AMATEUR ROCKET MOTORS
Amateur propulsion systems / rocket motors are where the action is really at for many of the non-professional altitude attempts. You need to develop skills in mathematics, physics, chemistry and in the case of hybrid and liquid propulsion systems, high pressure plumbing. If the propulsion systems are to be controlled, or you want to instrument them to obtain data (generally a good idea), a knowledge of electronics is a good idea too.
As the altitude requirements go up, so do the costs of buying large rocket motors off the shelf. It gets to a point, where the price of a rocket motor off the shelf is out of the range of those in the non-professional rocketry community. At that point, the advantages of building your own amateur propulsion system are compelling.
By far the safest rocket motors to construct are hybrid rocket motors. Liquid propellant engines are more complex, requiring more plumbing, and liquid propellant engines are also more temperamental.
In the U.K. it is illegal to manufacture solid rocket motors of ANY size, anywhere in the U.K., under the 1875 Explosives Act. Manufacture is defined as mixing the solid compounds neccesary to make the solid propellant for a solid rocket motor.
Because of emails I have received on this subject, please try and understand, "ANY" means "ANY", regardless of if you are talking about grams or kilograms of solid compounds. It is no good asking me about how to do this in the UK, because it is illegal. It also does NOT matter where in the U.K. you are, on private or other property. Without the appropriate manufacturing licence (normally only available to arms companies and firework manufacturers), you cannot make solid rocket motors legally.
However the saving grace is that hybrid rocket motors are not subject to the same laws, since they do not contain pre-mixed fuel and oxidiser, nor do they require fuel and oxidiser to be mixed until they are launched, nor are the fuel and oxidiser dangerous. So, the obvious way forward in the U.K. for amateur rocket builders, is the hybrid rocket motor.
|Commercial Motor||Amateur Motor|
|Development Costs||None - it is already developed||Can be considerable|
|Development Time||None - it is already developed||Can take years in order to test thoroughly|
|Advantages||You don't need many clues to follow this approach||You need lots of clues to follow this approach, and that means you have to be knowledgeable about your subject|
|Disadvantages||Not having many clues is dangerous||Needing lots of clues takes time|
How to start.
The place to start is by reading up on rocket propulsion systems. The bible of rocket propulsion engineers is generally regarded as being a book called Rocket Propulsion Elements by Sutton and Biblarz. Now in its 7th edition, it contains a good overview of rocket propulsion.
Whilst Sutton and Biblarz does have a good treatment of hybrid rocket motors, I find that there is even more detail on hybrid propulsion in a book called Space Propulsion Analysis and Design by Humble, Henry and Larson. This is another excellent text book for developing rocket propulsion knowledge.
The key textbook for Liquid Rocket Engines is Design of Liquid Propellant Rocket Engines by Huzel and Huang.
When you have read through these books, try and do some of the examples in the books, learn how to theoretically design propulsion systems. If you progress to actually building propulsion systems, you will learn that it is the practical experience that actually helps far more than reading textbooks, but having the background knowledge, is a major advantage.
After reading through these books, and following through some of the examples, obtain a copy of combustion code simulation software such as PROPEP or GUIPEP. Then you will be in a good position to start designing an amateur rocket propulsion system.
The best source of information and help online is the arocket forum.
- Rocket Propulsion Elements - George Sutton and Oscar Biblarz, 7th edition - 2001 - Wiley - ISBN 0-471-32642-9
- Space Propulsion Analysis and Design - Ronald Humble, Gary Henry and Wiley Larson, 1st edition (revised)- 1995 - McGraw Hill - ISBN 0-07-031320-2
- Design of liquid propellant rocket engines - Dieter K. Huzel and David H. Huang, 3rd edition - 1992 - AIAA Inc - ISBN 1-56347-013-6 / ISSN 0079-6050
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