SpaceX's Crew Dragon spacecraft took off on Saturday morning, marking the first major step towards US ambitions to resume sending astronauts into space on its own spacecraft on American soil.
The uncrewed spacecraft launched from Nasa's Kennedy Space Centre in Florida at 2.49am local time (7.49am UK time) as planned, on top of a Falcon 9 rocket, carrying a dummy pilot called Ripley – a nod to Sigourney Weaver's character in the Alien movies – loaded with sensors to feed back information on the journey's progress.
The launch will provide vital data to SpaceX and Nasa that will determine whether the spacecraft is ready to carry passengers.
The American space agency ended its own Space Shuttle in 2011, opting for a new Commercial Crew Programme working with Elon Musk's SpaceX and Boeing.
Since then, it has relied on Russia's Soyuz spacecraft to blast astronauts into space, which costs 81 million dollars a seat (£61 million).
Crew Dragon's lift off has been hit by several delays along the way, previously scheduled for January 7, before moving to January 17 and then pushing it back again to no earlier than February.
"This is really a significant achievement in the history of American space flight," said Jim Bridenstine, Nasa administrator.
"We want to make sure we keep our partnership with Russia, which has been very strong for a long period of time, going back to the Apollo Soyuz era, but we also want to make sure we have our own capability to get back and forth to the ISS, so that we can have this strong partnership where they can launch on our rockets and we can launch on their rockets.
"But I think another big milestone here is the idea that we're not as an agency, as Nasa, we're not purchasing, owning and operating our own rockets at this point, we're looking to a future where we can be a customer, one customer of many customers in a very robust commercial marketplace in lower Earth orbit."
The crew capsule is expected to reach the ISS (International Space Station) at 6.05am (11.05am UK time) on Sunday, delivering around 400 pounds of cargo and staying for around five days before returning to Earth.
A trial carrying passengers for the first time could happen as soon as July, with astronauts Bob Behnken and Doug Hurley lined up to take the ride.