A NASA center and the Pentagon's lead research group are striking financial flint to steel in hopes of sparking a sustained effort to make interstellar space travel a reality.

On Thursday, an official with the Defense Advanced Research Projects Agency (DARPA) announced that the agency will award a $500,000 grant to the person or group who can lay out the most effective road map for financing and implementing a research and development program to lead to interstellar travel by early next century.

At that point, the government will bow out, leaving it up to the winner to turn the ideas on Powerpoint slides to a sustainable research program – one that also is likely to focus on the ethical, economic, and legal issues surrounding the prospect of launching humans to other stars.

The award, expected to be announced in November, represents the final stage in what by then will have been a year-long collaboration between DARPA and NASA's Ames Research Center in Moffett Field, Calif. The money is what remains of an initial pot of $1 million – mostly from DARPA – to get the project, dubbed the 100 Year Starship Study, going.

The technological hurdles alone of achieving interstellar space travel are high – driven by the enormous distances involved.

Take the Voyager 1 spacecraft, for instance. It's currently hurtling toward interstellar space and took nearly 34 years to reach its current location at the edge of the solar system some 930 million miles from the sun.

The nearest star to the sun, Alpha Centauri, is roughly 2,700 times farther from the sun than Voyager, explains Bruce Betts, director of projects for the Planetary Society, a space-exploration advocacy group based in Pasadena, Calif. At Voyager's speed, it would take tens of thousands of years to get there.

From that simple distance estimate comes huge challenges in developing propulsion systems that will reach speeds needed to get Alpha Centauri within several human generations and the braking systems needed to slow the starship down once it gets there. Power generation for the ship's life-support systems represents another significant hurdle, as would the communications systems needed to keep in touch with folks back home. The list goes on.

For a robotic probe to a nearby star, "if you can throw money at it for long periods of time you can start coming up with solutions" to these issues, Dr. Betts says.

It's a lot harder to swallow the idea of humans traveling to another star, he continues. "We're choking and sputtering on trying to make sure we come up with solutions to send them to asteroids or to Mars."

Indeed, funding is just as big a challenge as technology, acknowledges David Neyland, director of the Tactical Technology Office at DARPA.

"Reaching the stars in the next century will require sustained interest and investment over a long period of time," he says.

That's why the 100 Year Starship Study will focus heavily on designing an approach to R&D funding that will not rely on an endless stream of money from the federal government, although agencies, including DARPA, may opt to pay for lines of research that have a direct bearing on their priorities.

That task may become somewhat easier if, as space scientists hope, researchers can identify habitable, Earth-like planets in the sun's neighborhood.

At a 100 Year Starship workshop in January, most of the participants said any approach to funding the R&D effort should be independent of the vagaries of the federal budget. Among the options the group discussed: tapping very wealthy donors to contribute to an endowment fund, which also could be fattened through small individual donations, similar to those that bolstered campaign coffers during the 2008 presidential election.

More ideas are expected to surface at a three-day symposium on the 100 Year Starship effort scheduled to begin Sept. 30 in Orlando, Fla.

For spaceflight advocates, the meeting will be an early indication of whether ideas once thought to be the province of Fantasyland can be converted into practical technologies eventually populating a Tomorrowland.