Shuttle astronauts have backyard-mechanic woes

HOUSTON, Sep 13 (Reuters) Astronauts working on the International Space Station had troubles today familiar to any backyard mechanic on Earth -- a lost bolt and a broken tool.

During the second spacewalk of a mission critical to completion of the half-finished Space Station, Shuttle Atlantis crew members Dan Burbank and Steve MacLean worked on a solar-power unit that was attached to the station the day before.

In the process, MacLean lost a bolt somewhere in space that prompted a worried radio call from Mission Control about whether it might have gone into a rotating joint that will move the solar panels to catch the sunlight.

''We just want to confirm from Steve that he does not think that bolt is likely to have gone into structure,'' Mission Control radioed from Johnson Space Center in Houston.

MacLean's explanation indicated he thought the bolt had been off to the side of the joint when it disappeared, and would not cause harm.

Later, MacLean also broke a tool he was working with and had to gather the broken parts before they drifted away.

The 17-1/2 tonne, 372 million dollar solar unit was the first addition to the space station in nearly four years after the 2003 Columbia disaster forced NASA to ground the shuttle program and thus halt construction of the 100 billion dollar complex.

It consists of a 45-foot-long truss structure which holds solar energy panels that will be unfolded to their full 240-foot length tommorow.

Burbank and MacLean, a Canadian astronaut, spent most of their spacewalk releasing restraints placed on the rotating joint to protect it while Atlantis carried it to the station after launching on Saturday from Florida.

SPACEWALK HICCUP After they finish, Mission Control will send up commands to put the joint through a series of tests.

On the mission's first spacewalk yesterday, Joe Tanner and Heidemarie Stefanyshyn-Piper hooked up 17 power, data and fluid lines to bring the unit to life.

They will go into space again on Friday to continue installation of the unit and perform a few other tasks.

Tanner also lost a bolt yesterday. Even though NASA managers insisted it had floated harmlessly away, he was still concerned about it today and told MacLean, ''keep an eye out for a stray bolt.'' NASA managers said yesterday that post-launch inspections of Atlantis' heat shield had turned up no damage and the spacecraft is cleared for its scheduled return to Earth on September 20.

Columbia fell apart as it came back to Earth on Febuary 1, 2003 after it was struck by debris at launch that cracked its heat shield.

NASA spent more than a 1 billion dollars and 3-1/2 years fixing the shuttle so it could resume assembly of the station.

At least 14 more shuttle flights are planned to finish the station before the aging shuttle fleet is retired in 2010.

REUTERS PB RN1854