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105-468: The Short Range Air-to-Air Missile ( Short-Range Anti-Air Missile in NATO AAP-15), or SRAAM for short, initially known as Taildog , was an experimental British infrared homing ("heat seeking") air-to-air missile , developed between 1968 and 1980 by Hawker Siddeley Dynamics . It was designed to be very manoeuvrable for use at short range in a dogfight situation. The SRAAM was unusual in that it

210-415: A forward looking infrared or similar cueing system. Heat-seekers are extremely effective: 90% of all United States air combat losses between 1984 and 2009 were caused by infrared-homing missiles. They are, however, subject to a number of simple countermeasures, most notably by dropping flares behind the target to provide false heat sources. That works only if the pilot is aware of the missile and deploys

315-784: A base for a future missile design. In 1980, the SRAAM work became the starting point for the ASRAAM . Surviving artefacts include a mockup of the missile in the Royal Air Force Museum Cosford , and a launcher at the Bristol Aero Collection. Infrared homing Infrared homing is a passive weapon guidance system which uses the infrared (IR) light emission from a target to track and follow it seamlessly. Missiles which use infrared seeking are often referred to as "heat-seekers" since infrared

420-625: A better weapon than the Falcon: B models managed a 14% kill ratio, while the much longer-ranged D models managed 19%. Its performance and lower cost led the Air Force to adopt it as well. The first heat-seeker built outside the US was the UK's de Havilland Firestreak . Development began as OR.1056 Red Hawk , but this was considered too advanced, and in 1951 an amended concept was released as OR.1117 and given

525-616: A high off-boresight lock-on capability capable of being targeted by a Helmet Mounted Sight (HMS), allowing it to be fired at targets which were not directly ahead, making it far easier to achieve a firing position. The solid-propellant rocket used thrust vectoring for control giving it superior turning capability over the Sidewinder. At the time the navy was developing VFX, the Air Force was developing its F-X concept , which emerged with an almost identical set of requirements as VFX. And as part of that project, they also concluded they needed

630-606: A large searchlight fitted with a filter to limit the output to the IR range. This provided enough light to see the target at short range, and Spanner Anlage was fitted to a small number of Messerschmitt Bf 110 and Dornier Do 17 night fighters . These proved largely useless in practice and the pilots complained that the target often only became visible at 200 metres (660 ft), at which point they would have seen it anyway. Only 15 were built and were removed as German airborne radar systems improved though 1942. AEG had been working with

735-471: A missile airframe and considerable effort remained before an actual weapon would be ready for use. Nevertheless, a summer 1944 report to the German Air Ministry stated that these devices were far better developed than competing systems based on radar or acoustic methods. Aware of the advantages of passive IR homing, the research program started with a number of theoretical studies considering

840-561: A missile work like the pilots wanted rather than the pilots working the way the missile wanted. They began designing a missile that would track successfully in every situation where the missile indicated lock-on. In order for this to happen, it would have to have a very wide FOV, or "off-boresight capability", so it would continue to see the target even if it was crossing rapidly. It would also have to have extremely high manoeuvrability so it could successfully track down an aircraft in these situations. The company began low-level development of such

945-522: A more conventional hemispherical dome. The first test firing took place in 1955 and it entered service with the Royal Air Force in August 1958. The French R.510 project began later than Firestreak and entered experimental service in 1957, but was quickly replaced by a radar-homing version, the R.511. Neither was very effective and had short range on the order of 3 km. Both were replaced by

1050-720: A much better missile, and began the AIM-82 to that requirement. Since both missiles were more or less identical in their role, it was decided to abandon the AIM-82 in favour of the Agile. The AIM-95A was developed to a point where flight tests were carried out including test firing at China Lake and inclusion in the ACEVAL/AIMVAL Joint Test & Evaluation conducted with both the F-14 and F-15 at Nellis AFB in 1975–78. As

1155-568: A much larger design. In 1970 the British Ministry of Defence came to the conclusion that a better short-range missile was needed, and drew up a request for proposals , AST 1218 . AST 1218 also included the requirement that the missile could be carried by aircraft that lacked the radar-aided target acquisition systems of the Phantom and Lightning . The Taildog became Hawker Siddeley's response to AST 1218, which became ASR 1222 when

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1260-581: A much smaller, shorter-range weapon was the correct solution, a "gun that fires around corners". This led to the Taildog concept, which became SRAAM , which was ultimately canceled in favor of Skyflash . The Soviet Union also began development of an advanced high off-boresight SRM with thrust vectoring and subsequently fielded the R-73 /AA-11 Archer on the MiG-29 in 1985. NATO learned about their performance due to

