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The AIM-9 Sidewinder is the most famous, successful, and longest-lived air-to-air missile ever fielded
Country of origin AIM-9A/B AIM-9C/D
Country of origin United States
Entered service 1956 Late 1950s
Missile
Missile length 2.83 m 2.87 m
Missile diameter 0.13 m 0.13 m
Fin span 0.56 m 0.63 m
Missile weight 70 kg 88 kg
Warhead weight 4.5 kg 11 kg
Warhead type HE-FRAG Continuous rod
Range of fire 4.8 km 18 km
Guidance Infrared homing Semi-active radar homing (AIM-9C), infrared homing (AIM-9D)
Unquestionably the most famous and successful air-to-air missile, the AIM-9 Sidewinder is still in full production and widespread service today, 60 years after its introduction. It has been used by a multitude of air arms throughout the world, and more than 1 000 have been launched in combat, shooting-down almost 300 aircraft. The US Air Force (USAF) itself has contracts for maintenance and logistical support for the Sidewinder into 2055, and Stephanie Powell, a spokeswoman for that service, has stated that "...due to its relative low cost, versatility, and reliability it is very possible that the Sidewinder will remain in Air Force inventories through the late 21st century."
The origins of this weapon date back to 1946 at the Naval Ordnance Test Station near Inyokern, California; a facility today referred to as Naval Air Weapons Station China Lake. This concept for an infrared-guided missile was euphemistically dubbed "Local Fuze Project 602" by its creator, William B. McLean. Surprisingly, this was not the result of an actual US military requirement, but a sort of a "pet project" of McLean himself. In 1950, the design was officially named the "Sidewinder", after Crotalus cerastes, a venomous rattlesnake known to use infrared vision to hunt its prey.
McLean spent years trying to convince the US Navy to test the Sidewinder, and it wasn't until 1951 that McLean convinced the Deputy Chief of the Bureau of Ordnance, Admiral William "Deak" Parsons, to actually fund it. Though even with funding, the Sidewinder wasn't ordained as an official US Navy program until 1952. Although by then, the US Navy finally realized they were on to something. The USAF had their own infrared guided missile program (which later resulted in the AIM-4 Falcon), and even in its conceptual phase, the Navy's weapon was already clearly much more efficient and cost-effective than its USAF counterpart. For political reasons, the Navy neither wanted to acquire nor fund a USAF weapon, and the Sidewinder couldn't have been presented at a better time.
Thanks in part to a fully-realized design phase, the development of the missile proceeded quickly. Initially named the Sidewinder 1, the prototypes had a markedly different layout from the familiar production models of the Sidewinder, with square fins and a much longer rocket motor. The first test launches occurred in 1951, while the first powered launch from and aircraft took place on September 3rd 1952. Barely a year later, the Sidewinder I --- now designated the XAAM-N-7 --- achieved its first powered and guided launch against a target drone, on September 11th 1953. An additional 51 guided launches took place through 1954 as the design was further refined, and in 1955, the Navy finally approved the missile for production. Deliveries to the Navy soon followed, and In the following year, the Sidewinder was declared operational. The USAF's competing AIM-4 Falcon entered service in the same year, though it was a much less impressive feat, considering that its development was twice as long.
Interestingly, while the Sidewinder today is almost universally associated with jet aircraft, those involved in the earliest tests were all propeller-driven; the prototypes were launched from AD4 Skyraiders, and the target drones were converted F6F-5K Hellcats.
Prior to the early 1960s establishment more familiar tri-service designation system now in use, the first model of the Sidewinder was designated the AAM-N-7 Sidewinder I, while the subsequent three models were designated AAM-N-7 Sidewinder IA (or GAR-9, under the USAF designation system), AAM-N-7 Sidewinder IC (SARH), and AAM-N-7 Sidewinder IC (IR). For simplicity, these missiles will be referred-to in the rest of this article by their tri-service designations; the AIM-9A, AIM-9B, AIM-9C, and AIM-9D, respectively.
