Space Centre, Houston - Discovery's astronauts are preparing for a high-stakes task that's never before been attempted: sending a spacewalker beneath the craft to repair filler sticking out from the ship's thermal tile belly.
On Wednesday, the agency will put astronaut Stephen Robinson on the space station's 18m robotic arm as part of an unrehearsed maneuver. The arm will be operated by astronauts inside the station, who will bend and wrap Robinson around so he can reach the shuttle's belly. Once there, he'll tug out the ceramic-fabric filler with his gloved hands. If that doesn't work, he'll cut away the material, which is sticking out by about 2,5cm from two spots near Discovery's nose.
Deputy shuttle program manager Wayne Hale says if the proposed methods don't work, there will likely be some head-scratching for a day. However, he says the agency will find another method and try the repair again on Thursday or Friday, informs Independent.
“Like most types of repairs, it's conceptually very simple, but this has to be done very carefully - the tiles are very fragile,” Robinson said today in a live press conference from the shuttle. “'m pretty comfortable with using tools very carefully. We'll use the hacksaw only if necessary.”
Pictures taken by the space station crew as Discovery docked revealed that two pieces of fabric on the craft's underside are protruding by 1.1 inches (2.8 centimeters) and 0.6 inches. The “gap-filler,” composed of coated Nextel fabric, allows heat- shield tiles to expand in higher temperatures.
While studies of shuttles that have landed after re-entry in the past revealed protrusions, any fabric sticking out more than 1/4 of an inch might be a problem, NASA spokesman Pat Ryan said on Monday, reports Bloomberg.
According to The New York Times, earlier on Monday, astronauts on the mission's second spacewalk successfully replaced a failed gyroscope on the space station, giving the outpost a full set of stabilizers for the first time in three years.
The astronauts, Dr. Robinson and Soichi Noguchi, spent 7 hours and 14 minutes in space, 45 minutes longer than scheduled because they completed extra tasks to get ahead of schedule for Wednesday's outing.
Their return to the Discovery, at 11:56 a.m. Eastern time, was briefly delayed by latch problems on the airlock.
The astronauts removed the 660-pound gyroscope, which failed in 2002, and replaced it with one taken up in the Discovery's cargo bay. Mr. Noguchi rode on the end of a robot arm to transport them. After attaching the new gyroscope and connecting it electrically, mission control asked the astronauts to go back and check the connections because the unit was not working properly.
After reseating the cables, ground controllers said the unit was working properly. "The space station now has four working control moment gyros," mission control said. "Congratulations."
The station has four gyroscopes to stabilize and orient the laboratory in space without using scarce rocket fuel. It has been operating with only two for months, the minimum number, because of the dead unit that was replaced and an electrical problem with another.
During the mission's first spacewalk, on Saturday, Dr. Robinson rerouted cables around a bad circuit breaker and restored the third unit.