This page contains answers to common questions about hybrid rocket motors and links to more detailed information.
- What is a hybrid motor?
- Why use nitrous oxide?
- What regulations control hybrid use?
- How old do I have to be?
- Can I get my Level 1 cert with a hybrid?
- Are they safe?
What is a hybrid motor?
A hybrid rocket motor uses fuel and oxidizer that are in different phases. The most common hybrid uses a solid fuel and a liquid oxidizer. There have been successful firings of motors with solid fuel and gaseous oxidizer, and "reverse" hybrids using a liquid fuel flowing over an oxidizer-rich solid.
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Why use nitrous oxide?
Nitrous Oxide (N2O or "NOX") is not toxic or hazardous. In its pure form it's an intoxicant, but the NOX that we commonly use has a little "leak check" compound added to it (the same as natural gas). This smelly stuff (usually sulfur dioxide or butyl mercaptan) keeps people from abusing the NOX and also helps you detect a slow leak.
NOX is a cryogenic, so if you're careless you could get frostbite from handling it. Liquid NOX has a vapor pressure that is less than liquid CO2, which is in common use. With elementary safety precautions, it's about as benign as you could expect a rocket propellant to be. And thanks to hot rodders, who have been using it as a performance additive for years, it's readily available.
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What regulations control the use of hybrids?
NOX is a compressed gas, and is subject to any regulations that might apply to the handling of compressed gases. The commercial hybrid motors use fuel grains that are non-hazardous, usually some form of plastic. Some hybrids use a small amount of conventional solid rocket propellant as an igniter or preheater. As long as this igniter grain is under 62.5 grams, it is only subject to the same regulations as a composite model rocket motor.
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How old do I have to be?
Both the national rocketry organizations (NAR and Tripoli) require that you achieve Level 1 certification to use a hybrid motor. This requires you to be at least 16 years of age.
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Can I get my Level 1 Cert with a hybrid?
Yes! At this writing, the RATT Works H70 motor can be used to make your Level 1 certification flight. This has been accepted by both NAR and Tripoli.
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Are they safe?
Yes. While hybrids are more complex than most conventional solid fuel motors, their operation is well understood. Always follow the NAR and Tripoli safety codes when using any kind of sport rocket motor.
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