The Sidewinder has an iconic and immediately recognizable appearance, with a long and narrow cylindrical fuselage, crucifix-pattern fore and aft fins, small and triangular front fins, and proportionately large trapezoidal aft fins (though the recent AIM-9X has tiny aft fins). The nose may be conical or dome-shaped, depending on the variant; and also straight or tapered. The foreword fins on the A through D models are triangular, pointed, and swept-back, though the C and D models have a noticeably larger fin with a more shallow sweep. A rolleron --- a wheel-like device mounted in a tab-shaped fixture, whose function is described below --- is located on the outer aft corners of the aft fins (the AIM-9X has no rollerons, though that missile is outside the subject matter of this particular article).
The body and fins of the Sidewinder are constructed almost entirely of aluminum, the fuselage consisting of a long tube with at least two sections. The forward fins are solid metal, while the aft fins have a thin metal skin, and an aluminum honeycomb internal frame. The nose cone of the seeker head on the A and B models was initially made of glass, but this was quickly replaced in production with a cone made of silicium (a similar silicon-based substance, which is more infrared-transparent than glass). All Sidewinders are powered by solid fuel rocket motors, though the composition of the fuel and the casing varies from one motor to another.
Nearly all AIM-9 Sidewinders employ infrared homing guidance, though the AIM-9C was an exception (more on that below); in fact, the AIM-9 was named the "Sidewinder" as a reference to the species of venomous pit viper snake of the same name known to have passive infrared vision (a widely-held myth is that the Sidewinder missile earned its name from its distinctive serpentine handling in flight, but the name was assigned before any were actually launched yet --- and thus, before it's handling tendencies were fully understood). The guidance systems in all early Sidewinders (the A, B, C, and D models) lacked solid state electronics, and instead utilized vacuum tubes.
The AIM-9A and B have a seeker head with an uncooled PbS (lead sulfide) detector, which only had a field of view of 4 degrees and a tracking angle of 11 degrees/second; thus, these missiles had to be pointed almost directly at the target in order to attain a lock. Engaging maneuvering targets with these missiles were inadvisable, and due to the poor infrared sensitivity and filtration of these seeker heads, engaging aircraft from any direction other than directly from behind was effectively impossible. Moreover, the AIM-9A/B seeker head also had a tendency to lock-onto the wrong heat sources, such as sun glare, ground reflections, and heat from the smoke stacks of factories. As the A and B models are almost identical, it is unclear if any attributes of their seekers differ.
The AIM-9C is unique among all production Sidewinders, in employing semi-active radar homing guidance instead of infrared guidance. This made the AIM-9C the first Sidewinder capable of a head-on engagement (or any apart from tail-chasing, for that matter), though it could only be used by an aircraft capable of illuminating the target with radar. It was also immune to the interference that plagued the infrared seeker heads of the A and B models, but the C model had problems of its own. It was easily jammed, had no "look down" capability (i.e., the ability to "see" a target below the horizon), could be foiled by radio interference, and in practice could not distinguish between an aircraft and a chaff cloud.
The AIM-9D introduced a new seeker infrared head, which still used the familiar PbS detector, but also introduced a liquid nitrogen coolant. Combined with the new silicium nose cone, this greatly increased the sensitivity and resolution of the D model over the previous missiles. The new detector had a narrower field of view at only 4.5 degrees, but also a slightly wider tracking angle of 12 degrees/second.
The AIM-9A and B models are propelled by a 40 kg Thiokol/Aerojet Mk.17 solid fuel rocket motor, with a burn duration of 2.2 seconds. This allows the missile to reach its full speed only a few seconds after launch. The forward fins function as all-moving canards, and are powered by a hot gas generator with a 20-second burn time.
This C and D models were instead powered by a Hercules Mk.36 solid fuel rocket motor. This 44.9 kg device boasts a 4130 steel casing, a Phenolic nozzle, an Ethylene Propylene Diene Monomer (EPDM) rubber insulator, a Pyrogen igniter, and an Hydroxyl-Terminated Polybutadiene (HTPB) fuel compound that produces relatively little smoke. The thrust produced by the Mk.36 has not been published, but it is presumably greater than that of the Mk.17 motor. This is also a much more efficient engine, as the C and D models have more than triple the range of the A and B models.
