Ammonia leak on space station causes concerns, power re-route

The crew of the International Space Station might be taking an unscheduled space walk tomorrow to check out what appears to be a leak in one of the recirculating ammonia loops used to keep the station's power-generating solar arrays within operating temperature.

The leak was first noticed on Thursday morning, when ISS commander Chris Hadfield (who tweets under the handle @Cmdr_Hadfield and has about 750,000 followers) radioed Mission Control in Houston to report what appeared to be some white flakes drifting away from the P6 segment of the station's backbone truss. The truss hosts the station's photovoltaic arrays and radiators; each solar array has its own independent ammonia-based cooling system.

Transverse view of ISS (with Endeavour docked). Integrated Truss Structure visible in foreground, with P6 segment closest to camera.

NASA

Mission Control confirmed on Thursday that the flakes were in fact from the truss' coolant loop, and that the ammonia levels were indeed dropping. If unchecked, the leak is expected to deplete the P6 array's supply of ammonia by tomorrow morning. The solar arrays generate and provide electricity to eight separate power channels, which feed into the ISS's various systems. ISS ground controllers are switching load off of the affected power channel in anticipation of the array going offline. It is responsible for about 12.5 percent of the ISS's total electricity generation.