a castable elastomeric material, polysulfide rubber, produced by Thiokol Chemical Corporation. The polysulfide rubber, compared to asphalt, produced a propellant much better both as regards storage temperature limits and hardness at high atmospheric temperatures. The latter property was especially important in the design of high-thrust engines requiring a charge with an internal-burning surface rather than a cigarette-burning surface.
Since at this time only Aerojet in the USA was producing composite solid-propellant engines, that company's attention was drawn to the asphalt replacement, but it was already interested in a similar material made by the General Tire and Rubber Co. It was only at the urging of the Ordnance Department that the Thiokol Chemical Corp. entered the field of composite solid propellants with the new fuel-binder discovered at JPL.
After obtaining the experience with the composite solid- propellant missiles Private A and F, studies began at JPL in 1946 on larger missiles using, in particular, the polysulfide rubber-perchlorate type propellant. The results of these studies led eventually to the design of the tactical guided missile, Sergeant.
The laboratory followed closely development with other type of solid propellants, especially Ballistite, used in high-thrust short-duration engines suitable for boosters (Aerojet built some double-base boosters using this material).
Other special-purpose rocket vehicles supported research in solid propellants and high-acceleration, and high-speed dynamics. A small vehicle unofficially called "Thunderbird" demonstrated the polysulfide composite-propellant, internal-burning star-grain solid motor in 1947. With an acceleration of over 100 G, (a precursor of the Sprint missile) it led to the Wac-scale solid-propellant research vehicle called Sergeant in 1948.
This Sergeant sounding rocket, unrelated to the tactical missile of the same name, proved to be ahead of its time. It was inspired by calculations that indicated a solid-propellant rocket of the internal-burning-star design could deliver several times the payload of a liquid-propelled V-2 type of similar weight. The motor chamber walls were very thin because the propellant, burning from within, would help contain heat and pressure.
An autopilot design effort was begun, and static tests of the motor, weighing 1300 lbs and delivering about 6000 lbs thrust for more than 30 seconds, were conducted.
Difficulties with this solid rocket, manifested in the rupture of the thin-wall case, coincided with a change in the JPL mission and an acceleration and expansion of Corporal development. The Sergeant project was suspended. The electronic autopilot was adopted for the Corporal missile while the solid-propellant engineers took their problems back to the laboratory and test stand for more investigation. Further development was undertaken by the Thiokol Chemical Corporation. The ultimate heritage of this early "Sergeant" powerplant was the reliable solid rocket, used in large scale in the Sergeant and other military missiles, and in clustered miniatures to launch the first Explorer satellites.
The motor evolved from the Sergeant test vehicle of 1948-49 via the Hermes RV-A-10 flight tested in March 1953. A Hermes A-2 Thiokol motor was ground tested in December 1951. The Hermes A-2 program was ended in October 1952.
The Sergeant missile was not the only result of the Thiokol polysulfide motor. Another major development was the Nike-Hercules sustainer motor (or stage two), the Lacrosse motor, and later the Bomarc B motor. Many small missiles, sounding rocket motors, and the Mercury and Gemini retro-rockets used the same propellant.
However, the use of polysulfide by Thiokol probably caused their loss of the key Polaris contract. Aerojet won the contract with the use of a more energetic polyurethane propellant.
After that Thiokol began the use of polybutadiene for big motors and won the contract for the Minuteman first stage motor. That lead as well to the Nike-Zeus, Pershing, Castor motors, Surveyor retro (first of a series of upper stage motors) and finally to the Shuttle SRB's.
Meanwhile, Hercules began the use of double-base propellant as fuel in composite propellants, since double-based motors burned with excess of fuel. The use of a separate oxidiser also permitted the addition of energetic fuels such as aluminium powder.
The excess of fuel in pure double-base caused a long afterburning flame, essentially of burning carbon (see launch-photographs of Nike Ajax and Hercules, Honest John, Terrier, and Talos). The unburned carbon cause also the dark exhaust before the afterburning.
The Hercules' Minuteman third stage was a follow-on of the Vanguard third stage.
Some composite propellants continue to use saltpetre (potassium nitrate) or ammonium nitrate.
Some composite propellant formulations and characteristics:
Molded composite: potassium nitrate(20-50%), elastomer(10%), ammonium picrate-NH4C6H2NO7-(70-40%). Specific impulse s.l.: 160 to 200 sec. Abundant smoke. Hard to brittle.
Castable composite: ammonium nitrate(80%), elastomer (18%), catalyst(2%). Specific impulse s.l.: 185 to 198 sec. Little smoke. Soft and resilient to hard and tough.
Castable composite: ammonium perchlorate(50-85%), elastomer(50-15%). Specific impulse s.l.: 175 to 240 sec. Much smoke at low oxidiser; little at high oxidiser; mist at relative humidity greater than 80%. Soft and resilient to hard and tough.
Castable composite: potassium perchlorate(50-80%), elastomer(50-20%). Specific impulse s.l.: 165 to 210 sec. Abundant smoke. Soft and resilient to hard and tough.
OXIDISERS
Ammonium perchlorate is the most widely used today. It is characterised by high heat, is a good gas producer (not a smoke producer), percent of oxygen by weigh: 34 percent, specific gravity: 1.9.
Potassium perchlorate is used for fast burning rates. It is characterised by high heat, is a low gas producer, percent of oxygen by weight: 46 percent, specific gravity: 2.5.
Ammonium nitrate is used for slower burning rates. It is characterised by low heat, is a high gas producer, and is good for gas generator propellants. It requires a greater amount of binder (fuel) to make castable, but too much binder produces excessive smoke. Ammonium nitrate's percent of oxygen by weight: 20 percent, specific gravity: 1.9. It may be the oxidiser for the future. It contains no toxic elements and no solid elements, produces no solids by decomposition, and therefore, together with a high energy non-polluting fuel, could provide a more 'environmentally friendly' solid propellant.
Lithium perchlorate, a proposed oxidiser, is very hygroscopic and may be used in some high-temperature propellants. Percent of oxygen by weight: 60 percent, specific gravity:2.4.
BINDER SYSTEMS
Introduction
The original composite propellants, used in JATO units, contained an asphalt binder. Since asphalt-perchlorate composites had poor performance and formulation characteristics, extensive research and development work was directed toward their improvement. This soon led to the discovery and acceptance of new and better chemical binder-fuels, primarily synthetic rubbers Initially, polysulfide liquid polymers were developed with only physical properties that were an improvement over those of asphalt. Later, with certain chemical-structure modifications, the overall performance of polysulfide soon outshone that of asphalt. Polysulphides, however, had a major drawback in that they released water during combustion; which interfered with efficient burning. The water by-product also limited the type of additives that could be mixed with the propellant, since water was highly reactive with materials such as aluminium. In the search for binder-fuels without the drawbacks of asphalt and polysulfides, polyurethanes (synthetic thermosetting or thermoplastic polymers) were found to have good performance and physical properties. With these aluminium could be incorporated for higher specific impulse. However, polyurethanes were so viscous that the amount of oxidisers and other solid additives that could be incorporated was limited. Eventually polybutadiene- based propellants were developed that had physical properties superior to those of polyurethanes.
Polysulfide
Polysulfide was the first binder elastomer fuel. For rocket applications a low-molecular-weight polymer was made from dichlorodiethyl formal; sodium polysulfide was used as the liquid binder. When the mixture was heated with an appropriate curing agent such as zinc oxide, the links between adjacent polymer chains were joined together to form the rubber network. The resulting binder had a glass-transition temperature near -60°F., making it usable to about -40°F. This was a distinct advantage over the first composites.
An undesirable quality of the polysulfides was the presence of sulphur atoms in the system. They produced high-molecular-weight exhaust products (sulphur dioxide with a molecular weight of 64) thereby lowering specific impulse. Since a large amount of oxidiser had to be mixed with the binder to obtain the high energy desired, the binder lost much of its rubber-like quality.
There were many organic and inorganic materials that acted as oxidisers and could be used to cure liquid polysulfide polymers. Each had its advantages and disadvantages.
Thiokol developed many varieties of polysulfides with improved qualities.
Polyurethane
Polyurethanes were the second elastomer fuel binder. The group of polymers known as polyurethanes were made by combining polyols with isocianates. The versatility in polymer chemistry was such that a large number of starting materials having varying molecular weights were available.
Compared with the polysulfides, the average molecular weight of the polyurethanes' exhaust gases was lower. This was because the polyurethanes contained only carbon, hydrogen, oxygen, and nitrogen atoms (not sulphur). An additional benefit was claimed in the processing: the backbone polymer contained substantial amounts of oxygen. It was not necessary therefore to use as great a percentage of oxidiser in the formulation of the propellant to achieve comparable energies. The increased proportion of binder to oxidiser provides added elongation and other good mechanical properties to the propellant, permitting the addition of other energetic fuels (for example aluminium).
From the logistics standpoint, the starting ingredients for manufacturing polyurethane were available from a large number of chemical suppliers, whereas the liquid polysulfide rubbers were manufactured almost exclusively by a single company. This had its effect on cost, quality, and delivery time.
One of the advantages of polyurethane was that a high concentration of nitrate ester could be incorporated in the binder to give increased energy. A commonly used polyurethane binder material was ESTANE, a product of B.F. Goodrich Chemical Company.
Polybutadiene.
Polybutadiene Acrylic Acid.
Almost concurrently with the evolution of the polyurethane propellants, a new type of binder based on long-chained polybutadiene backbone gained the attention of rocket manufacturers. The selection of polybutadiene binder for propellants to be used over wide temperature ranges was a natural one, since most butabiene copolymers (butadiene-styrene, butadiene-acrylonitrile, butadiene- methylvinyl pyridine) had glass-transition temperatures near or below -100°F. This was advantageous, since the mechanical behaviour of a propellant during periods of strain was related to its properties at different temperatures. For example, the ability of a propellant to withstand high strain rates such as those encountered on ignition of a large-diameter rocket motor was directly related to low-temperature properties such as elongation and brittle point. Therefore, the polybutadiene propellants were attractive, both for large motors and for those requiring wide temperature ranges of operation.
Probably the most widely used polybutadiene polymer (1967) had been PBAA, a copolymer of polybutadiene and acrylic acid. One of the added benefits of PBAA over polyurethane was that the binder system was less complex, consisting essentially of the liquid polymer and a single curative chemical such as an epoxide resin. In certain formulations where a large amount of oxidiser and an auxiliary metal-powder fuel such as aluminium was needed to provide high energy, it was necessary to add to the binder a liquid hydrocarbon or other low-viscosity fluid that acted as a plasticiser to aid in processing.
By contrast, the polyurethane system normally consisted of a main chain polymer such as a polyether diol, a shorter chain cross-linking agent (perhaps a trifunctional polyol), a curing agent (isocyanate) and a curing catalyst; polyurethanes also employ plasticisers where necessary, usually in the form of aliphatic esters such as dioctyladipate or dioctylsebacate.
Carboxy-Terminated Polybutadiene.
Throughout the 1950's propellant manufacturers depended mainly upon rubber chemicals that were readily available to provide the material used in the binders. Among these were PBAA, and the polyethers and polyesters used in polyurethane propellants.
However, at the beginning of the 1960's the designers of weapon systems appeared to be moving ahead of the propellant manufacturers from the standpoint of operational requirements. Thus it was necessary for the propellant research chemist to visualise the "perfect molecular structure" that would best fulfil the need, and then either make the material or work with a chemical supplier to make it.
The first of these custom-made polymers, pioneered by Phillips Petroleum Co. and first evaluated in propellant applications by Rocketdyne, was carboxy-terminated polybutadiene (CTPB). There was an advantage in placing the carboxyl groups at the end of the polymer chain rather than randomly spacing them along the chain (as PBAA polymers). This way the polymer chemist was provided with a uniform structure so he could control his binder network to give the desired mechanical properties. The reproducibility of a controlled system was naturally greater than that of a random structure.
However, the demand by the customer (primarily the US Government) for greater reliability and overall improved performance suggested that still better binders would be forthcoming. To improve reliability of the CTPB system, for example, a greater insight was needed into the affects of molecular weight and molecular-weight distribution. The influence of molecular structure (isomeric configuration) and minor impurities on mechanical properties was to be determined as part of the continuing research and development.
The interplay of mechanical forces between the binder, the aluminium particles, and the ammonium perchlorate crystals would have to be researched until greater knowledge was attained. Information on such fundamentals as energy of wetting, surface free-energy of the solids, the effect of these properties on cracking or other mechanical failure, kinetics of cross-linking reaction, and the effect of temperature and moisture on cure reversion was needed.
There was no doubt that knowledge in these areas would bring about improved hydrocarbon binders.
PBAN - Polybutadiene Acrylic Acid Acrylonitril Terpolymer (PBAN).
This was the formulation widely used on the 1960-70's big boosters (Titan III & Shuttle).
HTPB - Hydroxyl-Terminated Polybutadiene.
HTPB was the most recent state-of-the-art composite propellant binder, manufactured by ATOChem, Inc. (Boosters: Delta II, Delta III, future Delta IV, Titan IVB and Ariane).
NEW BINDERS TO MEET CLEAN AIR REQUIREMENTS.
Environmental concerns regarding the combustion products of large solid rocket motors used in space launch applications led to a number of 'environmentally friendly' binders being proposed.
GAP: Glycigyl azide polymer, a developmental energetic binder produced by 3M Co. and developed at Valcartier, near Québec, Canada.
Poly-NMMO: Poly-nitratomethyl, methyl oxetane, a developmental energetic binder with a high oxygen content, by Aerojet Solid Propulsion Co.
BTTN: Butanetrioltrinitrate, a highly oxygenated energetic plasticiser.
DMBT: Dimethylbitetrazole, a developmental high nitrogen solid fuel with a high positive heat of formation, used in propellants with oxidisers having high oxygen balances to increase performance, developed at NAWCWPNS.
Developments Outside of the USA
Other countries begin to study modern composite propellants around mid-1950. Polysulfide remained a nearly an exclusive product of Thiokol. In 1957 design bureau TsKB-7 in the USSR began the study of solid propellants for the D-6 SLBM system, but the technology was not mature. Beginning in 1961 TsKB-7 build the second and the third stages for the Korolev RT-2 ICBM (US code name SS-13 Savage), but the composite propellant technology in USSR remained many years behind that of the west. The RT-2 first flight was in 1966. Beginning in 1961, development began of the RT-15/8K96 mobile IRBM using two stages from the RT-2. The RT-15 would have a range of 4,500 km with a 1.4 tonne payload. However the project was abandoned in 1970 after 19 test launches.
PROPELLANT ADDITIVES
To help provide the high-energy propellants that were required for the more efficient space vehicles and missiles, many propellants used special fuel additives such as powdered metals. Powdered aluminium was used extensively in propellant formulation for the extra energy it contributed and for the help it gave in promoting stable burning. Although powdered beryllium had a higher theoretical energy value than aluminium, it was seldom used because of its extreme toxicity, relative scarcity, and higher cost. In addition, beryllium had a poor combustion efficiency with most of the hydrocarbon binder-fuels available. However, this could be improved by using it with unique and advanced binders like fluorocarbons.
THE SEARCH FOR HIGH ENERGY PROPELLANTS
After WW II, with the Cold War and the prospect of space travel, the search for exotic, energetic fuel was the rule. Boron was the star during the 1950s, but things changed during the 1960s and 1970s. Rocket fuel selection began with an evaluation of the elements from which candidate fuels were, or may be composed. The calculated variation in adiabatic combustion temperature for an oxygen reaction with some of the elements had been reported by Grosse and is reproduced in the table here.
These temperatures varied considerably and showed that some heavy elements were capable of producing even greater temperatures than light elements such as hydrogen and carbon. However, the heavy elements could quickly be eliminated from consideration (however note that the combustion temperatures would be different with fluorine or other oxidisers). A few, such as zirconium and titanium, were merely competitive on a volumetric heating value basis (BTU/cu ft) and considerably inferior on a gravimetric basis (BTU/lb). Light elements, such as hydrogen, lithium, beryllium, boron, carbon, magnesium and aluminium, appeared interesting.
Only hydrogen, beryllium and boron had higher heating value than the usual hydrocarbons (HC=~18-19). Beryllium was scarce and extremely toxic, and does not at this time merit serious consideration. High energy fuels, therefore, quickly become restricted to hydrogen and boron and a few classes of compounds containing hydrogen or boron. Special purpose fuels could also involve compounds containing lithium, magnesium, aluminium or carbon. (if one notes that a lighter element goes faster (exhaust velocity) for the same combustion temperature, it can be seen that the carbon and sulphur of black powder, and the sodium in Napalm, were very poor fuels).
EXTOTIC, HIGH ENERGY SOLID PROPELLANTS - THE VIEW IN THE 1960s.
Space and military applications stimulated chemical research so that many exotic and highly reactive ingredients for solid-propellant rockets were produced.
The oxidisers in use consisted of weakly held oxygen atoms in chlorine and nitrogen compounds. It was thought that future oxidisers would have less chlorine and nitrogen atoms, and most of the oxygen would be replaced by fluorine. Some oxygen would remain for the purpose of burning the carbon in the binder to carbon monoxide. Fluorine would be linked to oxygen and nitrogen atoms, with which it forms weak bounds. Nitronium perchlorate and its fluorine derivative (nitronium perfluorate?) were outstanding oxidisers at that time.
Fuels would be light-metal hydrides then known, but efforts would be made to replace these by less reactive hydrides of mixed nature. The fuel would be a light-metal hydride with a low heat of formation-one which yields fluorides and oxides with the highest heat of formation. Since rockets using exotic propellants would have a limited volume, the density of the propellant was of critical importance. The best fuels would be light-metal hydrides of low density, a factor which must be considered in the selection of the oxidiser and binder.
A major problem was to solve that of preventing the oxidiser and fuel from reacting with each other and with the organic polymeric binder material. Binders would have to be developed which were inert to the fuel and oxidiser. In addition, binders would have to prevent chemical interaction of fuel and oxidiser to avoid possible propellant explosions. The most likely binders would contain long chains of carbon atoms bearing fluorine atoms- (CF2)n -fluorocarbons). The fluorine would serve to consume the fuel and produce inert polymers. These binders would contain little hydrogen since the metal hydrides contained loosely held hydrogen. The performance of these future solid propellants would probably range from 285 to more than 300 seconds. The ultimate solid propellant (specific impulse of up to 350 seconds) would be composed of a binder containing sufficient oxygen to convert its carbon monoxide. A maximum of fluorine-oxygen-carbon groups was also desirable.
Binders more dense than the (CF2)n structure previously mentioned would be difficult to achieve since its density was 50 to 60 percent greater than conventional hydrocarbon binders. In view of compatibility problem with solid propellants, hybrid-propellant systems would have to be developed. Some liquid fuels and oxidisers were superior to their solid counterparts, so the hybrid system should be able to achieve performances which were superior to those of solid propellants.
EXOTIC INGREDIENTS - THE VIEW IN THE 1960s
The development of propellants with higher energy (250-300 Isp) and increased thermal stability (300°F- 500°F) necessitated the incorporation of some exotic chemicals into solid propellants and related devices. Many of these compounds had unusual hazards associated with their uses that were not immediately evident. Others had been used in various phases of research and development and had recognised toxic or explosive properties. The following section lists, with brief comments, some of the more important of these chemicals that were then used in the development of new propellants.
OXIDIZERS.
Nitronium perchlorate or NP (NO2ClO4)-Nitrosyle
Toxicity- Decomposes above 80°C or in contact with water and many organic compounds. The decomposition of NP releases oxides of nitrogen (NO,NO2) and chlorine (Cl2). Maximum allowable concentration are 5 ppm.
Sensitivity- Mixtures of NP with nearly all organic compounds are dangerous and explosives and are apt to explode spontaneously. Mixtures with other oxidisable materials behave similarly.
Uses- Proposed for use in high-energy propellants.
Lithium perchlorate or LP (LiClO4)
Toxicity- Not toxic unless large amounts taken orally.
Sensitivity- Same as potassium perchlorate. Mixtures with reducing agents are explosives (class B).
Uses- High-temperature propellants.
Hydrazinium diperchlorate or HP (N2H6(ClO4)2)
Toxicity- Decomposes to give chlorine gas (Cl2).
Sensitivity- Very hazardous material to handle. Extremely sensitive to impact and friction. Low auto-ignition temperature.
Uses- High-energy propellants.
FUELS
Lithium aluminium hydride or LAH (LiAlH4)
Toxicity- Dust was very irritating since it contains lithium hydroxide.
Explosive Hazards- Very dangerous to handle since it may ignite and burn violently. Dust may explode. Ignites spontaneously with water, alcohols, ammonium hydroxide, etc.
Uses- High-energy fuel.
Magnesium hydride (MgH2) and Lithium borohydride (LiBH4)
Toxicity- MgH2 was relatively non-toxic. LiBH4 was toxic and may release diborane (B2H6) on treatment with acids. B2H6 (also proposed in liquid fuel in the 50s, on B-70 for example) was extremely toxic, with a maximum allowable concentration less than 1 ppm.
Hazards- MgH2 and LiBH4 are much less hazardous than LiAlH4. They are similar to Mg powder, and release hydrogen.
Uses- High-energy fuel.
Powdered metals such as Zirconium (Zr) and Beryllium (Be)
Toxicity- Dust should not be inhaled. Beryllium dusts are very toxic.
Hazards- Finely powdered Zr was ignited by static electricity. Some powders are pyrophoric. Mixtures with oxidising agents are hazardous and easily exploded by static electricity.
Uses- Zr was used in igniters and various pyrotechnic devices while beryllium was an additive in high-energy propellants.
BINDERS
Nitrourethanes or NU
Toxicity- All nitro compounds are toxic, some extremely so. Many are absorbed through the skin. Some may cause dermatitis. The alisocyanates from which nitrourethanes are prepared are extremely hazardous.
Sensitivity- Nitrourethanes are generally class-C explosives, but a few may be more sensitive.
Uses- High energy propellants.
Nitramines (HMX, RDX)
Toxicity- Most similar to nitro compounds but more variable, depending on structure. Some may cause severe dermatitis.
Sensitivity- Some are class-B explosives. Nitrourethanes mixed with this group are generally class C.
Uses- Experimental only. (1967)
Tetrazoles
Toxicity- Toxic properties not well established but some are apparently non-toxic.
Sensitivity- Some propellants and pyrotechnic devices using tetrazoles accidentally exploded, causing several injuries. These devices are regarded as extremely hazardous.
Uses- Various pyrotechnic devices.(derivatives in high-energy propellants)
Fluorocarbons or FC
Toxicity- While many FC compounds are completely non-toxic, some are extremely toxic. Pyrolysis of many fluorocarbons may yield gaseous, odourless compounds of extreme toxicity. Kel-F, teflon, and other FC polymers release fluorolefins on heating which among the most toxic of gases. Combustion of FC propellants release toxic gases (hydrogen fluoride).
Sensitivity- FC derivatives are not explosive unless mixed with certain powdered metals, metal hydrides, and metallorganic derivatives. These mixtures are not easily exploded by shock, but are exploded by heating.
Uses- Experimental only.
Plasticizers
Toxicity- Many are relatively non-toxic but some of the nitrated or fluorinated materials must be regarded as toxic. Nitrocompounds are absorbed through the skin and cause dermatitis. Dinitriles are toxic; they are absorbed through the skin.
Sensitivity- All insensitive, except some nitro or nitramino plasticiser.
Uses- Improved propellants.

