On late Thursday, "a very steady stream of flakes" was spotted drifting away from the space station — an apparent ammonia leak. The crew isn't in any danger, but an emergency spacewalk is being planned to inspect and fix it.
Liquid ammonia is used as a coolant to extract the heat that accumulates in electronic systems, dumping that excess energy through a radiator array. Commander Chris Hadfield and crew spotted the leak near the station's port side, at the far end of the power truss, which is the structure that holds the station's solar arrays. NASA thinks the problem has something to do with the 2B power channel, one of eight fed by the lab's solar arrays.
"They were coming out cleanly and repeatedly enough that it looked like it was a point source they were coming from," Hadfield noted when speaking to mission controllers.
In order for the coolant system to operate normally, it needs as lead 40 pounds of ammonia. Based on the amount of leakage observed, coolant levels could drop below that level and shut down within 48 hours. If that were to happen, the lab's six-person crew would need to reconfigure the station's cooling systems. The ISS can operate without all the cooling channels, but the total loss of a coolant loop would require some serious hacks to prevent some electrical systems from overheating.
As of this morning, a spacewalk is being planned to address the situation. According to Hadfield, astronauts Chris Cassidy and Tom Marshburn are currently getting their suits and airlock ready for what appears to be a Saturday spacewalk.
Here are some highlights from Chris Hadfield's twitter stream:
You can watch the team's preparation for the space walk here:
Listen to how Hadfield explained the situation to the ground crew at NASA.