NEW MEXICO (NYTIMES) - Soaring more than 80km into the hot, glaringly bright skies above New Mexico, Richard Branson at last fulfilled a dream that took decades to realise: He can now call himself an astronaut.

On Sunday (July 11) morning, a small rocket plane operated by Virgin Galactic, which Branson founded in 2004, carried him and five other people to the edge of space and back.

More than an hour later, Branson took the stage to celebrate. "The whole thing was magical," he said.

Branson's flight reinforces the hopes of space enthusiasts that routine travel to the final frontier may soon be available to private citizens, not just the professional astronauts of NASA and other space agencies.

Another billionaire with his own rocket company - Jeff Bezos, the founder of Amazon - has plans to make a similar jaunt to the edge of space in nine days.

In each case, billionaire entrepreneurs are risking injury or death to fulfil their childhood aspirations - and advance the goal of making human spaceflight unexceptional.

"They're putting their money where their mouth is, and they're putting their body where their money is," said Eric Anderson, chair of Space Adventures, a company that charters launches to orbit. "That's impressive, frankly."

At 8.40am Mountain time, a carrier aircraft with the rocket plane, named VSS Unity, tucked underneath, rose off the runway and headed to an altitude of nearly 14km. There, Unity was released, and a few moments later, its rocket motor ignited, accelerating the space plane on an upward arc.

Although Unity had made three previous trips to space, this was its first launch that resembled a full commercial flight of the sort that Virgin Galactic has promised to offer the general public, with two pilots - David Mackay and Michael Masucci - and four more crew members, including Branson.

This flight resembled a party for Virgin Galactic and the nascent space tourism business. Guests included Elon Musk, the founder of SpaceX; Michelle Lujan Grisham, the governor of New Mexico; and about 60 customers who have paid for future Virgin Galactic flights.

Stephen Colbert of the CBS programme The Late Show introduced segments of the webcast that included some live video from inside the spaceship. After the landing, Khalid performed a new song.

When the fuel was spent, Unity continued to coast upwards to an altitude of about 86km. The four people in back unbuckled and experienced about four minutes of floating before returning to their seats.

Branson was accompanied in the cabin by Beth Moses, the company's chief astronaut instructor; Colin Bennett, lead operations engineer; and Sirisha Bandla, vice president of government affairs and research operations.

As the space plane reentered the atmosphere, the downward pull of gravity resumed. Unity glided to a landing back at the spaceport.

Paving the way for commercial flights

For well over a decade, Branson, the irreverent 70-year-old British billionaire who runs a galaxy of Virgin companies, has said he believes that commercial flights will soon begin.

So did the 600 or so customers of Virgin Galactic who have paid US$200,000 or more for their tickets to space and are still waiting. So did the taxpayers of New Mexico who paid $220 million (S$270 million) to build Spaceport America, a futuristic vision in the middle of the desert, in order to attract Branson's company.

After years and years of unmet promises, Virgin Galactic may begin flying the first paying passengers next year after two more test flights. But with tickets costing hundreds of thousands of dollars, this experience will, for now, remain out of financial reach for most people.

Virgin Galactic's space plane is a scaled-up version of SpaceShipOne, which in 2004 captured the US$10 million Ansari X Prize as the first reusable crewed spacecraft built by a nongovernmental organisation to make it to space twice in two weeks.

Branson initially predicted commercial flights would begin by 2007. But development of the larger craft, SpaceShipTwo, stretched out.

The first SpaceShipTwo vehicle, VSS Enterprise, crashed during a test flight in 2014, killing one of the pilots. Virgin Galactic was then grounded until Unity was completed a year and a half later.

In 2019, Virgin Galactic came close to another catastrophe when a seal on a rear horizontal stabiliser ruptured because a new thermal protection film had been improperly installed.

Jeff Bezos' turn

Bezos' flight is to take place about 320km to the south-east of Spaceport America in Van Horn, Texas, where his rocket company, Blue Origin, launches its New Shepard rocket and capsule.

Although Blue Origin has yet to fly any people on New Shepard, 15 successful uncrewed tests of the fully automated system convinced the company it would be safe to put Bezos on the first flight with people aboard.

He will be joined by his brother, Mark, and Mary Wallace Funk, an 82-year-old pilot. In the 1960s, she was among a group of women who passed the same rigorous criteria that NASA used for selecting astronauts, but the space agency at the time had no interest in selecting women as astronauts. A fourth unnamed passenger paid US$28 million in an auction for one of the seats.

Neither Blue Origin nor Virgin Galactic flights go high enough or fast enough to enter orbit around Earth. Rather, these suborbital flights are more like giant roller coaster rides that allow passengers to float for a few minutes while admiring a view of Earth against the black backdrop of space.

Bezos' company emphasised the rivalry with Virgin Galactic for space tourism passengers in a tweet Friday. Blue Origin highlighted differences between its New Shepard rocket and Virgin Galactic's SpaceShipTwo, including the fact that New Shepard flies higher, above the altitude of 100km, that is often regarded as the boundary of space. However, the US Air Force and the Federal Aviation Administration set the boundary at about 80km.

The company also noted the size of the New Shepard capsule's windows and called Virgin Galactic's Unity "a high-altitude plane" in contrast to New Shepard's rocket.

Bezos on Sunday congratulated Branson and his fellow crew on their flight.

"Can't wait to join the club!" he added in an Instagram post.

Blue Origin has not yet announced a ticket price, and Virgin Galactic's earlier quoted fare of US$250,000 may rise. But Sunday, after his trip, Branson announced a sweepstakes that will give away two seats on a future Virgin Galactic flight.

Future rides to space

Joy-riding tourists will not be the only passengers on future suborbital flights. Both companies are selling flights to organisations including the Italian air force, where scientists will conduct experiments that take advantage of the minutes of microgravity.

The era of nonprofessional astronauts regularly heading to orbit may also begin in the coming year.

Jared Isaacman, a 38-year-old billionaire, is essentially chartering a rocket and spacecraft from SpaceX for a three-day trip to orbit that is scheduled for September.

In December, Space Adventures has arranged for a Japanese fashion entrepreneur, Yusaku Maezawa, and Yozo Hirano, a production assistant, to launch on a Russian Soyuz rocket on a 12-day mission that will go to the International Space Station.

Another company, Axiom Space in Houston, is arranging a separate trip to the space station that will launch as soon as January.

The orbital trips are too expensive for anyone except the superwealthy - Axiom's three customers are paying US$55 million each - while suborbital flights might be affordable to those who are merely well off.

But how many people are willing to spend as much as some houses cost for a few minutes of space travel?

Carissa Christensen, founder and chief executive of Bryce Space and Technology, an aerospace consulting firm, thinks there will be plenty.

"Based on previous ticket sales, surveys and interviews," she said in an email, "we see strong demand signals for multiple hundreds of passengers a year at current prices, with potential for thousands if prices drop significantly."

Anderson of Space Adventures is less certain.

"Per minute, it's like a thousand times more expensive than an orbital flight," he said. "It's crazy."

Two decades ago, Space Adventures did sell suborbital flights, including a ticket to Funk, who goes by Wally.

"Wally Funk was one of our first customers," Anderson said. "That would have been, like, 1998." The ticket price then was US$98,000.

At one point, about 200 people signed up for suborbital flights, but none of the promised suborbital rocket companies was able to get their space planes close to flight. Space Adventures returned the money to Funk and the others.

Now this unproven suborbital market has whittled down to a battle of billionaires - Branson and Bezos.

"If anybody can make money and make the market work for suborbital, it's Branson and Bezos," Anderson said. "They have the reach and the cachet."