Sending a package to outer space is not as simple as dialing a parcel company. But it's getting there.

If all goes well, on Wednesday morning a privately owned robotic spaceship, the Cygnus, will blast off from Wallops Island, Va., to deliver cargo to NASA astronauts living on the International Space Station. Crews in space have already received three loads of freight on robotic spaceships belonging to California-based SpaceX, but Cygnus is owned by a rival firm. And that means that Wednesday's flight will mark a milestone of its own: the beginning of competition in the high-stakes business of supplying astronauts in orbit.