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. Last Updated: 07/27/2016

Astronauts Fix Gyroscope on Space Station

HOUSTON -- Two of Discovery's astronauts floated outside their spacecraft Monday with one key task: to replace a failed washing machine-sized spinning wheel, which along with three other gyroscopes, helps to steer the international space station.

Astronauts Stephen Robinson and Soichi Noguchi planned to spend 6 1/2-hours exchanging the broken 299-kilogram gyroscope, which failed in 2002, with a new one.

"Is it day or night out there?" Robinson asked minutes before the two opened the orbiting shuttle's airlock.

"Out you go," Robinson told his spacewalking partner, pushing him out of the craft. Almost two hours later, the pair removed the faltered gyroscope.

Once Discovery undocks from the station Saturday, NASA hopes to have all four gyroscopes operating simultaneously for the first time in three years.

On Sunday, NASA officials said they may consider repairing material dangling from Discovery's belly in a third spacewalk scheduled for Wednesday.

But there remains debate among engineers and others over how to handle what would be an unprecedented repair -- and whether it is even necessary.

Some engineers worry the filler that is protruding from between thermal tiles in two areas beneath the shuttle near its nose could trigger potentially treacherous overheating during re-entry.

One solution would be to pull the filler completely out or fold it back in. Another could be to cut it, said Steve Poulos, manager of the orbiter project office. Deputy shuttle program manager Wayne Hale said more technical information was needed, and the risks of causing further damage by going underneath the shuttle need to be considered.

"We certainly don't want to make the situation worse than it is," he said. "My immediate knee-jerk reaction was that we can live with this. On the other hand, this is bigger than we have seen before."

In 24 years of shuttle flight, astronauts have never ventured beneath their spacecraft in orbit and have made few repairs to their ship.