Bread and salt were waiting for commander Eileen Collins and her crew when they docked the space shuttle Discovery with the International Space Station last Thursday. Station commander Sergei Krikalev had prepared the little ceremony, a Russian tradition intended to bring good luck to a visitor to your home. After the shuttle's stunning lift-off two days earlier--the first since the loss of the Columbia orbiter in 2003--it didn't seem the crew would need such happy charms. But now it appears the shuttle program as a whole--if not the astronauts themselves--may need a lot of luck indeed.
Only hours before the docking, NASA announced that the entire shuttle fleet was being grounded again, after evidence that four pieces of insulating foam--the largest the size of a skateboard--had spun off the ship's external fuel tank during lift-off, just the kind of debris that damaged Columbia's wing and doomed the ship. Only one small piece may have struck the shuttle this time, glancing off a wing with so little force it didn't register on impact sensors. But a camera mounted on the shuttle's 50-ft. arm as well as photos taken from the station have detected at least 25 dings in Discovery's insulating tiles. The most worrisome: a 1.5-in. divot near the nose, where temperatures can reach 3000°F.
So far, NASA insists that none of the chips present a danger, but in the days leading up to Discovery's planned Aug. 7 return, engineers--to say nothing of the astronauts' families--will be anxiously watching for any change in that assessment. If the shuttle were deemed unsafe to fly, the crew could take refuge in the space station, waiting out the five weeks it would take to roll out and gas up sister ship Atlantis for a rescue mission. But Wayne Hale, deputy shuttle manager, dismisses that scenario as "remote."
The larger question may not be the fate of Discovery but that of the whole fleet. After 2 ½ years and $1 billion spent on safety upgrades designed to prevent just such a setback, how could things go so wrong again? Can a program that has already claimed the lives of 14 astronauts ever be safe? And what does any of that say about the Bush Administration's dream of sending crews to the moon and Mars?
No one knows why the foam flaked off in such large chunks. Since 2003, engineers have improved the way it's applied and contoured, and they eliminated it altogether in some tricky spots. That was supposed to ensure that no debris heavier than 0.03 lb. broke free. Cameras aboard Discovery suggest that the biggest chunk this time weighed just under a pound--nearly 30 times the limit. "The cameras worked well," said NASA chief Michael Griffin. "The foam did not."
Most of the debris came from a nettlesome area of the tank known as the protuberance air load (PAL) ramp, a ridge designed to minimize turbulence around cables and fuel lines. Tests and earlier flights convinced NASA that the PAL could withstand lift-off. "Obviously," says flight operations manager John Shannon, "we were wrong."