The AIM-9 Sidewinder started life in the United States as the XAAM-N-7 in 1949. The requirement was for a missile capable of engaging a target independently from the launch aircraft. During World War 2 Germany had experimented with using miniature infra red detectors to guide a missile completely autonomously from the launch aircraft. The XAAM-N-7 used this approach but utilised improvements in solid-state electronics to incorporate a fully integrated on-board infra-red seeker. Once aimed at a target object the missile could track it via its heat signature.

Loral/Raytheon/BGT AIM-9L

Initial trials were none to successful in any respect. One major problem was an inability to discriminate between objects. It was even possible for the missile to lock onto the Sun! However in 1956 the redesignated AIM-9B Sidewinder first entered service with the United States Air Force and Navy.

Over the years the Sidewinder has undergone various updates and improvements, each one resulting in a new letter designation. The main designations are :

• AIM-9A/B : Introduced in 1956 this was the first operational Sidewinder. It is also the most produced version at some 80,000 units many of which later found themselves as re-built -9E (or -9J) variants.
• AIM-9E : Introduced in 1967 this version introduced a new cooled seeker with improved tracking, aerodynamics and low altitude engagement capabilities.
• AIM-9H : Introduced in 1973 this Sidewinder saw the introduction of solid-state electronics, a new improved seeker head (with an off-boresight launch capability) and double delta fins. The AIM-9J used some of the solid-state technology and double deltas in re-builds of the AIM-9A/B.
• AIM-9L/M : These are now the two most common variants of Sidewinder in the inventories of the worlds airforces. The -9L saw substantial (and belated) improvements in the form of an all-aspect capability (previous versions had required the missile to be launched behind the target aircraft), a laser fuzing system, improved warhead, improved seeker (now argon cooled) and software (with much enhanced IRCCM, Infra Red Counter-Counter Measures) and modified aerodynamics. The -9M improved further upon the IRCCM of the -9L while introducing a lower smoke propellant.

While not always being at the forefront of technology (Britain for example had the worlds first all-aspect IR guided missile in the form of Red Top in 1967) it has remained the largest selling Western missile at some 110,000 units. In addition few other weapons have been battle tested to the same extent as the Sidewinder. It's first combat use was by Taiwanese aircraft in 1958, making up most of the air to air combat kills during the conflict with China. The Vietnam War saw the most extensive use of the weapon again with most air to air kills associated with Sidewinder. In 1982 during the Falkland's War, Royal Navy Sea Harrier's made 14 kills using the -9L variant.

During the late 1980's the US Air Force and Navies started work on the AIM-9R. This was to introduce a new Imaging Infra Red seeker (rather than a single spot seeker like previous systems), image processing software, on-the-fly upgradeability (through the use of EEPROM hardware) and improved IRCCM measures. Then in 1988 USAF and USN initiated Project Box Office with Raytheon. This was intended to yield a successor to the Sidewinder. It was to incorporate a new large array imaging seeker, electrically activated tail controls and digital autopilot. In 1991 the US Air Force pulled out of the AIM-9R program and the US Navy was forced to shut the program down later that year.

Project Box Office then became one of the candidates for what USAF/USN had termed AIM-9X or 'Evolved Sidewinder'. It lost out to a rival bid from Hughes (now part of Raytheon!). The new AIM-9X features the same 128 by 128 pixel Imaging Infra Red (IIR) seeker as Britain's ASRAAM (unsurprising given Hughes involvement in ASRAAM) and thrust vectoring control yet retains the AIM-9M motor and body. So again, the AIM-9X appears to not be as advanced as some of its rivals (ASRAAM, IRIS-T, Vympel R-73, Python-4) but it's hard to equate that with failure given the Sidewinder pedigree! The AIM-9X is supposed to enter service with both USAF and the USN in 2000/2001, export sales are yet to be confirmed. In June 1999 the first live firing of AIM-9X was carried out at White Sands Missile Range New Mexico from a USN F-18 Hornet.

* : Note that all ranges quoted are based on mean figures from various data sources. Actual achievable range will depend on a great number of factors and may be no where near those quoted.