CAPE CANAVERAL, Florida, United States - Two NASA astronauts, their spacesuits rigged with snorkels in case of a water leak, floated outside the International Space Station for 5-1/2 hours on Saturday, successfully completing the first steps to fix the outpost's cooling system.
The spacewalk, which was broadcast live on NASA Television, was the first for NASA since July when the spacesuit helmet worn by Italian astronaut Luca Parmitano began filling with water, a situation that could have caused him to drown.
No such leaks were detected in Saturday's spacewalk, the first of two or possibly three that will be needed to complete the cooling system repair.
The operation was prompted by the Dec. 11 shutdown of one of the station's two US ammonia cooling systems, which forced the crew to turn off non-essential equipment and shut down dozens of science experiments.
While the six-member crew is not in danger, the remaining cooling system cannot support the three laboratories and other modules on the US side of the $100 billion station, a project of 15 nations. The Russian side of the station has a separate cooling system.
Engineers at the Johnson Space Center in Houston tried devising ways to bypass a suspected faulty pump valve, but with time running short, managers decided to have astronauts replace the pump, located outside the station, with a spare.
The work, which began shortly after 7 a.m. EST (1200 GMT), went smoothly, with station flight engineers Rick Mastracchio and Mike Hopkins finishing up an hour earlier than expected.
They were able to not only disconnect the old pump, but also remove it from its pallet on the station's exterior truss, a task slated for a second spacewalk originally planned for Monday and later delayed until Tuesday, NASA said late on Saturday.
A third spacewalk, if needed, presumably also would slip one day, from Wednesday to Thursday.
NASA said an extra day was needed to prepare a backup spacesuit for Mastracchio to use.
"During repressurization of the station's airlock following the spacewalk, a spacesuit configuration issue put the suit Mastracchio was wearing in question for the next excursion," NASA said in a statement.
The issue is not related to the water leak that was seen during the July spacewalk, NASA said.
"Both Mastracchio and Hopkins reported dry conditions repeatedly throughout (Saturday's) activities," the statement said.
Mastracchio, a veteran of six previous spacewalks, and Hopkins, a rookie, wore spacesuits that were modified to protect them from another possible water leak. The problem in July was traced to contamination in piece of equipment called a fan pump separator that circulates water and air in the spacesuit and removes moisture from air.
How the water-separator portion of the device became clogged remains under investigation.
Hopkins wore Parmitano's spacesuit, but it had been outfitted with a new fan pump separator. In addition, both Hopkins and Mastracchio rigged their helmets with homemade snorkels, fabricated out of pieces of plastic tubing and Velcro, which they could have used for breathing in case of another water leak. The helmets also included water-absorbent pads.