- Created on Tuesday, 12 February 2013 16:41
- Written by Jim Schenke
West Lafayette, Indiana - A Purdue University mechanical engineering technology professor has built a new air-powered bazooka that shoots pingpong balls at speeds faster than an F-16 fighter jet, blowing the doors off similar far less powerful devices peers use to explain physics properties.
Mark French drew on his experience as an aeronautical engineer for the U. S. Air Force to create a device that blasts balls clean through plywood or aluminum and deeply dents steel. Online video of the bazooka destroying pingpong paddles, VHS tapes and a series of soda pop cans has generated more than a half million views.
Previous devices propelled balls by popping the seal on a vacuum tube. French had his doctoral students Craig Zehrung and Jim Stratton create a pressure chamber connected to the vacuum tube via a convergent-divergent nozzle.
"That hourglass-shaped nozzle is similar to what is used in fighter jets," French said. "When the pressurized air rushes through the bottleneck it accelerates to supersonic speed as it helps propel the ball through the clear PVC barrel."
French says the supersonic speeds are surprising because the lightweight balls have such poor aerodynamics and high-drag coefficient. At a mere 2.3 grams, the balls deliver a startling amount of energy to targets - the equivalent of a 125 mph fastball or a brick falling several stories.
"There is not enough money you could give me to get me to step in front of that gun," French said.
French uses the gun as an educational device for his students in the College of Technology and as an outreach tool during demonstrations for a wide variety of schoolchildren.