CAPE CANAVERAL, Florida (AP) ― Astronauts removed an old space station pump Saturday, sailing through the first of a series of urgent repair spacewalks to revive a crippled cooling line.

The two Americans on the crew, Rick Mastracchio and Michael Hopkins, successfully pulled out the ammonia pump with a bad valve ― well ahead of schedule. That task had been planned for the next spacewalk, originally scheduled for Monday but now delayed until Tuesday, Christmas Eve, because of the need for a suit swap.

“An early Christmas,” observed Mission Control as Mastracchio tugged the refrigerator-size pump away from its nesting spot.

If Mastracchio and Hopkins keep up the quick work, two spacewalks may be enough to complete the installation of a spare pump and a third spacewalk will not be needed as originally anticipated.

Several hours after Saturday’s spacewalk ended, Mission Control bumped spacewalk No. 2 to Tuesday to give Mastracchio enough time to prepare a spare suit. His original suit was compromised when he inadvertently turned on a water switch in the air lock at the end of Saturday’s excursion. NASA officials said Saturday night that it’s unclear whether a third spacewalk will be needed and when it might occur, if required. A third spacewalk had been slated for Christmas Day before the latest turn of events. NASA requires a day off between spacewalks for astronaut rest.

The space station 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.

Mission Control wanted to keep the spacewalkers out even longer Saturday to get even further ahead, but a cold and uncomfortable Mastracchio requested to go back. The spacewalk ended after 5 1/2 hours, an hour short on time but satisfyingly long on content.

Earlier, Mastracchio managed to unhook all the ammonia fluid and electrical lines on the pump with relative ease, occasionally releasing a flurry of frozen ammonia flakes that brushed against his suit. 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 Italian astronaut last summer, so Saturday’s spacewalkers had snorkels in their suits and water-absorbent pads in their helmets.

To everyone’s relief, the spacewalkers remained dry while outside. But midway through the excursion, 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 extend the spacewalk to get ahead, given Mastracchio’s discomfort.

Not quite two hours later, Mastracchio had enough as he clutched the old pump. When Mission Control suggested even more get-ahead chores, he replied, “I’d like to stow this old module and kind of clean up and call it a day.” He said a couple of things were bothering him, not just temperature, and declined to elaborate when asked by Mission Control what was wrong.

Flight controllers obliged him. Once the old pump was secured to a temporary location, the spacewalkers started gathering up their tools to go in.

Adding to the excitement 418 kilometers up, a smoke alarm went off in the space station as the astronauts toiled outside. It was quickly found to be a false alarm.

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.