Laser Shearography Might Have Found Shuttle Flaw

NORRISTOWN, Pa., Feb. 21 -- Laser Technology Inc. said its laser shearography process might have detected defects in the foam used on the Columbia Space Shuttle, had NASA used it, according to an Associated Press (AP) article published today.

"After years of concern about foam insulation breaking off and damaging space shuttle thermal tiles, NASA started evaluating -- but not widely using -- a technology that could detect subtle defects in the foam," the article said.

NASA didn't comment on the new technology except to say that any new process used on the shuttle requires lengthy testing before being implemented. Records show NASA ordered one of the laser systems as recently as three years ago, said the AP.

According to the article, "Laser shearography promised to address a concern since the earliest days of the shuttle program -- insulation peeling off and striking the tiles. Recent changes in the composition of the spray-on foam and adhesives have made it more susceptible to flaking off, experts said."

Laser shearography involves vibrating the material very slightly. A laser is beamed on the surface and a digital camera records differences in the surface of the material. In the case of foam insulation, the technology is useful in finding areas where it has "disbonded" from the aluminum-lithium skin of the massive external fuel tanks, John Newman, Laser Technology's CEO, told the AP.

The system can scan an area of about 32-by-36-inches every half-second, meaning the entire tank could have been tested in about 24 hours, Newman said. It can detect deformation as small as 20 nanometers. But even this technology can't detect all possible problems, Newman was quoted: "We can only see debonds. We can't see where the foam is weak."

For more information, visit: www.laserndt.com