Motor Certification

The purpose for certifying hobby rocket motors is to enforce standards on motor manufacturers and to help ensure the safety of the hobby. There are currently three organizations that certify hobby rocket motors:

		The National Association of Rocketry (NAR) is the oldest organization and promotes model rocketry in the United States. It has traditionally been focused on model rocketry (A-F class motors), but has started certifying high-power motors in recent years. www.nar.org N.A.R. Standards & Testing
		The Tripoli Rocketry Association (TRA) was formed to promote high-power rocketry. It is international, with prefectures all over the world. Tripoli is the primary organization for certifying high-power motors manufactured in the United States. www.tripoli.org Tripoli Motor Testing
		The Canadian Association of Rocketry (CAR) was formed to promote rocketry in Canada. and is the primay organization for certifying motors manufactured in Canada, notably by Cesaroni Technology Incorporated. www.canadianrocketry.org C.A.R. Motor Certification Committee

All three organizations accept motors certified by the others so launches held under the auspices of any of these organizations allow motors certified by the other organizations to be flown.

NFPA 1125 Code for the Manufacture of Model Rocket and High Power Rocket Motors is the base document for the testing requirements for all hobby rocket motors.

The contents of the document is carefully protected against casual reading. (You must purchase it and then even reading it requires access rights on the document.) The license does not allow reproduction here, but there are some interesting tidbits from Chapter 8 (Testing and Certification) that are worth paraphrasing. (This is taken from the 2001 version; the 2006 version is currently in review.)

• A minimum of 10 samples are to be tested for model rocket motors, 2 for high-power motors.
• Testing must be done at, or corrected to, sea level and a temperature of 20°C (68°F).
• The total impulse must not have a standard deviation greater than 6.7%.
• The ejection delay must not vary more than 1.5 second or 20% (whichever is greater, up to 3s) from average.
• The average thrust must not vary more than 20% (or 1N for model rocket motors, 10N for high-power motors, whichever is greater) from average.
• The motor must be incapable of ignition when subjected to temperatures of 125°C (257°F) for 30 minutes.
• No part of the case must exceed 200°C (392°F) during or after firing.

As you can see, there is much lattitude for variation between individual motors.