All four models of the early Sidewinders accelerate to their top speed within seconds of being launched, and attain supersonic speed. The A and B models have a top speed of Mach 1.7 (2 100 km/h), while the more powerful motor used in the C and D models gives them a flight speed of Mach 2.5 (3 087 km/h). These missiles are only propelled in flight over a few kilometers, after which they rely on inertia to reach their target. The Sidewinder's structure is capable of withstanding 25 Gs of force (well over twice the maximum G tolerances of the human body, and nearly three times the tolerances of many fighters that were in service during the 1950s), though this doesn't necessarily make it more maneuverable overall than a manned fighter aircraft, as the closure rate can be too fast for the missile to correct. The aforementioned rollerons are a vital component of the Sidewinder as well, because they keep it on course by acting as stabilizing gyros during flight.
The AIM-9A and B were armed with a 4.5 kg High Explosive Fragmentation (HE-FRAG) warhead, which had a lethal radius of 9 m, and was triggered by an infrared proximity fuze. Although it had a satisfactory shrapnel pattern, this munition proved wanting in testing against larger airframes typical of the supersonic fighters and large bombers then expected to enter service soon. The AIM-9C and D switched over to the Mk.48, an 11 kg warhead of considerably greater power. The Mk.48 is a continuous rod warhead, whose principle of operation is similar to an HE-FRAG munition, but instead of wrapping the sides of the bursting charge with pre-formed shrapnel, it is instead enveloped by a thick steel wire compressed and folded down into a tube. When a continuous rod munition detonates, the tube unravels at supersonic velocities, creating a rapidly expanding ring of wire that can inflict major structural damage against large aircraft, and destroy smaller aircraft by literally slicing them in half. The welds at the ends of the wire segments break at a set radius, beyond which the effectiveness and reliability of the warhead diminishes significantly, so continuous rod warheads often employ multiple rings.
The Sidewinder was also an extremely cheap weapon compared to most other air-to-air missiles. An AIM-9B cost only $20 000 in the late 1960s, compared to $500 000 for a single AIM-7B Sparrow in the same era. Coupled with its combat results and vast numbers, it was also both expendable and highly cost-effective. For some nations that acquired the Sidewinder, it was the first air-to-air missile their air arms ever operated (for example, South Vietnam and Yemen), and it is doubtful they could have afforded an air-to-air missile capability had the Sidewinder (or at least one of its equivalents) not been available.
Another important (and often overlooked) aspect of the Sidewinder is that it gave an air-to-air missile capability to many aircraft that would have otherwise been unable to attain this. For example, F-86 Sabre, A-4 Skyhawk, and A-10 Thunderbolt II were originally designed with little to no consideration of missile combat against other aircraft, but the Sidewinder was easily integrated into them, making these aircraft significantly more formidable in air combat.
The combat debut of the AIM-9 Sidewinder occurred on September 24th 1958, over the Taiwan Strait. The Republic of China Air Force's (ROCAF's) primary fighter at the time was the F-86 Sabre, against which the People's Liberation Army Air Force (PLAAF) had skillfully exploited the speed and altitude advantages of their MiG-17s. Anticipating another such battle, the US military had secretly supplied the ROCAF with AIM-9B Sidewinders to even the odds. USAF F-100 Super Sabres posed as high-flying MiG-17s in dissimilar air combat training with ROCAF F-86 pilots, who were taught how to use Sidewinders to engage hostile aircraft from below, while the US Marine Corps back-fitted the F-86s to carry these missiles. When the MiGs made their move on the 24th and used the usual tactics, they got a nasty surprise from below, and 10 of them were swatted from the sky by Sidewinders before they knew what hit them. The ROCAF F-86s took no losses. This event upset China's entire air combat strategy, as neither their speed or altitude advantages could off-set the threat posed by the Sidewinder, and barely a week later, the PLAAF's intrusive flights into Taiwanese airspace finally ended (for the time being).
One of the most surprising outcomes of the dogfight over the Taiwan Strait wasn't realized until one of the surviving MiG-17s returned to China. The pilot hadn't noticed any damage to the aircraft during the mission, but as the MiG taxied onto the apron at its airbase, startled ground crews noticed an unexpected accessory on the airframe; a missile lodged in its fuselage. This event being prior to the Sino-Soviet Split, Soviet technicians quickly retrieved the missile, and brought it back to Russia for further study. They were astonished not only to find the missile almost totally undamaged, but also how far ahead of Soviet aviation missile technology the US had already progressed. Further research eventually resulted in a reverse-engineered Soviet "Sidewinder", theR-3 (code-named AA-2 or Atoll by the West), but that's a different story altogether.
