Crew-4 mission astronauts walk out at the Kennedy Space Center in Florida on Wednesday. AFP
The SpaceX launch vehicle, consisting of a two-stage Falcon 9 rocket topped with a Crew Dragon capsule dubbed Freedom, lifted off with its crew of four at 3:52am EDT (0752 GMT) from NASA's Kennedy Space Center in Cape Canaveral, Florida.
If all goes according to plan, the three US astronauts and a European Space Agency (ESA) crewmate from Italy will reach the space station after a 17-hour flight and dock around 8:15pm EDT (0015 GMT Thursday) to begin a six-month science mission orbiting some 250 miles (420 km) above Earth.
The liftoff was carried live on a NASA webcast, which showed the Falcon 9 ascending from the launch tower as its nine Merlin engines roared to life in billowing clouds of vapor and a reddish fireball that lit up the pre-dawn sky.
The four astronauts were seen strapped into the pressurized cabin of their capsule and seated calmly in their helmeted white-and-black spacesuits moments before launch.
The mission, designated Crew 4, is the fourth full-fledged ISS crew NASA has launched aboard a SpaceX vehicle since the private rocket venture founded by Musk, also owner of electric carmaker Tesla Inc, began flying US space agency astronauts in 2020.
In all, SpaceX has launched six previous human spaceflights over the past two years.