WATCH: NASA to award contracts to SpaceX and Boeing to fly astronauts to space

WASHINGTON, Sept. 16 (UPI) -- NASA is set to announce its decision to award coveted contracts to bring human space flight back to U.S. soil to both Boeing and SpaceX on Tuesday.

In a live announcement planned for 4 p.m., the space agency will open the door to putting its astronauts back on American-flown rockets by 2017.

Since the shuttering of the space shuttle program in 2011, NASA has relied on Russian Soyuz craft to ferry astronauts back and forth to the International Space Station, at a cost of more than $70 million per ride.

Some $1 billion had been given to SpaceX, Boeing and a third company, Sierra Nevada Corp., to develop commercial "space taxis" for NASA work.

Sources said Boeing is likely to receive a larger share of the final multi-billion dollar contract, but it's unclear how the experienced "old space" company will split the work load with the Elon Musk-founded upstart.

NASA will essentially rent these new space taxis to send U.S. crews into orbit. SpaceX has been using its Dragon capsule powered by the Falcon rocket, a similar vehicle to what it has used for several years to carry cargo to the ISS. Boeing uses the CST-100, which is boosted by the Atlas V.

Musk has turned up his criticism of Boeing's reliance on the Atlas V rocket, which uses a Russian-made engine, as U.S. relations with the Kremlin have grown increasingly strained in recent months.

But on Wednesday, Boeing and Lockheed Martin's United Launch Alliance are expected to announce plans to team up with Blue Origin to develop of American-made engine for the Atlas V. Blue Origin is a startup founded by Amazon and Washington Post owner Jeff Bezos.

Meanwhile, Lockheed and NASA have been working to develop the Orion capsule, a spaceship that will be used to fly astronauts into deep space.

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