NASA is looking for two private firms to design and build 'space taxis' to ferry astronauts to and from the International Space Station.
NASA plans to invest $300 million to $500 million in each of the firms selected under new 21-month partnership agreements, Ed Mango, manager of NASA's Commercial Crew program, said at an industry briefing at the Kennedy Space Center prior to the release of a solicitation on Tuesday.
The new program aims to build upon previous NASA investments in companies designing commercial passenger spaceships.
With the retirement of the U.S. space shuttles last year, Russia has a monopoly on flying crews to the station, a $100 billion orbiting laboratory for medical, materials science and other research.
China, the only other country that has flown people in orbit, is not a partner in the project.
Russia charges NASA about $60 million per person for rides to the station, which flies about 240 miles (385 km) above Earth and is staffed by rotating crews of six astronauts from the United States, Russia, Europe, Japan and Canada.
Winning firms would have until May 2014 to complete their integrated designs, with the intention, if funding allows, to test fly their spaceships in orbit by the middle of the decade, Mango said.