CAPE CANAVERAL, Fla. (AP) — It's the third spacewalk in just over a week for a pair of NASA astronauts.

Terry Virts and Butch Wilmore ventured out of the International Space Station on Sunday morning. They have 400 feet of cable and two antennas to install. Once that's complete, the spacewalkers will have routed nearly 800 feet of power and data lines, all of it needed for future American crew capsules.

NASA is paying Boeing and SpaceX nearly $7 billion to develop spacecraft capable of transporting astronauts to the space station. The first manned flight is targeted for 2017. New docking ports will fly up later this year.

Virts and Wilmore's first spacewalk was Feb. 21. Their second was Wednesday. NASA hasn't conducted such a quick succession of spacewalks since its former shuttle days.