Cosmic Log

Alan Boyle, Science Editor NBC News

7 minutes ago

Two NASA astronauts began a high-stakes series of spacewalks to repair the International Space Station's cooling system on Saturday, outfitted for the first time with snorkels in their helmets to keep them from drowning.

"Beautiful day," astronaut Rick Mastracchio said after the spacewalk's start at 7:01 a.m. ET. He took a moment to look down at Earth as the station passed more than 250 miles (400 kilometers) over Africa. "Quite a view," he said.

Mastracchio and fellow spacewalker Mike Hopkins are taking on three spacewalks through Christmas Day to replace a coolant pump module with a faulty valve. Last week's valve malfunction cut the station's cooling capability in half, forcing mission managers to shut down non-critical systems on the $100 billion-plus orbital outpost.

Worries about waterGround controllers couldn't get the valve back in service by remote control, which led to the current plan for three spacewalks running through Christmas Day. Replacing the refrigerator-sized module is one of the station's expected maintenance tasks but the job has been complicated by the fact that an Italian spacewalker, Luca Parmitano, almost drowned in July when water pooled up in the helmet of his U.S.-made suit.

That incident led NASA to suspend U.S. spacewalks while the station's crew and controllers worked to track down the source of the problem. They think they've identified the cause: previously undetected contamination that clogged up the system designed to remove moisture from the suit. And they've given a clean bill of health to the spacesuits Mastracchio and Hopkins are using.

"I would be surprised if we have a problem with the suits," Mike Suffredini, NASA's space station program manager, told reporters this week.

But just in case, the astronauts are wearing absorbent pads on their necks that should pick up the first signs of excess moisture in the helmet and are primed to stop the spacewalk if those pads start feeling squishy. They also have jury-rigged snorkel tubes within easy reach of their mouths in the event that water starts covering their faces.

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Snorkel-equipped spacewalkers start critical repair job on space station