I test fired my ping pong ball canon. This is an 8ft length of PVC pipe which is sealed on the ends with mylar held in place with a coupling. The air is drawn out with a vacuum pump. The Ping Pong Ball inside at one end. The mylar is punctured at that end. The air rushing in to fill the vacuum pushes the ball down the pipe and through the mylar at the other end.
Next I will build a rack to hold a few aluminum cans. Marc “Zeke” Kossover demonstrated his vacuum cannon at the Make Faire in 2009. It was very impressive to see a ping pong ball blow a hole in an aluminum can. I think it will be a hit at the fun with science night. A loud bang with some minor distruction is sure to be a hit. I wonder what a golf ball will go through?