Guarding against foam flaws

The engineers who built the massive external fuel tank that will power the shuttle Discovery into orbit this spring used sophisticated X-ray detectors developed by University of Florida (UF) researchers to reduce the chance of a defect in the foam insulation covering the tank.

The detectors, first invented as a new technology to find land mines, can identify tiny gaps, or air-filled voids, in the insulating foam without causing any damage. It is believed that such a gap – possibly located between the foam and the tank’s surface – caused a suitcase-sized piece of foam to break off during Columbia’s liftoff in January 2003. The chunk struck the edge of the shuttle’s left wing, seriously damaging it and spurring the shuttle’s destruction during re-entry on February 1.

“We can do the inspection of the foam as it exists already sprayed onto the tank. We don’t have to cut into it,” said Warren Ussery, team leader for the return to flight nondestructive evaluation team at Lockheed Martin’s Michoud Assembly Facility in New Orleans, where the shuttle’s external tanks are manufactured. “We’re able to find critical voids with that (the UF detector).”