February 18, 2003
SPACE CENTER, Houston -- As the days become weeks since Columbia's disintegration over Texas, fewer and fewer pieces of space shuttle wreckage are turning up, even though the calls keep coming in.
On Monday, NASA asked farmers and ranchers out West to be on the lookout during spring plowing for anything that might have fallen from the sky on Feb. 1. The plea came as a reported 1,300 state and federal personnel took part in search and recovery efforts in Texas and Louisiana.
"It's kind of a mixed thing. There's a tremendous amount of information available already, even though not everything directly points to a particular thing," said NASA's Steve Nesbitt, who is serving as the spokesman for the accident investigation board.
Nine of the 10 board members met Monday at their new headquarters in an office building just a mile from Johnson Space Center and planned to hold a news conference, their second, today. The 10th member, newly selected Sheila Widnall, a former secretary of the Air Force, will join the group later in the week.
So far, the investigation board has publicly put forward just one hypothesis: that a breach in the left wing likely allowed superheated gases to penetrate the spacecraft.
Paul Fischbeck, a Carnegie Mellon University engineering professor, said that hypothesis makes his own analysis "more and more likely." In a 1990 study and followup research, Fischbeck concluded that a space shuttle could fail catastrophically if during liftoff debris hit the vulnerable underside of its wings, near the landing-gear wheel wells.
Barely a minute into Columbia's flight on Jan. 16, a chunk of insulating foam broke off the external fuel tank and slammed into the bottom of the left wing.
The breach in Columbia could have been caused by a meteor or space debris, or the landing gear compartment door could have been blown open during atmospheric re-entry, Fischbeck said Monday. But the most likely scenario by far, he said, is that the foam damaged or knocked off thermal tiles, more tiles gave way during re-entry and those missing tiles led to a burn-through of the aluminum hull.