Sunday, February 1, 2004
The Columbia STS-107 Accident
In honor of seven heroes
Finally, at 395,000 feet altitude and 5,000 miles from touchdown, the shuttle begins to enter the Earth’s atmosphere and decelerate. The high pitch attitude is intended to maximize deceleration while minimizing the heat of re-entry. Still, as Rominger recounted, the temperature outside the spacecraft climbs to about 2,700 degrees F.
Normally, the shuttle’s thousands of ceramic tiles protect the aluminum structure underneath from heat damage. In the case of Columbia, a large section of the left wing’s bottom leading edge had been compromised, allowing the heat of re-entry to burn through the remaining insulation and attack the wing structure. Just as during the deorbit burn, the computers were flying the shuttle in this phase of the approach, guiding the aircraft through a series of S-turns, bleeding off speed on the long, steep glide toward Cape Canaveral. In theory, the computers could have flown the aircraft all the way to touchdown, though they weren’t capable of extending the gear, deploying the drag chute or applying the brakes.
Ironically, the computers may have only served to mask the problem, automatically compensating for the additional drag of the disintegrating wing structure, though there was nothing Commander Rick Husband could have done even if he’d understood the situation. Without power, the shuttle was committed to descend from the moment it dropped out of orbit.
As Columbia crossed the California coast, it was roughly 250,000 feet up, still traveling at 15,000 mph, the point of maximum heating. It was at this location that the first video captured what appeared to be pieces departing the spacecraft. We’ll probably never know the exact sequence of events after that, but by the time Columbia reached Texas, the aircraft had essentially disintegrated, still flying at an estimated Mach 18 and 207,000 feet. In an instant, mission commander Rick Husband, pilot William McCool, payload commander Michael Anderson, mission specialists David Brown, Kalpana Chawla and Laurel Clark, and payload specialist Ilan Ramon were gone.
Just as with Apollo 1 and 13, and the Challenger accident, NASA has gone to school on the problems and hopes to modify the remaining shuttles to minimize future risks. If all goes as planned, NASA will launch an improved shuttle early this year.
Some call the Columbia crew heroes, and if bravery is any definition, they certainly were. I doubt they would have considered themselves as such, however. They were special people doing a special job they loved, and you can bet they felt privileged to be among the chosen few to fly in space. Like the Challenger and Apollo 1 astronauts, the Columbia Seven will never be forgotten.
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