How does the military test their ballistic missiles? By using a potato cannon. A new testing device developed by the U.S. Navy is a super sized version of the potato gun, which offers a low cost alternative by simply shooting stuff out of a few pipes.
Developed at the Naval Air Warfare Center in China Lake, CA, the Variable Energy Research Accelerator (VERA) is a transonic impact gun for use in ordnance development labs. The gun was built to launch live or inert missile and bomb components at transonic speeds (below the speed of sound). Check out the video below:
The gun has a 40-foot long barrel and a 19-inch diameter bore, which is very useful for shooting oddly-shaped projectiles. According the YouTube videos's poster Inigo93,
It's what's known in the potato gun world as a hybrid. It uses both compressed air and combustion to operate. Basically, throw some compressed air and fuel into a chamber and light a match. 'Tis very similar to the inner workings of an internal combustion engine. I just use propane instead of gasoline and my "piston" isn't attached to a crank shaft.
The gun can fire projectiles weighing up to 200 pounds with as much as 2.25 megajoules of energy, which is equivalent to shooting a 100 pound load at 1000 feet per second.