One of the most ambitious space tourism missions in history has launched, with the all-commercial crew set to hit a number of milestones during its five days in space, including the first-ever privately funded human space walk.

The mission, called Polaris Dawn, took off from NASA’s Kennedy Space Center in Florida today, Tuesday, September 10, at 5.23 am Eastern Time. The four-person crew, traveling inside a SpaceX Crew Dragon vehicle atop one of the California company’s Falcon 9 rockets, comprises Jared Isaacman, the billionaire who funded the mission, SpaceX engineers Sarah Gillis and Anna Menon, and pilot Scott Poteet.

Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, says the mission’s pioneering space walk is a “gimmick” in some respects. “But if you look at it as developing the capability, independent of NASA, to do space walks, that is potentially important,” he says.

Initially set to launch at the end of August, Polaris Dawn was pushed back first due to technical concerns and weather, and later because of a botched landing of another Falcon 9 rocket, which resulted in the Federal Aviation Administration (FAA) temporarily grounding the Falcon 9 fleet. The crew remained in quarantine for the duration but kept busy with additional training.

Post-launch, the Crew Dragon spacecraft was placed into an orbit that will take it as high as 1,400 kilometers above Earth’s surface, making this the farthest astronauts will have traveled from Earth since the Apollo 17 mission to the moon in 1972, and the highest altitude ever achieved by a woman. “This is the farthest humans have traveled since the last time humans walked on the moon,” Isaacman said in a prelaunch briefing at the Kennedy Space Center on August 19.

Isaacman, the CEO of the US payment firm Shift4, flew to space previously in September 2021 on the Inspiration4 mission. That mission, which also ran on a SpaceX Crew Dragon vehicle, at a cost of somewhere up to $200 million, showcased the ability of SpaceX to allow the ultrarich to pay for the ultimate thrill, a trip to orbit as a space tourist. (The cost of the Polaris Dawn mission has not been revealed.)

Space tourism missions have happened multiple times before, beginning in 2001 when the US businessman Dennis Tito became the first paying customer aboard a Russian Soyuz capsule to the International Space Station (ISS). In the past few years, dozens of paying customers of companies such as Virgin Galactic and Blue Origin have also taken brief suborbital “hops” into space lasting minutes.

But Crew Dragon, partially funded by nearly $5 billion of NASA money to ferry astronauts to and from the ISS in the wake of the space shuttle’s retirement in 2011, brings a whole new angle to such missions. The vehicle, about as roomy as a large car with accommodation for up to seven passengers, can launch bespoke flights to Earth orbit, not just to the ISS, and enable new types of missions.

“Isaacman is working to make commercial spaceflight about science and exploration and to dispel the notion that it is just thrill-seeking and adventure tourism,” says Jordan Bimm, a historian of science at the University of Chicago. Earlier this month, SpaceX also revealed that it would launch a first-ever mission over Earth’s poles—not featuring Isaacman—on Crew Dragon in late 2024.

SpaceX’s goal is to use these missions to kick-start its own era of human spaceflight. Elon Musk, the company’s CEO, has made no secret of the fact that his ultimate goal is to make humans multi-planetary and send the first people to live on Mars in the coming years with a large new rocket his company is developing. Called Starship, the rocket is already contracted with NASA to begin human landings on the moon in 2026.

To that end, Polaris Dawn is designed as an early foray into more ambitious private human spaceflights, with the mission—delayed from an initial planned launch date in November 2022—also intended to raise millions of dollars in charitable funds through sponsorship deals and donations for the St. Jude Children’s Research Hospital in the US. The crew went into quarantine a week before the launch, to ensure they remained healthy ahead of the flight.

The attempt at the high orbit of 1,400 kilometers will occur just hours into the mission, and it is intended to eclipse the record for the highest nonlunar orbit of Earth, set at 1,370 kilometers by NASA’s Gemini 11 spacecraft in September 1966. The flight will touch “the inner regions of Earth’s Van Allen radiation belt” said Menon in the briefing.

The peak of the spacecraft’s orbit will then be lowered to 700 kilometers. On the second day in space, the crew will prepare for the space walk, which will include readying their sleek new extravehicular activity suits designed by SpaceX. On the third day, the space walk will be attempted.

Although not confirmed, Isaacman and Gillis are believed to be the two crewmembers who will actually leave the spacecraft’s hatch and enter space. However, the entire spacecraft will need to be depressurized, and the whole crew will be suited, with a “pre-breathe” protocol needed to remove nitrogen from the astronaut’s bodies to “reduce [the] risk of decompression sickness,” Gillis said in the briefing, noting that the crew had spent two days at NASA’s Johnson Space Center in Houston to prepare for the process. Separately the team have also trained for thousands of hours for the mission, including in simulators, have completed physical training, and have worn the suits for more than 100 hours on the ground.

Isaacman and Gillis will not detach from the spacecraft and float freely in space. However, they will fully exit the craft using a series of rails, dubbed “Skywalker,” installed at the hatch, while remaining attached to the vehicle with a 12-foot-long tether. The duo will remain in contact with Crew Dragon but will have a “hands-free demonstration” where only their feet are touching, said Isaacman.

Leroy Chiao, a former NASA astronaut who performed six space walks, says the duo can expect to see a “spectacular view of Earth and the horizon” that is immensely better than looking through the spacecraft’s window, along with a flood of emotions. “When I’ve been outside on every one of my space walks, I have this heightened sense of what I’m doing,” he says. “I’m hyper-aware of every single thing.”

He notes that safety will be paramount for the spacewalkers. “My advice would be to triple-check everything, go slow, and enjoy it,” he says. “You want to make sure your tether’s attached—getting flung out into space is every spacewalker’s worst nightmare. That’s the secret fear of all spacewalkers, whether we admit it or not.”

The space walk, which will be livestreamed to Earth on X, is expected to last about two hours. A number of scientific experiments will also be conducted during the mission, including tests of how humans react to short-duration spaceflights like this, as opposed to months-long stays on the ISS—such as that of the two NASA astronauts who found their eight-day trip on Boeing’s Starliner become an eight-month stay due to problems with the spacecraft.

The mission will end on its fifth day by splashing down off the coast of Florida in the Atlantic Ocean or the Gulf of Mexico, where it will be picked up by a ship, with the crew returned to land. Isaacman then hopes to launch a second Polaris Dawn mission on Crew Dragon in the coming years, possibly a mission to boost NASA’s Hubble Space Telescope—although Isaacman was coy about that prospect, and NASA has not yet given its approval.

The Polaris program will end with a third mission that will be the first crewed flight of Starship. If Isaacman and Musk get their way, that might well be the start of an even more ambitious era of human spaceflight where it is not just billionaires clinging to the sides of spacecraft. “There’s going to be an armada of Starships arriving on Mars at some point in the future,” Isaacman said in the briefing. “And people are going to have to be able to get out and walk around.”