For miniature black powder rocket motors (13 mm diameter), the maximum thrust is between 5 and 12 N, the total impulse is between .5 and 2.2 Ns, and the burn time is between .25 and 1 second. For Estes ‘regular size’ rocket motors (18 mm diameter), there are three classes: A, B, and C. The A class 18 mm motors have a maximum thrust between 9.5 and 9.75 N, a total impulse between 2.1 and 2.3 Ns, and a burn time between .5 and .75 seconds. The B class 18 mm motors have a maximum thrust between 12.15 and 12.75 N, a total impulse between 4.2 and 4.35 Ns, and a burn time between .85 and 1 second. The C class 18mm motors have a maximum thrust from 14 – 14.15 N, a total impulse between 8.8 and 9 Ns, and a burn time between 1.85 and 2 seconds.