Republic SD-3 Snooper

The Republic SD-3 Snooper was an early unmanned reconnaissance aircraft built by Republic Aviation for the U.S. Army. It underwent testing by the Army Signal Corps in 1959 but was never put into active service.

Republic Aviation’s Guided Missiles Division secured a development contract in 1957 after winning an Army competition for a short-range reconnaissance drone. The complete system was designated AN/USD-3, and the drone itself was also called Sky Spy. It featured a twin-boom layout with a single Continental IO-200 horizontally opposed piston engine mounted in a pusher configuration. The Snooper could stay aloft for up to 30 minutes, enough to pass over several reconnaissance targets in one flight.

Launch used a zero-length setup assisted by two solid-fuel rocket boosters. During a mission, the drone could follow a preprogrammed autopilot course or be guided by radio commands from a ground station. It landed by parachute, with airbags built into the airframe to soften the impact. The nose section was interchangeable, allowing payloads such as television, aerial photography, infrared photography, or radar systems.

The SD-3 was shown to the press in late 1958 and made its first flight in January 1959. After manufacturer testing, the Army ordered fifty pre-production units for a full evaluation. Although the Signal Corps deemed the trials successful, the Army canceled the program once they were complete. The twin-boom pusher design later became common in many unmanned aerial vehicles.