Astronauts in spacewalk 'ballet'

[Guest Glenn]

Source: http://www.news.com.au/story/0,10117,19 ... 09,00.html

 

TWO space shuttle Discovery astronauts performed a spacewalk "ballet" overnight to repair hardware critical to the completion of the International Space Station, a day after their spaceship was cleared to return home.

 

Astronauts Mike Fossum and Piers Sellers, who arrived at the ISS last week aboard Discovery with five colleagues, floated up on the ISS to install a spare pump and replace a broken cable reel, according to NASA television images.

 

"I'm working up a sweat," Fossum said as the duo made preparations to replace the reel for a cable that provides power to the orbiting laboratory's mobile transporter, a sort of railcar needed to finish building the station.

 

Sellers and Fossum, who a day earlier said the spacewalk would be "quite a ballet", moved to another spot on the ISS to install a spare pump module to an external stowage platform.

 

"Good job guys, slightly ahead of time. It's a pleasure to watch," mission control capsule commentator Julie Payette said from the Johnson Space Center in Houston, Texas after they placed the pump.

 

The astronauts then moved to the shuttle's payload bay to make a tricky equipment swap. With his feet secured on a strap on the cargo bay, Sellers at one point held the old and new cable reels simultaneously during a handoff with Fossum, who was held horizontally by the ISS's robotic arm.

 

Before replacing the part, the astronauts took a moment to admire the view about 350km above Earth.

 

"It's like standing in an all-around Imax (3D movie theatre). It's just beautiful," Sellers said.

 

The pair then slipped back inside the ISS's airlock chamber after completing the nearly seven-hour-long spacewalk.

 

Discovery docked to the ISS on Friday in just the second shuttle flight since the Columbia accident that killed seven astronauts in February 2003.

 

Fossum and Sellers will venture out of the ISS again on Thursday to try out shuttle repair techniques pivotal for NASA's efforts to increase space flight safety.

 

They will test repairs on pre-damaged samples of reinforced carbon-carbon (RCC), a composite material used on the shuttle's wing leading edges as a heat shield.

 

In their first spacewalk on Sunday, Sellers and Fossum tested a boom extension on the shuttle's robotic arm as a possible work platform for future repairs. NASA described the test as a success.

 

The US space agency has taken several measures to improve safety in order to resume regular shuttle missions.

 

NASA administrator Michael Griffin wants to conduct 16 more flights to complete the ISS by 2010, when the 25-year-old shuttle fleet is scheduled to be retired.

 

In addition to testing in-orbit repair techniques, NASA has made several modifications to foam insulation on the shuttle's external fuel tank to prevent debris from striking the spacecraft during liftoff.

 

Officials yesterday declared the shuttle fit to return to Earth on July 17.

 

NASA analysts who reviewed images of the shuttle's heat shield found no damage that could prevent Discovery from coming home.

 

Discovery will get a final checkup at the end of the mission, however, to make sure it was not hit by micrometeorites while in orbit.

 

Columbia's demise was caused by foam insulation that peeled off its external fuel tank and pierced its heat shield during liftoff, dooming its return to Earth on February 1, 2003.

 

NASA has since made several fuel tank modifications to limit the size of debris during blastoff.

 

Officials were pleased with the performance of Discovery's fuel tank during liftoff, saying it shed small pieces of debris as expected but too late into ascent to cause concern.