Cypher UAV(Unmanned Aerial Vehicle), 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 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. It led to a true flight prototype Cypher that weighed 110 kilograms (240 pounds), had a diameter of 1.9 meters (6.2 feet) and was powered by a compact, 40 kW (53 hp) rotary engine. After an initial free flight in 1993, the Cypher prototype was used in flight tests and demonstrations through most of the 1990s, ultimately leading to a next-generation design, the Cypher II, which was a competitor in the United States Navy VT-UAV competition. The single prototype first flew in April 1992 and flew untethered in 1993. Since then, over 550 demonstration flights have been made for the US government.