August 2005, Issue 181

Flight Computer for High-Power Rocketry

LEVEL 1 CERTIFICATION

Most of us involved in high-power rocketry started out working with model rocket kits and motors. But high-power rocketry is different than model rocketry. According to the NAR, a high-power rocket must have either a motor with more than 160 newton-seconds (Ns) of total impulse (an H motor or larger) or multiple motors working together to exceed 320 Ns. The motor must also have an average thrust in excess of 80 N. Lastly, the rocket must weigh more than 1,500 g or include airframe parts of ductile metal.

You must be certified to launch high-power rockets. Level 1 certification is the first step. You should first check out the high-power rocket safety code (www.nar.org/NARhpsc.html). Then, join a local rocket club and attend a launch. The process of Level 1 certification is started by purchasing a Level 1 class motor (H and I). You should then buddy up with someone who can help you prepare your rocket for its first flight.

On flight day, you’ll obtain your motor reload. Load your motor casing, pack the chute, fill out your flight card, and head out to the range safety officer (RSO) table. One tip: Don’t install the igniter in the motor reload until you have cleared the RSO table and your rocket is on a launch pad. For any certification flight, you’ll need someone with Tripoli or NAR “prefect” status to monitor your RSO check, launch pad preparation process, and launch. This person will later sign off on your certification paperwork.

Okay, so how did I get certified? First, I made the mistake of buying a Public Missiles, Ltd. (PML) AMRAAM 4 rocket kit with a dual-deployment system, which turned out to be too big and complicated for my first project. Next, I joined the Association of Experimental Rocketry of the Pacific (AERO-PAC) and attended my first launch in 2003 in the Black Rock Desert in Nevada. The event brought me up to speed on all the terms, hardware, and procedures. I then joined Tripoli, NAR, AERO-PAC, and paid for a Low Explosive Use (LEU) permit. The total cost for joining the groups and a three-year LEU permit was approximately $320. During the six-month period that followed, I pored over all the written material I could get my hands on.

I finally ended up purchasing a PML AMRAAM 2 Level 1 rocket kit and a 29-mm Dr. Rocket motor casing (see Photo 1). I also bought RocFlight software for flight simulation. The software simplifies the entire process. By inputting my rocket’s size, weight, drag, motor size, and type, I got its speed, altitude, and Gs.