The Sikorsky Cypher and Cypher II are types of unmanned aerial vehicles developed by Sikorsky Aircraft Corporation. They are vertical takeoff and landing aircraft which use two opposing rotors enclosed in a circular shroud for propulsion.
In the late 1980s, Sikorsky Aircraft flew a small UAV named "Cypher", with coaxial rotors inside a torus-shaped airframe. The torus shroud improved handling safety and also helped increase lift. The first proof-of-concept Cypher was 1.75 meters (5.75 feet) in diameter and 55 centimeters (1.8 feet) tall, weighed 20 kilograms (43 pounds), and was first flown in the summer of 1988. This design was powered by a four-stroke, 2.85 kW (3.8 hp) engine and was mounted on a truck for forward-flight tests.[Wikipedia]