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The Challenges of a Successful Rocket Flight

Rocket Debrie
There are so many different rocket motors available with such varying impulse ranges and propellant characteristics that it can become overwhelming to any potential rocketeer. There are hybrids, Ammonium Perchlorate Composite Propellant (APCP), black powder, sugar . . .etc. Each has their benefits. APCP is the most common, but hybrids are quickly becoming popular due to lack of government interference, ahem,,, I mean regulation. For now, there are a few things right up front. First, the size should be already known at this point. The rocket was constructed with a 29mm, 38mm, 54mm ...etc. engine tube or adapter which dictates the size of the motor. Whew! That is one decision down.

The motor vendor is the next decision. Choosing a rocket motor vendor is much like choosing your child’s pediatrician, the church you will patronage, or who you will vote for in the next election. Once you purchase motor hardware from a vendor, you will be locked in with that vendor for your propellant reloads. There are no reliable methods of interchanging different vendor’s propellant reloads with other vendor’s motor hardware so choose wisely here. Some factors to consider are availability, cost, variety, and complexity.

Check with the flying club. Most flying clubs have regular vendors that sell motors that show up at launches. This is a good starting point as it can be expensive to have high power reloads shipped due to the 25 dollar hazmat fees.

Zipper Damage

Late apogee deployment led to zipper damage. Lucky that the rocket survived to be repaired. Not good!

Also, level 1 certification is required to purchase H-I motors, level 2 for J-L motors, and level 3 for M and above. However, most vendors will sponsor certification attempts. A Low Explosives User Permit (LEUP) from the Bureau of Alcohol, Tobacco, and Firearms (BATF) with onsite storage is no longer required since NAR/TRA won the lawsuit against the BATF in 2009. However, a LEUP is still required for most e-matches and igniters. Once certification is achieved, keep an ample supply of motors on hand to fly in case your favorite friend, the rocket motor vendor, is not available. This will prevent major disappointment after that 2-hour commute to your flying field. That rocket vendor onsite at the launches with plenty of motors to sell is very integral to your ability to shoot for the stars. If the club is lucky and has such a vendor, buy him a hot dog at the next launch and send him a Christmas card over the holidays. Do not forget the easier to obtain A-G class motors, which are just as challenging and fun to fly.

Next, we want the very best possible rocket engine, the kind that spits beautiful colors of the rainbow out of the nozzle, sparkles and crackles like a jake brake on steroids, and has the impulse and burn time to join the rovers on Mars, but . . . , we want it in the same price range as a pack of Estes D12. There might have to be some compromise here. When pricing motors out, consider cost of replacement parts for the hardware, shipping and hazmat fees if no onsite vendor, range of/and inclusion of delay charges, and availability of your best friend, the rocket motor vendor. Gas is very expensive for that 2-hour commute to the flying field just to watch other people fly, which can still be a lot of fun. Also, some propellant types are more expensive then other types so determine your requirements and pay accordingly.

There are propellants with green, red, and blue plumes, fire starting spark spitters, white or black smokies, warp speed blink and they are gone propellant, moonburners, and the list continues into orbit. Every propellant has a thrust curve that indicates burn time and thrust. As long as minimum 5:1 ratio (a 1 pound rocket requires at least 5 pounds of thrust) is met, then the rocket should achieve vertical liftoff. Different propellant types and various impulse ranges for your motor hardware allow a variety of flight possibilities for various conditions. Make sure the rocket can handle the motor, otherwise a really spectacular flight might occur.

The last thing to consider is simplicity of assembling the motor. Most motors are assembled on the flight line with spectators and rocket groupies asking questions, and rockets ascending and descending all around. One can easily become distracted and not realize the obvious difference between 1/16 and a 3/32 thick o-ring. Get them wrong and the difference becomes all too apparent. Some motors have threaded closures and others have snap rings. Practice assembling before launch day. Sometimes I assemble the motors in the comfort of home and take the assembled motor to the launch. The launch field is standing by for our newly constructed rocket loaded with a high power motor purchased from our new best friend, the rocket motor vendor. Do not forget the Christmas card. Now it is time to start thinking about recovering your rocket.


Sometime debris will litter the flying field after a really spectacular flight. Not good!

By Peter E. Abresch Jr.
Choosing Your Rocket Engine

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