In addition to Jared Isaacman, the mission’s commander, there are three more astronauts aboard the flight.
Hayley Arceneaux, 29, is a physician assistant at St. Jude Children’s Hospital in Memphis. Almost two decades ago, Ms. Arceneaux, who grew up in the small town of St. Francisville, La., was a patient at St. Jude when bone cancer was diagnosed in her left leg, just above the knee. Ms. Arceneaux went through chemotherapy, an operation to install prosthetic leg bones and long sessions of physical therapy.
“When I grow up, I want to be a nurse at St. Jude,” she said in a video shown at the ceremony in 2003. “I want to be a mentor to patients. When they come in, I’ll say, ‘I had that when I was little, and I’m doing good.’”
Last year, Ms. Arceneaux was hired by St. Jude. She works with children with leukemia and lymphoma.
Ms. Arceneaux could become the youngest American ever to travel to orbit. She will also be the first person with a prosthetic body part to go to space. She will be the health officer for the mission.
Sian Proctor, 51, is a community college professor from Tempe, Ariz.
Dr. Proctor, who is African American and holds a doctorate in science education, had come close to becoming an astronaut the old-fashioned way. She said that in 2009, she was among 47 finalists whom NASA selected from 3,500 applications. The space agency chose nine new astronauts that year. Dr. Proctor was not one of them.
She applied twice more and was not even among the finalists.
She still pursued her space dreams in other ways. In 2013, Dr. Proctor was one of six people who lived for four months in a small building on the side of a Hawaiian volcano, part of an effort financed by NASA to study the isolation and stresses of a long trip to Mars.
She will be the pilot on the Inspiration4 mission, the first Black woman to serve as the pilot of a spacecraft.
Christopher Sembroski, 42, of Everett, Wash., works in data engineering for Lockheed Martin. During college, Mr. Sembroski worked as a counselor at Space Camp, an educational program in Huntsville, Ala., that offers children and families a taste of what life as an astronaut is like. He also volunteered for ProSpace, a nonprofit advocacy group that pushed to open space to more people.
Mr. Sembroski described himself as “that guy behind the scenes, that’s really helping other people accomplish their goals and to take center stage.”
He’ll be the mission specialist for Inspiration4, and responsible for certain tasks during the mission.