Computer Repair Successful During Spacewalk On International Space Station

Two clambered outside the space station to reach a failed back-up computer.


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ock Mastracchio and Steve Swanson
NASA spacewalkers Rock Mastracchio and Steve Swanson (Image Credit: NASA TV)

Two NASA astronauts, Rick Mastracchio and Steve Swanson, donned spacesuits Wednesday morning and clambered outside the space station to reach a failed back-up computer bolted onto the station’s main truss.

The device is known as a multiplexer-demultiplexer, or MDM, and it’s a computer relay device that helps monitor the station’s cooling loops and control the movement of the station’s solar panels.

While joking around with Swanson, Mastracchio unbolted the dead device and swapped in a spare. He used a pistol-grip tool to tighten up three bolts.

“You’re working over there, aren’t you?”

“Yeah, we’re working!”

Mastracchio narrated his step-by-step progress to Mission Control in Houston, where engineers gave him feedback on the proper settings for the drill. 

“Two turns, no torque,” he reported as he tightened the bolt. “Three turns, zero torque. Four turns, zero torque. Five turns, picking up on the torque!”

Mission Control managers had carved out two and a half hours for the spacewalk, but the astronauts worked so quickly they shaved almost an hour off that time.

NASA spokesman Dan Huot says that’s because the astronauts practice so thoroughly while back in Houston.

pacewalker works on the S0 truss
A spacewalker works on the S0 truss after replacing a failed backup computer. (Image Credit: NASA TV)

In fact, they had specifically practiced for this computer-swapping task. The task is one of the so-called “Big Twelve.”

“There are 12 major potential failures that could happen onboard the International Space Station that would warrant what we call a contingency space walk,” Huot said. “And they train for all 12 of those.”

Astronauts practice underwater at the Johnson Space Center, wearing their spacesuits in a giant pool known as the Neutral Buoyancy Laboratory.

“Swimming underwater is actually one of the best ways to simulate microgravity,” Huot said. “So we have this 40-foot deep pool with a mock-up of the International Space Station in it. These astronauts will spend hours training inside of that pool before they launch to the station.”

Including this one, there have been a total of 179 spacewalks at the space station — either to assemble the station or conduct maintenance.

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