Unlike his previous chartered flight, tech entrepreneur Jared Isaacman shared the cost with SpaceX this time around, which included developing and testing new spacesuits to see how they will hold up in the harsh vacuum.
If all goes as planned, the flight will be the first time private citizens conduct a spacewalk, but they will not venture away from the capsule.
One of the most riskiest parts of spaceflight, spacewalks have been the sole realm of professional astronauts since the former Soviet Union popped open the hatch in 1965, closely followed by the US.
Today, they are routinely done at the International Space Station.
Jared Isaacman (second right) is flying with astronauts Anna Menon, Scott Poteet and Sarah Gillis. (AP PHOTO)
Isaacman, along with a pair of SpaceX engineers and a former Air Force Thunderbirds pilot, launched before dawn aboard a SpaceX Falcon 9 rocket from Florida.
The spacewalk is scheduled for late Wednesday or Thursday, midway through the five-day flight.
But first the passengers are shooting for way beyond the International Space Station - an altitude of 1400km, which would surpass the earth-lapping record set during NASA's Project Gemini in 1966.
Only the 24 Apollo astronauts who flew to the moon have ventured further.
The plan is to spend 10 hours at that height - filled with extreme radiation and riddled with debris - before reducing the oval-shaped orbit by half.
Even at this lower 700km, the orbit would eclipse the space station and even the Hubble Space Telescope, the highest shuttle astronauts flew.
All four wore SpaceX's spacewalking suits because the entire Dragon capsule will be depressurised for the two-hour spacewalk, exposing everyone to the dangerous environment.
Isaacman and SpaceX's Sarah Gillis will take turns briefly popping out of the hatch.
Both will always have a hand or foot touching the capsule or attached support structure that resembles the top of a pool ladder.
Pilot Scott "Kidd" Poteet and SpaceX's Anna Menon will monitor the spacewalk from inside.
Like SpaceX's previous astronaut flights, this one will end with a splashdown off the Florida coast.
At a pre-flight news conference, Isaacman - CEO and founder of the credit card processing company Shift4 - refused to say how much he invested in the flight.
"Not a chance," he said.
SpaceX teamed up with Isaacman to pay for spacesuit development and associated costs, said William Gerstenmaier, a SpaceX vice-president who once headed space mission operations for NASA.
"We're really starting to push the frontiers with the private sector," Gerstenmaier said.
It's the first of three trips that Isaacman bought from Elon Musk more than two years ago, soon after returning from his first private SpaceX spaceflight in 2021.
Isaacman bankrolled that tourist ride for an undisclosed sum, taking along contest winners and a childhood cancer survivor.
Poor weather caused a two-week delay to Tuesday's launch.
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