Shuttle astronauts go out for second spacewalk

HOUSTON, Sep 13: Two astronauts ventured out of the International Space Station on Wednesday for the second spacewalk of a shuttle mission critical to completion of the half-finished orbital outpost.

Shuttle Atlantis crew members Dan Burbank and Steve MacLean were to spend six hours working on a solar power unit that was attached to the station yesterday and will double its electricity supply when activated.

''A great day out there,'' Burbank said as he floated out into the bright daylight of space. ''Boy, that is pretty. Not something you see every day.'' The 17-1/2 tonne, 372 million dollars 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 dollars 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.

The unit includes a large rotating joint -- the Solar Alpha Rotary Joint, or SARJ, in NASA lexicon -- that will move the solar arrays to catch the energy-generating sunlight as the station moves through its orbit about 220 miles above the earth.

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

TESTS PLANNED 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.

The only spacewalk hiccup so far came yesterday when Tanner lost a bolt that skipped across the truss and out of sight.

He worried that it might damage the new unit and, even though NASA managers insisted it had floated harmlessly away, was still concerned about it today.

''If that missing bolt is anywhere it would be around (the) cover 18, 19 area. So keep an eye out for a stray bolt,'' he told MacLean.

''Okay, copy will do,'' his crewmate responded.

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