This is one I was considering building just for myself. A series of clear tubes (let's say 5) is set up with ping pong balls lightly stopping the top. In the tubes is butane/air mix, and two electrodes. Under each tube is a photodiode/transistor/resistor. When it is hit by the laser pointer the sudden change in light level is registered and a spark is sent through the according tube. The butane ignites and BANG the ping pong ball flies into the air. This, of course, is a totally useless waste of time, but it sure beats those boring desk toys doesn't it? The tubes would probably have to be manually filled back up with butane or dimethyl ether or propane from some sort of a bottle or can. Some of those ozone friendly dust off cans work pretty well in spud guns, and this is basically a smaller version.
-- brewer, Jun 04 2004

[BB] For whimps it is just hot air that drives the ball. There should be enough of that around in any major company.
-- kbecker, Jun 06 2004


What about some type of piston that causes a strong puff of air that can be reset without "manually filling back up with butane or dimethyl ether", or even a compressed air source. But I like the idea. +
-- Dickcheney6, Feb 13 2011



random, halfbakery