The FAQ!



This FAQ is not intended to be a complete course in rocketry. It covers some basics and has pointers to further information but from there, it's up to the reader. If there are any errors or if you know of something that really should be included, please email it to the author Email Ray

Some parts (it should be obvious which) are the author's opinions. Feel free to disagree. While the author tried to ensure the accuracy of the information in this FAQ, he makes no warranty, express or implied, as to the validity or usefulness of anything that follows. You pays your money and you takes your chances.


  1. Definitions
  2. Rocketry Classes
  3. Associations
  4. Frequently Asked Questions
  5. About ARocket
  6. Books
  7. Suppliers
  8. More Suppliers


The following is a short list of terms, acronyms, and abbreviations that are commonly used on ARocket:

AN Ammonium Nitrate: Solid rocket oxidizer

AP Ammonium Perchlorate: Solid rocket oxidizer

BP Black Powder

CATO Catastrophe At Take Off

DeltaV Change in velocity

ELV Expendable Launch Vehicle

GLOW Gross Lift Off Weight: total rocket weight at the moment of lift off.

GLOM Gross Lift Off Mass: technically more accurate than GLOW.

GOX Gaseous Oxygen

GrEp Graphite Epoxy

H2O2 Hydrogen Peroxide liquid oxidizer/monopropellant.

HTPB Hydroxyl-terminated polybutadiene: Solid rocket fuel/binder

Hydrazine Liquid fuel.

Hypergolic Fuel and oxidizer ignite spontaneously upon contact.

Id Destiny Specific Impulse: product of specific gravity and specific impulse.

Impulse Thrust Force * Time

Isp Specific Impulse: Thrust force per unit weight flow of propellant

LH2 Liquid Hydrogen

LOX Liquid Oxygen

Mass Ratio Final mass (after propellant burn) divided by initial mass.

MMH Monomethylhydrazine: liquid fuel related to hydrazine.

MTA Mojave Test Area: Rocket testing site maintained by the RRS

N20 Nitrous Oxide, commonly used in drag racing

NOX Oxides of Nitrogen, generally toxic products of incomplete combustion of air or N2O

Propellant Mass Fraction Propellant mass divided by initial mass.

PVC Poly Vinyl Chloride: plastic used as a fuel grain in some hybrids

RLV Reusable Launch Vehicle

RFNA Red Fuming Nitric Acid: liquid oxidizer; nitric acid with 5-20% nitrogen dioxide.

RP1 Kerosene-like fuel of higher purity for use in rocket engines.

SSTO Single Stage To Orbit

TSTO Two Stage To Orbit

UDMH Unsymmetrical Dimethylhydrazine: liquid fuel related to hydrazine.

Ullage Extra volume of gas above propellants in the tanks

See also the NASA Thesaurus


Model Rocketry:

The kind of rockets everyone fooled around with as a kid. It uses only premanufactured, solid motors from class A to G. Restrictions: GLOW not to exceed 1500g; Each motor not to exceed 62.5g propellant and/or 160 NS impulse; Total propellant not to exceed 125g; No metal structural parts.

HPR - High Power Rocketry:

Scaled up model rocketry, using the same basic methods for construction, though metal parts can be used if necessary. It uses only premanufactured solid or hybrid motors from H to O. There are no weight restrictions, but each motor may not exceed 40,960 NS impulse and the total impulse may not exceed 81,920 NS.

Amateur Rocketry:

Anything that falls between HPR and professional rocketry. This includes liquid fueled engines, metal structures, building your own motors, and just about anything else you can think of. There are no formal definitions or requirements, other than the laws of physics and your government.

Experimental Rocketry:

Different people have used this to mean different things, but essentially it's the same as amateur rocketry. The term is generally used by HPR people to refer to TRA sanctioned amateur rocketry

Professional Rocketry:

Rocketry conducted for profit, usually by governments or large corporations.


IEAS International Experimental Aerspace Society: Tax-deductable non-profit educational organization supporting independent experimental rocketry development.

ARSA Amateur Rocketry Society of America: Leads legislative efforts to ease regulatory burden for amateur rocketeers and supports all types of hobby rocketry.

NAR National Association of Rocketry: The organization that regulates model rocketry in the United States.

TRA Tripoli Rocket Association: High power rocketry organization in the United States.

CAR Canadian Association of Rocketry: The organization governing model and high power rocketry in Canada.

RRS Reaction Research Society: The oldest amateur rocketry group; based in Southern California.

PRS Pacific Rocket Society: One of the leading amateur rocketry organizations, based in Southern California.

ERPS Experimental Rocket Propulsion Society:

SFF Space Frontier Foundation: A general space advocacy society.

