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 five decades. When a Sidewinder missile is being launched, NATO pilots use the brevity code Fox two in radio communication, as with all rear-aspect, or "heat seeking" missiles. AIM-9X: The next generation Sidewinder: After looking at advanced Short Range Missile (SRM) missile designs during the AIM portion of the ACEVAL/AIMVAL Joint Test and Evaluation at Nellis AFB in the 1974-78 timeframe, the Air Force and Navy agreed on the need for the Advanced Medium Range Air-to-Air Missile AMRAAM. But agreement over development of an Advanced Short Range Air-to-Air Missile ASRAAM was problematic and disagreement between the Air Force and Navy over design concepts (Air Force had developed AIM-82 and Navy had flight-tested Agile and flown it in AIMVAL). Congress eventually insisted the services work on a Joint effort and AIM-9M became the result thereby compromising without exploring the improved off boresight and kinematic capability potential offered by Agile. In 1985, the Soviet Union did field a SRM (AA-11 Archer/R-73) that was very similar to Agile. At that point, the Soviet Union took the lead in SRM technology and correspondingly fielded improved IRCM to defeat or reduce the effectiveness of the latest Sidewinders. As relations improved in the aftermath of the Soviet Union, the West became aware of how potent both the AA-11 and IRCM were and SRM requirements were readdressed. For a brief period in the late '80s, an ASRAAM effort led ...