There were many doubts during the early Cold War of the Sidewinder's viability against bombers, like the M-4 (Western reporting name Bison) or the Tu-95 (Western reporting name Bear). After all, these were large aircraft, and the Sidewinder was a small missile. However, the Sidewinder actually did manage to shoot-down one such aircraft --- though as fate would have it, the victim was a USAF B-52 Stratofortress. On April 7th 1961, F-100A Super Sabre #53-1662, belonging to the 188th TFS, New Mexico, performed a practice interception of B-52B #53-0380 out of Biggs air force base, Texas, when a Sidewinder carried by the F-100 accidentally launched. The missile was locked onto the B-52, and the F-100 pilot never pulled the trigger, a series of malfunctions in the electrical system connected to the missile caused it to launch. The pilot immediately warned the B-52 crew of the launch, but on a large, lumbering strategic bomber in the days before they carried electronic countermeasures, nothing could stop the missile. It struck and detonated against the inboard left engine pod, shredding it and tearing through the skeletal structure of the wing; moments later, the wing snapped in half, and the B-52 simply fell out of the sky. In seconds, the AIM-9B had proven it could fell even the most formidable aircraft in service at the time, though it was hardly a proud moment for the USAF or Raytheon.
The AIM-9A and AIM-9B also saw extensive combat use in the Vietnam War, the 1965 Indo-Pakistani War, the Six Day War, the War of Attrition, the 1971 Indo-Pakistani War, the Yom Kippur War, the Iran-Iraq War, the Falklands War, and many other conflicts.
However, since the Vietnam War is generally considered the "acid test" for how well the early AIM-9 Sidewinders performed, its results in that war are worth noting. A total of 425 were launched in combat, achieving 80 kills, for a Probability of Kill (pK) ratio of 18%. While this is a poor result by contemporary standards, it must be noted that it is the best performance of any missile used in that war by a wide margin. The AIM-4 Falcon performed badly over Southeast Asia, with only 5 kills to show for 54 launches (a 10% pK ratio), and the Vietnamese People's Air Force's R-3s did no better; it was the poor performance of the Falcon that prompted the USAF to re-arm its F-4 Phantom IIs with AIM-9 Sidewinder and AIM-7 Sparrow missiles instead of the Falcons they had been using, though ultimately the Sparrow fared worst of all --- its pK ratio of 0.05% was a disaster.
The AIM-9D was used extensively by the US Navy during the Vietnam War, achieving a total of 36 confirmed kills during the conflict (out of 46 Navy kills with all types of Sidewinders used in that war). By comparison, AIM-9Gs launched by the Navy achieved 9 kills, and only a single Navy kill was confirmed using an AIM-9B. The AIM-9B played a much more important part in the USAF, however. Out of 34 USAF kills using Sidewinders in the same conflict, 25 were with AIM-9Bs, with the remainder going to the more advanced AIM-9E and AIM-9J. While this doesn't necessarily suggest the AIM-9B was the most capable Sidewinder variant used during the Vietnam War, it certainly does demonstrate how heavily the USAF relied on it.
However, the real irony was that while the Sidewinder had practically become the universal air-to-air missile of the US military by 1970, it wasn't even supposed to be in service at all by then. USAF fighters that couldn't use the Falcon only carried the Sidewinder as a stop-gap measure until a future USAF-exclusive missile could carry it, and prior to the Vietnam War, the only weapon ever intended for USAF F-4s was the Falcon. Similarly, the Navy saw the Sidewinder as an obsolete weapon for obsolete aircraft, and the F-4 had not yet been back-fitted to use it; by the end of the decade, the F-4 was the only contemporary Navy fighter to remain in frontline service, and the only weapon this aircraft was meant to use was the Sparrow, while the subsequent (though later canceled) F-111B was to use the Sparrow and the AIM-54 Phoenix. What changed all of this was the reality of war. Even the most optimistic assessments of the Sparrow considered it expensive and sub-optimal for use against fighters, so Navy F-4s bound for Southeast Asia were back-fitted to use the "old-fashioned" Sidewinder to give it a few more rounds to fire. This was due to strong institutional bias in both services toward close air combat tactics, which prior to the Vietnam War were regarded as hopelessly obsolete in the face of the new aerial warfare technologies of the time (this was also the case in the US military with all prior air wars, going back to the Spanish Civil War... as well as every air war *since* the Vietnam War).
