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Two American astronauts will begin a series of spacewalks Saturday to swap out a crippled valve that helps cool the International Space Station, and NASA announced Wednesday it will equip them with snorkels just in case their helmets accidentally fill with water.
The snorkels and new absorbent padding are spacesuit modifications NASA made to prevent what happened in July when an Italian astronaut nearly drowned as his helmet filled with water.
“We’re ready to go out the door,” Michael Suffredini, International Space Station program manager, said in a news briefing on Wednesday in which he detailed at least three spacewalks to make the repairs.
The first spacewalk is planned for Saturday with another set for Monday and next Wednesday — Christmas Day.
Flight controllers on the ground tried, but were unable to, remotely fix the broken cooling valve in recent weeks. Since then managers have opted to use spacewalks to install the spare refrigerator-sized pump module that is already stored aboard the space station.
“For the better part of valor we had to pick a path,” Suffredini said.
One line of the two-line cooling system — a series of tubes, pumps and radiators that circulates ammonia — was shut down last week, forcing the six-person space station crew to turn off nonessential equipment and hold off on some scientific experiments.
Americans Michael Hopkins and Rick Mastracchio will do the three-day repair job outside the station. The crew on board the space station also includes three Russians and one Japanese.
"The next week will be busy with spacewalks so not much tweeting from here," Mastracchio tweeted from space on Tuesday.
Still, spacewalks do carry risks, particularly in light of the July incident in which an Italian astronaut Luca Parmitano almost drowned during a spacewalk because of water seeping into his helmet.
Though the root cause of the water leak is still unknown, engineers have determined that some of the filters inside the helmets were contaminated. Those filters were sent back to Earth for further analysis. The remaining spacesuits that will be used in the upcoming spacewalks got new filters and were cleaned, tested and modified.
As part of the probe into the cause of the water in the helmet, scientists have also tested the chemistry of the water itself for a potential source of the contamination.
This time around, the spacesuits will be equipped with absorbent padding to catch any extra moisture from the suits — and actual snorkels. The snorkels are modified water line vent tubes that were snipped into short lengths and will be attached to the spacesuits with Velcro to provide emergency oxygen.
"This is your last resort, if water is encroaching in your face like what happened with Luca on the last EVA (extra-vehicular activity), the crew member could lean down and use this to breathe," Allison Bolinger, NASA’s lead spacewalk officer, said Wednesday.
“We think we’re taking out two clean suits to the best of our knowledge,” said Dina Contella, space station flight director. “We can’t rule out that we wouldn’t have water in the helmet again but that is what the ops communication is for and the new hardware is for but we’re still really working on what the root cause is.”
NASA engineers have emphasized that despite failure of the valve and shutting down of the cooling line, astronauts are comfortable and not in any danger.
It turns out this same pump — a bulky, 780-pound rectangular module — was replaced by spacewalking astronauts in 2010. Three spacewalks were needed then.
The lessons learned will help Mastracchio and Hopkins to finish the job more quickly, managers said.
Mastracchio is a veteran spacewalker, and Hopkins, a first-time space flier, trained for just such a repair before rocketing into orbit. They have been preparing for the spacewalks all week.
Due to the repair work, Orbital Sciences Corp. will hold off on a planned Thursday night launch of its Cygnus cargo ship from Wallops Island, Va. That commercial launch, to restock the space station with supplies, has been postponed until mid-January.
Tom Costello of NBC News and The Associated Press contributed to this report.