X-Prize Organization: They are raising a prize of $10 million US for the first group to fly a three man RLV to 100km twice in two weeks.


1) Which is best for amateur rocketry: solid, liquid, or hybrid propulsion?

The question gets a lot of debate. As with anything else, it depends on a number of factors, and there's no definite answer. Factors that should be considered include: your personal background and knowledge; size of rocket; impulse required; specific impulse desired; thrust; monies available; reliability factor; materials and equipment available; legal aspects; etc.

Generally, very small rockets (up to several kg or tens of kg) are easiest to build as solids or hybrids, and a lot of the technology is already available. Liquids provide the highest specific impulse and are most economical in larger sizes but are more complex. Hybrids tend to bridge the gap between liquids and solids, providing better impulse in mid-size than solids and being simpler than liquids.

2) "How do I build rocket motors?"

There is no easy answer to this. You need to buy the books, join an amateur group, do the research, and understand what you're doing. Blindly following a recipe you found is asking for the sudden removal of your extremities.

3) "Where can I get LOX?"

Check with welding supply companies in your area or with the local outlets of Air Liquide and Praxair, listed in the SUPPLIERS section. If all else fails, medical supply companies sell it for respirators, though you'll pay through the nose (pun intended) and they may have restrictions. Price varies widely, so shop around.

4) "Where can I get transducers, DAQ boards, valves, fiberglass, etc?"

Omega offers a very wide selection of data collection material, their prices can be a little steep for the amateur. DataQ offers a very reasonably priced serial port data collection module that is ideal for the beginner.

5) "Putting a rocket into orbit looks easy. How come no amateur has done it yet?"

Short answer: Because it ain't easy, not even close.

Long answer: There are several inter-related reasons: Scalability, Materials, Methods, Development, Cost, Time and Paperwork.

SCALABILITY: Some rocket components are impractical on a small scale, for instance turbopumps and hydraulic systems. Rockets also suffer from the effects of the cube/square law as they get smaller, particularly tanks.

MATERIALS: There is a sliding scale of price and performance: steel,aluminum, alloys, fiberglass, graphite, and someday, buckytube. Generally, the higher the strength to weight ratio, the higher the price. Graphite fibre is expensive. And if you go cheap, performance suffers.

METHODS: Advanced manufacturing techniques are a stretch for the average amateur. Not many of us can afford a filament winding machine. You could build one of course, but that's a project by itself. And the best way to implement regenerative cooling is to machine the coolant passages in the walls of the engine, fill them with wax, electro-deposit a "roof" and then melt the wax out. Possible, but a major undertaking. If you contract for those kinds of jobs, you drive the price way up, and if you use simpler methods, performance suffers.

DEVELOPMENT: You can't buy a kit, slap the pieces together, and put a satellite in orbit (not yet anyway.) This is real R&D: you're going to have to build a prototype, test it, build another, test it, build another and soon. For each of three stages. And things go wrong: valves stick, plumbing leaks, rockets blow up. And then there's the support equipment; you're going to have to build a test stand, data acquisition system, fuel loader, launch pad, tracking system and more. All of this takes time and, yes, money

COST: The big one. All the other factors contribute to the cost, and it adds up in a hurry. How much would it cost to do a "Sputnik?" More than $25,000. Some groups have spent that much already, and are still nowhere near orbit. $100,000 is probably in the ballpark. (Note: that's the cost of the entire program, not just the flight.)

TIME: The key word here is "amateur." These people are not paid to build rockets. They have regular jobs and only do it in their spare time. This doubles or triples development time.

PAPERWORK: Obtaining the necessary permits to place an object in orbit is particularly difficult, considering the value of orbital assets. Insurance to protect your ground overflight and these orbital assets is very expensive also.

Short answer #2: If that still doesn't convince you, try it yourself.

6) "What materials should I use for my rocket motor?"

In Appendix C of Huzel & Huang there is a brief description of the materials being used in modern rocket engines.

7) "Why don't we start a newsgroup for amateur rockets instead of a mailing list?"

Mailing lists have a very strong self-selection factor; you have to want to join up. Moving to a newsgroup would bring a higher profile, but it would also bring spammers, flamers and the truly clueless. The average IQ in USENET has been plunging in recent years, with no sign of bottom. Most of us do not want to be pestered by endless repetitions of Question #2.


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The ARocket list is dedicated to the advancement of amateur rocketry. Amateur rocketry is: encompassing many of the goals and methods employed by professional rocketry work at NASA and other representative organizations at a fraction of the cost. Amateur rocketeers are typically small groups or dedicated individuals working within small budgets. This list endeavors to present a forum for discussion and communication to advance the community, and to create networking opportunities.


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E) Revision 4.0.3, Feb 5, 2005.

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