NASA Delays Critical Space Station Repairs to Saturday

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The International Space Station is featured in this image photographed by an STS-130 crew member on space shuttle Endeavour after the station and shuttle began their post-undocking relative separation. (Image credit: NASA)

NASA has delayed two spacewalks to fix a major coolingsystem failure on the International Space Station for the second time, pushingthe start of the vital repairs to no earlier than Saturday.

American astronauts Douglas Wheelock and Tracy CaldwellDyson were planning to perform the first spacewalk Friday to replace a failedammonia pump on the station's right side. That spacewalk ? which was alreadydelayed one day ? will now begin Saturday at about 7 a.m. EDT (1100 GMT),with the second spacewalk set for no earlier than next Wednesday, Aug. 11.

Mission Control radioed the spacewalk delay news to the stationcrew Thursday morning.

"Thank you for the word," Wheelock told MissionControl. "Thanks for the hard work. We know people are still workingthrough the evening, and through the night, and we appreciate it."

The delays give NASA mission planners more time to finishrefining the procedures and safety concerns for the pump repair spacewalks,NASA officials said. [Graphic:Space Station's Cooling System Problem Explained]

"What's really being done now is putting on thefinal touches," said NASA spokesperson Kyle Herring during televisedstation mission commentary.

The space station's cooling system troubles began July31, when a power spike tripped a circuit breaker that shut down one of two pumpsthat push liquid ammonia through the orbiting laboratory's cooling system. Attemptsto reactivate the stricken pump were unsuccessful.

The failure forced astronauts to turn off many systems onthe space station's U.S. segment and shut down the backup systems for some othersto reduce the amount of heat generated by equipment. ?The space station'sworking pump is currently operating normally to cool the systems left online.

NASA has repeatedly stressed that the space station crewis in no danger from the malfunction.

But mission managers do want to repair the cooling systempump swiftly in order to restore the space station to full operations.Astronauts on Earth have been practicingthe spacewalk repair to help Wheelock and Caldwell Dyson prepare for theirorbital work.

The malfunction is a major system failure and one of 14that NASA has prepared repair plans for on the off chance it ever occurred.There are four spare ammonia pumps currently stored on platforms on thestation's exterior.

The pumps are not small. They are bulky and are expectedto be difficult to maneuver in the weightlessness of space.

Caldwell Dyson has said the pumps are about as large as alaundry dryer.

Each pump weighs 780 pounds (353 kg) and is 5 1/2 feetlong (69 inches) by 4 feet wide (50 inches). They are about 3 feet tall (36inches).

The InternationalSpace Station is currently home to six people; three Americans and threeRussians.

NASA will broadcast the International SpaceStation spacewalk repairs live from space on NASA TV, with the first spacewalkslated to begin Saturday at 7 a.m. EDT.

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Tariq Malik

Tariq is the Editor-in-Chief of and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.