The shuttle Discovery's spacewalkers made a fix to the international space station's rail transporter Saturday and tried out a extension boom that could be used to make repairs to the shuttle.
While perched on the boom, one of the astronauts said he felt like "a bug on the end of a fishing rod," but the initial reviews were generally positive.
The boom's performance "was above and beyond" what engineers expected, flight director Tony Ceccacci told reporters after the 7½-hour spacewalk ended. "Hopefully, we'll never have to use it, but we know we have the capability."
Saturday's outing, conducted in orbit 220 miles (350 kilometers) above Earth, was the first spacewalk for Mike Fossum and the fourth for Piers Sellers. It was also the first of three spacewalks scheduled during Discovery's 13-day mission.
“Enjoy the view, gentlemen!” NASA communicator Megan McArthur said from Houston as the spacewalk began.
That they did. At one point, Sellers was told to look down at Ireland and Britain. "Oh, good heavens ... oh, my goodness," the British-born Sellers said in reply. "It's a beautiful day in Ireland."
Later, Fossum marveled over a view of the Caspian Sea. "I'm in a dream — nobody wake me up," he said.
The spacewalkers quickly dispatched their first task, immobilizing a cable cutter on the station’s mobile transporter, or railroad car, and rerouting a cable through it. A duplicate cable cutter accidentally cut a cable leading to the transporter late last year, and NASA wanted to make sure it doesn’t happen again because the cable is a conduit for power, data and video images.
The transporter moves along the space station and is used for constructing the complex. After the backup cable was rerouted, NASA engineers on the ground reported that the rail car was operational again. The cable that was severed last year will be replaced during a second spacewalk set for Monday.
Bouncing on the boom
The spacewalkers then started testing whether the robotic boom, with astronauts attached at the end, could be used for inspecting or making repairs on the shuttle. NASA mission commentator Kelly Humphreys compared the contraption to a crane or "cherry picker" that could be moved to otherwise-hard-to-reach areas on the shuttle's underside.
During Saturday's practice session, the spacewalkers didn't come anywhere near the shuttle's belly. Instead, they merely simulated repair-related movements while at the end of the 50-foot (15-meter) extension boom, which was attached to the shuttle’s 50-foot robotic arm.
The boom exhibited a bit of springiness as Sellers went through an initial round of motions — twisting around, lying backward, leaning forward and getting in and out of the foot restraints. "It gets easier as you go along, doing all these tasks on the end of a skinny little pole," Sellers said.
After the initial tryout, the boom maneuvered into a position that was more precarious, and Fossum joined Sellers at the end. Then the spacewalkers were brought up next to the space station's truss structure to measure the pushes and pulls they might experience during an actual repair operation.
The sensation has been compared to trying to paint a house on a rickety ladder, and Fossum said one of the practice moves resulted in "too much motion to handle." But the other maneuvers were doable, he and Sellers said.
Throughout the test, the spacewalkers were attached by a long safety tether to the shuttle's robotic arm, to guarantee that they wouldn't float away from the work site.
"I feel like a bug on the end of a fishing rod out here," Sellers commented. "I know, ain't it the truth?" Fossum answered.
NASA developed the boom-mounted platform to make sure there is never a repeat of the Columbia disaster, which killed seven astronauts in 2003. Foam from the shuttle’s external tank struck Columbia’s wing during launch, creating a breach that allowed fiery gases to penetrate the shuttle during the return flight to Earth.
Fossum and Sellers may get a chance to use the boom for a real repair on their third spacewalk, now scheduled for next Wednesday. NASA managers are evaluating whether a piece of fabric filler protruding from the thermal tiles on Discovery’s belly needs to be removed by the spacewalkers. The early consensus was that the gap filler would be all right the way it is, but orbiter project manager Steve Poulos said the final decision would be made Sunday.
Two pieces of gap filler had to be removed from Discovery’s belly during a spacewalk last year because of concerns they would cause problems during re-entry.
More pictures, less flushing
In their morning message, flight controllers told the Discovery crew that they wanted to take additional pictures of slightly damaged thermal blankets using a camera on the space station.
NASA managers do not think two of the blankets pose any problems but want to make sure the other two small blankets don’t tear off during re-entry into Earth’s atmosphere. The thermal blankets are used to protect the shuttle against searing heat during ascent and descent.
The flight controllers also had a request for the shuttle crew: Stop pouring unused drinks down the shuttle’s toilet. “An example of how closely Big Brother watches,” they wrote.
The space shuttle crew awoke Saturday to “God of Wonders,” a popular Christian music recording chosen by Fossum’s family.
“I do think it’s particularly appropriate as I prepare to step outside for about four and a half trips around this chunk of creation we call Earth,” Fossum radioed Houston.
This report includes information from MSNBC's Alan Boyle and The Associated Press.