Space Station Crew Safe After Coolant Failure

Backup systems kick in after broken pump shuts off ammonia supply to critical systems and instruments.
NASA said it plans to send astronauts aboard the International Space Station on an emergency spacewalk this week to repair a cooling system that failed Saturday.

The space agency added that ISS's current residents—three U.S. astronauts and three Russian cosmonauts—were not in any danger.

NASA said the problem began when a circuit breaker tripped on Saturday night, causing the failure of a pump that feeds an ammonia-based coolant solution to key systems and avionics instruments. Crewmembers attempted to reset the breaker and restart the pump on Sunday but the effort was not successful.

Despite the breakdown, NASA said the ISS remains in a "stable configuration," with backup systems working to ensure that critical components on the ISS don't overheat.

U.S. astronauts Doug Wheelock and Tracy Caldwell Dyson will likely undertake at least two spacewalks later this week to swap out the broken pump module, which is located in the station's S1 truss. The ISS is carrying two spare pump modules that can be used as replacements.

"Although a final decision on a new spacewalk plan is still pending engineering and timeline analysis, the most likely scenario would call for an initial spacewalk no earlier than Thursday by Wheelock and Caldwell Dyson to replace the Pump Module and structurally bolt it into place on the S1 truss," NASA officials said, in a statement released Sunday.

NASA said it would reschedule tasks that were to be performed on a spacewalk that had previously been scheduled for this week but which has now been cancelled due to the pump failure.