CAPE CANAVERAL, Fla. — Half of the International Space Station’s cooling system shut down over the weekend, forcing astronauts to power down equipment and face the likelihood of spacewalking repairs.
NASA managers gave preliminary approval Sunday for a pair of spacewalks. Two of the Americans on board were already scheduled to conduct a spacewalk Thursday for routine maintenance, though the repairs would supersede the original chores.
Officials emphasized that the six occupants were in no danger.
The trouble arose Saturday 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, causing the pump to stop working.
The cooling system is critical for on-board operations. The two ammonia lines ensure that all the station’s electronic equipment does not overheat and with one of those out of commission, there is no safeguard in case of a second failure.
Astronaut Tracy Caldwell Dyson hustled through the equipment shutdown procedures and, with crewmate Douglas Wheelock, installed a jumper cable to keep all the rooms cool.
Any repairs later this week will involve replacing that ammonia pump, a difficult job that would require two spacewalks. Two spare pumps are stored on the outside of the station.
The first repair spacewalk likely would occur Thursday at the earliest, with the second excursion two or three days later.
Among the equipment powered off for now: the Global Positioning System circuit, several power converters and a set of devices that route commands to various equipment.
Two of the four gyroscopes initially were shut down — part of the space station’s pointing and navigating system. But the crew installed a jumper cable to bring up a third gyroscope, leaving the station in a much more stable position.
On board are three Americans and three Russians.