Spacewalking astronauts prepped the International Space Station on Friday for a new parking spot reserved for commercial crew capsules.
The 250-mile-high complex already has one docking port in place for the SpaceX Crew Dragon and Boeing Starliner, which should start carrying up astronauts as early as next year. Friday's spacewalk set the stage for a second docking location. A new docking device will fly up late this year or early next.
NASA astronaut Shane Kimbrough disconnected all four cables from an old docking port, using some extra force on one. He looped a spare tether around the balky cable and pulled, and off it came. "Nicely done, Shane," Mission Control radioed.
On Sunday, flight controllers in Houston will move the old port to provide better clearance for the future ships. Then on Thursday, the crew will conduct another spacewalk to secure the unit.
Until the new crew capsules come on line, U.S. astronauts will keep riding Russian rockets to orbit.
As Kimbrough worked on the docking port and replaced a computer-relay box, French astronaut Thomas Pesquet hunted for signs of an ammonia coolant leak in outdoor plumbing. The leak, while still small, has worsened recently, and NASA wants to pinpoint the location.
"No leaks. No flakes whatsoever," he reported.
During their 6 ½-hour excursion, the spacewalkers also replaced a pair of Japanese cameras, greased latching mechanisms on the end of the big robot arm and even tackled some extra work.
Their crewmates welcomed them back inside, wearing special black glasses and face masks, after Kimbrough reported there was a yellow chalk-like substance on one of his gloves. As an added precaution, both of his gloves were bagged before they came off.
NASA wants to cram in two and possibly three spacewalks before Kimbrough, the station's commander, returns to Earth on April 10.
Before a third spacewalk, Orbital ATK needs to launch a cargo ship to the space station with replacement parts. That shipment was supposed to be there by now, but repeatedly has been delayed because of rocket concerns. It's unclear when the Atlas V rocket will be ready at Cape Canaveral, Florida.
NASA has been contracting out cargo deliveries since the end of the space shuttle program in 2011. The space agency is counting on private companies to do the same with astronauts.
"It will be exciting to see a new way to bring crew members into orbit," NASA astronaut Robert Behnken said from Mission Control. He is among four astronauts training for the Dragon and Starliner test flights.