2006-01-05T18:42:00.000-08:00

Pushpendra
Composite Solid Propellant By Pushpendra Singh

Solid propellants of the composite type, containing separate fuel (or reducer, chemically) and oxidiser (in a separate compound) intimately mixed, replaced the simple double-base propellants to a considerable extent, especially for large non-military motors. The organic fuel material is initially in a liquid or semi-liquid form that can set to a solid (binder). Among the earliest substances used were asphalt and various synthetic rubbers. While generally not considered as composite, black powder was in fact the oldest composite propellant. Before 1940 black powder, in common use, was nearly synonymous with the words 'rocket motor' .
While working on the theory of rocket propulsion for his doctoral thesis in 1937, Frank Malina mentioned to Fritz Zwicky of Caltech some difficulties he was having in his study. Zwicky exploded with the opinion that Malina was wasting his time on an impossible subject. For, he said, Malina must realise that a rocket could not operate in space as it required the atmosphere to push against to provide thrust! By 1940 he realised that he was mistaken.
At Guggenheim Aeronautical Laboratory, California Institute of Technology (GALCIT),in 1939, one of the first objectives was to develop a solid propellant rocket unit capable of delivering a constant thrust on the order of 1000 pounds for a period of 10 to 30 seconds. As far as is known, no black powder or smokeless powder rocket had ever been constructed to meet these specifications of thrust and duration. Experts consulted by Malina, John Parsons, and Forman were very dubious about the possibility of doing so.
Preliminary experiments made by Parson and Forman with pressed solid propellant charges restricted to burn cigarette-fashion appeared to support this view. It was generally believed that the combustion chamber pressure of a restricted burning solid rocket unit would continue to rise from the moment of ignition until any combustion chamber of reasonable weight would burst. In other words, it was thought that such combustion was inherently unstable.
The GALCIT group's mentor, Professor Theodore von Karman, in the spring of 1940, had to listen to both the opinions of the experts and to the explosions of Parson's rockets. One evening at home Von Karman wrote down four differential equations describing the operation of an ideal restricted burning motor, and asked Malina to solve them. It was found that, theoretically, a restricted burning unit would maintain a constant chamber pressure as long as the ratio of the area of the throat of the exhaust nozzle to the burning area of the propellant charge remained constant, that is, the process was stable. Experimental verification of the theory was soon obtained.
Although there have been centuries of experiments with black powder rocket, and several investigators used smokeless powder and Ballistite in rockets between about 1918 and 1939, none of these rockets had the thrust and duration required for the aircraft "super-performance" applications. Parsons and Forman in 1938 built and tested a smokeless powder constant-volume combustion motor similar to the one that had been used by Goddard. They concluded after these tests that the mechanical complications of constructing an engine using successive impulses to obtain thrust durations of over 10 seconds was impractical. Upon Parson's recommendation, they concentrated their efforts on the development of a motor provided with a restricted burning powder charge that would burn at one end only at constant pressure to provide a constant thrust.
Parsons started with the traditional sky rocket. This type of pyrotechnic device was propelled by a black powder charge pressed into a cardboard combustion chamber with a conical hole in its centre. The gases escaped through a rounded clay orifice. Its efficiency was very, very low, but it was reliable. The conical hole in the charge was believed to be the secret that kept the charge from burning down the sides of the container or to produce chamber pressures that would burst the container. The longest duration of thrust of this motor did not exceed about 1 second.
During 1939 and 1940, various mixtures based on black powder and mixtures of black powder with smokeless powder were tested in 1 in. and 3 in. diameter chambers. The charge for the 3 in. chamber was made up of 6 in. long pellets compressed at around 6,500 psi., and coated with various substances to form a solid or liquid seal between the charge and the walls of the chamber. The charge of the 1 in. chamber was pressed directly into the chamber in small increments at pressures between 7,700 and 12,000 psi. Most of the tests of these charges ended in an explosion.
Mechanical causes for failures, such as burning of the charge on the surface next to the wall because of leakage, transfer of heat down the walls sufficient to ignite the sides of the charge, and cracking of the charge under combustion pressure, were suspected. However, there were those who were convinced that the combustion process of a restricted burning charge in a rocket motor was basically unstable. Only after von Karman and Malina proved the process was stable in their analysis of the characteristics of the ideal solid propellant rocket motor in the spring of 1940 was a concentrated effort was made to study the mechanical causes of failure.
Hundred of tests were then made with different powder mixtures, using black powder as the basic ingredient, with various loading techniques and various motor designs. The dependence of chamber pressure on the ratio of chamber cross section area to nozzle throat area was determined for each specific powder mixture.
By the spring of 1941 the results were sufficiently encouraging to schedule flight tests of an aircraft equipped with solid propellant rockets specially designed for it. The propellant charge used in the Ercoupe motor was a type of amide black powder designated as GALCIT 27 (amide: organic compound containing carbon, hydrogen, oxygen, and nitrogen. Some examples: HCONH2, CH3CONH2, C6H13CONH2). The 2 lb. charge was pressed into the combustion chamber, which had a blotting paper liner, in 22 increments by a plunger with a conical nose shape at a pressure of 18 tons. The diameter of the charge was 1.75 in. and its length varied between 10 and 11 in. The motor was designed to deliver about 28 lb. thrust for about 12 seconds.
Eighteen rocket motors were delivered every other day for the first tests at March Field, California, about an hour's drive from the project. During the first phase of the flight tests one motor failed explosively in a static test and one while Ercoupe was in level flight. Thereafter, 152 motors were used in succession without explosive failure. The motors were prepared by Parsons, Forman, and Fred Miller.
On August 16, 1941, Boushey made the first take-off of the Ercoupe with six JATOs firing. The first American manned flight of an aircraft propelled by rocket thrust alone was made by Boushey on August 23, 1941. The propeller of the Ercoupe was removed and 12 JATO units installed, of which only 11 functioned. The Ercoupe was pulled by a truck to a speed of about 25 m.p.h. before the JATOs were ignited. The airplane left the ground and reached an altitude of about 20 ft. This flight was not originally scheduled but the group could not resist the opportunity to make the improvised demonstration of the future possibility of rocket propulsion.
Frank Malina noted that it was most fortunate that the flight tests were carried out close to the location of the project, which permitted the rocket motors to be fired within a few days from the time they were charged with propellant. Following the flight tests, it was found that after the motors were exposed to simulated storage and temperature conditions over several days they exploded in most cases. It was evident that either the blotting paper liner or the mechanical characteristics of the propellant were unsatisfactory.
But the Navy Department regarded the successful Ercoupe tests with much interest from the point of view of application of rockets for assisted take-off of aircraft from aircraft carriers. Upon the urging of Lt. C.F. Fischer of the Bureau of Aeronautics, who had witnessed the tests, a contract was placed by the Navy with the Project in early 1942 for the development of a 200 lb. thrust, 8 second unit. The unit was designated by the acronym JATO for Jet Assisted Take-Off (sometime RATO), and this designation is still used.
This Navy contract came in the midst of the explosive failure of the JATO unit developed for the Ercoupe tests. All efforts to improve the amide-black powder propellant and loading techniques of the motor developed for Ercoupe tests failed to meet specified storage conditions ranging from Alaska to Africa. Investigations of motors using Ballistite also proved negative, mainly because of its ambient temperature sensitivity (variation of its rate of burning and thrust with ambient temperature).
Thus, the spring of 1942 was one of desperation for those concerned with development of a reliable solid propellant JATO unit. They knew that theoretically it was possible to construct such an engine, but no one came forward with a promising idea until June, when Parsons, no doubt after communing with his poetic spirits, suggested trying a radical new propellant. It would consist of potassium perchlorate (KClO4- in place of potassium nitrate KNO3: saltpetre), as oxidiser, common asphalt as used on roads as a binder and fuel. These could be cast, after being mixed, into a combustion chamber.
A test of the propellant, designated GALCIT 53, was quickly made and the results were so promising that work on other propellant types was dropped for a long time. Parsons was assisted in the development of the asphalt base propellant by Mills and Fred Miller. After due study of the origin of the ideas for the new propellant, Parsons was recognised as its inventor and a patent was granted in his name.
At first, the Ordnance Department objected strongly to the use of potassium perchlorate as an oxidiser because it had proved unsafe in the past. Parsons realised that their objection was no longer valid, since way had been found to produce the material with a minimum purity of 99%. Impurities in the form of dangerous chlorates (KClO3) had been practically eliminated. Sodium and potassium chlorates were used with dinitrotoluen in explosives (know as cheddites in French), also with perchlorates and various hydrocarbons-vaseline-,castor oil, and nitro. Potassium chlorate was also used as oxidiser in matches with phosphorus sesquisulfide P4S3 or tetraphosphorus trisulfide as the active fuel.
The ruling of the Ordnance Department was thereafter changed, allowing the use of this kind of solid oxidiser. The Navy contract for 100 JATO units delivering 200 lb. thrust for 8 seconds was successfully completed, with GALCIT 53 as the propellant. Production of service-type units for the Navy began shortly thereafter at the Aerojet Engineering Corporation (organised at the end of 1941 and formally incorporated on March 19, 1942 with the GALCIT members Von Karman, Malina, Haley, Parsons, Forman, and Summerfield).
The project carried out extensive studies on asphalt-base propellants in the following years. A detailed report released in May 1944 on the propellant GALCIT 61-C by Mills give the following composition: 76% potassium perchlorate and 24% fuel. The fuel component was 70% Texaco No. 18 asphalt and 30% Union Oil Company Pure Penn SAE No. 10 lubricating oil. The fuel was liquefied at about 275°F, the pulverised potassium perchlorate added to it, and the mixture thoroughly stirred. The mixture was then poured into the combustion chamber, which had been previously lined with a material similar to the fuel component, and allowed to cool and become hard. This propellant, when burned at a chamber pressure of 2,000 psi., had a chamber temperature of 3,000-3,500°F, a specific impulse of 186, and an exhaust velocity of about 5,900 ft. per sec. Storage temperature limits were from -9 deg F to 120 deg F. GALCIT 61-C was developed in 1943 and used in service JATO units by the Navy until the end of World War II. The propellant is also used on the Private A and F research rockets.
IMPROVEMENTS
Solid propellants utilising potassium perchlorate as oxidiser produced dense clouds of white smoke (potassium chloride-KCl, like sodium chloride-NaCl, common salt), which the Navy did not like at all. Some months after GALCIT 53 was developed, Parsons informed the Project weekly research conference that he had eliminated the smoke problem by replacing potassium perchlorate with ammonium perchlorate (NH4ClO4). Navy rocket experts were immediately invited to visit the Project for a demonstration:
"When they arrived we posted ourselves some distance from the test pit, the red flag was run up, and Parsons gave the order for his latest creation to be fired. We beheld a big cloud of with smoke and Parsons with a look of surprise on his face. He sheepishly explained that the smoke must have been caused by the humidity, for the air had been very dry on the days they had made tests before".
Ammonium perchlorate does reduce the amount of smoke produced if the air is dry, but it produces undesirable chloride in the jet. In fact Cl and H in NH4ClO4 may combine to form HCl, hydrogen chloride or hydrochloric acid with water. But that is the base of modern composite propellants.
The project also studied the possible use of other fuels instead of asphalt, such as Napalm (sodium palmitate = NaPalm - first tried as a high temperature, high energy propellant), gelled hydrocarbons, gelled wax mixtures, and butyl rubber. A continuation of studies of the last material later led Charles Bartley, under the JPL-ORDCIT Project in 1945, to the discovery of the advantages of the castable elastomeric (polysulfide rubber) material called Thiokol. This discovery became the basis of solid propellant manufacture by the Thiokol Chemical Corporation. The Air Force Material Command terminated work by the Project on solid propellant motors on June 30, 1944. The Ordnance Department, however, continued the work for long range missile applications.
During the course of this research, engineers were provided with methods of motor component design when the following characteristics of the propellant to be used were known:
Sensitivity of the propellant to ambient temperature during combustion.
Combustion pressure limit below which the propellant burns in irregular manner.
Combustion pressure limit above which the propellant burns in an unpredictable manner.
Storage characteristics of the propellant charge from the point of view of minimum and maximum ambient temperatures allowed and possible decomposition of the propellant with prolonged storage.
Ignition temperature of the propellant.
Rate of burning of the propellant as function of the combustion pressure.
Performance characteristics of the propellant to produce rocket thrust.
The great progress made in the scientific design of solid propellant rocket motors in comparison with the empirical, traditional, method used in previous centuries can be appreciated by reference to the text "Jet Propulsion" prepared for the course at Caltech at the request of the Air Technical Service Command in 1943 and continued in the following years. The debate on the superiority of solid vs. liquid propellant rocket engines for boosters of space vehicles still rages today (but environmental considerations now favour liquid propellants).
Sponsorship of solid-propellant research was taken over by the ORDCIT Project from the Air Force Materiel Command on July 1, 1944. By this time, JPL had made the following fundamental contributions to the design and construction of long-duration solid-propellant engines:
Theory: Von Karman-Malina theory of constant-thrust long- duration engines (1940)
Propellant development:
Parsons' break-away from Ballistite with amide black powder (1940)
Parsons' introduction of perchlorates as an oxidiser (1942).
Parsons' introduction of asphalt as fuel-binder with perchlorates; the invention of a castable case- bonded composite propellant charge (1942).
Engine component design
Parsons' design of a restricted-burning (case- bounded) propellant charge with amine black powder (1940).
Malina-Mills design of a safety pressure relief valve (1942).
Mills' review of various types of burning surfaces of a charge and theoretical confirmation that the surface of a cigarette-type burning charge was stable (1943).
After the successful JATO development with the asphalt- perchlorate propellant in 1942, Mills sought a fuel-binder for the perchlorate superior to asphalt. In 1944, Charles Bartley joined Mills' group, and in 1945 introduced as a replacement for asphalt a castable elastomeric material, polysulfide rubber, produced by Thiokol Chemical Corporation. The polysulfide rubber, compared to asphalt, produced a propellant much better both as regards storage temperature limits and hardness at high atmospheric temperatures. The latter property was especially important in the design of high-thrust engines requiring a charge with an internal-burning surface rather than a cigarette-burning surface.
Since at this time only Aerojet in the USA was producing composite solid-propellant engines, that company's attention was drawn to the asphalt replacement, but it was already interested in a similar material made by the General Tire and Rubber Co. It was only at the urging of the Ordnance Department that the Thiokol Chemical Corp. entered the field of composite solid propellants with the new fuel-binder discovered at JPL.
After obtaining the experience with the composite solid- propellant missiles Private A and F, studies began at JPL in 1946 on larger missiles using, in particular, the polysulfide rubber-perchlorate type propellant. The results of these studies led eventually to the design of the tactical guided missile, Sergeant.
The laboratory followed closely development with other type of solid propellants, especially Ballistite, used in high-thrust short-duration engines suitable for boosters (Aerojet built some double-base boosters using this material).
Other special-purpose rocket vehicles supported research in solid propellants and high-acceleration, and high-speed dynamics. A small vehicle unofficially called "Thunderbird" demonstrated the polysulfide composite-propellant, internal-burning star-grain solid motor in 1947. With an acceleration of over 100 G, (a precursor of the Sprint missile) it led to the Wac-scale solid-propellant research vehicle called Sergeant in 1948.
This Sergeant sounding rocket, unrelated to the tactical missile of the same name, proved to be ahead of its time. It was inspired by calculations that indicated a solid-propellant rocket of the internal-burning-star design could deliver several times the payload of a liquid-propelled V-2 type of similar weight. The motor chamber walls were very thin because the propellant, burning from within, would help contain heat and pressure.
An autopilot design effort was begun, and static tests of the motor, weighing 1300 lbs and delivering about 6000 lbs thrust for more than 30 seconds, were conducted.
Difficulties with this solid rocket, manifested in the rupture of the thin-wall case, coincided with a change in the JPL mission and an acceleration and expansion of Corporal development. The Sergeant project was suspended. The electronic autopilot was adopted for the Corporal missile while the solid-propellant engineers took their problems back to the laboratory and test stand for more investigation. Further development was undertaken by the Thiokol Chemical Corporation. The ultimate heritage of this early "Sergeant" powerplant was the reliable solid rocket, used in large scale in the Sergeant and other military missiles, and in clustered miniatures to launch the first Explorer satellites.
The motor evolved from the Sergeant test vehicle of 1948-49 via the Hermes RV-A-10 flight tested in March 1953. A Hermes A-2 Thiokol motor was ground tested in December 1951. The Hermes A-2 program was ended in October 1952.
The Sergeant missile was not the only result of the Thiokol polysulfide motor. Another major development was the Nike-Hercules sustainer motor (or stage two), the Lacrosse motor, and later the Bomarc B motor. Many small missiles, sounding rocket motors, and the Mercury and Gemini retro-rockets used the same propellant.
However, the use of polysulfide by Thiokol probably caused their loss of the key Polaris contract. Aerojet won the contract with the use of a more energetic polyurethane propellant.
After that Thiokol began the use of polybutadiene for big motors and won the contract for the Minuteman first stage motor. That lead as well to the Nike-Zeus, Pershing, Castor motors, Surveyor retro (first of a series of upper stage motors) and finally to the Shuttle SRB's.
Meanwhile, Hercules began the use of double-base propellant as fuel in composite propellants, since double-based motors burned with excess of fuel. The use of a separate oxidiser also permitted the addition of energetic fuels such as aluminium powder.
The excess of fuel in pure double-base caused a long afterburning flame, essentially of burning carbon (see launch-photographs of Nike Ajax and Hercules, Honest John, Terrier, and Talos). The unburned carbon cause also the dark exhaust before the afterburning.
The Hercules' Minuteman third stage was a follow-on of the Vanguard third stage.
Some composite propellants continue to use saltpetre (potassium nitrate) or ammonium nitrate.
Some composite propellant formulations and characteristics:
Molded composite: potassium nitrate(20-50%), elastomer(10%), ammonium picrate-NH4C6H2NO7-(70-40%). Specific impulse s.l.: 160 to 200 sec. Abundant smoke. Hard to brittle.
Castable composite: ammonium nitrate(80%), elastomer (18%), catalyst(2%). Specific impulse s.l.: 185 to 198 sec. Little smoke. Soft and resilient to hard and tough.
Castable composite: ammonium perchlorate(50-85%), elastomer(50-15%). Specific impulse s.l.: 175 to 240 sec. Much smoke at low oxidiser; little at high oxidiser; mist at relative humidity greater than 80%. Soft and resilient to hard and tough.
Castable composite: potassium perchlorate(50-80%), elastomer(50-20%). Specific impulse s.l.: 165 to 210 sec. Abundant smoke. Soft and resilient to hard and tough.
OXIDISERS
Ammonium perchlorate is the most widely used today. It is characterised by high heat, is a good gas producer (not a smoke producer), percent of oxygen by weigh: 34 percent, specific gravity: 1.9.
Potassium perchlorate is used for fast burning rates. It is characterised by high heat, is a low gas producer, percent of oxygen by weight: 46 percent, specific gravity: 2.5.
Ammonium nitrate is used for slower burning rates. It is characterised by low heat, is a high gas producer, and is good for gas generator propellants. It requires a greater amount of binder (fuel) to make castable, but too much binder produces excessive smoke. Ammonium nitrate's percent of oxygen by weight: 20 percent, specific gravity: 1.9. It may be the oxidiser for the future. It contains no toxic elements and no solid elements, produces no solids by decomposition, and therefore, together with a high energy non-polluting fuel, could provide a more 'environmentally friendly' solid propellant.
Lithium perchlorate, a proposed oxidiser, is very hygroscopic and may be used in some high-temperature propellants. Percent of oxygen by weight: 60 percent, specific gravity:2.4.
BINDER SYSTEMS
Introduction
The original composite propellants, used in JATO units, contained an asphalt binder. Since asphalt-perchlorate composites had poor performance and formulation characteristics, extensive research and development work was directed toward their improvement. This soon led to the discovery and acceptance of new and better chemical binder-fuels, primarily synthetic rubbers Initially, polysulfide liquid polymers were developed with only physical properties that were an improvement over those of asphalt. Later, with certain chemical-structure modifications, the overall performance of polysulfide soon outshone that of asphalt. Polysulphides, however, had a major drawback in that they released water during combustion; which interfered with efficient burning. The water by-product also limited the type of additives that could be mixed with the propellant, since water was highly reactive with materials such as aluminium. In the search for binder-fuels without the drawbacks of asphalt and polysulfides, polyurethanes (synthetic thermosetting or thermoplastic polymers) were found to have good performance and physical properties. With these aluminium could be incorporated for higher specific impulse. However, polyurethanes were so viscous that the amount of oxidisers and other solid additives that could be incorporated was limited. Eventually polybutadiene- based propellants were developed that had physical properties superior to those of polyurethanes.
Polysulfide
Polysulfide was the first binder elastomer fuel. For rocket applications a low-molecular-weight polymer was made from dichlorodiethyl formal; sodium polysulfide was used as the liquid binder. When the mixture was heated with an appropriate curing agent such as zinc oxide, the links between adjacent polymer chains were joined together to form the rubber network. The resulting binder had a glass-transition temperature near -60°F., making it usable to about -40°F. This was a distinct advantage over the first composites.
An undesirable quality of the polysulfides was the presence of sulphur atoms in the system. They produced high-molecular-weight exhaust products (sulphur dioxide with a molecular weight of 64) thereby lowering specific impulse. Since a large amount of oxidiser had to be mixed with the binder to obtain the high energy desired, the binder lost much of its rubber-like quality.
There were many organic and inorganic materials that acted as oxidisers and could be used to cure liquid polysulfide polymers. Each had its advantages and disadvantages.
Thiokol developed many varieties of polysulfides with improved qualities.
Polyurethane
Polyurethanes were the second elastomer fuel binder. The group of polymers known as polyurethanes were made by combining polyols with isocianates. The versatility in polymer chemistry was such that a large number of starting materials having varying molecular weights were available.
Compared with the polysulfides, the average molecular weight of the polyurethanes' exhaust gases was lower. This was because the polyurethanes contained only carbon, hydrogen, oxygen, and nitrogen atoms (not sulphur). An additional benefit was claimed in the processing: the backbone polymer contained substantial amounts of oxygen. It was not necessary therefore to use as great a percentage of oxidiser in the formulation of the propellant to achieve comparable energies. The increased proportion of binder to oxidiser provides added elongation and other good mechanical properties to the propellant, permitting the addition of other energetic fuels (for example aluminium).
From the logistics standpoint, the starting ingredients for manufacturing polyurethane were available from a large number of chemical suppliers, whereas the liquid polysulfide rubbers were manufactured almost exclusively by a single company. This had its effect on cost, quality, and delivery time.
One of the advantages of polyurethane was that a high concentration of nitrate ester could be incorporated in the binder to give increased energy. A commonly used polyurethane binder material was ESTANE, a product of B.F. Goodrich Chemical Company.
Polybutadiene.
Polybutadiene Acrylic Acid.
Almost concurrently with the evolution of the polyurethane propellants, a new type of binder based on long-chained polybutadiene backbone gained the attention of rocket manufacturers. The selection of polybutadiene binder for propellants to be used over wide temperature ranges was a natural one, since most butabiene copolymers (butadiene-styrene, butadiene-acrylonitrile, butadiene- methylvinyl pyridine) had glass-transition temperatures near or below -100°F. This was advantageous, since the mechanical behaviour of a propellant during periods of strain was related to its properties at different temperatures. For example, the ability of a propellant to withstand high strain rates such as those encountered on ignition of a large-diameter rocket motor was directly related to low-temperature properties such as elongation and brittle point. Therefore, the polybutadiene propellants were attractive, both for large motors and for those requiring wide temperature ranges of operation.
Probably the most widely used polybutadiene polymer (1967) had been PBAA, a copolymer of polybutadiene and acrylic acid. One of the added benefits of PBAA over polyurethane was that the binder system was less complex, consisting essentially of the liquid polymer and a single curative chemical such as an epoxide resin. In certain formulations where a large amount of oxidiser and an auxiliary metal-powder fuel such as aluminium was needed to provide high energy, it was necessary to add to the binder a liquid hydrocarbon or other low-viscosity fluid that acted as a plasticiser to aid in processing.
By contrast, the polyurethane system normally consisted of a main chain polymer such as a polyether diol, a shorter chain cross-linking agent (perhaps a trifunctional polyol), a curing agent (isocyanate) and a curing catalyst; polyurethanes also employ plasticisers where necessary, usually in the form of aliphatic esters such as dioctyladipate or dioctylsebacate.
Carboxy-Terminated Polybutadiene.
Throughout the 1950's propellant manufacturers depended mainly upon rubber chemicals that were readily available to provide the material used in the binders. Among these were PBAA, and the polyethers and polyesters used in polyurethane propellants.
However, at the beginning of the 1960's the designers of weapon systems appeared to be moving ahead of the propellant manufacturers from the standpoint of operational requirements. Thus it was necessary for the propellant research chemist to visualise the "perfect molecular structure" that would best fulfil the need, and then either make the material or work with a chemical supplier to make it.
The first of these custom-made polymers, pioneered by Phillips Petroleum Co. and first evaluated in propellant applications by Rocketdyne, was carboxy-terminated polybutadiene (CTPB). There was an advantage in placing the carboxyl groups at the end of the polymer chain rather than randomly spacing them along the chain (as PBAA polymers). This way the polymer chemist was provided with a uniform structure so he could control his binder network to give the desired mechanical properties. The reproducibility of a controlled system was naturally greater than that of a random structure.
However, the demand by the customer (primarily the US Government) for greater reliability and overall improved performance suggested that still better binders would be forthcoming. To improve reliability of the CTPB system, for example, a greater insight was needed into the affects of molecular weight and molecular-weight distribution. The influence of molecular structure (isomeric configuration) and minor impurities on mechanical properties was to be determined as part of the continuing research and development.
The interplay of mechanical forces between the binder, the aluminium particles, and the ammonium perchlorate crystals would have to be researched until greater knowledge was attained. Information on such fundamentals as energy of wetting, surface free-energy of the solids, the effect of these properties on cracking or other mechanical failure, kinetics of cross-linking reaction, and the effect of temperature and moisture on cure reversion was needed.
There was no doubt that knowledge in these areas would bring about improved hydrocarbon binders.
PBAN - Polybutadiene Acrylic Acid Acrylonitril Terpolymer (PBAN).
This was the formulation widely used on the 1960-70's big boosters (Titan III & Shuttle).
HTPB - Hydroxyl-Terminated Polybutadiene.
HTPB was the most recent state-of-the-art composite propellant binder, manufactured by ATOChem, Inc. (Boosters: Delta II, Delta III, future Delta IV, Titan IVB and Ariane).
NEW BINDERS TO MEET CLEAN AIR REQUIREMENTS.
Environmental concerns regarding the combustion products of large solid rocket motors used in space launch applications led to a number of 'environmentally friendly' binders being proposed.
GAP: Glycigyl azide polymer, a developmental energetic binder produced by 3M Co. and developed at Valcartier, near Québec, Canada.
Poly-NMMO: Poly-nitratomethyl, methyl oxetane, a developmental energetic binder with a high oxygen content, by Aerojet Solid Propulsion Co.
BTTN: Butanetrioltrinitrate, a highly oxygenated energetic plasticiser.
DMBT: Dimethylbitetrazole, a developmental high nitrogen solid fuel with a high positive heat of formation, used in propellants with oxidisers having high oxygen balances to increase performance, developed at NAWCWPNS.
Developments Outside of the USA
Other countries begin to study modern composite propellants around mid-1950. Polysulfide remained a nearly an exclusive product of Thiokol. In 1957 design bureau TsKB-7 in the USSR began the study of solid propellants for the D-6 SLBM system, but the technology was not mature. Beginning in 1961 TsKB-7 build the second and the third stages for the Korolev RT-2 ICBM (US code name SS-13 Savage), but the composite propellant technology in USSR remained many years behind that of the west. The RT-2 first flight was in 1966. Beginning in 1961, development began of the RT-15/8K96 mobile IRBM using two stages from the RT-2. The RT-15 would have a range of 4,500 km with a 1.4 tonne payload. However the project was abandoned in 1970 after 19 test launches.
PROPELLANT ADDITIVES
To help provide the high-energy propellants that were required for the more efficient space vehicles and missiles, many propellants used special fuel additives such as powdered metals. Powdered aluminium was used extensively in propellant formulation for the extra energy it contributed and for the help it gave in promoting stable burning. Although powdered beryllium had a higher theoretical energy value than aluminium, it was seldom used because of its extreme toxicity, relative scarcity, and higher cost. In addition, beryllium had a poor combustion efficiency with most of the hydrocarbon binder-fuels available. However, this could be improved by using it with unique and advanced binders like fluorocarbons.
THE SEARCH FOR HIGH ENERGY PROPELLANTS
After WW II, with the Cold War and the prospect of space travel, the search for exotic, energetic fuel was the rule. Boron was the star during the 1950s, but things changed during the 1960s and 1970s. Rocket fuel selection began with an evaluation of the elements from which candidate fuels were, or may be composed. The calculated variation in adiabatic combustion temperature for an oxygen reaction with some of the elements had been reported by Grosse and is reproduced in the table here.
These temperatures varied considerably and showed that some heavy elements were capable of producing even greater temperatures than light elements such as hydrogen and carbon. However, the heavy elements could quickly be eliminated from consideration (however note that the combustion temperatures would be different with fluorine or other oxidisers). A few, such as zirconium and titanium, were merely competitive on a volumetric heating value basis (BTU/cu ft) and considerably inferior on a gravimetric basis (BTU/lb). Light elements, such as hydrogen, lithium, beryllium, boron, carbon, magnesium and aluminium, appeared interesting.
Only hydrogen, beryllium and boron had higher heating value than the usual hydrocarbons (HC=~18-19). Beryllium was scarce and extremely toxic, and does not at this time merit serious consideration. High energy fuels, therefore, quickly become restricted to hydrogen and boron and a few classes of compounds containing hydrogen or boron. Special purpose fuels could also involve compounds containing lithium, magnesium, aluminium or carbon. (if one notes that a lighter element goes faster (exhaust velocity) for the same combustion temperature, it can be seen that the carbon and sulphur of black powder, and the sodium in Napalm, were very poor fuels).
EXTOTIC, HIGH ENERGY SOLID PROPELLANTS - THE VIEW IN THE 1960s.
Space and military applications stimulated chemical research so that many exotic and highly reactive ingredients for solid-propellant rockets were produced.
The oxidisers in use consisted of weakly held oxygen atoms in chlorine and nitrogen compounds. It was thought that future oxidisers would have less chlorine and nitrogen atoms, and most of the oxygen would be replaced by fluorine. Some oxygen would remain for the purpose of burning the carbon in the binder to carbon monoxide. Fluorine would be linked to oxygen and nitrogen atoms, with which it forms weak bounds. Nitronium perchlorate and its fluorine derivative (nitronium perfluorate?) were outstanding oxidisers at that time.
Fuels would be light-metal hydrides then known, but efforts would be made to replace these by less reactive hydrides of mixed nature. The fuel would be a light-metal hydride with a low heat of formation-one which yields fluorides and oxides with the highest heat of formation. Since rockets using exotic propellants would have a limited volume, the density of the propellant was of critical importance. The best fuels would be light-metal hydrides of low density, a factor which must be considered in the selection of the oxidiser and binder.
A major problem was to solve that of preventing the oxidiser and fuel from reacting with each other and with the organic polymeric binder material. Binders would have to be developed which were inert to the fuel and oxidiser. In addition, binders would have to prevent chemical interaction of fuel and oxidiser to avoid possible propellant explosions. The most likely binders would contain long chains of carbon atoms bearing fluorine atoms- (CF2)n -fluorocarbons). The fluorine would serve to consume the fuel and produce inert polymers. These binders would contain little hydrogen since the metal hydrides contained loosely held hydrogen. The performance of these future solid propellants would probably range from 285 to more than 300 seconds. The ultimate solid propellant (specific impulse of up to 350 seconds) would be composed of a binder containing sufficient oxygen to convert its carbon monoxide. A maximum of fluorine-oxygen-carbon groups was also desirable.
Binders more dense than the (CF2)n structure previously mentioned would be difficult to achieve since its density was 50 to 60 percent greater than conventional hydrocarbon binders. In view of compatibility problem with solid propellants, hybrid-propellant systems would have to be developed. Some liquid fuels and oxidisers were superior to their solid counterparts, so the hybrid system should be able to achieve performances which were superior to those of solid propellants.
EXOTIC INGREDIENTS - THE VIEW IN THE 1960s
The development of propellants with higher energy (250-300 Isp) and increased thermal stability (300°F- 500°F) necessitated the incorporation of some exotic chemicals into solid propellants and related devices. Many of these compounds had unusual hazards associated with their uses that were not immediately evident. Others had been used in various phases of research and development and had recognised toxic or explosive properties. The following section lists, with brief comments, some of the more important of these chemicals that were then used in the development of new propellants.
OXIDIZERS.
Nitronium perchlorate or NP (NO2ClO4)-Nitrosyle
Toxicity- Decomposes above 80°C or in contact with water and many organic compounds. The decomposition of NP releases oxides of nitrogen (NO,NO2) and chlorine (Cl2). Maximum allowable concentration are 5 ppm.
Sensitivity- Mixtures of NP with nearly all organic compounds are dangerous and explosives and are apt to explode spontaneously. Mixtures with other oxidisable materials behave similarly.
Uses- Proposed for use in high-energy propellants.
Lithium perchlorate or LP (LiClO4)
Toxicity- Not toxic unless large amounts taken orally.
Sensitivity- Same as potassium perchlorate. Mixtures with reducing agents are explosives (class B).
Uses- High-temperature propellants.
Hydrazinium diperchlorate or HP (N2H6(ClO4)2)
Toxicity- Decomposes to give chlorine gas (Cl2).
Sensitivity- Very hazardous material to handle. Extremely sensitive to impact and friction. Low auto-ignition temperature.
Uses- High-energy propellants.
FUELS
Lithium aluminium hydride or LAH (LiAlH4)
Toxicity- Dust was very irritating since it contains lithium hydroxide.
Explosive Hazards- Very dangerous to handle since it may ignite and burn violently. Dust may explode. Ignites spontaneously with water, alcohols, ammonium hydroxide, etc.
Uses- High-energy fuel.
Magnesium hydride (MgH2) and Lithium borohydride (LiBH4)
Toxicity- MgH2 was relatively non-toxic. LiBH4 was toxic and may release diborane (B2H6) on treatment with acids. B2H6 (also proposed in liquid fuel in the 50s, on B-70 for example) was extremely toxic, with a maximum allowable concentration less than 1 ppm.
Hazards- MgH2 and LiBH4 are much less hazardous than LiAlH4. They are similar to Mg powder, and release hydrogen.
Uses- High-energy fuel.
Powdered metals such as Zirconium (Zr) and Beryllium (Be)
Toxicity- Dust should not be inhaled. Beryllium dusts are very toxic.
Hazards- Finely powdered Zr was ignited by static electricity. Some powders are pyrophoric. Mixtures with oxidising agents are hazardous and easily exploded by static electricity.
Uses- Zr was used in igniters and various pyrotechnic devices while beryllium was an additive in high-energy propellants.
BINDERS
Nitrourethanes or NU
Toxicity- All nitro compounds are toxic, some extremely so. Many are absorbed through the skin. Some may cause dermatitis. The alisocyanates from which nitrourethanes are prepared are extremely hazardous.
Sensitivity- Nitrourethanes are generally class-C explosives, but a few may be more sensitive.
Uses- High energy propellants.
Nitramines (HMX, RDX)
Toxicity- Most similar to nitro compounds but more variable, depending on structure. Some may cause severe dermatitis.
Sensitivity- Some are class-B explosives. Nitrourethanes mixed with this group are generally class C.
Uses- Experimental only. (1967)
Tetrazoles
Toxicity- Toxic properties not well established but some are apparently non-toxic.
Sensitivity- Some propellants and pyrotechnic devices using tetrazoles accidentally exploded, causing several injuries. These devices are regarded as extremely hazardous.
Uses- Various pyrotechnic devices.(derivatives in high-energy propellants)
Fluorocarbons or FC
Toxicity- While many FC compounds are completely non-toxic, some are extremely toxic. Pyrolysis of many fluorocarbons may yield gaseous, odourless compounds of extreme toxicity. Kel-F, teflon, and other FC polymers release fluorolefins on heating which among the most toxic of gases. Combustion of FC propellants release toxic gases (hydrogen fluoride).
Sensitivity- FC derivatives are not explosive unless mixed with certain powdered metals, metal hydrides, and metallorganic derivatives. These mixtures are not easily exploded by shock, but are exploded by heating.
Uses- Experimental only.
Plasticizers
Toxicity- Many are relatively non-toxic but some of the nitrated or fluorinated materials must be regarded as toxic. Nitrocompounds are absorbed through the skin and cause dermatitis. Dinitriles are toxic; they are absorbed through the skin.
Sensitivity- All insensitive, except some nitro or nitramino plasticiser.
Uses- Improved propellants.

