Fixing computers in space requires more than IT

Astronauts Rick Mastracchio and Steven Swanson returned to the Quest airlock aboard the International Space Station at 11:32 a.m. EDT (GMT-4), ending a short but successful one-hour 36-minute spacewalk to replace a faulty external computer.

The start of the spacewalk, known as U.S. EVA-26, came just five hours after the departure of a Russian Progress supply ship that undocked from the Zvezda command module at 4:58 a.m. After moving about 300 miles ahead of the station, the uncrewed Progress will return and re-dock Friday to test an upgraded navigation and rendezvous system planned for future vehicles.

But the spacewalk was the focus for the station's NASA crew and flight controllers at the Johnson Space Center in Houston. The goal was to replace an external multiplexer-demultiplexer, or MDM, a 49-pound computer mounted in the central S0 segment of the station's solar power truss that failed April 11.

Less than an hour into a planned 2.5-hour spacewalk, Mastracchio and Swanson pulled a failed external computer from its rack in the central S0 truss segment of the International Space Station's solar power truss Wednesday and installed a replacement, making quick work of a critical repair.

Before unbolting the computer, Mastracchio reported there were no obvious signs of any damage in the area and examining the faulty "black box" after it was removed, he said everything looked good with no evidence of anything out of the ordinary. While additional troubleshooting will be needed to make sure, it would appear that an internal component failure of some sort was responsible for the original malfunction.

With the new computer in place, flight controllers sent commands to power it up and then began a series of diagnostic tests to verify its performance before uplinking the latest software. The faulty computer was carried back inside the station for troubleshooting and repairs.

"Your R & R was successful, we have a good MDM," Hansen called. "It's in diagnostic mode as expected."

"Oh, wonderful," one of the spacewalkers replied. "Fantastic," said the other.

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Fixing computers in space requires more than IT