The upcoming launch of a SpaceX spacecraft and rocket on a demonstration flight to the International Space Station is expected to cross a key milestone on the path to operational, commercial missions.

"It's almost like the lead-up to Apollo, in my mind," said Mike Horkachuck, NASA's project executive for SpaceX. "You had Mercury then you had Gemini and eventually you had Apollo. This would be similar in the sense that, we're not going to the moon or anything as spectacular as that, but we are in the beginnings of commercializing space. This may be the Mercury equivalent to eventually flying crew and then eventually leading to, in the long run, passenger travel in space."

California-based Space Exploration Technologies, known as SpaceX, is preparing to launch an ambitious mission to dock its Dragon spacecraft to the space station and return it to Earth. The spacecraft will not have a crew, but will carry about 1,200 pounds of cargo that the astronauts and cosmonauts living on the station will be able to use. The capsule will go into space atop a Falcon 9 rocket also built by SpaceX.

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