The Republic SD-3 Snooper was an early reconnaissance drone developed by

Republic Aviation The Republic Aviation Corporation was an American aircraft manufacturer based in Farmingdale, New York, on Long Island. Originally known as the Seversky Aircraft Company, the company was responsible for the design and production of many important ...

for the

United States Army The United States Army (USA) is the land warfare, land military branch, service branch of the United States Armed Forces. It is one of the eight Uniformed services of the United States, U.S. uniformed services, and is designated as the Army o ...

. It was evaluated by the Army Signal Corps in 1959, but did not enter operational service.

Design and development

The Guided Missiles Division of Republic Aviation was awarded a contract for development of a short-range reconnaissance drone in 1957,Ordway and Wakeford 1960, p.USA50. 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,Newcome 2004, p.75. the Snooper was of

twin-boom A twin-boom aircraft is characterised by two wikt:Longitudinal, longitudinal booms (extended nacelle-like bodies). The booms may contain ancillary items such as fuel tanks and/or provide a supporting structure for other items. Typically, twin ...

configuration, a single Continental IO-200

horizontally-opposed piston engine A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, wh ...

being mounted in a

pusher configuration In an aircraft with a pusher configuration (as opposed to a tractor configuration), the propeller(s) are mounted behind their respective engine(s). Since a pusher propeller is mounted behind the engine, the drive shaft is in compression in no ...

.Parsch 2004 The drone was capable of flying for up to 30 minutes, allowing it to overfly multiple reconnaissance targets during a single flight. Launch was from a

zero-length launch The zero-length launch system or zero-length take-off system (ZLL, ZLTO, ZEL, ZELL) was a method whereby jet fighters and attack aircraft could be near-vertically launched using rocket motors to rapidly gain speed and altitude. Such rocket boos ...

setup, two rocket boosters burning

solid fuel Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuel ...

being used to assist the aircraft into flight; following a mission, which could either use

autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

control following a programmed course or

radio command guidance Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its P ...

from a ground station, the Snooper would land via parachute;

airbags An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. Th ...

were installed in the airframe to cushion the landing. The SD-3's nose section was designed to be interchangeable among a number of payloads; options included television,

aerial photography Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other airborne platforms. When taking motion pictures, it is also known as aerial videography. Platforms for aerial photography include fixed-wing aircr ...

infrared photography ''Top:'' tree photographed in the near infrared range. ''Bottom:'' same tree in the visible part of the spectrum. In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is r ...

, or

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

systems.''

Aviation Week ''Aviation Week & Space Technology'', often abbreviated ''Aviation Week'' or ''AW&ST'', is the flagship magazine of the Aviation Week Network. The weekly magazine is available in print and online, reporting on the aerospace, defense and aviatio ...

'', Volume 70, 1959
page 58

Operational history

Revealed to the press in late 1958, 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. Although the trials, conducted by the Signal Corps, were considered successful, the Army cancelled the SD-3 program at the end of the trials.''Astronautics'' Volume 6 part 1, 1961. American Rocket Society
p.8
However, the SD-3's twin-boom pusher design would become commonly used by

unmanned aerial vehicle An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controlle ...

s in later years.

Specifications

References

Citations

Bibliography