Back in highschool I had a friend that built a potato gun out of a black PVC pipe, an igniter, and a can of hairspray.  You’d put the potato in the front end and it would create a seal, then you’d fill the back end with hairspray, screw the cap on, and whoola, a home-made bomb…I mean spud cannon.  Keep in mind that these things are dangerous, and I in no way condone their use, except under the guidance of resposible adult supervision…we had more than our fair share of incidents, everything from burnt hair, to our back cap blowing off and narrowly missing one of our group…they can be dangerous, so if you’re so inclined to build one, please take precautions.  That said, they are really cool to see in use, and it’s a great way to learn about the science of things…well combustion anyway. 

For a simple example, check out this site.  It’s similar to the gun we made in school…though hopefully these guys were a little bit smarter about it than we were…though by the looks of it, I wouldn’t count on it…

For those of you that think you’re beyond this stuff…well…just check out this page and dare to reconsider.