A spacewalking astronaut gently pulled two potentially dangerous strips of protruding filler from Discovery‘s tile belly with his gloved hand on Wednesday, successfully completing an unprecedented emergency repair.
Astronaut Stephen Robinson said both pieces came out easily during the spacewalk, which lasted just less than six hours. He did not have to use a makeshift hacksaw put together in orbit that he took along just in case.
”That came out very easily, probably even less force,” Robinson said of the second piece. ”I don’t see any more gap filler … I’m doing my own inspection here. It is a very nice orbital belly.”
Nasa officials had determined that the exposed ceramic-fibre fillers could lead to overheating and a possible repeat of Columbia‘s disastrous re-entry.
Robinson attached a special foot restraint to the space station’s 17,7m robotic arm and fellow astronauts aboard the station manoeuvred the arm so Robinson could reach the shuttle’s belly. They were careful to make sure Robinson’s helmet and feet did not contact the fragile ship.
It was the first time an astronaut had ventured beneath the ship.
Robinson took only the essential tools for the repair — leaving a tile-repair kit just outside the airlock. He also secured his safety tethers between his legs and behind him to keep from accidentally striking the vehicle.
Once under Discovery‘s belly, Robinson expected to spend about an hour removing or trimming the fillers from two locations near the shuttle’s nose. But it took mere seconds for him to pull out each strip.
His spacewalking partner, Soichi Noguchi, kept a close eye on Robinson and was set to communicate with astronauts aboard the orbiting complex if Robinson’s communication system failed.
”Steve, we trained for four years, you’re going to spend the next four years signing autographs,” Noguchi told Robinson once the repairs were complete.
Those who watched from space and on the ground were fascinated by the never-before-seen views.
”Steve, could you move your hand out of the field of view?” astronaut Andrew Thomas radioed Robinson, who had a camera attached to his helmet. ”We were enjoying the view as much as you were.”
Nasa thought the first gap filler was the trickier of the two.
They believed it remained glued to a shim that was bonded to a thermal tile.
There are 24 300 glass-coated tiles on the shuttle, a majority of them on its belly. The tiles protect the shuttle from the extreme temperatures in orbit and, more importantly, insulate the ship during launch and re-entry.
The filler material protects the tiles from bumping against one another during launch, but isn’t needed for landing because of the difference in the airflow.
Once the work was complete, Thomas requested the spacewalkers return to the shuttle and cut short the expected seven-hour orbital outing. He said it had been a long day.
Robinson, however, urged mission control to let him take a picture from beneath the shuttle before the station’s arm brought him back up.
”You guys are going to be happy I had a camera,” Robinson said. ”It is so beautiful to see the orbiter against the Earth at these angles.”
An astronaut in mission control told Robinson the photo sounded nice.
”I think the team down here would like an autographed copy when you get back,” Michael Massimino radioed from the Houston control centre. ”You guys did a great job. Congratulations.”
As the spacewalkers returned to the airlock, those aboard the shuttle made plans with mission control to use Discovery‘s robotic arm to inspect a thermal blanket below the commander’s window that was ripped during launch, possibly by debris.
Deputy shuttle programme manager Wayne Hale hinted late on Tuesday that the astronauts may have another repair job ahead of them before their mission ends. It would come during a fourth unplanned spacewalk.
Hale said there is concern that the blanket might come off during re-entry and smack into the shuttle. He said engineers were in the process of assessing whether something needed to be done to the blanket, which was opened and puffed up by air during launch.
Before Robinson began the filler repair on Wednesday, he and Noguchi spent about two hours installing an external tool and parts platform on the International Space Station, where Discovery has been docked since Thursday.
The platform’s installation was the key task of the mission’s third spacewalk until Nasa officials determined the exposed fillers could threaten Discovery‘s re-entry.
Columbia broke apart over Texas in 2003 as its crew returned to Earth from a 16-day mission. The disaster was blamed on a chunk of foam that fell from the external tank during lift-off and tore a hole in one of spacecraft’s wings. All seven astronauts died.
Discovery, set to land on Monday, is the first shuttle to return to orbit since the tragedy. New damage surveys developed in Columbia‘s aftermath detected the drooping material on Discovery.
”That was the ride of the century,” Robinson told astronaut James Kelly, who operated the station’s arm during the filler repair. ”Very nice job.” — Sapa-AP