An electric current is passed through water, reducing it into its constituents of hydrogen and oxygen. The gasses can then mixed in a combustion chamber and ignited to fire a projectile. The Exploratorium version of this exhibit fires a ping-pong ball into the air, and catches it in a large net. A version of this exhibit was sent to NASA visitor center that launches a model of the Space Shuttle along a vertical guy-wire to a height of almost twenty feet.