1365-619: A number of victories in the middle east and Vietnam. A major upgrade program for the Redeye started in 1967, as the Redeye II. Testing did not begin until 1975 and the first deliveries of the now renamed FIM-92 Stinger began in 1978. An improved rosette seeker was added to the B model in 1983, and several additional upgrades followed. Sent to the Soviet–Afghan War , they claimed a 79% success rate against Soviet helicopters, although this

1470-498: A position where the missile would be able to continue tracking even after launch. This problem also led to efforts to make new missiles that would hit their targets even if launched under these less-than-ideal positions. In the UK this led to the SRAAM project, which was ultimately the victim of continually changing requirements. Two US programmes, AIM-82 and AIM-95 Agile , met similar fates. New seeker designs began to appear during

1575-503: A practical detector. Nevertheless, it was used for some time by the US Navy as a secure communications system. In 1930 the introduction of the Ag–O–Cs ( silver – oxygen – cesium ) photomultiplier provided the first practical solution to the detection of IR, combining it with a layer of galena as the photocathode . Amplifying the signal emitted by the galena, the photomultiplier produced

1680-562: A result of escalating costs, the project was canceled in 1975. Instead, an improved version of the Sidewinder was developed for use by both the Air Force and Navy. Although this was intended to be an interim solution, in fact, the AIM-9 continues in service today. While the AIM-95 program was being carried out, the Royal Air Force had come to similar conclusions about the need for a new high-maneuverability missile. However, their studies suggested

1785-568: A supersonic version. At this stage the concept was for a defensive weapon fired rearward out of a long tube at the back end of bomber aircraft . In April 1949 the Firebird missile project was cancelled and MX-904 was redirected to be a forward-firing fighter weapon. The first test firings began in 1949, when it was given the designation AAM-A-2 (Air-to-air Missile, Air force, model 2) and the name Falcon. IR and semi-active radar homing (SARH) versions both entered service in 1956, and became known as

1890-471: A target at longer ranges. The new design would address both of these problems; a new seeker would allow lock-on from any angle including the front of the aircraft, greatly improved manoeuvrability would allow it to attack targets even at rapid crossing speeds, and a larger and more powerful motor would give it equal or greater range under all conditions. The resulting Agile design was equipped with an infrared seeker for fire and forget operation. The seeker had

1995-447: A transparent plate with a sequence of opaque segments painted on them that was placed in front of the IR detector. The plate spins at a fixed rate, which causes the image of the target to be periodically interrupted, or chopped . The Hamburg system developed during the war is the simplest system, and easiest to understand. Its chopper was painted black on one half with the other half left transparent. For this description we consider

2100-429: A useful output that could be used for detection of hot objects at long ranges. This sparked developments in a number of nations, notably the UK and Germany where it was seen as a potential solution to the problem of detecting night bombers . In the UK, research was plodding, with even the main research team at Cavendish Labs expressing their desire to work on other projects, especially after it became clear that radar

2205-581: A very desirable device. Kutzscher's team developed a system with the Eletroacustic Company of Kiel known as Hamburg , which was being readied for installation in the Blohm & Voss BV 143 glide bomb to produce an automated fire-and-forget anti-shipping missile. A more advanced version allowed the seeker to be directed off-axis by the bombardier in order to lock on to a target to the sides, without flying directly at it. However, this presented

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2310-587: A weapon as a private venture under the name "Taildog" in 1968. This goal was a short-range, low-cost missile that would fill the gap between guns and then-current missiles like the Firestreak and the Red Top . Hawker described it as 'a gun that fires around corners'. The initial design was 2.0 m long, had a diameter of 16.5 cm and weighed 50 kg. It was capable of engaging targets between 250 m and 2 km, as compared to perhaps 12 km under

2415-622: Is debated. The Soviets likewise improved their own versions, introducing the 9K34 Strela-3 in 1974, and the greatly improved dual-frequency 9K38 Igla in 1983, and Igla-S in 2004. The three main materials used in the infrared sensor are lead(II) sulfide (PbS), indium antimonide (InSb) and mercury cadmium telluride (HgCdTe). Older sensors tend to use PbS, newer sensors tend to use InSb or HgCdTe. All perform better when cooled, as they are both more sensitive and able to detect cooler objects. Early infrared seekers were most effective in detecting infrared radiation with shorter wavelengths, such as

2520-436: Is not required, instead, both signals can be extracted from a single photocell with the use of electrical delays or a second reference signal 90 degrees out of phase with the first. This system produces a signal that is sensitive to the angle around the clock face, the bearing , but not the angle between the target and the missile centerline, the angle off (or angle error ). This was not required for anti-ship missiles where

