NASA has granted two companies in the United States with multibillion-dollar contracts to supply the orbiting ISS with cargo since the retirement of the space shuttle fleet. The two companies are Orbital and SpaceX. We have heard a lot more about SpaceX in the recent months while hearing relatively little from Orbital.
SpaceX has already test fired its Falcon 9 rocket and its Dragon capsule has already been in orbit. Meanwhile, Orbital has yet to test fire its rocket and its own Cygnus capsule remains untested. Orbital is looking to move faster with a static launch test and the first launch into orbit for its capsule scheduled for this summer. The company is also looking forward to a possible mission to the ISS this fall. SpaceX already had a mission to the ISS on the books, but that was postponed for more testing.
SpaceX has designed much of its rocket and capsule in-house while Orbital has bought many of the components needed from around the globe. For instance, Orbital buys rocket engines from the Soviet Union that were originally designed for the N-1 lunar rocket. However, Orbital's Cygnus capsule is purpose built and intended to deliver supplies to the ISS, and will not support astronauts. The Dragon capsule will support manned flight. Orbital thinks it's a race to see which of the companies will be the first to dock a private spacecraft with the ISS.