Half of the International Space Station's cooling system has suddenly shut down, forcing the astronauts on board to power down equipment and face the likelihood of urgent spacewalking repairs. After huddling today, NASA managers gave preliminary approval for a pair of spacewalks, the first of which would take place later this week. Officials stressed that the six occupants—three Americans and three Russians—were in no danger, and that the orbiting complex was in a stable situation.
Two American astronauts were already scheduled to conduct a spacewalk Thursday for routine maintenance, though the repairs would supersede the original chores. The trouble arose last night, when one of the two ammonia-fed cooling loops shut down. Alarms sounded throughout the sprawling outpost as the circuit breaker for the pump in that line tripped. Much of the station is operating on a single string, with no safeguard in case of further cooling system failures. (Read more International Space Station stories.)