2006-01-03T19:31:00.000-08:00

Pushpendra

Hybrid Rocket Motor

By Pushpendra singh

Typical Hybrid rocket motor:

INTRODUCTION:
In a hybrid rocket motor the oxidizer and fuel are stored in different physical states. In most cases, a solid fuel is stored in the combustion chamber into which a liquid or gaseous oxidiser is injected. A schematic diagram of a typical hybrid rocket engine is shown below. Figure: Hybrid rocket motor schematic Hybrid motors differ from solid and liquid rockets in that they combine a solid fuel with a liquid oxidiser - hence, they are said to be a "hybrid" of a solid and a liquid rocket. The hybrid fuel is contained within the combustion chamber, and the oxidiser is fed from an oxidiser tank. The oxidiser tank can be part of the same structure, or a separate component.

HYBRID FUELS:The fuel for a small hybrid rocket motor is generally a tube of combustible material (most frequently Polyethylene or Acrylic, although even cardboard is used in some cases!). The tube is known as the fuel grain. The hole down the center of the tube is called the fuel port. For a larger hybrid rocket motor, multi-port grain geometries are

common, where there will be several separate ports in the fuel grain, with oxidizer injected down each port. Common hybrid rocket fuels include:
· Polyethylene (Polyethene or PE) - - High Density Polyethylene (the most frequent form of Polyethylene used for hybrid rocket fuel) has a density of 960 kg / m3, and a heat conductivity of 0.23-0.29 W m-1 K-1
· Poly-Methyl Methacrylate (PMMA, Acrylic or Plexiglas) - [C6H10On]n - Poly-Methyl Methacrylate has a density of 1683 kg / m3, and a molecular weight of 114
· Poly-Vinyl Chloride (PVC) - PVC has a density of 1380 kg / m3, and a thermal conductivity of 0.16 W m-1 K-1
· Hydroxyl Terminated Poly-Butadiene (HTPB) - HTPB has a density of 930 kg / m3, and a thermal conductivity of 0.217 W m-1 K-1

HYBRID OXIDIZERS:
In High Power Rocketry and Amateur Rocketry, by far the most common oxidizer used with hybrid rocket motors is Nitrous Oxide (sometimes known somewhat incorrectly as NOx). Nitrous oxide (N2O) is an oxidizing liquefied gas and is clear and colourless. It has a slightly sweet odour. At room temperature, Nitrous Oxide is stable and inert. It is classified as a non-flammable gas. Nitrous Oxide supports combustion and can detonate at temperatures in excess of 650° C (1202° F). Nitrous Oxide is probably the easiest oxidiser to handle due to its benign nature compared to other oxidizers, as well as being relatively easy to acquire, due to there being no special restrictions on its sale or use, and due to it being self pressurising. Nitrous Oxide was the oxidiser used in the hybrid rocket motor, which propelled the Manned Spaceship. Nitrous Oxide was also used in the Environmental Aero sciences Hyper ion Sounding Rockets.
Common hybrid rocket oxidisers include:
Nitrous Oxide (N2O) - Nitrous Oxide, also known as Dinitrogen Monoxide, NOx, or laughing gas, has a boiling point of -89.5 degrees Celsius at 1 atm, and is normally maintained as a liquid at a pressure of 54 bar. Nitrous Oxide has a molecular weight of 44.0 and a density of 1222 kg / m3 at 20 degrees. The critical pressure and temperature of Nitrous Oxide is 7.27 MPa and 36.6 degrees Celsius.
-Gaseous Oxygen (GOx) -Hydrogen Peroxide (H2O2)
-Liquid Oxygen (O2) -Liquid Oxygen, also known as LOx, has a boiling point of -183 degrees Celsius at 1 atm. -Liquid Oxygen has a molecular weight of 32.0 and a density of 1265 kg / m3 at 20 degrees.
-Nitrogen Tetroxide (N2O4) - Nitrogen Tetroxide has a boiling point of 21.2 degrees Celsius at 1 atm. Nitrogen --Tetroxide has a molecular weight of 46.01 and a density of 1903 kg / m3 at 20 degrees.
-Nitric Acid (HNO3)

REGRESSION RATE:
In a hybrid rocket motor, liquid oxidizer is fed into the combustion chamber from the oxidizer tank, where it is ignited by an ignition source such as a pyrotechnic igniter. The fuel is then ignited and burned in the presence of the oxidizer, where it vaporizes, and burns along the length of the fuel grain. The rate at which the fuel burns, is called the regression rate, and is measured in meters per second (m/s).The combination of fuel burn rate and oxidizer flow rate is called the mass flux, and is measured in kilograms per meter-squared seconds (kg / m2 s). The oxidiser flow rate affects the rate of regression of the solid fuel, and enables the following equation for solid fuel regression rate to be derived:
r = aGnxm
Where;
r = fuel regression rate (m/s)G = propellant mass flux (kg / m2 s)x = length along the fuel grain port (m)a,n,m = regression rate constants The regression rate then, is dependent on the mass flux and the length along the fuel grain port.

OXIDISER TO FUEL (O/F) RATIO:
A hybrid motor differs fundamentally in terms of combustion behavior compared with solid and liquid rockets, in that the Oxidizer to Fuel ratio (O/F), varies along the length of the hybrid fuel grain, i.e., it has an axial dependency.In a liquid rocket, the injectors generally inject both the fuel and the oxidizer at one end of the combustion chamber thus there is no axial dependency.In a solid rocket motor, there is no injector head, and every particle is bound of fuel and oxidizer, thus ensuring the O/F remains pretty much constant.
COMBUSTION CHAMBER:
The combustion chamber in a hybrid rocket motor not only provides the location for propellant combustion, but also contains the whole fuel grain. The length of the combustion chamber is determined by the fuel grain configuration (e.g. a single port or multi-port fuel grain configuration). Also, the longer the combustion chamber, the more stable the combustion, since the propellant has more opportunity for even mixing.
FUEL GRAIN CONFIGURATION:
A single cylindrical port geometry for a hybrid fuel grain, provides more volumetric efficiency for any high power or amateur rocket, than does a multi-port geometry.The disadvantage of the single port configuration however, is that it generally requires long length to diameter ratios compared to a multi-port configuration. The multi-port configuration can be made quite short and compact, with length to diameter ratios of between 3-7.In general however, for high power or amateur rocketry, the single cylindrical port geometry configuration is probably the best choice for most hybrid propulsion applications.

INJECTION SYSTEM:
There are two methods of injection that can be used for injecting oxidizer into the combustion chamber of a hybrid rocket motor:
1. Direct injection into the fuel grain port.
2. Injection into a pre-combustion chamber.

For hybrid rocket motors on the high power and amateur rocketry level, where a single circular port geometry is most frequently used, direct injection of the oxidizer is the best approach, since there is no need to inject multiple oxidizer streams down multiple ports, and hence less requirement for a homogenized oxidizer stream from multiple injector nozzles.

Injection into a pre-combustion chamber is more useful for larger motors, or motors where a multi-port geometry is used for the fuel grain, since multiple injectors are more common, and even mixing of the oxidizer stream needs to be achieved before it is passed over the fuel grain.

CLASSIFICATION OF HYBRID ENGINES

1. Conventional Lithergolic Engines
2. Air Breathing Engines
1. Conventional Lithergolic Engines:
Conventional Lithergolic Engines can be of the normal type or inverse type. The liquid propellant is stored in a tank similar to the liquid fuel rocket. A feed system (turbo pump or pressurized gas) is used to supply the liquid oxidizer to the combustion chamber where the solid propellant is stored in the form of a block that contains either one or several openings. A whirling chamber is often used to ensure better mixing of combustion gases. The inverse lithergolic engine requires much bigger combustion due to O/F ratio requirements.

To improve the combustion efficiency the following methods are used;

(i.) Liquid injection into the reaction chamber.
(ii). Introduction of liquid through a porous fuel.
(iii) Accommodation of solid fuel in the form of individual pieces in the combustion chamber.
(iv) Counter current injection.

(i). Liquid injection into the reaction chamber:
As shown in the figure Combustion efficiency increases and helps in maintaining a constant O/F ratio when thrust control of the engine is employed.

(ii). Introduction of liquid through a porous fuel:
The oxidizer is injected through the porous holes of fuel, thus controlling the regression rate and giving larger thrust. The increasing hole size during combustion and grain manufacturing has not given encouraging results. Also this is restricted to non-hypergolic propellants.
(iii) Accommodation of solid fuel in the form of individual pieces in the combustion chamber.
Solid pieces in the form of spheres are accommodated in the combustion chamber as shown below, such an arrangement is used in gas generators. It was used in GIRD-09 the first hybrid rocket.

(iv)Counter current injection:
The solid fuel is made to impinge on the grain end, thus resulting in constant ablation surface and a long duration of combustion. It has a drawback of positioning the grain as combustion proceeds with time.

2. Air Breathing Engines:
In this system oxygen available in air is used as an oxidizer during the missile flight to reduce its lift-of-weight. Some varieties of the air breathing engines are as follows,
Ramjet with solid fuel:
It represents the possible way of simplifying the traditional ramjet engine by replacing the liquid fuel by a solid one. This latter is then consumed in the course of heterogeneous combustion, This type of layout can be regarded as a hybrid engine in which air is used in place of normal oxidizer (also called Hybrid Ram Rocket).
(b) Combined Ramjet-Lithergolic Engine: It can be adapted to a wide range of different missions. The hybrid engine is used during the launching phase and to accelerate the ramjet to the required flying speed. While operating within the atmosphere a part of the oxidizer can be replaced by air.
(c) Fuel Generator for Ramjet Engine: A hybrid generator for a ramjet engine produces a fuel rich gas mixture in a primary chamber that is formed by the combustion channel of the propellant grain. This fuel rich mixture is then subjected to further combustion with ram air in the secondary combustion chamber. Fuel with high metal content can be used and propellant mass flow rate can be adapted to mission requirement by regulating the gas generator.

Tribrid Rocket Engine:
Liquid-Solid-Liquid combination is some time known as TRIBRID system. Usually liquid H2 as third propellant not as a chemically reacting fuel but as an additional
working fluid capitalizing on its low molecular weight.

2006-01-03T19:23:00.000-08:00

Pushpendra
Alternate Energy Solution

By Pushpendra Singh

Abstract

Alternative sources of energy are considerably more attractive in many ways than nuclear power. These sources include solar power, wind, wave and geothermal energy. Energy efficiency is also critically important in delivering an economically and environmentally acceptable but sustainable source of energy for the 21st century. An alternative, or complementary, approach is to reward cleaner energy supply systems by paying a subsidy to balance the environmental costs of burning fossil fuels. The environmental consequences of energy production have led many nations in the world to impose stricter guidelines on the production and consumption of energy. Further, the search for new sources of energy and more efficient means of employing energy has accelerated. Researchers and engineers have been looking at alternative energy sources that do not tax the environment or deplete natural fuel reserves. Future energy development faces great challenges due to an increasing world population, demands for higher standards of living.

TABLE OF CONTENT
1. Introduction
2. Alternative Energy Sources
2.1 Solar Energy
2.2 Geothermal Energy
2.3 Wind Energy
2.4 Ocean Energy
2.5 Biomass Energy
2.6 Nuclear Energy
2.7 Hydrogen
2.8 Fuel Cell
2.9 Hydropower
2.10 Energy from fossil fuels
3. Energy Storage
4. Advantages and Disadvantages of Alternative Energy
5. Conclusion
6. References

2 Alternative Energy Sources
An Alternative Energy Source is one not commonly associated with a particular use. For example, wind power in the form of windmills has been used for hundreds of years to grind grain making it a conventional source of energy. However, using wind power to generate electricity is relatively new, and is therefore considered an alternative energy source when used for this application Examples of renewable primary energy sources include geothermal, hydropower and solar. Nonrenewable primary energy sources include natural gas, oil, coal and uranium. Secondary energy sources are products of human technology, the most common of these energy sources is electricity.
Alternative Energy Sources
Nonrenewable
Renewable

Oil sands, heavy oil
Wood/other biomass

Natural gas
Hydro-electric power

Coal
Solar energy

Shale oil
Wind energy

Gas hydrates
Wave energy

Nuclear fission
Tidal power

Geothermal1
Fusion

Ocean thermal energy conversion

SOLAR ENERGY

The sun's energy is vital to life on Earth. It determines the Earth's surface temperature and supplies virtually all the energy that drives natural global systems and cycles. Although some other stars are enormous sources of energy in the form of X-rays and radio signals, our sun releases 95% of its energy as visible light. Yet, visible light represents only a fraction of the total radiation spectrum; infrared and ultraviolet rays are also significant parts of the solar spectrum.

All renewable energies derive from the sun. There is solar, of course, but also hydrothermal, biomass, and wind. They all get their energy from the sun. The amount of sun that reaches the earth’s surface is enormous. Two weeks of sunlight over the whole earth is equal to all of the energy stored in coal, oil and natural gas. The problem is to harness it.
Each second, the sun releases an enormous amount of radiant energy in to the solar system. The Earth receives a tiny fraction of this energy; still, an average of 1367 watts (W) reaches each square meter (m2) of the outer edge of the Earth's atmosphere. The atmosphere absorbs and reflects some of this radiation, including most X-rays and ultraviolet rays. Still, the amount of sunshine energy that hits the surface of the Earth every minute is greater than the total amount of energy that the world's human population consumes. The Earth's atmosphere and cloud cover absorb, reflect, and scatter some of the solar radiation entering the atmosphere.
Solar cells

These convert solar power directly into electricity. Clean, but very expensive and polluting in the production of them. The most important parts of a solar cell are the semiconductor layers, because this is where the electron current is created. There are a number of different materials suitable for making these semi conducting layers, and each has benefits and drawbacks. Unfortunately, there is no one ideal material for all types of cells and applications. In addition to the semi conducting materials, solar cells consist of a top metallic grid or other electrical contact to collect electrons from the semiconductor and transfer them to the external load, and a back contact layer to complete the electrical circuit. Then, on top of the complete cell is typically a glass cover or other type of transparent encapsulate to seal the cell and keep weather out, and an anti reflective coating to keep the cell from reflecting the light back away from the cell.

The "photovoltaic effect" is the basic physical process through which a PVcell converts sunlight into electricity. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum (see "Light and the Sun" for more about that). When photons strike a PVcell, they may be reflected or absorbed, or they may pass right through.Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit. By leaving this position, the electron causes a "hole" to form. Special electrical properties of the PV cell-a built-in electric field provide the voltage needed to drive.
Solar cells are typically combined into modules that hold about 40 cells; about 10 of these modules are mounted in PV arrays that can measure up to several meters on a side. These flat-plate PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day. About 10 to 20 PV arrays can provide enough power for a household; for large electric utility or industrial applications, hundreds of arrays can be interconnected to form a single, large PV system. By connecting cells together to form a solar panel we can do even more work. The typical individual silicon solar cell has the potential of generating about half a volt, but by wiring them in series or end to end you can increase the voltage. In other words, 36 individual cells will produce about 18 volts. The size of the individual cell is what determines the amount of current of amps that a solar panel can produce.
Solar energy power plants
Many power plants today use fossil fuels as a heat source to boil water. The steam from the boiling water rotates a large turbine, which activates a generator that produces electricity. However, a new generation of power plants, with concentrating solar power systems, uses the sun as a heat source. There are three main types of concentrating solar power systems: parabolic-trough, dish/engine, and power tower.
Parabolic-trough systems concentrate the sun's energy through long rectangular, curved (U-shaped) mirrors. The mirrors are tilted toward the sun, focusing sunlight on a pipe that runs down the center of the trough. This heats the oil flowing through the pipe. The hot oil then is used to boil water in a conventional steam generator to produce electricity.
A dish/engine system uses a mirrored dish (similar to a very large satellite dish). The dish-shaped surface collects and concentrates the sun's heat onto a receiver, which absorbs the heat and transfers it to fluid within the engine. The heat causes the fluid to expand against a piston or turbine to produce mechanical power. The mechanical power is then used to run a generator or alternator to produce electricity.
A power tower system uses a large field of mirrors to concentrate sunlight onto the top of a tower, where a receiver sits. This heats molten salt flowing through the receiver. Then, the salt's heat is used to generate electricity through a conventional steam generator. Molten salt retains heat efficiently, so it can be stored for days before being converted into electricity. That means electricity can be produced on cloudy days or even several hours after sunset.

California has an abundance of accessible solar energy resources. In terms of potential Electricity capacity, sunlight striking California could produce about 30,000 megawatts (MW) for central generation to the electricity grid and about 35,000 MW for distributed generation. For comparison, the entire California electric generation demand is currently about 65,000 MW. As of 1998, however, solar energy produces only roughly about 355 MW of electricity (about 0.3 percent of the total state electricity generation).
Solar Hot Water
The shallow water of a lake is usually warmer than the deep water. That's because the sunlight can heat the lake bottom in the shallow areas, which in turn, heats the water. It's nature's way of solar water heating.
Most solar water heating systems for buildings have two main parts: a solar collector and a storage tank. The most common collector is called a flat-plate collector. Mounted on the roof, it consists of a thin, flat, rectangular box with a transparent cover that faces the sun. Small tubes run through the box and carry the fluid — either water or other fluid, such as an antifreeze solution — to be heated. The tubes are attached to an absorber plate, which is painted black to absorb the heat. As heat builds up in the collector, it heats the fluid passing through the tubes.
The storage tank then holds the hot liquid. It can be just a modified water heater, but it is usually larger and very well-insulated. Systems that use fluids other than water usually heat the water by passing it through a coil of tubing in the tank, which is full of hot fluid.
Solar Process Heat
These technologies include ventilation air preheating, solar process heating and solar cooling.
In cold climates, heating this air can use large amounts of energy. A solar ventilation system can preheat the air, saving both energy and money. This type of system typically uses a transpired collector, which consists of a thin, black metal panel mounted on a south-facing wall to absorb the sun's heat. Air passes through the many small holes in the panel. A space behind the perforated wall allows the air streams from the holes to mix together. The heated air is then sucked out from the top of the space into the ventilation system.
Solar process heating systems are designed to provide large quantities of hot water or space heating for nonresidential buildings. A typical system includes solar collectors that work along with a pump, a heat exchanger, and/or one or more large storage tanks. The two main types of solar collectors used—an evacuated-tube collector and a parabolic-trough collector—can operate at high temperatures with high efficiency. An evacuated-tube collector is a shallow box full of many glass, double-walled tubes and reflectors to heat the fluid inside the tubes. A vacuum between the two walls insulates the inner tube, holding in the heat. Parabolic troughs are long, rectangular, curved (U-shaped) mirrors tilted to focus sunlight on a tube, which runs down the center of the trough. This heats the fluid within the tube.
The heat from a solar collector can also be used to cool a building. It may seem impossible to use heat to cool a building, but it makes more sense if you just think of the solar heat as an energy source. Your familiar home air conditioner uses an energy source, electricity, to create cool air. Solar absorption coolers use a similar approach, combined with some very complex chemistry tricks, to create cool air from solar energy. Solar energy can also be used with evaporative coolers (also called "swamp coolers") to extend their usefulness to more humid climates, using another chemistry trick called desiccant cooling
Solar ponds
One way to tap solar energy is through the use of solar ponds. Solar ponds are large-scale energy collectors with integral heat storage for supplying thermal energy. It can be use for various applications, such as process heating, water desalination, refrigeration, drying and power generation.
The solar pond works on a very simple principle. It is well-known that water or air is heated they become lighter and rise upward e.g. a hot air balloon. Similarly, in an ordinary pond, the sun’s rays heat the water and the heated water from within the pond rises and reaches the top but loses the heat into the atmosphere. The net result is that the pond water remains at the atmospheric temperature. The solar pond restricts this tendency by dissolving salt in the bottom layer of the pond making it too heavy to rise.
A solar pond has three zones. The top zone is the surface zone, or UCZ (Upper Convective Zone), which is at atmospheric temperature and has little salt content. The bottom zone is very hot, 70°– 85° C, and is very salty. It is this zone that collects and stores solar energy in the form of heat, and is, therefore, known as the storage zone or LCZ (Lower Convective Zone). Separating these two zones is the important gradient zone or NCZ (Non-Convective Zone). Here the salt content increases as depth increases, thereby creating a salinity or density gradient. If we consider a particular layer in this zone, water of that layer cannot rise, as the layer of water above has less salt content and is, therefore, lighter. Similarly, the water from this layer cannot fall as the water layer below has a higher salt content and is, therefore, heavier. This gradient zone acts as a transparent insulator permitting sunlight to reach the bottom zone but also entrapping it there. The trapped (solar) energy is then withdrawn from the pond in the form of hot brine from the storage zone.
Geothermal Energy
Geothermal energy is an alternative energy source, although it is not resourceful enough to replace more than a minor amount of the future's energy needs. Geothermal energy is obtained from the internal heat of the planet and can be used to generate steam to run a steam turbine. This in turn generates electricity, which is a very useful form of energy. These resources can be classified as low temperature (less than 90°C or 194°F), moderate
temperature (90°C - 150°C or 194- 302°F), and high temperature (greater than 150°C or
302°F). The uses to which these resources are applied are also influenced by temperature.
The highest temperature resources are generally used only for electric power generation.

Hydrothermal convection system

A permeable layer in which hot water circulates. If the temperature is high enough, we have a vapor-dominated system, where mixed water and steam exist. As the mixture is brought to higher levels, the water flashes to superheated steam, which can drive steam turbines. The used water has to be pumped back down into the ground, as it is hot and often contains toxic materials.
The second type is a hot-water system. Here the temperature is not high enough to have
only steam, and the water and steam must be separated. Plus, the water has to be pumped
back into the ground.
Hot igneous systems

These consist of hot rock that is not in contact with groundwater. Most igneous intrusions are of this type. Temperature can be well over 600°C. They have the highest amount of energy stored in them, but without the water to circulate to the surface and create electricity, they don’t do us any good in their present form. They can be drilled and then explosives at depth can create fracturing. Water can then be injected and recovered as steam. Injected water was heated to 150°C and pumped to the surface.
Moderate T ground waters
Direct use, as the name implies, involves using the heat in the water directly (without a
heat pump or power plant) for such things as heating of buildings, industrial processes,
greenhouses, aquaculture (growing of fish) and resorts. Direct use projects generally use
resource temperatures between 38°C (100°F) to 149°C (300°F). Current U.S. installed
capacity of direct use systems totals 470 MW or enough to heat 40,000 average-sized
houses.
Low T groundwater systems
We’re back to the discussion of low temperature energy needs. Most of our energy needs
is low T. Normal water is only about 13°C. This isn’t hot, but it is hotter than on a
cold winter day. So you could use the water to heat your home in the winter. And it’s a lot colder than a hot summer day. So in summer it could be used to cool a house. It is economically feasible, but the payoff is about 8 years. Ground-source heat pumps use the earth or groundwater as a heat source in winter and a heat sink in summer. Using resource temperatures of 4°C (40°F) to 38°C (100°F), the heat pump, a device which moves heat from one place to another, transfers heat from the soil to the house in winter and from the house to the soil in summer.
How do Geothermal-Energy Systems Work?
The radius of the Earth is about 4000 miles, with an internal core temperature of about 4000 degrees Celsius at the center. The mantle surrounds the outer core and is only about 45 miles below the surface, depending on location. The temperature at the mantle-surface crust boundary is about 375 degrees, Celsius. Drilling down only three miles we can reach temperatures of 100 degrees, Celsius, which is enough to boil water to run a steam-powered electric power plant. Drilling three miles through the earth is possible, but not easy, so luckily there are easier routes to access this power source, known as geothermal hotspots.
Geothermal hotspots are volcanic features which are found all around the world. Basically a hotspot is an area of reduced thickness in the mantle which transmits excess internal heat from the interior of the earth to the outer crust. These hotspots are well known for their unique effects on the surface, such as the volcanic islands of Hawaii, the mineral deposits and geysers in Yellowstone National Park, or the hot springs in Iceland. These geothermal hotspots can easily be used to generate electricity
Some systems pump hot-water into permeable sedimentary hotspots found underground and then use the steam to generate electricity. Then the used steam is condensed and sent back down to the permeable sedimentary stream. Another system utilizes volcanic magma which is still partly molten at around 650 degrees, Celsius, to boil water which would generate electricity. Also there is a system which uses hot dry rock, which is just hardened magma, but still is extremely hot. To recover this heat from these rocks, a system is used which circulates water through the rock and transfers the heat up to a steam generator. The first system listed here is not as useful as other methods because of the acidic nature of the fluids found under the ground. These acidities require a lot of maintenance and upkeep on the equipment, and this cost reduces the economic effectiveness of the system. Therefore, geothermal energy systems are more inefficient than other alternative energy sources because of the costs required in upkeep and the shortage of potential sites
Geothermal Electricity Production
Geothermal power plants, however, use steam produced from reservoirs of hot water found a couple of miles or more below the Earth's surface. There are three types of geothermal power plants: dry steam, flash steam, and binary cycle.
Dry steam power plants draw from underground resources of steam. The steam is piped directly from underground wells to the power plant, where it is directed into a turbine/generator unit. There are only two known underground resources of steam in the United States: The Geysers in northern California and Yellowstone National Park in Wyoming, where there's a well-known geyser called Old Faithful. Since Yellowstone is protected from development, the only dry steam plants in the country are at The Geysers.
Flash steam power plants are the most common. They use geothermal reservoirs of water with temperatures greater than 360°F (182°C). This very hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water boils into steam. The steam is then separated from the water and used to power a turbine/generator. Any leftover water and condensed steam are injected back into the reservoir, making this a sustainable resource.
Binary cycle power plants operate on water at lower temperatures of about 225°—360°F (107°—182°C). These plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point. The working fluid is vaporized in a heat exchanger and used to turn a turbine. The water is then injected back into the ground to be reheated. The water and the working fluid are kept separated during the whole process, so there are little or no air emissions.
Small-scale geothermal power plants (under 5 megawatts) have the potential for widespread application in rural areas, possibly even as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity delivery system.
Geothermal Heat Pumps
The shallow ground, the upper 10 feet of the Earth, maintains a nearly constant temperature between 50° and 60°F (10°–16°C). Like a cave, this ground temperature is warmer than the air above it in the winter and cooler than the air in the summer. Geothermal heat pumps take advantage of this resource to heat and cool buildings.
Geothermal heat pump systems consist of basically three parts: the ground heat exchanger, the heat pump unit, and the air delivery system (ductwork). The heat exchanger is basically a system of pipes called a loop, which is buried in the shallow ground near the building. A fluid (usually water or a mixture of water and antifreeze) circulates through the pipes to absorb or relinquish heat within the ground. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed.
Wind Energy
Wind is air in motion. It is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s radiation unevenly. When the sun is shining during the day, the air over landmasses heats more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air over water moves in to take its place, creating local winds. At night, the winds are reversed because the air cools more rapidly over land than over water. Similarly, the large atmospheric winds that circle the earth are created because the surface air near the equator is warmed more by the sun than the air over the North and South Poles. Wind is called a renewable energy source because wind will continually be produced as long as the sun shines on the earth. Today, wind energy is mainly used to generate electricity.
Types of Windmills
Aeration Windmill
This windmill will aerate a pond or pump water out of your pond or river to water your animals or garden. This windmill will pump out of a shallow (up to 15m) well.

