Two NASA astronauts have ventured outside the International Space Station as they continue the transformation of the orbiting outpost.

The spacewalkers are preparing for commercial crew vehicles that will one day dock at the ISS.            

This is the second of three planned spacewalks and NASA says to expect even more spacewalks this year to get the ISS ready for American’s launching to space from the U.S. Both SpaceX and Boeing are planning to launch Americans, from the Space Coast starting in 2017.

But to make sure that these commercial vehicles can dock at the space station, the proper docking adaptors and cables need to be in place.          

NASA astronauts Barry “Butch” Wilmore and Terry Virts will spend six and a half hours outside the space station.

Like their first spacewalk on Saturday, the pair will be the cable guys once again, deploying two bundles of cables that will be used to provide power and data for a new docking adaptor that will be used by the new commercial vehicles.

NASA says this is just the beginning of work on the ISS.

“This entails a tremendous amount of relocation. This is the largest project we’ve done, certainly since the end of the shuttle program,” said Sean Kelly, NASA Senior Project Manager.

The astronauts will also be lubricating the robotic arm and start preparations for some new modules that will be installed later this year.

That includes Bigelow’s inflatable module. Later this year NASA is going to install a private company’s module that will expand in space, a kind of inflatable room attached to the space station.

Meanwhile, NASA is also keeping a close eye on the spacesuits.

There were no issues with them on Saturday’s spacewalk, but they have caused problems in the past.