An MIT professor speculated that the space shuttle Columbia broke apart upon re-entry because of a malfunction of the vehicle's flight control system--which, like on an airplane, automatically positions its wings and rudder--or a problem with the tiles that coat the shuttle.
David W. Miller, associate professor of aeronatics and astronautics and director of the Space Systems Laboratory at MIT, said today, "My guess is that it is one of two things: a problem with the flight control system or a problem with the thermal tiles" that protect the shuttle from the massive heat of re-entry into the Earth's atmosphere.
Although Miller said there are "a myriad of other possibilities and we don't have any data," he said that based on where and when the shuttle appeared to break apart, the shuttle appeared to be on course, so that would rule out other complications. "There's always a chance (for hope that the astronauts survived), but I think what you see is what really happened--catastrophic failure of the vehicle," he said.
The space shuttle prepares for landing by firing its orbital manuevering system rockets to slow down enough to drop out of orbit. It is virtually on automatic pilot at that point, with computers automatically taking a reading of on-board sensors and determining how to run the control surfaces of the vehicle.
The control surfaces, like those on a commercial airplane, take on different configurations of the tail and wings to move the belly of the shuttle forward and start to position it, still half a world away, to land at Kennedy Space Center. "They want to come into the atmosphere at a specific location, speed and angle to the horizon," Miller said. "The shuttle was on its expected trajectory--people looked for it from the ground and there it was."
"It could have tumbled because its control surfaces were not operating correctly, or it was flying fine and the thermal tiles sustained damage when they started absorbing heat. The vehicle at that point is very hot in the atmosphere. There are extremely hot gases--the atmosphere gets superheated around the shuttle, and if the heat reaches the aluminum under the tiles, there could be a blowtorch effect," he said.
The space shuttles undergo an extensive refurbishment program. Even though Columbia is the oldest shuttle in the fleet, Miller said it had probably been refurbished at least once. In addition, after every flight, the shuttle's heat-protecting tiles undergo a meticulous inspection where worn or damages tiles--and their neighbors--are replaced. Neverthleless, Miller points out, the tiles are delicate and "there are many, many tiles."
"It just reminds me of when I was a graduate student at MIT and heard about the Challenger accident," Miller said. "At first you don't believe it--you're just sort of stunned. You don't know what to feel."