Scientific rocket from 1970's

thingiverse

This old rocket from my childhood still gets me fired up! You just print it out, pour some vinegar down the tube, stuff a ball of baking soda (Arm & Hammer's the best) into the end, then attach the base while the rocket's still pointing downwards. When you flip it over, the acid mixed with the powder kicks in after a few seconds and whoosh - up in the air it goes! Make sure there's some space inside the tube for air to compress or your lift won't be so high.