The launch window is five hours.
The first stage will separate from the spacecraft at an altitude of about 80 kilometers and will automatically return to Earth for future use.
During manned flights, the second stage usually separates about ten minutes after take-off.
The Dragon capsule will orbit Earth for three days at an altitude higher than the ISS.
After that, it will descend back to Earth, landing off the coast of Florida with the help of giant parachutes.
Heading and financing the mission is US billionaire Jared Isaacman, who invited three other people to join him through an original selection process.
Hayley Arceneaux, 29, is a nurse and a pediatric cancer survivor.
Chris Sembroski, 42, is a US Air Force veteran who now works in the aviation industry.
Geology professor Sian Proctor, 51, was a finalist to become a NASA astronaut more than a decade ago.
The crew trained for just under six months, compared to years of preparation required for professional astronauts.
They learned to withstand the g-force by going on a spin in a centrifuge, and they experienced weightlessness.
Finally, although the flight should normally be fully automated, the team has been trained by SpaceX to take control in the event of an emergency.
The crew members' sleep, heart rate, blood and cognitive functions will be analyzed during the mission in order to study how rookies react in space.
© 2021 AFP