Nasa and SpaceX launched a new team of four astronauts to the International Space Station on Friday, for the first time using a spacecraft recycled from a previous mission to put a human crew in orbit.
Live video of the launch showed the rocket streaking through the early morning sky over Florida.
The Crew Dragon spacecraft reached orbit shortly before dawn, Nasa commentators said, with the Falcon 9 booster rocket touching down on one of the company's autonomous drone ships in the Atlantic Ocean.
The crew is scheduled to arrive at the space station, which orbits about 400km above Earth, early on Saturday after a flight of nearly 24 hours.
Managers from Nasa, the European Space Agency and the Japan Aerospace Exploration Agency (Jaxa), whose astronauts are aboard the Dragon capsule, gave the Crew-2 mission clearance to fly on Tuesday.
It was the first time astronauts have blasted into space on board a SpaceX rocket that has already been there.
The powerful Falcon 9 rocket and the Endeavour capsule both flew to the ISS last year.
Nasa astronauts Michael Hopkins, Victor Glover and Shannon Walker, with Jaxa astronaut Soichi Noguchi, were delivered to the ISS in a milestone for the commercial space sector, ending nearly a decade of reliance on Russia's ageing Soyuz rockets for delivering crews to the space station.
For the second launch to the ISS, two Nasa astronauts, Shane Kimbrough and Megan McArthur, were joined by the European Space Agency’s Thomas Pesquet and Japan’s Akihiko Hoshide.
The helmeted astronauts, dressed in their white flight suits and black boots, walked out of the space centre's operations building a little over three hours before launch time, waving to onlookers and bidding goodbye to loved ones.
A caravan of vehicles from Elon Musk's electric car manufacturer Tesla drove them to Launch Complex 39A, built during the 1960s and the same site used for the launch of the Apollo 11 flight to the Moon.
"There's nothing like it when you look out the window and see a spaceship getting prepared and realise that you're going to be riding on it in a few days," Ms McArthur said after arriving at Kennedy Space Centre last week.
The four astronauts will spend approximately six months on board the ISS, before returning to Earth on board the Crew Dragon capsule.
Ms McArthur made a bit of history herself as the first female pilot of the Crew Dragon and the second person from her family to ride aboard the SpaceX capsule. She is married to Nasa astronaut Bob Behnken, who flew the SpaceX demonstration flight with fellow astronaut Doug Hurley last year.