Astronauts board International Space Station from SpaceX capsule

Four astronauts carried into orbit by a SpaceX Crew Dragon boarded the International Space Station on Tuesday.

The "Resilience" spacecraft docked autonomously -- a process known as "soft capture" -- with the space station some 260 miles (400 kilometers) above the Midwestern US state of Ohio at 11:01pm on Monday (0401 GMT Tuesday), completing a 27.5-hour journey.

This is the second astronaut mission for SpaceX. But it's the first time Elon Musk's company is delivering a crew for a full half-year station stay.

The crew is comprised of three Americans -- Michael Hopkins, Victor Glover and Shannon Walker -- and Japan's Soichi Noguchi. They will remain at the orbiting lab until their replacements arrive on another Dragon in April.

The crew members each floated in zero gravity through a hatch and onto the ISS, where they were cheered and embraced by the station's three crew members.

The four astronauts named their capsule "Resilience" to provide hope and inspiration during an especially difficult year for the whole world. They broadcast a tour of their capsule Monday, showing off the touchscreen controls and storage areas.

Earlier, mission commander Hopkins gave pilot Glover his "gold pin," a NASA tradition when an astronaut first crosses the 100-kilometer Karman line marking the official boundary of space.

Glover is the first Black astronaut to make an extended stay at the ISS, while Noguchi is the first non-American to fly to orbit on a private spaceship. The crew joins two Russians and one American aboard the station, and will stay for six months.

Along the way, there was a problem with the cabin temperature control system, but it was quickly solved.

SpaceX briefly transmitted live images from inside the capsule showing the astronauts in their seats, something neither the Russians nor the Americans had done before.

SpaceX is scheduled to launch two more crewed flights for NASA in 2021, including one in the spring, and four cargo refueling missions over the next 15 months.

The Crew Dragon capsule earlier this week became the first spacecraft to be certified by NASA since the Space Shuttle nearly 40 years ago. Its launch vehicle is a reusable SpaceX Falcon 9 rocket.

NASA turned to SpaceX and Boeing after shuttering the checkered Space Shuttle program in 2011, which failed in its main objectives of making space travel affordable and safe.

The agency will have spent more than $8 billion on the Commercial Crew program by 2024, with the hope that the private sector can take care of NASA's needs in "low Earth orbit" so it is freed up to focus on return missions to the Moon and then on to Mars.

SpaceX, founded by Elon Musk in 2002, leapfrogged its much older rival Boeing, whose program floundered after a failed test of its uncrewed Starliner last year.