This was an idea I'd had floating around for several years before I got around to building it. I originally designed it half this size, intending for a 1-meter strand of NeoPixels to go around the outer rim, but later upscaled it 2x and got a 2-meter strand.
All of my design files are on GitHub. The saucer as I built it has a 3 inch body tube 100 mm long, around a 29mm motor mount. Five basswood fins support the top skin, which is silver-colored posterboard, and the outside ring, which is 3D-printed. The dome on top is also 3D-printed. The lights (the NeoPixel strand around the outside and four green LEDs under the dome) are powered by a 400 mAh LiPo battery, and the NeoPixels are controlled by an Adafruit Trinket on a carrier PCB that I designed. The purpose of the carrier was to connect an 8-position DIP switch to allow lighting colors and patterns to be changed in the field, and to bring together the connectors for the battery and the LEDs. The Trinket is programmed in Arduino C.
Initially I had planned to have the dome pop off like a conventional nose cone and deploy a drogue parachute, to ensure that the rocket came back down nose-up, allowing the drag of the saucer itself slow its fall. However, once I had it built, I could not find a satisfactory way to fit any parachute (or even a streamer) in the amount of interior space I had. I then decided to try a rear-ejection approach, friction-fitting the motor and letting the ejection charge pop it out on a tether. I hoped in this configuration, the weight of the motor (plus additional weight I attached to the tether) would cause the rocket to fall nose-up. In the first flight, this did not work either (the rocket's flight was so short, the ejection charge went off after it landed), but it turned out that it was stable enough falling nose-down that no other recovery deployment is needed. (I had been concerned that it might fall edgewise, but it doesn't appear that this will be a problem).
The current build has a few issues; the first being the most important thing I need to solve before I fly the rocket again. The others I will probably just keep in mind if I ever build a second one.
- The first flight showed that the rocket really needed a bigger motor. I would like to try a G79 for the next flight, but it won't currently hold a motor that long. I will need to either get the nose cone / dome loose (it's currently glued into the motor tube with CA) so I can cut the shoulder off to make more room, or just cut the dome off and print a new one without a shoulder.
- The top surface of the saucer is made of poster board, which looked good at first but wrinkled up the first time I took it outside into humid air. I'd like to find a different material that would not be prone to wrinkling but still be lightweight.
- The wiring of the dome LEDs is quite messy. I was running all of the wires around the outside of the body tube when I was still trying to save space inside for a parachute, and ended up with excess that I just glued to the tube with CA. A re-design would put all of the wiring inside the tube where it wouldn't show.
Ordering the controller PCBs from OSH Park.
Manufactured controller PCB with all components soldered in.
Finished rocket in the workshop prior to first flight.