CAPE CANAVERAL, Fla. - When it comes to complaining about poor exchange rates for the US dollar, American tourists traveling to Europe have nothing on tourists headed into space. The cost of flying to the international space station aboard a Russian Soyuz spaceship has increased from $25 million earlier this year to $30 million. Trips planned in 2008 and 2009 will cost $40 million.

Backdropped by the blackness of space and Earth's horizon, the International Space Station moves away from the Space Shuttle Atlantis in this digital photograph taken by an Atlantis crew member June 19, 2007. [Reuters]

"It's mostly because of the fallen dollar," Eric Anderson, president and CEO of Space Adventures, said Wednesday. His company brokers the trips with Russia's space agency.

A US dollar currently is worth about 25 1/2 Russian rubles, compared with 32 rubles in 2002.

Five space tourists have paid $20 million to $25 million to visit the space station via the Soyuz vehicles through trips arranged by Space Adventures. The company announced Wednesday that two more Soyuz seats have been purchased for tourists to fly in 2008 and 2009.

Anderson said the space tourists flying in the two new seats likely would be an American and an Asian, but he offered no details. Prospective space tourists must put down a 20 percent deposit, pass physical examinations and later undergo training at a Russian space facility.

About a dozen prospective space tourists are in the process of reserving flights to the space station, even as the number of available seats on the three-man Soyuz vehicles is likely to diminish after space shuttles are grounded in 2010.

NASA is going to rely on the Soyuz vehicles to deliver astronauts to the space station between the end of the shuttle program in 2010 and the expected first manned flight in 2015 of the next-generation spacecraft, Orion, which NASA hopes takes astronauts back to the moon by 2020. Additionally, the three-member space station crew, consisting of US astronauts and Russian cosmonauts, is expected to double in size in 2009.

"We're certainly working out ways to get more seats," Anderson said. "With the competition at that point, it becomes more difficult."