A malfunction caused the shutdown of two key computers that control navigation and oxygen production on the Russian side of the International Space Station. Later, all six main control computers reported a glitch that forced astronauts on Thursday to turn off equipment in the docked shuttle Atlantis to conserve energy.

Officials are optimistic, although this glitch has baffled space engineers in Houston and in Moscow. "We've got a plan to go work the problem," said NASA Associate Administrator William H. Gerstenmaier during a briefing Thursday at Johnson Space Center in Houston. "I don't consider this critical."

This incident could further delay the Atlantis space shuttle, scheduled to return to Earth with Indian-American astronaut Sunita Williams and six others. NASA is actually considering the possibility of extending the space shuttle's stay one or two days. Without the computers, the station cannot maintain proper orbit and its crew cannot stay on board in a worst-case scenario.

Atlantis is still docked at the space station, so the astronauts periodically fired its thrusters to help maintain the space station's position while the computers were down.

The computers were built and delivered by the European Aeronautic Defence and Space Company EADS, the largest European aerospace corporation, but the cause of the sudden simultaneous failures was not identified, although some emergency repairs have begun.
So far, there have been several attempts to reboot the six control computers, but none of them worked. Without the main control computers, the Russian rocket thrusters can't be activated to orient the station in space, which leaves them both on the station itself and on the unmanned Progress freighters that bring up supplies without control.

Russian engineers are working to restore the system and "they've made a lot of progress," said NASA space station flight director Holly Ridings. "There are some cleanup steps to do still and some investigation."