2625-456: Is radiated strongly by hot bodies. Many objects such as people, vehicle engines and aircraft generate and emit heat and so are especially visible in the infrared wavelengths of light compared to objects in the background. Infrared seekers are passive devices, which, unlike radar , provide no indication that they are tracking a target. That makes them suitable for sneak attacks during visual encounters or over longer ranges when they are used with

2730-437: Is set too small the image from the target is too small to create a useful signal, while setting it too large makes it inaccurate. For this reason, linear scanners have inherent accuracy limitations. Additionally, the dual reciprocating motion is complex and mechanically unreliable, and generally two separate detectors have to be used. Most early seekers used so-called spin-scan , chopper or reticle seekers. These consisted of

2835-557: The AIM-4 Falcon after 1962. The Falcon was a complex system offering limited performance, especially due to its lack of a proximity fuse, and managed only a 9% kill ratio in 54 firings during Operation Rolling Thunder in the Vietnam War . However, this relatively low success rate must be appreciated in the context of all these kills representing direct hits, something that was not true of every kill by other American AAMs. In

2940-566: The AIM-9M Sidewinder and Stinger use compressed gas like argon to cool their sensors in order to lock onto the target at longer ranges and all aspects. (Some such as the AIM-9J and early-model R-60 used a peltier thermoelectric cooler ). The detector in early seekers was barely directional, accepting light from a very wide field of view (FOV), perhaps 100 degrees across or more. A target located anywhere within that FOV produces

3045-469: The Hamburg , an AC signal was generated that matched the rotational frequency of the disk. However, in this case the signal does not turn on and off with angle, but is constantly being triggered very rapidly. This creates a series of pulses that are smoothed out to produce a second AC signal at the same frequency as the test signal, but whose phase is controlled by the actual position of the target relative to

3150-400: The Vietnam War , when early missiles like the AIM-4 Falcon and AIM-9 Sidewinder had success rates on the order of 9 and 14%, respectively. Much of this was due to the fact that pilots had been trained to approach using radar or ground-controlled interception , which placed the enemy aircraft somewhere in front of them, but not necessarily flying in the same direction. In these situations,

3255-426: The "Sun Tracker", was being developed as a possible guidance system for an intercontinental ballistic missile . Testing this system led to the 1948 Lake Mead Boeing B-29 crash . USAAF project MX-798 was awarded to Hughes Aircraft in 1946 for an infrared tracking missile. The design used a simple reticle seeker and an active system to control roll during flight. This was replaced the next year by MX-904, calling for

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3360-410: The 1960s. A new generation developed in the 1970s and the 1980s made great strides and significantly improved their lethality. The latest examples from the 1990s and on have the ability to attack targets out of their field of view (FOV) behind them and even to pick out vehicles on the ground. IR seekers are also the basis for many semi-automatic command to line of sight (SACLOS) weapons. In this use,

3465-421: The 1970s and led to a series of more advanced missiles. A major upgrade to the Sidewinder began, providing it with a seeker that was sensitive enough to track from any angle, giving the missile all aspect capability for the first time. This was combined with a new scanning pattern that helped reject confusing sources (like the sun reflecting off clouds) and improve the guidance towards the target. A small number of

3570-436: The 4.2 micrometre emissions of the carbon dioxide efflux of a jet engine . This made them useful primarily in tail-chase scenarios, where the exhaust was visible and the missile's approach was carrying it toward the aircraft as well. In combat these proved extremely ineffective as pilots attempted to make shots as soon as the seeker saw the target, launching at angles where the target's engines were quickly obscured or flew out of

3675-495: The Block III version was put into production. The Soviets started development of two almost identical weapons in 1964, Strela-1 and Strela-2. Development of these proceeded much more smoothly, as the 9K32 Strela-2 entered service in 1968 after fewer years of development than the Redeye. Originally a competing design, the 9K31 Strela-1 was instead greatly increased in size for vehicle applications and entered service at around

3780-537: The R-73 problem was initially going to be the ASRAAM , a pan-European design that combined the performance of the R-73 with an imaging seeker. In a wide-ranging agreement, the US agreed to adopt ASRAAM for their new short-range missile, while the Europeans would adopt AMRAAM as their medium-range weapon. However, ASRAAM soon ran into intractable delays as each of the member countries decided a different performance metric

3885-464: The ability to be fired at targets completely out of view of the seeker; after firing the missile would orient itself in the direction indicated by the launcher and then attempt to lock on. When combined with a helmet mounted sight , the missile could be cued and targeted without the launch aircraft first having to point itself at the target. This proved to offer significant advantages in combat, and caused great concern for Western forces. The solution to

3990-477: The aircraft and thus produce an ever-increasing signal while the aircraft is providing little or none. Additionally, as the missile approaches the target, smaller changes in relative angle are enough to move it out of this center null area and start causing control inputs again. With a bang-bang controller, such designs tend to begin to overreact during the last moments of the approach, causing large miss distances and demanding large warheads. A great improvement on

