Folding-Fin Aerial Rocket

The Mk 4 Folding-Fin Aerial Rocket (FFAR), also known as Mighty Mouse, was an unguided rocket used by United States military aircraft. 2.75 inches (70 mm) in diameter, it was designed as an air-to-air weapon for interceptor aircraft to shoot down enemy bombers, but primarily saw service as an air-to-surface weapon.

The advent of jet engines for fighters and bombers posed new problems for interceptors. With closing speeds of 1,500 ft/s (457 m/s) or more for a head-on interception, the time available for a fighter pilot to successfully target an enemy aircraft and inflict sufficient damage to bring it down was vanishingly small. Wartime experience had shown that .50 caliber (12.7 mm) machine guns were not powerful enough to reliably down a bomber, certainly not in a single volley, and heavy did not have the range or rate of fire to ensure a hit. Unguided rockets had been proven effective in ground-attack work during the war, and the Luftwaffe had shown that volleys of their Werfer-Granate 21 rockets, first used by elements of the Luftwaffe's JG 1 and JG 11 fighter wings on July 29, 1943 against USAAF bombers attacking Kiel and Warnemünde, could be a potent air-to-air weapon as well . The summer and autumn of 1944 saw the adoption of the folding-fin R4M unguided rocket for use underneath the wings of the Messerschmitt Me 262 jet fighter for bomber destroyer duties against the USAAF's Eighth Air Force heavy bombers.

The FFAR was developed in the late 1940s by the US Navy Naval Ordnance Test Center and North American Aviation. Mass production was established at the facilities of the Norris-Thermador Corp., Los Angeles, and the Hunter Douglas Division of the Bridgeport Brass Co., Riverside, CaliforniaFuzes were manufactured by the Bulova Watch Co., Jackson Heights, Queens, N.Y., with rocket propellant supplied by Hercules Inc., Wilmington, Delaware, metal parts supplied by Aerojet General, Downey, California, and miscellaneous spare parts were made by North American Aviation.

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