In this example, the letter (C) represents the total impulse range of the motor, the number (6) before the dash represents the average thrust in newtons, and the number (3) after the dash represents the delay in seconds from propelling charge burnout to the firing of the ejection charge (a gas generator composition, usually black powder, designed to deploy the recovery system).
A C6-3 motor would have between 5.01 and 10 N·s of impulse, produce 6 N average thrust, and fire an ejection charge 3 seconds after burnout.
In many countries, the sale, possession, and use of model rocket motors is subject to governmental rules and regulations.
High-power rockets in the United States are only federally regulated in their flight guidelines by the FAA.
However, some of the consumer motor manufacturers and two U.S. national rocketry organizations have established a self-regulating industry and codified it in National Fire Protection Association (NFPA) "model" code documents, which are adopted only in specific circumstances and jurisdictions, largely in conjunction with fire and building codes.
Both these organizations have three levels of certification which involves building progressively more complex and higher powered rockets and taking a test of safety rules and regulations.
On February 11, 2000, Tripoli Rocketry Association and the National Association of Rocketry filed suit in the United States District Court for the District of Columbia claiming that the BATF applied "onerous and prohibitive civil regulations" against sport rocketry hobbyists due to the Bureau's improper designation of ammonium perchlorate composite propellant (APCP) as an explosive.
The commentary by BATFE staff in response to objections to adding new enforcement against hobby rocket motors is quite instructive.
[16] In 2009, the court ruled in favor of the hobby organizations and ordered the BATF to remove APCP and other slow burning materials from its list of regulated explosives.
[18] The largest vendor of model rocket motors in the world is Estes Industries.
The largest vendor of professional solid rockets in the world is Orbital ATK.