Aermotor Windmill
They have been manufactured since 1888 and are the old standard of windmills. They will pump out of a well but will not aerate a pond or pump water out of the pond or river.
These styles of windmills will not produce electricity! Many people think you can buy a regular windmill to run your air conditioner, freezer, washer, dryer, etc. and you can not. This is all 240 volts A.C.
Wind Turbine
The wind turbine, also called a windmill, is a means of harnessing the kinetic energy of the wind and converting it into electrical energy. This is accomplished by turning blades called aerofoil, which drive a shaft, which drive a motor (turbine) and are e connected to a generator. the Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor. wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.
A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than
Wind Mill Efficiency
Windmills are turbines. The two names can be used synonymously. Turbines are a means of harnessing the fluid's power (the wind) by converting the kinetic energy of the fluid (the wind) into mechanical power (the rotating shaft) When the shaft of a w windmill is hooked up to a generator, electrical energy can be formed. The generator can be used to produce either DC or AC current. Generators that produce DC can be connected to batteries, an inverter to produce AC, or to power DC loads.An important equation used to find the wind power density, how much power is available per square meter is the equation ------------------ P = .5 pu³
where P is the wind power density in W/m2, p is the density of the air, and u³ is the cube of the wind velocity.
Windmills can not operate at 100% efficiency because the structure itself impedes the flow of the wind. The structure also exerts back pressure on the turbine blades as they act like an air foil (a wing on an airplane). In most all cases, the efficiency of the wind turbine depends on the actual wind speed. The maximum efficiency of 44% is reached in a 9 m/s wind (18 mph) and falls sharply at higher wind speeds. For a reasonable range of winds, the average efficiency is around 20%.
Ocean Energy
The ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves.
Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.
Ocean thermal energy
Ocean thermal energy is used for many applications, including electricity generation. There are three types of electricity conversion systems: closed-cycle, open-cycle, and hybrid. Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a low-boiling point, such as ammonia. The vapor expands and turns a turbine. The turbine then activates a generator to produce electricity. Open-cycle systems actually boil the seawater by operating at low pressures. This produces steam that passes through a turbine/generator. And hybrid systems combine both closed-cycle and open-cycle systems.
Ocean mechanical energy
Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent sources of energy, while ocean thermal energy is fairly constant. Also, unlike thermal energy, the electricity conversion of both tidal and wave energy usually involves mechanical devices.
A barrage (dam) is typically used to convert tidal energy into electricity by forcing the water through turbines, activating a generator. For wave energy conversion, there are three basic systems: channel systems that funnel the waves into reservoirs; float systems that drive hydraulic pumps; and oscillating water column systems that use the waves to compress air within a container. The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water, or air, which then drives a turbine/generator.
Wave Energy
Waves, particularly those of large amplitude, contain large amounts of energy. Wave energy is in effect a stored and concentrated form of solar energy, since the winds that produce waves are caused by pressure differences in the atmosphere arising from solar heating. The total power of waves breaking on the world's coastlines is estimated at 2 to 3 million megawatts. In favorable locations, wave energy density can average 65 megawatts per mile of coastline.
Several ways of classifying wave energy devices have been proposed, based on the energy extraction method, the size of the device, etc. The method adopted here uses the location of the device with respect to the shoreline, i.e. shoreline devices, near shore devices and offshore devices.
Shoreline Devices
Shoreline devices have the advantage of relatively easier maintenance and installation and do not require deep water moorings and long underwater electrical cables. The less energetic wave climate at the shoreline can be partly compensated by the concentration of wave energy that occurs naturally at some locations by refraction and/or diffraction. The three major classes of shoreline devices are the oscillating water column (OWC), the convergent channel (TAPCHAN) and the Pendulor, as shown below.
The OWC comprises a partly submerged concrete or steel structure, which has an opening to the sea below the water line, thereby enclosing a column of air above a column of water. As waves impinge on the device, they cause the water column to rise and fall, which alternately compresses and depressurizes the air column. This air is allowed to flow to and from the atmosphere through a turbine which drives an electric generator. Both conventional (i.e. unidirectional) and self- rectifying air turbines have been proposed. The axial-flow Wells turbine, invented in the 1970s, is the best known turbine for this kind of application and has the advantage of not requiring rectifying air valves. A number of OWC devices have been installed worldwide, with several of them being built into a breakwater to lower overall construction costs.
The Tap Chan comprises a gradually narrowing channel with wall heights typically 3 to 5 m above mean water level. The waves enter the wide end of the channel and, as they propagate down the narrowing channel, the wave height is amplified until the wave crests spill over the walls to a reservoir which provides a stable water supply to a conventional low head turbine. The requirements of low tidal range and suitable shoreline limit the world-wide replicability of this device.
The Pendulor device consists of a rectangular box, which is open to the sea at one end. A pendulum flap is hinged over this opening, so that the action of the waves causes it to swing back and forth. This motion is then used to power a hydraulic pump and generator. World-wide, only small devices have been deployed.
Near shore Devices
Near shore devices are situated in shallow waters (typically 10 to 25 m water depth). Again the OWC is the main type of device, with several designs having been deployed world-wide.
Offshore Devices
Offshore devices are situated in deeper water, with typical depths of more than 40 m. Several different designs having been deployed world-wide, with many more still at the design stage. Some of the representative devices that have been deployed are shown below:
The Swedish Hose pump has been under development since 1980. It consists of a specially reinforced electrometric hose (whose internal volume decreases as it stretches), connected to a float which rides the waves. The rise and fall of the float stretches and relaxes the hose thereby pressurizing sea water, which is fed (along with the output from other Hose pumps) through a non-return valve to a central turbine and generator unit.
The McCabe Wave Pump consists of three rectangular steel pontoons which move relative to each other in the waves. The key aspect of the scheme is the damper plate attached to the central pontoon, which ensures that it stays still as the fore and aft pontoons move relatively to the central pontoon by pitching about the hinges. Energy is extracted from the rotation about the hinge points by linear hydraulic pumps mounted between the central and two outer pontoons near the hinges. The device was developed to supply potable water (by reverse osmosis) but can also be used to generate electricity (via a hydraulic motor and generator).
The floating wave power vessel is a steel platform containing a sloping ramp, which gathers incoming waves into a raised internal basin. The water flows from this basin back into the sea through low-head turbines. In these respects it is similar to an offshore Tap Chan but the device is not sensitive to tidal range.
The Danish Wave Power float-pump device uses a float which is attached to a seabed mounted piston pump; the rise and fall motion of the float causes the pump to operate driving a turbine and generator mounted on the pump. The flow of water through the turbine is maintained as uni-directional through the incorporation of a non-return valve.
Biomass Energy
The biomass energy or " bioenergy " the energy from plants and plant-derived materials—since people began burning wood to cook food and keep warm. Wood is still the largest biomass energy resource today, but other sources of biomass can also be used. These include food crops, grassy and woody plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes. Even the fumes from landfills (which are methane, a natural gas) can be used as a biomass energy source

Biomass can be used for fuels and power production that would otherwise be made from fossil fuels.
Biofuels
Biomass can be converted directly into liquid fuels, called "biofuels," to help meet transportation fuel needs. The two most common types of biofuels are ethanol and biodiesel.
Ethanol is an alcohol-based alternative fuel produced by fermenting and distilling starch crops that have been converted into simple sugars. Feedstocks for this fuel include corn, barley, and wheat. Ethanol can also be produced from "cellulosic biomass" such as trees and grasses and is called bioethanol. Ethanol is most commonly used to increase octane and improve the emissions quality of gasoline . Ethanol can be blended with gasoline to create E85, a blend of 85% ethanol and 15% gasoline.
Biodiesel is made by combining alcohol (usually methanol) with vegetable oil, animal fat, or recycled cooking grease. It can be used as an additive (typically 20%) to reduce vehicle emissions or in its pure form as a renewable alternative fuel for diesel engines.
Biopower
Biopower, or biomass power, is the use of biomass to generate electricity. Biopower system technologies include direct-firing, cofiring, gasification, pyrolysis, and anaerobic digestion.
Most biopower plants use direct-fired systems. They burn bioenergy feedstocks directly to produce steam. This steam drives a turbine, which turns a generator that converts the power into electricity. Paper mills, the largest current producers of biomass power, generate electricity or process heat as part of the process for recovering pulping chemicals.
Co-firing refers to mixing biomass with fossil fuels in conventional power plants. Coal-fired power plants can use co-firing systems to significantly reduce emissions, especially sulfur dioxide emissions. Gasification systems use high temperatures and an oxygen-starved environment to convert biomass into synthesis gas, a mixture of hydrogen and carbon monoxide. The synthesis gas, or "syngas," can then be chemically converted into other fuels or products, burned in a conventional boiler, or used instead of natural gas in a gas turbine.
Biomass pyrolysis refers to a process where biomass is exposed to high temperatures in the absence of air, causing the biomass to decompose. The end product of pyrolysis is a mixture of solids (char), liquids (oxygenated oils), and gases (methane, carbon monoxide, and carbon dioxide).
Anaerobic digestion is a process by which organic matter is decomposed by bacteria in the absence of oxygen to produce methane and other byproducts. The primary energy product is a low to medium calorific gas, normally consisting of 50 to 60 percent methane.

Nuclear Energy
Nuclear processes can release a million times the energy of a chemical process. For this reason, mankind has tried to make use of this energy source for both military purposes and for power production. There are two kinds of ways that nuclear energy has been used: fission and fusion.
Nuclear Fusion
Fusion means joining smaller nuclei (the plural of nucleus) to make a larger nucleus. The sun uses nuclear fusion of hydrogen atoms into helium atoms. This gives off heat and light and other radiation. The most suitable reaction occurs between the nuclei of the two heavy forms (isotopes) of Hydrogen - Deuterium (D) and Tritium (T); eventually reactions involving just Deuterium or Deuterium and Helium (3He) may be used.
Reaction : 2H + 3H --> 4He + n.+ energy
Scientists have been working on controlling nuclear fusion for a long time, trying to make a fusion reactor to produce electricity. But they have been having trouble learning how to control the reaction in a contained space. What's better about nuclear fusion is that it creates less radioactive material than fission, and its supply of fuel can last longer than the sun.
Nuclear Fission
When a nucleus fissions, it splits into several smaller fragments. These fragments, or fission proThe sum of the masses of these fragments is less than the original mass. This 'missing' mass (about 0.1 percent of the original mass) has been converted into energy according to Einstein's equation.
Fission can occur when a nucleus of a heavy atom captures a neutron, or it can happen spontaneously.
Reaction : U235 + n -----à fission product + 2 or 3 n + 200 MeV
1 MeV (million electron volts) = 1.609 x 10 -13 joules
the natural uranium, only 0.7% is uranium 235. This meant that a large amount of uranium was needed to obtain the necessary quantities of uranium 235. plutonium 239 would have a high fission probability. However, plutonium 239 is not a naturally occurring element and would have to be made.
Nuclear Power Plants
A nuclear power plant uses uranium as a "fuel." Uranium is an element that is dug out of the ground many places around the world. It is processed into tiny pellets that are loaded into very long rods that are put into the power plant's reactor. The controlled fission occurs in core. This water from around the nuclear core is sent to another section of the power plant. Here, in the heat exchanger, it heats another set of pipes filled with water to make steam. The steam in this second set of pipes turns a turbine to generate electricity.
A typical nuclear power plant
Types of Nuclear Power Plants
Pressurized Water Reactor (PWR)
This is the most common type, with over 230 in use for power generation and a further several hundred in naval propulsion. The design originated as a submarine power plant. It uses ordinary water as both coolant and moderator. The design is distinguished by having a primary cooling circuit which flows through the core of the reactor under very high pressure, and a secondary circuit in which steam is generated to drive the turbine. Water in the reactor core reaches about 325ƒC, hence it must be kept under about 150 times atmospheric pressure to prevent it boiling. Pressure is maintained by steam in a pressurizer (see diagram). In the primary cooling circuit the water is also the moderator, and if any of it turned to steam the fission reaction would slow down.
A PWR has fuel assemblies of 200-300 rods each, arranged vertically in the core, and a large reactor would have about 150-250 fuel assemblies with 80-100 tonnes of uranium
Boiling Water Reactor (BWR)
This design (diagram next page) has many similarities to the PWR, except that there is only a single circuit in which the water is at lower pressure (about 75 times atmospheric pressure) so that it boils in the core at about 285ƒC. The steam passes through drier plates (steam separators) above the core and then directly to the turbines, which are thus part of the reactor circuit. BWR fuel assembly comprises 90-100 fuel rods, and there are up to 750 assemblies in a reactor core, holding up to 140 tonnes of uranium.
Pressurized Heavy Water Reactor (PHWR or CANDU)
It uses natural uranium (0.7% U-235) oxide as fuel, hence needs a more efficient moderator, in this case heavy water (D2O) .The moderator is in a large tank called a calandria, penetrated by several hundred horizontal pressure tubes which form channels for the fuel, cooled by a flow of heavy water under high pressure in the primary cooling circuit, reaching 290ƒC. As in the PWR, the primary coolant generates steam in a secondary circuit to drive the turbines.
Advanced Gas-cooled Reactor (AGR)
These are the second generation of British gas-cooled reactors, using graphite moderator and carbon dioxide as coolant. The fuel is uranium oxide pellets, enriched to 2.5-3.5%, in stainless steel tubes. The carbon dioxide circulates through the core, reaching 650ƒC and then past steam generator tubes outside it, but still inside the concrete and steel pressure vessel. Control rods penetrate the moderator and a secondary shutdown system involves injecting nitrogen to the coolant.
Light water graphite-moderated reactor
This is a Soviet design, developed from plutonium production reactors. It employs long (7 meter) vertical pressure tubes running through graphite moderator, and is cooled by water, which is allowed to boil in the core at 290°C, much as in a BWR. Fuel is low-enriched uranium oxide made up into fuel assemblies 3.5 meters long. With moderation largely due to the fixed graphite, excess boiling simply reduces the cooling and neutron absorption without inhibiting the fission reaction, and a positive feedback problem can arise
Thorium as a nuclear fuel
Thorium, as well as uranium, can be used as a nuclear fuel. Although not fissile itself, thorium-232 (Th-232) will absorb slow neutrons to produce uranium-233 (U-233), which is fissile. The use of thorium-based fuel cycles has been studied for about 30 years, but on a much smaller scale than uranium or uranium/plutonium cycles. Much experience has been gained in thorium-based fuel in power reactors around the world, some using high-enriched uranium (HEU) as the main fuel. In India, both Kakrapar-1 and -2 units are loaded with 500 kg of thorium fuel in order to improve their operation when newly-started. Many Concepts for advanced reactors based on thorium-fuel cycles example Light Water Reactors - With fuel based on plutonium oxide (PuO2), thorium oxide (ThO2) and/or uranium oxide (UO2) particles arranged in fuel rods.
Hydrogen
Hydrogen is the third most abundant element on the earth's surface, where it is found primarily in water (H²O) and organic compounds. It is generally produced from hydrocarbons or water; and when burned as a fuel, or converted to electricity, it joins with oxygen to again form water. Most hydrogen production today is by steam reforming natural gas. Fill vehicle fuel tanks with it instead of gasoline. Pipe it to homes for heating and cooking instead of natural gas and to generate electricity onsite instead of sending electricity through transmission lines. On a weight basis, hydrogen has nearly three times the energy content of gasoline (120 MJ/kg for hydrogen versus 44 MJ/kg for gasoline). However, on a volume basis the situation is reversed (8 MJ/liter for liquid hydrogen versus 32 MJ/liter for gasoline). On-board hydrogen storage in the range of 5-13 kg H2 is required to encompass the full platform of light-duty vehicles.
Hydrogen Properties
Hydrogen is a colorless, odorless, tasteless, and nonpoisonous gas under normal conditions on Earth. It typically exists as a diatomic molecule, meaning each molecule has two atoms of hydrogen ,this is why pure hydrogen is commonly expressed as "H2". Hydrogen is the most abundant element in the universe, accounting for 90 percent of the universe by weight. However, it is not commonly found in its pure form, since it readily combines with other elements. It is also the lightest element, having a density of 0.08988 grams per liter at standard pressure.
Hydrogen has several important chemical properties that affect its use as a fuel:
It readily combines with oxygen to form water, which is absolutely necessary for life on this planet.
It has a high energy content per weight (nearly 3 times as much as gasoline), but the energy density per volume is quite low at standard temperature and pressure. Volumetric energy density can be increased by storing the hydrogen under increased pressure or storing it at extremely low temperatures as a liquid. Hydrogen can also be adsorbed into metal hydrides.
Hydrogen is highly flammable; it only takes a small amount of energy to ignite it and make it burn. It also has a wide flammability range, meaning it can burn when it makes up 4 to 74 percent of the air by volume.
Hydrogen burns with a pale-blue, almost-invisible flame, making hydrogen fires difficult to see.
The combustion of hydrogen does not produce carbon dioxide (CO2), particulate, or sulfur emissions. It can produce nitrous oxide (NOX) emissions under some conditions.
Hydrogen can be produced from renewable resources, such as by reforming ethanol (this process emits some carbon dioxide) and by the electrolysis of water (electrolysis is very expensive).
Hydrogen Production
Hydrogen can be produced using a variety of domestic energy resources - fossil fuels, such as coal and natural gas, with carbon capture and sequestration; renewable, such as biomass, and renewable energy technologies, including solar, wind, geothermal, and hydropower; and nuclear power. Specific technologies and processes are described below.
Thermochemical Processes
Steam methane reforming: In this process, high-temperature steam is used to extract hydrogen from a methane source such as natural gas. This is the most common method of producing hydrogen; about 95 percent of the hydrogen we use today in the United States is produced using this process.
Partial oxidation: Scientists are exploring a process that produces hydrogen by simultaneously separating oxygen from air and partially oxidizing methane.
Other thermal processes: Other processes include (1) splitting water using heat from a solar concentrator, and (2) gasifying or burning biomass (i.e., biological material, such as plants or agricultural waste) to generate a bio-oil or gas, which is then reformed to produce hydrogen.
Electrolytic Processes
Electrolysis: In electrolysis, electricity is used to separate water (H2O) into hydrogen and oxygen. Current electrolysis systems are very energy intensive. The challenge is to develop low cost and more energy efficient electrolysis technologies.
Photolytic Processes
Photolytic methods: In photolysis, sunlight is used to split water. Two photolytic processes are being explored: (1) photobiological methods, in which microbes, when exposed to sunlight, split water to produce hydrogen, and (2) photoelectrolysis, in which semi-conductors, when exposed to sunlight and submersed in water, generate enough electricity to produce hydrogen by splitting the water.
Hydrogen Storage
Finding a cost-effective method of storing hydrogen on a vehicle is a challenge. While hydrogen contains more energy per weight than any other energy carrier, it contains much less energy by volume. This makes it difficult to store a large amount of hydrogen in a small space, like in a gas tank of a car.
Technologies
High-pressure tanks: Hydrogen gas can be compressed and stored in storage tanks at high pressure. These tanks must be strong, durable, light-weight, and compact, as well as cost competitive.
Liquid hydrogen: Hydrogen can be stored as a liquid. In this form, more hydrogen can be stored per volume, but it must be kept at cold temperatures (about -253°C).
Materials-based storage of hydrogen: Hydrogen can be stored within solid materials, such as powders, or liquids. Technologies under study include —
Reversible Metal Hydrides: Hydrogen combines chemically with some metals, which can result in higher storage capacity compared to high-pressure gas or liquid. These materials can be "re-filled" with hydrogen while on the vehicle.
Carbon Materials and High Surface Area Sorbents: Carbon nanotubes are examples of materials that reversibly store hydrogen. Other sorbents may be able to store hydrogen at room temperature.
Chemical Hydride Materials: Materials are under study that release hydrogen by a chemical process on the vehicle. These materials are then removed and "regenerated" off-board, either at the fueling station or at a central processing plant.
Hydrogen Fuel Cell
The fuel cell works by injecting molecular hydrogen (H2) molecules into the anode. The hydrogen molecules react with the catalyst. The catalyst is usually a thin coat of powdered platinum on carbon paper. This breaks up the hydrogen into a proton and an electron. The proton goes across the electrolyte, (remember, it only accepts protons) while the electron is fed through the circuit and goes to work, whether it be powering our oven or providing horsepower to our new automobile.
Upon finishing their job, the electrons return to the cell through the cathode. There, the catalyst assists the oxygen molecules, the hydrogen protons and the hydrogen electrons in making water. The chemical reactions are the following:
Anode:2H2 => 4H+ + 4e-
Cathode: O2 + 4H+ + 4e- => 2H2O
The whole reaction ends up looking like this:2H2 + O2 => 2H2O
This reaction only creates about 0.7 volts. Because of this, there are several cells built into a stack. This multiplies the voltage up to useable levels.
Fuel Cell

Electricity is nothing more than flowing electrons. That means that power generation is nothing more than finding out how to free electrons. Fuel cells rely on hydrogen for its electrons. There are many different fuel cells for every kind of application. But every fuel cell has the same essentials. They all have an anode (negative electrode) comprised of hydrogen gas, and a cathode (positive electrode) of oxygen. In the middle is an electrolyte that only allows protons to pass through it. In between both electrodes and the electrolyte are catalysts that facilitate the reactions
Fuel cells are an important enabling technology for the hydrogen economy and have the potential to revolutionize the way we power our nation, offering cleaner, more-efficient alternatives to the combustion of gasoline and other fossil fuels. Fuel cells have the potential to replace the internal combustion engine in vehicles and provide power in stationary and portable power applications because they are energy-efficient, clean, and fuel-flexible. Hydrogen or any hydrogen-rich fuel can be used by this emerging technology.
Types of Fuel Cells
Fuel cells are classified primarily by the kind of electrolyte they employ. This determines the kind of chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors.
Polymer Electrolyte Membrane (PEM) Fuel Cells
Polymer electrolyte membrane (PEM) fuel cells—also called proton exchange membrane fuel cells—deliver high power density and offer the advantages of low weight and volume, compared to other fuel cells. PEM fuel cells use a solid polymer as an electrolyte and porous carbon electrodes containing a platinum catalyst. They need only hydrogen, oxygen from the air, and water to operate and do not require corrosive fluids like some fuel cells. They are typically fueled with pure hydrogen supplied from storage tanks or onboard reformers.
Direct Methanol Fuel Cells
Direct methanol fuel cells (DMFCs), however, are powered by pure methanol, which is mixed with steam and fed directly to the fuel cell anode. Direct methanol fuel cells do not have many of the fuel storage problems typical of some fuel cells since methanol has a higher energy density than hydrogen—though less than gasoline or diesel fuel. Methanol is also easier to transport and supply to the public using our current infrastructure since it is a liquid, like gasoline.
Alkaline Fuel Cells
Alkaline fuel cells (AFCs) were one of the first fuel cell technologies developed, and they were the first type widely used in the U.S. space program to produce electrical energy and water onboard spacecraft. These fuel cells use a solution of potassium hydroxide in water as the electrolyte and can use a variety of non-precious metals as a catalyst at the anode and cathode. High-temperature AFCs operate at temperatures between 100°C and 250°C (212°F and 482°F). However, newer AFC designs operate at lower temperatures of roughly 23°C to 70°C (74°F to 158°F)
Phosphoric Acid Fuel Cells
Phosphoric acid fuel cells use liquid phosphoric acid as an electrolyte—the acid is contained in a Teflon-bonded silicon carbide matrix—and porous carbon electrodes containing a platinum catalyst. The chemical reactions that take place in the cell are shown in the diagram to the right.
The phosphoric acid fuel cell (PAFC) is considered the "first generation" of modern fuel cells. It is one of the most mature cell types and the first to be used commercially, with over 200 units currently in use. This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to power large vehicles such as city buses.
Molten Carbonate Fuel Cells
Molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and coal-based power plants for electrical utility, industrial, and military applications. MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum oxide (LiAlO2) matrix. Since they operate at extremely high temperatures of 650°C (roughly 1,200°F) and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs.

Solid Oxide Fuel Cells
Solid oxide fuel cells (SOFCs) use a hard, non-porous ceramic compound as the electrolyte. Since the electrolyte is a solid, the cells do not have to be constructed in the plate-like configuration typical of other fuel cell types. SOFCs are expected to be around 50-60 percent efficient at converting fuel to electricity. In applications designed to capture and utilize the system's waste heat (co-generation), overall fuel use efficiencies could top 80-85 percent. Solid oxide fuel cells operate at very high temperatures—around 1,000°C (1,830°F).
Regenerative Fuel Cells
Regenerative fuel cells produce electricity from hydrogen and oxygen and generate heat and water as byproducts, just like other fuel cells. However, regenerative fuel cell systems can also use electricity from solar power or some other source to divide the excess water into oxygen and hydrogen fuel—this process is called "electrolysis."
Applications of Fuel Cells
Fuel cells have the potential to slip into every kind of electronic device. A few applications could include:
· Cars- as stated before, fuel cells the size of a printer could provide enough juice to power as well (if not better than) a combustion engine. The hydrogen for both forms of transportation may be provided through propane, methanol or natural gas.
· Personal Devices (Laptops, cell phones, hearing aides) - fuel cells have the tremendous potential to get into every electronic device we come in contact with.
· Stationary Power Production and Backup- larger-scale fuel cells could allow every city to have its own power station, rather than a centralized power grid. Power generation could become so decentralized that each housing development or apartment complex could be self-sustained with its own power. This would drastically cut down on pollution and ugly power lines. Hospitals and airports could (some already do) have backup power supplies that kick in, in the event of a power failure.
Hydropower
Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam.
Hydroelectric power plant
Hydroelectricity comes from the damming of rivers and utilizing the potential energy stored in the water. As the water stored behind a dam is released at high pressure, its kinetic energy is transferred onto turbine blades and used to generate electricity. This system has enormous costs up front, but has relatively low maintenance costs and provides power quite cheaply.
Another type of hydroelectric power plant—called a pumped storage plant—can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.
Energy Storage
Helping secure a clean energy future for the nation and the world isn't just about reducing energy usage or producing clean energy. It is about how energy moves from the power source to the end user. Moving the energy from point A to point B, or storing it at the site where it will be used, are related to using our energy most effectively and wisely. Energy storage can improve the efficiency and reliability of the electric utility system by reducing the requirements for spinning reserves to meet peak power demands, making better use of efficient baseload generation, and allowing greater use of renewable energy technologies.
Energy Storage Technologies
Batteries
Batteries are the most common device used for storing electrical energy.
Advanced Batteries
Advanced battery technologies include lithium-ion, lithium polymer, nickel metal hydride, and sodium sulfur types. Advanced batteries offer much smaller "footprints" (i.e., they take up less space) than lead-acid batteries. They are typically CURRENTLY too expensive for large-scale utility applications, but are used for power quality and backup purposes at manufacturing plants. They are also used in consumer goods and automobiles. Lithium-ion batteries in laptop computers, for example, can provide twice as much operating time as conventional batteries. Sodium sulfur batteries can operate at high temperatures, and have proven safe even under extreme conditions.
Flow Batteries
Flow batteries work in a similar fashion to lead-acid batteries, but the electrolyte is stored in external containers and circulated through the battery cell stack as required. This external reservoir of rechargeable electrolyte can be as large as needed, and situated where convenient. Some flow batteries use two different kinds of electrolyte that are stored separately.
The great advantage to flow batteries is that their electrical storage capacity is limited only BY the capacity of the electrolyte storage reservoirs. They provide very high power and very high capacity batteries for load-leveling applications on the electricity grid. Zinc-bromine flow batteries are the most common type in use in the United States.
Lead-Acid Batteries
Lead-acid batteries are the most common type of battery. They are used in automobiles, and by both utilities and electricity consumers as a backup energy source for critical electricity needs.
The traditional lead-acid battery is made up of plates, lead, and lead oxide immersed in a solution consisting of 35% sulfuric acid and 65% water. This solution is called "electrolyte," and causes a chemical reaction that produces electrons. Various other elements are also used to change the density, hardness, and porosity of the plates.
A couple of variations on the traditional design have emerged:
Valve-regulated lead-acid (VRLA) batteries — are sealed and need no topping off with water, and so require less maintenance than regular lead-acid batteries.
Gel-type lead-acid batteries — are filled with a gel instead of liquid, making them much less likely to spill.

