CAPE CANAVERAL, Florida (Reuters) - U.S. and Russian flight controllers worked to fully restore computers aboard the International Space Station on Thursday after a system crash that could force the $100 billion outpost's crew back to Earth.
NASA said it did not regard the problem as critical and believed it was a long way from having to contemplate abandoning the space station, a 16-nation project.
But the U.S. space agency made plans to keep the visiting space shuttle Atlantis attached to the station for an extra day to help steer the massive complex if the Russian computers, which control navigation, continue to malfunction.
"We're still struggling to understand what the real problem is here," said NASA's associate administrator for spaceflight, Bill Gerstenmaier.
"There's an extremely remote chance that this problem would lead to abandoning the space station," Gerstenmaier said at a briefing. "We're still a long way away from where we would be to de-man space station."
Flight directors told the crew to cut power to noncritical equipment, like lighting, to conserve electricity and fuel in case the shuttle's mission to the space station is extended.
In the worst-case scenario, the three astronauts aboard the station, including NASA's newly arrived Clayton Anderson, could leave in the escape ship, a Russian Soyuz capsule.
As a precaution, the Soyuz was put on battery power on Wednesday for seven hours before one primary and one auxiliary computer system in the Russian modules were rebooted on Thursday, allowing the capsule to be returned to station power.
Two other primary systems, which control navigation and operate life support systems like an oxygen generator and air purifiers, remained shut down.
The station has backup systems for life support and the shuttle has been firing its control jets to help it maintain proper orbit.
RUNNING OUT OF STEAM
"We won't ask you how you're doing because we can imagine," a Russian flight director, speaking through a translator, said to station commander Fyodor Yurckikhin, who skipped a night's sleep to work on the computer problems.
"I hope you haven't run out of steam yet."
The computer glitches began shortly after a newly installed solar wing panel began producing power. Gerstenmaier said it would likely take days to find out why the computers were misbehaving.
Work continued on Thursday on the retraction of the second half of an older solar wing panel that must be moved before the new array can rotate and track the sun for full power.
Spacewalking astronauts Patrick Forrester and Steven Swanson helped guide the old wing into its storage box on Wednesday. Their crewmates James Reilly and John "Danny" Olivas are due to finish the job during a spacewalk on Friday.
Reilly and Olivas also are scheduled to repair a bit of protruding insulation near the rear of the shuttle. A corner of the blanket tore loose during Atlantis' launch six days ago, potentially exposing inner layers of the shuttle's surface to superheated gases on re-entry.
NASA had already extended Atlantis' mission from 11 to 13 days and added a fourth spacewalk to make sure there was enough time to fix the blanket and retract the old solar wing.
The astronauts must also prepare other station systems for the arrival of new laboratory units and life support equipment for an expanded, six-person resident crew.
The U.S. space agency has three years to finish building the complex before the shuttles, which are the only vehicles capable of hauling major components into orbit, are retired.