Sport Rocketry

30 MAY/JUNE 2024 SPORT ROCKETRY ignites the propellant inside the rocket mo- tor. Launch controllers must be designed with features that ensure only authorized users can operate them. If someone pre- maturely gives the controller the signal to launch while someone else is working at the base of the launch pad, a safety inter- lock prevents the firing signal from reach- ing the igniter, saving someone from pain- ful burns, or at least from having to change their pants. Typically this interlock in- cludes a key of some kind, which is carried separately from the launch controller and must be inserted prior to the final action that completes the electrical circuit, such as the press of a button. I had become pretty bored with the big red button I had included in my high school-era launch controller built from RadioShack components. A few years ago I realized I needed a new one to take my rocketry to a higher level. I had been wanting a launch controller that uses only a key. I thought about using an old igni- tion switch from a car. is would allow the operator to insert the key, turn it "on" to arm the system, and then turn it all the way over to the "start" position to send the firing energy. Being spring loaded, the key would return from the start position to the "armed" position aer lioff. In 2021, when my obsession with the Titan II missile system began in earnest, I had my answer: Two keys! With Titan II, a launch was initiated by the simultaneous turning of two keys, each against spring tension. ese key operated switches were located far apart, so that two people were required to send the signal to the computer. Additional safeguards were in place, to ensure that not even Air Force personnel with knowledge of the system's inner workings could launch a rogue mis- sile. e central safeguard was a secret un- lock code, kept only with and sent only from the President of the United States as part of the order to launch. is code, a string of six letters of the alphabet, was entered by rotating lettered wheels, similar to a combination lock. Each wheel had six- teen letters from which to choose, making nearly seventeen million possible combi- nations. Only one would unlock a valve on the missile and allow propellant to flow to the engine. If a few incorrect combinations were entered, the unit would self-destruct, permanently disabling the missile. My model launches don't require this level of security, but I did want to have some fun by pretending to follow a few as- pects of a simulated launch. With the gen- As I've learned through an explosive ex- perience in 2003, fuses are for fireworks. We don't use fuses in model rocketry. We launch on command, at the end of a count- down, which can be paused at any point that something becomes unsafe, such as a gust of wind knocking over the rocket, per- haps pointing it toward the spectators, or because of a low flying aircra approaching the flying field at the last second. e launch controller is the device that supplies the electrical power to light the fire at the bottom of the rocket, causing it to launch at the end of the countdown, on command. It does this by heating a small wire to glowing white-hot, like the filament in an incandescent light bulb. e wire is dipped in something similar to a match head, creating a small burst of flame that Figures 1-3. e launch controller case, with drawer-pull handles added to front and rear. By Bryce Gorrell Titan II Launch Controller Figure 1.

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