Compressed air rocket that (hopefully) twirls down to minimize the maximum velocity of the projectile as it plunges back to Earth. Designed to fit the 3/8" tube from an AirRocketWorks.com launcher.

WARNING: While this rocket has been tested at a 120psig launch using PLA, your results may vary depending on printing parameters and material.

The launch was successful. Unfortunately, it did not twirl down, or launch vertically due to the flexible nature of the fins. An additional support was added (using soldering iron & raw filament) to prevent over-flexing of the fins prior to apogee. The final result was that the rocket once twirled (only upwards) and generally performed a tumbling descent, which limited the impact velocity. After several launches, the fins were fixed to the sides of the rocket just to see the flight characteristics of the rocket without tumbling. The rocket flew very well, right into the street and smashed.

I built my own launcher based on these instructions and the pictures here.

Print 3 fins and one rocket tube.

The holes for the hinges are designed to fit 1.75mm filament, but might require a little drilling after printing (mine did).

Use a soldering iron at 200C to "glue" the filament in place after verifying the fins can still rotate.

Find an appropriate sized rubber band to provide slight upward pressure on fins. The idea is to allow drag to keep the fins down, until near apogee, then the rubber band will pull the fins out just enough to promote the twirling action, which further pivots the fins.