Four astronauts were successfully launched on the SpaceX Crew Dragon "Resilience" to the International Space Station last night.

It is the first of what the US hopes will be many routine missions following a successful test flight in late spring.

Three Americans, Michael Hopkins, Victor Glover and Shannon Walker, and Japan's Soichi Noguchi blasted off at 7.27pm (12.27am Irish time) from the Kennedy Space Center in Florida.

It ended almost a decade of international reliance on Russia for trips on its Soyuz rockets.

"This is a great day for the United States of America, and a great day for Japan," said NASA administrator Jim Bridenstine during a post-launch press conference.

Twelve minutes after liftoff, at an altitude of 200km and a speed of 27,000km per hour, the capsule successfully separated from the second stage of the rocket.

"That was one heck of a ride," said mission commander Hopkins from orbit.

SpaceX confirmed that it was on the right orbit to reach the ISS a little more than 27 hours later, at around 4am Irish time tomorrow.

The astronauts will join two Russians and one American aboard the station and stay for six months.

There was a problem with the cabin temperature control system, but it was quickly solved.

"She's operating just fine," said SpaceX president Glynne Shotwell during the press conference.

But "we'll be able to breathe a sigh of relief, 26 or so hours from now, once we hand the crew over to NASA".

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.

US President-elect Joe Biden hailed the launch on Twitter as a "testament to the power of science and what we can accomplish by harnessing our innovation, ingenuity, and determination," while US President Donald Trump called it "great".

Vice President Mike Pence, who attended the launch with his wife Karen, called it a "new era in human space exploration in America".

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.

At the end of its missions, the Crew Dragon deploys parachutes and then splashes down in water, just as in the Apollo era.

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.

NASA turned to SpaceX and Boeing after shuttering the checkered Space Shuttle programme 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 programme 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 programme floundered after a failed test of its uncrewed Starliner last year.

But SpaceX's success will not mean the US will stop hitching rides with Russia altogether, said Mr Bridenstine.

The goal is to have an "exchange of seats" between American astronauts and Russian cosmonauts.

He also explained it was necessary in case either programme was down for a period of time.

The reality, however, is that space ties between the US and Russia, one of the few bright spots in their bilateral relations, have frayed in recent years.

Russia has said it will not be a partner in the Artemis programme to return to the Moon in 2024, claiming the NASA-led mission is too US-centric.

Dmitry Rogozin, the head of Russia's space agency, has also repeatedly mocked SpaceX's technology, telling a state news agency he was unimpressed with the Crew Dragon's "rather rough" water landing and saying his agency was developing a methane rocket that will be reusable 100 times.

But the fact that a national space agency feels moved to compare itself to a company arguably validates NASA's public-private strategy.

SpaceX's emergence has also deprived Roscosmos of a valuable income stream.

The cost of round-trips on Russian rockets had been rising and stood at around $85m per astronaut, according to estimates last year.

Presidential transitions are always a difficult time for NASA, and the ascension of Mr Biden in January is expected to be no different.

The agency has yet to receive from Congress the tens of billions of dollars needed to finalize the Artemis programme.

Mr Bridenstine has announced that he will step down, to let the new president set his own goals for space exploration.

So far, Mr Biden has not commented on the 2024 timeline.

Democratic party documents say they support NASA's Moon and Mars aspirations, but also emphasise elevating the agency's Earth sciences division to better understand how climate change is affecting the planet.