Six computers began crashing on the Russian side of the international space station Tuesday, limiting the spacecraft's ability to maneuver and produce oxygen. Here are answers to some questions about that problem:
Q: Are the astronauts in danger?
A: No. The seven U.S. astronauts who are visiting the space station from space shuttle Atlantis, and the two cosmonauts and one American who live at the space station, have plenty of oxygen, food and supplies.
Q: What caused the computers to fail?
A: Good question, and if you have the answer, go pick up your NASA engineer's badge. Possibilities include electromagnetic interference and a software problem.
A leading theory is that a bad power connection between the Russian section of the space station and a newly installed pair of solar wings is disrupting the very sensitive, German-built computers.
To test that theory, power between the U.S. and Russian segments was turned off and then the cosmonauts tried to reboot the computers. It didn't work.
So spacewalking astronauts James Reilly and Danny Olivas may physically disconnect the line.
Q: Why all the concern?
A: The space station needs those computers to stay properly positioned in space. That's key for pointing the solar arrays at the sun for power and for shifting the station to avoid occasional large debris that comes flying through space.
Q: What happens if the cosmonauts and astronaut can't get the full computer system up and running?
A: At least in the short run, the crew will stay put. The space shuttle's thrusters help the station stay in place while the spacecraft is docked there.
Once Atlantis leaves on Tuesday, the space station's gyroscopes and thrusters on three Russian spacecraft docked at the station can help maintain control.
Also, a Russian cargo ship, now set to launch in July, can deliver new computers to replace the failed ones.
Q: How long before the crew runs out of oxygen?
A: Even though the Russian oxygen machine doesn't work with the computers down, the crew has plenty of breathable air. There is enough oxygen for 10 people (three station crew and seven shuttle astronauts) to live at the station for 56 days. Once the shuttle astronauts depart, the oxygen supply will stretch even further. Plus the Russian cargo ship will bring more oxygen canisters.
Q: How has the crew's quality of life been changed by the computer failure?
A: Some of Atlantis' lights, computers and cameras were turned off to save energy in case the shuttle spends an extra day docked to the space station to allow more time to figure out the problem.
Q: What would happen if the space station had to be evacuated?
A: NASA calls that unlikely. But if it did happen, the three space station crew members could depart in a Russian Soyuz vehicle that is docked at the station for such emergencies.
Q: What would happen to the space station?
A: It turns out that in space, you can go home again. The outpost can be commanded from Earth, about 200 miles below, while there are no crew members on board.
Before leaving, the cosmonauts and astronaut would power down all but the most essential systems. NASA says vehicles would be able to dock to an unmanned station to deliver new crew members.