The International Space Station (ISS) has an attitude problem. A computer system wipe-out means the space station is currently depending on the docked space shuttle Atlantis to keep it pointing in the right direction.

More worryingly, in the long term, the dead computers also control the station's altitude, oxygen, and water supplies.

Russian flight controllers are hard at work trying to fix the malfunctioning systems, as speculation grows as to the cause of the glitch.

According to reports, the problems with the computers began shortly after the new truss segment was installed on Monday. On Tuesday, four of the Russian's six computers went offline, leaving just one guidance machine and one command-and-control machine. By Wednesday, these had crashed as well, leaving the space station effectively adrift in space.

Mike Suffredini, manager of the space station programme at the Johnson Space Centre in Houston, told reporters he thought the idea of all six Russian machines having a hardware failure at the same time was unlikely.

"It appears to me that something has changed in the environment, either something in the (space) environment or the source of power to these computers is different coming from S3/S4 for reasons we do not understand," he said.

He added that the Russians have suggested switching off the power from the new S3/S4 truss segment and trying to bring the systems back online using only the internal power systems. However, the Russian section is not self sufficient in power terms and needs the power from the S3/S4 truss. If the new segment is the problem, it will still have to be solved.

The computer crash could mean Atlantis stays at the ISS for another day, to allow the Russian team more time to correct the problem.

But managers are hopeful that the problem will be resolved within a few days. If not, the astronauts might all have to return to Earth. The Shuttle crew would fly back in Atlantis, and the rest of the ISS personnel would have to travel in a Soyuz spacecraft. ®

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