Columbia was spattered by molten metal
By Alan Levin
USA TODAY
HOUSTON -- A hole in Columbia's left wing allowed so much heat to enter the shuttle, a cloud of molten metal enveloped it as it broke apart, the board investigating the accident said Tuesday.
Numerous heat-resistant tiles recovered across Texas and Louisiana are coated with aluminum residue, apparently the remnant of the shuttle's left wing frame. Pieces of hard carbon that made up the front of the left wing were spattered with molten stainless steel.
The latest report from the Columbia Accident Investigation Board provided more detail on the violence of the shuttle's sudden end Feb. 1. But the board said the growing pile of evidence still does not explain why hot gases penetrated the shuttle's left wing.
''The wing was being eaten from the inside out,'' board member Roger Tetrault said.
The two left landing gear tires, for example, are severely torn and burned, Tetrault said. By comparison, the tires from the right side suffered more moderate damage similar to that expected in a plane crash.
The black, soot-like coating on the tiles is more prevalent on tiles from the left side. But the final moments were so severe that the overheated aluminum also hit tiles on the opposite side of the shuttle.
''You had molten aluminum being sprayed or depositing onto those tiles on the right side where the event does not occur. That's a very hot re-entry,'' Tetrault said. The aluminum coating has never been seen before, he said.
So far, the investigation has raised far more questions than it has answered, board members said. Analysts have so far been unable to pinpoint the origin of the hole in Columbia's left wing. The half-dozen separate investigative efforts are making progress, but ''right now, they don't fit together,'' accident board chairman Harold Gehman said.
Tetrault said he is particularly puzzled by why pieces of the inside of the wing's leading edge were sprayed with melted stainless steel. The stainless steel used to hold that part of the wing together melts at about 2,500 degrees Fahrenheit.
Similarly, investigators cannot explain why a piece of the left wing that adjoined the wheel well shows signs that a stream of hot gas had spewed out of the wing.
Very little of the left wing's basic structure has been recovered, offering further evidence that it may have been vaporized by the superheated gases of re-entry. No wreckage from the left wheel well door has been identified.
Gehman also said he will call NASA's shuttle program manager Ron Dittemore along with other officials to testify at an accident board hearing Thursday. Dittemore and another NASA official will describe the history of the shuttle program but will not discuss the investigation. Another witness will describe the foam applied to the shuttle's external fuel tank. A piece of the foam may have struck the underside of Columbia's left wing shortly after launch.
