The AIM-9 Sidewinder is a heat-seeking, short-range, air-to-air missile carried by fighter aircraft and recently, certain gunship helicopters. It is named after the Sidewinder snake, which detects its prey via body heat and also because of the peculiar snake-like path of flight the early versions had when launched.The Sidewinder was the first truly effective air-to-air missile, widely imitated and copied; yet its variants and upgrades remain in active service with many air forces after 5 decades.
The development of the Sidewinder missile began in 1946 at the Naval Ordnance Test Station (NOTS), Inyokern, California, now the Naval Air Weapons Station China Lake, California as an in-house research project conceived by William Burdette McLean. McLean initially called his effort "Local Fuze Project 602" using laboratory funding, volunteer help and fuze funding to develop what it called a heat-homing rocket. It did not receive official funding until 1951 when the effort was mature enough to show to Admiral "Deak" Parsons, the Deputy Chief of the Bureau of Ordnance (BUORD). It subsequently received designation as a program in 1952. The Sidewinder introduced several new technologies that made it simpler and much more reliable than its United States Air Force (USAF) counterpart, the AIM-4 Falcon that was under development in the same time period. After disappointing experiences with the Falcon in the Vietnam War, the Air Force replaced its Falcons with Sidewinders.
The primary advantage to the Sidewinder is its sophisticated, yet simple detection and guidance system. During WWII the Germans had experimented with infrared guidance systems in a large missile known as the Enzian, but were unable to get it to work reliably. The Enzian was guided by an IR detector mounted in a small, steerable telescope. A vane in front of the mirror shaded the detector, so the system could locate the target. By continually turning toward the telescope, the missile was guided toward the target using what is known as a pure pursuit. The Sidewinder improved on this concept with numerous changes and made it work.
The first combat use of the Sidewinder was on September 24, 1958 with the air force of the Republic of China (Taiwan). During that period of time, ROC F-86 Sabres were routinely engaged in air battles with the People's Republic of China over the Taiwan Strait. The PRC MiG-17s had higher altitude ceiling performance and in similar fashion to Korean War encounters between the F-86 and earlier MiG-15, the PRC formations cruised above the ROC Sabres immune to their .50 cal weaponry and only choosing battle when conditions favored them. In a highly secret effort, United States provided a few dozen Sidewinders to ROC forces and a team to modify their Sabres to carry the Sidewinder. In the first encounter on 24 Sept 1958, the Sidewinders were used to ambush the MiG-17s as they flew past the Sabres seemingly invulnerable to attack. The MiGs broke formation and descended to the altitude of the Sabres in swirling dogfights. Air combat had entered a new era.
Although originally developed for the USN and a competitor to the USAF AIM-4 Falcon the Sidewinder was subsequently introduced into USAF service when DoD directed that the F-4 Phantom be adopted by the USAF. The Air Force originally borrowed F-4B model Phantoms, which were equipped with AIM-9B Sidewinders as the short-range armament. The first production USAF Phantoms were the F-4C model, which carried the AIM-9B Sidewinder. The Air Force opted to carry only AIM-4 Falcon on their F-4D model Phantoms introduced to Vietnam service in 1967, but disappointment with combat use of the Falcon led to a crash effort to reconfigure the F-4D for Sidewinder carriage. The USAF nomenclature for the Sidewinder was the GAR-8 (later AIM-9E). During the 1960s the USN and USAF pursued their own separate versions of the Sidewinder, but cost considerations later forced the development of common variants beginning with the AIM-9L.
When air combat started over North Vietnam in 1965, Sidewinder was the standard Short Range Missile (SRM) carried by the US Navy on its F-4 Phantom and F-8 Crusader fighters and could be carried on the A-4 Skyhawk and on the A-7 Corsair for self-defence. The Air Force also used the Sidewinder on its F-4C Phantoms and when MiGs began challenging strike groups, the F-105 Thunderchief also carried the Sidewinder for self-defence. Performance of the Sidewinder and the AIM-7 Sparrow was not as satisfactory as hoped and both the Navy and Air Force studied their performance of their aircrews, aircraft, weapons and training as well as supporting infrastructure. The Air Force conducted the classified Red Baron Report while the Navy conduct a study concentrating primarily on performance of air-to-air weapons that was unofficially called and better known as the "Ault Report". The impact of both was modifications to the Sidewinder by both services to improve its ability to perform in the demanding air-to-air arena and increase reliability.
The Navy Sidewinder design progression went from the early production B model to the D model that was used extensively in Vietnam. The G and H models followed with new forward canard design improving ACM performance and expanded acquisition modes and improved envelopes. The "Hotel" model followed shortly after the "Golf" and featured solid state design that improved reliability in the carrier environment where shock from catapult launches and arrested landings had a deteriorating effect on the earlier vacuum tube designs. The Ault report had a strong impact in aspects of Sidewinder design, manufacture and handling.
Once the Air Force adopted the Sidewinder as part of its arsenal, it developed the AIM-9E introduced it in 1967. The "Echo" was an improved version of the basic AIM-9B featuring larger forward canards as well as a more aerodynamic IR seeker and an improved rocket motor. The missile, however still had to be fired at the rear quarter of the target, a drawback of all early IR missiles. Significant upgrades were applied to the first true dogfight version, the AIM-9J, which was rushed to the South-East Asia Theatre in July 1972 during the Linebacker campaign, in which many aerial encounters with North Vietnamese MiGs occurred. The Juliet model could be launched at up to 7.5.gs and introduced the first solid state components and improved actuators capable of delivering 90 lb.ft torque to the canards, thereby improving dogfight prowess. In 1973, Ford began production of an enhanced AIM-9J-1, which was later redesignated the AIM-9N. The AIM-9J was widely exported.
The Sidewinder is the most widely used missile in the West, with more than 110,000 missiles produced for the U.S. and 27 other nations. It has been built under license by some nations (including Sweden, which builds it under the local designation Rb24). The AIM-9 is one of the oldest, least expensive and most successful air-to-air missiles, with an estimated 270 kills world-wide to date.
It has been said that the design goals for the original Sidewinder were to produce a reliable and effective missile with the "electronic complexity of a table model radio and the mechanical complexity of a washing machine" – goals which were well accomplished in the early missiles. The United States Navy hosted a 50th anniversary celebration of its existence in 2002. The AIM-9 is one of the oldest, least expensive and most successful missiles in the entire U.S. weapons inventory.
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