Decades after burnishing his reputation as a wealthy daredevil mogul in a series of boating and hot-air balloon expeditions, Richard Branson is poised to promote his burgeoning astro-tourism venture by launching himself to the final frontier.

Branson's Virgin Galactic Holding Inc (SPCE.N) is due on Sunday to send the company's passenger rocket plane, the VSS Unity, on its first fully crewed test flight to the edge of space, with the British billionaire founder among the six individuals strapping in for the ride.

The gleaming white spaceplane will be borne by a twin-fuselage carrier jet dubbed VMS Eve (named for Branson's mother) to an altitude of 50,000 feet, where Unity will be released and soar by rocket power in an almost vertical climb through the outer fringe of Earth's atmosphere.

At the apex of its flight some 55 miles (89 km) above the New Mexico desert, the crew will experience a few minutes of weightlessness before making a gliding descent back to Earth.

If all goes according to plan, the flight will last about 90 minutes and end where it began - on a runway at Spaceport America near the aptly named town of Truth or Consequences.

Virgin's Unity 22 mission marks the 22nd test flight of the spacecraft, and the company's fourth crewed mission beyond Earth's atmosphere.

But it will be the first to carry a full complement of space travelers – two pilots and four "mission specialists," Branson among them.

MILESTONE AND PUBLICITY

Although the mission is seen as a potential milestone in helping transform citizen rocket travel into a mainstream commercial venture, spaceflight remains an inherently hazardous endeavor.

An earlier prototype of the Virgin Galactic rocket plane crashed during a test flight over California's Mojave Desert in 2014, killing one pilot and seriously injuring another.

If successful, Sunday's flight will also give Branson bragging rights to besting rival Jeff Bezos and his space company, Blue Origin, in what has been popularized as a "billionaire space race." Bezos, founder of online retail giant Amazon.com, is slated to fly aboard Blue Origin's suborbital rocketship, the New Shepard, later this month.

Branson's official job on his flight is to "evaluate the private astronaut experience," and his observations will be used to "enhance the journey for all future astronaut customers," according to Virgin's press materials.

Sir Richard Branson stands on the floor of the New York Stock Exchange (NYSE) ahead of Virgin Galactic (SPCE) trading in New York, U.S., October 28, 2019. REUTERS/Brendan McDermid
But Marco Caceres, a senior space analyst for the Virginia-based consulting firm Teal Group, said the Branson and Bezos ride-alongs were each "a bit of a publicity stunt."

"If they succeed, their ventures will be taken more seriously," Caceres said. "There's plenty of multimillionaires in the world that would like to go up on an adventure, so long as they see it as relatively safe."

Virgin Galactic and Blue Origin, along with fellow billionaire entrepreneur Elon Musk's SpaceX, are competing head-to-head in the emerging business of space tourism, though Musk has a big head start.

SpaceX, which plans to send its first all-civilian crew (without Musk) into orbit in September, has already launched numerous cargo payloads and astronauts to the International Space Station.

Branson, 70, insists there is plenty of demand from wealthy would-be citizen astronauts to go around, and that he had no intention of trying to upstage Bezos.

'NOT A RACE'

"It's honestly not a race," Branson told Reuters in an interview earlier this week. "If it's a race, it's a race to produce wonderful spaceships that can make many more people be able to access space. And I think that's both of our aims."

The spaceplane's two pilots, Dave Mackay and Michael Masucci, will control the ignition and shutoff of the ship's rocket engine, and activate the vehicle's "feathered" tail maneuver for re-entry.

The three other mission specialists are Beth Moses, the company's chief astronaut instructor; Virgin Galactic's lead operations engineer Colin Bennett; and Sirisha Bandla, a research operations and government affairs vice president.

The Virgin brand, including Branson's airline and former record label, has long been associated with exploits of derring-do by its flamboyant founder. Branson set a new record for the fastest boat crossing of the Atlantic in 1986, a year after his initial attempt ended with a Royal Air Force helicopter rescue when his vessel capsized.

In 1987 he made a record-breaking Atlantic crossing by hot-air balloon, though again he had to be rescued from the sea. He went on to break at least two other air-balloon speed records but failed to complete any of three bids to circumnavigate the globe by balloon.

As for Sunday's flight, Branson said this week that he is excited, "and I really don't think there’s anything there to be scared about."

Assuming the mission goes well, Virgin has said it plans two further test flights of the spaceplane before beginning commercial service next year.

The company has said it has received more than 600 flight reservations, priced at around $250,000 per ticket, but hopes eventually to slash the cost of each seat to $40,000.

Reporting by Steve Gorman in Los Angeles; Additional reporting by Kevin Fogarty in Washington; Editing by Daniel Wallis