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In the early days of aerial combat, the pilots who prevailed were the ones who best learned how to maneuver their aircraft, manage their energy, and employ their armament, the gun. These successful �dogfighting� skills became a part of their everyday training to help ensure future survivability of the aircrew. During WWII, many U.S. aviators faced adversaries with equal or comparable skills and a need was born to provide U.S. flyers with a combat edge. In the late 40's there were missiles with radar detecting systems aboard but they were dismal failures at downing aircraft. Some attempts at Infrared guidance had been tested without much success.

In 1949, a small team at NOTS (later NWC) China Lake, led by Dr. McLean, investigated the passive Infra Red homing problem, with limited financial means. The name of this project was taken from the name of a snake which is a denizen of the Mojave Desert called the Sidewinder.

McLean sketched what would become the future of dogfighting weapons, the AIM-9 Sidewinder missile. Surprisingly, the result of this low-profile research project is still known as one of the world's leading dogfight missiles. As if the financial limitations were not restrictive enough, the team imposed on itself one further restriction: it chose for an airframe of only 5 inch (127mm) diameter, which made fitting in the necessary electronics (still vacuum-tube in those days) a major challenge. The research led to a contract, awarded to Philco in 1951, for a homing head.

The primary advantage to the Sidewinder was its use of a very sophisticated detection/guidance system. In WWII the Germans had experiments with infrared guidance systems in a large missile known as the Enzian but were unable to get it to work reliably. The system used an IR detector mounted in a small steerable telescope, and used a vane in front of the mirror to tell on which side of center the target was in order to guide. By continually trying to turn the missile body toward the current direction of the telescope, the missile would guide toward the target using what is known as a pure pursuit.

The Sidewinder improved on this in a number of ways. The first was to replace the "steering" mirror with a system using a mirror that was rotating around a shaft pointed out the front of the missile, with the detector mounted in a fixed location in front of it (not to the mirror). Instead of attempting to track the target in the mirror, the IR sensor would see the target as brief flashes as the mirror lined up with the target. By knowing where the flash was as the mirror spun, the direction (radially) to the target was also known. In addition this system could track the angle-off to the target in a clever manner. If the target was further to the side of the field of view, the flash seen in the detector would be shorter due to the mirror's higher rate of motion at the outside.

Finally this sort of signal made the tracking system both simpler and much better. Instead of simply pointing the missile at the target (which is inefficient) the guidance system, the Sidewinder "remembered" each flash's direction and time. By attempting to zero out the changes, instead of the difference between the detector and missile angles, the Sidewinder flew a course known as proportional pursuit, which is much more efficient and makes the missile "lead" the target.

However this system also requires the missile to have a fixed angle of flight. If the missile spins at all, the timing based on the speed of rotation of the mirror is no longer accurate. Correcting for this spin would normally require some sort of sensor to tell which way is "down" and then adding control inputs to correct it. Instead the Sidewinder engineers came up with a very clever solution. Small control surfaces were placed at the rear of the missile with spinning disks on their outer surface. Airflow over the disk would spin them to a high speed, and if the missile started to roll, the gyroscopic force of the disk would drive the control surface into the airflow and produce the opposite control input. Thus the Sidewinder team replaced a potentially complex control system with a small bit of metal.

A prototype Sidewinder, the XAAM-N-7 (later AIM-9A), was first fired successfully in September 1953. The initial production version, designated AAM-N-7 (later AIM-9B), entered operational use in 1956, and has been improved upon steadily since. The first combat use of the Sidewinder was in 1958 with the air force of the Republic of China on Taiwan. During that period of time, the ROC was engaged in air battles with the People's Republic of China over the Taiwan Strait. The United States provided a few dozen Sidewinders to ROC forces, which used them to great effect against PRC MiG-15s, adding a new element to an air war which had formerly been fought only with guns.

Sidewinder is undoubtedly the most influential heat-seeking missile in the history of air warfare. More than 200,000 of the missiles have been built for 40 countries around the world and it has achieved more than 175 kills in air combat. The Sidewinder originally developed and improved at China Lake became the yardstick against which all heat-seeking missiles have been measured.

Although originally developed for the USN, the Sidewinder was subsequently adopted by the USAF as 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.

The Sidewinder subsequently evolved through a series of upgraded versions with newer, more sensitive seekers with various types of cooling and various propulsion, fuse, and warhead improvements.

Early Sidewinders consisted of sections of cylindrical aluminum tube, with the seeker head fitted at the front end together with the control fins. The rear end has four fixed fins, each containing a so-called 'rolleron'. These patented rollerons are in fact small wheels, one of which is mounted at the rear tip of each fixed tailfin. These wheels are slightly milled at the edges, so they are made to spin at high-speed by the slipstream. The rollerons act as air-driven mini-gyros, their inertial moment resisting every change in attitude. This way, they tend to roll-stabilize the missile. Both tailfins and control surfaces are in a cross-like arrangement.

The missile's main components are an infrared homing guidance section, an active optical target detector, a high-explosive warhead, and a rocket motor. The infrared guidance head enables the missile to home on target aircraft engine exhaust. An infrared unit costs less than other types of guidance systems, and can be used in day/night and electronic countermeasures conditions. The infrared seeker also permits the pilot to launch the missile, then leave the area or take evasive action while the missile guides itself to the target. The early models used an uncooled PbS (Leadsulfide) seeker which yielded a 70% SSKP (Single-Shot Kill Probability) in ideal conditions, but extremely bad results in less-than-ideal circumstances. The seeker showed a tendency to lock-on to the sun or reflections from water surfaces. De original solid-engine was produced by Hunter-Douglas, Hercules and Norris-Thermador, and accelerated the missile to Mach 2.5 in 2.2 seconds.