A recycled SpaceX Crew Dragon capsule with four astronauts aboard has docked at the International Space Station.
It was the third crew sent to the ISS by SpaceX, as part of its multibillion dollar contract with Nasa, and the first time the company was reusing a rocket, the Falcon 9 and a spacecraft, the Endeavor.
The Crew-2 mission, which includes the first European, Thomas Pesquet of France, blasted off from pad 39A at the Kennedy Space Center in Florida before dawn on Friday.
"We're glad to be back in space," said mission commander Shane Kimbrough of the United States.
Flying on used vehicles is a key cost-saving goal of Nasa's partnerships with private industry.
Three white Teslas that whisked the astronauts to the launchpad bore license plates reading "recycle," "reuse," and "reduce" – a nod to the fact that both the Falcon 9 booster and Endeavour were deployed on previous missions.
SpaceX's first crewed mission to the ISS launched last May, ending nine years of American reliance on Russian rockets for rides, following the end of the Space Shuttle program.
"I think we're at the dawn of a new era of space exploration," said SpaceX founder Elon Musk, who made a surprise appearance at the post-launch press conference.
The arrival of the space quartet – which also includes American Megan McArthur and Japan's Akikho Hoshide – will bring the number of people on the station to 11, as the Crew-2 team overlaps for a few days with Crew-1 astronauts, in addition to three Russian cosmonauts.
The launch is a major milestone for Europe, which named the mission "Alpha" after the star system Alpha Centauri.
"This is really the golden era for us in terms of exploitation of the International Space Station," Frank De Winne, head of ISS programs for the European Space Agency (ESA), told AFP.
Germany's Matthias Maurer and Italy's Samantha Cristoforetti are set to follow Mr Pesquet on SpaceX missions, this fall and next spring respectively.
The next module of the ISS, built by Russia, should reach the station in July and will include a robotic arm built by ESA that Mr Pesquet will help make operational, added Mr De Winne.
ESA will also be a key partner to the United States in the Artemis program to return to the Moon, providing the power and propulsion component for the Orion spacecraft, and critical elements of a planned lunar orbital station called Gateway.
The Crew-2 team has around 100 experiments in the diary during their six-month mission.
These include research into what are known as "tissue chips" – small models of human organs that are made up of different types of cells and used to study things like aging in the immune system, kidney function and muscle loss.
In terms of the environment, by the time Crew-2 returns in fall, it will have taken 1.5 million images of the Earth, documenting phenomena like artificial lighting at night, algal blooms, and the breakup of Antarctic ice shelves.
Another important element of the mission is upgrading the station's solar power system by installing new compact panels that roll open like a huge yoga mat.