Records show NASA ordered one of the laser systems as
recently as three years ago.
A 2 1/2-pound chunk of insulation that appeared to
fly off and hit Columbia's heat-protecting tiles is one area of investigation
into why the shuttle broke apart on its descent Feb. 1, killing all seven
astronauts.
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.
Most of the foam is applied at the Michoud Assembly
Facility in New Orleans, and more is applied just before launch at Kennedy Space
Center in Florida.
The spray-on foam ``has a history of debonding,
sometimes striking the orbiter and causing damage,'' according to one report
written in 2001 by Christopher Davis, an engineer at Kennedy Space Center. ``For
this reason, shearography provides an opportunity to evaluate known areas of
concern.''
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, Newman said.
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. (A
nanometer is about 10,000 times narrower than a human hair.)
But even this technology can't detect all possible
problems, Newman said. "We can only see debonds. We can't see where the foam is
weak.''
The devices, which were first introduced in 1987,
start at $100,000. Besides rockets, it has been used in the testing of tires,
orthopedic implants, aircraft engine parts, concrete and even golf balls, he
said.
Records show NASA awarded several contracts to
Norristown, Pa.-based Laser Technology since 1995, including $265,485 in 1995
and $175,600 in 2000 for laser shearograph systems and $42,933 in 1999 for
repairs to the equipment.
In recent years, the flaking problem has become more
common as NASA. Contractors changed the composition of the spray-on foam and
adhesives to comply with health and environmental regulations, said Alfred F.
Daech, a former consultant with Martin Marietta, now part of Lockheed Martin.
Chromium and freon were removed.
Dirt and other foreign substances also can weaken the
insulation, he said.
The problem dates back to the first shuttle launch,
when Daech and others were called to the launch pad because a large bubble
appeared in the external tank insulation. They were able to fix that problem
without delaying the launch.
"Someone had wiped it with a rag. You could see the
swirls," he said. "Improper cleaning was the culprit, usually.''
Then there was always Mother Nature to contend with.
Birds would leave their droppings on the tanks at Michoud. And in 1995, at
Kennedy's launch pad, a pair of woodpeckers drilled nearly 200 holes in the
insulation of Discovery's tank. The spaceship had to be sent back to the hangar
and each hole patched.
Newman said he hopes his company will play a role in
ensuring the safety of future shuttles if in fact wayward foam turns out to be
the cause of the latest disaster.
"It's something I hope makes sure this never happens
again,'' he said.
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