How does it work?

The potato cannon works on the same principles that an internal combustion engine works. When the cannon is loaded a finite amount of fuel is confined to a finite amount of space. When you ignite it the fuel excites and combusts. The chemical reaction releases a great amount of energy, creating rapidly expanding gasses. The pressure in the chamber increases, pushing the potato out of the barrel. Who knew science could be this much fun?

Maybe one day I will put some graphics on this page, but for now you can check out a little animation from how stuff works.com that illustrates the process pretty well.