Isaacman, 38, gathered a unique group of individuals for the mission through three ways: from St. Jude's staff, through an entrepreneurial competition, and via a charity lottery.

The Inspiration4 commander founded his payment processing company in 1999 when he was 16. He's also an avid pilot, with a variety of ratings in commercial and military jets. He has flown in more than 100 airshows and is co-founder of Draken International, a private aerospace company that helps train pilots for the U.S. military.

Hayley Arceneaux, a cancer survivor and now a physician assistant at St. Jude, is the mission's medical officer. She survived osteosarcoma, a type of bone cancer, at age 10 and will be the first person to fly in space with a prosthetic body part — as a significant portion of her leg is metal. At 29, Arceneaux will also become the youngest American to fly in space.

Sian Proctor, 51, the Inspiration4 pilot, joined the crew after winning an online business competition through Isaacman's company. She is a geoscientist and science communication specialist, with a passion for space exploration that extends back to her childhood: She was born in Guam while her father worked for a NASA ground station during the Apollo missions. Proctor is an analog astronaut, having completed multiple Earth-based missions that simulate the isolation of living in space. In 2009, Proctor was a finalist for NASA's 2009 astronaut selection

Chris Sembroski, the mission specialist, donated to the St. Jude fundraising campaign and was selected from among nearly 72,000 entries. Sembroski, 42, is a Lockheed Martin engineer and an Air Force veteran who served in Iraq.