Alpha Centauri or bust.

The government agency that helped invent the Internet now wants to do the same for travel to the stars.

In what is perhaps the ultimate startup opportunity, Darpa, the Defense Advanced Research Projects Agency, plans to award some lucky, ambitious and star-struck organization roughly $500,000 in seed money to begin studying what it would take — organizationally, technically, sociologically and ethically — to send humans to another star, a challenge of such magnitude that the study alone could take a hundred years.

The awarding of that grant, on Nov. 11 — 11/11/11 — is planned as the culmination of a yearlong Darpa-NASA effort called the 100-Year Starship Study, which started quietly last winter and will include a three-day public symposium in Orlando, Fla., on Sept. 30 on the whys and wherefores of interstellar travel. The agenda ranges far beyond rocket technology to include such topics as legal, social and economic considerations of interstellar migration, philosophical and religious concerns, where to go and — perhaps most important — how to inspire the public to support this very expensive vision.

The Darpa plan has generated buzz as well as befuddlement in the labs, pubs, diners and Web sites that ring NASA centers both physically and virtually, where the dream of space travel has never died and where a few stubborn bands of scientists and engineers, fueled by science fiction dreams and prophecies, are designing spacecraft that could cross interstellar space, incubating a technology and preserving it for the day when it will be used.