The Columbia Accident Investigation Board also endorsed NASA’s theory about why the orbiter disintegrated over Texas: A hole in the leading edge of its left wing allowed hot gases to eat into the wing’s interior as Columbia re-entered the atmosphere Feb. 1. The seven astronauts aboard were killed in the accident.
Board Chairman Harold Gehman Jr. cautioned that this theory might be changed “at any time in any way without notice.” And he said the board can’t yet prove that the hole in the wing was caused by a 2-pound chunk of insulating foam that broke off Columbia’s fuel tank nearly 82 seconds after liftoff.
“The board is certainly suspicious that the foam had something to do with this,” Gehman said, though it lacks “concrete, irrefutable proof.”
But he added that it doesn’t matter whether investigators never pin the accident on the foam incident. Instead, he said, the board’s report – expected in midsummer – will go well beyond the specifics of the Columbia accident and touch on issues as far ranging as the aging of the shuttle fleet and the National Aeronautics and Space Administration’s decision-making process.
“We’re looking at this program in a very, very broad way,” said Gehman, a retired Navy admiral, “and therefore we’re going to come up with a broad range of recommendations which will make the program safer.”
He later added that the board hopes to set the stage for a national discussion on the risks of human space flight.
“We will attempt to characterize the risk in our own terms,” Gehman said. “That will be one of our goals, to restate the risk in terms that there can be a good public policy debate on whether we should be doing this or not.”
During a regular weekly news briefing in Houston, board members said adopting a “working hypothesis” for what caused the disaster allows them to tightly focus their efforts as the investigation winds down, and they prepare to move to Washington next month to write the report.
Gehman said the board’s recommendations will encompass four areas:
While board members continue to sort out what happened behind the scenes while Columbia was in space, they did endorse a basic technical description of what happened to the wing during re-entry.
The scenario was described to the board last week by NASA, after the Orlando Sentinel reported last month that it had been completed by agency engineers.
Gehman said his investigators are in complete agreement with NASA on the basic facts: A large chunk of foam peeled off the so-called “bipod” area of the shuttle’s external tank 81.7 seconds into launch and slammed into the edge of the wing.
The best analysis indicates that it struck near two of the 22 insulating carbon panels that cover the wing’s edge. The panels are numbered 1 to 22, and investigators think the foam hit in the area of panels 7 and 8.
On Columbia’s second day in orbit, a piece of the left wing came off after the shuttle executed a routine maneuver. The mystery object is probably a piece from carbon panel 8 or panel 9 or a piece of the seal between them.
This missing segment allowed hot gases to begin penetrating the wing as the shuttle dropped below 400,000 feet above Earth. The heat quickly burned through the wing’s aluminum spar and progressively destroyed inside components and electrical wiring. The shuttle shed debris steadily as it flew from California to Texas and finally disintegrated 18 miles above central Texas.
