Shuttle Endeavour astronauts Drew Feustel and Mike Fincke left the station's Quest airlock at about 2:15 a.m. EDT to begin the second of four spacewalks planned during Endeavour's 16-day mission, the next-to-last in the US space shuttle program.
RELATED:US astronauts finish spacewalk outside station‘Endeavour’ to run experiment that crashed with Ilan RamonIt was the fifth outing for Feustel, a former Hubble Space Telescope repairman making his first trip to the space station, and the seventh for Fincke, who previously served as a flight engineer and then as commander of the orbital outpost.Fincke's previous spacewalks were done Russian-style, in stiff Orlon spacesuit."The American spacesuit is called the Extravehicular Mobility Unit -- 'mobility' is the key word for me," Fincke said in a preflight interview."When I put on the American spacesuit it's only running about four pounds per square inch (27.57 kilopascals) (of pressure) and all of a sudden, I got a lot more mobility.When we're building the complex parts of the space station, we needed an EMU, whereas Orlan is good for routine maintenance on the outside where you don't need to have such dexterity."Nimble hands will be useful for the jobs facing Fincke and Feustel on Sunday. First on the astronauts' to-do list is the potentially messy job of topping off a tank of ammonia, used in the station's cooling system.Feustel and astronaut Greg Chamitoff set up the spare ammonia line during the mission's first spacewalk on Friday. Tapping the new line should fix a slow leak somewhere in the original plumbing."This isn't your household cleaner ammonia," Fincke said before flight."This is high-grade industrial ammonia so we have to be super careful not to get it on us or to spill it because it's quite dangerous if we brought it back inside."NASA has a procedure to decontaminate the astronauts' spacesuits if they do get any ammonia on them.Feustel and Fincke also plan to lubricate the massive joint that keeps the station's left-side power-generating solar arrays rotating to track the sun."We found the original design had some extra friction that we weren't expecting and it started to grind our joint, so we've, every couple years, started to add some grease on it and it rotates great," Fincke said.