Astronauts take first spacewalk

[Guest Glenn]

Source: http://www.news.com.au/story/0,10117,19731977-2,00.html

 

DISCOVERY astronauts Piers Sellers and Mike Fossum stepped out of the International Space Station today for a spacewalk aimed at testing equipment for possible future repairs on the shuttle.

 

In the first of three planned spacewalks, the pair floated into space to climb on a boom extension added to the shuttle's robotic arm to test if it can be used as a platform for in-orbit repairs.

 

"Oh my goodness, it's a beautiful day in Ireland," British-born Sellers said as the shuttle, which docked to the ISS on Thursday, passed over the British isles.

 

The simulation is part of an intense effort by NASA to improve safety for its astronauts since seven of them died in the Columbia accident in February 2003.

 

Before starting their simulation, Fossum and Sellers, a British-born American, fixed an ISS cable in about 30 minutes.

 

During the six-and-a-half-hour excursion, Sellers was to step on the 15-metre-long boom added to the equally long robotic arm and pretend to take photographs and grab tools behind him.

 

The two astronauts were to then climb on the platform together and move around to test its stability.

 

The National Aeronautics and Space Administration wants to resume regular shuttle missions to finish building the ISS before the fleet is retired in 2010, but it must first show it has made space flights safer.

 

The ability to make in-orbit repairs is among several efforts by the US space agency to ensure the shuttle can be safely flown back to earth. New repair techniques were tested in the first post-Columbia flight last year.

 

The first spacewalk could serve as a practice run for repairs in this shuttle mission, as analysts reviewed Discovery's heat shield for potential damage.

 

Analysts studying hundreds of images found two gap fillers sticking out from between thermal tiles in Discovery's underside. Last year, an astronaut performed a spacewalk to remove similar protuberances for the first time.

 

Deputy shuttle program manager John Shannon indicated a spacewalk could take place, if necessary, to take out gap fillers deemed potentially dangerous.

 

"We don't rule out anything until the analysts come in and say we don't have a problem," Shannon told reporters yesterday at the Johnson Space Centre in Houston, Texas. "Right now, the options are on the table."

 

NASA added an extra day to the mission yesterday in order to have time to conduct a third spacewalk to test new repair techniques, a move planned before Tuesday's shuttle launch.

 

Before NASA announced the 13th day, Fossum told CBS radio he was "anxious" to test the heat shield repair.

 

Proving "we can repair (the shuttle's heat shield) in flight is pretty valuable to the program," he said from the space station.

 

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

 

In addition to trying new repair techniques, NASA has made several modifications to the foam insulation to reduce the loss of debris during liftoff.

 

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.

 

If NASA concludes, however, that the shuttle suffered irreparable damage, the astronauts will take refuge in the ISS and wait for a rescue mission.