Model rocket motor classification

Motors for <a href="/facts/Model_rocket/v9TmSyAy">model rockets</a> and <a href="/facts/High-power_rocketry/UIqWeoxh">high-powered rockets</a> (together, consumer rockets) are classified by total <a href="/facts/Impulse_(physics)/maePm9Ua">impulse</a> into a set of letter-designated ranges, from 1⁄8A up to O.
The total impulse is the integral of the thrust over burn time.

P
          
            T
          
        
        =
        
          ∫
          
            0
          
          
            t
          
        
        
          F
          
            t
            h
            r
            u
            s
            t
          
        
        (
        
          t
          
            ′
          
        
        )
        d
        
          t
          
            ′
          
        
        =
        
          F
          
            a
            v
            e
          
        
        t
        .
      
    
    {\displaystyle P_{T}=\int \limits _{0}^{t}F_{thrust}(t^{\prime })dt^{\prime }=F_{ave}t.}

Where 
 
 
 
 t
 
 
 {\displaystyle t}
 
 is the burn time in seconds, 
 
 
 
 
 F
 
 t
 h
 r
 u
 s
 t
 
 
 
 
 {\displaystyle F_{thrust}}
 
 is the instantaneous thrust in newtons, 
 
 
 
 
 F
 
 a
 v
 e
 
 
 
 
 {\displaystyle F_{ave}}
 
 is average thrust in newtons, and 
 
 
 
 
 P
 
 T
 
 
 
 
 {\displaystyle P_{T}}
 
 is the total impulse in newton seconds.
Class A is from 1.26 <a href="/facts/Newton-second/8RDrLRf5">newton-seconds</a> (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 <a href="/facts/Amateur_rocketry/Pg5VyXqd">amateur rocketry</a> (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.

Model rocket motor classification open-in-new

Model rocket motor classification