American astronaut Reid Wiseman and German spaceman Alexander Gerst worked to move a broken pump into its proper storage location, a long overdue job.
U.S.-based spacewalks were curtailed in July 2013 after an Italian astronaut nearly drowned because of a flooded helmet. NASA solved the problem with the suit's water-cooling system. Then concern arose over the spacesuit batteries.
New batteries arrived late last month, clearing the way for Tuesday's spacewalk and another one scheduled for next week.
The 350-kilogram pump on the move Tuesday is about the size of a double-door refrigerator. It ended up in temporary storage during urgent spacewalking repairs to the station's ammonia-cooling system last December; NASA did not want to waste time back then putting the pump in the correct long-term location, given all the spacesuit worries.
This was the first spacewalk ever for Wiseman and Gerst. Wiseman's exuberance was evident as he emerged from the hatch into the vast darkness over the Pacific.
"Wow, looks like we've almost got a full moon out here. It's beautiful," Wiseman said. When the glow of sunrise started to appear several minutes later, he shared his excitement again with Mission Control.
A follow-up spacewalk is scheduled for Oct. 15 to further whittle down NASA's lengthy to-do list, on hold since the 2013 close call. That spacewalk will be conducted by Wiseman and fellow American Butch Wilmore, a newcomer.
A week after that, two of the three Russians on board will perform a spacewalk on their country's side of the orbiting outpost. The Moscow-led spacewalks were unaffected by NASA's spacesuit troubles.
Absorbent pads and makeshift snorkels
NASA considered December's U.S. spacewalks — to replace the failed ammonia pump and thereby restore full cooling to the space station — too important to wait. The same went for a critical spacewalk by Americans in April to replace a dead computer.
The helmets used by Wiseman and Gerst contained absorbent pads and makeshift snorkels in case of water leakage. The items became mandatory following last year's close call experienced by Italian spacewalker Luca Parmitano, safely back on Earth for nearly a year now.
As for the spacesuit batteries, NASA sent up replacements on the latest SpaceX cargo ship and Russian Soyuz capsule. Ground testing uncovered a potential fuse problem earlier this year, and NASA opted to switch out the batteries on board.