Early Thursday morning, the Russian’s Soyuz spacecraft will lift off from the Baikonur Cosmodrome in Kazakhstan carrying the last private tourist, U.S. software designer Charles Simonyi, to the space station. Since the station is expanding from three crew members to six, Soyuz must be used to accommodate, for example, Canadian, European, and Japanese astronauts who have been waiting years to live aboard the International Space Station (ISS). Also, after 2010 when the U.S. space shuttles are retired, the Russian spacecraft will have to carry U.S. astronauts to space. Such heavy lifting for Soyuz puts an end, for now, to what was once a lucrative Russian space tourism program.

Since 2001, the Russians have flown six private spaceflight participants, who each paid a minimum of $20 million, brokered through Virginia-based Space Adventures, for trips to space. Simonyi will be making his second trip, a $35 million deal, to the station. He is scheduled for a 12-day mission to perform research on bone density loss and lower-back pain in space, to work on Earth-observation studies, and to communicate with students. You can follow his experience online.

However, Space Adventures president and CEO, Eric Anderson, told me via e-mail that the Russian’s announcement does not affect the company’s plans for future private space missions and that Space Adventures has a private mission scheduled for 2011. “We are moving forward as planned,” said Anderson. (You can view the company’s press release here.)

In addition, the Russian Federal Space Agency’s chief, Anatoly Perminov, told the government newspaper that it has promised Kazakhstan it will send a cosmonaut from the ex-Soviet republic to the station “on a commercial basis,” and that trip would have take place this fall.

“The Russians have simply said, ‘We are not taking paying passengers’ on Soyuz, a government vehicle, because the space station is expanding its crew. But in terms of the business, [Simonyi’s flight] is not the last commercial flight to space,” says Henry Hertzfeld, a research professor of space policy and international affairs at George Washington University in Washington DC.

Private companies such as Xcor Aerospace, based in Mojave, CA, and Virgin Galactic owned by billionaire Richard Branson’s Virgin Group, are building rockets and spacecraft to take passengers on suborbital flights, and the vehicles may even be used to test government instruments. But Hertzfeld says this type of private enterprise is still in its infancy. “It still has to be proven to be a good business,” he says. Hertzfeld adds that most of these companies, if not all, that are well along in making vehicles are receiving government contracts and R&D money.

One example is SpaceX, based in Hawthorne, CA, which has received a government contract to use its rocket to carry cargo to the space station once the shuttles retire. The company also has a clause in its contract, which NASA has yet to exercise, to carry crew members to the station. “We have developed the capability to just do cargo with future plans to evolve to carry crew. Our capsule design can accommodate both,” says Lawrence Williams, the company’s vice president. The SpaceX vehicle, called Falcon, is scheduled for its first docking with the station in 2011. “If we started working on the crew capabilities today, we could carry crew within 24 months,” says Williams.

While there are private companies working diligently to build vehicles to accommodate U.S. human spaceflight missions, it remains that the Soyuz spacecraft will be even more crucial than it already is to the upkeep and expansion of the $100 billion space station. Williams says the major factor in Russia’s decision to stop taking paying passengers after 2009 is the fact that it is going to have to fly a lot more U.S. astronauts to the space station. “The U.S. will have no vehicle to fly on its own, so in the interim NASA has to rely on the commercial sector,” says Williams. “The Russians have a contract to do just that.”

“We will have a gap and it is regrettable, but the shuttle is an aging vehicle and the decision had to be made to retire it. Now we are going to have to rely on others and to also focus on Ares [NASA’s future launch vehicle] to get back our capability for human beings to travel to space,” says Hertzfeld.