Bad vibrations

Leaks are hard to find because spacecraft are full of life-support systems, computers, controls, gear and research equipment. All those things can hide a leak .Leaks are also hard to find because astronauts can't hear the telltale hiss of escaping air because the hiss is blowing outside the spacecraft and away from searching ears.

So the National Aeronautics and Space Administration (NASA) asked an Iowa State research team led by Dale Chimenti, an Iowa State University professor of aerospace engineering, to develop a sensor that can find leaks by detecting the small vibrations in a spacecraft's skin caused by escaping air. NASA has so far supported the work with $600,000. The Iowa State engineers are working with Invocon of Conroe, Texas, to use their sensor with the company's wireless electronics.

Chimenti's square sensor includes an array of 64 elements that detect vibrations as they radiate along the spacecraft. The different elements pick up vibrations at different times. Those differences can be analysed by a computer to determine the direction of a leak. Add information from multiple sensors, and 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.

Challenges

Chimenti said a major challenge was accounting for a reinforcing grid that rises from the back of a spacecraft's shell and affects the travel of vibrations. He said the researchers solved the puzzle by targeting the frequency range measured by the sensors. They focussed on lower frequencies and that reduces the effects of the reinforcing grid.

The sensor is now with researchers at Invocon, a company that built three kinds of electronic sensors for the June 8 space shuttle mission. One of the sensors was designed to record any impacts to the leading edge of the space shuttle's wing during liftoff.

Kevin Champaigne, a program director for Invocon, said company researchers led by Jonathan Sumners, a senior design engineer, are working to connect the Iowa State sensor with new Invocon electronics. That work will be completed over the next few months.

Chimenti and the company will submit a joint proposal for Phase II funding from NASA's Small Business Technology Transfer Program. If NASA funds that proposal, Iowa State and Invocon researchers would develop a prototype of the leak detection system for NASA.