MARCIA DUNN, AP Aerospace Writer
CAPE CANAVERAL, Fla. (AP) — Astronauts sailed through the first of a series of urgent repair spacewalks Saturday to revive a crippled cooling line at the International Space Station.
The two Americans on the crew, Rick Mastracchio and Michael Hopkins, successfully removed an ammonia pump with a bad valve __ well ahead of schedule. That task had been planned for the next spacewalk on Monday.
"An early Christmas," observed Mission Control as Mastracchio pulled the refrigerator-size pump away from its nesting spot.
If Mastracchio and Hopkins keep up the quick work, two spacewalks will be enough to complete the installation of a spare pump and a third spacewalk will not be needed on Christmas Day as originally anticipated.
The breakdown 10 days earlier left one of two identical cooling loops too cold and forced the astronauts to turn off all nonessential equipment inside the orbiting lab, bringing scientific research to a near-halt and leaving the station in a vulnerable state.
Mastracchio managed to unhook all four ammonia fluid lines on the pump with relative ease, occasionally releasing a flurry of frozen ammonia flakes that brushed against his suit. Next he undid the electrical connections. A small O-ring floated away, but he managed to retrieve it.
"I got it, I got it, I got it. Barely," Mastracchio said as he stretched out his hand.
"Don't let that go, that's a stocking stuffer," Mission Control replied.
"Don't tell my wife," Mastracchio said, chuckling, as he put it in a small pouch for trash.
Mastracchio, a seven-time spacewalker, and Hopkins, making his first, wore extra safety gear as they worked outside. NASA wanted to prevent a recurrence of the helmet flooding that nearly drowned an astronaut last summer, so Saturday's spacewalkers had snorkels in their suits and water-absorbent pads in their helmets.
Midway through the spacewalk, the spacewalkers were still dry. But Mastracchio's toes were so cold that he had to crank up the heat in his boots. Mission Control worried aloud whether it was wise to stretch the spacewalk from the planned 6½ hours to 7½ hours to get ahead, given Mastracchio's discomfort. But he assured everyone he'd be fine once he warmed up.
Adding to the excitement 260 miles up, a smoke alarm went off in the space station as the astronauts toiled outside. It was quickly found to be a false alarm, and Mission Control reassuringly told the crew to continue with the spacewalk.
The pump replacement is a huge undertaking attempted only once before, back in 2010 on this very unit. The two astronauts who tackled the job three years ago were in Mission Control, offering guidance. Mastracchio promised to bring back a wire tie installed on the pump by the previous spacewalkers. "Oh, awesome, thanks Rick," replied the astronaut in Mission Control who put it on.
The 780-pound pump is about the size of a double-door refrigerator and extremely cumbersome to handle, with plumbing full of toxic ammonia. Any traces of ammonia on the spacesuits have to be dissipated by the time the astronauts go back inside, to avoid further contamination.
NASA's plan initially called for the pump to be disconnected Saturday, pulled out Monday and a fresh spare put in, and then all the hookups of the new pump completed Wednesday. But if the work is finished on the first two spacewalks, the third won't be needed.
In the days following the Dec. 11 breakdown, flight controllers attempted in vain to fix the bad valve through remote commanding. Then they tried using a different valve to regulate the temperature of the overly cold loop, with some success. But last Tuesday, NASA decided the situation was severe enough to press ahead with the spacewalks. Although the astronauts were safe and comfortable, NASA did not want to risk another failure and a potential loss of the entire cooling system, needed to radiate the heat generated by on-board equipment.
NASA delayed a delivery mission from Wallops Island, Va., to accommodate the spacewalks. That flight by Orbital Sciences Corp., which should have occurred this past week, is now targeted for Jan. 7.
Until Saturday, U.S. spacewalks had been on hold since July, when an Italian astronaut's helmet was flooded with water from the cooling system of his suit. Luca Parmitano barely got back inside alive.
Engineers traced the problem to a device in the suit that turned out to be contaminated — how and why, no one yet knows.
For Saturday's spacewalk, Hopkins wore Parmitano's suit, albeit with newly installed and thoroughly tested components.
Just in case, NASA had Mastracchio and Hopkins build snorkels out of plastic tubing from their suits, before going out. The snorkels will be used in case water starts building up in their helmets. They also put absorbent pads in their helmets; the pads were launched from Earth following the July scare.
Besides the two Americans, three Russians and one Japanese are living on the space station, all men.