By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - Astronauts aboard the International Space Station prepared for an unexpected series of spacewalks by fabricating spacesuit snorkels they can use for breathing in case of another helmet water leak, NASA officials said on Wednesday.
The spacewalks, the first of which is slated to begin at 7:10 a.m. EST (1210 GMT) on Saturday, are needed to replace one of two cooling pumps outside the $100 billion complex, which flies about 250 miles above Earth.
U.S. spacewalks have been suspended since July after a spacesuit helmet worn by Italian astronaut Luca Parmitano filled with water, causing him to nearly drown.
The underlying cause of the leak remains under investigation but engineers have learned enough to make modifications so the problem will not happen again, NASA managers told reporters during a conference call.
"I would be surprised if we have a problem with the suits," said space station program manager Mike Suffredini.
As a contingency, the spacewalkers' helmets will be outfitted with absorbent pads and home-made snorkels to funnel air from the body of the water-cooled suits into an astronaut's mouth, if needed.
The snorkels, which were fabricated by the crew on Sunday, are made from plastic water line vent tubes used in the spacesuits.
"This is your last resort," said Allison Bolinger, lead spacewalk officer. "If water is encroaching your face, similar to what happened to Luca, the crewmember can lean down and use this (the snorkel) to breathe."
First-time spacewalker Michael Hopkins will wear Parmitano's spacesuit, but it has been outfitted with a new fan pump separator, a device that circulates water and air and removes moisture from air.
The fan pump separator from Parmitano's suit was flown back to Earth for analysis and engineers found tiny holes in the water-separator portion of the device were clogged.
That allowed water to back up into the fan portion, get into a vent loop and enter the helmet, said space station flight director Dina Contella.
Still unknown is how the water was contaminated.
"Unfortunately, it's a pretty complicated water chemistry problem," Contella said.
Suffredini said: "We believe the lines we're using today are clean. We've put in new filters and we think the filter system works."
A new fan pump separator is among the cargo aboard Orbital Sciences Corp's first supply ship to the station which had been slated to launch this week. But it is being delayed until mid-January so NASA can tackle the higher-priority work of getting the station's cooling system back in operation.
One of two ammonia cooling systems shut down on December 11, forcing astronauts to turn off unnecessary equipment and suspend some science experiments.
The U.S. side of the station has a second cooling system, but it cannot accommodate all the gear.
Hopkins will be joined by six-time spacewalker Rick Mastracchio for three spacewalks to replace the faulty cooling system with a spare that is in storage outside the station.
In addition to Saturday's 6.5-hour outing, spacewalks are planned for Monday and Wednesday.
(Editing by Kevin Gray and Mohammad Zargham)