U.S. Naval Museum of Armament & Technology
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 five decades. When a Sidewinder missile is being launched, NATO pilots use the brevity code Fox two in radio communication, as with all "heat seeking" missiles.
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 effective, yet simple target detection and guidance system.
Sidewinder-1. –1A, and 1B
The first generation included Sidewinder-1, -1A, and –1B. This generation had an uncooled lead sulfide (PbS) seeker, a tail-attack-only envelope and a limited range.
- Sidewinder 1 had a 1/2-mile range at sea level and very restricted envelope, about ±20° off the tail of the target.
- Sidewinder 1A (AIM-9B) incorporated a new gyro to improve performance above 45K feet. It was the first Sidewinder used in Vietnam. It was primarily an anti-bomber missile and dogfight missile second. It had a narrow firing cone off the tail, and a range of about 1 mile at sea level and 2.5 miles at 30K feet altitude. At lower altitudes ground infrared interfered with target IR. About 95,000 were manufactured for the U.S. and some allies. This version had 14 radio tubes compared to a contemporary Soviet IR missile, which had 34 radio tubes. The AIM-9B went through 14 modifications
- Sidewinder 1B. This version was originally to have been carried internally by the Grumman F11F Tiger. The project was eventually canceled.
Sidewinder 1C, AIM-9D, AIM-9E, AIM-9F, and AIM-9J
The navy's second generation included AIM-9C and 9D Sidewinders, originally known as SARAH (semiactive radar alternative head) and IRAH (infrared alternative head), respectively. These sidewinders had better seekers and longer ranges. This generation also included improved versions of the 9D, the AIM-9G and the AIM-9H. The Air Force ignored China Lake for its second generation and got Philco (Ford) to provide improved head for some 12,000 AIM-9Bs. These became AIM-9E, AIM-9F, and AIM-9J.
- Sidewinder 1C began the second generation of expanded-envelope Sidewinders. An expanded envelope was needed because it was possible to escape the earlier AIM-9B by turning tightly if a pilot saw it coming. It was also decided to develop not only an infrared head but also an alternative radar head for the missile–the infrared alternative head (IRAH) and the semiactive radar head (SARAH). The IRAH became Sidewinder 1C Mod 29 (AIM-9D) and the SARAH Sidewinder 1C Mod 30 (AIM-9C). The missiles were identical except for the seeker heads.
- AIM-9D. The AIM-9B technology was updated and became the AIM-9D. The update included a redesign of the gyro optical system. The seeker (irfrared alternative seeker (IRAH)) used high-pressure nitrogen gas cooling to increase the sensitivity of the lead sulfide cell. The seeker still had bulky tube electronics so the cooling system was fitted into the launcher instead of the missile. The 9D was far better than the 9B at gaining and maintaining a lock on targets. A more powerful rocket motor tripled the 9B's range up to 11 miles.
- AIM-9C (SARAH). China Lake also pursued a semiactive radar alternative head (SARAH). The IR versions were limited to tail attacks, so the radar head was pursued. While the AIM-9C was used in Vietnam and shot down its share of MiGs, it was too closely integrated with the F-8 Crusader. When the Crusaders were retired, so was the AIM-9C since no other aircraft had a radar capable of using the AIM-9C.
- AIM-9E, -9J. Since the Air Force was not happy about using navy missiles they decided not to buy the AIM-9D. Instead, they got Philco-Ford to develop versions of the Sidewinder for air force specification. To create the AIM-9E, Philco-Ford installed new head and control surfaces on the 9B frame and motor, reduced drag and designed wider gimbal angles. The 9E, however, lacked the range and target discrimination of the 9D, and the Air Force pilots and turned to the SPARROW missile. The AIM-9J was a solid-state version of the AIM-9E with superior control surfaces. Both missiles were inferior to the navy's 9Cs and 9Ds. The Air Force eventually gave up on the 9E and 9F, and accepted the navy's AIM-9G.
- AIM-9G. The AIM-9G was essentially a 9D with one key improvement–the Sidewinder expanded acquisition mode (SEAM). The seeker was slaved to the aircraft's acquisition radar, and it could revolve 25 degrees in a circular scan, instead of being aimed straight ahead. This improved the odds of acquiring targets. The 9G also had a number of solid-state modules. Only about 1850 of an order for 5000 9Ds were produced before the rest of the order were converted to 9Gs.
- AIM-9H. The AIM-9H was essentially a solid-state version of the AIM-9G with the same specification. However, it turned out to be more reliable than the 9G. The 9H entered the fleet in 1972, too late for the Vietnam War.
- Chaparral (MIM-72). A ground-launched version of the Sidewinder was developed for the Army. It used the 9D seeker it was fielded by the Army and the Israelis. The first kill by Chaparral was a Syrian MiG-17 in the October 1973 Yom Kippur War.
AIM-9L, AIM-9M, and AIM-9M(R)
The third generation began with a joint navy-air force missile, the AIM-9L Super Sidewinder. It was followed shortly by the AIM-9M and AIM-9M(R), which incorporated improved counter-countermeasures. The AIM-9M(R) refers to a retrofit of 9M including several modifications.
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AIM-9L. The AIM-9L's double-delta canards gave the weapon an incredible 35g capability making it virtually impossible for a plane to out turn the AIM-9L During the Falklands War the British had an 87% success rate with the missile. The missile incorporated an indium antimonide detector.
- AIM-9M. The Air Force wanted better defense against countermeasures. A Product Improvement Program (PIP) was begun for the AIM-9L, the AIM-9L PIP. This program turned into the AIM-9M. In addition to better counter-countermeasures, the 9M had better performance against cloud and terrain backgrounds. New microchip electronics gave the missile enough processing power to sort out false targets, both background and countermeasures, from the real one. The AIM-9M and modified versions are still in use today
AIM-9R
AIM-9R was an attempt at a major change in imaging, replacing the gyro with a charged-coupled device (CCD). It passed its tests but never reached operational status. Due to soaring costs and project delays, the program was canceled in favor of modifications to the AIM-9M.
AIM-9X
The fourth and latest generation is the AIM-9X. The AIM-9X Sidewinder, developed by Raytheon, entered service in November 2003 with the USAF (lead platform is the F-15C; USN lead platform is the F/A-18C) and is a substantial upgrade to the Sidewinder family featuring an imaging infrared focal plane array (FPA) seeker with claimed 90° off-boresight capability, compatibility with helmet-mounted displays such as the new U.S. Joint Helmet Mounted Cueing System, and a totally new three-dimensional thrust-vectoring control (TVC) system providing increased turn capability over traditional control surfaces. It retains the same rocket motor, fuze and warhead of the AIM-9M but its lower drag gives it improved range and speed. AIM-9X also includes an internal cooling system eliminating the need for use of nitrogen bottles (US Navy and Marines) in the launch rail or Argon internal bottle (USAF). It also features an electronic safe and arm device (ESAD) allowing reduction in minimum range and reprogrammable InfraRed Counter Counter Measures (IRCCM) capability that coupled with the FPA provide improved look down into clutter and performance against the latest IRCM. Though not part of the original requirement, AIM-9X has demonstrated a Lock on After Launch (LOAL) capability, allowing for possible internal use for the F-35 Joint Strike Fighter, and even in a submarine launched configuration for use against ASW platforms.