After less than 24 hours of travel from Earth, NASA's Doug Hurley and Bob Behnken on Sunday successfully docked their SpaceX Dragon capsule with the International Space Station.
The two men are 250 miles above Earth, for a stay of up to four months, after which they will come home with a Right Stuff-style splashdown at sea, something the world hasn't witnessed since the 1970s.
The crew successfully opened the hatch connecting the Dragon to the International Space Station about two hours after docking on Sunday.
The astronauts lifted off atop a Falcon 9 rocket on Saturday, becoming the first to leave U.S. soil for space in nine years.
SpaceX becomes the first private company to launch people into orbit, a feat achieved previously by only three governments: the U.S., Russia and China.
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At a post-liftoff rally held at NASA's massive 525-foot-high Vehicle Assembly Building, President Donald Trump commended SpaceX founder Elon Musk and proclaimed: "Today we once again proudly launch American astronauts on American rockets, the best in the world, from right here on American soil."
"Thanks for the great ride to space," Hurley told SpaceX ground control. The two crewmates batted around a floating blue dinosaur plush toy doubling as a dragon, demonstrating that they had reached zero gravity.
The mission is technically considered a test flight. The next SpaceX voyage to the space station, set for the end of August, will have a full, four-person crew: three Americans and one Japanese.
Associated Press writers Jill Colvin and Mike Schneider in Cape Canaveral, Fla., contributed to this report.