California's SpaceX has launched on a mission to re-supply the space station - the first cargo delivery to the orbiting outpost by a private company.
The firm's Falcon rocket, topped by an unmanned Dragon freight capsule, lifted clear of its Florida pad at 03:44 EDT (07:44 GMT; 08:44 BST).
The initial climb to an altitude some 310km above the Earth was scheduled to last a little under 10 minutes.
Once ejected, Dragon will then take a couple of days to reach the station.
The plan currently is for the vessel to demonstrate its guidance, control and communications systems on Thursday, at a distance of 2.5km from the International Space Station (ISS).
If those practice proximity manoeuvres go well, Dragon will be allowed to drive to within 10m of the station on Friday. Astronauts inside the platform will then grab the ship with a robotic arm and berth（停泊） it to the 400km-high structure.
The mission has major significance because it marks a big change in the way the US wants to conduct its space operations.
Nasa is attempting to offload routine human spaceflight operations in low-Earth orbit to commercial industry in a way similar to how some large organisations contract out their IT or payroll.
The carriage of freight will be the first service to be bought in from external suppliers; the transport of astronauts to and from the station will be the second, later this decade.
The US agency hopes these changes will save it money that can then be invested in exploration missions far beyond Earth, at destinations such as asteroids（小行星） and Mars.
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