4095-410: The angle-off and feed that into the controls as well. This can be accomplished with the same disk and some work on the physical arrangement of the optics. Since the physical distance between the radial bars is larger at the outer position of the disk, the image of the target on the photocell is also larger, and thus has greater output. By arranging the optics so the signal is increasingly cut off closer to

4200-451: The basic spin-scan concept is the conical scanner or con-scan . In this arrangement, a fixed reticle is placed in front of the detector and both are positioned at the focus point of a small Cassegrain reflector telescope. The secondary mirror of the telescope is pointed slightly off-axis, and spins. This causes the image of the target to be spun around the reticle , instead of the reticle itself spinning. Consider an example system where

4305-517: The best case for the Red Top. The first photographs of mock-ups were shown in early 1970, and were displayed at a trade show in Hannover later that year. The Taildog was highly manoeuvrable through the use of thrust vectoring for all flight control. Vectoring was accomplished by rotating small vanes into the rocket exhaust. Six of these vanes were arranged as segments of a circle at the tail end of

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4410-409: The center of the disk, the resulting output signal varies in amplitude with the angle-off. However, it will also vary in amplitude as the missile approaches the target, so this is not a complete system by itself and some form of automatic gain control is often desired. Spin-scan systems can eliminate the signal from extended sources like sunlight reflecting from clouds or hot desert sand. To do this,

4515-478: The center of the operator's telescope. SACLOS systems of this sort have been used both for anti-tank missiles and surface-to-air missiles , as well as other roles. The infrared sensor package on the tip or head of a heat-seeking missile is known as the seeker head . The NATO brevity code for an air-to-air infrared-guided missile launch is Fox Two . The ability of certain substances to give off electrons when struck by infrared light had been discovered by

4620-401: The centerline it was. Other systems used a second scanning disk with radial slits to provide the same result but from a second output circuit. AEG developed a much more advanced system during the war, and this formed the basis of most post-war experiments. In this case, the disk was pattered with a series of opaque regions, often in a series of radial stripes forming a pizza-slice pattern. Like

4725-477: The code name Blue Jay . Designed as an anti-bomber weapon, the Blue Jay was larger, much heavier and flew faster than its US counterparts, but had about the same range. It had a more advanced seeker, using PbTe and cooled to −180 °C (−292.0 °F) by anhydrous ammonia to improve its performance. One distinguishing feature was its faceted nose cone, which was selected after it was found ice would build up on

4830-489: The contract was awarded. Hawker's proposal was received favourably, and in 1972 the Ministry of Defence awarded a development contract (Air Staff Requirement 1222). Two versions were studied, the advanced SRAAM-100 and a basic version called SRAAM-75. Both used the same airframe but different electronic fits. The SRAAM was slightly longer than the Taildog, with a length of 2.75 m (9 ft 0 in). The diameter remained

4935-401: The control system and commands the missile to turn up. A second cell placed at the 3 o'clock position completes the system. In this case, the switching takes place not at the 9 and 3 o'clock positions, but 12 and 6 o'clock. Considering the same target, in this case, the waveform has just reached its maximum positive point at 12 o'clock when it is switched negative. Following this process around

5040-410: The countermeasures on time. The sophistication of modern seekers has rendered these countermeasures increasingly ineffective. The first IR devices were experimented with during World War II . During the war, German engineers were working on heat-seeking missiles and proximity fuses but did not have time to complete development before the war ended. Truly practical designs did not become possible until

5145-401: The detector, or in the case of Madrid , two metal vanes were tilted to block off more or less of the signal. By comparing the time the flash was received to the location of the scanner at that time, the vertical and horizontal angle-off can be determined. However, these seekers also have the major disadvantage that their FOV is determined by the physical size of the slit (or opaque bar). If this

5250-410: The disk spinning clockwise as seen from the sensor; we will call the point in the rotation when the line between the dark and light halves is horizontal and the transparent side is on the top to be the 12 o'clock position. A photocell is positioned behind the disk at the 12 o'clock position. A target is located just above the missile. The sensor begins to see the target when the disk is at 9 o'clock, as

5355-401: The disk. By comparing the phase of the two signals, both the vertical and horizontal correction can be determined from a single signal. A great improvement was made as part of the Sidewinder program, feeding the output to the pilot's headset where it creates a sort of growling sound known as the missile tone that indicates that the target is visible to the seeker. In early systems this signal

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5460-438: The emissions from the targets. This led to the practical discovery that the vast majority of the IR output from a piston-engine aircraft was between 3 and 4.5 micrometers. The exhaust was also a strong emitter, but cooled rapidly in the air so that it did not present a false tracking target. Studies were also made on atmospheric attenuation, which demonstrated that air is generally more transparent to IR than visible light, although

