US Patent 8692171 Hand launchable unmanned aerial vehicle

An unmanned aerial vehicle including a controller operating in a search mode of operation where a receiver of an acquisition sensor searches for a target and causes flight control surfaces to guide the vehicle in a downward spiral path, a terminal mode of operation where the acquisition sensor detects a target and causes flight control surfaces to direct the vehicle toward the target, and an activation mode of operation where a trigger sensor detects a target within a predetermined distance to the vehicle and the controller activates a responder.