Space taxis made by Boeing and SpaceX could carry astronauts to the ISS as soon as 2017, and NASA has begun preparing for their arrival. On Friday, astronauts Jeff Williams and Kate Rubins will do a six-and-half-hour spacewalk to install a parking spot where the taxis can dock. Previous crew members already laid out hundreds of feet of power and data cables, so the duo will be in charge of finishing the job. They'll get some help from their helper robot, the Canadarm2, which will extract the dock from the SpaceX Dragon capsule that carried it on board later today. Canadarm2 will also position the dock just a few inches away from where it's supposed to be attached.