Compressed Air Energy Storage
Compressed air energy storage (CAES) is really a hybrid storage/power production system. Off-peak electricity is used to power a motor/generator that drives compressors to force air into an underground storage reservoir, such as a rock cavern or abandoned mine. When the demand for electric power peaks, the process is reversed. The compressed air is returned to the surface, heated by natural gas in combustors and run through high-pressure and low-pressure expanders to power the motor/generator to produce electricity.
In traditional gas turbines, the air that drives the turbine is compressed and heated using natural gas. CAES technology needs less gas to produce power because it uses air that has already been compressed. There is only one CAES facility operating in the United States at present.
Has high energy storage capacity compared to the alternatives. About 10 times higher per cubic meter than water.
One example (in Germany) to date:
· Storage reservoir is underground cavity in a natural salt deposit.
· The storage volume is 300,000 cubic meters.
· Sheer weight of the salt deposit is able to pressure confine the air reservoir.
· Air is compressed to 70 atm (1000 lbs per square inch)
· Compression is done by electrically driven air compressors
· System delivers 300 Megawatts for 2 hours by using the compressed air to drive a turbine
· Difficult to measure the efficiency of this system. Two major contributions to the inefficiency:

o Energy required to cool the air as it is being put into storage this is a critical requirement (see below)
o Energy required (usually from fuel) to expand the cool air taken from storage as it entries the turbine.
· Desirable design feature would be recycle the waste heat from the compression stage and use it to reheat the air during expansion stag
Flywheels
A flywheel is a cylinder that spins at very high speeds, storing kinetic (movement) energy. A flywheel can be combined with a device that operates either as an electric motor that accelerates the flywheel to store energy or as a generator that produces electricity from the energy stored in the flywheel. The faster the flywheel spins, the more energy it retains. Energy can be drawn off as needed by slowing the flywheel.
Modern flywheels use composite rotors made with carbon-fiber materials. The rotors have a very high strength-to-density ratio, and rotate in a vacuum chamber to minimize aerodynamic losses. The use of superconducting electromagnetic bearings can virtually eliminate energy losses through friction. Flywheels can discharge their power either slowly or quickly, allowing them to serve as backup power systems for low-power applications or as short-term power quality support for high-power applications. They are little affected by temperature fluctuations, take up relatively little space, have lower maintenance requirements than batteries, and are very durable.
Pumped Hydropower
Pumped hydro facilities use off-peak electricity to pump water from a lower reservoir into one at a higher elevation. When the water stored in the upper reservoir is released, it is passed through hydraulic turbines to generate electricity.
The off-peak electrical energy used to pump the water up hill can be stored indefinitely as gravitational energy in the upper reservoir. Thus, two reservoirs in combination can be used to store electrical energy for a long period of time, and in large quantities.
Supercapacitors
Supercapacitors are electrochemical storage devices that work like large versions of common electrical capacitors. They are also known as ultracapacitors or electrochemical double-layer capacitors. Unlike batteries, supercapacitors store their energy in an electrostatic field rather than in chemical form.
Batteries are charged when they undergo an internal chemical reaction. They discharge, delivering the absorbed energy, when they reverse the chemical reaction. In contrast, when a supercapacitor is charged, there is no chemical reaction. Instead, the energy is stored as a charge or concentration of electrons on the surface of a material.
Supercapacitors are capable of very fast charges and discharges, and can typically be recharged hundreds of thousands of times, unlike conventional batteries which last for only a few hundred or thousand recharge cycles. But their power is available only for a very short duration, and their self-discharge rate is much higher than with batteries. Common applications include starting diesel trucks and railroad locomotives, and in electric/hybrid-electric vehicles for transient load leveling and capturing the energy used in braking. In power systems, they are most likely to be used as bridging power sources in uninterruptible power supplies, much like flywheels.
Superconducting Magnetic Energy
Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current through a large coil of superconducting material that has been super-cooled. In low-temperature superconducting materials, electric currents encounter almost no resistance, greatly enhancing their storage capacity.
Power is available almost instantaneously from SMES systems, and very high power output is provided for a brief period of time. There are no moving parts. However, the energy content of SMES systems is small and short-lived, and the cryogenics (super-cooling technology) can be a challenge. Researchers are trying to find ways to maintain the special qualities of SMES without having to keep the systems quite so cold. Low-temperature SMES cooled by liquid helium is commercially available today, and "high temperature" (less cold) SMES cooled by liquid nitrogen is in development
Energy Density of Some Materials (KHW/kg) · Gasoline --------------> 14· Lead Acid Batteries ----> 0.04· Hydrostorage -----------> 0.3 (per meter3)· Flywheel, Steel --------> 0.05· Flywheel, Carbon Fiber -> 0.2· Flywheel, Fused Silica -> 0.9· Hydrogen ---------------> 38· Compress Air ------------> 2 (per meter3)
Energy density storage drives the choices that can be made. Technology helps to drive this. As discussed previously, energy storage in batteries is not sufficiently high to solve the basic problem

2006-01-02T21:56:00.000-08:00

Pushpendra

INTRODUCTION TO THE ARMOURED FIGHTING VEHICLES:
By Pushpendra Singh

1.1) CONCEPT OF MODERN BATTLE TANK DEVELOPMENT:
The idea of development of the modern tracked fighting vehicle arose from the visualization of the armoured Rolls Royce cars used in 1914.The awareness to create such a vehicle arose in the mind in the First Lord of the Admiralty, Winston Churchill, who sponsored the Landships Committee to oversee development of this new weapons system. The first successful prototype tank, nicknamed "Little Willie", was tested for the British Army on September 6, 1915. Although initially termed "landships" by the Admiralty, the initial vehicles were colloquially referred to as "water-carriers", later shortened to "tanks", to preserve secrecy. The word "tank" was used to give the workers the impression they were constructing tracked water containers for the British army in Mesopotamia.
Fig.1. This German photograph from World War I shows a captured British tank.This diagram shows the past scenario of the tanks. The foremost part of the tracks is high off the ground in order to climb obstacles. The main guns are side-mounted to keep the centre of gravity low.

The first tank became operational when Captain H. W. Mortimore of the Royal Navy took a Mark I into action at Delville Wood during the Battle of the Somme on September 15, 1916. The French developed the Schneider CA1 working from Holt caterpillar tractors, and first used it on April 16, 1917. The first successful use of massed tanks in combat occurred at the Battle of Cambrai on November 20, 1917.
The tank would eventually make trench warfare obsolete, and the thousands of tanks, fielded by French and British forces ,made a significant contribution to the war. Initial results with tanks were mixed, with problems in reliability causing considerable attrition rates when getting the tanks into combat and on the move. They lacked the mobility and flexibility.This forced the development of tanks such as the Mark IV, which rhomboid shape could navigate large obstacles, especially long trenches. The development of the modern battle tank concept arose from the mobility and maneuverability characteristics of Mark IV tank.
With the tank concept now established, several nations designed and built tanks between the two world wars.

1.2) OVERVIEW OF MODERN MATTLE TANKS:
A modern battle tank is a tracked, armoured combat vehicle (armoured fighting vehicle), designed primarily to engage enemy forces by the use direct fire. A modern main battle tank (MBT) is distinguished by its high level of firepower, mobility and armour protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds, but is fuel, maintenance, and ammunition-hungry and is logistically demanding. It has the heaviest armour of any vehicle on the battlefield, and carries a powerful weapon able to engage a wide variety of ground targets. It is among the most versatile and fearsome weapons on the battlefield, valued for its shock action against other troops and high survivability.
Tanks are usually employed with infantry in combined arms warfare, supported by engineers, artillery, aircraft, and other support arms. If not properly protected, tanks can be vulnerable to attack by infantry, mines, artillery, and aircraft strikes.
1.3) GENERAL CHARACTERISTICS OF MODERN BATTLE TANKS:
The characteristics of main battle tanks can be viewed in terms of various factors:
1.WEAPON SYSTEM:
The main weapon of any modern tank is a single large gun. Tank guns are among the largest calibre weapons in use on land, with only a few artillery weapons being larger. Although the calibre has not changed substantially since the end of the Second World War, modern guns are technologically superior. The current common sizes are 120-mm calibre for Western tanks and 125-mm for Eastern (Soviet and Chinese legacy) tanks. Tank guns have fired many types of rounds, but their current use is commonly limited to kinetic energy (KE) penetrators and high explosive (HE) rounds. Some tanks can fire missiles through the gun. Smoothbore (rather than rifled) guns are the dominant type of gun today. The British Army and the Indian Army are now the only ones to field main battle tanks with rifled guns.
Modern tank guns are generally fitted with thermal jackets which reduce the effect of uneven temperature or cooling of the barrel. Eg if it were to rain on a tank barrel the top would cool faster than the bottom, or a breeze on the left might cause the left side to cool faster then the right. This uneven cooling will cause the barrel to bend slightly and will effect long range accuracy. The thermal jacket reduces this uneven cooling.
Usually, tanks carry other armament for short range defence against infantry or targets where the use of the main weapon would be ineffective or wasteful. Typically, this is a small calibre (7.62 to 12.7 mm) machine gun mounted coaxially with the main gun. However, a couple of French tanks such as the AMX-30 and AMX-40 carry a coaxial 20-mm cannon that has a high rate of fire and can destroy lightly armoured vehicles. Additionally, many tanks carry a roof-mounted or commander's cupola machine gun for close-in ground or limited air defence. The 12.7-mm and 14.5-mm machine guns commonly carried on US and Russian tanks and the French Leclerc are also capable of destroying light armoured vehicles, such as APCs and possibly IFVs at close range.
Some tanks have been adapted to specialised roles and have had unusual main armaments such as flame-throwers. These specialised weapons are now usually mounted on the chassis of an armoured personnel carrier.
2. FIRE CONTROL:
Historically, tank weapons were aimed through simple optical sights and laid onto target by hand, with windage estimated or assisted with the reticule. Range-finding was initially estimated, then estimated again with the aid of the reticule (which uses the measurement of angles, measured in the reticule of known sized objects as a method for range finding), which was later supplemented with stereoscopic optical range-finders, which remained the standard until the introduction of laser range-finder. Consequently, accuracy was limited at long range and made concurrent movement and shooting largely impossible.
Most of the modern MBTs and upgraded MBTs in the armies of industrialised countries use a laser range-finder but optical and reticule range-finders are still in use in older and less sophisticated vehicles. Modern tanks have a variety of sophisticated systems to make them more accurate. Gyroscopes are used to stabilise the main weapon; laser range-finders are used to measure the range to the target; computers calculate the appropriate elevation and aim-point, taking into account many factors such as wind speed, air temperature, humidity, the temperature of the gun, the speed of the target (calculated by taking at least two sightings of the target with the range-finder), the speed of the tank, the bend of the barrel, and the wear of the barrel. Night and infrared vision equipment is also commonly included. Laser target designators may also be used to illuminate targets for guided munitions. As a result modern tanks can fire reasonably accurately while moving. .
Most of the modern MBTs and upgraded MBTs in the armies of industrialised countries use a laser range-finder but optical and reticule range-finders are still in use in older and less sophisticated vehicles. Modern tanks have a variety of sophisticated systems to make them more accurate. Gyroscopes are used to stabilise the main weapon; laser range-finders are used to measure the range to the target; computers calculate the appropriate elevation and aim-point, taking into account many factors such as wind speed, air temperature, humidity, the temperature of the gun, the speed of the target (calculated by taking at least two sightings of the target with the range-finder), the speed of the tank, the bend of the barrel, and the wear of the barrel. Night and infrared vision equipment is also commonly included. Laser target designators may also be used to illuminate targets for guided munitions. As a result modern tanks can fire reasonably accurately while moving.
3.PROTECTION:
The main battle tank is the most heavily armoured vehicle in modern armies. Its armour is designed to protect the vehicle and crew against a wide variety of threats. Commonly, protection against kinetic energy penetrators fired by other tanks is considered the most important. Tanks are vulnerable to antitank guided missiles. Antitank mines, larger bombs, and direct artillery hits can also disable or destroy a tank. Tanks are especially vulnerable to airborne threats. Most modern MBTs do offer near complete protection from artillery shrapnel and lighter antitank weapons such as rocket propelled grenades. The amount of armour needed to protect against all conceivable threats from all angles would be far too heavy to be practical, so when designing an MBT much effort goes into finding the right balance between protection and weight.
4. MOBILITY:
The main battle tank is the most heavily armoured vehicle in modern armies. Its armour is designed to protect the vehicle and crew against a wide variety of threats. Commonly, protection against kinetic energy penetrators fired by other tanks is considered the most important. Tanks are vulnerable to antitank guided missiles. Antitank mines, larger bombs, and direct artillery hits can also disable or destroy a tank. Tanks are especially vulnerable to airborne threats. Most modern MBTs do offer near complete protection from artillery shrapnel and lighter antitank weapons such as rocket propelled grenades. The amount of armour needed to protect against all conceivable threats from all angles would be far too heavy to be practical, so when designing an MBT much effort goes into finding the right balance between protection and weight.
For most tanks, water movements are also possible. The water operations are limited to fording. The fording depth is usually limited by the height of the air intake of the engine, and to a lesser extent the driver's position. Typical fording depth for MBTs are 90 to 120 cm. However, with preparation some tanks are able to ford considerably deeper depths. The West German Leopard I and Leopard II tanks can ford to a depth of several metres, when properly prepared and equipped with a snorkel. Some light tanks such as the PT-76 are amphibious, typically being propelled in the water by hydrojets or by their tracks.Often a fold down trim vane is erected to stop water washing over the bow of the tank and thus reducing the risk of the vehicle being swamped via the driver's hatch.

1.4) ARE THESE CHARACTERISTICS SUFFICIENT?

“In modern tanks, in first gear, you can take your pet turtle for a walk. In the sixth, you can walk away from almost anybody. Its like a pussy cat on metalled roads or built up areas and a lion in the open fields and deserts.”
The present day tanks are equipped with the necessary characteristics, such as-1.Adequate Fire Power capability, 2.Protection facilities, 3.Provision of Surplus power, as required, 4.Shock Action capability and 5. Good Mobility and Maneuverability characteristics. Undoubtedly these are the necessary factors for an effective tank operation; but not sufficient enough for the required present day combat effectiveness.
In addition to the above, some of the other suggested qualities include-1.Capability of avoiding enemy detection, 2.Reduced target size(Presentation of low silhoutte) and weight for greater mobility, 3.Reduced crew size for weight reduction, 4.More unmanned operational effectiveness, 5.Crew comfort improvement, 6.More destructive potential with advanced weapons systems, 7.Dual Purpose Armour development, both for protection as well as reaction to enemy attacks, 8.Capability of Silent operations, required for Shock Action purpose, 9.Enhanced endurance and what not! Thus, creativity plays a great role behind establishing these sufficient facilities.

2. NEED FOR FURTHER RESEARCH IN COMBAT FIELD:

“A battle tank can be described as an unique animal. It needs the speed of a greyhound, the strength of a bull, the suspension of a kangaroo and the staying power of a mule. Then, when its all put together, its supposed to handle like a champion show horse.”
Battle tanks are offensive weapons system; thus they should be equipped with advanced protection systems also to suffice their survivability aspect in the modern devastating battlefield. In order to improve upon the tank qualities, as mentioned above, new designs of battle tanks are necessary. Tanks and tank tactics have undergone many generations of evolution over nearly a century. Although weapons systems and armour continue to be developed, many nations have been reconsidering the need for such heavy weaponry in a period characterised by unconventional warfare.
The new designs are directed to increasing the battlefield lethality of the tanks by improved ammunition and increased calibers and also towards a higher level of tank protection.In order to decide for the possible new designs to be conducted, a short glimpse at the present combat system drawbacks should be taken. The present day tanks have-1.Thicker and heavier armour, 2.Increased size and weight, 3.Increased target size, 4.Increased armoured volume and 5.Reduced survivability and mobility. These are not at all the acceptable status for the modern tanks. Thus other alternative actions should be adopted.
Military Researchers are resorting to radical designs in order to achieve: 1.Reduced volume, 2.Reduced target size, 3.Reduced weight, 4.Enhanced protection, 5.Detection Avoidance, 6.Hit Avoidance and 7.Enhanced endurance.
Need for further design may arise due to desire to abandon the classical concept of the turreted tank in favour of concepts for lighter vehicles, featuring external or overhead-mounted main armament. There will be demands for increased lethality of tank armaments against other hostile tanks and against hostile helicopters(The most dreaded and undefeatable enemy of the modern tanks). In this respect there seems to be no second opinion to use a high pressure gun in the forseable future. It may be necessary to increase its caliber and to introduce new types of ammunition. To help improved crew survivability and vehicle restorability, the main armament has to be located in such a position that the volume of the tank can greatly be reduced. An automatic loader will have to be introduced to load rounds from a magazine that well may be totally separated from the crew and other vital components. One very important aspect of battletank design, that has a significant bearing on the effectiveness of such vehicles, is their availability, ie, the ability of an individual tank to be ready for battle at any given time and in any location. There may be a requirement to alter the present shape of the tanks, in order to achieve this area. To enhance availability, the vehicle weight must be kept down to a level at which maximum use can be made of all infrastructure in potential warzones. Increased availability is also a function of speed, fuel consumption, reliability and life of mechanical and electrical components. To cite an example, both NATO and Warsaw Pact countries are trying to rectify this problem, especially the NATO countries, whose battle tank weight lies between 55-65 tonnes. Improvements are continually being made in this respect, leading to greater component weight savings and volume reductions in the future(in the field of propulsion, notably). However these savings are not the only remedy, which might enable researches to work along traditional improved lines.

2.1) BASIS OF BATTLE TANK DESIGN:
The three traditional factors determining a tank's effectiveness are its firepower, mobility, protection and shock action . The psychological effect of a tank's imposing battlefield presence on enemy soldiers is called shock action. Thus, initially a silent operation of the tank is needed from a non-detectble range; as it approaches very near to the enemy line, it needs to generate huge noise so as to confuse the enemy about the side from which the tank is approaching.Thus the tank needs to have a flexible and well maintained power train in opeation. Firepower is the ability of a tank to defeat a target. This includes the maximum distance at which targets can be engaged, the ability to engage moving targets, the speed with which multiple targets can be destroyed, the capability to defeat armoured vehicles or entrenched infantry, and the ability to continue fighting after damage has been sustained.
Mobility includes the speed and agility of driving cross-country, the types of terrain that can be covered, the size of obstacles, trenches, and water that can be crossed, the ability to cross small bridges, and the distance that can be covered before refuelling is required. "Strategic mobility" also includes the ability to travel at high speed on roads, and the ability to be carried on rail or truck transport. Traditionally AFV mobility is measured by the following metrics:
engine power
engine torque
power-to-weight ratio
road speed
off-road speed (a somewhat nebulous figure given the possible variation)
road range
off-road range
weight (bridge classification)
ground pressure
width of trench crossed
vertical step climbed
angle of slope that can be climbed
angle of side slope that can be negotiated
ground clearance
unprepared fording depth
prepared fording depth (if different)
Protection is the amount of armour, the type(s), how it is arranged (e.g., whether it is sloping or not), and which areas are given more protection (e.g., the turret and tracks) and which receive less (e.g., the rear of the chassis). It also includes low profile, low noise and thermal signature, active countermeasures, and other methods of avoiding enemy fire.
Tank design is traditionally considered to be a compromise between these three factors—it is not possible to maximise all three. For example, increasing protection by adding armour will increase weight and therefore decrease manoeuvrability; increasing firepower by using a larger gun will decrease both manoeuvrability and protection (due to decreased armour at the front of the turret).
However,the compromise is achieved by a combination of factors, including military strategies, budget, geography, political will, and the requirement to sell the tank to other countries.
Let us take examples of a few countries to briefly discover basis of their designs:
Britain has historically opted for better firepower and increased protection at the expense of some manoeuvrability. Britain maintains a small, highly trained professional army, and so tank crew survivability is important. As limited resources may be available, the crew needs to be able to maintain their tanks in the field, and, with a succession of secondary sites available, are able to keep fighting if the primary site is out of action.
USA has a large army with sophisticated weaponry and a complex array of mobile support services. As their tanks are expected to rarely be away from support and repair units, less emphasis is placed on the crew's ability to maintain the tank themselves or to continue fighting with it once damage has been sustained.
Germany had tanks were completely outmanoeuvred on the Russian front during WWII by the T-34, which was a major factor in their defeat. Also they lost more of their overly complex Tiger and Panther tanks due to mechanical breakdowns than enemy action. As a result German tanks in the post war era have been designed to be very manoeuvrable, with a resulting decrease in protection. Enhanced reliability and lower maintenance requirements have also been important design goals.
Israel is a small, but relatively rich, nation, with limited manpower in a hostile political environment. Its primary concern is therefore crew survivability. To this end it is the only nation to have produced a modern tank with the engine placed at the front, to increase protection for the crew behind it.

3) CURRENT DESIRED RESEARCH PROGRAMS:
Modern progressing Research and Development activities, taking place in the field of Combat Engineering, are mostly directed towards the upgradation of the already existing facilities on an armoured fighting vehicle, for improved flexibility, survivability and surveillance activities on the battlefield. Its not totally devoted to the generation of a completely new Future Combat System, which cannot be identified as a particular category of the present day battle tank, as we see today.
Tank research and development activities were in the booming stage, during the period when the United States and the Soviet Union were engaged in a massive arms race. It continued in many industrial countries despite the end of the Cold War;but with a low investmest because of the lack of forecasting future threats.One of the most pioneer contributors to innovative tank designs, is the Kharkiv Morozov Machine Building Design Bureau, which is at present a unit of the Ukranian government. Another important contributor to the battle tank protection and reconnaissance systems, is the U.S. Defence Advanced Research Program Agency(DARPA), which we’ll see later.
The latest battle tanks show a growing trend for computerization and automation of components. Future tank designs, such as the Russian T-95 and the US MCS, are proposed with unmanned turrets, with the crew in a single compartment in the hull of the tank, from which they can control the turret remotely. The turret's automatic loading system can then fire ammunition faster and of a size too large for a human loader, as well as store ammunition more efficiently since there is no need for crew space in the turret. Thus, the trend towards production of turretless tanks(ie, abandoning of two-tier arrangement for a single tier) can be achieved in two ways:1.Main Armament out of the crew compartment and 2.Remote controlled automatic gun-loading system. Because the crew are contained in a single compartment space in the hull, the tank's size and mass can be reduced. Composite designs and lighter chassis are also proposed to reduce the tank's weight further to improve deployment and logistics.Thus research is conducted accordingly. Thus, the desired activities are mainly concentrated on the following areas:
1.Weapons Research.
2.Armour Research.
3.Stealth Research.
4.Power Plant Research.

3.1) Weapons Research:
A battle tank is not a defensive weapons system; but totally an offensive one in the Army. It is an attacking system. Thus one of the major prerequisites of battlefield survivability of the tank, is the advanced weapons systems on it. Initially battle tanks were fitted with the main cannon system.Since the end of the second world war and the general introduction of missiles, many have speculated that the modern battle tank's main cannon has become inferior and thus have become obsolete. With anti-tank missile having greater range, accuracy and ergonomics, the battle tank’s cannons had proved ineffective.
Thus, it was proposed for a missile as the tank armament system,initially. A missile-carrying tank could be turret-less, thus reducing the tanks visible profile, weight and construction costs. Missiles could be launched vertically to reduce target acquisition time and increase the rate of fire. Also a missile tank with advanced computerize missiles could target anything from airplanes, helicopters, ships and stationary targets. But then came the supporters of the advanced guns system.They were opposed to missiles, pointing out that advanced gun systems can do all of the above, in addition to killing enemy soldiers with shrapnel rounds, in a more cost-effective way. They have also pointed out that anti-tank missiles have proved ineffective in penetrating the rapidly developing armour standards, with their increased protective and reactive potential. The debate on the relevance of guns and missiles continued over the decades.
Modern tank armament development has tended to focus on cannon fired KE penetrators,ie armour piercing ammunitions,such as High Explosives Squash Head, High Explosive Anti Tank and hollow shaped charges as well.It was found that most of the developed armour systems could not defeat these very basic rounds. Increasing the velocity of gun-fired penetrators has been a major focus to increase range, accuracy and penetration. At present, weapons research is conducted in the following areas:
1.Conventional 140mm guns.
2.Liquid Propellant Guns.
3.Electromagnetic Guns.
4.Electrothermal Chemical Guns.
5.Plasma Impulse Guns.

3.1.1) Conventional 140mm guns:
The latest tanks are already well armed with guns of 120mm or 125mm, which are capable of defeating heavy armor, and their performance can be stretched further. However, there are indications that, even at their best, these guns will not be able to defeat the kinds of armour that are being developed for future tanks. In that situation, it is necessary to resort to guns of larger calibre, and several countries have been working for some time on 140mm guns that fire APFSDS projectiles with twice the muzzle energy of those fired by the current 120mm tank guns.

A major consequence of the diminished urgency to develop novel guns in the near foreseeable future is that conventional, Solid Propellant (SP) guns will remain in service for many years to come, and their lethality will be gradually enhanced. The typical High Velocity Armor PiercingFin Stabilized Discarding Sabot(HV-APFSDS) projectile has been successively improved over the last three decades with suggested near-future penetration capability of up to 800-900+ mmof Rolled Homogenized Armor (RHA).This was primarily achieved by a progressive increase of the geometrical ratio ‘Length/Diameter’ (L/D) of relatively long and slender rod penetrators and continuous improvements to their corresponding materials (Tungsten Alloys,Powder Metallurgy-PM, Depleted Uranium-DU, and Variable Density Penetrators-VDP). Penetrators with high ‘L/D’ ratios proved effective against RHA but they were found considerably less effective against composite and/or complex armor. To augment its effectiveness against thelatter, the penetrator rod must have a larger diameter. Without reverting to lower and adverse ratios of ‘L/D’ (approximately20/1 for 120mm and experimental140mm and still increasing), it must ultimately result in an increase of volume and mass of the penetrator rod and therefore, inevitably, in a corresponding undesirable reduction of the effective muzzle velocity. Utilization of progressively heavier rod penetrators to defeat contemporary and ever-improving armor protection required higher muzzle energy [presently 18-20 megajoules(MJ)]. Consequently, it led to guns withever-increasing chamber pressures and likewise, larger gun calibers (90, 105,120, 140mm, Western preference). Following a MOU previously signed in 1988 with the U.S., Giat (France), Rheinmetall (Germany) and Royal Ordnance (U.K.) are contemplating a joint venture to develop, market and produce a standardized 140mm smoothbore/rifled gun and ammunition. The weapon system is designated by NATO as the Future Tank Main Armament(FTMA) and is claimed to have a significant increase in armor penetration over the standard 120mm tank gun.

As part of this development, the German firm of Rheinmetall has mounted its 140mm gun in a Leopard II tank. The Swiss Federal Construction Works has also mounted its 140mm gun in a Leopard II. These experiments indicate that the retrofitting of 140mm guns in the existing tanks is possible. But it presents a number of major problems. In particular, 140mm rounds are large and heavy, which makes them difficult, if not impossible, to manhandle. As a result they require automatic loading systems, and this implies major changes to tank turrets and a reduction in the size of tank crews from four to three men. The UK, Germany and France are working on a 140mm tank gun. While these can be fitted to tank turrets, the size of the rounds and the need for an autoloader make the practicality of this doubtful. One option may be to adopt an assault gun configuration capable of high elevation fire. A 140mm high velocity gun could be at least equal in range to a 155mm howitzer [5.5" (140mm) were the standard medium field piece of the British Army in the Second World War]. A 140mm gun on an assault gun body could be a useful weapon system both for divisional artillery and to reinforce armored or infantry attacks. The only problems with this idea at present is that the prototype 140mm gun is smoothbore, and no 140mm guided projectiles currently exist. The only type of automatic loading system, which may readily be installed in existing tanks, is one installed in the turret bustle. In consequence, the configuration of tanks rearmed with 140mm guns should resemble that already adopted for the Japanese Type 90 and the French AMX Leclerc. In fact, this configuration has actually been adopted for CATTB, (Component Advanced Technology Test Bed) built recently in the US, to explore the future form of tanks. Thus CATTB has a three-man crew and a bustle auto loader for its XM-291 gun, which can be fitted with either a 120mm or a 140mm barrel. Because of the problems they pose and the absence of a threat, which would urge their adoption, the development of 140mm tank guns is proceeding slowly. The problems they pose are also encouraging people to consider potential alternatives to conventional 140mm guns. One of them is liquid-propellant guns, which were seriously considered for tanks.
Notwithstanding the 140mm gun andammunition’s indisputable potential, the larger gun size will command a bigger and heavier vehicle. If the requirement to reduce weight and volume is going to remain firm and strictly enforced, it is most unlikely that the 140mm gun andheavy ammunition will find their way into the FCS.

3.I.2) LIQUID PROPELLANT GUNS:
Regardless of how SP guns will ultimately evolve, both users and defense research community have concluded that solid propellants are not the most efficient medium of conveying to a projectile, the energy required to defeat the ever-evolving threat. Consequently, since the mid 80’s, there has been a significant increase in Western R&D interest and research efforts, aimed particularly at developing new technologies, which will substitute for contemporary SP gun systems.
Thus, Liquid Propellant(LP) gun propulsion technology is another viable alternative. LP technology is the outcome of extensive R&D efforts performed in several countries, ever since the end of WWII. Though LP is technologically based on a sound engineering foundation, it is presently known to experience inherent prematuration, nagging problems such as ignition control, excessive corrosion, combustion non-repititiveness, sealing, exorbitant weight growth, material contamination and difficulties in handling of LP. LP requires the continuous resupply of propellant working fluid, which does not conform favourably with stringent requirements of reduced logistics. LP, in conjunction with 120/140 mm tank guns with regenerative, multistaging propellant injection systems, could reach muzzle velocities up to 220-22500 m/s respectively at best. Its about 10-15% higher than that what could ultimately be achieved with SP 120/140 mm guns. This only holds true if ailing problems with traveling charge or stage propellant will be satisfactorily resolved to match the injected charge front propagation speed, through the entire injection process with that of the projectile as it advances down the barrel. It has already been demonstrated that by using a 30mm two stage traveling charge, velocities as high as 3100m/s and beyond could be achieved. Thus LP guns have a high level of design flexibility and possess controlled, variable lethality and permit a relatively large stowed load due to improved efficiency of LP storage and reduced volumetric requirements in comparison to SP combustible cases. Other advantages are safer storage of LP via compartmentalization, improved piezometric efficiency and extended barrel life due to a much cleaner and better controlled combustion processes. Last, but not the least, RILP technology represents a rational leverage of the substancial investment already made in the LP version of the revolutionary Crusader.
But, LP technology, though belived to be the prime alternative to SP, is sometimes viewed as less attractive for ground mobile applications and thus may not become the main armament of the FCS. Nonetheless, all this may dramatically change if these technical difficulties would somehow be removed satisfactorily. Inspite of its recent handicap, research and development of Regeneratively Injected LP guns (RILP) for various ground tank applications will most likely continue. Figure below demonstrates the inteaction between the liquid propellant and the moving mechanical components of the gun.

