Model Rocket Motor Standards

« Introduction
4.1 Definition
Model Rocket motors must meet the requirements of the NAR Standards and Testing Committee and NFPA 1122.
4.2 Limits
A single solid propellant model rocket motor must not contain more than 125 grams of propellant, and must not produce any more than 160.00 Newton-seconds of total impulse.
4.3 Contest Approval
All motors used in a model rocket in NAR sanctioned competition, or for the purpose of establishing a United States Model Rocket Performance Record, must be listed in the NAR Certified/Combined Motor List found on NAR.org as holding NAR Contest Approval.
4.4 Alterations
A model rocket motor must not be altered in any manner that changes its dimensions and/or its performance characteristics. No material may be permanently affixed to the motor.
4.5 Classification
A model rocket motor is assigned a motor classification based on its mean sea level total impulse when tested at a temperature of 20 degrees Celsius. A motor becomes NAR certified when its test data is accepted by the NAR Standards and Testing Committee. NAR certified model rocket motor classifications are as follows:

Motor Class Total Impulse (N-sec)
1/8A 0.00 – 0.3125
1/4A 0.3126 – 0.625
1/2A 0.626 – 1.25
A 1.26 – 2.50
B 2.51 – 5.00
C 5.01 – 10.00
D 10.01 – 20.00
E 20.01 – 40.00
F 40.01 – 80.00
G 80.01 – 160.00

Note: All motor classes listed above will be recognized for certification purposes regardless of current commercial availability.

4.6 Published Values
The total impulse values published in the NAR Certified/Combined Motor List found on NAR.org will be the values used in all NAR sanctioned competition and for United States Model Rocket Performance Record attempts.
4.7 Total Impulse
When multiple motors are used in a single entry (e.g., clustering and staging), the total impulses of the individual motors must be summed to compute the total impulse of the configuration and to determine the impulse class of an event for which the entry qualifies. Only those motors actually intended to ignite and produce useful thrust are to be included in this total.
4.8 Acceptance
Only model rocket motors that are currently and readily available commercially, and meet the requirements of Rule 4.1 – Definitions, through Rule 4.3 – Contest Approval, and Rule 4.5 – Classification, through 4.7 – Total Impulse, shall be accepted for NAR contest approval.
4.9 Contest Use
NAR sanctioned competition allows the use of all contest approved motors for which the total impulse of the motor is appropriate for the event and in compliance with state and local laws. Booster stage, single stage, and upper stage motors may be used in locations other than their primary intended stage.
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