SpaceX's latest bold mission has sent four commercial astronauts rocketing to heights higher than any human has reached since the end of NASA's Apollo moon missions 50 years ago.

The Polaris Dawn crew were finally able to embark early Tuesday on the thrice-delayed spaceflight, where by Thursday they should attempt to become the first nongovernment astronauts to conduct a spacewalk. In the predawn hours, billionaire entrepreneur Jared Isaacman and his crew boarded a SpaceX Dragon capsule perched atop a Falcon 9 rocket, which lifted off at 5:23 a.m. EDT from NASA's Kennedy Space Center in Florida.

Ahead for the private astronauts – who spent three weeks in quarantine awaiting the launch – are five days in orbit testing out SpaceX technology that could be crucial for future deep-space exploration.

If you missed the launch, here's how to rewatch SpaceX's Polaris Dawn mission get underway.

SpaceX launches Polaris Dawn on Falcon 9

The highly-anticipated launch followed about two weeks of delays as SpaceX awaited the ideal time to schedule a launch opportunity.

The spacecraft will ascend to 870 miles above Earth's surface before descending to a cruising orbit about 435 miles above Earth.

That initial altitude is higher than any human has traveled since NASA’s Apollo lunar program came to an end in the 1970s and is more than three times higher than the International Space Station. The ascent will also take the crew through the treacherous inner regions of Earth's Van Allen radiation belts, which astronauts will have to traverse on future missions to the moon and Mars.

SpaceX will track the crew's journey on X and its website.

SpaceX launch:Polaris Dawn crew looks to make history with civilian spacewalk

Photos show historic crewed launch from Florida

In the pre-dawn hours, spectators gathered all over the Florida coast to watch the daring mission get underway from launch Complex 39A at the NASA facility in Cape Canaveral.

Following Tuesday's launch, the Falcon 9 rocket's first-stage booster was able to detach from the spacecraft within 10 minutes, guide itself back to Earth and land as planned aboard a drone ship in the Atlantic Ocean. By 5:40 a.m., the Dragon spacecraft broke away from the Falcon 9's upper stage and began using its own thrusters to power on, SpaceX said on social media site X.

What is the Polaris Dawn mission?

Polaris Dawn is the first of three human spaceflights under the Polaris Program, all of which are intended to test SpaceX technologies needed to carry humans deep into the cosmos.

Years in the making, the launch was most recently scrubbed due to poor weather conditions forecasted for the crew's return to Earth. Because the Dragon is not docking at the International Space Station, its crew will be entirely reliant on the oxygen and supplies they have stored on the spacecraft, which is only enough for about a week, Isaacman previously explained on social media site X.

For that reason, SpaceX had been waiting for the past several days for weather conditions to improve off the Florida coast, where the crew will make a splashdown landing on the sixth day of their mission.

Isaacman, who helped to fund the mission along with Elon Musk's SpaceX, is the only member of the Polaris Dawn crew to have been to outer space before. The billionaire founder of internet company Shift4 Payments is mission commander of a crew that includes pilot Scott “Kidd” Poteet as well as mission specialists Sarah Gillis and Anna Menon, who is also the medical officer.

The crew will spend five days in orbit testing space technology on behalf of SpaceX that could prove crucial as NASA and other space agencies set their sights on destinations like Mars.

On the third day of the mission, the crew will also attempt to become the first-ever private citizens to conduct a spacewalk, opening the Dragon's hatch to expose themselves to the vacuum of space. The daring maneuver is one only ever conducted by government astronauts, and most commonly takes place of spacecraft with airlocks.

Because the Dragon does not have an airlock, the entire spacecraft will have to be depressurized when the hatch is opened, exposing the entire crew to the vacuum of space. All four astronauts will be wearing extravehicular activity (EVA) suits designed by SpaceX to receive oxygen through tethers, which they will test on behalf of the company.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]