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Motors for
model rocket A model rocket are small rockets designed to reach low altitudes (e.g., for model) and be recovered by a variety of means. According to the United States National Association of Rocketry (NAR) Safety Code, model rockets are constructed of p ...
s and high-powered rockets (together, consumer rockets) are classified by total
impulse Impulse or Impulsive may refer to: Science * Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time * Impulse noise (disambiguation) * Specific impulse, the change in momentum per uni ...
into a set of letter-designated ranges, from ⅛A up to O. The total impulse is the integral of the thrust over burn time. : P_ = \int\limits_^F_(t^)dt^ = F_t. Where t is the burn time in seconds, F_ is the instantaneous thrust in newtons, F_ is average thrust in newtons, and P_ is the total impulse in newton seconds. Class A is from 1.26
newton-second The newton-second (also newton second; symbol: N⋅s or N s) is the unit of impulse in the International System of Units (SI). It is dimensionally equivalent to the momentum unit kilogram-metre per second (kg⋅m/s). One newton-seco ...
s (conversion factor 4.448 N per lb. force) to 2.5 N·s, and each class is then double the total impulse of the preceding class, with Class B being 2.51 to 5.00 N·s. The letter (M) would represent the total impulse of between 5,120.01 and 10,240.00 N·s of impulse. Motors E and below are considered low power rocket motors. Motors between F and G are considered mid-power, while motors H and above being high-powered rocket motors. Motors which would be classified beyond O are in the realm of
amateur rocketry Amateur rocketry, sometimes known as experimental rocketry or amateur experimental rocketry, is a hobby in which participants experiment with fuels and make their own rocket motors, launching a wide variety of types and sizes of rockets. Amateur ro ...
(in this context, the term ''amateur'' refers to the rocketeer's independence from an established commercial or government organization). Professional organizations use the nomenclature of average thrust and burning time.


Rocket motor codes

The designation for a specific motor looks like C6-3. In this example, the letter (C) represents the total
impulse Impulse or Impulsive may refer to: Science * Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time * Impulse noise (disambiguation) * Specific impulse, the change in momentum per uni ...
range of the motor, the number (6) before the dash represents the average
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
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 A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...
composition, usually
black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
, 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. An attempt was made by motor manufacturers in 1982 to further clarify the motor code by writing the total impulse in newton-seconds before the code. This allowed the burn duration to be computed from the provided numbers. Additionally, the motor code was followed by a letter designation denoting the type of propellant. The propellant designations are manufacturer specific. This standard is still not fully adopted, with some manufacturers adopting parts or all of the additional nomenclature.


Motor impulse by class


Governmental regulation

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. These regulations are codified in FAA FAR Part 101. Rockets under 125g propellant and 1500g liftoff mass are exempt from most requirements. Beyond that a free "Waiver" is required from a FAA field office. 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 The National Fire Protection Association (NFPA) is an international nonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards. As of 2018, the NFPA claims to have 50,000 mem ...
(NFPA) "model" code documents, which are adopted only in specific circumstances and jurisdictions, largely in conjunction with fire and building codes. This self-regulation of industry suggests a user to become certified for use before a manufacturer will sell him a motor. In the United States, the two recognized organizations that provide high-power certifications are
Tripoli Rocketry Association The Tripoli Rocketry Association (TRA) is an international organization and one of the two major organizing bodies for high power rocketry in the United States. History Tripoli Rocketry Association was founded in 1964 in the Pittsburgh, Pennsy ...
and the
National Association of Rocketry The National Association of Rocketry (NAR) is a non-profit tax-exempt scientific organization dedicated to consumer safety, youth education, and the advancement of technology in the hobby of sport rocketry in the United States. Founded in 1957, t ...
. 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. With the national member association bodies using published safety codes. In Canada, the Canadian Association of Rocketry has a four-step certification process, but all three organizations accept the other's certifications if a flyer shows up at a high-power launch and wishes to fly under their sanction. Level 1 certification from NAR or TRA qualifies one to purchase and use an H or I motor, Level 2 certification J, K, and L motors, and Level 3 certification M, N, and O motors. Canada adds another step in between, and has a Level 4 which is the same as US Level 3. In the late 1990s, the U.S.
Bureau of Alcohol, Tobacco, Firearms and Explosives The Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), commonly referred to as the ATF, is a domestic law enforcement agency within the United States Department of Justice. Its responsibilities include the investigation and prevent ...
began requiring that individuals obtain a Low Explosives Users Permit (LEUP) to possess and use high-powered motors. 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 Ammonium perchlorate composite propellant (APCP) is a solid-propellant rocket fuel. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur, not only in chemical composition and overall performance but also ...
(APCP) as an explosive. APCP is used in most high-power rocket motors. The commentary by BATFE staff in response to objections to adding new enforcement against hobby rocket motors is quite instructive. 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. That judgement established 1 meter per second burning rate ("ATFE’s own burn rate threshold for deflagration is 1000 millimeters (or one meter) per second." Tripoli Rocketry Ass’n, 437 F.3d at 81–82) as the threshold for a material on the BATFE list of explosive materials.


Vendors

The largest vendor of model rocket motors in the world is
Estes Industries Estes Industries is a model rocket company that was started in Denver, Colorado, USA. The company was the first to mass-produce model rocket engines with consistent and reliable performance. It is popular among hobbyists of experimental amateur ...
. The largest vendors of high-power rocket motors in the world ar
Cesaroni Technology Inc.
an
RCS Rocket Motor Components, Inc.
The very first model rocket motor certified was by Model Missiles Inc. (Orville Carslile). Circa 1958. The very first high-power rocket motor certified was b
U.S. Rockets
(Jerry Irvine). Circa 1985. The very first APCP propellant model rocket motor made was by Rocket Development Corporation (Irv Wait). Circa 1970. The largest vendor of professional solid rockets in the world is
Orbital ATK Northrop Grumman Innovation Systems (NGIS) was a sector (business segment) of Northrop Grumman from 2018 through 2019. It was formed from Orbital ATK Inc. a company which resulted from the merger of Orbital Sciences Corporation and parts of Alli ...
.


See also

* Jetex (Aerodynamic lift) *
High-power rocketry High-power rocketry is a hobby similar to model rocketry. The major difference is that higher impulse range motors are used. The National Fire Protection Association (NFPA) definition of a high-power rocket is one that has a total weight of more ...
*
Model rocket A model rocket are small rockets designed to reach low altitudes (e.g., for model) and be recovered by a variety of means. According to the United States National Association of Rocketry (NAR) Safety Code, model rockets are constructed of p ...
*
Solid-propellant rocket A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persians ...


External links


National Association of Rocketry (NAR) - Model Rocketry and High-Powered Rocketry Certifications

Tripoli Rocketry Association (TRA) - High-power rocketry Certifications

Canadian Association of Rocketry (CARWeb) - Model Rocketry and High-Powered Rocketry Certifications in Canada

United Kingdom Rocketry Association - High-power rocketry Certifications


References

{{DEFAULTSORT:Model Rocket Motor Classification Model rocketry