In a classroom at Colorado College’s Barnes Science Center on Thursday, several CC students and a small group of observers from the National Society of Professional Engineers watched as the air pressure built inside a contraption that, if successful, would launch a near-weightless object faster than the speed of sound.

There was no countdown, because the actual moment of the launch could not be known. The students and observers watched and waited, not wanting to miss the moment when …

POP!

The contraption made a noise like a giant party balloon as the object was fired. It happened too quickly to be seen with the naked eye. There was simply the loud noise and, as if by magic, a hole appeared in the nearby target: a ping-pong paddle.

One student checked the speed of the launch as the others waited anxiously.

“Three-hundred-fifty-one meters per second!” said physics student Max Pfeiffenberger.

“We broke Mach 1!” the students exclaimed, partly in triumph, partly in relief.

The speed of sound is 343 meters per second, or about 761 mph. The students had just broken the sound barrier — with a ping-pong ball.

“This has been a true engineering project,” said Kristine Lang, chair of CC’s physics department. “I tell students all the time that real learning comes from failure, from falling down and getting back up again.”

ABOVE: Thursday’s successful launch propelled the ping-pong ball through a paddle — and broke the sound barrier.

photos by O’Dell Isaac, The Gazette

The course, Investigations in Engineering, is a two-week, project-based course taught by a visiting engineer to introduce students to a different aspects of the field. Colorado College does not offer an engineering degree, so the 27 students came from various fields of study to build a device that could launch — at supersonic speed — an object that weighs less than 3 grams.

“We chose a ping-pong ball launcher because we thought the project would give the students a real idea of what engineering is all about,” said Tom Edwards, the veteran engineer who taught the course. “The project involved aspects of mechanical engineering design, there was some rocket science in the designing nozzle, and electrical engineering in measuring the speed of the ball.”

Because the course is only two weeks long, there isn’t much time to study theory. The 27 students were divided into nine teams, each with its own specific function, and got to work right away.

“Every team has its own piece of the puzzle to work on,” Edwards said. “Each day, we’d have a morning meeting, and we’d get a project update from each team, we’d collaborate, share some ideas, and get back to work.”

The device was composed of two large tubes, fitted together by a pair of flange fittings. One tube was connected to a large air compressor, which would supply air pressure of up to 150 pounds per square inch. The other tube was a vacuum.

In the middle of the device, between the flange fittings, was a polycarbonate membrane that was 0.015-inch thick. When activated, the buildup of air pressure would burst the membrane, allowing air to rush into the vacuum, creating the thrust that would propel the ping-pong ball at supersonic speed.

At least, in theory.

“A ping-pong ball weighs next to nothing,” said Max Dunham, a business and art student who served as project manager. “It’s a lot easier to make a heavier thing go fast, which is why bullets are made of lead and not plastic.”

One of the more frustrating challenges was finding the right material for the membrane, students said. Some materials would crack too soon. Others would wrinkle. Each defect had a negative effect on the air pressure.

“We tried aluminum foil, we tried rubber,” said Sonia Gutierrez. “At one point, we tried using pie plates.”

The group learned something from each launch attempt, but the trial-and-error process produced its share of frustrating moments.

LEFT: An earlier launch attempt didn’t reach subsonic speed, but did manage to launch a ping-pong ball at about 400 mph.

O’Dell Isaac, The Gazette

“A lot of us are used to things working right away, from the get-go, and this definitely did not,” Dunham said.

“It’s probably not that complicated for students with an engineering background. If you had put a bunch of juniors from, say, MIT on this project, they probably would have figured it out a week ago. “

Edwards, whose day job is director of support and operations at Scientific Applications and Research Associates in Colorado Springs, said the students’ lack of engineering experience is part of what drew him to the course.

“This is a good way for these students to cut their teeth on some engineering design work, learn how to observe safety procedures … and how not to blow stuff up,” he said.

One of the most important things the students learned, they agreed, was patience.

“There were a lot of times when we thought there was no chance of it working,” Pfeiffenberger said. “But we kept at it.”

“It got pretty frustrating sometimes,” Gutierrez agreed. “But that’s part of the course — trying, and failing, and trying again.”

Even after the course was officially over, several students returned to the classroom during their free time, making calculations and adjustments, then recalculating and readjusting, as they tried to get it right. One student grabbed a ratchet wrench and tightened the fittings just minutes before the demonstration was set to begin.

Because of the weightlessness of the ball, it cannot travel far. Even with all that air propelling it, the ping-pong paddle was placed less than a foot from the barrel of the launcher. When the ball was fired, it made a nearly perfect round hole in the paddle. The ball was obliterated.

“There’s a piece here,” Edwards said, scanning the floor. “Oh, and there’s a little piece over here …”

When Pfeiffenberger announced that the launcher had broken the sound barrier, the observers were impressed, and the team members were relieved. Lang, who oversees the course, was all smiles.

“You try something, and if it doesn’t work, you figure out what went wrong, make adjustments, and try again,” Lang said. “That’s engineering. That’s science.”