I installed a bicycle valve in the cap of a 2 liter pop bottle,
pumped it up to 100 PSI, and then burst the bottles by shooting an
arrow through them with my
home made crossbow.
For added effect I filled the pop bottles with wood shavings.
The wood shavings pack loosely, so there is lots of air between them to spread them
once the bottle bursts.
Simple water bottle rocket
I drilled a small 3/16 (4.5 mm) hole in the cap of a pop bottle.
With the bottle filled half way with water, I
stuck the compressor nozzle in the hole, pumped it up, and let it go.
There isn't much in the way of directional stability.
Fins would help, but that would be more work and add weight,
which would make it not go quite as wild.
