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Investigators focus on shuttle's overhaul
By Anne Barnard and Gareth Cook, Globe Staff, 2/5/2003
The space agency is reviewing the overhaul, both to determine whether something could have gone wrong when many of the shuttle's protective tiles, wiring, and other systems were taken apart and rebuilt, and to learn from the most comprehensive recent view of the shuttle's condition, according to a NASA official with knowledge of the investigation. Since Columbia disintegrated in the upper atmosphere Saturday, killing seven astronauts, much of the scrutiny has focused on damage the shuttle may have sustained on liftoff from a hardened piece of insulation that broke off an external fuel tank and hit tiles on the underside of the left wing. The tiles protect the vessel from the extreme heat of reentry.
NASA associate administrator Michael Kostelnik said yesterday that the insulation chunk, estimated at 2.67 pounds and 20 inches long, ''probably is the largest piece'' ever to slam into a shuttle on liftoff. But the agency is also looking for a possible ''missing link,'' another problem that could have contributed to the accident, perhaps in conjunction with tile damage. Also yesterday, researchers said they had warned NASA nine years ago that the shuttle could fail catastrophically if debris hit the vulnerable underside of its wings during liftoff. After receiving the warning, NASA made changes in materials and flight rules to lessen the risk of debris breaking loose, said Paul Fischbeck, an engineering professor at Carnegie Mellon University who conducted the 1994 analysis. Fischbeck and a colleague at Stanford University, Elisabeth Pat-Cornell, studied the damage caused by debris during the first 50 shuttle launches and concluded that on average, 25 thermal tiles per flight sustained damage of at least one inch. A spokesman at NASA's Johnson Space Center, David Drachlis, said last night that no one was available to comment on the report. Insulation chunks have fallen off and hit the shuttle during numerous launches, according to NASA reports, including one in 1997 in which 388 tiles were missing on the Columbia after one particularly battering flight. The official involved in the current investigation said he initially worried that NASA had gotten ''overconfident'' that foam chunks falling off the tank were not dangerous. But he said he now believes it's more likely that several problems, none fatal by themselves, combined to cause the disaster. Outside specialists, however, continued to argue that the chunk of insulation by itself could have caused damage that worsened with aerodynamic pressure on both liftoff and descent, leading to the disaster. NASA could not have ruled out the possibility the brick-like, hardened foam insulation that struck the wing was the ''magic BB'' that brought down the craft, said John Handsman, professor of aeronautics and astronautics at Massachusetts Institute of Technology. ''There are so many variables: the exact attitude at which it hit, whether it dug in and flipped, whether it hit on the seam between two tiles or in the middle of a tile,'' he said. NASA's initial analysis, based on past experience, found that the risk of danger from the damage was insignificant, but now, he said, analysts will use new mathematical models based on the assumption that the damage was fatal. Handsman said the overhaul begun in 1999 could provide important information about which areas of tile were old and which were relatively new. Repair records would also show the history of the glue attaching them to the shuttle structure, and where areas of corrosion under the tiles were found and repaired. Handsman said that while the overhaul was meant to make Columbia safer, there is a small chance it could have caused structural problems. ''Any time you start opening an airplane up you do introduce the possibility that you break something while opening and closing it,'' he added. ''That's always a kind of trade-off.'' The overhaul was conducted at a Boeing facility in Palmdale, Calif., and at the Kennedy Space Center in Cape Canaveral, Fla., where workers inspected the shuttle's electrical system to correct a problem from the previous launch, scoured its surface replacing tiles and looking for corrosion, and removed 1,000 pounds of outdated and unnecessary wiring, to lighten the shuttle and allow it to reach the International Space Station. A spokeswoman for United Space Alliance, the Lockheed Martin-Boeing joint venture that is NASA's largest contractor, said the company had turned over information about the overhaul to NASA, but did not know what aspect of the overhaul might be most interesting to investigators. Investigators will be particularly interested in the bond between tiles and the aluminum body of the craft. If a tile failed, and started to heat the aluminum body underneath, it would heat the bonds of other nearby tiles, possibly causing them to fail, said Subra Suresh, the head of the department of materials science at MIT. NASA officials yesterday said several debris sites had been cordoned off. Pieces of the fuselage, a circuit board, and landing gear from the Columbia were found in East Texas yesterday, authorities said. NASA's Kostelnik also revealed a new, unexpected source of data: An Army Apache helicopter aloft over Texas caught the Columbia's fiery streak downward on high-powered video cameras. For years, Columbia has suffered more tile damage from falling insulation than some other shuttles have. In a 1997 report, a NASA mechanical system engineer noted that during Columbia's takeoffs, dislodged insulation ''becomes a projectile with incredible damage potential.'' Gregory N. Katnik, in an unofficial report for a NASA public relations website, said he noticed light spots of ''significant'' damage on the shuttle as it landed in 1997. Forty damaged tiles are considered normal by shuttle standards, he noted, but post-flight examination found 388 hits to the Columbia. More than 100 tiles had nicks greater than 1 inch in length, with some measuring up to 15 inches in length and 1 1/2 inches in depth. The tiles, Katnik noted, are only 2 inches deep, and 100 tiles on that 1997 flight were damaged beyond repair. Katnik speculated that a sub-par insulation foam may have been used to insulate the shuttle's external tank. NASA, on that flight, had shifted to an ''environmentally friendly'' foam that did not contain freon. Raja Mishra of the Globe staff contributed to this report. Anne Barnard can be reached at abarnard@globe.com; Gareth Cook is at cook@globe.com.
This story ran on page A1 of the Boston Globe on 2/5/2003.
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ASA specialists investigating the Columbia disaster are taking a close look at a major, nine-month overhaul that the space shuttle underwent in 1999 and 2000, before its second-to-last mission, officials at NASA and its largest contractor said yesterday.
