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CAPE CANAVERAL -- If liftoff damage to Columbia's thermal tiles caused the disaster, was the crew doomed from the very start?
Or could NASA have saved all or some of the seven astronauts by trying some Hollywood-style heroics -- a potentially suicidal spacewalk, perhaps, or a rescue mission by another shuttle?
Some of the ideas that have been suggested would have been highly impractical, dangerous and perhaps futile.
The shuttle does not carry spare tiles, and NASA insists there was nothing on board that the crew could have used to repair or replace missing or broken ones. In any case, the space agency believed at the time that the tile damage was nothing to worry about.
Still, as James Oberg, a former shuttle flight controller and author who has been bombarded by Armageddon-type rescue ideas via e-mail, said Sunday: "They may be implausible, but not by much." He added: "There's always the question of miracles."
NASA knew from Day Two of Columbia's 16-day research mission that a piece of the insulating foam on the external fuel tank peeled off just after liftoff and struck the left wing, possibly ripping off some of the tiles that keep the ship from burning up when it re-enters Earth's atmosphere.
A frame-by-frame analysis of launch video and film clearly showed a clump of something streaking away from Columbia 80 seconds into the flight.
Engineers spent days analyzing the situation and concluded that there was no reason for concern. The flight director in charge of Columbia's Jan. 16 launch and Saturday's descent from orbit, Leroy Cain, assured reporters as much on Friday.
But hours after the disaster, shuttle program manager Ron Dittemore acknowledged that NASA might have been wrong and that wing damage on launch day might have contributed to or even caused Columbia to disintegrate on re-entry.
"It's one of the areas we're looking at first, early, to make sure that the investigative team is concentrating on that theory or that set of facts as we are starting to unfold," NASA administrator Sean O'Keefe said Sunday.
Dittemore himself said: "My thoughts are on what we missed, what I missed, to allow this to happen."
Some facts remain:
NASA did not attempt to examine Columbia's left wing with high-powered telescopes on the ground, 180 miles below, or with spy satellites. The last time NASA tried that, to check Discovery's drag-chute compartment during John Glenn's shuttle flight in 1998, the pictures were of little use, Dittemore said. Besides, he said, "there was zero we could have done about it."
Similarly, NASA did not ask the crew of the international space station to use its cameras to examine the wing when the two ships passed within a few hundred miles of each other several times over the past two weeks.
NASA did not consider a spacewalk by the crew to inspect the left wing. The astronauts are not trained or equipped to repair tile damage anywhere on the shuttle, least of all on a relatively inaccessible area like the underside of a wing, Dittemore said.
Could NASA have sent another shuttle to rescue Columbia's five men and two women?
In theory, yes.
Normally, it takes four months to prepare a shuttle for launch. But in a crisis, shuttle managers say they might be able to put together a launch in less than a week if all testing were thrown out the window and a shuttle were already on the pad.
Columbia had enough fuel and supplies to remain in orbit until Wednesday, and the astronauts could have scrimped to stay up another few days beyond that. With shuttle Atlantis ready to be moved to its pad, it theoretically could have been rushed into service, and Columbia's astronauts could have climbed aboard in a series of spacewalks. If Atlantis flew with the minimum crew of two, it could have accommodated seven more astronauts.
Could Columbia's astronauts have abandoned ship and climbed aboard the international space station?
Because Columbia was in an entirely different orbit than the space station, it did not have enough fuel to fly to the orbiting outpost. Even if the shuttle could have limped there, it could not have docked. Columbia was not equipped with a docking ring since it was never meant to go there. So the shuttle astronauts would have had to float over in spacesuits to get there.
Could Columbia's astronauts have gone out on a spacewalk to inspect and perhaps repair their own ship?
That assumes, first of all, that the astronauts could have rigged up something, Apollo 13-style, to replace the missing tiles. But there was nothing on board, according to Dittemore and others. Back in the early shuttle days, NASA considered a tile-patching kit that was essentially a caulking gun, but the gunk undermined the performance of the tiles and never flew.
Two of Columbia's astronauts, Michael Anderson and David Brown, were trained to do a spacewalk, and they had the suits to do it. But neither was trained to do anything more than a relatively simple emergency repair, like freeing a stuck radio antenna or fixing a jammed latch that could cause the ship to burn up during re-entry.
Moreover, a spacewalk to reach the underside of the wings could have been suicidal, because there is nothing to hold on to, and the astronauts did not have mini-jetpacks to propel themselves. The astronauts could have floated off and never gotten back to the shuttle.
Anderson theorized just last summer on how he would go about reaching a trapdoor on the belly of the shuttle that was stuck open, in order to close it. He would have had to rig a 60-foot tether to a weighted bag, lasso it over one of the wings, and then crawl along the line hand over hand to reach the jammed trapdoor.
The chance of all this working, within the eight-to-nine-hour limit of a spacewalk, is practically zero. The spacewalkers probably would not have had enough oxygen to make it back inside.
And Dittemore said Sunday they could easily have worsened the situation. "Just the nature of them trying to position themselves in space underneath the vehicle could cause more damage than what we were trying to fix," he said.
If it was determined that there was no way Columbia and crew could survive a re-entry, and another spacecraft could not reach them in time, they would have been stuck in orbit for a couple of months before being dragged down through the atmosphere in a fireball.
"It would be visible at dawn and dusk and that would be pretty creepy," Oberg said. "But on the other hand, that would be also a memorial. It would be a Viking funeral."