FIG.2. RILP gun with its moving mechanical parts.

3.1.3) ELECTROTHERMAL CHEMICAL GUNS:
Encouraging results have been obtained with Electrothermal Chemical (ETC) experimental guns. In principle, it uses a chemically energetic working liquid instead of conventional solid propellants. It requires considerably less electrical energy to achieve adequate projectile propulsion than its predecessor-Electrothermal experimental guns. It needs relatively smaller and lighter auxiliary equipment to produce and store electricity. Electrothermal-Chemical (ETC) technology is an advanced gun propulsion candidate that can substantially increase gun performance with less system burden than any other advanced gun propulsion technology. It has been under development since the mid 1980s.ETC uses electrical energy to augment and control the release of chemical energy from existing or new propellants, and can significantly improve the performance of existing conventional cannons, both direct fire (e.g., tanks) and indirect fire (e.g., howitzers and Navy guns). The electrical energy is used to create a high-temperature plasma, which in turn both ignites the propellants and controls the release of the chemical energy stored in the propellants during the ballistic cycle.This equipment could ultimately be reduced to a suitable size to warrant its installation on armoured vehicles. Energetic working fluid is naturally prone to be problematic in operation, handling, storage and supply, such that its utilization will pose a potential safety concern and a logistic burden, similar to LP guns. As in LP, ETC implementation requires new industrial and military infrastructures for production, deployment, and logistics. Current developments are aimed at a medium caliber (60-80mm), antitank gun with a firing rate of 10-15 rounds/min. At this caliber range, various types of rounds could be comprised of KE projectiles and CE rounds, as well as future‘smart’ sensor-fuzed munitions.
United Defense Industries achieved an industry first recently when it successfully fired a 120mm Electrothermal Chemical (ETC) gun from a hybrid electric drive combat vehicle(Shown below).This effort, using a fully integrated 100kJ pulse power system, was accomplished through a Cooperative Research and Development Agreement with the US Army's Armament Research Development and Engineering Center (ARDEC). ARDEC is the Army's center of excellence for armament systems development.
Fig.3.United Defense Industries' 120mm Electrothermal Chemical gun.
The ultimate objective is aimed at an ETC automatic gun with a muzzle energy of 20+MJ (corresponding to 2500-3000 m/secfor medium calibers) which is comparable to that of the conventional, solid propellant140mm gun. Much like LP guns, ETC technology allows better control of the pressure (propulsion) generated, so that it is maintained relatively close to its maximum while the projectile is moving down the barrel, resulting in more energy conveyed to the projectile. This is quite contrary to conventional SP technology, where the pressurequickly diminishes as the projectile departsfrom the combustion chamber. ETC technology is recognized by many to show promise of “infinite” or multistage variable lethality and improved propulsion controllability. It also requires significantly less electrical energy in comparison to Electro-Magnetic (EM) guns that use only electricity for projectile propulsion. Nevertheless, ETC technology, as promising as it may seem, requires further fundamental research beyondthe laboratory stage. Much detailed research and testing has yet to be accomplished in the field and at weapon systemlevel. It must achieve maturation to warrant its applicability asa stand-alone solution, or in conjunction with other mature technologies, or with existing 120/140mm guns. As an additional practical alternative, ETC technology could be combined with existing conventional SP 120mm and/or future 140mm guns and ammunition, though a new cartridge and modifiedgun chamber are required. It represents a near-term upgrade application of already leveraged and proven technology. Thesize of the electrical equipment is much smaller than that of current EM research guns and present ETC as a viable upgrade proposition. Research has shown that specially designed ammunition and ETC gun technology could be combined with existing conventional SP guns to further enhance the performance of the latter up to 30% and beyond. Augmenting the energy of solid propellant is possible by implementing a plasma regenerative injector and combustion control to the conventional pressure chamber. In the event that ETC technology will become practical, existing conventional 120mm and future 140mm guns could be economically converted into ETC/SPguns as one more step in the evolutionof SP guns. There are still various predominating problems to be addressed and resolved before ETC guns can become a practical proposition in conjunction with conventional solid propulsion. The combination of controllable, repeatable inner ballistics with a compatible solid propellant, and the significant increase in performance (e.g. muzzle velocity) in large caliber guns, has yet to be demonstrated. Regardless of whether ETC technology will become a viable proposition, the useof large consumable ammunition in addition to ‘energetic’ liquid propellant is contradictory to the requirement of reduceddependency on logistics andweight. The combined implementation of SP with ETC, will probably not justify the enormous investment in design, development and deployment associated with the fielding of an entirely new tank fleet. Though new and promising technology, it will not change the nature of armored warfare.

3.1.4) ELECTROMAGNETIC GUNS:
These are also known as the Pulsed-Power EM guns. They consist of two varieties-1.Rail guns and 2.Coil guns.
3.1.4.1)RAIL GUNS:

Fig.4. Schematic Diagram of an Electromagnetic Rail gun.
Railgun is a form of gun that converts electrical energy—rather than the more conventional chemical energy from an explosive propellant—into projectile kinetic energy. Railguns utilize an electromagnetic force called the Lorentz force to propel an electrically conductive projectile that is initially part of the current path. Sometimes they also use a movable armature connecting the rails. The current flowing through the rails sets up a magnetic field between them and through the projectile perpendicularly to the current in the rail. This results in a mutual repulsion of the rails and the acceleration of the projectile along them.The world's first large scale railgun was designed and constructed in the 1970s by John P. Barber, a Ph.D. Scholar from Canada and his advisor Richard A. Marshall from New Zealand, in the Research School of Physical Sciences at the Australian National University. The system used the very large (500MJ of stored energy) Mark Oliphant homopolar generator as its energy source.

Theory and construction:

Fig.5. Schematic diagram of a railgun

Although conceptually simple, the operation of a railgun involves several factors that have to this day made a practical design (one that can be employed in the field in order to replace conventional weapons) impossible.A wire carrying an electrical current, when in a magnetic field, experiences a force perpendicular to the direction of the current and the direction of the magnetic field. This is the principle behind the operation of an electric motor, where fixed magnets create a magnetic field, and a coil of wire is carried upon a shaft that is free to rotate. When electricity is applied to the coil of wire a current flows, causing it to experience a force due to the magnetic field; the wires of the coil are arranged such that all the forces on the wires act to make the shaft rotate, and so the motor runs.
A railgun is even simpler than a motor. It consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (from the end connected to the power supply), it completes the circuit. Electrical current runs from the positive terminal of the power supply up the positive rail, across the projectile, and down the negative rail back to the power supply again.This flow of current makes the railgun act like an electromagnet, creating a powerful magnetic field in the region of the rails up to the position of the projectile. In accordance with the right-hand rule, the created magnetic field circulates around each conductor. Since the current flows in opposite direction along each rail, the net magnetic field between the rails (B) is directed vertically. In combination with the current (I) flowing across the projectile, this produces a Lorentz force which accelerates the projectile along the rails. There are also forces acting on the rails attempting to push them apart, but since the rails are firmly mounted they cannot move. The projectile is able to slide up the rails away from the end with the power supply.
If a very large power supply, providing a million amperes or so of current, is used, then the force on the projectile will be tremendous, and by the time it leaves the ends of the rails it can be travelling at many kilometres per second. 20 kilometers per second has been achieved with small projectiles explosively injected into the railgun.
3.1.4.2) COIL GUNS:
Coil guns use electric currents within coils inside a barrel that generates a magnetic field. This magnetic field then induces a current in an armature that creates a counter magnetic field, creating an acceleration on the armature and its projectile. The armature and projectile are accelerated to high velocities by sending it through a series of switched coils timed to the passage of the armature and projectile. Because the armature and barrel coils are coupled magnetically, the armature and projectile are self-centering within the barrel coils, with no physical contact between the armature and the barrel coils, eliminating barrel wear. The current state of development of coilgun technology makes them better suited for lower velocity, higher mass uses than kinetic weapons applications (e.g., missile or torpedo launchers, or even mortars).Sandia National Laboratory is one organization that is currently working on coil gun technologies (Picture shown below).
Fig.6 Diagram showing coil gun concept.

Thus, a Coilgun (also known as Gauss gun rifle or Gauss) is a type of cannon that uses a series of electromagnets to accelerate a magnetic shell to very high velocities. The appellation "Gauss gun" comes from Carl Friedrich Gauss, who formulated mathematical descriptions of the electromagnetic effect used by coilguns. Coilguns are often mistakenly called railguns by many sources, and while they are similar in general concept (that is, a magnetic gun), they differ in operation, as a railgun accelerates projectiles down two parallel conducting rails. Coilguns are essentially identical to mass drivers, though on a smaller scale. Kristian Birkeland is commonly considered the inventor of the electromagnetic coilgun, for which he obtained a patent in 1900. The attempts to turn his invention into a usable weapon failed, and the idea was more or less forgotten for many years.Many hobbyists use low-cost rudimentary designs to experiment with coilguns. One such design would incorporate the use of photoflash capacitors from a disposable camera as the energy source, and a low inductance coil to propel the projectile forward.
The power must be delivered to each successive electromagnet with precise timing, due to hysteresis. Electromagnets take some time to reach full strength after voltage is applied , so the power supply must start before the shell has reached a particular magnet. The same is true after the power is turned off, and if the shell is on the "far side" of the magnet at that time, the magnet will continue pulling on it, slowing it down. One obvious solution would be to trigger the magnets long before the shell reaches them, but because magnetic force drops off with the square of distance (that is, very quickly) too much power would be lost with such a solution. For this reason most coilguns that use more than one magnet include some sort of electronic timing device for powering the magnets, one that can be adjusted for various parameters such as power of the shot, and the mass of the shell. The gun starts with all of the magnets turned on, and then turns them off one by one before the shell reaches them. One advantage of the coilgun over the railgun is that it can be made arbitrarily long. This has a number of side effects, but the main one is that the acceleration can be much slower over a longer length, meaning that the power needed in any one section of a coilgun is much lower. However this advantage is offset by the cost and complexity of the switching system needed to supply a longer gun.
Electromagnetic (EM) railguns or coilguns, also known as Pulsed-Power EMguns, are expected to launch light projectiles(KE, up to 5 kg) with 30-60mmin diameter, at unprecedented hypervelocities between 4000-8000 m/sec (30-60MJ). Contrary to conventional SP guns, the EM pulse travels at near the speed oflight (@ 186K miles/sec) and thus provides propulsion means inherently immune to natural limits of gas expansion. At these extremely high velocities, EM guns are unsurpassed, being more efficient than any other type of existing gun. EM railguns operate on the sameprinciple as ‘linear’ electric motors. The barrel consists of two (or more?) highly conductive rails with the projectile positioned between the latter and enclosed in the leading bore. As high current is supplied to the rails, a strong magnetic field is created by the electric arc across the rails which accelerates the projectile down the barrel. Hypervelocities appear to improve the effectiveness of kinetic energy projectiles against some types of homogenized armor but may not do so against others. It increases with velocity against explosive reactive armour if the projectiles are segmented, but will not increase against a variety of complex composite armors. The benefit of hypervelocity projectiles is obvious against RHA, missiles, helicopters, and low flying ground support aircraft, but requires further development for full adaptation to antiarmor complex applications. Considerable size, low energy density, and a multitude of unresolved technical problems indicate that EM guns still have a long way to go before they could become practical enough to be incorporated as the main gun armament in a relatively small, highly mobile weapon system such as the FCS. Because of the high secrecy associated with outer-space military weapons applications, no recent information has been published nor released about EM guns and their applicability. Many in the research community believe that significant technical breakthroughs have been achieved over the last ten years, but havenot become public knowledge.
There are still fundamental issues that must be investigated, researched, and developed before EMguns could become a practical proposition, among them: 1) Material ablation effects due to extremely high friction with the atmosphere at hypervelocities could cause the projectile to burn unevenly,resulting in substantial degradation of its ballistic trajectory accuracy,velocity attenuation, and subsequent reductionin penetration effectiveness. Materials, demonstrating low ablation must also possess high mechanical strength(hard to find); 2) Interface repulsive force between the projectile and the accelerators(rails or coils) must be determined to quantify the critical implications in safety, structural integrity and launch reproducibility; 3) Selection of gun barrel material for overall weight reduction while maintaining adequate resistance to ablation and durability; 4) Accelerationsof 106 g’s produce previously unknown and unique material problems (e.g. vaporization) with critical implications for both lethality and accuracy. [At hypervelocities, materials behave like liquids, requiring the implementation of hydrodynamics, gas thermodynamics, and compressible fluid dynamics to representthe impact interaction between thepenetrator and its target]; and 5) Reductionof electrical equipment size (e.g capacitors, compulsators, and homopolar generators) and development of coaxial inductors and first-generation, barber repetitive opening switches operating atextremely high-current; 6)Railguns exhibit difficulty with initial acceleration.To avoid excessive heat and stress associated with the initial projectile launchphase, a method of gas-injected running startfor initial acceleration (up to practically1 km/sec), prior to the projectile entering the railgun breech, has been developed.This method introduces mechanical complexity and additional undesired logistic burden. Nevertheless, in spite of immense technical challenges, especially extensive pulse and power requirements for extremely short periods of time, and virtually nonexistent infrastructure, EM gun technology is the preferred long-term ultimate choice.
3.1.5) PLASMA IMPULSE GUNS:
Railguns and coilguns have been proposed, as these systems could provide much greater velocities and removed the need for dangerous explosive; but such systems require space-consuming generators and capacitors and have technical problem related to their mechanisms of action. A railgun is limited only by the amount of power available, but projectiles faster then 6000m/s would be seriously hindered by atmospheric friction, putting a upper limit on projectile speeds. An intermediate solution is the use of electrically-enhanced explosives or plasma impulse guns. They would use electricity to vaporize or even turn into plasma an inert or explosive liquid that would propel a bullet. One such type is the Plasma Thermal Gun (Shown below), which utilizes the electrothermal energy obtained from vaporizing a metallic material, creating a pressure wave of sufficient magnitude to cause a projectile to accelerate to ballistic velocities.
Fig.7. Schematic Diagram of the Plasma Thermal Gun.
Gas velocities and pressures much higher then conventional explosives could be achieved resulting in greater bullet velocities, inert liquids or less-combustible explosives could be used. An electrically-enhanced explosives cannon could achieve speeds of 3000m/s.
All the above weapon systems are still in their infancy; but its probable thaxt their drawbacks can be removed for their reliable use in the Future Comat Vehicles.

3.2) ARMOUR RESEARCH:
Undoubtedly, proper attacking and destructive potential, is one of the most essential requirement of a modern battle tank. But, a battle tank of a particular developed nation won’t be the only dominating weapons system on the battlefield.It will also have to encounter the threats from its opponents’ battle tank,more or less advanced in technology to the country. Thus, strong competition prevails in the battlefield. So, beyond having adequate firepower capability and proper fire control systems, upgradation of the protection levels of the tank is equally important for improved survivability aspects. This protection can only be provided by the tank armour.
Most of the modern armoured fighting vehicles are manufactured of hardened steel plate, or in some cases aluminium. These vehicles consist of the rolled homogeneous armour. Most armoured vehicles are best protected at the front, and their crews always strive to keep them pointed in the likeliest direction of the enemy. The thickest and best-sloped armour is on the glacis plate and the turret front. The sides have less armour and the rear and roof are least protected.Taking a glimpse to World War II,American Sherman tank crews found the German Tigers to be practically invulnerable from the front.But inspite of the good front protection,still today, tanks are vulnerable to specialised top-attack missile weapons and air attack.
In part to combat the threats of handheld anti-tank weapons and other advanced weapons system, as well as to investigate ways of maintaining protection levels while reducing weight, many countries,especiallyU.S. and U.K., are investigating a series of advanced armour technologies.Its light weight can increase strategic deployability by allowing two to three vehicles per cargo plane and increasing the number of vehicles, that can be transported by ship,rail or highway. Now-a-days, armours,besides being a protective shield of the tanks,are also thought to be the induced warriors of the modern battlefield, having the capability to fight against the dreadful anti-tank ammunitions and warheads. Most of the modern day battle tanks are equipped with Reactive armours, that react efficiently,in some way,to the impact of a weapon to reduce the damage done to the vehicle being protected. The most common type of reactive armour is by far Explosive Reactive Armor (ERA), but other types include Self-Limiting Explosive Reactive Armor (SLERA), Non-Energetic Reactive Armor (NERA), Non-Explosive Reactive Armor (NxRA), and electric reactive armor. Unlike ERA and SLERA, NERA and NxRA modules can withstand multiple hits, but a second hit in exactly the same location will still penetrate.So, basically all Reactive armours can be defeated with multiple hits in the same place, employed in tandem-charge weapons, which use two or more shaped charge explosions in rapid succession. ERA tiles are used as add-on armour to the most vulnerable portions of an armoured fighting vehicle, typically the front of the hull and the front and sides of the turret. They require fairly heavy armour on the vehicle itself, since the exploding ERA would otherwise damage the vehicle and injure or kill the personnel inside. Usually, ERA is not mounted on the sides or rear of a vehicle, since the underlying armour is not as heavy on those parts. Exploding ERA also poses a danger to friendly troops in close proximity to the vehicle. Though it was once quite common for a dozen or so infantrymen to ride on the outside of a tank's hull, this is not done with ERA-plated vehicles—for obvious reasons. Considering all the above disadvantages of the present day reactive armours, military scientists are recently trying for other alternatives . Thus, at present, research is going on to develop the following types of armour shields:
1.Electromagnetic Armour.
2.Electric Armour.
3.Active Armour.

3.2.1) ELECTROMAGNETIC ARMOUR:
This is a technology,still under development .Its used to defeat shaped charge warheads.The armour uses a massive magnetic charge to break apart and disperse shaped charge jets. One proposed system uses a sensor net of fibre optics, covering the vehicle. An impacting warhead will interrupt the flow of light through the fibre optics, registering a hit. An automated system registers the location and sends a signal to energise a powerful electric coil located behind the armour.The spiralling electrons in the coil give rise to an intense magnetic field that interacts with the particles within the shaped charge jet. Although shape charges generate enormous forces by travelling at up to 9 km/s, the stream maintains its penetrating power over a very short, and specific, distance. The magnetic field "pinches" the charge jet, making it unstable and dispersing its force so the warheads penetration power is significantly degraded. Figure below demonstrates the working of an electromagnetic armour.
Fig.8.Diagram showing the working of the electromagnetic armour.
Other proposals use a layered electrified armor underneath standard armour. Penetration of the armor by a shaped charge results in a massive discharge of electricity powered by a capacitor array in the tank. The electricity discharges into the incoming jet of explosive gas/plasma and this disrupts its flow and direction by adding extra heat and electric_charge. The electric discharge can also vaporize the molten metal used in some shape charges to increase penetration.
Using such systems could reduce main battle tanks from their current scale-tipping weight of 70 tons, down to a more manageable 20 tons, while providing superior protection. This would also have strategic implications. Current U.S. heavy armour divisions can take months to move from the continental United States to locations around the world. A lighter MBT could make deployment faster.
3.2.2) ELECTRIC ARMOUR:
Recent research has produced the idea of Electric Reactive Armour, where the armour is made up of two electrically charged plates separated by an insulator. When an incoming body penetrates the two plates and closes the circuit, a high current will flow through the penetrator, attempting to vaporize it, significantly reducing the resulting attack. It is not public knowledge whether this is supposed to function against both KE-penetrators and shaped charge jets, or only the latter. Rocket Propelled Grenades (RPGs) are the most prolific ground launched threat to British and Allied armoured fighting vehicles world-wide. To combat this very real and dangerous threat the Defence Science & Technology Laboratory, Dstl, has developed an 'Electric Armour' that reduces the effect of impacts by such projectiles to almost zero, and will ultimately save the lives of soldiers. Picture shown below demonstrtates the New Age Electric Armour - Tough enough to face modern threats.
Fig.9 Showing encountering power of the electric armour system.
Dstl scientists have developed a revolutionary Electric Armour system which can resist attack by RPGs or other shaped charge weapons whilst remaining of a practical weight and size for armoured vehicles to carry. A recently demonstrated system, consisting of bulletproof metal plating, insulation, power distribution lines, and storage capacitors weighs a mere couple of tonnes, but has a protective effect equal to carrying an extra 10-20 tonnes of steel armour. But this technology is still in its infancy and has not yet been introduced on any operational platform( battlefield).

3.2.3) ACTIVE ARMOUR SYSTEMS:
These systems are proposed to act more or less like the tank armament systems, thus adding great destructive potential to the battle tank. They form the sole warriors in the tank system, acting as the vehicle’s exoskeleton. They protect a tank or other armoured fighting vehicle from incoming fire before it hits the vehicle's armour. There are two general categories: soft kill systems, which use jamming to confuse a missile's guidance system, and hard kill systems, which attempt to detect and destroy incoming projectiles.
Active Protection Systems commonly consist of an array of soft- and hard-kill techniques. Soft-kill methods, similar to Electronic Counter-Measures (ECM) in aircraft, seduce and confuse an incoming missile, by using decoys, smoke and electro-optical signals, infrared or laser jamming. Other concepts which include "Hard-kill" means, are designed to intercept and destroy the incoming projectile or missile before it hits its target. Countermeasures include fragmentation charges, steel bars, high pressure shock waves that will destroy the threat, destabilize or disrupt it flight path, or divert it from its course. The optimal implementation of APS should be "design-dependent" thus, make it adaptable to tracked or a wheeled vehicle as well as fixed positions. Most of the currently available systems are, however, too heavy and are therefore suitable only for AFVs with weight class over 25 tons. (In photo - US Army M-1A1 equipped with the active protection system, in Iraq, 2003).

Fig.10 Showing Active Protection System on M1-A1 Abrams.

3.2.3.1) SOFT KILL SYSTEMS:
Soft kill systems were unsuccessfully deployed by Iraq in the Gulf War. These were essentially strobe lights fitted to Iraqi tanks, which misguided the guidance beacon on the back of a TOW missile. The multinational force was aware of their use, and adjusted the frequency of their guidance systems so they wouldn't be confused. Russia is the major contributor to the existence of this system. A soft kill system, currently in service, is the Russian Shtora, deployed on Russian and Ukrainian tanks. During the International Defense Exposition (IDEX) held in Abu Dhabi in 1995, the system was shown fitted to a Russian MBT. The first known application of the system is the Russian T-90 MBT that entered service in the Russian Army in 1993.
It is an electro-optical countermeasures suite, designed to disrupt the laser target designation and rangefinders of incoming ATGMs. It is an electro-optical jammer that jams the enemy's semiautomatic command to line of sight (SACLOS) antitank guided missiles, laser rangefinders and target designators. It is most effective when used in tandem with a hard kill system such as the Arena (active countermeasures system).
3.2.3.2) HARD KILL SYSTEMS:
Hard kill systems are activated when a millimetre-wavelength radar or other sensor detects an incoming projectile. In considerably less than a second they launch a counter-projectile in an attempt to physically damage or destroy the incoming round. In these systems also, Russia is a great contributor. Examples of the previously used systems include the TROPHY Active Protection System, Drozd, Arena and Zaslon.
One of the most important active hard kill systems prevalent today is the Arena Active Protection System (APS). It is an active countermeasure system developed at Russia's Kolomna-based Engineering Design Bureau to provide anti-missile defense for T-90 tanks. Arena was designed partly in response to vulnerabilities in T-80 and other tanks, discovered during fighting in Chechnya in the 1990s. It is intended to help protect a tank from light anti-tank weapons and ATGMs, including those with top-attack warheads.It uses millimeter-wavelength radar to detect timed to detonate immediately in front of the target.Different countries are trying to install these systems gradually, but most of them are limited by the huge cost of installation( roughly $300,000).
Future research should be aimed at not only the traditional survivability but also at the non-traditional survivability of the tank. In addition to ballistic protection of the tank, the armour should also be designed for good signature management and other related countermeasures.
3.3) POWER PLANT RESEARCH:
The battle tank’s power plant is a part of the power train, consisting of the tank propulsion system, transmission and steering system. The prime mover of the battle tank is the engine(also known as the power plant of the tank).The tank's power-plant supplies power for moving the tank and for other tank systems, such as rotating the turret or electrical power for a radio.
Tanks fielded in WWI all used petrol (gasoline) engines as power-plants. In the Second World War there was a mix of power-plant types used; a lot of tank engines were adapted aircraft engines. As the Cold War started, tanks had almost all switched over to using diesel, improved multi-fuel versions of which are still common. Starting in the late 1970s, turbine engines began to appear.
All modern non-turbine tanks use a diesel engine because diesel fuel is less flammable and more economical than petrol. Some Soviet tanks used the dark smoke of burning diesel as an advantage and could intentionally burn fuel in the exhaust to create smoke for cover. Modern tank engines are in some cases multi-fuel engines, which can operate on diesel, petrol or similar fuels. Gas turbine engines also have been used as an auxiliary power unit (APU) in some tanks.
3.3.1) EXAMPLES OF POWER PLANTS IN MODERN TANKS:
Gas turbine engines are the main power plant in the Soviet/Russian T-80 and U.S. M1 Abrams. The M1A2 was nicknamed “Whispering Death” for its quiet operation. T-80 was dubbed as the “Flying Tank” for its high speed. Some of the models of the M1 have a small secondary turbine engine as an APU to power the tank's systems while stationary, saving fuel by reducing the need to idle the main turbine. T-80 tanks are commonly seen with large external fuel tanks to extend their range. Russia has replaced T-80 production with the less powerful T-90 (based on the T-72), while Ukraine has developed the diesel-powered T-80UD and T-84 with nearly the power of the gas-turbine tank.
3.3.2) RELATIVE ADVANTAGES AND DISADVANTAGES OF THE
USED ENGINES:

Gas Turbines are comparatively lighter and smaller than diesel engines, at the same level of sustained power output (the T-80 was dubbed the Flying Tank for its high speed).However they are much less fuel efficient, especially at low RPMs, requiring larger fuel tanks to achieve the same combat range. Because of their lower efficiency, the thermal signature of a gas turbine is higher than a diesel engine at the same level of power output. On the other hand the acoustic signature of a tank with a muffled gas turbine can be quieter than a piston engine–powered one. A turbine is theoretically more reliable and easier to maintain than a piston-based engine, since it has a simpler construction with fewer moving parts. In practice, however, those parts experience a higher wear due to their higher working speeds. The turbine blades are also very sensitive to dust and fine sand, so that in desert operations special filters have to be carefully fitted and changed several times daily. An improperly fitted filter, or a single bullet or piece of shrapnel can render the filter useless, potentially damaging the engine. Piston engines also need well-maintained filters, but they are more resilient if the filter does fail.Like most modern diesel engines used in tanks, gas turbines are usually multi-fuel engines.

