NASA astronauts will be heading out to conduct critical repairs on the International Space Station early Saturday morning. The 6 1/2-hour spacewalk, the first in a series, will replace a faulty piece of cooling equipment.
Astronaut Rick Mastracchio is a seasoned veteran, while his partner Mike Hopkins is on his first-ever spacewalk. But NASA officials emphasize that the scenario does not resemble the recent blockbuster Gravity.
"No, no, no," NASA spokesman Josh Byerly told NPR.
Still, the station is in a bit of a tight spot. On Dec. 11, a valve inside the orbiting outpost's cooling system quit working. One of the two cooling loops had to be shut down, and as a result, so did a lot of the station's electronics, which generate too much heat to be handled by the internal atmosphere.
The shutdowns didn't endanger the crew, but they did put a stop to many of the experiments on the station. They also have prevented an unmanned resupply mission from launching.
Initially, engineers hoped they could fix the problem remotely. But over the past week, it's become apparent that a series of spacewalks is the best solution. The spacewalks will remove a 780-pound pump module, which contains the faulty valve, and replace it with a spare stored outside the station. Astronauts performed the same repair when a different fault caused the pump to shut down in 2010.
The process is tricky. The enormous mass of the module means astronauts must move it slowly and carefully. In addition, the cooling system uses ammonia, a toxic chemical that could pollute the station's atmosphere if astronauts accidentally carried any of it inside.
Adding to the difficulty is that one of the spacesuits had a serious problem the last time it was used. Luca Parmitano was wearing Suit #3011 on a July spacewalk when he noticed water leaking into the back of his helmet.
"The water kept trickling until it completely covered my eyes and my nose," he said in a July interview. He and his partner rushed back into the airlock, and it later became clear that he had come close to drowning in space.
NASA now believes that the water came from part of a cooling system inside the spacesuit. It has replaced some parts of Suit #3011 and is taking additional precautions. Astronauts will wear absorbent pads in the back of their helmets. And they'll be carrying homemade snorkels. The snorkels will connect to the midsection of the suit and should provide a last resort if astronauts find their heads immersed in water.
The first spacewalk will begin shortly after 7 a.m. Eastern time Saturday. Additional spacewalks are scheduled for Dec. 23 and on Christmas, Dec. 25.