The AIM-9 Sidewinder is a supersonic, heat-seeking, air-to-air missile carried by fighter aircraft. It has a high-explosive warhead and an infrared heat-seeking guidance system. The Sidewinder was developed by the U.S. Navy for fleet air defense and was adapted by the U.S. Air Force for fighter aircraft use.
AIM-9A: baseline version, originally designated AAM-N-7 Sidewinder I. It featured a blast-fragmentation warhead, which was triggered by an IR proximity or contact fuze. It could only be used for tail-on engagements of non-maneuvering targets. The missile was also very susceptible to other heat sources (sun, ground reflections, etc). Only 240 Sidewinder I missiles were built.
AIM-9B: originally designated AAM-N-7 Sidewinder IA or GAR-8 (for the U.S. Air Force), it was the full-rate production version.
AIM-9C: originally designated AAM-N-7 Sidewinder IC, this version uses a semi-active radar homing.
AIM-9D: originally designated AAM-N-7 Sidewinder IC, this version uses IR guidance.
AIM-9E: the first version specifically developed by the USAF. It was an improved AIM-9B with a new seeker with thermoelectric (Peltier) cooling, and a higher tracking rate of 16.5°/s. The Peltier cooling method allowed unlimited cooling time while the missile was on the launch rail. Externally, the AIM-9E differed from the AIM-9B by its longer conical nose section.
AIM-9F: a European development of the AIM-9B. It featured a now CO2-cooled seeker, some solid-state electronics, and a new nose dome.
AIM-9G: an improved AIM-9D. It featured SEAM (Sidewinder Expanded Acquisition Mode), which allowed the optics either to be slewed through a search pattern, or to be slaved to the aircraft's radar to acquire a target.
AIM-9H: the Navy developed this verslon. The main difference to the AIM-9G were solid-state electronics in the guidance and control system. The seeker tracking rate was also increased to 20°/s to complement the more powerful actuators.
AIM-9J: an improved AIM-9E developed for the U.S. Air Force. It had partial solid-state electronics, a longer-burning gas generator (increasing flight time), and more powerful actuators which drove new square-tipped double-delta canards. The latter feature doubled the single-plane "G"-capability of the missile.
AIM-9K: The designation ZAIM-9K was allocated by the U.S. Navy to a planned upgraded AIM-9H, but development was cancelled in favor of the joint USAF/USN AIM-9L.
AIM-9L: the USAF and U.S. Navy agreed to jointly develop the AIM-9L, a vastly improved Sidewinder based on the AIM-9H. Major development goals were ALASCA (All-Aspect Capability) and effective use against violently manoeuvering and high-speed targets at all ranges. The AIM-9L had new long-span pointed double-delta canards, a modified MK 36 solid-fuel rocket motor (MODs 8 through 11), and a new AN/DSQ-29 solid-state guidance and control section. Additional improvements include a completely new Argon-cooled Indium Antimonide (InSb) seeker, a DSU-15/B AOTD (Active Optical Target Detector) laser proximity fuze, and an improved annular blast-fragmentation warhead.
The AIM-9M features a reduced-smoke rocket motor, an improved guidance section designated WGU-4/B, better countermeasures resistance (IRCCM - Infrared Counter-Countermeasures), and improved overall reliability.
The AIM-9P is a USAF-sponsored development of AIM-9J/N, mainly intended for export to countries which can't afford, don't need, or are not allowed to receive the AIM-9L/M, however many AIM-9Ps are in the USAF inventory. Externally, the AIM-9P remains almost identical to the AIM-9J/N.
The AIM-9R was derived from the AIM-9M and equipped with a completely new WGU-19/B IIR (Imaging Infrared) seeker, offering much improved detection and tracking performance in daylight. The the planned production was cancelled due to lack of funding.
Following cancellation of the AIM-9R, development of a future dogfight missile based on the AIM-9M began. The missile was officially designated AIM-9X. It retains the MK 36 motor and the WDU-17/B warhead of the AIM-9M. The airframe is new, however, and has much smaller fins and canards for lower drag and higher flight performance. The guidance section is completely new, and features an IIR (Imaging Infrared) seeker. The new WPU-17/B propulsion section has a jet-vane steering system for significantly enhanced agility. The missile is compact enough to fit into the internal weapons bays of stealthy fighters like the F/A-22 Raptor and the F-35 Joint Strike Fighter, but can also be used on existing AIM-9 launchers. The AIM-9X is also fully compatible with the new JHMCS (Joint Helmet-Mounted Cueing System) for target acquisition.