British tycoon Richard Branson said on Wednesday his children would join him on the first of his Virgin Galactic space flights, as he unveiled a new satellite launching service.

Outlining his plans at the Farnborough Air Show in southwest England, the billionaire entrepreneur said he and his adult son Sam and daughter Holly hoped to make the journey on the SpaceShipTwo, or SS2, aircraft by the end of 2013.

The WhiteKnightTwo aircraft that will help launch SS2 into space will also be used for a new launch vehicle, LauncherOne, which will take small satellites into space for around one tenth of the present cost, Branson said.

"Obviously this is the most exciting adventure I have ever undertaken," the Virgin Galactic founder said.

"It's both an entrepreneurial and personal adventure in being able to build a spaceship and ask my children to come along who can also enjoy it. It's every boy's dream."

Branson unveiled a full size replica of SS2 at the show.

In all, 529 people have put down a deposit to clinch a space on the 60-mile, two-hour ride into space, at a cost of £128,000 ($200,000, 162,000 euros) each. Around 120 of them were at the Branson event in Farnborough.

Actor Ashton Kutcher and scientist Stephen Hawking are among the aspiring astronauts who have signed up to join the programme when it gets under way in late 2013 to early 2014, according to Branson.

Irish businessman and author Bill Cullen, 70, was the first to sign up for a trip, in 2004.

"I wanted to be the first Irishman in space and I'm really looking forward to it, he said. "I've been interested in space ever since I followed comic hero Dan Dare when I was a kid."

The flights are expected to start from Spaceport America in New Mexico with plans afoot to build a second spaceport in Abu Dhabi, United Arab Emirates.

"Virgin Galactic's goal is to revolutionise the way we get to space," Branson said. "I'm immensely proud of what we have already achieved as we draw near to regular suborbital flights on SpaceShipTwo."

The WhiteKnightTwo, a large twin-fuselage aircraft joined by a central wing, will launch the SS2 craft -- which carries two pilots and six passengers -- at approximately 50,000 feet (15,240 metres).

Once separated from the mothership, the vehicle will ignite its hybrid rocket and fly to the edge of space before gliding back to perform a conventional runway landing.

Passengers will be able to experience a brief period of weightlessness as its flight path overlaps Earth's upper atmosphere.

In a separate enterprise, LauncherOne is expected to begin commercial operations in 2016 and can carry up to 227 kilos (500 pounds) of weight for prices below $10 million (£642,500).

Branson said LauncherOne would bring satellite launch "into the realm of affordability" for organisations ranging from national space agencies to new businesses and even schools.

"It will be a critical new tool for the global research community, enabling us all to learn about our home planet more quickly and affordably," he said.

Virgin Galactic CEO George Whitesides said there was a high demand for a satellite launching service despite the difficult economic climate.

"Miniaturised satellite components and constrained budgets are driving commercial clients, academic users and government agencies all to clamour for an affordable, dedicated launch vehicle," he said.