Space Saturday II: If the Unthinkable Happens

With the space shuttle Discovery poised to be launched on Tuesday after a three-day delay because of weather concerns, NASA has revealed a new plan that might allow a last-ditch effort to save it in the event of damage by guiding it back to Earth without its seven astronauts aboard.

The system -- 28-foot braided cable -- could be used if astronauts were forced to abandon the shuttle and take refuge in the International Space Station. The lightweight cable can be attached to control boxes on the shuttle and would allow flight controllers on the ground to activate systems that previously had to be switched on by members of the shuttle crew, including power units, landing gear and drag chutes.

The cable system could offer an alternative to ditching a craft worth at least $2 billion. If the craft had a chance of successful re-entry but officials felt that the risk to crew might be unacceptably high, the cable could be tried in an automated landing at Vandenberg Air Force Base in California so the approach to Earth would occur over water.

In the past, NASA officials have argued that it would be impossible to land the shuttle without astronauts.

The 12-day Discovery mission is mainly dedicated mainly to carrying food, water, spare parts, oxygen and other supplies to the space station, along with a new crew member, Thomas Reiter of Germany, who will be the first astronaut from the European Space Agency to serve on the orbiting laboratory for a long term.

Of far more importance to the future of the space program is the issue of flaws that doomed two previous missions, those of the Challenger in 1986 and the Columbia in 2003.

This is only the second flight since the loss of the Columbia and its crew of seven, caused by a 1.67-pound piece of foam that fell from the shuttle's giant external fuel tank during ascent and punched a lethal hole in its left wing.

NASA spent two years redesigning the tank and developed potential repair methods. But shortly after the Discovery's liftoff in its return-to-flight mission a year ago, several smaller but still hazardous pieces of foam fell from the tank.