Article Posted on : - Dec 25, 2013

NASA astronaut Rick Mastracchio participates in the first Expedition 38 spacewalk designed to troubleshoot a faulty coolant pump on the International Space Station. A NASA photo

WASHINGTON (AFP): Two NASA astronauts wrapped up successful repairs at the International Space Station Tuesday after a rare Christmas Eve spacewalk to fix an equipment cooling system.

Americans Rick Mastracchio, 53, and Mike Hopkins, 44, floated outside the orbiting lab for seven and a half hours to replace an ammonia pump whose internal control valve failed on December 11.

"We have a pump that is alive and well," said a NASA commentator on the US space agency's live television feed after a successful jumpstart test on the newly installed pump module, a bulky piece of gear the size of a refrigerator.

Despite recent concerns about leaking spacesuits, neither astronaut reported any problems.

The suits "have functioned perfectly and have been bone dry throughout the course of today's spacewalk," a NASA commentator said.

Hopkins, making his second career spacewalk, rode the 15-metre robotic arm, operated from inside the station by Japanese astronaut Koichi Wakata.

With his boots affixed to the Canadian-made arm, Hopkins grasped the bulky pump module as Wakata manoeuvred him over to its installation location.

Then, Mastracchio, who was making his eighth career spacewalk, helped push the module into its slot and the pair began affixing it in place.

Five electrical connections and four fluid connections followed, and a brief test, like a jumpstart, was done to test the pump's connections and electronics.

The team made swift work of the first spacewalk on Saturday, disconnecting and pulling out the old cooling pump that regulates the temperature of equipment at the orbiting space lab.

They managed to complete what had been seen as almost two days' worth of work in a single outing that lasted just five and a half hours.

Orchestrating the spacewalks from inside the station's Destiny laboratory was Wakata of the Japan Aerospace Exploration Agency.