3.3.3) PROPOSED ALTERNATIVE PROPULSION SYSTEMS:
The turbine engine long ago supplanted piston engines in both military aircraft and ships, but whether it will be successful in tanks has yet to be seen. Miitary Researchers are now wanting to fulfill the requirement of the Future Combat System. They desire to significantly lessen the dependency on conventional fossil fuels, thus making the FCS more independent and capable of operating over long periods of time without resorting to periodic maintenance and logistical support. This requirement is extremely difficult to satisfy, and necessitates a dramatic departure from any conventional power sourcepresently in use. The FCS power pack is configured for an all-electric front drive installation. Electrical propulsion for mobility applicationsis widely recognized today as the wave of the future. Researchers are also proposing for reducing the thermal signatures as well as the acoustic signatures of battle tanks, which are not firmly established with diesel as well as gas turbines. Also, increased compactness is another requirement.
Many types of alternate power-plants such as fuel cells have been experimented with. One proposal is to use a diesel-electric or turbine-electric series-hybrid. These power plants would provide power by spinning a generator that would provide electricity to electric motors mounted inside the wheel hubs. In conjunctions with electric batteries or ultracapacitors for storing excess and recaptured energy such a system would be far more fuel efficient then traditional tank power plants while providing some advantages in maneuverability and performance. A system of this kind could be more rugged and damage sustaining with the use of multiple engine/generators and electric motors. Such a power plant could also provide electricity for energy weapons and defense systems like the ones mentioned above. Other types of power plants proposed are-
1.Solar Power Propulsion Plants.
2.Nuclear Power Propulsion Plants.
3.3.3.1) FUEL CELL PROPULSION SYSTEM:
A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i.e. it produces electricity from an external fuel supply of hydrogen and oxygen as opposed to the limited internal energy storage capacity of a battery. Fuel cells are often considered to be very attractive in modern applications for their high efficiency and ideally emission-free use, in contrast to currently more common fuels such as methane or natural gas that generate carbon dioxide. The only by-product of a hydrogen fuel cell is water vapour.
Besides being applicable as useful power sources in remote locations, such as spacecraft, remote weather stations, military researchers have proposed these cells for use in certain military applications-including battle tanks, particularly because of the following military benefits: 1.A Fuel cell system running on hydrogen can be compact, light weight and have relatively few moving parts, which is required for improved maneuverability, 2.Endurance of the tank is enhanced as effective mileage is provided, 3.Quiter tank operation is provided, much needed advancing undetected by the enemy,with reduced acoustic signature, 4.Lower maintenance is required for the lack of moving parts, 5.Its practically a emission-free propulsion system, which is very much required for reducing the thermal signatures of the tank, 5.Reduced logistics are required.
Bernard I Robertson, Senior Vice President, Research and Regulatory Affairs has said, "This unique technology could have great benefits for the military: in particular, it is nonflammable, greatly improving safety in battle zones, and the main ingredient can be transported as a dry powder, dramatically reducing the enormous logistical demands of fueling our military in advanced battle settings. In addition, the greater fleet fuel efficiency would greatly reduce the amount of fuel used by our armed forces--fuel that can cost hundreds of dollars per gallon to deliver to the battlefield. And this technology produces zero smog-forming and greenhouse gases, contributing to a cleaner environment. Finally, sodium borohydride has the potential to reduce or eliminate our dependence on oil for our transportation needs." To cite an example, the U.S. armed forces have expressed interest in alternative-fuel vehicles in order to stretch the military's mobility into the future with improved fuel economy and range. Benefits include a decreased dependency on oil which significantly decreases cost of operation and increases the range and reach of individual task forces.
Supporting Special Forces during extended operations requires lots of power. Thirteen BA-5590 batteries weighing more than 29 lbs and costing $100 each are currently required to support a typical 72-hour deployment. The US Army is evaluating the use of inexpensive, injection-molded fuel cell technology formed into a common BA-5590 form factor, to power SOF PRC-117 field radio, resulting in a weight saving of over 13 lbs and decrease its cost by at least 50%. Figure below demonstrates the fuel cell power unit which is thought of to be installed in the tank.
Fig.11 Showing the Fuel Cell Power Unit.
But again, much frustrations have also taken place due to the use of these cells due to:
1. The hydrogen typically used as a Fuel is not a primary source of energy: it is only an energy carrier, and must be manufactured using energy from other sources. Some critics of the current stages of this technology argue that the energy needed to create the Fuel in the first place may reduce the ultimate energy efficiency of the system to below that of the most efficient gasoline internal-combustion engines. Thus, the fuel cells lack competition in this respect to the diesel engines also.
2. Because Fuel cells have a high cost per kilowatt, and because their efficiency drops with increasing power density, they are usually not considered for applications with high load variations. Large variations of load occur in battle tanks during normal conditions and also during war.Thus fuel cells are unable to provide sudden changes in load demand.
3. In particular, they are not suited for energy storage systems, unless weight is a major consideration. An electrolyzer and Fuel cell would return less than 50 percent of the input energy, while a much cheaper lead-acid battery might return about 90 percent.
4. There is concern, however, about the energy-consuming process of manufacturing the hydrogen, which may still generate pollution and still requires either fossil fuel, nuclear power generation, or as yet undeveloped alternative generation. In this regard, hydrogen fuel technology itself cannot be said to reduce fossil fuel dependence.
5. However, another environmental problem faced by all types of hydrogen fuel cells has been pointed out in a paper published in Science magazine by a group of Caltech scientists. They note that if hydrogen fuel cell usage becomes widespread enough to replace gasoline internal-combustion engines, small amounts of hydrogen leaking from storage containers and pipelines will have a detrimental impact on the Earth's ozone layer.
6. Finally, roughly 70% of all electricity produced in the United States comes from Coal. The problem is that coal is a relatively dirty energy source. If electrolysis (a process that uses electricity) is used to create hydrogen using energy from power plants, it is essentially creating hydrogen fuel from coal. Though the fuel cell itself will only emit heat and water as waste, the problem of pollution is still present at power plants.
Since the disadvantages of these cells in military use outnumber the advantages, researchers are discouraged to use these cells. They have realised that a better performance of the armoured fighting vehicles can occur from the hybrid(diesel and electric power sources combined) engine systems.
3.3.3.2) HYBRID ELECTRIC PROPULSION SYSTEM:
A number of land vehicles use a diesel-electric powerplant for providing locomotion. A diesel-electric powerplant includes a diesel-electric connected to an electrical generator, creating electricity that powers electric motors. The most well-known vehicle to use this technology is the locomotive, used for pulling or pushing trains. Diesel-electric powerplants have also been used in submarines and surface ships. Vehicles using a diesel-electric power system can be considered as a class of hybrid electric vehicles. Now they are also being proposed for use in military vehicles as well.
Defence Advanced Research Projects Agency (DARPA) is embarking upon anew venture to find a contractor teamable to inexpensively develop and demonstrate the capabilities of a highly-effective, Hybrid Electric Power System(HEPS) for generation and storage of electricity. HEPS is intended for automotive applications as a prime-mover in advanced combat vehicles (FCS and the Future Scout Cavalry System - FSCS).In essence, HEPS is comprised of a diesel engine or gas turbine directly coupled to generators to produce electrical energy for storage and subsequent use by the vehicle systems.DARPA has announced its intention to invest more than $40 M(!) to develop and test the HEPS over the coming few years.
A Hybrid Electric Drive, an 8x8 wheeled vehicle has been demonstrated following several years of field testing, accumulating over 4,200 km of road and cross-country testing.(Picture shown below).
Fig.12 Showing the interior installation of the hybrid system.
A first hybrid-electric tracked armored vehicle(Shown below),developed by the U.S. Army’s National Automotive Center and BAE Systems (formerly United Defense) was the hybrid-drive 15-ton M-113 prototype. The vehicle's battery power was used to provide transient power needs, on acceleration, steering and climbing. When stationary, the vehicle can generate about 200 kilowatts of electricity and function as an auxiliary power unit.
Fig.13 Showing the first tracked vehicle with hybrid engine.
Competing teams will develop and demonstrate an integrated HEPS for a 15-ton vehicle (e.g. FSCS), but they will also be required to demonstrate, by computer simulation and computer virtual modeling, that a more powerful version of the HEPS could be integrated into a 40-ton vehicle (e.g., FCS). Nonetheless, though same basic technology could be used to power the FCS, it is not in accordance with the requirement for simplified and reduced logistics. Integrated HEPS are more efficient, and have improved performance compared to contemporary diesels or turbine-based power packs. The internal combustion engine in a hybrid type is much smaller, lighter and more efficient than the one used in a conventional tank, because the engine can be designed for an average power demand only, rather than peak power demand. Also with proper regenerative braking, much of the kinetic energy is conserved, which helps the motor to charge the battery. Thus, these engines have better efficiency in stop and go missions, although less in long duty periods. The advantage is that the electric motors get the better storage capacity for offroad maneuverability- in gradients especially when too much mechanical stresses can be induced in conventional diesel power plants. Thus frequent charging of the battery from outside is eliminated. They operate with less noise and with reduced thermal signature, thus improving survivability. With hot noisy diesel engines turned off, the batteries, ultracapacitors or fuel cells of hybrid provide silent watch power in stationary tanks to avoid detection. These engines can provide stealthy sources of power for battlefield sensors, weapons, command and fire control systems, laser range finders, etc. Thus, they provide exportable power to run other equipments. It has been estimated by the United States that the hybrid electric wheeled Future Combat System can travel at the rate of 5 miles per hour for about 30 minutes, using electric power only. A hybrid electric version of the MII3 APC created by United Defence L.P. outperformed the conventional M113 in many areas, in an experimental setting. Thus they provide exportable power to run other equipments. According to the Defence Science Board, fuel takes up about 70% of the total logistic burden tonnage in an armoured fighting division. The Army expects that the hybrid-electric Future Combat System is likely to reduce the fuel consumption by about 75%.
It remains to be seen whether integrated HEPS will come out less costly in production and deployment than contemporary power packs. Attempting to capture the best of two worlds, HEPS seem to be more applicable, as a near-term solution, to the lighter FSCS and similar vehicles, though less so for the longer-term, heavier FCS. Currently no battle tank uses this principle for movement, but it's quite appropriate to train the turret and/or guns with electric motors powered by diesel or turbine APUs.
The only problem, HEPS is still going to require diesel or turbine fuel for its operation, and would add a piston engine or a gas turbine, in addition to a sophisticated electrical power generating system, to worry about.

3.3.3.3) SOLAR POWER PROPULSION SYSTEM:
Its been pondered as a possible long term energy source solution for the Future Combat System.
Solar energy is considered by many as an ideal energy source. It is clean; it produces no pollution and there are none of the nuclear residual radioactive wastes that make nuclear energy so unpopular in the public eye. It is practically unlimited, so it will still exist in abundance long after fossil fuel reserves become scarce, sometime during the next century. And best of all, solar energy is free,short of the cost of harnessing it for humanconsumption. A Solar Power Satellite System(SPS) is placed in a geostationary orbit (36,000 km) above the equator,similar to the orbit being used for communication satellites. The SPS is so positioned in space that it revolves at the same rate as the Earth spins, being relatively fixed to the equator, and can intercept at least four times as much solar energy as the sunniest spot on Earth. The SPS intercepts unobstructed sunlight (noclouds, bad weather, or darkness inspace), converts it into microwaves(short-wavelength radio waves) and beams them back to collector arrays on Earth where they could be convertedwith high efficiency into electricity.

Fig.14 Showing a photovoltaic cell, which make up the solar panel in the SPSS.
Depending on its size, the SPS could deliver thousands of millions of watts, practically in a continuous manner. DOE concluded that it was feasible to construct a fleet of 60 solar power satellites, the first of which will be in operation in 2010 and the last by 2040.A SPS could reach a mass of about 50,000 tons, but it is weightless in space.Solar cell arrangement is preferred, becausethere are no moving parts to malfunction,and the use of solar cells in space is already well established. Solar cells, made of silicon (or gallium arsenide forbetter efficiency) convert sunlight directlyinto electricity. Remotely-controlled and operated ‘space robots’ could construct the lightweight structures which support the array of solar cells. Whether the SPS uses turbines or solar cells, the electricity generated will be converted into microwaves by devices known as Amplitrons (also Klystrons) and then beamed to Earth at an area of limited diameter. At a wavelength of 10cm (2450 MHz) this type of microwave radiation passes through the atmosphere virtually unabsorbed. At the ground, receiving arrays termed Rectennas, installed on the FCS as shown, will collect the microwaves to convert them very efficiently (83+ %) into electricity. The rectennas will consist of panels studded with T-shaped aerials linked to rectifying devices known as Schottky barrier diodes, which convert the microwave beam back into electricity. Picture below demonstrates the use of the Rectennas in powering other devices.
Fig.15 Showing the mode of use of the solar collectors, installed on the battle tank.
One of the arguements against beaming power to Earth is that microwave beam radiation might damage humans. This problem could be mitigated by using a beam that is stronger in the center, but it must be very accurate. The accuracy of beaming could be much improved with the aid of the Global Positioning System (GPS), which is also satellite-based. Any realistic assessmentof the dangers of power satellites must be balanced against the pollution from fossil fuels, and the waste from nuclear reactors. The SPS concept may resemble “StarWars” and frontier-of-science type of technology, but successful and promising experiments have been conducted in the past that validated the feasibility of such an idea. Using its Global PositioningSystem (GPS), each individual FCS could identify its definite location so that it could receive the transmission with high accuracy and, better yet, while on the move. Once the transmitted energy has been absorbed by the FCS, it will be converted into electrical energy and stored in high-density energy to the various “consumers” (EMgun, fire control system, laser gun, prime-mover, etc.). The FCS could also receive electrical energy from a dedicated “refueling” vehicle (generator) and by physical connection to another FCS that could share some of its own electrical energy. Admittedly, there is a vast array of problems yet to be solved in order to harness this type of energy source for automotive applications. To mention just a few :- The rectennas on the FCS must be small to accommodate its limited size, and still be efficient. The safety hazard of exposure to microwave radiation must be eliminated or reduced to controllable and acceptablelevels. Radio noise disruption over a wide range of frequencies, and detrimental ionospheric and atmospheric effects, must be mitigated. The beaming process must be sufficiently accurate to hit a single FCS, or a group of them, in a pre-planned rendezvous location, and recharge them within a reasonable duration. The high efficiency of microwave power transmission and reception is crucial to the economics of placing the SPS in space for practical military applications. In conclusion, the authors realize that one may challenge the feasibility and practicality of such an approach to their fueling problem. It stands to reason that, if we are to be independent from conventional fossil fuels, we must use a different source of energy.
3.3.3.4) NUCLEAR ENERGY PROPULSION SYSTEM:
Nuclear energy is also conceived of as a prime-mover energy source. The energy produced by a nuclear reactor is released by the fission of atomic nuclei in a controlled and self sustaining manner, and appears as heat, which is then converted to electrical energy by using conventional turbine generators.As an example, the Fast BreederReactor2 (FBR) now under active development, uses fast neutrons produced by fission without slowing them down, such as in a conventional Thermal Reactor(TR). The fuel used has a higher concentration of fissile material (plutonium-239and uranium-235) with the high concentration resulting in a much smaller core. Molten sodium or high-pressure helium are used as coolants. In essence, the FBR generates more fuel than it burns, so it could continuously operate for extended periods of time. By processing the burned fuel, it is possible to use up to 60 pecent and more of the energy stored in the uranium, as opposed to just a few percent with thermal reactors. The energy potentially available from the fissioning of uranium and thorium in FBRs is at least a few orders of magnitude greater than that of all fossil fuels sources combined. The emergence of nuclear power as aviable energy source for automotive military applications comes at a time when additional environmentally acceptable sources of energy for civil and military consumption are sorely needed to meet continued rapid increases in demand Despite its undeniable potential, the authors decided to reject this alternative up front on both environmental and political grounds. It is primarily because of the inherent difficulties and safety hazards involved in dealing with radioactive radiation in peacetime, accidents and war, demilitarization problems associated with discarding radioactive products and radioactive residual materials. Furthermore, there are insurmountable difficulties in cooling the nuclear reactor and ‘purifying’ the working liquid when the only available coolant in abundance is ambient air (a poor heat conductive substancewith a much lower heat transferefficiency than water), rather than the unlimited sea water supply commonly used in submersible and surface naval applications. The reactor under armor must be ruggedized, and the control rods— which regulate the speed of reaction— must be stabilized to account for the jagged motion over typical cross-country terrain. In addition, the nuclear reactor and its auxiliaries — its insulation, cooling, pumps, controls, monitoring and redundant safety devices — must all be made inexpensive to produce in order to make any economical sense. Present commercial and military nuclear applications are considered unpopular because they contradict the current trend towards diminishing civil nuclear applications, and in particular, the trend toward banning the proliferation of nuclear weapons.
This option may be regarded as feasible if there was a safe, practical, and economical way to neutralize radioactive radiation and demilitarize residual nuclear materials while preserving the natural environment. The above systems bear a disadvantage with respect to installation in a tank. But the researchers have realized that even a more potent synthetic fuel is not going to provide the desired level of independence from the burden of the logistical “umbilical cord”. Compact, reliable, and economical diesel engines have probably reached their peak performance. Turbocharging, recuperation, intercooling, high-temperature resistant materials (e.g. ceramics) and combustion control, in addition to some emerging technologies like variable compression ratio piston engines, adiabatic engines, employing ceramic liners and compound engines, have all contributed to their performance with limited progressive improvements yet to be expected. One way or another, this particular problem of using the alternative sources of power must be addressed sometime in the course of the next century, when fossil fuel reserves become scarce.

3.4) STEALTH RESEARCH:
A battle tank is an offensive weapons system, which has to progress aggressively in the battlefield. So adequate protection facilities are provided and some are being developed to be used in future. But because of the advancement of technology in various countries with regard to the armoured protection systems, its not always possible to save the disability of the tank from the powerful armour piercing weapon systems,now being developed. Thus, besides protection, sometimes hiding of the tank is also required in the battlefield to the maximum extent in order to cheat the enemy detection systems. Most armoured vehicles carry smoke grenade launchers which can rapidly deploy a smoke screen to visually shield a withdrawal from an enemy ambush or attack. The smoke screen is very rarely used offensively, since attacking through it blocks the attacker's vision and gives the enemy an early indication of impending attack. Some smoke grenades are designed to make a very dense cloud capable of blocking the laser beams of enemy target designators or range finders and of course obscuring vision, reducing probability of a hit from visually aimed weapons, especially low speed weapons, such as antitank missiles which require the operator to keep the tank in sight for a relatively long period of time. But the installation of these grenades affect the health of the moving infantry, thus reducing their working capabilities.Thus, such smoke grenades are not used for hiding purposes. Modern technologies, which supports the tank to move through the field in a hidden manner, is known as Stealth Technology.
The concept of stealth itself is not new. Being able to operate without the knowledge of the enemy has always been a goal of military technology and techniques. It covers a wide range of techniques, initially and now often used with aircraft, ships and missiles, in order to make them less visible (ideally invisible) to radar and other detection methods.Radar avoidance technology was first used on a large scale during the Gulf War in 1991. However, F-117A Stealth Fighters were used for the first time in combat during Operation Just Cause in 1989. Since then it has become less effective due to developments in the algorithms used to process the data received by radars, such as Bayesian particle filter methods.
Thus, we see that the concept of stealth has been developed in the fields of air-defence and in ships also. But no such concept has yet been undertaken in the combat field, except in a few armoured personal carriers. Its typically very tough to hide such a big metal block of tank in the moving condition, though some success has occurred during the time when the tank is stationary. Military researchers are now trying to follow the methods for activating stealth to the maximum possible extent in combat enviroment by using the methods of stealth, used in air-defence and in navy. So in order to realise the techniques of hiding the tank, we have to first take a glimpse as how this technology is used in the Air Force.

3.4.1) STEALTH METHODOLOGY IN AIRCRAFTS:

A stealth aircraft is an aircraft which has been designed to absorb and deflect radar signals;these are not completely "invisible" to radar, they are simply harder to detect than conventional technology. In general the goal is to allow a stealth aircraft to execute its attack while still outside the ability of the opposing system's detection. In this context, it can be seen that the tremendous supersonic velocities of most of the fighter jets also gives an added advantage to the non-detectability. Stealth aircraft were most notably used during the Gulf War (1991). To cite a few examples of these stealth aircrafts,first-generation stealth aircraft include the F-117 Nighthawk. Second-generation aircraft include the B-2 Spirit and F-22 Raptor.

The Lockheed F-117A Stealth fighter was the world’s first operational combat aircraft designed to exploit the stealth technology with its unusual shape (Picture shown below).

Fig.17 Showing the world’s first combat aircraft.

If the shape of the external structure of the aircraft is curved, then they have the maximum possibility of reflecting the radar waves towards the radar direction(Picture shown below-Fig.18). In general, the main method, used by stealth crafts to avoid detection,is by using a body shape that deflects radar signals in a direction roughly perpendicular from the radar signals origin, rather than reflecting the signal back to enemy radar sensors (Picture shown below- Fig.19).

Fig.18 Showing the shape of the conventional aircrafts and their detection.

Fig.19 Showing the shape of the stealth aircrafts and their non-detectability.

To a lesser extent, they also use a covering of some type of radar absorbing material. Stealth aircraft are also harder to detect and track via other methods:
1.The normally hot exhaust is cooled by ambient air before leaving the aircraft and partially shielded from below, as a result the infrared signature of stealth aircraft is minimized.
2.Stealth aircraft are painted in dark colors and typically fly at night to make visual identification more difficult.
3.Stealth aircraft are not supersonic, they have no afterburners, and the exhaust nozzles are tuned for low noise rather than peak performance, making them difficult to detect via sound waves.
Application of Stealth Technology in tanks have similarity with that in aircrafts, as both vehicles try to reduce the radar cross section as much as possible. The various ways, applicable to aircrafts, to reduce the radar cross section are:
a) Vehicle shape: It has been known since at least the 1960s that aircraft shape makes a very significant difference in how well an aircraft can be detected by a radar. Another important factor is the internal construction; behind the aircraft skin there is a special structure known as re-entrant triangles. Radar waves penetrating the skin of the aircraft get trapped in this structure, bouncing off its internal faces and losing energy. The vertical and horizontal components of the tail of any conventional craft is set at right angles, which facilitate more radar detection. Stealth aircrafts are arranged in a different manner. Here the vertical component of the tail is set at an angle; in some cases no tail is provided at all. As well as altering the tail, stealth design must bury the engines within the wing or fuselage, or in some cases where stealth is applied to an existing aircraft, install baffles in the air intakes, so that the turbine blades are not visible to radar. The shape of the aircraft must be devoid of complex bumps or protrusions of any kind if it is to be stealthy. This means that all weapons, fuel tanks, and other stores may not be carried on under wing pylons but must be stored internally.
b) Use of non-metallic materials: Nonmetallic components, such as composites may be used for the airframe. The composites used, often contain high amount of ferrites as filling. Composites are transparent to radar, whereas metals reflect waves back to the radar transmitter if the metal happens to be perpendicular to the radar.But certain alloys are there which reflect less electromagnetic radiation than others.
c) Use of Radar absorbing paint: RAM (Radar Absorbent Material) coating may be used especially on the edges of metal surfaces. The RAM coating, known also as "iron ball" paint, contains tiny spheres coated with carbonyl iron ferrite. Radar waves induce alternating magnetic field in this material, which leads to conversion of their energy into heat. Early versions of F-117A planes were covered with neoprene-like tiles with ferrite grains embedded in the polymer matrix, current models have RAM paint applied directly. The aircraft must be painted by robots, because the solvent used is highly toxic.
d) Reducing signatures: Aircraft signatures include infra-red, visible, and accoustis ones. Stealth aircraft need to stay subsonic to avoid being tracked by sonic boom. Some early stealth observation aircraft utilised very slow-turning propellers in order to be able to orbit above enemy troops without being heard. Most stealth aircraft use matte paint and dark colors, and operate only at night. The primary means of reducing the infrared signature is generally to have a non-circular tail pipe (a slit shape) in order to minimise the exhaust area and maximise the mixing of the hot exhaust with cool ambient air. Often, cool air is deliberately injected into the exhaust flow to boost this process. Sometimes, the jet exhaust is vented above the wing surface in order to shield it from observers below.
e) Reducing radar emissions: Infrared emissions and sound aren't the only detectable means on ships or aircraft. The stealth vehicle must not radiate any energy which can be detected by the enemy, such as that of a height finding radar, terrain following radar or search radar. The F-117 uses a passive infra-red system to navigate and the F-22 has an advanced Low Probability of Interception (LPI) radar which can illuminate enemy aircraft without triggering a radar warning receiver response.
f) Plasma stealth is another proposed process that uses ionized gas to reduce the radar cross section (RCS) of an aircraft. Interactions between EM radiation and ionized gas have been extensively studied for a variety of purposes, including the possible concealment of aircraft from radar that plasma stealth theorizes. While the theoretical possibility of reducing an aircraft's RCS by wrapping the airframe in ionized gas flow is not in question, the technological aspects of applying such methods represent considerable challenges. There are many possible means of accomplishing this effect, running from "simple" electrostatic discharges to complex and power-hungry plasma lasers. The Journal of Electronic Defense reported that "plasma-cloud-generation technology for stealth applications" developed in Russia reduces an aircraft's RCS by a factor of 100.
Sukhoi Design Bureau is the main competitor-colleague of Mikoyan-Gurevich Design Bureau. The Bureau was able to create, develop, build, and start testing of the 5th generation fighter in just 10 years comparing to MFIs long 15 years. This aircraft is called S-37 Berkut [Ber-koot]( Picture shown below). The configuration of forward-swept wings combined with canard wings, can be compared to the American X-29. This configuration makes the aircraft more stealthier and maneuverable. The aircraft was designed in such a manner so as to get its stealth capability from the electro - magnetic plasma field around the aircraft. This technology is one of the most closely guarded secrets of the Russian Airforce, at present. N

Fig.20 Showing the aircraft based on plasma stealth.
A number of methodologies to detect stealth aircraft at long range have been developed. Both Australia and Russia have announced that they have developed processing techniques that allow them to detect the turbulence of aircraft at reasonably long ranges (possibly negating the stealth technology).
Passive (multistatic) radars are known to detect stealth aircraft better than receivers connected to the transmitters (active or monostatic radars). In addition, it has been suggested that use of low frequency broadcast TV and FM radio signals as the illuminating source produces a much higher RCS than high frequency monostatic radars as the long wavelengths cause whole structural portions of the targets to resonate. Researchers at the University of Illinois with support of DARPA, have shown that it is possible to build a synthetic aperture radar image of an aircraft target using passive multistatic radar, possibly detailed enough to enable Automatic Target Recognition (ATR).The United Kingdom has announced a system that uses the signals broadcast from the huge number of cellular telephone towers to generate a synthetic picture, although it is not clear if this method is actually practical. Stealth aircraft can also be passively detected from their electromagnetic emissions (terrain-following radar, radio communications, missile guidance communications etc.). Stealth aircraft typically attempt to minimize these emissions (using low probability of intercept radars, satellite communications etc.). The problem of successfully countering stealth aircraft on the battlefield remains essentially unsolved. Although stealth technology has since become less effective, the United States continues to develop stealth aircraft.
Stealth Technology is also applied in naval field. Ships, which employs stealth technology, are constructed in an effort to ensure that it cannot or can hardly be detected by radar. These techniques borrow heavily from stealth aircraft technology, though there are some aspects, such as wake reduction, that are unique to their design.
3.4.2) APPLICABILITY OF STEALTH TECHNOLOGY IN BATTLE TANKS:
Undoubtedly, the size and weight of any battle tank is much more than that of any aircraft. Therefore, hiding the tank from enemy detection system is not a matter of simple research, as tanks always present a bigger target before the enemy than aircrafts. With the urgest need of hiding themselves to suit the modern day conflicts, tanks have been the focus of speculation as to what role and changes they will have. Some have suggested that given the unconventional warfare, that is likely to be seen in the future, more agile tanks are likely to be seen even, if some non-detectable technologies are used. The stealth technology, applied to tanks, is similar to the one used in stealth aircraft,making the tank nearly invisible to enemy radar, by absorbing rather than reflecting radar beams. Some of the radar absorbing materials and paints may be coated on the surface of the armour of the tanks for absorbing the radar signals. A further modification that makes this harder to detect is to give stealth tanks a special color, such as orange, which camouflages it with the desert sands. Non-detectability is also possible by active camouflage. Active camouflage (or adaptive camouflage) is a group of camouflage technologies which would allow an object (usually military in nature) to blend into its surroundings by use of panels or coatings capable of changing color or luminosity. Active camouflage can be seen as having the potential to become the perfection of the art of camouflaging things from visual detection. Theoretically, active camouflage should differ from more conventional means of concealment in two important ways. First but less importantly it should replace the appearance of what is being masked with an appearance that is not simply similar to the surroundings (like in conventional camouflage) but with an exact representation of what is behind the masked object. Second and more importantly, active camouflage should also do so in real time. Ideally active camoflage would not only mimic nearby objects but also distant ones, potentially as far as the horizon, creating perfect visual concealment. In principle, the effect should be similar to looking through a pane of glass making that which is hidden perfectly invisible. This technology is poised to develop at a rapid pace, with the development of organic light-emitting diodes (OLEDs) and other technologies which allow for images to be projected from oddly-shaped surfaces. With the addition of a camera, while not allowing an object to be made completely invisible, theoretically the object might project enough of the background to fool the ability of the human eye or other optical sensors to detect a specific location. As motion would still be noticeable, an object would merely be more difficult to hit, and not undetectable under this circumstance.
But "Stealth Technology" redesigns the vehicle itself to dramatically reduce its observability. The British Researchers have proposed that a stealth tank prototype should have a low center of gravity and should almost crawl on the ground to avoid detection. By virtue of its light weight and size it should be more of a scout vehicle than a main battle tank though.Other invisible tanks that blend into the visual environment by controlling luminosity via the use of flares and diodes are in conceptual stages in the US and UK military. Such a tank would not only be very difficult for the radar to pick up but also for the naked human eye.

