Folding - Fin Aerial Rocket The Mk 4 Folding - Fin Aerial Rocket ( FFAR ) , sometimes called the Mighty Mouse , was a 2 . 75 in ( 70 mm ) diameter unguided rocket weapon commonly used by U . S . military aircraft . It was intended as an air - to - air weapon to allow interceptor aircraft to shoot down enemy bomber s with greater range and effectiveness than machine gun s or cannon . It was later developed into a modular rocket motor for air - to - ground use . History . The advent of jet engines for both 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 amount of 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 cannon did not have the range or rate of fire to ensure a hit . Unguided rocket weapons 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 introduction in 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 . The original Mk 4 FFAR was about 4 ft ( 1 . 2 m ) long and weighed 18 . 5 lb ( 8 . 4 kg ) , with a high - explosive warhead of about 6 lb ( 2 . 7 kg ) . Like the Third Reich " Luftwaffe ' s " R4M projectile of World War II , it had folding fins that flipped out on launch to spin - stabilize the rocket , with the FFAR using half the number ( four ) of fins in comparison to the R4M ' s set of eight folding fins . Its maximum effective range was about 3 , 700 yards ( 3 , 400 m ) . Because of its low intrinsic accuracy , it was generally fired in large volleys , some aircraft carrying as many as 104 rockets . FFARs were the primary armament of many NATO interceptor aircraft in the early 1950s , including the F - 86D , F - 89 , F - 94C , and the CF - 100 . They were also carried by the F - 102 Delta Dagger to supplement its guided missile armament . The Mk 4 was dubbed " Mighty Mouse " in service , after the popular cartoon character . The Mighty Mouse was to prove a poor aerial weapon . Although it was powerful enough to destroy a bomber with a single hit , its accuracy was abysmal . Its spin rate was not high enough to compensate for the effects of wind and gravity drop , and the rockets dispersed widely on launch : a volley of 24 rockets would cover an area the size of a football field . As a result , by the late 1950s it had been largely abandoned as an aircraft weapon in favor of the guided air - to - air missile s then becoming available . The Mk 4 found other uses , however , as an air - to - ground weapon , particularly for the new breed of armed helicopter . A volley of FFARs was as devastating as a heavy cannon with far less weight and recoil , and in the ground - attack role its marginal long - range accuracy was less important . It was fitted with a more powerful motor to become the Mk 40 . The Mk 40 was a universal motor developed from the Mk 4 2 . 75 FFAR , and could be fitted with different warheads depending on the mission . Pods ( typically carrying seven or 19 rockets ) were created for various applications , and a wide variety of specialized warheads were developed for anti - personnel , anti - tank , and target - marking use . The FFAR has been developed into the modern Hydra 70 series , which is still in service . US Mk 40 FFAR Launchers . The United States was the primary user of this type of weapon and developed a number of different launching pods for it . Initially pods were intended to be disposed of by launching aircraft , either in flight or on the ground following a mission . With the advent of the armed helicopter , the need for launching pods that were reusable became apparent . Though the rocket was initially developed by the US Navy , the US Air Force and later US Army were most responsible for the development of rocket pods for all services . These pods are described as follows : Early UH - 1B / UH - 1C Gunships had the XM - 3 Subsystem using paired 24 round rectangular launchers mounted near the back edge of the sliding side doors . These pods were ground reloadable and were semi - permanent aircraft parts . The mounting point had been used to mount booms for 3 SS - 11 Launchers on each side for anti - tank missions . The co - pilot had a roof mounted sight and control box to fire these . Later UH - 1C and D aircraft had a mount on each side to carry a 7 round pod coupled with paired M - 60D machine guns . Some carried M - 134 Miniguns with 3000 rounds per gun instead , though these aircraft were normally used by Air Cavalry units , not the Aerial Rocket Artillery ( ARA ) units . Also various ground launchers using discarded aircraft pods were used for fire base defence . A towed configuration consisting of 6 19 round pods called a Slammer was tested for airborne infantry support . The range was approximately 7000 meters using Hydra 70 family rockets . Warheads for the Mk 40 Motor . With the development of the Mk 40 Mod 0 universal motor came the development of a considerable number of different warheads , as well as , a number of different fuzing options . A list of those warheads believed to be developed before the replacement of the Mk 40 motor with the Mk 66 motor is as follows :