Launch saver

When a crack was discovered in the insulating foam that keeps the shuttle Discovery8217;s external fuel tank from icing over...

When a crack was discovered in the insulating foam that keeps the shuttle Discovery8217;s external fuel tank from icing over, NASA engineers had to decide whether the small piece that broke off before the launch on July 48212;less than four inches long and roughly the weight of a penny8212;was a sign of bigger problems. The engineers needed to examine the place where the foam fell away, to determine whether more and larger pieces could be shed and strike the shuttle orbiter during ascent.

But their view of the damaged spot, on an oxygen feed line bracket, was obscured by other parts of the shuttle, and it could not be seen from the tower standing next to the vehicle. Ordinarily, getting an inspector up close to the bracket would mean setting up a platform and postponing maintenance work while the inspection took place, perhaps delaying the launch by a full day.

About noon last Monday, however, one of the NASA engineers working on the problem checked in with the Micro Inspection Team, a 13-member group that has expertise in getting a good look at inaccessible parts of the shuttle. 8216;8216;They thought we8217;d be able to do what they wanted to do, and it turned out that we did,8217;8217; said Brad Smith, a member of the team.

The tool, known as a borescope, is a kind of camera, a 15-ft-long fibre optic bundle with a lens on the end. It is usually used to examine things like the insides of fuel lines, to see if any tiny scraps of metal or other impurities are there that could be dangerous8212;8216;8216;any areas of the orbiter that you cannot put a eyeball on8217;8217;, said Jeff Rowell, a member of the team. But the 50,000 tool had never been used to look at foam while the shuttle was on the launch pad.

The fibre optic cable cannot support its own weight, so technicians slid the borescope into a bendable 6-ft-long tube that retains its shape. Standing on a platform of the tower, Rowell said, they 8216;8216;had to snake around to the side of the feed line8217;8217; to get a good look. 8216;8216;We were fully extended, plus all of my arm,8217;8217; said Rowell, who had leaned out over a small piece of rope at the edge of the platform 207 ft above the ground, secured only by a safety harness.

8216;8216;The view we gave them was at least as good as you could have gotten with your eye,8217;8217; he said, referring to colleagues who were watching the output images from the borescope. 8216;8216;There was no more foam damage.8217;8217; Images NASA shared with reporters showed minute details on the foam, including inspection stamps. Based in part on those images, NASA officials decided that the launch could go ahead today despite the crack in the foam. 8212; JOHN SCHWARTZ