In this image taken from video provided by NASA, astronauts Rick Mastracchio, top, and Michael Hopkins work to repair an external cooling line on the International Space Station on Monday, Dec. 24, 2013, 260 miles above Earth. The external cooling line â one of two â shut down Dec. 11. The six-man crew had to turn off all nonessential equipment, including experiments. (AP Photo/NASA)
For two space station astronauts it was like a real-life “Gravity,” just without Sandra Bullock and George Clooney and the whole having to survive in space after an accident.
During a rare Christmas Eve spacewalk – their second in four days – U.S. astronauts Rick Mastracchio and Michael Hopkins ventured outside the International Space Station (ISS) in hopes of wrapping up urgent repairs to a cooling system.
This was only the second Christmas Eve spacewalk in NASA history.
NASA ordered up the spacewalks to revive a critical cooling loop at the ISS. All nonessential equipment had to be turned off when the line conked out Dec. 11, and many science experiments halted.
Mastracchio and Hopkins removed a faulty ammonia pump during Saturday's outing. On Tuesday, they worked to install a new pump 260 miles above the planet.
"It's like Christmas morning opening up a little present here," Mastracchio said as he checked his toolkit.
Mission Control in Houston was in a festive mood during Tuesday's spacewalk. Tabletop Christmas trees, Santa dolls and red Santa caps decorated the desks.
"It is Christmas Eve ... and in this holiday way of giving, we're giving you a spacewalk today," said commentator Rob Navias.
NASA's only previous Christmas Eve spacewalk occurred in 1999 during a Hubble Space Telescope repair mission.
But NASA's most memorable Christmas Eve was back on Dec. 24, 1968. Apollo 8 astronauts read from Genesis, the first book of the Bible, as they orbited the moon on mankind's first lunar flight.
Space station managers considered waiting until January for the repair spacewalks, so an unmanned rocket could blast off with supplies from Virginia. But flight controllers were unable to patch the cooling line by remote control, and the orbiting outpost was considered in too vulnerable a state to put off the spacewalking repairs. The delivery mission was bumped, instead, to January.
A bad valve in the ammonia pump caused the breakdown.
Another team of spacewalking astronauts installed that pump just three years ago, and engineers are perplexed as to why it didn't last longer. NASA hopes to salvage it in the years ahead.
The 2010 replacement required three spacewalks because of the difficulty in removing pressurized ammonia fluid lines. This time, NASA reduced the pressure and the task was simplified, allowing the astronauts to get ahead Saturday. Although three spacewalks were scheduled this time around, Mastracchio and Hopkins' advance work allowed NASA to squeeze everything into two, barring any problems Tuesday.
The second spacewalk was supposed to take place Monday, but was delayed a day to give Mastracchio time to switch to another suit. He inadvertently hit a water switch in the air lock at the end of Saturday's excursion, and a bit of water entered his suit, making it unusable this week.
During the rest of the spacewalk, however, the suits remained dry. Last July, an astronaut almost drowned when water from his suit's cooling system flooded his helmet. Makeshift snorkels and absorbent pads had been installed in the suits as a precaution.
A Moscow-led spacewalk, meanwhile, is set for Friday. Two Russian crew members will install new cameras and fresh experiments outside.
“Gravity,” directed by Mexican Alfonso Cuarón and starring Bullock and Clooney, premiered this year to rave reviews. The space thriller has been nominated multiple times for the Golden Globes, SAG Awards and Critics Choice.
Based on reporting by The Associated Press.