SpaceX’s newly designed Crew Dragon capsule, dubbed Resilience, has successfully docked at the International Space Station on schedule after a 27-hour flight.

Hovering 20 metres out from the ISS, and after a tense few minutes waiting for the sun orbit, Dragon “autonymously” docked at 3.01pm (AEDT) without incident. And 12 minutes later, the ISS secured a hard-capture, preparing to welcome its four astronauts.

Three Americans and one Japanese astronaut, in a spacecraft from Elon Musk’s SpaceX purchased by NASA, will live on the orbiting laboratory until a replacement crew arrives in April.

This is the second astronaut mission for SpaceX but the first time Elon Musk’s company delivered a crew for a half-year station stay.

NASA tweeted: “SpaceX Crew-1 astronauts aboard is officially attached to the space station”.

“Slow and steady wins the race,” NASA commentators said. “The crew must be so excited.”

Another US astronaut and two Russian cosmonauts are aboard the space station from a previous mission.

“Welcome to the ISS. We can’t wait to have you onboard,” said Kate Rubins, a US astronaut already on the space station.

Tweet from @NASA

SpaceX successfully launched four astronauts on a flight to the ISS at 11.27am on Monday local time.

The fully fledged mission is NASA’s first sending a crew into orbit aboard a privately owned spacecraft.

An air leak caused an unexpected drop in capsule pressure less than two hours before launch on Monday but technicians said they conducted a successful check and the scheduled launch was still on.

The ride to the space station, an orbiting laboratory 400 kilometres above Earth, was originally scheduled to begin on Saturday.

However the launch was postponed for a day due to forecasts of gusty winds – remnants of Tropical Storm Eta – that would have made a return landing for the Falcon 9’s reusable booster stage difficult, NASA said.

The astronauts donned their custom white flight suits and arrived at the Kennedy Space Centre launch pad on schedule at 4.30pm in three white Tesla SUVs, flanked by NASA and SpaceX personnel.

President-elect Joe Biden Tweeted his congratulations, saying the launch was “a testament to the power of science”.

NASA is calling the flight its first “operational” mission for a rocket and crew-vehicle system that was 10 years in the making.

It represents a new era of commercially developed spacecraft – owned and operated by a private entity rather than NASA – for sending Americans into orbit.

A trial flight of the SpaceX Crew Dragon in August, carrying just two astronauts to and from the space station, marked NASA’s first human space mission to be launched from US soil in nine years, following the end of the space shuttle program in 2011.

In the intervening years, US astronauts have had to hitch rides into orbit aboard Russia’s Soyuz spacecraft.

The Resilience crew includes commander Mike Hopkins and fellow NASA astronauts, mission pilot Victor Glover and physicist Shannon Walker.

They were joined by Japanese astronaut Soichi Noguchi, making his third trip to space after previously flying on the US shuttle in 2005 and Soyuz in 2009.

-with AAP