Several companies are working on rockets and spacecraft that could ferry supplies and astronauts to the International Space Station, now that the shuttle program is over.
A brief look at each:
* Alliant Techsystems Inc., or ATK, headquartered in Arlington, Va., with aerospace division in Magna, Utah. Developing Liberty launch system including rocket and passenger spacecraft. Test flights to begin in 2014, with possible first manned launch in 2015.
* Blue Origin in Kent, Wash. Run by Amazon founder Jeff Bezos. Developing rocket and space vehicle to transport astronauts. Also planning suborbital flights for experiments and tourists. This latter launch system is called New Shepard, after Mercury astronaut Alan Shepard.
* Boeing, headquartered in Chicago, with spacecraft development in Houston. Space capsule, called CST-100, undergoing parachute drop tests in the Nevada desert. Designed to carry astronauts as well as cargo. Initial test flights to be launched by United Launch Alliance's Atlas V rockets.
* Excalibur Almaz Inc. in Houston. Spacecraft planned for tourism would also serve space station crews.
* Orbital Sciences Corp. in Dulles, Va. Building Antares rocket and Cygnus spacecraft. First test flight for cargo scheduled by year's end from NASA's Wallops Flight Facility in Virginia.
* Sierra Nevada Corp., headquartered in Sparks, Nev. Space systems group in Louisville, Colo. Building Dream Chaser, a mini shuttle for crews. To be launched aboard United Launch Alliance's Atlas V rocket. First flight with crew targeted for 2016.
* Space Exploration Technologies Corp. in Hawthorne, Calif. Run by PayPal co-founder Elon Musk. Building Falcon rocket and Dragon spacecraft. First private launch of space station supplies scheduled for Saturday from Cape Canaveral, Fla.
* United Launch Alliance in Centennial, Colo. Joint venture of Boeing and Lockheed Martin Corp., builders of Delta and Atlas rockets, currently used for unmanned flights. Studies under way on manned flights.