SpaceX has become the first company to design, build, launch, and now dock a commercial spaceship made for flying people to the International Space Station.
Elon Musk's rocket company launched the seven-seat vehicle, called Crew Dragon, on Saturday at 2:49 am ET (7:49 am UTC).
By early morning on Sunday, the 14,000-lb (6,350 kilogram) space capsule had caught up to the football-field-size laboratory that orbits Earth.
After a series of safety checks, SpaceX began nudging Crew Dragon toward the front end of the space station.
At 5:51 am ET (10:51 am UTC), it made soft contact with a docking node, engaged six arms, and latched on. About 11 minutes later, the spaceship tightly screwed itself to Node 2 of the space station.
Nobody was on board to open Crew Dragon's hatch – only 400 lbs (181 kilograms) of cargo and a female crash-test dummy named "Ripley".
However, NASA says SpaceX's demonstration or Demo-1 mission was "a critical first step" in restoring US-crewed access to space, since the goal is to prove the new spaceship is safe to fly its astronauts.
"A new generation of space flight starts now with the arrival of @SpaceX's Crew Dragon to the @Space_Station," Jim Bridenstine, NASA's administrator, tweeted on Sunday.
"Congratulations to all for this historic achievement getting us closer to flying American Astronauts on American rockets."
NASA's space shuttle Endeavour was the last American human-rated ship to touch the space station, and that was in July 2011.
On Sunday, Crew Dragon docked with Node 2: the spot where NASA's 100-ton space shuttle orbiters often used to dock.
The symbolism was not lost on the space station's current three-person Expedition 58 crew, who opened the hatch, floated inside Crew Dragon at 8:07 am ET, and held a greeting ceremony for Crew Dragon live on NASA TV.
"It was a beautiful thing to see," said David Saint-Jacques, a Canadian astronaut and station crew member.
"Today we welcome a brand-new spacecraft to the space station, and a great new addition to the quiver of tools we have for humans to further space exploration. This is a good day, a first day of a new era for the next generation of space explorers."
During the brief greeting ceremony, Expedition 58 commander and Russian crew member Oleg Kononenko spoke first.
"On behalf of my crew, I would like to congratulate the United States of America and the NASA team for this very significant event: the launch and docking of the SpaceX Crew Dragon spaceship," Kononenko said.
"It's a historic step … on our way of human beings [moving] beyond low-Earth orbit to the Moon, and Mars, and the future."
Saint-Jacques spoke next, marveling at the thousands of people, years of work, and close collaboration between SpaceX and NASA that it took to pull off a docking of a commercial spaceship.
Last was Anne McClain, a NASA astronaut and another space station crew member. She had the most to say about Crew Dragon's successful arrival at her orbiting home in the sky.
"Our sincere congrats to all earthlings who have enabled the opening of this next chapter in space exploration," McClain said.
"And congratulations to all nations, private space firms, and individuals who wake up every day driven by the magic of exploration. This day belongs to all of us."
She remarked on the international makeup of the space station and the effort that went into its creation 250 miles (400 kilometres) above Earth, and how Crew Dragon is now part of it.
"Spaceflight gives us a chance to reflect on the context of our existence. We are reminded that we are human before any of our differences, before all of the lines are drawn that divide us," she said.
"We are reminded that we're at our best when we are a part of something bigger than ourselves.
She continued: "These events remind us that we are more alike than different, that we can be united by a cause that is not based on fear, threat, or a common enemy, but rather on a bold endeavour – an insatiable curiosity to go beyond what is known and to do what has never been done. We humans were built for exploration, and we were built to do it together."
McClain and her colleagues then floated into the Crew Dragon to show it off to the world.
Inside the spaceship, McClain grabbed onto a plush Earth toy that SpaceX had strapped into a seat before launch. Musk has called the toy a "super high tech zero-gravity indicator," and it's been floating around the cabin on the end of a string since Crew Dragon entered orbit.
"On behalf of Ripley, little Earth, myself, and our crew, welcome to the Crew Dragon," she said. "These amazing feats show us not how easy our mission is, but how capable we are of doing hard things. Welcome to the new era in spaceflight."
She then spun the Earth toy with a gentle nudge:
Crew Dragon's mission is not over with docking and hatch opening. It has to pull off a series of other feats before NASA will allow astronauts on board, including a textbook landing.
Launch and docking are what Musk described on Saturday as "some of the riskiest items" in the Demo-1 mission. But undocking, deorbit, and splashdown in water are up next.
The space station crew is supposed to close the Crew Dragon's hatch sometime on Thursday, and the ship is scheduled to depart at 2 am ET.
Crew Dragon is then scheduled to land in the Atlantic Ocean near Kennedy Space Center on Friday around 7:30 am ET.
If SpaceX can pull off Demo-1 with flying colours, the mission could be a major turning point for the company.
"The whole goal of SpaceX was crewed spaceflight, and improving space exploration technologies – that's actually the full name of the company: Space Exploration Technologies," Musk said during a press briefing on Saturday after launch.
He added: "It's been 17 years – we still haven't launched anyone yet – but hopefully we will later this year. That would definitely be the culmination of a long dream for me and a lot of other people at SpaceX."
Data gathered by Demo-1 will be used to tweak and finalise a new Crew Dragon that will actually fly astronauts on an experimental mission called Demo-2.
SpaceX and NASA may rocket that first crewed mission toward the space station as soon as July, and veteran astronauts Bob Behnken and Doug Hurley will be on board.
"It's an incredibly sleek-looking vehicle," Hurley said during an impromptu press briefing on Friday at Kennedy Space Center, adding that it's "a lot more intuitive" than the space shuttle.
He noted that instead of about 2,000 knobs, buttons, dials, switches, and other controls like a shuttle orbiter, Crew Dragon has about 30.
"We've been following the process for a few years at this point," Behnken said after launch on Sunday. "So seeing a success like this definitely gives us a lot of confidence in the future."