Investigators now have the strongest evidence yet that the space shuttle Columbia's left wing was critically punctured during liftoff, when falling debris started the fatal chain of events that led to the breakup of the shuttle when it re-entered Earth's atmosphere, ABCNEWS has learned.
The evidence comes from an old magnetic tape recorder that is part of the Orbiter Experiment Support System, sources said.
It shows an unusual temperature increase in a key sensor just behind the leading edge of the left wing near the spot where foam that fell from the shuttle's external fuel tank is suspected of striking the shuttle, just 81 seconds into the flight.
The temperature spike happens within the next 40 seconds. Usually during this phase of flight, the temperature would be decreasing or holding steady, sources said.
"All the evidence is pointing there," a knowledgeable source told ABCNEWS. "It's kind of like the lady in California. Everybody knows it's her, but they just can't officially say it yet."
The data comes from a temperature sensor behind the front spar of the left wing near a shuttle's protective thermal panels known as reinforced carbon carbon panels, or RCC. These panels are supposed to protect the shuttle from the heat of re-entry.
Investigators say it was a breach in the left wing near the leading edge that led to the breakup of Columbia on Feb. 1 when it plunged back into the Earth's atmosphere at more than 20,000 mph. All seven astronauts on board perished.
The Columbia Accident Investigation Board is still trying to piece together the puzzle of the shuttle disaster — but they have already recommended that NASA do a much better job of inspecting RCC panels for any weaknesses prior to liftoff.
The board is concerned that as the shuttle fleet ages, the RCC panels may be more susceptible to failure — and that Columbia's age may have been a factor in the shuttle accident. Columbia flew its first mission in 1981, making it the oldest shuttle in the fleet.
The board will hear from more experts at another public hearing next week. Members will start to write their report at the end of May and hope to issue it sometime in June.
None of the information from the recorder could have helped save the doomed shuttle. It was not available to ground control at launch, and controllers would not have noticed the spike until the shuttle landed and, weeks later, analyzed the data.
And even if they had known, it is open to debate what could have been done.
"If they suspected the damage, could they have done something? Probably not," a source said. "But you never want to say there was nothing that could have been done, because you never know what 1,000 people all working on one problem might come up with."