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SpaceX _ or Space Exploration Technologies Corp. _ is run by billionaire Elon Musk, a co-founder of PayPal who also directs the electric car maker Tesla Motors.

His space company is working to turn the unmanned Dragon vessels into craft that could carry Americans to the space station in the coming years. Until SpaceX or another U.S. company can do that, NASA astronauts will have to keep riding on Russian rockets at a steep cost.

SpaceX estimates it will be ready to launch crews aboard Dragons in three years.

NASA, meanwhile, expects to name within a few weeks the U.S. astronaut and Russian cosmonaut who will spend an entire year aboard the space station, beginning in spring 2015, twice the usual length for a mission. Suffredini said the list of potential candidates is “very short.”

Another NASA official said only previous space station crew members are under consideration for the two slots because they’re already trained in the systems of the orbiting complex.

On Friday, the space agency said it would commit to a yearlong mission to learn what it will take for humans to journey beyond low-Earth orbit _ Mars, for example.

Russia already knows. Three cosmonauts spent at least a year aboard the old Mir space station; the record for a single stint is almost 15 months.

No American has spent more than seven months in space at a time.

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Online:

SpaceX: http://www.spacex.com/

NASA: http://www.nasa.gov/mission_pages/station/main/index.html