The Guided Missiles Division of Republic Aviation was awarded a contract for development of a short-range reconnaissance drone in 1957,[1] winning a competition conducted by the U.S. Army to fill the requirement. Given the overall designation AN/USD-3 for the entire system, and sometimes referred to as Sky Spy,[2] the Snooper was of twin-boom configuration, a single Continental IO-200 horizontally-opposed piston engine being mounted in a pusher configuration.[3] The drone was capable of flying for up to 30 minutes, allowing it to overfly multiple reconnaissance targets during a single flight.[1]
Launch was from a zero-length launch setup, two rocket boosters burning solid fuel being used to assist the aircraft into flight; following a mission, which could either use autopilot control following a programmed course or radio command guidance from a ground station,[3] the Snooper would land via parachute; airbags were installed in the airframe to cushion the landing.[1] The SD-3's nose section was designed to be interchangeable among a number of payloads; options included television, aerial photography, infrared photography, or radar systems.[4]
Revealed to the press in late 1958,[5] the SD-3 first flew in January 1959; following manufacturer's trials, the U.S. Army ordered fifty pre-production aircraft to conduct a full evaluation of the system.[3] Although the trials, conducted by the Signal Corps,[6] were considered successful,[1] the Army cancelled the SD-3 program at the end of the trials.[7] However, the SD-3's twin-boom pusher design would become commonly used by unmanned aerial vehicles in later years.[2]