"As part of our current program, space tourist flights to the ISS will continue. But from 2010, difficulties could emerge due to planned increases in ISS crew numbers to between six and nine members," Anatoly Perminov told journalists.
Space tourists started flying to the ISS in 2001. American Richard Garriott, due to fly to the ISS this coming fall, will become the sixth space tourist.
Dennis Tito, an American businessman and former NASA scientist, became the first space tourist when he visited the ISS in 2001. He was followed by South African computer millionaire Mark Shuttleworth in 2002, and Gregory Olsen, a U.S. entrepreneur and scientist, in 2005.
In 2006 Anousheh Ansari, 40, a U.S. passport holder of Iranian descent and communications head, became the first female space tourist, followed by Charles Simonyi, 58, a U.S. passport holder born in Hungary and a key figure in developing Microsoft's Word and Excel applications, in 2007.
The space tourists paid about $20 million each for the pleasure of spending a week on the orbital station, but Russia said the price for commercial space flights was set to rise in the future, reaching $25 million.