5565-433: The entire seeker assembly is mounted on a gimbal system that allows it to track the target through wide angles, and the angle between the seeker and the missile aircraft is used to produce guidance corrections. This gives rise the concepts of instantaneous field of view (IFOV) which is the angle the detector sees, and the overall field of view, also known as the tacking angle or off-boresight capability , which includes

5670-499: The famous Indian polymath Jagadish Chandra Bose in 1901, who saw the effect in galena , known today as lead sulfide, PbS. There was little application at the time, and he allowed his 1904 patent to lapse. In 1917, Theodore Case , as part of his work on what became the Movietone sound system , discovered that a mix of thallium and sulfur was much more sensitive, but was highly unstable electrically and proved to be of little use as

5775-604: The first effective French design, the R.530 , in 1962. The Soviets introduced their first infrared homing missile, the Vympel K-13 in 1961, after reverse engineering a Sidewinder that stuck in the wing of a Chinese MiG-17 in 1958 during the Second Taiwan Strait Crisis . The K-13 was widely exported, and faced its cousin over Vietnam throughout the war. It proved even less reliable than the AIM-9B it

5880-402: The fixed signal is filtered out. A significant problem with the spin-scan system is that the signal when the target is near the center drops to zero. This is because even its small image covers several segments as they narrow at the center, producing a signal similar enough to an extended source that it is filtered out. This makes such seekers extremely sensitive to flares, which move away from

5985-581: The ground and from a Hawker Hunter F.6 (RAF serial XG210 ). The trials were successful, with one famous incident demonstrating the missile's manoeuvrability when it turned into the Hunter's flight path immediately after launch and almost collided with it. In the same year, the British MOD chose the AIM-9L Sidewinder as its next short-range missile, but the SRAAM project was kept alive to provide

6090-403: The high degree of sensitivity required to lock onto the lower-level signals coming from the front and sides of an aircraft. Background heat from inside the sensor, or the aerodynamically heated sensor window, can overpower the weak signal entering the sensor from the target. ( CCDs in cameras have similar problems; they have much more "noise" at higher temperatures.) Modern all-aspect missiles like

6195-416: The introduction of conical scanning and miniaturized vacuum tubes during the war. Anti-aircraft IR systems began in earnest in the late 1940s, but the electronics and the entire field of rocketry were so new that they required considerable development before the first examples entered service in the mid-1950s. The early examples had significant limitations and achieved very low success rates in combat during

6300-638: The late 1960s the Navy began development of the Grumman F-14 Tomcat fighter, which offered dramatically improved performance over their F-4 Phantoms . The Tomcat's origins begin in the Fleet Air Defense (FAD) concept that was based on aircraft carrying very long-range missiles and radars, allowing them to attack enemy aircraft at ranges on the order of 100 miles (160 km). While the FAD

6405-658: The launch aircraft would be both behind the target and flying in the same general direction. This would maximize the chance that the target would still be visible to the missile after it was launched. Unfortunately, such maneuvering was both time consuming and potentially difficult to arrange, and in combat there were many situations where a target would cross in front of the fighter in a "snap shot". To provide some capability in these situations, autocannons were hastily added to those fighters that lacked them. Considering this problem, designers at Hawker Siddeley Dynamics , Hawker's missile division, decided that it would be better to have

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6510-528: The launch aircraft would be both behind the target and flying in the same general direction. This would maximize the chance that the target would still be visible to the missile after it was launched. Unfortunately, such manoeuvring was both time consuming and potentially difficult to arrange, and in combat, there were many situations where a target would cross in front of the fighter in a "snap shot". To provide some capability in these situations, autocannons were hastily added to those fighters that lacked them. In

6615-413: The location of the target by timing when the image disappeared (AEG) or reappeared (Kepka). The Kepka Madrid system had an instantaneous field of view (IFOV) of about 1.8 degrees and scanned a full 20 degree pattern. Combined with the movement of the entire seeker within the missile, it could track at angles as great as 100 degrees. Rheinmetall-Borsig and another team at AEG produced different variations on

6720-462: The markings on the reticle. At this same instant, a spin-scan system would be producing a constant output in its center null. Flares will still be seen by the con-scan seeker and cause confusion, but they will no longer overwhelm the target signal as it does in the case of spin-scan when the flare leaves the null point. AIM-95 Agile Early infrared homing missiles had two limitations that made them difficult to use in combat situations. The first

