The ISS when it was still under construction I think about 7 years ago The ISS when it was still under construction I think about 7 years ago

Imagine if you’d been in space, weightless, for 5 months, and were scheduled to fly back to Earth on Monday, specifically to southern Kazakhstan (wouldn’t be my first choice but there’s no other option at the moment). But then you were told, wait, first you need to get on your spacesuit and do a space walk to fix a leak. That’s what’s facing one of the astronauts on the International Space Station, which has sprung a serious leak in a cooling system that’s part of the station’s power supply. Here’s my story on the ISS leak, which I just typed up.

If you’re into this sort of thing, you can monitor events at NASA TV. They just played a clip from last night in which an astronaut (I think Commander Chris Hadfield, but I’m not 100 percent sure) talked to someone in Houston. As always, they’re totally calm and professional, and reassuring, and these are people with coolant in their veins. But a spacewalk, improvised, is no trip to the CVS, and the system that needs to be shut down provides one-eighth of the power to the station. They’ve got plenty of workarounds — NASA engineers are geniuses at workarounds, as you may recall from watching “Apollo 13” — but the controller in Houston could not assure the astronauts that the Monday trip home is still a go. “We are still getting our arms fully around that issue,” the controller said. What they need is a “good config” of the station before they can rest assured that they can stick to the previous schedule. Three more astronauts are scheduled to go to the station later this month to bring the crew back up to the full complement of six.

[Update: NASA will hold a newser at 4 p.m., I’m told, and we’ll presumably find out then if the spacewalk is on or not, and whether the astronauts will be coming home as scheduled on Monday. But folks, this is a reminder that human spaceflight is hard. You can’t just call an electrician or a plumber. YOU are the electrician, the plumber, the Mr. Fix-it, plus the scientist, engineer, photographer, tweeter, etc.]