Kettering Bug Aerial Torpedo
The Kettering Bug was an experimental unmanned aerial torpedo, a forerunner of present-day cruise missiles. It was capable of striking ground targets up to 75 miles (121 km) from its launch point, while traveling at speeds of 50 miles per hour.
The aircraft was powered by a two-stroke V4 40-horsepower (30 kW) DePalma engine. The engine was mass-produced by the Ford Motor Company for about $40 each. The fuselage was constructed of wood laminates and papier-mâché, while the wings were made of cardboard. The "Bug" could fly at a speed of 50 miles per hour (80 km/h). The total cost of each Bug was $400.
The Bug was launched using a dolly-and-track system, similar to the method used by the Wright Brothers when they made their first powered flights in 1903. Once launched, a small onboard gyroscope guided the aircraft to its destination. The control system used a pneumatic/vacuum system, an electric system and an aneroid barometer/altimeter.
To ensure the Bug hit its target, a mechanical system was devised that would track the aircraft's distance flown. Before takeoff, technicians determined the distance to be traveled relative to the air, taking into account wind speed and direction along the flight path. This was used to calculate the total number of engine revolutions needed for the Bug to reach its destination. When a total revolution counter reached this value a cam dropped down which shut off the engine and retracted the bolts attaching the wings, which fell off. The Bug began a ballistic trajectory into the target; the impact detonated the payload of 180 pounds (82 kg) of explosives.
Despite some successes during initial testing, the "Bug" was never used in combat. Officials worried about their reliability when carrying explosives over Allied troops. By the time the War ended about 45 Bugs had been produced. The aircraft and its technology remained a secret until World War II.