6825-404: The missile body, where they were protected from the rocket exhaust. Each segment was pivoted at one end, allowing it to be rotated so the other end would be moved into the exhaust. The control system would activate the segment closest to the required change in direction. External aerodynamic surfaces were reduced to vestigial surfaces near the rear of the missile, and were unmovable. Hawker was not

6930-514: The missile to be carried by almost any aircraft with little modification. The missile could be fired automatically when a target came into view of the seeker, unlike, for example, the Firestreak , which needed to be fed targeting information by the aircraft's radar. The contract was cancelled in 1974 due to defence cuts in favour of work on the Skyflash , but retained as a technology demonstration program. In 1977, eight test missiles were fired from

7035-555: The missile's field of view. Such seekers, which are most sensitive to the 3 to 5 micrometre range, are now called single-color seekers. This led to new seekers sensitive to both the exhaust as well as the longer 8 to 13 micrometer wavelength range, which is less absorbed by the atmosphere and thus allows dimmer sources like the fuselage itself to be detected. Such designs are known as "all-aspect" missiles. Modern seekers combine several detectors and are called two-color systems. All-aspect seekers also tend to require cooling to give them

7140-471: The missile, maximizing its angular velocity relative to the seeker. These limitations were made clear during the Vietnam War , when early missiles like the AIM-4 Falcon and AIM-9 Sidewinder had success rates on the order of 9 and 14%, respectively. Much of this was due to the fact that pilots had been trained to approach using radar or ground-controlled interception , which placed the enemy aircraft somewhere in front of them, but not necessarily flying in

7245-460: The movement of the entire seeker assembly. Since the assembly cannot move instantly, a target moving rapidly across the missile's line of flight may be lost from the IFOV, which gives rise to the concept of a tracking rate , normally expressed in degrees per second. Some of the earliest German seekers used a linear-scan solution, where vertical and horizontal slits were moved back and forth in front of

7350-399: The negative voltage portion of its waveform, so the switch inverts this back to positive. When the disk reaches the 9 o'clock position the cell switches again, no longer inverting the signal, which is now entering its positive phase again. The resulting output from this cell is a series of half-sine waves, always positive. This signal is then smoothed out to produce a DC output, which is sent to

7455-474: The next year. Wally Schirra recalls visiting the lab and watching the seeker follow his cigarette. The missile was given the name Sidewinder after a local snake; the name had a second significance as the sidewinder is a pit viper and hunts by heat, and moves in an undulating pattern not unlike the missile. The Sidewinder entered service in 1957, and was widely used during the Vietnam war. It proved to be

7560-571: The only one to come up with this basic concept; around the same time, the US Navy and the Air Force both began similar programs for similar reasons, ultimately combining their efforts in the AIM-95 Agile project. The Taildog and the Agile differed primarily in range; the Taildog was intended as a short-range dogfighting weapon, while the Agile was a replacement for the Sidewinder and set range requirements at least as good as that missile, producing

7665-472: The period the target is visible to the sensor, the AC waveform is in the positive voltage period, varying from zero to its maximum and back to zero. When the target disappears, the sensor triggers a switch that inverts the output of the AC signal. For instance, when the disk reaches the 3 o'clock position and the target disappears, the switch is triggered. This is the same instant that the original AC waveform begins

7770-487: The presence of water vapour and carbon dioxide produced several sharp drops in transitivity. Finally, they also considered the issue of background sources of IR, including reflections off clouds and similar effects, concluding this was an issue due to the way it changed very strongly across the sky. This research suggested that an IR seeker could home on a three-engine bomber at 5 kilometres (3.1 mi) with an accuracy of about 1 ⁄ 10 degree, making an IR seeker

7875-428: The problem that when the bomb was first released it was traveling too slowly for the aerodynamic surfaces to easily control it, and the target sometimes slipped out from the view of the seeker. A stabilized platform was being developed to address this problem. The company also developed a working IR proximity fuse by placing additional detectors pointing radially outward from the missile centerline. which triggered when

7980-523: The resulting L models were rushed to the UK just prior to their engagement in the Falklands War , where they achieved an 82% kill ratio, and the misses were generally due to the target aircraft flying out of range. The Argentine aircraft, equipped with Sidewinder B and R.550 Magic , could only fire from the rear aspect, which the British pilots simply avoided by always flying directly at them. The L

8085-421: The reticle is modified by making one half of the plate be covered not with stripes but a 50% transmission color. The output from such a system is a sine wave for half of the rotation and a constant signal for the other half. The fixed output varies with the overall illumination of the sky. An extended target that spans several segments, like a cloud, will cause a fixed signal as well, and any signal that approximates

8190-410: The rotation causes a series of chopped-off positive and negative sine waves. When this is passed through the same smoothing system, the output is zero. This means the missile does not have to correct left or right. If the target were to move to the right, for instance, the signal would be increasingly positive from the smoother, indicating increasing corrections to the right. In practice a second photocell

