Crew Dragon is meant to transport astronauts eventually, but for this month's mission it carried a data-collecting test dummy named Ripley, which will monitor how traveling in the craft may affect humans. But that quickly changed once the hatch swung open and the space station astronauts floated inside.
The docking took place more than 400km above the Earth's surface, north of New Zealand - 27 hours after the capsule's launch on a SpaceX Falcon 9 rocket from the Kennedy Space Centre at Cape Canaveral in Florida.
NASA is anxious for reliable transit to and from the space station.
"Our honest congratulations to all earthlings who have enabled the opening of this next chapter in space exploration", NASA astronaut Anne McClain said from aboard the ISS during a welcoming ceremony for the Crew Dragon. After undocking from the space station, Crew Dragon will begin its descent to Earth. Its Falcon 9 rockets have resupplied the space station 15 times in seven years, even though one of them blew up in 2015.
Around 0900 GMT, Dragon was 3,000 meters away, NASA said.
"It's been 17 years, we still haven't launched anyone yet, but hopefully we will later this year".
"This is a critically important event in American history", Jim Bridenstine, the head of the U.S. space agency, told reporters, with the rocket and capsule visible behind him on the legendary launch pad where the Apollo missions to the Moon began.
If all goes smoothly, Crew Dragon could conduct a second test flight, with live crew, as soon as April.
Both astronauts due to make that journey, Doug Hurley and Bob Behnken, watched the automatic docking from mission control in Hawthorne, California.
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"The Crew Dragon is a fundamental redesign, with hardly a part in common with Dragon", SpaceX founder Elon Musk said early Saturday morning, after the launch, during a news briefing.
The demonstration flight of America's new astronaut capsule will see it attempt to dock with the International Space Station (ISS). Cargo Dragon must be manoeuvred with the station's robot arm. The ship obeyed general commands sent from the station such as "clear to proceed" or "retreat", but otherwise operated on its own.
The mission was supported by NASA and culminated in the Dragon automatically attaching itself to the space station, almost 260 miles above the Pacific ocean, north of the New Zealand coast. They burst into applause again, several minutes later, when the Dragon's latches were tightly secured.
For employees of SpaceX-who have worked to bring Crew Dragon to fruition for most of the last decade-Saturday morning's launch proved cathartic. The test dummy was nicknamed Ripley after the main character in the "Alien" movies.
Dragon will remain at the space station until Friday, when it undocks and aims for a splashdown in the Atlantic, a couple hundred miles off the Florida coast.
With the successful launch and docking procedure now behind it, only one important test remains for SpaceX's test flight: the return trip.
Next up, though, should be Boeing, NASA's other commercial crew provider. The Starliner is now due to make its first uncrewed test flight no earlier than April, and its first crewed flight no earlier than August.
NASA hopes to test the technology in the summer with human astronauts aboard.