Model Rocket Launchers

  Model 2 Model 1
I designed and built this model rocket launcher when I was in 9th grade. This was my first scratch-built project as I was learning digital circuits.

This launcher was very basic and did a simple count down from 9, then launched the rocket.



Operation

The green light indicated the power was connected. The yellow light indicated the igniter clips were touching the metal blast deflector which would also stop the count. The red light indicated the igniter was connected.

The rotary switch allowed for one of three pads to be selected for launch.

The jack just under the count was used as a "key". The count would not proceed until the key was inserted.

The right switch, when flipped on, would set the count from blank to nine. When the switch was flipped off the count would begin. When the count reached zero it would launch the rocket, then once second later the display would blank.

I believe the left switch turned on the igniter power, but I don't remember at this point.

The three connectors on the top went to each of the three pad igniters. The top jack on the right side connected to the metal blast deflectors on each pad. The bottom side jack was the primary car battery power.

The jack on the left connected to secondary power which kept the unit operating when the igniter was heated.

Issues

Before adding the secondary power supply, the unit would get confused when the igniter was heated. I didn't know why at the time, so I added a second small battery for the digital circuits that was isolated from the igniter. In hindsight, the real issue was the small 18 awg wire I used for the primary power. When the igniter was heated it would draw so much current the voltage would drop too low. The correct solution would have been to simply use much heavier gauge wire.

In the photo above, the primary power jack no longer worked. The seconary power still powered the digital circuits so the display lit up, but it would no longer count down. Not surprising considering how old this launcher is.