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Initial inquiry focuses on wing Loss of insulation raised as a theory By Gareth Cook and Matthew Brellis, Globe Staff, 2/2/2003
As it streaks through the atmosphere, the shuttle is protected against temperatures of up to 3,000 degrees Fahrenheit by a thin layer of ceramic tiles. There are hints that some of these tiles may have failed, leaving the wing exposed to the extreme heat and eventually tearing the craft to pieces. When Columbia was launched on Jan. 16, cameras recorded what appeared to be a piece of insulating foam falling from the external tank and apparently striking the left wing. Then yesterday, in the minutes before controllers lost contact with the shuttle at around 9 a.m., they received a cascade of warnings from pressure and temperature sensors that something had gone awry in the left wing. ''All indications were in the left wing, so we cannot discount that there is a connection,'' Ron Dittemore, the shuttle program manager, said at an afternoon press conference. ''But we cannot have a rush to judgment.'' Prior to the accident yesterday, NASA had said the launch incident was minor, and was not a threat to the mission.
A massive investigation began less than an hour after the first sign of trouble and, by the end of the day, had turned broad parts of the nation into the equivalent of a crime scene. NASA officials ordered operations at several NASA centers and contractors' facilities to stop, to preserve potential evidence. They also impounded records, from flight data to preflight reports. And local law enforcement officials in Texas and Louisiana scrambled to protect wreckage that might hold clues. They also called on the public to help by calling in reports of wreckage and supplying any pictures or video they had of the craft breaking up over Texas. NASA administrator Sean O'Keefe said yesterday that two groups will investigate the accident, an internal NASA group, and an independent board, including top officials from the military and other federal agencies. Scientists said that while early attention was focusing on the left wing, many factors could have caused the accident. During reentry, the shuttle is a vulnerable craft, and it must fight off an onslaught of heat that would have been at its maximum at the time of the accident. At this time, little problems can quickly escalate. Based on videotapes showing many pieces streaking through the sky, and based on the suddenness of the accident, it is clear that the shuttle experienced what engineers call a catastrophic structural failure. Investigators face a broad array of possible explanations for that failure. If enough tiles were affected, heat could have torn the shuttle apart. It is also possible that there was an explosion on board, caused by overheating or something else. It is also possible the Columbia, the oldest vessel in the shuttle fleet, had been mechanically weakened by years of service. And it may be that the craft lost control, perhaps because of a computer glitch or another failure, which itself my have been caused by overheating or by some other problem. During liftoffs, it is common for pieces of ice or insulation to fly off the craft, so the idea of an insulation loss could be a red herring, some analysts said. On a day like this, observers seem to gravitate to the most recent available fragment of information, said Ed Crawley, chairman of the Massachusetts Institute of Technology's Department of Aeronautics and Astronautics. Crawley and others did say, though, that terrorism was unlikely to have been the cause. Investigators will look at the possibility, but shuttle security has been especially tight since the Sept. 11 attacks. And because the accident occurred at 207,135 feet, it was well beyond the reach of a ground-based attack. Weather was also viewed as unlikely to have been a factor, because the craft was so high. At a press conference yesterday, NASA officials described the warnings that made the left wing an early focus of the investigation. The first indication of trouble was received at 8:53 a.m. when there was a loss of temperature sensors in the hydraulic systems of the wing, said Dittemore, the program manager. This was followed seconds and minutes later by the loss of tire pressure readings in the left main-gear wheel well, Dittemore said. At 8:58, NASA officials said, temperature sensors embedded in the shuttle stopped giving readings. At 8:59, the left inboard and left outboard tire temperatures and pressure monitors stopped sending signals. Sensors commonly fail if a box that conveys the signals malfunctions, but controllers knew there was a problem because so many sensors from different systems were failing, Dittemore said. The problems appear to have started at the back of the wing, he said, and to have worked their way forward as the shuttle was in the process of rolling to slow its speed, about 18 times the speed of sound, and performing a banking roll with the wings at a 57-degree angle. A ground controller was asking the crew about the problem when communication abruptly was lost. Video played on television throughout the day showed what appeared to be a large piece breaking off, then the shuttle breaking into many pieces. The durability of the tiles was an early concern in the shuttle program, with numerous delays as engineers figured out how to fasten them to the surface without breaking them. As the flights became more regular, though, that concern abated. After the problem at the launch, NASA issued a statement saying that the insulation that had been seen falling off the shuttle was not a safety concern. This mission did not have the robot arm, so there was no easy way to inspect the tiles, and there would have been no way to repair them, Dittemore said. Investigators will look at the debris pattern, videos, and radar and may determine reasonably precisely when it happened from the telemetry, said R. John Hansman, professor of aeronautics and astronautics at MIT. Hansman also said investigators would make use of NASA simulators and run flight controls to try to learn more. ''People forget that the shuttle is always flying at the edge of the envelope,'' Hansman said. ''They think of it as a commercial airplane. They think of it as a normal thing, and it is not. It is an old airplane, with old flight control systems, the best of 1970s technology.'' Critics of the shuttle program have said that funding cuts have been cutting away at the margin of saftety. Six NASA scientists were dismissed in March 2001 after issuing such warnings for years. The investigation will also have a political component. The independent inquiry, similar to one conducted after the Challenger disaster of 1986, is intended to give the public some confidence that the problems have been found. And, if the shuttle program is not over, that problems have been fixed. Wire services were used in this report. Gareth Cook can be reached at cook@globe.com.
This story ran on page A17 of the Boston Globe on 2/2/2003.
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ithin hours of the shuttle disaster yesterday, investigators focus ed on the possibility that damage to the left wing on takeoff may have led to the disaster.
