First......A little Rocket Science:

Each motor has two numbers associated with it, example 38/360. The first number, 38 in the example, is the diameter of the motor in millimeters. You want to be sure your rocket accepts (or has an adapter for) motors of this size. The second number, 360 in this example, is the total impulse of the motor in newton-seconds. What's a newton? It's a metric measurement of thrust; 4.45 newtons = 1 pound. So there are 80 pound-seconds in the 360 casing.

Now let's talk about pound-seconds. I'll continue using pounds rather than newtons since we are more comfortable (at least I am) with pounds. A motor with a total impulse of 80 pound-seconds can put out 80 pounds of thrust for 1 second, or 40 pounds of thrust for 2 seconds, or 20 pounds of thrust for 4 seconds. See the relationship? Pounds of thrust times burn time equals total impulse. 40 pounds times 2 seconds equals 80 pound-seconds. What this means is you can get a large average thrust out of a short burn time or a small average thrust over a long burn time. In either case, short or long burn time, the total impulse, 80 pound-seconds in this example, will be the same.

An understanding of this is important when it comes time to choose a motor for a particular rocket. You should have a MINIMUM thrust to weight ratio of 5. A 4 pound rocket should use a motor that produces an average thrust of at least 20 pounds. Using too small a motor can produce an unstable and dangerous flight.....the rocket comes off the rod so slowly the fins cannot provide guidance.

Aerotech produces three propellant formulations, Black Jack (abbreviated "J"), White Lightning (abbreviated "W"), and Blue Thunder (abbreviated "T"). Each of the three has different visual effects and thrust characteristics.

The Black Jack motors produce a thick, black smoke under thrust. No flame is visible, just black smoke coming out of the nozzle. These motors have the longest burn time and the lowest average thrust. Check your thrust to weight ratio carefully to insure the average thrust of the motor is at least 5 times the weight of the fully loaded rocket.

The White Lightning motors produce a bright orange flame and a dense white smoke. Of the three propellant types, these have intermediate burn times and intermediate average thrusts. They are easy to track because of the thick smoke.

The Blue Thunder propellant produces a bright blue/violet flame and little smoke. They have the shortest burn time and therefore the highest average thrust. Use these motors to get your heaviest rocket moving fast quickly.

A little more Rocket Science:

Each reload kit is labeled with a letter, a number, and another letter. There is actually another letter at the end that specifies delay time, short (S), medium (M) or long (L). We won't discuss delay times here, since that requires still more rocket science. Lets look at an example, say the H-180W. The H indicates the total impulse range of the motor; for an H the range is between 160 and 320 newton-seconds total impulse. Since the H-180W uses the 29/240 motor, 240 newton-seconds is between 160 and 320 so it's an H. The 180 specifies the average thrust of the motor in newtons. Remember, 4.45 newtons equals one pound so 180 newtons is about 40 pounds. Remember that we want at least a thrust to weight of at least 5. So, this motor can safely lift a fully loaded rocket that weighs 8 pounds maximum. Of course, lighter is better. A 6 pound rocket will have almost a 7G liftoff. The "W" specifies a White Lightning propellant.

MOTOR...............................USES RELOADS

29/60.....................................F-37W, F-62T
29/100...................................G-54W, G-104T
29/180...................................G-75J, H-128W, H-238T
29/240...................................H-97J, H-180W, H-220T

38mm

38/240...................................H-73J, H-123W, H-242T
38/360...................................H-112J, I-161W, I-357T
38/480...................................I-154J, I-211W, I-300T
38/600...................................I-195J, I-284W, I-435T
38/720...................................J-350W
38/1080.................................J-570W

54mm

54/852...................................J-90W, J-180T, J-275W, J-460T
54/1280.................................J-135W, J-415W, J-800T
54/1706.................................K-185W, K-550W, K1100T
54/2560.................................K-700W

75mm

75/2560.................................K-560W
75/3840.................................L-850W
75/5120.................................L-1120W
75/6400................................M-1315W

98mm