An air-to-air missile (AAM) is a guided missile fired from an aircraft for the purpose of destroying another aircraft. It is typically powered by one or more rocket motors, usually solid fuelled but sometimes liquid fuelled. Ramjet engines, as used on the MBDA Meteor (currently in development), are emerging as propulsion that will enable future medium-range missiles to maintain higher average speed across their engagement envelope.
Air-to-air missiles are broadly grouped into short-range missiles - also called "dogfight" or "within visual range" (WVR) and medium- or long-range missiles - beyond visual range (BVR). Short-range missiles tend to use infrared guidance, while medium- and long-range missiles rely upon some type of radar guidance (and sometimes inertial guidance).
Post-war research led the Royal Air Force to introduce Fairey Fireflash into service in 1955 but their results were unsuccessful. The US Navy and US Air Force began equipping guided missiles in the 1956, deploying the USAF's AIM-4 Falcon and the USN's AIM-7 Sparrow and AIM-9 Sidewinder. The Soviet Air Force introduced its Kaliningrad K-5 into service in 1957. As missile systems have continued to advance, modern air warfare consists almost entirely of missile firing. The faith in Beyond Visual Range combat became so pervasive in the US that early F-4 variants were armed only with missiles in the 1960s. High casualty rates during the Vietnam War caused the US to reintroduce autocannons and traditional dogfighting tactics but the missile remains the primary weapon in air combat. In the Falklands War technically inferior British Harriers were able to defeat faster Argentinian opponents using AIM-9G missiles provided by the United States as the conflict began. The latest heat-seeking designs can lock onto a target from various angles, not just from behind, where the heat signature from the engines is strongest. Other types rely on radar guidance (either on-board or "painted" by the launching aircraft).
Guided missiles operate by detecting their target (usually by either radar or infrared methods, although rarely others such as laser guidance or optical tracking), and then "homing" in on the target on a collision course.
The target is usually destroyed or damaged by means of an explosive warhead, often throwing out fragments to increase the lethal radius, typically detonated by a proximity fuze (or impact fuze if it scores a direct hit).
Note that although the missile may use radar or infra-red guidance to home on the target, this does not necessarily mean that the same means is used by the launching aircraft to detect and track the target before launch. Infra-red guided missiles can be "slaved" to an attack radar in order to find the target and radar-guided missiles can be launched at targets detected visually or via an infra-red search and track (IRST) system, although they may require the attack radar to illuminate the target during part or all of the missile interception itself.
Infrared guided (IR) missiles home on the heat produced by an aircraft. Early infra-red detectors had poor sensitivity, so could only track the hot exhaust pipes of an aircraft. This meant an attacking aircraft had to maneuver to a position behind its target before it could fire an infra-red guided missile. This also limited the range of the missile as the infra-red signature soon become too small to detect with increasing distance and after launch the missile was playing "catch-up" with its target.
More modern infra-red guided missiles can detect the heat of an aircraft's skin, warmed by the friction of airflow, in addition to the fainter heat signature of the engine when the aircraft is seen from the side or head-on. This, combined with greater maneuverability, gives them an "all-aspect" capability, and an attacking aircraft no longer had to be behind its target to fire. Although launching from behind the target increases the probability of a hit, the launching aircraft usually has to be closer to the target in a tail-chase engagement.
An aircraft can defend against infra-red missiles by dropping flares that are hotter than the aircraft, so the missile homes in on the brighter, hotter target. Towed decoys and infra-red jammers can also be used. Some large aircraft and many combat helicopters make use of so called "hot brick" infra-red jammers, typically mounted near the engines. Current research is developing laser devices which can spoof or destroy the guidance systems of infra-redguided missiles.
However, the latest missiles such as the ASRAAM use an "imaging" infra-red seeker which "sees" the target (much like a digital video camera), and can distinguish between an aircraft and a point heat source such as a flare. They also feature a very wide detection angle, so the attacking aircraft does not have to be pointing straight at the target for the missile to lock on. The pilot can use a helmet mounted sight (HMS) and target another aircraft by looking at it, and then firing. This is called "off-boresight" launch. For example, the Russian Su-27 is equipped with an infra-red search and track (IRST) system with laser rangefinder for its HMS-aimed missiles.
In order to maneuver sufficiently from a poor launch angle at short ranges to hit its target, missiles are now employing gas-dynamic flight control methods such as vectored thrust, which allow the missile to start turning "off the rail", before its motor has accelerated it up to high enough speeds for its small aerodynamic surfaces to be useful.
A recent advancement in missile guidance is electro-optical imaging. The Israeli Python-5 has an electro-optical seeker that scans designated area for targets via optical imaging. Once a target is acquired, the missile will lock-on to it for the kill. Electro-optical seekers can be programmed to target vital area of an aircraft, such as the cockpit. Since it doesn't depend on the target aircraft's heat signature, it can be used against low-heat targets such as UAV's and cruise missiles.
Air-to-air missiles are typically long, thin cylinders in order to reduce their cross section and thus minimize drag at the high speeds at which they travel.
At the front is the seeker, either a radar system, radar homer, or infra-red detector. Behind that lies the avionics which control the missile. Typically after that, in the centre of the missile, is the warhead, usually several kilogrammes of high explosive surrounded by metal that fragments on detonation (or in some cases, pre-fragmented metal).
The rear part of the missile contains the propulsion system, usually a rocket of some type. Dual-thrust solid-fuel rockets are common, but some longer-range missiles use liquid-fuel motors that can "throttle" to extend their range and preserve fuel for energy-intensive final maneuvering. Some solid-fuelled missiles mimic this technique with a second rocket motor which burns during the terminal homing phase. There are missiles in development, such as the MBDA Meteor, that "breathe" air (using a ramjet, similar to a jet engine) in order to extend their range.
Modern missiles use "low-smoke" motors - early missiles produced thick smoke trails, which were easily seen by the crew of the target aircraft alerting them to the attack and helping them determine how to evade it.
Missiles are often cited with their maximum engagement range, which is very misleading. A missile's effective range is dependent on factors such as altitude, speed, position, and direction of target aircraft. For example the Vympel R-77 has stated range of 100 km. That's only true for a head-on, non-evading target at high altitude. At low altitude, the effective range is reduced by as much as 75%-80% to 20-25 km. If the target is taking evasive action, or in stern-chase position, the effective range is further reduced. See Air-to-Air missile non-comparison table for more information. The effective range of an air-to-air missile is known as the 'no-escape zone', noting the range at which the target can not evade the missile once launched.
Poorly-trained pilots, are known to fire their missiles at maximum-range engagement with poor results. In the 1998-2000 Eritrean-Ethiopian War, fighters from both sides shot over a dozen medium-range R-27 (AA-10 Alamo) missiles at distance with little effect. But when better-trained Ethiopian Su-27 pilots gave chase and attacked with short-range R-73 (AA-11 Archer) missiles, the results were often deadly to the Eritrean aircraft.
To take advantage of the increased field-of-view that now exceeded the capabilities of most aircraft radars also meant that helmet mounted sights gained popularity. Many newer missiles include what is known as "look-down-shoot-down" capability, as they could be fired onto low flying planes that would formerly be lost in ground clutter.
Examples of fifth generation missiles include:
For each missile, short notes are given, including an indication of its range and guidance mechanism.