Astronauts pull off urgent station repairs

Spacewalking astronauts completed urgent repairs at the International Space Station on Tuesday, replacing equipment that failed three days earlier and restoring a backup for a vital data-relay system.

It took commander Peggy Whitson much longer than expected to install the spare unit. Success finally came after her spacewalking partner, Jack Fischer, blasted the area with nitrogen gas to clear away flecks of metal.

Mission Control noted that the failure occurred only 2 days, 21 hours, 38 minutes earlier, “and we are already back in a good position, so excellent work. “

Testing confirmed the new unit worked, restoring full redundancy to the system that operates the space station’s solar panels, radiators and robotic equipment.

“Very good. We are really happy about that,” Whitson said.

Tuesday’s spacewalk lasted less than three hours — exceedingly short by NASA standards. Whitson has now tied the record for most spacewalks by an American — 10 — and moved up to third place on the all-time spacewalking list.

The failed data-relay unit — recently refurbished with upgraded software — was just installed in March. Even though a second unit worked just fine after Saturday’s breakdown, NASA scrambled to put together a spacewalk so there would be a backup in case that second unit failed, too, crippling the system for station cooling and solar energy production.

Whitson had no trouble removing the broken unit. But it took her two tries to install the replacement.

During the first attempt, Whitson discovered what appeared to be metal shavings in the holes for the bolts. Fischer used a cleaning tool — essentially a nitrogen gas blaster — and blew away debris from the three holes.

“I think all three look clean as a whistle,” he reported before Whitson bolted down the spare box.

The data-relay boxes are officially known as MDMs or multiplexer-demultiplexers. They’re compact: Each one weighs 50 pounds (22 kilograms) and measures 14 by 8 by 13 inches (35-20-33 centimeters.)

Whitson and Fischer were just out spacewalking on May 12. That excursion was cut short by leaking station equipment, leaving two antenna installations undone. So Fischer completed the chore Tuesday.