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Composite model rocket engines

Model rocket engines are rated from a baseline of 2.5 Newton-seconds of impulse, denoted as "A". Impulses between letters are rounded up to the next letter. Each successive letter is double the last letter's impulse, so an F engine is 2x the impulse of a E, and 32x that of an A. The letter is followed by a number which gives average thrust, in Newtons. A special permit is requred to fly anything larger than G size. Delay is denoted by a number after a dash; this is the delay time in seconds. After the delay, a charge bursts through the top of the engine to deploy the parachute or other recovery system.

Aerotech adds a letter to the end of each engine denoting which of their three varieties of propellant mixtures it uses.

Aerotech makes engines with composite propellants, which they claim have up to three times the energy of black powder by weight. They make disposable engines in D through G size, and motors with reusable casings and replacable propellant grains in D through M size. They also make a J size solid-liquid hybrid which uses composite fuel and nitrous oxide liquid.
Aerotech engine?
Engine statistics
Specification F50-4T disposable H180W reloadable J210H hybrid
Propellants Blue Thunder composite White Lighning composite N2O/composite
Total impulse 80 N-s 230 N-s 850 N-s
Average thrust 50 N 180 N 210 N
Burn time 1.6 s 1.27 s 4.05 s
Total weight 83 g 263.6 g 1497 g
Propellant weight 38.3 g 123 g 172 g fuel / 299 g N2O