Those Last Few Seconds

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th comes quickly in space, unless it comes very slowly. The crew of the shuttle Challenger is thought — or hoped — to have suffered little. Crew members of Apollo 13, had they not made it home, would have needed days to breathe up all their air and suffocate. Ever since the crack-up of the shuttle Columbia last month, NASA has wanted to know how the astronauts on that doomed ship met their end — believing that the precise sequence of events on the crew decks would reveal a lot about the precise sequence of breakdowns throughout the ship.

Slowly, investigators are piecing together the answers. Space-agency technicians have been scrutinizing the final, fragmentary transmissions that came from the disintegrating Columbia, particularly a telltale, 2-sec. scrap of data deciphered for the first time only last week. Analysts are also paying closer attention to the 13-min. videotape, recovered partly intact from the wreckage, that the crew made during re-entry. Perhaps most important, some former astronauts have been willing to speculate — cautiously — on what might have been taking place inside Columbia in the critical minutes after the video went black and before the ship was destroyed. The sketchy picture that all this paints is of a professional team of astronauts doing everything they could to fly their vehicle, even as events overtook them.

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The videotape, which runs from 8:35 to 8:48 a.m. E.T.--ending about 11 min. before the ship was destroyed — shows the astronauts just where they ought to have been that late in the mission, with commander Rick Husband, pilot William McCool and crew members Laurel Clark and Kalpana Chawla strapped into their seats on the main flight deck. Crewmates Ilan Ramon, David Brown and Michael Anderson were out of view, similarly belted into place on the middeck below. When the tape begins, Chawla and Clark are finishing their suiting up, while Husband and McCool are busy flying the ship.

"Oh, shoot!" Husband says, as he accidentally hits a control that briefly switches the spacecraft from autopilot to manual. "We bumped the stick earlier."

"Not a problem, Rick," Mission Control answers. "Yeah, but ..." Husband grumbles, sounding displeased that the harmless mistake happened at all.

Outside the windows, glowing plasma is flickering like lightning. "Is that [maneuvering] jets firing in the back?" Chawla asks. McCool replies, "That might be some plasma. The jets are not firing now."

The crew members spend the next few minutes enjoying the light show while tending to their suits and instruments and feeling for the return of the first ghost of gravity. When the ship is pulling only one-hundredth of a G, McCool is heard commenting that when he drops a card, it falls, a sure sign that Columbia is crossing the line from extraterrestrial to terrestrial.

Shortly afterward, the video record ends, but things probably remained routine until 3 min. later--8 min. before the accident — when NASA got its first indication of what it dryly calls off-nominal aero increments. Translation: the shuttle was growing unstable because of the loss of insulating tiles, and the computer-controlled flaps were attempting to compensate. Inside the ship this would not have caused concern.

"They probably noticed that the aero surfaces were being trimmed," says former astronaut Norman Thagard, a veteran of five shuttle flights and a tour of duty aboard the Russian space station Mir. "They might have commented that the vehicle was taking some sort of action, but it was still within the ability of the system to stay flying."

Just a few seconds later, however, when Columbia was 300 miles west of California, temperature sensors in the brake lines began to flutter — an anomaly, but a minor one. One minute 27 sec. after that, the first confirmed piece of debris broke away from the shuttle. While this was apparent to observers on the ground, it was not visible to the crew inside the disintegrating ship. "The wing is well behind you," says Thagard.

Less than 2 min. before the end, the problems began to cascade: the instrument panel blinking with a tire-pressure alert, a thruster-leak signal, a roll warning and more. The crew — at least the four astronauts on the flight deck — would have known something was up. "They are seeing multiple failures on top of one another," says former astronaut Tom Henricks, who piloted two shuttle missions and commanded two others. "But they are still thinking they can handle things like they do in the simulator."

Henricks and Thagard agree that whatever the commander and the pilot were doing to right the ship, the rest of the crew probably stayed quiet and let them do it. The astronauts on the flight deck were wired for sound, so anything they said was picked up by their microphones. The three on the middeck had mikes too, but if they wanted to be heard, they had to punch into the ship's intercom. All of them would have kept the chatter to a minimum. "If you're not flying the ship, you keep your mouth shut," says Thagard.