Key to many a successful military assault is the element of surprise. If an attacking force can arrive undetected—through terrain thought to be impassible—the battle is half won. The U.S. Defense Advanced Research Projects Agency, the arm of the Pentagon most responsible for shiny, futuristic technology, recently gave a $100,000 grant to Logos Technologies, Fairfax, Va.-based defense tech company, to develop a silent, hybrid-engine motorcycle for the military.

What can the military do with a motorcycle that runs nearly silently? Wade Pulliam, the program manager at Logos Technologies, told Popular Science that while there's "no CONOPS [concept of operations] set in stone," it would be ideal for missions deep into hostile territory.