Although I enjoyed launching my model rockets, I often wished they would do more than just go up and float down. One early payload, launched on the Estes Astron X-Ray with its clear plastic payload section, was a flashlight bulb wired directly to a double-A battery. Launched at night, this made for a very neat flight. Later came the Estes Camroc, giving rockets the ability to take photos. That was the extent of my payload launches until many years later when I got interested in rocketry again and bought a copy of the booklet "Advanced Model Rocketry," published by Kalmbach Publishing Co.

     One section of this book described a simple telemetry package for model rockets using a radio system available from Radio Shack. It occurred to me that I could use the transmitter from one of my son's radio controlled cars (which no longer ran very well, of course).

     Using the book as a guide, I wired an input device to the board where the control stick input was previously connected. I actually had two inputs that could be selected with a switch: a photocell and a thermistor. The photocell would pick up rotation in the rocket, while the thermistor would sense changes in temperature. Upon ground testing, both worked well.

     I selected the Estes Mega Sizz as my launch vehicle. This model came as a single stage, no-payload kit. First, I cut a 7" section of the upper body tube to create the payload section. Next, I added a booster stage designed to induce spin until it separated, at which time the rocket should stop spinning for the duration of the flight. Hopefully, the photocell would detect and transmit this change of state. Although the thermistor detected the difference between ice and my hand, heard as a difference in pitch in the transmitted signal, it was doubtful if it would sense any real change in atmospheric temperature within the rocket's flight altitude.

     I had set this whole thing up as a project to be shared with my son's science class at school. I went in before launch day and gave a presentation on rocketry and telemetry, and gave a demonstration of the sensors in action. On launch day we had to use a hand-held CB unit to pick up the signal. We held a tape recorder nearby to try to record the signal. We did the launch in photocell mode. If you listened very carefully, you could just make out the pulsing signal from the rotation of the rocket, then the steady signal as the rocket stabilized after the booster stage dropped off.

     I wouldn't call this a resounding success, but it was a fun project. Maybe I'll try to improve on the transmitter and try it again some day.


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