Motors for model rockets and high-powered rockets are classified by total impulse, the integral of thrust over burn time, into letter-designated ranges from 1⁄8A up to O. Total impulse (PT) in newton-seconds is calculated as the integral of instantaneous thrust over burn time, or equivalently average thrust times burn time. Class A motors range from 1.26 to 2.5 N·s, and each subsequent class doubles the total impulse, with Class M ranging between 5,120.01 and 10,240 N·s. Motors up to Class E are low power, Classes F and G mid-power, and H and above high power. Motors beyond O fall into amateur rocketry, involving independent non-commercial rocketeers.
Rocket motor codes
The designation for a specific motor looks like C6-3. 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.
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.3 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
| Class (Base 26) | Total Impulse (N·s) | Total Impulse (lbf·s) | Aerospace Vehicle or Rocket(s) | US Requirements |
|---|---|---|---|---|
| Micro | 0–0.3125 | 0–0.07 | ||
| 1/4A | 0.3126–0.625 | 0.071–0.14 | ||
| 1/2A | 0.626–1.25 | 0.141–0.28 | ||
| A | 1.26–2.50 | 0.281–0.56 | ||
| B | 2.51–5.00 | 0.561–1.12 | ||
| C | 5.01–10.0 | 1.121–2.25 | ||
| D | 10.01–20.0 | 2.251–4.5 | ||
| E | 20.01–40.0 | 4.51–8.99 | Most Water Bottle Rockets | |
| F | 40.01–80.0 | 8.991–18.0 | ||
| G | 80.01–160 | 18.01–36.0 | Invictus | Largest model rocket motor according to TRA and NAR. |
| H | 160.01–320 | 36.01–71.9 | Level 1 Certification required for purchase, available from Tripoli or NAR. Under 125g propellant is Federal Aviation Administration exempt. | |
| I | 320.01–640 | 71.9–144 | THRUST TU-1 rocket4 | |
| J | 640.01–1,280 | 144.01–288 | Level 2 Certification required for purchase, available from Tripoli or NAR. | |
| K | 1,280.01–2,560 | 288.01–576 | ||
| L | 2,560.01–5,120 | 576.01–1,151 | ||
| M | 5,120.01–10,240 | 1,151.01–2,302 | Level 3 Certification required for purchase, available from Tripoli or NAR. | |
| N | 10,240.01–20,480 | 2,302.01–4,604 | High Steaks5 | |
| O | 20,480.01–40,960 | 4,604.01–9,208 | ||
| P | 40,960–81,920 | 9,210–18,400 | UCLA Rocket Project's Grand Larceny NZRA - The Nike - Flight 1 | |
| Q | 81,920–163,840 | 18,400–36,800 | NZRA - The Nike - Flight 2 | |
| R | 163,840–327,680 | 36,800–73,700 | USCRPL's Traveler IV6NZRA - The Nike - Flight 3 | |
| S | 327,680–655,360 | 73,700–147,000 | WAC Corporal CSXT GoFast7 | Largest motor used by amateurs.8 |
| The following classifies professional propulsion systems using amateur motor codes, which are not used in industry. | ||||
| T | 655 k–1,311 k | 147,000–295,000 | ALSOR (Air Launched Sounding Rocket) | 200,000 lbf-s (889,600 N·s) is the limit for FAA definition of an "amateur" rocket 9 |
| U | 1,311 k–2,621 k | 295,000–589,000 | Apollo launch escape rocket | |
| V | 2,621 k–5,243 k | 589,000–1,180,000 | Bloodhound SSC hybrid rocket10 | |
| W | 5,243 k–10,486 k | 1,180,000–2,360,000 | SS-52011 | Smallest orbital rocket12 |
| X | 10,486 k–20,972 k | 2,360,000–4,710,000 | Lambda 4S13 | |
| Y | 20,972 k–41,943 k | 4,710,000–9,430,000 | VanguardGEM-40 SRBElectron14 | |
| Z | 41,943 k–83,886 k | 9,430,000–18,900,000 | Black ArrowMercury-Redstone15Pegasus-XL16 | |
| AA | 83.89 M–167.8 M | 18,900,000–37,700,000 | Falcon 117Minotaur I18VLS-119 | |
| AB | 167.8 M–335.5 M | 37,700,000–75,400,000 | M-V20Minotaur-C21Strela22 | |
| AC | 335.5 M–671.1 M | 75,400,000–151,000,000 | Ariane 323Titan IIDnepr24 | |
| AD | 671.1 M–1,342 M | 151,000,000–302,000,000 | VostokDelta IIFalcon 9 v1.0 | |
| AE | 1,342 M–2,684 M | 302,000,000–603,000,000 | Falcon 9 v1.1Falcon 9 Full ThrustDelta IV Heavy | |
| AF | 2,684 M–5,369 M | 603,000,000–1,210,000,000 | Atlas V HeavyFalcon HeavyNew Glenn25 | |
| AG | 5.369 G–10.74 G | 1.21*109–2.41*109 | Space ShuttleSaturn VSpace Launch System | |
| AH | 10.74 G–21.47 G | 2.41*109–4.82*109 | Ares VLong March 9Starship Block 1 | |
| AI | 21.47 G–42.95 G | 4.82*109–9.64*109 | Starship Block 3 | |
| AJ | 42.95 G–85.9 G | 9.64*109–19.3*109 | Sea DragonUR-700M | |
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 (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 and the National Association of Rocketry. 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 began requiring26 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 (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.27 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.28 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.29
Vendors
The largest vendor of model rocket motors in the world is Estes Industries. The largest vendors of high-power rocket motors in the world are Cesaroni Technology Inc. and 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 by 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.
