Four Companies at Forefront of Commercial Space Race

Four private companies are the leaders in the effort to build commercial spaceships to carry astronauts to low-Earth orbit and the International Space Station after the space shuttles retire. The four contract winners are Blue Origin, Sierra Nevada, SpaceX and Boeing. While the timeline is murky, officials say the earliest a commercial spacecraft would be ready to carry crews to orbit is around 2014-15.

The firms are at various stages of development; SpaceX is the only one that has flown its version of an orbital spacecraft on a test flight. 

Boeing is developing a capsule called the Crew Space Transportation-100 (CST-100), which would be compatible to fly atop various rockets, including SpaceX's Falcon 9 and United Launch Alliance's Atlas and Delta boosters.

Sierra Nevada is building a space plane called Dream Chaser that would launch atop an Atlas rocket like a capsule but glide down for landing like a plane or the space shuttle

Rounding up the group is Blue Origin, a company founded in 2000 by Amazon.com founder Jeff Bezos. Blue Origin is the most secretive of the space companies, keeping specifics of its spacecraft and timeline under wraps.

The four companies are hoping NASA won't be the only customer looking to buy passage aboard their orbital spacecraft. They intend to sell seats to space tourists as well as to astronauts from countries without their own space vehicles. Space.com