8295-496: The same direction. In these situations, the seeker might see the target's engine and send the growling signal that indicated lock-on , but would fail to track when fired because the target would move out of the FOV in the time while the missile was flying off the mounting rail. Faced with these dismal results, the US Navy and then US Air Force introduced new training syllabuses that placed much more emphasis on pre-shot maneuvering, so

8400-547: The same output signal. Since the goal of the seeker is to bring the target within the lethal radius of its warhead, the detector must be equipped with some system to narrow the FOV to a smaller angle. This is normally accomplished by placing the detector at the focal point of a telescope of some sort. This leads to a problem of conflicting performance requirements. As the FOV is reduced, the seeker becomes more accurate, and this also helps eliminate background sources which helps improve tracking. However, limiting it too much allows

8505-560: The same systems for use on tanks , and deployed a number of models through the war, with limited production of the FG 1250 beginning in 1943. This work culminated in the Zielgerät 1229 Vampir riflescope which was used with the StG 44 assault rifle for night use. The devices mentioned previously were all detectors, not seekers. They either produce a signal indicating the general direction of

8610-541: The same technologies have appeared in the Chinese PL-10 and Israeli Python-5 . Based on the same general principles as the original Sidewinder, in 1955 Convair began studies on a small man-portable missile ( MANPADS ) that would emerge as the FIM-43 Redeye . Entering testing in 1961, the preliminary design proved to have poor performance, and a number of major upgrades followed. It was not until 1968 that

8715-466: The same time. The UK began development of its Blowpipe in 1975, but placed the seeker on the launcher instead of the missile itself. The seeker sensed both the target and the missile and sent corrections to the missile via a radio link. These early weapons proved ineffective, with the Blowpipe failing in almost every combat use, while the Redeye fared somewhat better. The Strela-2 did better and claimed

8820-630: The same year as MX-798, 1946, William B. McLean began studies of a similar concept at the Naval Ordnance Test Station, today known as Naval Air Weapons Station China Lake . He spent three years simply considering various designs, which led to a considerably less complicated design than the Falcon. When his team had a design they believed would be workable, they began trying to fit it to the newly introduced Zuni 5-inch rocket . They presented it in 1951 and it became an official project

8925-489: The same. The thrust director system was replaced with a moving dome deflector, which consists of a cone-shaped deflector placed in the exhaust which is moved to the sides to cause the thrust to change. The fins were moved to the rear and were reshaped. The SRAAM was designed to be carried in a launch tube to protect the missile. The fins on the missile were hinged and designed to extend following launch. The launcher comprised two tubes and an optional radar cueing system, enabling

9030-403: The seeker is mounted on a trainable platform on the launcher and the operator keeps it pointed in the general direction of the target manually, often using a small telescope. The seeker does not track the target, but the missile, often aided by flares to provide a clean signal. The same guidance signals are generated and sent to the missile via thin wires or radio signals, guiding the missile into

9135-406: The seeker might see the target's engine and send the growling signal that indicated lock-on , but would fail to track when fired because the target would move out of the FOV in the time while the missile was flying off the mounting rail. Faced with these dismal results, the US Navy and then US Air Force introduced new training syllabuses that placed much more emphasis on pre-shot manoeuvring, so

9240-410: The seeker's mirror is tilted at 5 degrees, and the missile is tracking a target that is currently centered in front of the missile. As the mirror spins, it causes the image of the target to be reflected in the opposite direction, so in this case the image is moving in a circle 5 degrees away from the reticle's centerline. That means that even a centered target is creating a varying signal as it passes over

9345-405: The signal strength began to decrease, which it did when the missile passed the target. There was work on using a single sensor for both tasks instead of two separate ones. Other companies also picked up on the work by Eletroacustic and designed their own scanning methods. AEG and Kepka of Vienna used systems with two movable plates that continually scanned horizontally or vertically, and determined

9450-591: The spinning-disk system. In the post-war era, as the German developments became better known, a variety of research projects began to develop seekers based on the PbS sensor. These were combined with techniques developed during the war to improve accuracy of otherwise inherently inaccurate radar systems, especially the conical scanning system. One such system developed by the US Army Air Force (USAAF), known as

9555-407: The target is moving very slowly relative to the missile and the missile quickly aligns itself to the target. It was not appropriate for air-to-air use where the velocities were greater and smoother control motion was desired. In this case, the system was changed only slightly so the modulating disk was patterned in a cardioid which blanked out the signal for more or less time depending on how far from

