Three spacewalks to kick off big year aboard the ISS

Astronauts Terry Virts, left, and Expedition 42 commander Barry "Butch" Wilmore, right, inside the space station's airlock where they have been readying their suits for three planned spacewalks. The excursions will kick off a busy year of work to ready the station for eventual visits by new U.S. commercial crew ferry ships. NASA TV

NASA space station managers decided Thursday to delay the first two of three planned spacewalks by one day to give flight controllers and engineers a chance to catch their collective breath after exhaustive troubleshooting to verify the health of critical internal spacesuit components.

Expedition 42 commander Barry "Butch" Wilmore and Terry Virts plan to install more than 760 feet of power and data cables needed for new docking mechanisms that will be used by commercial crew ferry ships being built by Boeing and SpaceX. They also plan to install and hook up two sets of antennas, part of a new communications system that will be used by crews approaching and departing the lab complex.

The first spacewalk, originally planned for Friday, will slip to Saturday, starting around 7:10 a.m. EST (GMT-5) and the second outing will move one day to Wednesday. The third EVA remains on track for March 1 as originally planned pending additional review.

The decision to press ahead, albeit with a slight delay, was made after engineers concluded the suits that will be worn by Wilmore and Virts were healthy and not likely to suffer failures due to corrosion like that found in two spacesuit fan/pump/separator assemblies that were returned to Earth for analysis.

The modules in question circulate oxygen and cooling water throughout the spacesuit using a common motor and drive shaft. Each suit also is equipped with an emergency backup system.

After extensive troubleshooting, engineers concluded the drive shaft bearing corrosion seen in the fan assemblies shipped back to Earth likely was the result of additional testing implemented after water backed up into the helmet of spacewalker Luca Parmitano in 2013.

While some bearing corrosion is believed to be present in the fan/pump/separator in Virts' spacesuit, analysis indicates it is well below the threshold that could cause the unit to fail during use. And even if it did, officials said, the astronaut would have more than enough time to get back to the station's airlock using the suit's backup system.

As a result, mission managers cleared the astronauts to proceed after a one-day delay.

"We're not in a big hurry out get out the door on these," said a NASA spokesman. "Twenty four hours will just kind of make life easier."

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Three spacewalks to kick off big year aboard the ISS