Sean O'Keefe said that tests by the Columbia Accident Investigation Board suggest the space shuttle broke apart because of a hairline crack, less than an inch long, in the reinforced carbon panels covering the left wing. The crack is thought to have been created 81 seconds after launch when insulation foam peeled from a fuel tank and smashed the wing.
"You've got to put your face two to three inches away to see the crack," O'Keefe said.
Because such slight damage was enough to cause the loss of Columbia and its seven astronauts, NASA engineers face "an extreme challenge" as they develop plans for returning the shuttles to space, he said.
"We've got to create an inspection regime for future flights that will be extremely meticulous," O'Keefe said.
He said plans could include installing special foot and hand restraints on the outside of the shuttle that would allow space-walking astronauts to closely inspect the spacecraft's underside. The plans also could also include some sort of kit that would enable spacewalkers to repair damage to the craft's heat shield, he said.
O'Keefe said that when space shuttle flights resume, launches will be limited to daylight hours. This will allow cameras at the Kennedy Space Center to take high-resolution photos of the craft during its ascent to orbit. During Columbia's January launch, some cameras failed to capture high-quality views of the speeding craft. Although there were pictures of the foam insulation hitting the wing, their quality was too poor for engineers to immediately calculate the extent of the damage.
An analysis made during the flight concluded that any damage to the wing would not risk spacecraft safety. As a result, engineers did not formally request that spy satellites be used to take photographs of the potentially damaged wing or take any other actions that might have given Columbia a better chance of surviving re-entry.
O'Keefe declined to discuss whether such photos from spy satellites might have been able to detect the small crack in the wing.
"I'll let you draw your own conclusion," he said. The administrator announced earlier that future space shuttles would routinely be photographed in orbit by the satellite equipment operated by another federal agency.
O'Keefe also said that all but one of the anticipated future shuttle flights will go to the international space station. The station would provide a refuge for the astronauts and a platform to closely inspect any suspected damage. The sole exception, he said, is a late 2004 flight planned to maintain the Hubble Space Telescope. Shuttles that fly to the Hubble cannot also fly to the space station.
The Columbia Accident Investigation Board conducted the heat shield tests recently in San Antonio. The tests involved firing a 2.6-pound piece of insulation foam at a mock space shuttle wing at about 525 miles an hour, mimicking the effects of the foam hit during Columbia's launch. The test showed that the impact was enough to slightly open seams between the heat shield panels and cause small cracks. The theory is that this may have been enough to allow the superheated gas during re-entry to enter the hollow wing and melt it from within.
The board is expected to issue a final report late next month.
O'Keefe said his agency will "comply fully without any equivocation" to the board's recommendations. To ensure this compliance, he is naming a return to flight oversight board that will include three former astronauts along with a group of engineering safety experts, he said.
Columbia came apart over during its return to Earth on Feb. 1, killing the seven astronauts on board and scattering debris over parts of Texas and Louisiana. The three remaining space shuttles were grounded. O'Keefe said he was sticking by an earlier prediction that the shuttles will start flying again in December or early in 2004.
By Paul Recer