Two crew members of the International Space Station ventured outside the orbiting research laboratory on Friday in the first of three outings to prepare the space station for future commercial space taxis and to carry out repair and maintenance.
US station commander Shane Kimbrough, 49, and French flight engineer Thomas Pesquet, 39, floated outside the station's airlock at about 7:30 am EDT (1130 GMT), NASA TV showed.
Working 402 km above Earth, the astronauts reconfigured the spaceship, adding docking ports for new spaceships in development by Boeing and Space Exploration Technologies, or SpaceX in an operation lasting six and a half hours.
The $100-billion International Space Station (ISS) is jointly operated by 15 nations.
Kimbrough, making his fifth spacewalk, headed to the station's central beam to upgrade a computer relay box before turning his attention to a docking system that will be used by future fleets of commercial space taxis.
''Expedition 50 commander Shane Kimbrough of NASA and flight engineer Thomas Pesquet of the European Space Agency conducted a spacewalk outside the International Space Station on Friday to disconnect cables and electrical connections on Pressurized Mating Adapter-3 (PMA-3), lubricate the latching end effector on the Canadarm2 robotic arm and replace a computer relay box on the station's truss.
''PMA-3 will be robotically relocated 30 March by ground controllers from the port side of the Tranquility module to the space-facing side of the Harmony module for the future installation of a second International docking adapter that will accommodate the arrivals of commercial crew vehicles.
''The spacewalk is the first of three planned in a two-week period for station crew members that will see PMA-3 reconnected to its new location on Harmony and an avionics box replaced that routes electricity and data to station experiments,'' the NASA release stated.
NASA is making the retrofits in the hope that private companies could begin flying astronauts to the station by the end of 2018. This would break Russia's monopoly on crew transportation, a service that costs NASA more than $80 million per person.
The first of the space taxis is scheduled for an unmanned debut test flight later this year.
On Sunday, ground control teams will then use the station's robot arm to move it onto a different module.
A second spacewalk by Pesquet and NASA astronaut Peggy Whitson is planned for Thursday, to reconnect cables to the relocated docking tunnel.
Once all the work is finished, the US side of the station will have two docking ports for passenger spaceships and two for cargo ships. Russia, which jointly operates the station with NASA, has five docking ports.
A third spacewalk is on hold pending the arrival of a cargo ship that includes items to be installed during the outing.