On April 7, Hungarian-born billionaire software engineer Charles Simonyi will board a Russian Soyuz spaceship bound for the International Space Station, poised to become one of only a handful of civilians to fly into orbit around the Earth.

Billionaire Charles Simonyi, 58, right, who is scheduled to be the next space tourist, shakes hands with his future crew members, Russian cosmonauts, Oleg Kotov, centre, and Fyodor Yurchikhin, during a news conference in Star City outside Moscow, Thursday, March 22, 2007. (Sergey Ponomarev/Associated Press)

All the former Microsoft executive, 58, had to do was train for six months with Russian cosmonauts on the basics, from learning to walk and breathe in a spacesuit to coping with dizziness in space. That and write a cheque for $20 million US.

For a previous generation of millionaires, the literal summit of achievement was climbing Mount Everest. But the mountain first conquered by Sir Edmund Hillary and Tenzing Norgay in 1953 is now littered with tourists and is no longer an exclusive club.

Space exploration, on the other hand, remains both prohibitively costly and dangerous enough that only a few civilians have been given the chance to make the attempt.

Can anyone with $20 million US get to the space station?

In April 2001, Dennis Tito became famous as the world's first "space tourist," paying his own way on a Russian Soyuz spacecraft to spend a week on the International Space Station.

Tito underwent extensive cosmonaut training and medical tests in Russia to ensure his fitness before going to the space station. He agreed to replace any equipment he broke and to stay mainly in the Russian part of the station, though NASA allowed him an escorted visit into the American sections. He reportedly paid $20 million US for the privilege.

At the time, NASA and the Canadian, European and Japanese space agencies said it was a one-time exception.

However, the world's five biggest space agencies have now established health and training standards for both astronauts and visitors to the space station.

Tito was followed a year later by South African internet millionaire Mark Shuttleworth. Greg Olsen, an American entrepreneur and scientist, became the third space tourist in October 2005.

The fourth space tourist, tech businesswoman Anousheh Ansari, went up on a Soyuz spacecraft Sept. 18, 2006. Ansari set many firsts with her flight: She became the first female space tourist, the first Muslim woman in space and the first Iranian in space.

While it is known that Tito, Shuttleworth and Olsen all paid about $20 million US to go into space, Ansari's agreement with the Russian space agency forbids her from talking about how much she paid for her ticket. Simonyi is set to become the fifth space tourist.

Is there any other way a civilian can get to the space station?

Space tourists weren't the first non-astronauts to get a seat into space. The Russian space agency had previously accepted cash to take Japanese journalist Toyohiro Akiyama and British chemist Helen Sharman up to Mir, the Russian space station. Because they didn't pay their own way, they're considered business travellers, rather than tourists.

They also weren't the first civilians to train for a space mission. Christa McAuliffe, a teacher who was killed in 1986 with her six crewmates when the space shuttle Challenger exploded shortly after launch, had been part of a program that allowed civilians to go into space without training as full-fledged astronauts.

But NASA cancelled the program after the Challenger disaster.

Barbara Morgan, who has also been a teacher and McAuliffe's backup on the Challenger mission, is scheduled to head into space this summer, but she had to do it the old-fashioned way — by joining the astronaut corps in 1998.

Morgan is scheduled to go to the International Space Station in June 2007, although NASA's recent Atlantis mission delays might push the launch back.

Is space tourism viable as a business?

NASA has studied the possibility of commercial space flight. One such study, released in 1998, suggested that space "cruises" could be a viable industry #8212; worth tens of billions of dollars a year #8212; if the cost of a ticket could be brought down to $100,000 US. But this same study showed that NASA would have to charge $10 million per ticket if they crammed 50 seats into a space shuttle #8212; and that's just to break even.

However, there are private companies that are hoping to sell seats on shuttles making sub-orbital flights. Suborbital flights to heights of 100 km above the Earth require much less energy than the orbital flights undertaken by NASA's space shuttles and Russia's Soyuz spacecraft. The International Space Station, for example, orbits at a distance of more than 350 km above the Earth.

Billionaire Richard Branson's Virgin Atlantic has a division with the ambitious name of Virgin Galactic that plans to take six passengers on a suborbital flight in its SpaceShipTwo by 2008.

