CAPE CANAVERAL, Fla. -- A computer crash aboard the International Space Station sent the 17-story complex into a slow drift Monday, temporarily disrupting voice communications with the ground while sapping power aboard the outpost.
Science research aboard the outpost also came to a standstill, but NASA officials said that neither the station nor its crew -- Russian cosmonaut Yuri Onufrienko and U.S. astronauts Daniel Bursch and Carl Walz -- ever were in jeopardy.
"The crew was in no danger as a result of that computer failure whatsoever," said James Hartsfield, a spokesman for NASA's Johnson Space Center in Houston. "Basically, (it was) an interruption to their work day."
Midway through their 61st day in space, a critical station computer shut down inexplicably, disabling the outpost's attitude control system, which keeps the complex properly oriented as it circles high above the planet.
Located in the station's Russian-built crew quarters, the computer -- which crashed about 9 a.m. EST (1400 GMT) -- normally routes data from Russian pointing sensors to four, dome-shaped U.S. gyroscopes that are mounted to a metallic outpost truss.
The loss of that capability made it impossible for the gyroscopes to control the station's orientation in orbit. And with the station drifting freely, its solar wings could not properly track the sun, which reduced their ability to gather sunlight so it could be converted to electricity.What's more, the station's main U.S. radio antenna could not be precisely aimed while the outpost was drifting. That essentially made it impossible for the crew to communicate with ground controllers unless the station was passing over Russian ground tracking stations in central Asia.
Ground controllers ordered the crew to turn off science experiments and back-up station systems to conserve power until the problem could be fixed.
And while they still could monitor station systems, and computer commands still could be beamed up to the outpost via Russian tracking stations, engineers on Earth had a limited ability to communicate with the crew while the problem was being sorted out.
"We are following, and we're cheering you along," NASA astronaut Michael Fossum told the crew as the outpost passed over a Russian ground station. "We just don't have the chance to send the cheers up via audio."
"You all are doing great down there, too," Bursch replied. "Happy Monday."
Added Fossum: "It's definitely Monday."
The station drift ultimately was halted about noon EST (1700 GMT), and that enabled the crew to begin a lengthy effort to properly position solar arrays and then re-power systems and experiments that had been shut down to preempt any severe electrical outage.
"We should have all this wrapped up in two (orbits) -- the pointing part," Fossum told the crew. "The rest of the clean-up is going to take awhile."
The cause of the computer crash was not immediately apparent.
It was the first significant station computer failure since April 2000, when the outpost's three prime U.S. command and control computers crashed while a visiting shuttle crew was at the complex to erect a $600 million Canadian robot arm.
Those computer shutdowns eventually were traced to hard drive failures. To prevent similar failures in the future, Onufrienko, Walz and Bursch have been installing new solid-state memory devices in the U.S. command and control computers.
Launched Dec. 5 aboard shuttle Endeavour, Onufrienko, Bursch and Walz represent the fourth full-time crew to live and work on the station since it opened for business in November 2000. Now two months into a planned five-and-a-half-month station tour, the trio remains scheduled to return to Earth aboard Endeavour in mid-May.
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