One of two spacewalking astronauts can be seen floating upside down at the center of this view showing the forward end of the International Space Station. The astronauts installed power and data cables to support new docking mechanisms that will be used by commercial crew capsules starting in 2017. NASA TV

Last Updated Feb 21, 2015 3:20 PM EST

Astronauts Barry "Butch" Wilmore and Terry Virts floated outside the International Space Station Saturday and installed wiring needed for two new docking mechanisms that will be attached later this year for use by new Boeing and SpaceX crew capsules.

The Boeing-built International Docking Adapters, or IDAs, will allow the commercially developed ferry craft to dock at the front and top of the forward Harmony module starting in 2017. Two other ports on the Earth-facing side of the station will be available for use by U.S. cargo ships.

Floating in the station's Quest airlock module, Wilmore and Virts switched their spacesuits to battery power at 7:45 a.m. EST (GMT-5) to officially begin EVA-29, the 185th spacewalk devoted to station assembly and maintenance since construction began in 1998.

This was the first of three spacewalks by Wilmore and Virts to install more than 760 feet of cabling and to attach new antennas to prepare the space station for eventual dockings by commercial crew capsules. The two additional spacewalks are planned for Wednesday and March 1.

During Saturday's excursion, the spacewalkers spent most of their time working at the front of the station at the forward end of the Harmony module where a docking port extension known as Pressurized Mating Adapter No. 2 is attached. PMA-2 is where visiting space shuttles once docked and where one of the new IDAs will be attached later this year.

After removing micrometeoroid shields from the forward end cone of Harmony, Wilmore and Virts unplugged no-longer-needed cables and installed new power and data lines to support IDA-1. All in all, Wilmore and Virts deployed about 340 feet of cable.

The astronauts also disconnected four cables from the end cone of the Destiny laboratory module that were once used to deliver power to docked space shuttles. New cables will be plugged in later to support the new docking adapters.

With all of their primary objectives completed, Wilmore and Virts returned to the airlock, ending the spacewalk at 2:26 p.m. for a duration of six hours and 41 minutes.

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