Boeing Co (BA.N) announced plans to launch its seven-seat spaceship on a test run to the International Space Station in 2015 using Atlas 5 rockets built by its United Launch Alliance venture.

The project, however, is dependent on additional government funding, Boeing Vice President John Elbon told reporters during a conference call,

He declined to say how much added money would be needed.

Rocket-makers Space Exploration Technologies and ATK Launch Systems Group (ATK.N) also vied for the job of launching Boeing's CST-100 capsules, popularly known as "space taxis," on three test flights planned in 2015.

United Launch Alliance, or ULA, is a partnership with Lockheed Martin Corp (LMT.N). "The process is designed to ensure that the decision wasn't biased by the fact that Boeing is a partial owner of ULA," he said.

The Atlas 5 rocket's pedigree gave it the edge, with 26 successful flights and no failures over five years of flying NASA science probes, commercial satellites and military payloads, Elbon said.

Boeing is among four firms sharing $269 million in NASA funds to start developing alternative crew transportation to the space station, following the retirement of the U.S. space shuttles last month.

Until a U.S. company develops the capability to fly people in orbit, NASA will pay Russia to ferry astronauts to the space station, a $100 billion project of 16 nations.

Flights on Russian Soyuz spacecraft cost more than $50 million per person, including training.

"Our approach is to build a reliable spacecraft, built on existing simple systems, then integrate that with a proven launch vehicle all focused on putting in place a very safe system that can be operational as soon as practical so that we can start flying U.S. crews from U.S. launch sites in the post-shuttle era," Elbon said.

The Obama Administration's proposed budget for NASA's so-called commercial crew initiative is $850 million, a figure that Elbon says is "in the ballpark," for a trio of CST-100 test flights in 2015, though delays are likely if the pool of funds is divided among several space taxi designs like the current program.

In addition to Boeing's capsule, NASA also is funding space taxi projects by Space Exploration Technologies, or SpaceX, Sierra Nevada Corp, and Blue Origin, which is owned by Amazon founder Jeff Bezos.

SpaceX plans to launch its Dragon capsule on the company's own Falcon 9 launchers while Sierra Nevada and Blue Origin have outlined plans to use ULA's Atlas 5 rockets for test flights.

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