Astronauts hope to tackle one of "big 14" repairs on Friday

NASA has decided to wait until Friday morning to perform a spacewalk described as one of the “Big 14” repair jobs on the International Space Station.

Managers had been targeting Thursday for U.S. astronauts Doug Wheelock and Tracy Caldwell Dyson to replace a failed ammonia pump module that has knocked out half of the station's coolant system.

But that timeline was considered "very aggressive," a flight director said today, and ultimately it was pushed back a day.

The failure of a coolant system pump last weekend forced the station’s six residents to power down various systems and limit science research to prevent overheating.

The situation poses no immediate danger, but life support systems might only last a matter of days if another failure took out the second of two independent ammonia coolant loops.

“Today we’re in fine shape,” said Mike Suffredini, NASA’s space station program manager. “We’re just trying to make sure we get the (spacewalk) done before we suffer the next failure in the system.”

The job will require at least two spacewalks, each lasting roughly six hours, with the second possible as soon as Sunday.

Read the rest of the story in Tuesday's FLORIDA TODAY.

IMAGE: At Johnson Space Center in Houston on Monday, astronauts Sunita Williams and Catherine Coleman practiced spacewalk procedures in a giant swimming pool to help choreograph the job for station astronauts Doug Wheelock and Tracy Caldwell Dyson. Credit: NASA TV.