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Guidance
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. Radar guidanceRadar guidance is normally used for medium or long range missiles, where the infra-red signature of the target would be too faint for an infra-red detector to track. There are two major types of radar-guided missile - active and semi-active.
Active radar homingActive radar (AR)-guided missiles carry their own radar system to detect and track their target. However, the size of the radar antenna is limited by the small diameter of missiles, limiting its range which typically means such missiles have to use another method to get close to the target before turning their radar set on, often relying on inertial guidance systems. Semi-active radar homingSemi-active radar (SAR)-guided missiles are simpler and more common. They function by detecting the radar energy reflected from the target, the radar energy is emitted from the launch aircraft's own radar signal. However, this means the launch aircraft has to maintain a "lock" on the target (keep illuminating the target aircraft with its' own radar) until the missile makes the interception, limiting the attacking aircraft's ability to maneuver, which may be necessary should threats to the attacking aircraft appear. It also makes jamming the missile lock easier because the launching aircraft is further from the target than the missile, so the radar signal has to travel further and is greatly attenuated over the distance. Beam ridingAn early form of radar guidance was "beam-riding" (BR). In this method the attacking aircraft directed a narrow beam of radar energy at the target. The air-to-air missile was launched into the beam where sensors on the aft of the missile controlled the missile, keeping it within the beam. So long as the beam was kept on the target aircraft, the missile would ride the beam until making the interception. While simple in concept, the difficulty of simultaneously keeping the beam solidly on the target (which couldn't be relied upon to cooperate by flying straight and level), continuing to fly one's own aircraft, all the while keeping an eye out for enemy countermeasures, can be readily appreciated. Although radar beam-riding air-to-air missiles are obsolete, the technology has since evolved toward laser-beam guided air-to-ground munitions, such as laser-guided bombs (LGB). These precision-strike munitions are sometimes called "smart weapons" by the press. Infrared guidanceInfrared 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. The Russian Su-27 is equipped with an infrared search and track (IRST) system with laser rangefinder for its HMS-guided 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. Electro-opticalA 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. DesignAir-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. Missile rangeMissiles 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 and mercenary pilots more interested in collecting their pay and going home alive than dead, 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. [1] PerformanceA number of terms frequently crop up in discussions of air to air missile performance.
DogfightShort-range air-to-air missiles used in "dogfighting" are usually classified into five "generations" according to the historical technological advances. Most of these advances were in infrared seeker technology (later combined with digital signal processing). First generationEarly short-range missiles such as the early Sidewinders and Vympel K-13 (AA-2 Atol) had infrared seekers with a narrow (30 degree) field of views and required the attacker to position them self behind the target (rear aspect engagement). This meant the target aircraft only had to perform a slight turn to move outside the missile seeker field of view and cause the missile to lose track of the target ("break lock").[1] Second generationSecond generation missiles utilized better seekers that improved the field of view to 45 degrees. Third generationThis generation introduced "all aspect" missiles, because more sensitive seekers allowed the attacker to fire at a target which was side-on to itself, i.e. from all aspects not just the rear. This meant that while the field-of-view was still restricted to a fairly narrow cone, the attack at least did not have to be behind the target.[1] Fourth generationThe Vympel R-73 (AA-11 Archer) entered service in 1985 and marked a new generation of dogfight missile. These missiles employed more advanced seeker technologies such focal plane arrays that improved resistance to infrared countermeasures (IRCM) such as flares and increased off-bore sight capability to in excess of 60 degrees, i.e. a 120 degree field of view. 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.[2] Popularly know as "look-down-shoot-down", because the pilot would turn their head towards the target and the missile use this directional information in inertial guidance until the target was in the infrared seekers' field of view. The Israeli Python 4 was one example of a missile integrated with such a system. These missiles are also much more agile, some by employing thrust vectoring (typically gimballed thrust). Fifth generationThe latest generation of short-range missiles again defined by advances in seeker technologies, this time electro-optical imaging infrared (IIR) seekers that allow the missiles to "see" images rather than single "points" of infrared radiation (heat). The sensors combined with more powerful digital signal processing provide the following benefits:[2]
Examples of fifth generation missiles include:
List of missiles by countryFor each missile, short notes are given, including an indication of its range and guidance mechanism. Brazil
France
Germany
European
India
Iraq
Israel
Italy
Japan
Pakistan
People's Republic of China
Russia/Soviet
South AfricaUnited Kingdom
United States
References
See also
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