Space tourism companies are aiming to send their customers into orbit on beefed-up versions of existing spacecraft designs. Some companies claim their spaceships could even ferry government astronauts to the International Space Station after NASA retires the space shuttle in 2010.
The UK company Virgin Galactic has already announced plans to launch paying customers to the edge of space in 2008 on a suborbital craft called SpaceShipTwo. Now, it says it will develop a spacecraft to orbit the Earth if all goes well with those suborbital flights, which will initially cost $200,000.
"If the SpaceShipTwo service is successful, we will develop SpaceShipThree, which is orbital," the president of Virgin Galactic told Flight International.
The design is likely to be a more powerful version of the nine-person SpaceShipTwo, which itself is based on the trail-blazing vehicle SpaceShipOne designed by Burt Rutan of Scaled Composites in Mojave, California, US.
SpaceShipOne won the $10 million Ansari X Prize for private spaceflight in October 2004 and carried the weight of three people, including the pilot. The craft's rockets were ignited in mid-air after being lifted to a height of about 14 kilometres by a carrier airplane.
Suborbital space only requires the spaceships to reach three times the speed of sound, or Mach 3. But for orbital flights, they must reach Mach 25 and be able to withstand the intense heat of re-entry into the atmosphere.
But that may not be such a big hurdle, says Jim Benson, founder and CEO of SpaceDev of Poway, California, US. SpaceDev helped develop and build SpaceShipOne's "hybrid" motor, which burned liquid laughing gas and solid rubber. He says the company had to scale the motor's thrust up by a factor of 1000 to prepare for the SpaceShipOne flights.
To get to Mach 25, it has to scale up its most powerful motor by only a factor of four - to provide a total of about 454,000 kilograms of thrust. "It's not that difficult," he says.
SpaceDev is also working on its own spacecraft to reach orbit. It will be based on an existing - but as yet unnamed - design for an orbital space plane that had already been developed by NASA and the US military.
Capable of carrying six people into orbit, it will launch vertically and glide to a horizontal landing, unlike the probable design of SpaceShipThree. "The only feasible way to reach orbit is to take off vertically from the ground and go straight up," says Benson. After punching above most of the atmosphere, it will tilt over and accelerate to Mach 25, he says.
Benson claims that with enough funding, the company could begin its orbital flights in 2010. That is when NASA is scheduled to retire its space shuttles. It is also the target date for its next-generation spacecraft, called the Crew Exploration Vehicle (CEV), to begin flying.
NASA has yet to announce the requirements for the CEV, but two main consortia, one led by Lockheed Martin and the other by Northrop Grumman and Boeing, are bidding to build it.
"I have very little faith in the usual suspects - the giant aerospace companies - in meeting any schedule or cost estimates," says Benson. "There's a tremendous opportunity for smaller companies to jump into the fray and come up with more cost-effective alternatives."
He says SpaceDev's orbital vehicle could carry six people to the International Space Station for a NASA mission, or could take tourists around the Earth or to a space hotel being developed by Bigelow Aerospace of Las Vegas, Nevada, US. A prototype about one-third the size of the future hotel is set to blast into space in late 2005 or early 2006.
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