Astronauts take 1st spacewalk of shuttle mission

By MARCIA DUNN, AP Aerospace Writer

CAPE CANAVERAL, Fla. – Two 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.

It was the first of three spacewalks planned for Rick Mastracchio and Clayton Anderson, members of space shuttle Discovery's visiting crew.

"Remember, space is like chocolate. Go get a big bite," astronaut Dorothy Metcalf-Lindenburger radioed from inside as the spacewalkers floated out.

Anderson quickly disconnected the old tank's ammonia lines, noting with relief that nothing leaked out.

Next, Mastracchio unbolted the new tank in Discovery's payload bay, so that he and Anderson could lift it out and hand it over to a robot arm. The actual swap-out of the two tanks was going to take place during the second spacewalk Sunday, with the entire job finally wrapping up on the third outing Tuesday.

"OK, Clay, very, very slow as you know," Mastracchio told Anderson as they gently hoisted the new 1,700-pound tank. The tank got hung up on a bolt, and Anderson tried to free it with a pry bar. "Go nice and easy, Clay," Mastracchio urged.

Anderson yanked several times with the pry bar and still the tank was stuck. "We got it!" he called out when the tank finally came free.

Earlier, there were a few tense moments when Mastracchio reported that he bumped a large V-shaped bar in the shuttle payload bay and it was sliding around. He said it did not appear to be off its mooring. Mission Control later said engineers were "pretty convinced" it was normal for the clamp to move around a little, but just to be safe, warned the spacewalkers to stay away from it.

The V-shaped bar serves as a guide for the cargo carrier that flew up on Discovery and was attached to the space station Thursday. The compartment was unloaded by some of the 11 astronauts inside, as the spacewalk unfolded 215 miles up.

Besides the tank replacement job, Mastracchio and Anderson had to collect a science experiment from the front porch of the space station's Japanese lab and replace a failed station-positioning device.

Mastracchio and Anderson were supposed to do some battery work on the far left end of the space station, along the sprawling power truss. But NASA canceled the task this week because of concern the two might get shocked. The work instead will be carried out on the next shuttle flight, once the spacesuits are better protected.

Discovery and its crew of seven are supposed to remain at the space station until next Friday. But they likely will spend an extra day there because of the failure of the shuttle's main antenna. NASA wants the shuttle astronauts to inspect their ship for any signs of micrometeorite damage before they depart. That way, all the laser images can be transmitted to Mission Control through the station.

That would stretch the shuttle mission to 14 days, with a landing on April 19.

Late Thursday, Mission Control informed the astronauts that the shuttle seems to have weathered Monday's liftoff well and that there is no need for another inspection to check for launch damage. The survey that's planned before Discovery undocks will be looking for any potentially dangerous impacts from space junk.

Only three shuttle missions remain after this one to wrap up space station construction.