Mon, May 13, 2013 - Page 7 News List

NASA astronauts end spacewalk to fix leak


In a still image taken from NASA TV, International Space Station astronauts Chris Cassidy, top, and Tom Marshburn finish work on repairs on Saturday.

Photo: AFP / NASA TV

NASA astronauts performed an emergency spacewalk on Saturday to halt an ammonia leak on the International Space Station (ISS), but it will take weeks or months to determine whether the problem has been permanently fixed.

The spacewalk was successfully completed an hour ahead of schedule at 6:14pm GMT, five-and-a-half hours after flight engineers Tom Marshburn and Chris Cassidy ventured outside the ISS.

During the maneuver, Marshburn and Cassidy attached a spare pump and flow control sub assembly box to replace the one suspected to be the source of an ammonia leak that affected the US segment of the orbiting laboratory on Thursday.

Ammonia is used to cool the station’s power system.

The new pump was turned on about an hour later, and after about 30 minutes of careful observation by the astronauts and mission control, ISS commander Chris Hadfield of Canada tweeted: “No leaks! We’re bringing Tom & Chris back inside.”

Although the pump will continue to be observed through instruments, the early indications were positive that “we have climbed a big mountain on solving the ammonia leak,” a commentator at mission control said on NASA television.

ISS flight director Joel Montalbano later told a press briefing the astronauts had done a “fantastic job.”

“We’re very happy, we didn’t see any sign of leaks, but it’s going to take weeks to see if we did in fact stop the leak,” Montalbano said.

Asked to put a timescale on when officials could be certain that the problem had been repaired, Montalbano said that it could take several weeks.

“I expect it will take four weeks or five weeks, possibly longer before we have a real 100 percent characterization,” he said. “Weeks or months, it’s too early to tell you, but it’s going to take some time.”

Officials said that the emergency spacewalk had set a precedent because it was conducted at such short notice.

It was the 168th excursion in support of the orbiting laboratory and the fourth for both Marshburn and Cassidy, who have worked together before.

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