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Farnborough, England (CNN) -- Virgin chief Richard Branson has put a time frame on his plan to launch tourists into space, claiming he and his family will blaze a trail for hundreds of fare-paying passengers by blasting off in December 2013.

Branson also announced that Virgin Galactic, his fledgling commercial space company, was expanding to include a satellite-launching service that would use a low-cost rocket system to propel payloads into orbit.

Speaking at the UK's Farnborough International Airshow, the British entrepreneur said his adult children, Holly and Sam, would accompany him on board the SpaceShipTwo on its pioneering two-hour voyage into sub-orbital space.

"It'll certainly be the most momentous moment of my life and my children's lives," Branson told CNN. "It'll be very difficult to ever cap it I think. Anyone who has ever been into space says the same thing."

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Some 529 would-be astronauts, including celebrities such as Ashton Kutcher, have so far signed up for $200,000-a-seat flights which will last two hours.

Virgin executives said the figure was a milestone as it exceeds the existing number of space veterans. Six hundred are expected to fly in the first two years of service.

Launched from a carrier vessel known as WhiteKnightTwo, Virgin Galactic's space ship can carry two pilots and six passengers. SpaceShipTwo is currently undergoing testing in the Mojave Desert in California, although a replica was on display at Farnborough.

Branson acknowledged the existing price tag means that his goal of opening space travel up to ordinary people was some way off. He insisted, however, that it would drop over the next few decades as Virgin's space ambitions went further.

"The initial flights will be sub-orbital, which will give people a taste of space," he said. "From there we'll go into orbital flights and maybe one day hotels in space."

Outlining details of his new satellite service, LauncherOne, Branson said the two-stage rocket would also be carried into launching position by WhiteKnightTwo.

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He said the service, capable of launching 500-pound payloads, would drastically reduce the cost of putting satellites into orbit. This, he said would open up the market to researchers, small businesses and even schools.

Several clients have already signed up for the service including Earth observation company GeoOptics and Planetary Resources, an asteroid mining company which counts Google founders Eric Schmidt and Larry Page, and movie director James Cameron as investors.

Virgin Galactic's commercial director Stephen Attenborough told CNN that the goal was to be able to offer a reliable satellite launch system for $10 million, a price tag he says undercuts existing services by up to 50%.

George Whitesides, the company's chief executive and president, said: "This will radically revolutionize the small satellite business in the way we have the space tourism business."

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But Branson insisted his chief aim was to open space to researchers studying the "global crisis" of climate change.

"In America you've got a lot of skeptics about global warming, what you need is the scientific evidence that it is there one way or the other," he said.

"The majority of scientists believe we have a problem, we need to know that conclusively and we need to work towards resolving it and I think LauncherOne will make it clear one way or the other, and sadly I think it'll be the other."

On the sidelines of Wednesday's announcement, Virgin Galactic officials offered more details of what customers can expect for their money.

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Whitesides said astronauts on board SpaceShipTwo would experience a little less than five minutes of weightlessness, during which time they will be free to unclip their seat harnesses and float within the cabin.

"Some people will want to focus their time looking out of the vehicle, looking down at the planet or Milky Way, whereas others may want to do spins or tricks," Whitesides told CNN.

"There's one guy who wants to assume a neutral position, close his eyes and get back to the womb.

"My big concern is getting people back to their seats. This is one of the central design considerations. My guess is it will be as simple as saying 'OK everybody; get back in your seats. Then gravity will kick in."

Branson, meanwhile, confessed he hadn't yet planned his time in space. "I'm sure we will do something but we haven't got that far thinking about it. If we're allowed to put up a flag up there... who knows?"

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Adam Wells, Virgin Galactic's head of design, said the cabin's interior was being kept as minimal as possible to reduce weight and maximize space for floating. There are unlikely to be comforts familiar to airline passengers. Television screens will probably be too heavy -- and there will be no toilet.

"The intent is to keep the volume as uncluttered as possible," he told CNN. "From an ideal standpoint we want everything, including the seats to disappear, which is a fascinating design challenge."

Among would-be astronauts attending Wednesday's announcement was Portuguese diplomat Angelo Araujo.

Araujo, 62, described his journey into space as a "spiritual journey" during which he would pay homage to his late father, a poet and composer also called Angelo Araujo.

"As we age and we approach the end, we are part of the universe and I think it's wonderful to see it from another angle.

"I want to read some poetry from my father. He will be the first Portuguese poet to be read in space.

Perry Sporn, a jeweler from Burlington, Vermont, who will be among the first 500 to fly said the $200,000 price tag was money well spent.

"I was a poor kid but I had an amazing opportunity to be productive and make a good living, so to me it's a ridiculously small sum."

As Virgin Galactic's chief pilot, David Mackay is likely to helm the first flights and may even break records for space travel as he clocks up at least one voyage per week when the service is up and running.

"I'm not on some ego trip to enjoy the greatest number of space flights," he told CNN. "If it's successful, it will eventually become much more common and whatever record I set will quickly be broken."