SpaceX to send 1st all-civilian crew into orbit for 3 days

SpaceX's Inspiration4 mission may sound familiar, as another billionaire-backed space launch, but it's going where neither Richard Branson nor Jeff Bezos could -- into orbit.

Branson's Virgin Galactic and Bezos' Blue Origin sent civilians into space on brief, suborbital flights that lasted only for a few minutes.

But Elon Musk's SpaceX is just days away from sending its first all-civilian crew on a three-day mission around the Earth multiple times.

Inspiration4 will orbit 360 miles above Earth, higher than the International Space Station, with no professional astronaut on board. It will be the first orbital space tourism flight that doesn't have an astronaut to guide the passengers through launch and landing.

Commanding the mission is 38-year-old billionaire Jared Isaacman, an experienced pilot. He founded a payment process company called Shift4 Payments and purchased all four seats on the flight for roughly $200 million.

Isaacman wants this launch to benefit St. Jude Children's Research Hospital. He has already donated $100 million to the cause, and raised an additional $13 million through a lottery to win a seat.

One seat was reserved for a St. Jude ambassador -- 29-year-old Hayley Arceneaux.

Arceneaux is a bone cancer survivor who was treated at St. Jude's as a child and now works there as a physician assistant. She will be the youngest American to go to space as well as the first person with a prosthesis.

Joining Arceneaux and Isaacman on their journey is Chris Sembroski, 41, and Dr. Sian Proctor, 51.

Proctor said she has dreamed of going to space since she was a child. She once applied to become a NASA astronaut and made it to the final 47 out of 3,500 applicants, but was cut from the final round. She burst into tears when she heard she was chosen as a member of the Inspiration4 mission.

Sembroski is an Iraq War veteran and engineer with Lockheed Martin, who won the final seat through the lottery that required a St. Jude donation to enter.

The crew has gone through partial- and full-mission simulations and has been trained by SpaceX on "the Falcon 9 launch vehicle and Dragon spacecraft, including a specific focus on orbital mechanics, operating in microgravity, zero gravity, and other forms of stress testing," according to an Inspiration4 release.

They will launch from Pad 39A at NASA’s Kennedy Space Center in Florida -- the same launch pad that Apollo 11 blasted off from -- sending man to the moon for the first time.

Inspiration4 is targeting a launch no no earlier than 8 p.m. ET on Sept. 15. Since they aren't going to the International Space Station, they don’t need to launch at any specific time.

The crew is planning to bring items on board the Crew Dragon spacecraft to auction off to benefit St. Jude, including artwork from patients.

After three days of orbiting Earth, they will prepare to splashdown in the Atlantic Ocean off the coast of Florida.

ABC News' Gio Benitez contributed to this report.