During the past 10 years, Presidents George W. Bush and Obama have directed NASA to turn the job of transporting cargo and crew to the space station over to the private sector. As that process gathers pace, here is a list of the key players.
SpaceX's Falcon 9 rocket has already proved itself able to get a cargo payload to the International Space Station. Orbital Sciences' Antares rocket, set for its first test launch Wednesday evening, is a very different animal.
The Antares rocket, built by Orbital Sciences Corp., is set for a first test launch Wednesday evening, weather permitting. Its maker is, like SpaceX, under contract with NASA to ferry cargo to the International Space Station.