WASHINGTON (AP) Two astronauts are preparing for a possible impromptu spacewalk Saturday to work on a coolant leak in the power system at the International Space Station.

NASA says the six-member crew at the station is not in danger. The ammonia leak forced the shutdown of one of eight solar panels that power the station, but the outpost can operate fine with only seven, spokesman Kelly Humphries said.

NASA will decide Friday evening whether the spacewalk is needed Saturday. One of the spacewalk veterans slated for the job is due to return to Earth on Monday, one of the reasons NASA wants to do it this weekend, he said.

Station Commander Chris Hadfield of Canada told NASA flight controllers Friday that the six-member crew is completely ready for the spacewalk.

"I think it's really smart the way we're all proceeding here," Hadfield radioed down to Earth. "It's the right thing to do."

Hadfield tweeted that the crew was working "like clockwork" and said the two astronauts were already getting their spacesuits ready, adding "Cool!"

The leak is in one of the radiator lines that chill the power systems. NASA spokesman Rob Navias said the line was expected to run out of ammonia coolant Friday. Power has been rerouted and is operating normally, he said.

NASA suspects the leak might be on the far left truss of the station from a certain box, but isn't certain. There's a spare box right near it and spacewalking astronauts can swap it out if that's the source, Navias said.

"What's causing the leak is unknown because there's a lot of plumbing underneath the box itself," he said. "We've had lots of experience in installing and replacing coolant loop hardware."

If needed, U.S. astronauts Chris Cassidy and Tom Marshburn would make about a six-hour spacewalk. They have trained for this type of repair. It is what NASA calls one of the "Big 12" types of emergency repair work that all spacewalking astronauts prepare for in advance, Navias said.

Follow this link:

NASA mulls spacewalk to fix space station leak