Two astronauts floated outside the international space station Wednesday to help fold up an old solar wing and try to bring to life a rotating joint that will allow a new pair of solar arrays to track the sun.
Space shuttle Atlantis astronauts Patrick Forrester and Steve Swanson spent the first two hours of what was ultimately a seven-hour-plus spacewalk helping to put the 115-foot (35-meter) solar wing away in its storage box.
Even before the walk started, astronauts began retracting the old wing's 31½ sections by computer command.
Using specially designed tools, including one that looks like a hockey stick, the spacewalkers loosened and nudged panels on the solar wing that hadn't properly folded earlier in the day. Shuttle astronauts then resumed retracting the array, ending the day with 13 sections folded up.
"We're going to call it quits on this part of your job for today. Excellent job," astronaut James Reilly told the spacewalkers.
NASA hopes to finish folding up the solar wing Thursday. The wing's retraction appeared to go fairly smoothly on Wednesday.
Before the spacewalk, when it looked as if the solar panels were starting to bunch up or fold backward, Mission Control periodically wiggled the array by remote control to loosen guide wires and grommets, the metal eyelets through which guide wires run.
The folding of a similar 115-foot solar array during a December shuttle mission was more problematic, because guide wires got stuck on grommets.
Tracking the sun
The solar wing needs to be folded up so that the new set of solar panels, delivered to the space station this week, can follow the sun to generate electrical power for the orbiting outpost. The new array was unfolded Tuesday after being attached to the space station the day before.
After the spacewalkers finished up with the old solar panels, they turned their attention to the rotating joint for the new array, known as the Solar Alpha Rotary Joint or SARJ. The automobile-sized joint is what enables the array to track the sun.
The astronauts started unhooking restraints to allow the joint to move — but they finished the spacewalk before the joint was ready to rotate, because it wasn't properly responding to remote commands from Mission Control. Astronauts will have to finish the task on another spacewalk.
Blanket repair set for Friday
Back on the ground, NASA engineers figured out how best to repair a loose thermal protection blanket on the shuttle that peeled back during launch last week. Repairs are scheduled for Friday.
The astronauts will secure the blanket using staples found in the shuttle's medical kit and pins that come from the shuttle's tile repair kit. If those methods don't work, NASA flight controllers will have the astronauts sew it into place using a stainless steel wire and an instrument that resembles a small needle.
Engineers don't think the damaged section of the thermal blanket, which protects part of the shuttle from the blazing heat of re-entry, would endanger the spacecraft during landing. But it could cause enough damage to require schedule-busting repairs.
Since shuttle damage resulted in the 2003 Columbia disaster that killed seven astronauts, NASA has greatly focused on any problems that could jeopardize a shuttle's re-entry.
Meanwhile, a union representing 570 space shuttle program workers at Kennedy Space Center planned to strike after contract negotiations broke down Wednesday, union spokesman Bob Wood said.
A strike date has not been set, but a strike would not affect the shuttle mission, he said. A handful of union members who help at landing sites would report to their jobs and then strike.
The union, the International Association of Machinist and Aerospace Workers, and the company, United Space Alliance, would not say what the sticking points were.
This report was supplemented by MSNBC.com.