The Sidewinder's success in subsequent combat actions accidentally turned the Sidewinder into a permanent fixture of the US armed services, as "pre-Phantom" fighters that couldn't use the "missiles of the future" in all the US armed services carried a significant portion of the air-to-air combat. Aircraft that were armed with the "missiles of the future" performed poorly against MiG-17s that pre-dated even the Sidewinder. This realization was finalized two studies into the matter, a USAF document whose contents are still classified, and a US Navy document titled the "Air-to-Air Missile System Capability Review" --- though it is better known as the Ault Report. The contents of these reports finally made short-range air-to-air missiles a recognized necessity in the US military, though the USAF and US Navy once again saw the Sidewinder only as a stop-gap. The new plan was to replace it with a new generation of short-range, infrared homing air-to-air missile by the mid-1970s, which would eventually result in the AIM-82 and AIM-95 AGILE programs, both of which ultimately ended up being canceled in favor of yet another generation of the Sidewinder... but again, that's another story in and of itself.
The AIM-9B is one of the most numerous variants of the Sidewinder, with over 80 000 (out of some 200 000 Sidewinders of all types) manufactured in the US and Western Europe. It is unclear how many AIM-9A missiles were produced, and the aforementioned 80 000 figure may include them as well. However, only 1 000 AIM-9Cs and 1 000 AIM-9Ds were ever produced, making them some of the rarest Sidewinders.
The AIM-9C was never launched in anger. The remainder were eventually converted into the AGM-122 Sidearm, a small anti-radiation missile introduced into US military service in 1986.
At present, some militaries still use the AIM-9A and AIM-9B, though their days are clearly numbered. Some of them may end up being re-manufactured into more advanced missiles (which had been done before, resulting in the AIM-9G and AIM-9H), but their most likely fate is to be gradually expended in training or combat, destroyed by demolition, or simply left in the armories long past the expiration date of their final service life extensions.
However, the Sidewinder has affected the outcome of military in a way that few other individual weapons ever have, and this family of missiles now over 60 years old is expected to live-on for almost another century in active service around the world, if not even longer. And it was all thanks to the imagination of a bored engineer, who worked on a personal side project in his spare time.
Variants
Sidewinder 1: The prototype of Sidewinder had a similar seeker to that used on the production AIM-9A, but it had rectangular fins and a longer rocket motor that gave it a radically different appearance. Coincidentally, this shape gave the Sidewinder 1 a similar appearance to the FIM-92 Stinger, a much later Raytheon product.
AIM-9A (AAM-N-7 Sidewinder I): First production model for the US Navy. Employed infrared guidance. It was first successfully fired in 1953. This missile was approved for production by the US Navy in 1955. It entered service in 1956.
AIM-9B (AAM-N-7 Sidewinder IA): Virtually identical to the AIM-9A, with indistinguishable performance, but this nonetheless became the definitive early Sidewinder missile. It was adopted in 1956. The first combat use of this missile was in 1958. Over 80 000 were manufactured, making this the most numerous Sidewinder model. Designated as the "GAR-8" in USAF service, until the tri-service designation system was adopted. Since its introduction the AIM-9B has been steadily improved.
AIM-9C (AAM-N-7 Sidewinder IC (SARH)): Longer-range Sidewinder with a Semi-Active Radar Homing (SAHR) guidance for the US Navy. It was developed for the US Navy's F-8 Crusader. The AIM-9C is one of the rarest Sidewinders, only some 1 000 AIM-9Cs were manufactured, and most were later converted into AGM-122 Sidearms (see below).
AIM-9D (AAM-N-7 Sidewinder IC (IR)): Infrared-guided version of the AIM-9C for the US Navy. As with its predecessor, only about 1 000 were built.
AIM-9E Sidewinder: Improved AIM-9B developed by the USAF. About 5 000 AIM-9Bs were converted into AIM-9Es.
AIM-9F Sidewinder: Improved AIM-9B developed by BGT in Germany. Most European AIM-9Bs were converted to AIM-9F standard.
AIM-9G/H Sidewinder: Improved AIM-9D variants, developed for the US Navy.
