US astronauts step out on spacewalk for repairs

WASHINGTON - Agence France-Presse

This April 23, 2014 NASA TV image shows International Space Station(ISS) astronauts Koichi Wakata of Japan as he helps Rick Mastracchio of the US(front) prepare for a spacewalk to install a backup computer that failed earlier this month. AFP Photo

Two US astronauts stepped out on a brief spacewalk Wednesday to install a backup computer at the International Space Station after one failed earlier this month.
      
Astronauts Rick Mastracchio and Steve Swanson climbed out of the space station without incident starting at 9:56 am (1356 GMT), about a half hour behind schedule. The spacewalk was expected to last 2.5 hours.
      
The computer they will remove and replace is known as a multiplexer/demultiplexer (MDM), one of 45 aboard the orbiting laboratory.
      
The 10-year-old MDM failed after a routine restart operation on April 11.
      
NASA said the broken model provides commands to certain space station systems, including the external cooling system, solar alpha rotary joints and mobile transporter rail car.
      
The astronauts were also planning a quick "get-ahead" task to remove a lanyard on the secondary power distribution assembly -- a wiring hub -- that was located near the computer.         The spacewalk will mark the 179th in support of the orbiting space station, a global collaboration that includes Europe, Canada, Japan, the United States and Russia.
      
Just prior to the spacewalk, a Russian cargo capsule undocked from the space station for a two-day test of a new system to automatically reattach itself, NASA said.
      
The Progress 53 resupply ship separated from the space station at 4:58 am (0858 GMT), and was to retreat a distance of 311 miles (500 kilometers).
      
"It will return back to the Zvezda docking port Friday morning after Russian flight controllers have tested its new Kurs automated rendezvous system," the US space agency said.
      
A similar operation was done in July 2012 when another Progress cargo freighter pulled away from the station and redocked, also for a trial run of its automated return system.