9660-483: The target to move out of the FOV and be lost to the seeker. To be effective for guidance to the lethal radius, tracking angles of perhaps one degree are ideal, but to be able to continually track the target safely, FOVs on the order of 10 degrees or more are desired. This situation leads to the use of a number of designs that use a relatively wide FOV to allow easy tracking, and then process the received signal in some way to gain additional accuracy for guidance. Generally,

9765-470: The target, or in the case of later devices, an image. Guidance was entirely manual by an operator looking at the image. There were a number of efforts in Germany during the war to produce a true automatic seeker system, both for anti-aircraft use as well as against ships. These devices were still in development when the war ended; although some were ready for use, there had been no work on integrating them with

9870-414: The transparent portion of the chopper is aligned vertically at the target at 12 o'clock becomes visible. The sensor continues to see the target until the chopper reaches 3 o'clock. A signal generator produces an AC waveform that had the same frequency as the rotational rate of the disk. It is timed so the waveform reaches its maximum possible positive voltage point at the 12 o'clock position. Thus, during

9975-497: Was also clear. Given the dismal results with their current short-range missile, the Sidewinder, the China Lake Naval Weapons Center began development of a dramatically improved missile to replace it. Studies had demonstrated two primary sources of misses; one was taking shots when the missile could not successfully track the target, and the other was when the missile ran out of fuel trying to chase down

10080-432: Was based on, with the guidance system and fuse suffering continual failure. As Vietnam revealed the terrible performance of existing missile designs, a number of efforts began to address them. In the US, minor upgrades to the Sidewinder were carried out as soon as possible, but more broadly pilots were taught proper engagement techniques so they would not fire as soon as they heard the missile tone, and would instead move to

10185-533: Was being developed, experience over Vietnam was clearly demonstrating that the idea of all-long-range combat was simply not possible given tactical limitations. The need for improved manoeuvrability over the lumbering FAD design was clear, and this developed into the VFX proposal that in turn produced the Tomcat. The need for a better short-range missile to equip it for times when the aircraft was forced to close on its target

10290-412: Was fed directly to the control surfaces, causing rapid flicking motions to bring the missile back into alignment, a control system known as "bang-bang". Bang-bang controls are extremely inefficient aerodynamically, especially as the target approaches the centerline and the controls continually flick back and forth with no real effect. This leads to the desire to either smooth out these outputs, or to measure

10395-595: Was going to be a better solution. Nevertheless, Frederick Lindemann , Winston Churchill 's favorite on the Tizard Committee , remained committed to IR and became increasingly obstructionist to the work of the Committee who were otherwise pressing for radar development. Eventually they dissolved the Committee and reformed, leaving Lindemann off the roster, and filling his position with well known radio expert Edward Victor Appleton . In Germany, radar research

10500-607: Was launched from a launch tube instead of being attached to a launch rail, allowing two to be carried on a single mounting point. Although initially intended to replace the AIM-9 Sidewinder , it was downgraded to a technology demonstrator program in 1974. Between 1974 and 1977, several SRAAM missiles were launched in tests. In 1980, the knowledge gained from the SRAAM project was used in the ASRAAM missile project. Early infrared homing missiles had two limitations that made them difficult to use in combat situations. The first

10605-460: Was more important. The US eventually bowed out of the program, and instead adapted the new seekers developed for ASRAAM on yet another version of the Sidewinder, the AIM-9X. This so extends its lifetime that it will have been in service for almost a century when the current aircraft leave service. ASRAAM did, eventually, deliver a missile that has been adopted by a number of European forces and many of

10710-531: Was not given nearly the same level of support as in the UK, and competed with IR development throughout the 1930s. IR research was led primarily by Edgar Kutzscher at the University of Berlin working in concert with AEG . By 1940 they had successfully developed one solution; the Spanner Anlage (roughly "Peeping Tom system") consisting of a detector photomultiplier placed in front of the pilot, and

10815-578: Was so effective that aircraft hurried to add flare countermeasures, which led to another minor upgrade to the M model to better reject flares. The L and M models would go on to be the backbone of Western air forces through the end of the Cold War era. An even larger step was taken by the Soviets with their R-73 , which replaced the K-13 and others with a dramatically improved design. This missile introduced

10920-400: Was that the seeker was relatively insensitive and required large, hot sources to reliably track a target. In practice, this meant the engine of the enemy aircraft had to remain visible to the missile through the shot. The other was that the seeker had a limited field of view (FOV), meaning it could only see the target if it was in front of the missile. These limitations were made clear during

11025-438: Was that the seeker was relatively insensitive and required large, hot sources to reliably track a target. In practice, this meant the engine of the enemy aircraft had to remain visible to the missile through the shot. The other was that the seeker had a limited field of view (FOV), meaning it could only see the target if it was in front of the missile. This meant it was possible for the target to escape by flying at right angles to

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