One of the "Big 14" problems that NASA thought would likely strike the International Space Station has reared its ugly head again. A cooling system malfunction has cut the space station's temperature-regulating capabilities in half, forced the shutdown of some science experiments, and possibly delayed the launch of a private spacecraft resupply mission.
The latest problem affected one of two pumps that circulate ammonia coolant in two cooling loops outside the space station, according to SPACE.com. Those exterior cooling loops radiate excess heat transferred over from internal cooling systems inside the station and also cool the electricity-generating solar panels on the outside of the orbital outpost.
Such pump failures related to the space station's electrical system are among the critical 14 considered serious enough to require quick fixes before anything else goes wrong.
NASA engineers suspect that the main culprit behind the latest malfunction is a flow control valve in the pump connected to Loop A, one of the two exterior cooling loops. The problem has forced the space station crew to rely upon Loop B's cooling capabilities and shut down some non-critical systems such as science experiment hardware in the U.S. Harmony node, Japan's Kibo lab, and Europe's Columbus module, SPACE.com reports. (Freezers used to preserve scientific samples were still operating normally, according to NBC News.)
The cooling problem could also delay the launch of the commercial Cygnus spacecraft on its first official resupply mission to the space station next week, NASA officials said.
Current space station crew members—two American astronauts, three Russian cosmonauts and one Japanese astronaut—stuck to their normal sleep schedule while NASA mission controllers in Houston scrambled to figure out whether either a software patch or spacewalk repairs might become necessary, ABC News reported.
The pump in question was previously replaced during three spacewalks in August 2010 whose aim was fixing a similar Loop A shutdown. At the time, James Oberg, a journalist and former NASA aerospace engineer, wrote for IEEE Spectrum about how NASA trains its space station crews to handle general spacecraft maintenance during spacewalks as a first step for dealing with "Big 14" problems. Once a specific repair is needed, the space station astronauts spend an additional two weeks or so practicing for the task at hand.
Perhaps future space station crews will be able to make more use of NASA robots descended from the likes of Robonaut 2 to keep the orbital outpost repaired. But for now, humans will still have to suit up and carry out the long, tedious spacewalks necessary to keep the space station going despite a breakdown.