NASA delays final fix to International Space Station after initial spacewalk

NASA is delaying final repairs to the International Space Station after an astronaut's suit was compromised on a spacewalk.

Astronauts on spacewalk to fix station

NASA is delaying final repairs to the International Space Station after an astronaut's suit was compromised on a spacewalk.

US astronauts Rick Mastracchio and Michael Hopkins successfully removed a faulty pump on the international Space Station on Saturday.

At least one more spacewalk is needed to install a fresh spare.

Several hours after the pump was removed, NASA pushed the second spacewalk from Monday to Tuesday - Christmas Eve - to size a new suit for Mastracchio.

At the end of Saturday's spacewalk, Mastracchio's suit was compromised when he inadvertently turned on a water switch. He wasn't in any danger, but mission control decided to switch to a backup suit.

It was Mastracchio's seventh career spacewalk, and the first for Hopkins.

Japanese astronaut Koichi Wakata led the mission from inside the station, operating the station's 15-metre robotic arm, hoisting Mastracchio and hefty equipment from one section of the lab to another.

The men's first task was to disconnect the failed ammonia pump, which is about the size of a refrigerator.

Here's a good look at the degraded pump module from the helmet cam of Rick Mastracchio during today's #spacewalk: pic.twitter.com/6MnKpnNbTx

— NASA (@NASA) December 21, 2013

On the second spacewalk, now set for Tuesday, the astronauts are to remove the pump so it can be replaced with a spare that was already stowed at the ISS.

A third spacewalk is planned for Christmas Day, when the failed pump will be shuttled away and final installations made on its replacement.

However, there is a chance the astronauts will be able to complete all their work in two spacewalks, NASA has said.

NASA's @AstroRM & @AstroIllini turn spacesuit battery power on @ 7:01a ET, marking the start of today's #spacewalk pic.twitter.com/sVABMlphlg

— NASA (@NASA) December 21, 2013

If not, the Christmas Day outing would be the first since 1974, when a pair of NASA astronauts "stepped outside the Skylab space station to retrieve film from a telescope and photograph Comet Kohoutek," the US space agency said.

The urgent spacewalks were called for this week due to a faulty valve that caused a partial shutdown in the system that regulates equipment temperature at the space station.

Engineers tried to fix the problem from the ground, but eventually decided they needed to replace the ammonia pump.

The six-man crew was never in danger, but NASA wanted to repair the problem sooner rather than later, agency officials said.

The spacewalks meant the first regular commercial cargo supply mission by Orbital Sciences' Cygnus craft, which had been planned for earlier in the week, was postponed. It will now fly no earlier than January 7.

NASA also had to rig up some last-minute contingency gear inside the US-made spacesuits, which have not been used since a helmet water leak nearly drowned a European astronaut in July.

Now the helmets carry an extra absorption pad and a snorkel inside, just in case.

The investigation into the cause of the helmet leak is ongoing. Hopkins will be wearing the suit that had the problem, though its inner water pump has been replaced.

#Exp38 Wakata & Kotov prep for the #spacewalk in the Quest airlock w suited crew behind them ready for depress: pic.twitter.com/z2GjEVMRmM

— NASA (@NASA) December 21, 2013

During the initial walk, NASA said it would check with the astronauts throughout the day to make sure they were not feeling any "squishy" sensation behind their necks, which might indicate a water buildup and would cut short the spacewalk, space agency commentators said.

The first check, 31 minutes into the outing, was clear, with astronauts reporting dry conditions and no problems in the spacesuits or gloves, NASA said.

The astronauts also trained for the emergency spacewalks by watching video of a previous outing to replace an ammonia pump in 2010.

With each astronaut sporting a helmet camera, NASA TV showed the operations in real-time from the perspective of the spacewalkers.