Rocket in a Bottle

This little rocket is a cartesian diver to illustrate the principles of pressure and buoyancy. Please put it in a clear bottle filled with water, close it and press the bottle to see the rocket fall and rise.
This print is a fine educational or desktop toy.

The rockets shape is inspired by the german V2-rockets but optimised for 3d printing. The model has a cavity in which air is trapped, just enough to hold the rocket upright in the water. When the bottle is squeezed, the trapped air is compressed, and water enters the rocket through the bottom canal. The buoyancy of the rocket is reduced, and thus it starts to sink. When you release the pressure, the air expands and pushes the water out of the rocket. The model now starts rising in the bottle.

The performance of this model is highly dependant on the specific density of your filament, so you have to experiment with different amounts of infill. I had success with infill between 30% and 50%.

After some time or rapid changes in pressure, the rocket could keep sitting at the bottom. This means that water has entered the infill section of your rocket. Just take it out and let it try for some hours, and it will work as before.

Experiment with your infill settings. For PLA filament, I have used 30% to 50% infill density.
Support and bed adhesion are optional.