Flutterby™! :

The pictures continue: In another vain attempt to look cool by hanging out with cool people, here are some pictures of me and Loren Carpenter playing with Loren's liquid nitrogen bottle rocket launcher at Pixar last fall. The launcher will theoretically launch 5 gallon water cooler bottles (its predecessor did), but we were launching 1 and 2 liter soda bottles and 1 gallon milk jugs. Of course immediately after this we got to talking about more convenient gasses than liquid nitrogen, which is expensive and needs to be transported in an open container. We settled on liquid propane, which opened up the possibility of using liquids other than water for the reaction mass [nudge, nudge, wink, wink]. Loren built the EjacuLauncher, with a heater to compensate for the low vapor pressure of propane and an electric valve system. He was firing off bottles at Burning Man, but because he was unsure of the spark ignition system hasn't yet used gasoline or similar as the reaction mass.