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Astronauts prepare ammonia-tank swap

CAPE CANAVERAL, Fla. —A pair of spacewalking astronauts disconnected an old empty ammonia tank outside the International Space Station on Friday and got a new one ready to put in its place.

In the first of three spacewalks needed to complete the job, Clayton Anderson had no problem taking apart the ammonia lines on the old tank. But he needed a pry bar to remove the new tank out of space shuttle Discovery's payload bay. The tank got hung up on a bolt.

"Go nice and easy, Clay," spacewalking partner Rick Mastracchio warned as Anderson pushed and prodded with the pry bar. After several tries, the tank finally came free. "We got it!" Anderson called out.

The two men lifted the 1,700-pound tank out of Discovery and handed it off to a robot arm, which maneuvered it to a temporary storage location at the space station.

The actual swap-out of the two tanks will take place during the second spacewalk, on Sunday, with the entire effort wrapping up on Tuesday, the third and final outing. It will be "a big juggle" with the tanks, said David Coan, Mission Control's lead spacewalk officer.

As the spacewalk drew to a successful close, Mastracchio noted there was lot more distance to cover, moving hand over hand, than the last time he worked on the space station, in 2007. The orbiting outpost has grown considerably since then.

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