NASA on Monday unveiled a plan that will allocate $1.61 billion to private companies that will transport U.S. astronauts to the International Space Station and low Earth orbit.

NASA on Monday unveiled a plan that will allocate $1.61 billion to private companies that will transport U.S. astronauts to the International Space Station and low Earth orbit.

The program, which will run from July 2012 to April 2014, will provide funds to multiple companies, which must design and maintain spacecraft, launch vehicles, launch services, ground and mission operations, and recovery.

"This is a significant step forward in America's amazing story of space exploration," NASA Administrator Charles Bolden said in a statement. "It's further evidence we are committed to fully implementing our planas laid out in the Authorization Actto outsource our space station transportation so NASA can focus its energy and resources on deep space exploration."

NASA retired its space shuttle fleet over the summer and has since relied on Russian spacecraft to get its astronauts to the ISS (at a price of $50 million per person). During the most recent Soyuz landing, however, communications between the landing craft and Russia's Roscosmos space agency after the Soyuz capsule had de-orbited. Contact was re-established before landing and no one was injured, but the "space taxis" announced by NASA this week gives the agency another option for getting its astronauts to the ISS.

The effort, known as Integrated Design Contract (IDC) "will bring us through the critical design phase to fully incorporate our human spaceflight safety requirements and NASA's International Space Station mission needs," said NASA Commercial Crew Program Manager Ed Mango. "We look forward to strong U.S. industry response."

To push development, NASA also said it will fund some optional programs negotiated as add-ons to existing Commercial Crew Development (CCDev2) Space Act Agreements (SAA) . Specifically, Sierra Nevada Corp. will get $25.6 million for a total of $105.6 million, while Boeing will take home another $20.6 million for a total of $112.9 million. Space Exploration Technologies/SpaceX and Blue Origin have also been awarded contracts.

"All four CCDev2 partners are performing very well and meeting their milestones," said Phil McAlister, director of NASA's Commercial Spaceflight Development. "These additional milestones were selected because they sufficiently accelerated the development of commercial crew transportation systems to justify additional NASA investment."