With NASA's retired shuttles mothballed in museums, 2012 saw a new kind of spacecraft blaze its own path toward the International Space Station. In May, the Dragon space capsule - developed, owned and operated by California-based SpaceX - was launched from atop a Falcon-9 rocket, becoming the first private craft to dock with the ISS.

A feat achieved by only a few governments, the docking, says SpaceX chief Elon Musk, signaled more than a mere technological breakthrough.

"This was a crucial step," Musk said of the unmanned mission that was completed in conjunction with NASA. "It makes the things in the future, and the ultimate path toward humanity becoming a multi-planet species, much, much more likely."

Designed to carry cargo or crew, the Dragon capsule is slated for a manned test within three years.

Also working with NASA, Orbital Sciences Corporation, which has developed the Antares rocket and Cygnus cargo craft, has a planned 2013 demonstration flight to the space station.

At Kennedy Space Center for SpaceX's second successful ISS mission in October, NASA administrator Charles Bolden said these partnerships spur innovation and benefit the U.S. space program.

"We're handing off to the private sector our transportation to the International Space Station so that NASA can focus on what we do best - exploring even deeper into our solar system, with missions to an asteroid and Mars on the horizon," he said.

NASA officials have said the agency, via partnerships, is on track to launch astronauts from the United States within five years.

Presently constructing the Space Launch System, the largest rocket ever built, NASA engineers are also developing the Orion capsule, a craft designed to take astronauts 15 times farther than the International Space Station.

With Orion's unmanned trial mission set for 2014, interest in NASA's next generation vehicles has been growing.

"I'm glad to see the whole space program is going on because, I don't know, it seemed to me at least that all was kind of dead," said teenager Andrew Clancy at an April science festival in Washington. "But it's alive and well and looks great."

Acting as a lead investor that offers expertise and advice in addition to funding, NASA has secured contracts with three U.S. companies that are working on vehicles for manned missions to low-Earth orbit.

Boeing, for example, is working on its Crew Space Transportation-100 capsule, which is designed to carry seven people and land on the ground. SpaceX is also developing vehicles similar in shape to late 20th century lunar capsules.

Nevada-based Sierra Nevada Corporation, however, is developing a winged spacecraft called Dream Chaser, whose shape more closely resembles a plane or a retired space shuttle.

"It's the same contest we played out in the 1950s - wings versus gumdrops [capsule-shaped vehicles]," said Howard McCurdy, a public affairs professor at American University in Washington. "Nobody knows at this stage which is the superior technology."