By Marcia Dunn / Associated Press

CAPE CANAVERAL, Fla. — SpaceX’s first private flight blasted off Wednesday night with two contest winners, a health care worker and their rich sponsor, the most ambitious leap yet in space tourism.

It was the first time a rocket streaked toward orbit with an all-amateur crew — no professional astronauts.

The Dragon capsule’s two men and two women are looking to spend three days circling the world from an unusually high orbit — 100 miles higher than the International Space Station — before splashing down off the Florida coast this weekend.

Leading the flight is Jared Isaacman, 38, who made his fortune with a payment-processing company he started in his teens.

It’s SpaceX founder Elon Musk’s first entry in the competition for space tourism dollars. Isaacman is the third billionaire to launch this summer, following the brief space-skimming flights by Virgin Galactic’s Richard Branson and Blue Origin’s Jeff Bezos in July.

Joining Isaacman on the trip dubbed Inspiration4 is Hayley Arceneaux, 29, a childhood cancer survivor who works as a physician assistant where she was treated — St. Jude Children’s Research Hospital in Memphis, Tennessee. Isaacman has pledged $100 million out of his own pocket to the hospital and is seeking another $100 million in donations.

Also along for the ride: sweepstakes winners Chris Sembroski, 42, a data engineer in Everett, and Sian Proctor, 51, a community college educator in Tempe, Arizona.

Sembroski, a former Air Force missile technician who moved to Everett in 2007, is a reliability engineer with Lockheed Martin who works from home. He entered an open lottery by donating to St. Jude Children’s Research Hospital. He didn’t win, but a friend from his college days did and gave him the slot. He is married to Erin Duncan-Sembroski, an English teacher at Explorer Middle School south of Everett, and the couple has two girls.

Arceneaux is set to become the youngest American in space and the first person in space with a prosthesis, a titanium rod in her left leg.

The recycled Falcon rocket soared from the same Kennedy Space Center pad used by the company’s three previous astronaut flights for NASA. But this time, the Dragon capsule aimed for an altitude of 357 miles (575 kilometers), just beyond the Hubble Space Telescope.

Their fully automated capsule has already been to orbit: It was used for SpaceX’s second astronaut flight for NASA to the space station. The only significant change is the large domed window at the top in place of the usual space station docking mechanisms.

Isaacman, an accomplished pilot, persuaded SpaceX to take the Dragon capsule higher than it’s ever been. Initially reluctant because of the increased radiation exposure and other risks, SpaceX agreed after a safety review.

“Now I just wish we pushed them to go higher,” Isaacman told reporters on the eve of the flight. “If we’re going to go to the moon again and we’re going to go to Mars and beyond, then we’ve got to get a little outside of our comfort zone and take the next step in that direction.”

Isaacman, whose Shift4 Payments company is based in Allentown, Pennsylvania, is picking up the entire tab for the flight but won’t say how many millions he paid. He and others contend those big price tags that will eventually lower the cost.

“Yes, today you must have and be willing to part with a large amount of cash to buy yourself a trip to space,” said Explorers Club President Richard Garriott, a NASA astronaut’s son who paid the Russians for a space station trip more than a decade ago. “But this is the only way we can get the price down and expand access, just as it has been with other industries before it.

Though the capsule is automated, the four Dragon riders spent six months training for the flight to cope with any emergency. That training included centrifuge and fighter jet flights, launch and reentry practice in SpaceX’s capsule simulator and a grueling trek up Washington’s Mount Rainier in the snow.

Four hours before liftoff, the four emerged from SpaceX’s huge rocket hangar four hours before liftoff, waving and blowing kisses to their families and company employees, before they were driven off to get into their sleek white flight suits. Once at the launch pad, they posed for pictures and bumped gloved fists, before taking the elevator up. Proctor danced as she made her way to the hatch.

Unlike NASA missions, the public won’t be able to listen in, let alone watch events unfold in real time. Arceneaux hopes to link up with St. Jude patients, but the conversation won’t be broadcast live.

SpaceX’s next private trip, early next year, will see a retired NASA astronaut escorting three wealthy businessmen to the space station for a weeklong visit. The Russians are launching an actress, film director and a Japanese tycoon to the space station in the next few months.

Once opposed to space tourism, NASA is now a supporter. The shift from government astronauts to non-professionals “is just flabbergasting,” said former NASA Administrator Charles Bolden, a former space shuttle commander.

“Someday NASA astronauts will be the exception, not the rule,” said Cornell University’s Mason Peck, an engineering professor who served as NASA’s chief technologist nearly a decade ago. “But they’ll likely continue to be the trailblazers the rest of us will follow.”