Shuttle gear shift adds a day

Checks of the clogged solar wing controls will prolong the mission.

CAPE CANAVERAL - NASA asked its orbiting astronauts Monday to take a closer look at the gears that control the international space station's solar wings to try to find out what's grinding inside and causing steel chips to clog the system. The impromptu work - "exploratory surgery," as the station's program manager calls it - will keep the shuttle Discovery in orbit an extra day.

During a space walk today, astronaut Scott Parazynski will inspect a good rotary joint that turns the space station's left set of solar wings toward the sun. NASA wants to see what a perfectly running unit looks like to compare it to the one that is acting up on the opposite side.

On Sunday, space walker Daniel Tani found black dust that resembled metal shavings inside the motorized joint that controls the right set of solar wings. It was instantly apparent to him something was wrong, he said Monday. The dust was everywhere, and the spinning mechanism was not shiny and clean like it should have been for something launched just four months ago, Tani said.

At least some of the shavings are steel and could be from the bearings inside the joint, said Mike Suffredini, NASA's space station program manager.

At Suffredini's request, shuttle mission managers approved a more detailed inspection of the troublesome right joint. The time-consuming work will be conducted Thursday during the fourth space walk planned for Discovery's construction mission.

Discovery's commander, Pamela Melroy, said it's tough for the astronauts to make big changes like this. "There's a lot of choreography that goes into a space walk. We like to practice them and mentally rehearse them many, many times," Melroy said. But she said her crew was ready to tackle the job.

Today's inspection of the good left gear will take up just a small portion of the space walk. The primary goal will be to hook up a giant beam and its attached solar panels to their new location on the space station. These panels, once unfurled, will be controlled by the left rotary joint.

Installing that beam and extending those solar panels to their full 240 feet has taken on added importance because of the rotary joint problem. A significant power shortfall would delay the arrival of European and Japanese laboratories on the verge of launching.

Discovery is now set to undock from the space station on Monday and return to Earth Nov. 7.

[Last modified October 30, 2007, 00:27:05]