Sidewinder F.G.W.2: AIM-9B Sidewinder produced under license in the UK.
R-3, also referred as the K-13 (Western reporting name AA-2 or Atoll): Soviet infrared-guided air-to-air missile, based on a reverse-engineered AIM-9B. Manufactured in vast numbers and exported by at least 26 nations, the R-3 and its derivatives are still in service with some air forces to this day.
Diamondback: Nuclear-tipped air-to-air missile based on Sidewinder technology. Never left the drawing board.
AGM-87 Focus: AIM-9B converted for air-to-ground combat. Though reportedly successful in combat, no further conversions were made after the first batch was expended.
AGM-122 Sidearm: Anti-radiation missile based on the AIM-9C. As with the Focus, it was highly successful in combat, but no attempt was made to replenish or replace them once they were all expended. Given that 700 were converted from AIM-9Cs, almost every remaining missile of that type must have been converted.
RayWinder: Air-to-air anti-radiation missile based on the Sidewinder. Privately developed by Raytheon with their own funds, and demonstrated to be effective in actual live fire testing under simulated combat conditions, the US military nonetheless dismissed the concept, under the dubious assertion that Soviet aircraft didn't have radar. This attitude toward the RayWinder remained unchanged, even after Soviet fighters equipped with radar had become the norm.
MIM-72 Chaparral: Surface-to-air missile based on the AIM-9D. It is launched from a rotating 4-rail launcher, which may be mounted on either an M48 vehicle or an M54 trailer. A naval version of that launcher was developed as well, and is used by the Republic of China Navy.
Similar weapons
AIM-4 Falcon: The chief rival of the AIM-9 Sidewinder, the USAF's Falcon predated the former by several years. It was a larger and heavier missile with generally poorer performance than the Sidewinder, and it was largely superseded by that missile in USAF service (by the late 1960s, the only USAF fighters still using the Falcon were those that couldn't be made to use the Sidewinder, such as the F-106 Delta Dagger). The Falcon was quickly overrun and trampled on the short-range air-to-air missile market by the Sidewinder, though it nonetheless found a few enduring niches that kept it in service into the early 2000s.
R-5: The first operational Soviet air-to-air missile. It is also known as the K-5. Western reporting name for this missile is AA-1 or Alkali. It was a short-range weapon like the Sidewinder, but it was much larger and heavier, carried a warhead three times as heavy, had an even shorter range, and employed radio beam-riding (later semi-active radar) guidance. The R-55 variant replaced the seeker head with an infrared homing model in 1967, but by the time of this improvement, the R-5 series was badly outclassed by missiles like the British Red Top and the AIM-9D Sidewinder.
Firestreak: This British infrared guided air-to-air missile is similar in function to the Sidewinder, though it entered service several years earlier. A formidable weapon for its time, the Firestreak was almost twice as heavy as the AIM-9A, and carried a warhead four times as heavy.
Red Top: Another early British "heat-seeking" missile, the Red Top was developed to replace the Firestreak, but never completely did so. It is twice as heavy as the Sidewinder, with a warhead five times as massive.
PL-5: Produced in China, the PL-5 is extremely similar to the AIM-9G (an improved version of the AIM-9D).
R.550 Magic: A much newer French air-to-air missile introduced in 1975. The Magic is extremely similar in form and function to the Sidewinder, though its electronics and performance are more like that of 1970s variants. It is easily differentiated from the Sidewinder by its two tandem sets of forward fins.
AAM-1: Another missile very similar to the early Sidewinders, the AAM-1 was developed and produced in Japan. It was used only by the Japan Air Self-Defense Force, and only 330 were produced.
Shafrir-1: This Israeli air-to-air missile is very similar in form and function to the AIM-9B Sidewinder, but carries a heavier warhead on-par with the AIM-9C/D. It was introduced in 1963.
Shafrir-2: A later development of the Shafrir-1, this missile looks even more like the Sidewinder, and has improved performance over its predecessor.
AIM-9 Sidewinder
Short-Range Air-to-Air Missile
AIM-9 Sidewinder
Short-Range Air-to-Air Missile
AIM-9 Sidewinder
Short-Range Air-to-Air Missile
AIM-9 Sidewinder
Short-Range Air-to-Air Missile
AIM-9 Sidewinder
Short-Range Air-to-Air Missile
