Objects just a few millimeters across could pierce the thin aluminum skin of spacecraft such as the International Space Station orbiting 220 miles above Earth. And even a tiny hole can mean a leak of pressurized air. Dale Chimenti, an Iowa State University professor of aerospace engineering, is leading a team that has been contracted by NASA to find and fix these tiny leaks in spacecraft.

Leaks are hard to find because spacecraft are full of life-support systems, computers, controls, gear, and research equipment, all of which can hide a leak. Also, astronauts can't hear the telltale hiss of escaping air. A spacecraft can only produce so much oxygen, so astronauts must be able to find a leak as quickly as possible. The Iowa State team developed a sensor that can find leaks by detecting the small vibrations in a spacecraft's skin caused by escaping air.

The square sensor measures an inch across and includes an array of 64 elements that detect vibrations as they radiate along the spacecraft. The different elements pick up the vibrations at different times, and those differences can be analyzed by a computer to determine the direction of the leak. With information from multiple sensors, a leak can be found in about a minute -- it can take weeks to find a leak with NASA's current handheld ultrasonic detection devices.

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