Rocket Project v1

This was our first rocket, so we were learning as we went and trying new tools and materials. We chose to 3D print almost all of it: our team already knew 3D printing well, and it was the cheapest option for high school students on a limited budget.

We started from an existing printable model on Thingiverse because it looked the easiest to build. I reprinted it at 150% for a bigger rocket, but the model had no room for avionics, and I wanted onboard electronics. That's where my part started.

v1 was meant to hold two PCBs, one on each side, but it was very bulky. v2 simplified things and fit both boards, but it was too heavy for the rocket. v3 used less space, but the batteries sat too high and threw off the center of mass.

v4 solved those problems and lasted a while, but I wanted to save more weight. v5 isn't fully printed: carbon rods support the top and bottom plates, which cuts weight a lot and also gives the batteries support between the PCBs.

The boards needed to log altitude and temperature, record when the parachute deploys, detect apogee, and fire the parachute charge. We used an Arduino Nano, an Adafruit MPL3115A2 for altitude and temperature, and an onboard SD card for data. Each PCB was kept to 30 mm wide to fit the tray.

The deployment board was first inspired by Richard Nakka's experimental rocketry timer, using a 556 dual-timer IC to trigger a fuse. When the boards arrived we realized that was more complicated than we needed, so version 2 uses a relay driven by a transistor, controlled directly by the Arduino.

Fully built, the empty rocket weighed 264 g, too heavy for a small C6-5 motor. I set a target of under 200 g. The resin-printed nose with its hook looked great but was bigger and heavier than it needed to be, so I redesigned it with two small square mounts on top for the parachute instead of rings.

The middle body tube kept its shape but was cut down to fit the ~110 mm avionics tray. Most of the weight was in the fins, so we tried casting them in molds with three materials: one carbon-fiber composite with lots of air bubbles, a polyurethane that was too heavy, and a carbon-fiber epoxy that was much lighter.

For parachute deployment we designed small printed capsules that hold a charge and packing paper, with a hole on top for a fuse, then built test rigs to try them inside the actual airframes. We also ran ground tests of the electronics sled.

In OpenRocket, the design was predicted to reach an apogee of 243 m with an E16 motor, with a maximum velocity of about 70 m/s.