The company bought the rights to develop a fleet of spaceships capable of suborbital flight based on the design of SpaceShipOne, the first commercially built ship to make two flights at a height of 100 km above the Earth.

But the cost of a two-hour flight on Virgin Galactic's SpaceShipTwo spacecraft remains too pricey for all but the wealthiest travellers #8212; about $200,000 US, a Virgin Galactic representative told the Associated Press in February.

Another spaceport could be coming to west Texas. Blue Origin, a company founded in 2000 by Amazon.com executive Jeff Bezos, is planning a launch site for sub-orbital flights in Culberson Co., Texas. But so far Blue Origin has only test launched a vertical takeoff and landing vehicle designed to take three astronauts on sub-orbital trips into space.

When did private companies enter the space race?

Private space exploration really took off with the launch of the Ansari X Prize. Named after sponsors Amir and Anousheh Ansari (the latter being the world's fourth space tourist) the Ansari X Prize was a competition to build and fly a reusable space vehicle entirely with private money. The winner had to safely fly a ship capable of carrying three people to the edge of space (100 km up) and back twice in a two-week period. There were about two dozen teams from seven countries competing for the $10 million US prize.

The prize was inspired by the Orteig Prize, first offered in 1919. In 1927, its $25,000 US purse lured Charles Lindbergh to make the world's first solo flight across the Atlantic, kick-starting an industry worth $300 billion today.

SpaceShipOne, a privately developed manned rocket created by aviation designer Burt Rutan and funded by billionaire Paul Allen, is shown in this undated promotional photo. The rocket won the Ansari X Prize and became the prototype for Virgin Galactic's planned fleet of suborbital spaceships. (Scaled Composites/Associated Press)

The X Prize was won by the SpaceShipOne team, backed by Mojave Aerospace Ventures. Their craft was lifted into the air attached to the belly of its mother ship, White Knight, and released at an altitude of 15 km. SpaceShipOne made the rest of the trip up with a rocket engine burning liquid nitrous oxide (laughing gas) and rubber.

Once it reached space, the ship altered its shape, pushing up its wings to resemble a badminton shuttlecock, for a more stable re-entry. The ship then reassumed its airplane-like shape to glide to the ground and land on an airstrip in the Mojave Desert.

Two Canadian teams competed for the X Prize. The da Vinci Project, based in Toronto, received approval from Transport Canada for two launches in Saskatchewan in October 2004, but the team postponed its launches indefinitely on Sept. 23, 2004. The other team, the Canadian Arrow based in London, Ont., completed its final engine test in 2002. The team successfully tested its space capsule when a helicopter dropped it into Lake Ontario in 2004, and received permission in 2005 to launch from Cape Rich on Georgian Bay.

Canadian Arrow has since partnered with U.S.-based Planetspace, a company attempting to join the space tourism industry. In February 2007 NASA signed a deal with Planetscape to share information on projected requirements for space station crew and cargo transportation launch vehicles and spacecraft.

I really want to experience zero gravity. What can I do?

When NASA wants to train astronauts or perform experiments in microgravity without going to space, it uses the KC-135 turbojet. The modified Boeing 707 performs a series of dives and sharp climbs, and the passengers experience microgravity for several seconds at the top of each parabola.

The zero-g scenes in the 1995 film Apollo 13 were shot on the KC-135, more commonly known as the "Vomit Comet" for the stomach-churning effect its flight path has on passengers. Through special programs, NASA has allowed high school students, engineering undergrads, medical students, journalists and even dancers to experience brief moments of zero-g on this airplane.

The Russian space agency has a similar plane, the IL-76. An Arlington, Va., company called Space Adventures sells flights on an IL-76 for about $5,000 US. This is the same company that brokered many of the space tourist trips to the space station. An American company, Zero Gravity, began offering weightless flights in September 2004 at about $3,000 US a ticket.

Space Adventures also sells high-altitude flights on Russian MiG-25 jets, which fly at twice the altitude of commercial airliners. For about $12,000 US, you can fly high enough to see for yourself that the Earth is indeed round.

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