Published: November 22, 2008 05:54 pm         

Astronauts step out for longest, hardest spacewalk

CAPE CANAVERAL, Fla. — Astronauts stepped out for the longest and hardest spacewalk of their mission Saturday to wrap up greasy repair work on a gummed-up joint at the international space station.

As spacewalk No. 3 was getting under way, a new recycling system for converting urine into drinking water broke down again.

It was the third day in a row that the urine processor inexplicably shut down, and it appeared to be the same kind of sluggish motor trouble seen before. Engineers on the ground scrambled to figure out what might be wrong; the problem could jeopardize NASA’s plan to return recycled water to Earth aboard space shuttle Endeavour next weekend.

The $154 million water recycling system, delivered a week ago by space shuttle Endeavour, is essential for allowing more astronauts to live on the space station next year.

Saturday’s spacewalk by Heidemarie Stefanyshyn-Piper and Stephen Bowen focused entirely on the clogged solar wing-rotating joint. The joint stopped working properly more than a year ago, after it became jammed with metal grit from grinding parts, and cannot keep the solar wings on the right side of the space station pointed toward the sun.

The astronauts got started on the unprecedented clean and lube job — and bearing replacements — on Tuesday.

NASA expected Saturday’s spacewalk repairs to last at least seven hours. The astronauts were running ahead, though, as the spacewalk hit the halfway point. Any chores left undone could be squeezed into the fourth and final spacewalk of the mission Monday. That’s when astronauts are supposed to grease up the good rotary joint on the left side of the orbiting complex.