See also
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
NAR website: http://www.nar.org/safety-information/model-rocket-safety-code/ http://www.nar.org/safety-information/model-rocket-safety-code/ ↩
NAR website: http://www.nar.org/safety-information/high-power-rocket-safety-code/ http://www.nar.org/safety-information/high-power-rocket-safety-code/ ↩
USR website FS photograph: http://v-serv.com/usr/motors/images/CinerocFS5.jpg http://v-serv.com/usr/motors/images/CinerocFS5.jpg ↩
"TU-1 Development". YouTube. 14 December 2023. Retrieved 2024-03-01. https://www.youtube.com/watch?v=2YIaAHpn4P4 ↩
BPS.space (2025-05-02). I Cooked Meat by Launching It To Mach 3. Retrieved 2025-05-05 – via YouTube. https://www.youtube.com/watch?v=9UX7NJLYyb4 ↩
"Traveler IV". USCRPL. Retrieved 2019-10-16. http://www.uscrpl.com/traveler-iv ↩
"GoFast". www.astronautix.com. Archived from the original on December 27, 2016. Retrieved 2017-11-24. https://web.archive.org/web/20161227201705/http://astronautix.com/g/gofast.html ↩
"Civilian Space eXploration Team". http://www.ddeville.com/derek/CSXT.htm ↩
"ECFR". Retrieved 2020-09-09. https://www.ecfr.gov/cgi-bin/text-idx?SID=2db213e14546c42a51edbee07409231c&mc=true&node=se14.1.1_11&rgn=div8 ↩
"Falcon Project Ltd. UK Bloodhound SSC test firing". Telegraph. 3 October 2012. Archived from the original on 2021-12-13. Retrieved 3 July 2015. https://www.youtube.com/watch?v=GOKw-bHMc2w ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Graham, William (3 February 2018). "Japanese sounding rocket claims record-breaking orbital launch". NASA Spaceflight. Retrieved 3 February 2018. https://www.nasaspaceflight.com/2018/02/japanese-rocket-record-borbital-launch/ ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
Space Launch Vehicles - Total vacuum impulse https://web.archive.org/web/20180923052249/http://www.b14643.de/Spacerockets/Specials/Impulse/index.htm ↩
"Commerce in Explosives--Amended Definition of Propellant Actuated Device". Federal Register. 13 February 2009. Retrieved 4 July 2015. https://www.federalregister.gov/articles/2009/01/14/E9-578/commerce-in-explosives-amended-definition-of-propellant-actuated-device-2004r-3p ↩
"Commerce in Explosives-Amended Definition of "Propellant Actuated Device" (2004R-3P)". Federal Register. 13 February 2009. Retrieved 4 July 2015. https://www.federalregister.gov/articles/2009/01/14/E9-578/commerce-in-explosives-amended-definition-of-propellant-actuated-device-2004r-3p#h-11 ↩
"APCP not an explosive, rules Judge Reggie B. Walton" (PDF). Federal Judge. 16 March 2009. Retrieved 3 July 2015. http://www.v-serv.com/usr/ATFE-03-16-09.pdf ↩
"2014 List of Explosive Materials (Official)". Federal Register. 7 October 2014. Retrieved 4 July 2015. https://www.federalregister.gov/articles/2014/10/07/2014-23870/commerce-in-explosives-2014-annual-list-of-explosive-materials ↩