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Tuesday, March 18, 2008

Installing maintenance robot finished to the space station

Endeavour mission specialists Richard Linnehan and Michael Foreman (top center) installed a mechanical arm to the Canadian-built robot Dextre yesterday outside the International Space Station during the second of five planned spacewalks.

24hoursnews- Two astronauts Tuesday completed the third spacewalk of the latest shuttle mission to the International Space Station, putting the finishing touches on a Canadian-built, double-armed robot. Rick Linnehan and Robert Behnken worked for nearly seven hours to equip the robot with tools and spare parts before Dextre, as the robot is called, begins to help astronauts with their spacewalks and takes over some maintenance and service work on the expanding space station.

On an earlier spacewalk, Linnehan and Mike Foreman attached Dextre's two arms, each 3.35 metres long, to the station.

Dextre, which cost more than 200 million dollars, is the final component of the station's mobile servicing system.

Before the shuttle returns to Earth March 26, the Endeavour astronauts are to perform two more spacewalks outside the station on Thursday and Saturday.

Over the past year and a half, shuttles have transported huge elements to the space station construction site, including large solar collectors and truss structures.

The goal is to finish construction by 2010 with double the space for orbiting astronauts and an expanded capacity for experiments so the US space agency could retire the 26-year-old shuttles.

After the shuttle programme retires, Russia's Soyuz craft would continue to lift astronauts to the station, but because of their small size, they are unable to carry the huge construction pieces and experimental modules now being transported by shuttles.

More description from AP

Two spacewalking astronauts attached 11-foot arms to the international space station's huge new robot yesterday, preparing the giant machine for its handyman job on the orbital outpost.

more stories like thisThe Canadian-built robot, named Dextre, will be 12 feet high and weigh 3,400 pounds when it's fully assembled. It is designed to assist spacewalking astronauts and possibly take over some of the tougher chores, such as lugging around big replacement parts.

Hours after the spacewalk, the shuttle crew tested Dextre's electronics, joints, and brakes, finding one small problem. One of the wrist joint brakes in Dextre's left arm slipped more than engineers wanted, but officials said that would not affect its operations.

The already challenging spacewalk turned grueling as Richard Linnehan and fellow astronaut Michael Foreman struggled to release one of the robot's arms from the transport bed where it had been latched down for launch.

Two of the bolts wouldn't budge, even when the astronauts banged on them and yanked as hard as they could. They had to use a pry bar to get it out.

The other arm came out much more smoothly and quickly, paving the way for Linnehan to pull up Dextre's body 60 degrees, like Frankenstein rising from his bed. That was the ideal position for plugging in Dextre's gangly arms to its shoulders.

"The whole team did a spectacular job today," Mission Control radioed the crew after the spacewalk. "You guys ought to be proud of yourselves."

Zebulon Scoville, the lead spacewalk officer for Endeavour's mission, said the ground team was ecstatic when Linnehan and Foreman got the last bolt out.

The seven-hour overnight spacewalk - which lasted into the early hours of yesterday - came close to being drastically altered or even delayed. For nearly two days, a cable design flaw prevented NASA from getting power to Dextre, lying in pieces on its transport bed.

But Dextre got the power it needed to wake up and keep its joints and electronics from freezing when the astronauts gripped it with the space station's mechanical arm on Friday night.

After the spacewalk, the crew hooked Dextre back up to the mechanical arm to keep the robot warm. That also allowed NASA to perform tests to ensure all of Dextre's electronics are working properly.

Dextre - short for dexterous and pronounced like Dexter - has seven joints per arm and can pivot at the waist. Its hands, or grippers, have built-in socket wrenches, cameras, and lights. Only one arm is designed to move at a time to keep the robot stable and avoid a two-arm collision.

Space station astronauts will be able to control Dextre, as will flight controllers on the ground. The robot will be attached at times to the end of the space station arm.

The crew will finish building Dextre during a third spacewalk, set for tonight.

Mission Control jokingly told the astronauts on Saturday that in order to guard against a mutiny, some new flight rules were being instituted, which recalled two of the "three laws of robotics" devised by writer Isaac Asimov.

"Dextre may not injure a human being or, through inaction, allow a human being to come to harm," Mission Control wrote in an e-mail. "Dextre must obey orders given to it by human beings, except where such orders would conflict with the First Law."

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