A coolant system glitch on the International Space Station has forced several of the orbital outpost’s modules offline as astronauts and ground control manage the problem. The crew are not in danger and ground control teams are currently working to see how best to troubleshoot.

The issue, that occurred early on Wednesday, focuses on one of the space station’s two external ammonia cooling loops, along which the station’s electrical systems use to regulate their temperatures. The loop “automatically shut down when it reached pre-set temperature limits,” said NASA in a statement. It is thought that a flow control valve in the ammonia pump itself may have malfunctioned.

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The shutdown has affected Loop A, prompting station managers to move some electrical systems over to Loop B while prioritizing life support systems, electrical systems and experiments. All other non-essential systems have been shut down in the U.S. Harmony node, Japanese Kibo laboratory and the European Columbus laboratory.

According to Alan Boyle over at NBC News, should extra-vehicular activity (EVA) be deemed necessary, it could take up to two weeks to plan for the spacewalk operation to fix the faulty pump. This breakdown, known as a “Big 14″ maintenance issue, crops up intermittently during normal operations of the space station. Boyle points out that other maintenance issues like this have cropped up in 2012, 2011, 2010, 2009 and 2007.

In May, the crew of Expedition 35, commanded by Canadian astronaut Chris Hadfield, were confronted with an ammonia leak from the exterior of the space station. In that case, the repair operation was planned and executed in two days. The leaky Pump and Flow Control System (PFCS) box located on the space station’s Port 6 truss was replaced.

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On this occasion however, it may take some time for the space station’s Expedition 38 crew and ground control to troubleshoot the problem and to decide whether a spacewalk is needed or whether a software fix can be found.

The Expedition 38 crew include NASA astronauts Rick Mastracchio and Mike Hopkins, Russian cosmonauts Sergey Ryazanskiy, Oleg Kotov and Mikhail Tyurin, and the Japanese Space Agency's Koichi Wakata.

Underlining the quasi-routine nature of this partial shutdown, the NASA statement concluded: “The crew is safe and preparing to begin a normal sleep shift while experts on the ground collect more data and consider what troubleshooting activities may be necessary.”

Image: This picture of the International Space Station was photographed from the space shuttle Atlantis as the orbiting complex and the shuttle performed their relative separation in the early hours of July 19, 2011. Credit NASA