If you have some innovative ideas on how to build a small, cheap surveillance drone that can be carried in a rucksack and easily controlled by a single person, Uncle Sam wants you — or at least the Defense Advanced Research Projects Agency does.

The agency, one of the Pentagon’s idea factories, has launched a contest with a $100,000 top prize as an “alternative way to tap into innovation” to help it develop such a drone, according to program manager Jim McCormick.

Called UAVForge, the competition is open to individuals, such as scientists, engineers or aircraft hobbyists, as well as to teams of contestants. The task is to come up with ideas for a small, silent aircraft that could be controlled from two miles away and monitor people or cars in an urban area for up to two hours while sending back still photos or video.

Publicized in May, UAVForge has generated ideas from 93 teams, McCormick said, including one from Italy and another from South Korea. Competitors have begun sending concept videos to the contest Web site.

The team that prevails after a multistage winnowing process will join with a DARPA-chosen defense manufacturer to fabricate 15 of its drones. The aircraft will be used by the military services and in a 2012 operational exercise, probably overseas.

McCormick, speaking to reporters Friday, said there was “no guaranteed success” in using this approach. He said DARPA has already been experimenting with promising prototypes from Defense Department contractors that proved the feasibility of the concept. But he said the prototypes being tested were too costly to produce and too difficult to operate.

The U.S. Army’s 4.2-pound Raven is said to cost $25,000 apiece and can fly for 80 minutes. A drone called the Wasp, which has a two-foot wingspan and weighs 14 pounds when loaded, is said to have cost more than $40,000 apiece four years ago.

McCormick told an audience in May that the agency was looking to cap the price of each aircraft at $10,000 and keep its weight to less than 20 pounds when loaded. The question is whether crowd-sourcing the competition will lead the way to a vehicle that fits that description. It’s an approach that DARPA has tested before.

In February, the agency announced a $10,000 price for design of a next-generation military fighting vehicle. In August, Local Motors partnered with Dassault Systemes to deliver the first crowd-sourced military vehicle. It went from concept to prototype in less than six months.