By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - A prototype passenger spaceship developed by privately owned Space Exploration Technologies arrived in Florida on Sunday for launch on a practice cargo run to the International Space Station, officials said on Monday.

Liftoff of the Dragon capsule aboard the company's Falcon 9 rocket is targeted for as early as December 19, although the final launch date will be set by NASA, which is sponsoring the flight, said Bobby Block, vice president for communications for Space Exploration Technologies, or SpaceX.

The mission will mark the third flight of SpaceX's Falcon 9 rocket and the second for a Dragon capsule, which is designed to fly first cargo and later crew to the space station, among other missions.

With the retirement of the space shuttles this summer, NASA is dependent on partner countries to deliver cargo and to ferry astronauts to the orbital outpost, a $100 billion project of 16 nations that orbits about 225 miles above the planet.

SpaceX, founded, owned and operated by Internet entrepreneur Elon Musk and based in Hawthorne, California, is one of two companies hired by NASA to deliver cargo to the station. Orbital Sciences Corp plans to debut its Taurus 2 rocket and Cygnus space station cargo capsule on a test flight next year.

SpaceX, along with Boeing Co, privately held Sierra Nevada Corp. and Blue Origin, also hold NASA contracts to develop spaceships that can carry people.

RUSSIAN SOYUZ CAPSULES

Flying astronauts on Russian Soyuz capsules -- currently the only vehicles taking crews to the space station -- costs the U.S. space agency more than $50 million per person.

For its trial run to the station, SpaceX plans to put Dragon into orbit to test its maneuvering, communications and other systems as part of its $278 million contract with NASA.

If all goes well, the capsule would be cleared to approach the station, where astronauts would use the station's robotic crane to pluck Dragon from orbit and attach it to a berthing port on the station.

The capsule will carry food, water and other station supplies. Unlike other cargo vessels, which incinerate in the atmosphere after leaving the station, Dragon returns via parachute and splashes down in the ocean so it can return cargo from the station as well.

Pending NASA's approval, SpaceX plans to bring Dragon back to Earth 22 days after launch.

"It's important that we're successful and we're doing a lot of work with our NASA partners to make sure that we've done all the necessary cross checks, verify all the requirements to make sure this vehicle is ready to go," SpaceX Vice President Ken Bowersox said at the Symposium for Personal and Commercial Spaceflight in New Mexico last week.

Initially, SpaceX's contract called for three test flights before the company would start delivering cargo to the station under a separate $1.6 billion contract. Following Dragon's successful debut mission in December 2010, SpaceX petitioned NASA to combine the objectives of the next two flights.

The final decision about whether to let Dragon dock at the station, however, will not come until the flight is under way.

"We'll be prepared to go all the way to the station," Block told reporters on Monday at the company's Cape Canaveral launch site, where Dragon is being prepared for flight.

SpaceX has spent about $800 million developing Falcon 9 and Dragon. A similar system developed under traditional government contracts would have been between $2.4 billion and $7.2 billion, Bowersox said.

"It was very useful for both NASA and SpaceX to have this relationship," he said.

(Editing by Jane Sutton and Will Dunham)