Spacewalkers to tackle ripped solar wing

CAPE CANAVERAL, Florida (Reuters) - NASA sketched out plans on Wednesday for a hastily choreographed spacewalk with an astronaut dangling at the end of an extension boom to try to save a critical power wing of the International Space Station.

The job, targeted for Friday, will fall to veteran spacewalker Scott Parazynski, who will try to install a makeshift bracket to take the load off hinges that broke while the 110-foot (33-metre) solar power panel was being extended on Tuesday.

The panel is attached to an 18-ton truss that was moved to the far end of the station's frame. It tore as it neared the end of its 110-foot extension.

"One of the agonies was how do we get to the work site," NASA's space station program manager Mike Suffredini told reporters.

The answer, engineers hope, will be the 50-foot (15-metre) extension boom NASA added to the space shuttle's regular cargo after the 2003 Columbia accident. The boom doubles the length of the shuttle's robot arm so it can inspect the ship's heat shield for damage prior to its return through the atmosphere for landing.

But the boom has proved handy for putting spacewalkers in hard-to-reach areas for minor repairs on the shuttle.

NASA will attempt to use the boom on the station's robotic crane to place Parazynski within arm's reach of the station's tattered wing.

Fixing the panel has become the primary goal for the rest of the shuttle's 15-day mission, which had already been extended for an unplanned spacewalk to inspect a contaminated joint that rotates another pair of solar arrays to track the sun for power.

That problem has now been left for future shuttle crews to tackle, Suffredini said.

NASA needs to stabilize the broken wing before any more modules can be added to the growing outpost. The point of Discovery's mission was to deliver a vestibule with docking ports for Europe's Columbus laboratory and Japan's three-part Kibo complex.

"I don't know enough (about the damaged panel) to say that I won't damage it (more) if I leave it in this configuration," Suffredini said.

A spacewalk as complex as the one NASA envisions would typically take weeks to prepare. Engineers at the Johnson Space Center in Houston are working in three shifts around-the-clock to plan the outing by Friday. If the work isn't finished, the spacewalk would be put off until Saturday and the shuttle's departure from the station delayed until Tuesday.

NASA is eager to send Discovery home so the space station crew can prepare Harmony to support Columbus' arrival in early December. The schedule between Discovery's departure and Columbus' arrival already was filled with tasks.

NASA has between December 6 and 13 to launch Columbus aboard the shuttle Atlantis before the end of the year due to the angle of the sun and the shuttle's thermal requirements for staying in orbit at the station.

During the spacewalk, Parazynski must take special care not to touch the powered solar wing in order to avoid getting shocked. He will use specially wrapped tools.

The panels are coated and should not pose a safety threat, but NASA does not know the condition of the wing because it has been operating in the harsh space environment for seven years.

If the repair is successful, NASA plans to clear the shuttle for undocking on Monday and landing at the Kennedy Space Center in Florida on Wednesday.

NASA is trying to finish building the $100 billion station, a project of 16 member nations, before 2010, when the shuttle fleet is to be retired.