NASA has named the four astronauts who will embark on the first test flights of SpaceX and Boeing's commercial crew spacecraft. Astronauts Bob Behnken, Eric Boe, Doug Hurley and Sunita ("Suni") Williams will train with the companies' own test pilots for the maiden voyages of the Dragon crew capsule and the CST-100.

All four astronauts have prior spaceflight experience, having flown on the Space Shuttle to the International Space Station. Boe and Hurley were both pilots, while Behnken and Williams were mission specialists. Hurley served on the last shuttle mission, STS-135.

"These distinguished, veteran astronauts are blazing a new trail, a trail that will one day land them in the history books and Americans on the surface of Mars," NASA Administrator Charles Bolden said in a statement about the selection.

In September, NASA announced that both SpaceX and Boeing would be awarded contracts to build and operate spacecraft to ferry astronauts to and from the International Space Station. SpaceX received $2.6 billion to create an updated design of its Dragon cargo spacecraft, while Boeing received $4.2 billion to turn the design of its CST-100 into reality. Both capsules will be able to carry a crew of seven, with their first flights slated for 2017. The Dragon will launch on top of SpaceX's Falcon rocket, and the CST-100 will initially launch on top of ULA's Atlas V rocket, though it will be compatible with multiple rocket types.

Since the retirement of the Space Shuttle in 2011, NASA has been reliant on the Russian Soyuz rocket to transport the space agency's astronauts to the ISS. The option is both expensive and not exactly ideal. Sending a single NASA astronaut on the Soyuz costs the agency upwards of $70 million, and relations between the United States and Russia have been strained since the Ukraine crisis.

The Commercial Crew Program is NASA's way of getting American astronauts back on American rockets for a lower rate. SpaceX claims a ride on its Dragon crew capsule will cost only $58 million, and if the company's efforts to reuse its Falcon 9 prove fruitful, the price tag may be even lower in the future.

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