Other ideas of a stealth tank have been provided by researchers. Tanks have very noisy heavy armour and smoky diesel engines running loud. If instead of conventional diesel engines, if battery stores are added, to help propulsion of the tanks, then a much quiter operation can be obtained. The batteries once charged, will provide power to much quieter and environmentally friendly electric engines for temporary periods, thus allowing tanks to travel with less chance of detection by the enemy. It has been found that this would be rather useless in flat terrain as deserts or plains, but in areas where the terrain would allow for some cover(woodslands, semi-mountainous regions and the like) the tanks could more easily avoid detection This battery can be charged while the engines are running or through blankets of solar panels installed on the vehicle,during vehicles down time. Potential shortcomings are effected while using electric engines, such as: 1)battery life maybe insuffient to sustain "stealth mode" for prolonged periods. 2)electric engine output would be inferior to diesel, so "stealth mode" would be slower. 3)power generated from primary engines to charge the batteries may drain valuable electricity needed to power targeting and navigation systems.
Stealth can also be provided by a well designed suspension system. An alternative propulsion system, such as four tires on an adjustable suspension which could be lowered down and support the tank instead of the treads, would remove additional noise caused by the creaking treads.
Researchers have also forecasted that stealth would be better effected by employing solar-powered tanks, on which research is going on as mentioned earlier. Giat Industries of France has revealed that several years ago it developed and produced the prototype of a stealth vehicle based on its AMX-30 main battle tank (MBT) (Picture shown below). The project was funded by France's Delegation Generale Armement (DGA) defence procurement agency.

Fig.21 Showing AMX-3O Stealth tank.
Experiments were conducted with an AMX-30 main battle tank whose turret and chassis were enclosed in a Ram covering shaped to reduce the radar cross section, by the methods used for aircrafts, more or less. Also, cold air was pumped between the covering and the hull in order to minimise the vehicle’s IR signature.
Still some researchers believe that this technology might prove useless because a silent running tank moving through open terrain can easily be spotted by it's profile or dust trail from miles around is why I said it would be useless. True, tanks aren't known for their subtley but they have been used in ambushes (which have very high requirements on subtley) against other armour in the past, being able to move silently would insure their chance to move into position for an ambush without the enemy knowing. I would have thought that the sheer size of a tank would make subtlety futile in most situations. Maneuvering even a silent tank in a woodland area is sure to cause one hell of a lot of branches breaking, which in turn creates the noise that one wants to avoid. The output power of the Stealth Electric Power vehicles is only 100Kw, or roughly 134 HP.Obviously, these vehicles are not very heavily armored, and not very fast. So the idea isn't practical for heavy armor yet. The army is currently working on armored vehicles with electric drive, but this is not necessarily for stealth purposes. But , according to the researchers, if this idea is given a decade or so and the technologic advances in battery life, energy output and engine efficiency may even allow the electric engines to surpass current conventional engines, providing good stealth technics. The researchers have thought of a Future Combat System, involving this technology.(Picture given below)

Fig.22 Showing the stealthy based Future Combat System.

The Future Combat System-Tracked prototype will deliver superior survivability through a lightweight composite structure, modular armors, signature control and a survivability suite. It will be highly mobile in all terrains with a reduced logistics burden due to its fuel-efficient hybrid-electric drive, hydropneumatic suspension and band track. The platform allows the user to operate in one of three modes (hybrid, engine-only or battery-only) to provide superior mobility and silent operations. The FCS-T's engine will drive a 300-KW generator to provide high-power, high-speed operation of the vehicle. It will also work in conjunction with batteries, which may be used on their own without the engine runningto power other systems and accessories on the vehicle during silent watch or slow-moving stealth operations. Current prototypes like the British stealth tank prototype, developed alone as the TRACER when the U.S. dropped out of its FSCS part of the project, have pointed out that the future of tanks lies in invisibility rather than invincibility as modern missiles can penetrate any tank's defence.

4) OTHER MISCELLINEOUS RESEARCH ACTIVITIES:
There are some of the additional research activities going on in other fields of interest, such as in tank transmission systems, suspension systems as well as improvement in operating conditions of the night vision devices. Thus, the following activities, noteworthy of mentioning, are-
4.1) MICROPROCESSOR BASED STEERING CONTROL OF TANKS :
The propulsion system is one of the most important limbs of the battle tank. The propulsion includes engine, transmission and steering systems. The driver of the tank has got the control for all these. The steering of high speed track layers is accomplished by applying controlled speed differences between the tracks. It’s a notoriously brutal technique, for which a number of mechanisms have been developed.
When the tank is given an angular motion, every part of the track must rotate about a vertical axis, with the same angular velocity as the tank, thus skidding over the surface. The driver, therefore has to apply a couple, necessary to overcome the resistance to slewing , with the help of the steering mechanism. Resistance to slewing, being large, the effort applied by the driver is also considerable. It causes fatigue to the driver, which will be more intense while driving on a highway, through built-up areas or in deserts, where the resistance to slewing is still higher. Thus, better capability to change speed and direction simultaneously- in other words, significantly better acceleration and deceleration capabilities and improved steering are major parameters for maneuverability. In present tactical scenario, a tank may have to continue advancing and fighting for 72 hours at a stretch. It is,therefore, a requirement to make the drivers’ control as easy as possible to enable him to sustain the stress and strain for a long time. The latest trend to go in favour of a smaller crew in order to reduce the bulk of the tank, has a disadvantage of putting extra work on the rest of the crew in terms of observation and scanning of the battlefield. The driver also cannot contribute maximum to this if he is too busy with his controls.
The microprocessors, though may be a source of complexity and costly, can help in reducing the driver’s effort considerably by making the steering control easier and transmission semiautomatic or automatic. It is certainly true that for some tasks, electric systems out perform human operators- their reaction time is fast, their attention does not wander and they can perform complex mathematical computations that would battle most soldiers. Thus, microprocessors can be used alone in a very competitive arena of armoured combat. It is most persuasive to the designers of military vehicles for reduction in crew workloads. The microprocessor contols different operations with the help of a hardware and a software. The hardware consists of
a)A microprocessor.
b)Two sensors for sensing the positions of the steering sticks and converting them into digital output.
c)Two comparators and one sensor for sensing the engine speed and comparing them with prefixed values.
d)Three stepped motors with drive units for controlling valves.
e)Choice of AUTO/MANUAL mode.
The software involves:
a)Getting digital equivalent as input from steering sticks.
b)Rotating the stepper motors as per the input.
c)Readjusting the stepper motor for any variation in input, if any.
d)After being interrupted by lower limit or upper limit of engine speed, shifting gear range accordingly and displaying the number engaged.
e)Ensuring that no upshift is there beyond seventh gear, auto-downshift below neutral and downshift below reverse.
Thus, the microprocessor system selects an optimum speed range for a particular radius of turn automatically.
Other miscellineous research activities are inclined to the areas of tank suspension and navigation systems and also in fields, related to the improvedworking of the night vision devices.
4.2) RESEARCH ON ELECTROMAGNETIC SUSPENSION SYSTEM:
So far emphasis has been laid on passive suspension design for military vehicles. This was the only system in production uptil now. Now, attempts have been made to nvestigate the possibilities of incorporating a suspension, whose characteristics, instead of remaining fixed under all circumstances,can be altered under all prevailing conditions. This optimizes the ride. Such suspensionsystems are known as 'active systems'. A number of research vehicles have undergone demonstration. One such important approach may be accomplished by the use of electromagnetic suspension systems. These systems owned the combination of speed, strength and lectromagnetic efficiency. But, the installation of these systems require significant advances in four key disciplines: linear electromagnetic motors, power amplifiers, control algorithms and computation speed. A linear electromagnetic motor can be installed at each roadwheel of the track. The motor consists of magnets and coils of wire. When electrical power is applied to the coils, the motor can retract and extend, causing relative motion between the tank body and wheel. This reduces the jerk of the crews. A power amplifier can be used to supply electricity to the motor in response to signals from the control algorithms. These control algorithms can operate by observing sensor measurements, taken from around the tank vetronics. Then these algorithms send commands to the power amplifiers installed in each corner of the vehicle. Whenever the suspension encounters any obstruction, power is used to extend the motor and isolate the vehicle occupants from the disturbance. On the far side of the obstruction the motor operates as a generator and returns back the power to the amplifier. Thus this suspension requires less than half the power of an air-conditioning system installed in the tank. Thus, this system facilitates driving of the tank on all terrains smoothly, maintaining both control and crew comfort.

4.3) RESEARCH ON DIRECT PROPULSION LASER GUNS:
One of the most lethal weapon systems on the modern battlefield, is the laser. Researchers have pondered over the Future Combat System(FCS) to be equipped with a high-power, extremely accurate,fully-stabilized laser gun. Even low-power lasers with only a few milliwatts of output power can be hazardous to a person's eyesight. At wavelengths which the cornea and the lens can focus well, the coherence and low divergence of Laser Light means that it can be focused by the eye into an extremely small spot on the retina, resulting in localised burning and permanent damage in seconds or even faster. As the FCS is visualised as an ‘all-electric’ vehicle, it was also forecasted that the operation of a laser gun can be facilitated against a variety of close-in threats- helicopters,drones, ground ‘soft’ targets and infantry.The FCS laser gun application will probably represent a tremendous step towards independence from logistic support. There is no need for frequent ammunition resupply since it will be ‘firing’ variable,high-energy short pulses (bursts) ofconverted electrical energy. During target acquisition, a low-energy laser beam will be pointed at the target toverify ‘on-target’ position and the corresponding effective range. Subsequently, the low-energy beam will be substituted with a short, high- energypulse, ultimately yielding target destruction.
A case in point is the USAF’s High-Energy Chemical-Oxygen Airborne Laser(ABL), currently being developed to destroy ballistic missiles early in their boost phase of flight, immediately following their launch phase. A full power prototype baseline configuration laser module in the hundreds of kilowatts class has already been demonstrated to meet stringent performance requirements. Another notable program is the U.S.-Israeli Tactical High-EnergyLaser (THEL), developed to engage and destroy incoming missiles. Though chemical laser technology is considered mature, a compact and transportable tactical laser weapon system, well integrated into a smaller mobile armored vehicle, remains to be demonstrated. Typical outstanding issues are integrationof optics, energy pressurization system, radar, and command & control. To facilitate its development, the U.S.Army is already leveraging technology from the USAF’s space-based laser program. These developments and similar projects imply that future ‘spin-off’ versions, on a much smaller scale, could be implemented in various, armored ground-to-ground and ground to-air offensive weapons and active self-defense applications. The high power, direct line-of-sight (LOS) laser beam must have the ability to travel through the atmosphere at tactical operational ranges (10-15 km) without detrimental losses from beam spreading, divergence, dispersion, diffraction and scattering. Additionally, it must maintain its ‘self-focus’ characteristics and high-energy density, which are mandatory for achieving an effective target kill.
4.4) RESEARCH ON UPGRADATION OF NIGHT VISION DEVICES:
The modern infrared cameras, which are employed for night-vision during counterattacks at night, have to capture the heat signatures of the enemy objects, to transform the heat wave into a visible and identifiable image of the object. Thus, proper image resolution is the prime criterion for the functioning of these devices. Uncooled thermal cameras use sensors that operate at room temperature. Modern uncooled detectors use sensors that work by changing electrical properties of the material when heated by infrared radiation. These changes (in resistance, voltage, or current) are then measured and compared to the values at the operating temperature of the sensor. Uncooled infrared sensors can be stabilized to an operating temperature to reduce image noise, but they are not cooled to low temperatures and do not require bulky, expensive cryogenic coolers. This makes small, relatively inexpensive infrared cameras possible. However, they tend to have low resolution and poor image quality relative to cooled detectors.
Therefore, now-a-days cooled detectors are normally preferred for better resolution. They are still in a stage of research, inclined to enriching the field of Cryogenics. Cooled detectors are typically contained in a vacuum-sealed case and cryogenically cooled. This greatly increases their sensitivity since their own temperatures are much lower than that of the objects from which they are meant to detect radiation. Without cooling, these sensors (which detect and convert light in much the same way as common digital cameras, but are made of different materials) would be "blinded" or flooded by their own radiation. However, they have some disadvantages. The drawbacks of cooled infrared cameras are that the vacuum container is often expensive and difficult to produce, and the cooler requires a lot of power to function, and time to bring the sensor down to the operating temperature, as the camera may need several minutes to cool down before it can begin taking pictures. These devices make cooled infrared cameras generally bulky and expensive, but they also provide superior image quality compared to uncooled cameras. Materials used for infrared detection include a wide range of narrow gap semiconductors.
Another field where tank technology wants to upgrade itself is in the field of ‘Prognostics’. The Expeditionary Fighting Vehicles (EFV) Prognostics program was sponsored by the Office of Naval Research with the purpose of transitioning technology to the Fleet. This program was aimed to meet defined performance requirements for detection, diagnosis and prognosis.
Prognostics is defined as the ability to reliably predict the remaining useful life of mechanical or structural components, within an actionable time period, within acceptable confidence limits. The EFV program is developing an on-vehicle prognostics system that detects and isolates impending critical and/or catastrophic failures of the: 1.Engine, 2.Automotive Drive Train(Transmission and final drives) and 3.Vehicle Batteries.
The overall objective of prognostics is to provide information to support better management of operational and maintenance resources, integrated with vehicle diagnostics and testability. The EFV prognostics system will collect, store and process prognostic system sensor and vehicle information using on-vehicle processing and data bus resources. The vehicle’s Fault Manager will integrate prognostics system information with vehicle diagnostics information. The resulting prognostics fault codes will be displayed at crew stations if action by the operator is required. In addition, the prognostics information will be downloadable to the vehicle’s Portable Maintenance Device for access by other information customers. These information customers include: 1. Vehicle maintainers and 2. Operational Commanders.

5. CONTINUED:
Advanced Robotics Concepts:
Now-a-days, concepts have already risen about converting the present battle tanks to a remotely operated one or in other words, Robotic Battle Tanks.
DARPA has a heavy emphasis in advanced robotics concepts, to be applied to military vehicles. It focusses on those applications or technologies that are particularly stressing. One effort involves the development of very small robots that can work cooperatively on the tank itself. The challenge in this effort is to pack useful capability into a very small package, and to develop the software to allow these robots to work together. Another important effort will bring useful robotics technology to the work of dismounted operations in an effort to save soldiers’ lives.
Thus DARPA has initiated the Distributed Robotics program to develop microrobots that can work together in groups in dynamically changing environments. These small robots are proposed to be five centimeters (two inches) or smaller in any single dimension. They will work cooperatively together in groups, be capable of different modes of locomotion (land, water, vertical climbing, etc.) and will adapt their behavior based on remote user inputs or onboard sensors. The program has 13 contractor teams investigating different approaches, such as robots that can dynamically change their shape and locomotion mode. All contractors are now trying to demonstrate a single robot
Accomplishing a specific task, but in future,contractors will start work on multiple robots,working together.
DARPA has also initiated the Tactical Mobile Robotics program which aims at developing robotic technologies and platforms
designed to revolutionize dismounted operations by projecting operational influence and situational awareness into previously denied areas. These portable robots will be robust and able
to adapt to complex environments while employing specially designed payloads and devices. The program has selected three platform development concepts, demonstrated key component technologies for robust urban mobility (climbing up stairs, over rubble, etc.). Basic mobility platforms are likely to be outfitted with revolutionary perception aids such as Omni-cameras and laser scanners in conjunction with development of semi-autonomous navigation capabilities for non-GPS conditions (indoors, underground, deep jungle, etc.). The program is thus aimed at integrating enabling technologies and specialized payloads into functional platforms.

Advanced Energy Technologies:
DARPA is investing in a variety of technologies to provide high energy-density power sources for military systems. The program is investigating alternatives to traditional batteries for portable power applications through the use of fuel cells and solar cells, as well as methods to harvest energy from the environment for use in the vehicles. The program has already demonstrated robust, multi-kilowatt logistics fuel processing with fuel cell stack integration and transitioned the technology to the Navy’s Ship Service Power Program.The program will focus on generating electrical power in the 300- to 500-watt range directly from logistics fuels using compact, low-signature technologies such as thermophotovoltaics and solid oxide fuel cells, installed in military vehicles. The program is also investigating electostrictive polymers and piezoelectric materials for power generation from mechanical motion of the crew in the tanks. These materials can be easily loaded in the tank armour. Thus the program is trying to integrate these energy-harvesting technologies by testing them with sensors and small devices.

ADVANCED CRYOGENIC SYSTEM TECHNOLOGY:
Because of the electromagnetic interference in the present day electronic warfare, the radars installed on the ground military vehicles are not able to detect the weaker signals from the enemy forces. Thus DARPA has encouraged the Cryo-Systems program for developing high-temperature superconducting components packaged with cryogenic devices for use in radar, electronic warfare suites and communications systems, so that increasingly weaker signals are detected within a background of interference and clutter.
Initially, most of the vetronics systems rely on software algorithms. High-temperature superconducting filters and amplifiers are very selective, and can screen out unwanted signals to receive only the desired frequencies. But this type of multiband performance is particularly useful for signals intelligence collection systems and for improved GPS jamming rejection.
Cryogenic systems have been employed at ground-collection sites and installed in Navy and Air Force reconnaissance aircraft as well as ships. Now further demand is made for their use in tank technology. All are showing greatly improved reception of low-power signals within a noisy background. The range enhancement is typically two to three times greater than previously possible. A signals intelligence collection system for multiple cellular bands, using cryogenic components, is likely to be demonstrated. Thus the program is likely to focus on developing tunable superconducting filters, while maintaining their superior selectivity, enabling reductions in size and weight while increasing the coverage in detection of low-level signals.

ADVANCED MATERIALS TECHNOLOGY:
Research in advanced materials for military vehicle application technologies is the last of DARPA’s historical core investment area. Past achievements have tended to be in the area of structural materials such as advanced composites and ceramics. Both were instrumental in achieving the desired performance on armoured vehicles. Work continues in structural materials, focusing on ultra lightweight, high-strength materials for specific military applications, including body armor. In addition, they are investigating new materials that are termed “functional” in that they contribute to tank system operations or capabilities beyond simply forming the system structure. In this area, they are looking at magnetic materials, smart materials (which sense and respond to their surroundings), electroactive polymers, and frequency-agile materials. Thus researchers continue to support the development of high-temperature superconducting components, as well as a variety of advanced energy technologies and an effort to develop a new high energy explosive material.
DARPA has started the Ultra Lightweight Materials program to pursue metals that have the light weight of a composite material but without the traditional worries of corrosion and delamination. The metal is fabricated with a variety of internal microstructures, giving it strength with minimum weight. This will lead to substantial weight and cost savings in a number of military applications. In addition, the internal microstructures allow the metal normally used as part of a structure to also perform a useful function such as blast mitigation or thermal control. These new materials are to be demonstrated for antenna masts on tanks. The program is investigating other military applications such as the development of bullet-resistant fuel tanks in military vehicles.
DARPA has also activated the Smart Materials and Actuators program to develop new classes of materials and structures that use integrated sensors and actuators to respond and adapt to mission needs and the environment. This technology is being developed to suppress vibration and actively tune structures to reduce noise in armoured systems.
As part of the Functional Materials effort, the Electroactive Polymers project is another challenge undertaken by DARPA. Researchers are trying to develop polymers that can conduct and respond to an electrical current. The polymers can take the form of a thin film or a fiber and move or change shape when an electric current is applied. Such materials provide great help in the Robotics concept of the tank. These materials can be used as artificial muscles for small robots. These robots will have artificial “retinas” to process images quickly and efficiently.
DARPA’s efforts in the Frequency Agile Materials for Electronics program are investigating new materials that can be modified by the application of either an electric or a magnetic field. In these new materials, the application of this field changes the property of the material in some way. The materials can be used as communications systems filters and antennas – the magnetic or electric field “tunes” the filter or the antenna to be more responsive to a particular frequency. Antennas constructed from these frequency agile materials can be smaller and lighter weight, and can be a variety of shapes. These antennaes can be installed on military vehicles, easily conforming to the shape of the tanks. The materials fabricated and tested to-date in the program have shown promising performance.
One of the very interesting programs of DARPA has inaugurated the Spintronics program or the Non-Volatile Memory program for the military vehicles. The program has demonstrated a radiation-hard, 16-kilobit memory that is only one square centimeter in size –this chip is desired to be used on military systems to upgrade memory capabilities. The program has also proposed to develop a memory chip slightly larger than one square centimeter holding more than one megabit of information. This program is surely capable of upgrading the capability of the Vetronics system on tanks.
DARPA is also advocating the High Energy Density Materials program to investigate the synthesis of new molecules that will have 200 percent to 500 percent more explosive and/or propulsive energy per unit weight than does dynamite, and have between two and six times as much propulsive or explosive energy as current state-of-the-art operational materials. In addition, they are looking at molecules made solely or mostly of nitrogen, whose production and use should be environmentally friendly. If the program succeeds, the capabilities of the new materials could provide increased range and maneuverability and/or increased kill-effectiveness for the tank armament systems against missiles( greatest of all tank threats) through improvements in both the propellant's thrust and the warhead's lethality (per weight and volume). One research team recently proved the existence of a new nitrogen ion, a key step in synthesizing the new high energy-density form of nitrogen sought by the program.
Thus, the new reasonable technologies pursued by DARPA towards the supportive development of military vehicles are worth appreciable. As DARPA takes its role as the technical enabler for innovation for national security very seriously, it will surely be the key to the success of the tank warriors of the 21st century.
7. PROPOSED MODERN LAND OPERATIONS:
The future of land operations is likely to be multidimensional, complex and largely unstructured. That's why the MoD is instigating development of the Future Rapid Effects System (FRES), to meet the need for greater mobility, survivability and systems integration for armoured fighting vehicles.Among the wide-ranging programmes that are being used to support FRES are:
1. vehicle architectures
2. the development of standards and guidelines
3. improved survivability and Command, Control, Communications, Computers and Intelligence (C4I).
Improved survivability: Survivability is perhaps the key issue. So the programmes include defensive aid systems and electro-optical counter measures - including an anti-dazzle CMOS camera. Involvement with C4I includes:
1.Vehicle system integration and electronics
2.Crew system technologies.
In every area, long-established experience in human factors integration is applied to support the technologies and ensure that troops are better able to fight and survive. Improvements are being made for C4I both within and between platform structures, to raise crew awareness and knowledge, and increase their survivability.
Sensors bring the digitised battlefield and network centric warfare closer. With advanced data processing techniques, sensors improve situational awareness and survivability, and increase the probability of real-time links between sensor and shooter. And they will - as they develop further - make it easier and more efficient to mount precision attacks on high value targets, at greater depths of engagement.Artificial intelligence technologies and unmanned systems are also being developed to improve troop protection, making it possible to remove soldiers from danger in close combat zones.
6.1) CASE STUDY OF RECENT ARMOURED DEVELOPMENT:
Qinetiq has built their innovative Advanced Composite Armoured Vehicle Platform demonstrator (ACAVP)(Figure shown below) from revolutionary materials. They developed fibre composites, and affordable titanium alloys in a business venture with British Titanium. Together they gave Qinetiq strong, lightweight structures suitable for lightweight ordnance, vehicles and armour.
Fig.23 Showing the Plastic Tank.Nicknamed the 'plastic tank', ACAVP has been thoroughly tested, driven over 1,800 km and found to have significant stealth advantages over traditionally-structured vehicles, including its radar thermal and electromagnetic signatures. The ballistic tests carried out on composite materials have also been an outstanding success. Building on this success they are now developing new composite-material armoured fighting vehicle demonstrators, including main battle tanks.
6.1.1) PLASTIC TANK:
AFV construction hasn't changed much since the 1960s, when aluminium was introduced as an alternative to steel, so why was there the need for such a radical departure now? It's all a question of weight and of how the British Army is increasingly becoming involved in policing the world. The answer was to develop a vehicle with at least the same protective capabilities as those currently in use, but light enough to be airlifted easily at short notice. This meant abandoning metals for a lightweight, but extremely tough, moulded E-glass fibre composite: plastic.
The 'plastic tank' is a world first in military engineering. It's a groundbreaking new project, in conjunction with the UK Ministry of Defence and Vickers Defence Systems. The Advanced Composite Armoured Vehicle Platform (ACAVP) is the first composite moncoque plastic AFV to have been made in the world. The vehicle can withstand attack from a whole range of threats - including high performance cannon fire - while increasing the survivability of the crew against small arms fire, shaped charge anti-tank rounds and shrapnel from artillery shells, compared with conventional vehicles. In addition, the vehicle incorporates stealth technology to reduce its visibility to radar and infrared sensors. The new plastic armoured fighting vehicle (AFV) has sailed through its battle tests and proved to have major advantages over conventional metallic armoured vehicles of a similar size. Vickers believe it could prove a tremendous asset; it's faster, lighter and therefore easier to transport by air than conventional vehicles, so it can be flown rapidly to war zones.
Fig.24 Showing the ACAVP on trials at QinetiQ's test track.
For many years, composites have been used to make protective liners in armoured vehicles to prevent spallation - the potentially deadly shower of metal shards that can shear off inside the hull when the vehicle is hit. By removing the metal hull and replacing it with a plastic construction, there is no need for the weight-increasing spall liner and the danger to the crew from a hit is reduced by the design. It has passed all the tests required of a fully operational military vehicle and the technology can now be taken up by industry to be used in production vehicles. The plastic tank at a glance:
§ Weight: just 24 tons, four tons lighter than the similar metallic vehicle.
§ Top speed of 40mph over rugged terrain.
§ Decreased fuel consumption, reducing the need for supporting fuel tankers
§ Increased survivability for the crew, through: reduced visibility to radar and infra-red scanners; reduced risk of shrapnel inside the hull; better protection against bullets, mortars and land-mines.
§ Ideal for use in salt-water conditions, as plastic is less susceptible to corrosion than metal.
7. CONCEPT OF THE FUTURE COMBAT SYSTEM (FCS) :
The mentioned brainstorming research activities in the various fields, such as in the areas of weapons, armour,power plants, etc, will give rise to a new conception of the Future Combat System( may be in the 20 ton class ), representing a dramatic departure from the previous concept of the main battle tanks. According to the US Amy Tank-Automotive and Armaments Command’s picture of the FCS, it would be based on evolutionary tank design and technology. According to some of the military researchers, the next generation armoured fighting vehicle may not be referred to as a modified MBT of today.Thus, the systems engineering procedures will change the entire picture of the Future Combat Systems, so that it may not appear as the present tanks. This is evident from the computerised model of the desired model as shown below-
Fig.25 Showing a computerized model of the proposed Future Combat System.
Scenario of the FCS assumes that it can be the major contributor to the modern digitized battlefield environment. Operational requirements dictate that the FCS should operate as a ‘combat system’, while functioning and communicating beyond the conventional rather narrow tactical level. The FCS will be an active node on the battlefield digitized network. This is, in essence, a dramatic departure from the conventional way, tanks have been operated and deployed, since their inception. There will be Reconaissance Modules, which will be fired to assist the commander and crews in obtaining real time digitized information on the close area battlefield. This information will be used by the local forces, but also will be conveyed to the Greater Area War Management Centre. Information on enemy targets, obtained from these modules, will be fed back to the FCSs, which are prioritized, and used to automatically direct, aim and fire the Electromagnetic Guns and high power Laser Guns and anti armour/air missiles at their potential targets. Thus the FCS will serve as the integral part of the modern battlefield and will serve as its eyes and ears. The FCS is also conceived of being equipped with a second generation Vetronics system, that will further advance digitized data control and distribution, electrical power generation and management, computer resources, crew control and display processes. The Vetronics system will be capable of accepting a variety of inputs and delivering outputs, related to power system control, communications, countermeasures, weapons control, sensor control, artificial intelligence, training, maintenance, diagnostics and prognostics. This architecture will provide the interface between the various functional modules, computers and power sources, thus ultimately leading to the concept of an Unmanned Fighting Vehicle or more precisely, a Robotic Vehicle. The layout of the conceived FCS is shown below.
Fig.26 Showing the scenario of the FCS.
8. CONCLUSION:
Prediction of the future is within the realms of astrology, and preparation for it is wisdom. To visualize the design requirements of the future MBT,by the turn of the century, requires a knowledge of the present state of the art in tank designing, and the correct visualization of the future battlefield. Also required would be a rough idea of the economic layout and ability to gauge the technological and management expertise, without exaggeration, so as to produce a high technology-intensive offensive weapons system in the next two decades or less.The position of the tank as the most powerful weapons system of the ground forces, will probably remain unchanged. No other system, in sight is able to fulfill its function, better than a tank. However the shape of the tank will change. Countries which have the need and resources to develop and produce their own tanks are all, as ever, faced with the same general problems. On the other hand, they all have to keep pace with new technologies to defeat tanks, by improving their protection and make progress in their mobility. In this process, the weight is likely to go up, because of the need to increase the protection of tanks of a given size and also because of the size of the armament they will need, to defeat improved armours. True engines and transmissions will get smaller and lighter for a given propulsive power, but apparently not small enough to compensate for expected increases in the weight of the protection and armament. Therefore, in order to achieve satisfactory tank weights from the mobility point of view, new tank concepts will have to be adopted.
It is sometimes better to think unconventionally, in order to break the shackles of conventional thinking. The drills and fighting techniques, ie, the tactics for tank fighting have been established over the years and cannot be changed immediately because of the inherent time lag to educate the troops and train them for a new methodology. The equipment or weapon designers should always stay a step ahead of the existing techniques, by resorting to revolutionary designs, which defeat the tactics. At all stages of the design effort, two factors are always to be kept in mind. Firstly, the proposals should be forward thinking but realistic and secondly, as far as possible, the recommendations should be capable of being implemented indigenously, within the stipulated time frame. The following quote puts across the basic thought, underlying this attitude:
“A good researcher and engineer must be the masters of two ends of the spectrum: Ideas at the highest level of abstraction and analysis and implementation at the most mundane levels of details.”