Continuing Search for Cause of Spaceship Disaster

NASA backed away Wednesday from the idea that Columbia was critically damaged shortly after launch by a piece of flying foam from the shuttle`s external fuel tank. Insisting that "there`s got to be another reason," shuttle program manager Ron Dittemore said investigators were using "reverse engineering" to track down the source of rising temperatures in the minutes before Columbia broke up during its re-entry.

NASA conducted an impact test under the wind velocity double the one naturally occurring during the liftoff. But the test results showed that the foam chunk did not damage the shuttle`s body so much as to cause a safety problem. The chunk at issue weights 1.2kg and has a volume of 50×40×15㎝. Dittemore also discounted the possibility that the chunk might have been ice rather than foam: The external fuel tank, which stores the liquid hydrogen and oxygen needed for takeoff, was inspected for icing problems before flight, he said. Thus, the whole search for clues has hit a snag, reported NBC.

Engineers and investigators were looking at a wide array of potential causes for the loss of the shuttle, including even the possibility of a collision with a piece of orbital debris during flight. "It`s remote that it would hit the orbiter," Dittemore said, "but we`ve seen it happen. It`s certainly possible — how likely, I don`t know." Some scientists even suggest that the shuttle ran into a meteor in the space.

An Air Force helicopter flying over Texas also was able to photograph the shuttle in its final minutes, which are under scrutiny. In addition, an Arizona man and his son came forward with a home video that appeared to show a small, bright object falling off Columbia as it passed over Wupatki National Monument near Flagstaff.

The search for clues also includes a review of 32 seconds of computer data gathered just before all communication with Columbia was lost. The telemetry came in flawed, and Dittemore said investigators had not yet extracted any useful information from the data. More than 12,000 recovered remnants, many as small as a nickel, have been found at 3,500 sites, creating a growing mosaic of evidence that could take months or years to pick through. NASA hopes to collect enough debris to reconstruct part of Columbia and establish a sequence of how it broke up. When Challenger blew up in 1986, it took 32 months to find out the cause. A genius scientist, who was also a Nobel Prize winner, finally discovered that a trivial rubber part brought about the disaster.

Ki-Tae Kwon kkt@donga.com