A foil-wrapped hot dog was inserted in one end of a long, white pipe.

A button was pushed.

And fwoooomp!  The processed meat rocketed across a gym Saturday afternoon, its trajectory monitored by more than 100 young engineering enthusiasts.

A battle of protein ballistics was underway, hosted at the Sicklerville campus of Camden County Technical Schools.

Junior high students from 20 South Jersey schools, divided into 26 teams, had spent the morning assembling hot dog "launchers" – bazooka-like devices powered with compressed air.  The girls and boys wielded cordless drills, wire strippers, and glue brushes, with guidance from high schoolers and teachers from the technical school.

The "STEM" fields  – science, technology, engineering, and math – are big these days, and hands-on activities such as this are seen as a way to ignite career interest.

The hot dog launchers were designed by Robert Rozzelle, a teacher at the technical school. Each team got a copy of his blueprints, plus an assortment of parts, including PVC pipe,  a 24-volt switch, and an air-pressure valve. They were warned not to set the valve higher than 140 pounds per square inch, or the hot dog projectiles would turn to mush.

The teams stopped for lunch – no hot dogs, but pasta and meatballs – then put their devices to the test.

Though each team used the same plans, there were wide differences in execution.

The key to getting more mustard on your dog? Make sure all fittings are secure and leak-free, said Brendan Hoag, 14, an eighth grader at Resurrection Catholic School in Cherry Hill.

"Seal it so none of the air pressure can get out," he said.

The teams took turns, two at a time, aiming their unwieldy devices at large red-and-white targets at one end of a gym.

The room shook with loud music, punctuated every few minutes with the short, sharp whine of the air compressor. Hot dogs hit the targets, or sometimes the wall, with soft thunks.

Top prize went to Folsom Elementary School, with 200 points. Next came a team from Ann A. Mullen Middle School in Sicklerville, followed by R.W. Kershaw School of Mt. Ephraim and Cooper's Poynt School of Camden.

Audubon Middle School took the safety award, while Haddon Township's Rohrer Middle School earned notice for its engineering documentation.

Rianna Rudica, 14, a teammate of Hoag's at Resurrection, said she had built a small catapult with fellow science enthusiasts at school. But the hot dog launcher gave her new appreciation for the art of propulsion.

"This was definitely a different level," she said.

As for the scientific principle behind the devices, classmate Tyler Tyndale said that part was easy.

"It's an air compressor cannon," Tyndale said. "It's not rocket science."

Kaelin Marshall, 13, a seventh grader at Rohrer, said gluing the sections of pipe together was the easiest part. Stripping the ends of electrical wires was more challenging. Overall, a thumbs-up.

"It exceeded my expectations," she said.