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Asurface-to-air missile (SAM), also known as aground-to-air missile (GTAM) orsurface-to-air guided weapon (SAGW), is amissile designed to be launched from the ground or the sea to destroyaircraft or other missiles. It is one type ofanti-aircraft system; in modern armed forces, missiles have replaced most other forms of dedicated anti-aircraft weapons, withanti-aircraft guns pushed into specialized roles.[1]
World War II saw the initial development of SAMs, yet no system became operational. Further development in the 1940s and 1950s led to operational systems being introduced by most major forces during the second half of the 1950s. Smaller systems, suitable for close-range work, evolved through the 1960s and 1970s, to modern systems that are man-portable. Shipborne systems followed the evolution of land-based models, starting with long-range weapons and steadily evolving toward smaller designs to provide a layered defence. This evolution of design increasingly pushed gun-based systems into the shortest-range roles.
The AmericanNike Ajax was the first operational SAM system, and the Soviet Union'sS-75 Dvina was the most-produced SAM system. Widely used modern examples include thePatriot andS-300 wide-area systems,SM-6 andMBDA Aster Missile naval missiles, and short-range man-portable systems like theStinger and9K38 Igla.
The first known idea for a guided surface-to-air missile was in 1925, when abeam riding system was proposed whereby a rocket would follow a searchlight beam onto a target. A selenium cell was mounted on the tip of each of the rocket's four tail fins, with the cells facing backwards.[2] When one selenium cell was no longer in the light beam, it would be steered in the opposite direction back into the beam. The first historical mention of a concept and design of a surface-to-air missile in which a drawing was presented, was by inventor Gustav Rasmus in 1931, who proposed a design that would home in on the sound of an aircraft's engines.[3]
DuringWorld War II, efforts were started to develop surface-to-air missiles as it was generally considered thatflak was of little use againstbombers of ever-increasing performance. The lethal radius of a flak shell is fairly small, and the chance of delivering a "hit" is essentially a fixed percentage per round. In order to attack a target, guns fire continually while the aircraft are in range in order to launch as many shells as possible, increasing the chance that one of these will end up within the lethal range. Against theBoeing B-17, which operated just within the range of the numerous Germaneighty-eights, an average of 2,805 rounds had to be fired per bomber destroyed.[4]
Bombers flying at higher altitudes require larger guns and shells to reach them. This greatly increases the cost of the system, and (generally) slows the rate of fire. Faster aircraft fly out of range more quickly, reducing the number of rounds fired against them. Against late-war designs like theBoeing B-29 Superfortress or jet-powered designs like theArado Ar 234, flak would be essentially useless.[5] This potential was already obvious by 1942, whenWalther von Axthelm outlined the growing problems with flak defences that he predicted would soon be dealing with "aircraft speeds and flight altitudes [that] will gradually reach 1,000 km/h (620 mph) and between 10,000–15,000 m (33,000–49,000 ft)."[5][nb 1] This was seen generally; in November 1943 the Director of Gunnery Division of theRoyal Navy concluded that guns would be useless against jets, stating "No projectile of which control is lost when it leaves the ship can be of any use to us in this matter."
The first serious consideration of a SAM development project was a series of conversations that took place in Germany during 1941. In February, Friederich Halder proposed a "flak rocket" concept, which ledWalter Dornberger to askWernher von Braun to prepare a study on a guided missile able to reach between 15,000 and 18,000 m (49,000 and 59,000 ft) altitude. Von Braun became convinced a better solution was a crewed rocket interceptor, and said as much to the director of theT-Amt,Roluf Lucht, in July. The directors of theLuftwaffe flak arm were not interested in crewed aircraft, and the resulting disagreements between the teams delayed serious consideration of a SAM for two years.[6]
Von Axthelm published his concerns in 1942, and the subject saw serious consideration for the first time; initial development programs for liquid- andsolid-fuel rockets became part of the Flak Development Program of 1942.[7] By this point serious studies by thePeenemünde team had been prepared, and several rocket designs had been proposed, including 1940'sFeuerlilie, and 1941'sWasserfall andHenschel Hs 117Schmetterling. None of these projects saw any real development until 1943, when the first large-scale raids by the Alliedair forces started. As the urgency of the problem grew, new designs were added, includingEnzian andRheintochter, as well as the unguidedTaifun which was designed to be launched in waves.[8]
In general, these designs could be split into two groups. One set of designs would be boosted to altitude in front of the bombers and then flown towards them on a head-on approach at low speeds comparable to crewed aircraft. These designs included the Feuerlilie, Schmetterling and Enzian. The second group were high-speed missiles, typically supersonic, that flew directly towards their targets from below. These included Wasserfall and Rheintochter. Both types usedradio control for guidance, either by eye, or by comparing the returns of the missile and target on a single radar screen. Development of all these systems was carried out at the same time, and the war ended before any of them was ready for combat use. The infighting between various groups in the military also delayed development. Some extreme fighter designs, like theKomet andNatter, also overlapped with SAMs in their intended uses.
Albert Speer was especially supportive of missile development. In his opinion, had they been consistently developed from the start, the large scalebomber raids of 1944 would have been impossible.[9]
The British developed unguided antiaircraft rockets (operated under the nameZ Battery) close to the start ofWorld War II, but theair superiority usually held by the Allies meant that the demand for similar weapons was not as acute.
When several Allied ships were sunk in 1943 byHenschel Hs 293 andFritz Xglide bombs, Allied interest changed. These weapons were released from stand-off distances, with the bomber remaining outside the range of the ship'santiaircraft guns, and the missiles themselves were too small and fast to be attacked effectively.[10]
To combat this threat, theU.S. Navy launchedOperation Bumblebee to develop a ramjet-powered missile to destroy the launching aircraft at long range.[10] The initial performance goal was to target an intercept at a horizontal range of 10 miles (16 km) and 30,000 feet (9,100 m) altitude, with a 300 to 600 pounds (140 to 270 kg) warhead for a 30 to 60 percent kill probability.[11] This weapon did not emerge for 16 years, when it entered operation as theRIM-8 Talos.[12]
Heavy shipping losses tokamikaze attacks during theLiberation of the Philippines and theBattle of Okinawa provided additional incentive for guided missile development.[10][13] This led to the BritishFairey Stooge andBrakemine efforts,[14] and theU.S. Navy'sSAM-N-2 Lark.[15] TheLark ran into considerable difficulty and it never entered operational use. The end of the war led to the British efforts being used strictly for research and development throughout their lifetime.[13]
In the immediate post-war era, SAM developments were under way around the world, with several of these entering service in the early- and mid-1950s.
Coming to the same conclusions as the Germans regarding flak, theU.S. Army started itsProject Nike developments in 1944. Led byBell Labs, theNike Ajax was tested in production form in 1952, becoming the first operational SAM system when it was activated in March 1954.[16] Concerns about Ajax's ability to deal with formations of aircraft led to greatly updated version of the same basic design entering service in 1958 as theNike Hercules, the first nuclear-armed SAM.[16] TheU.S. Army Air Forces had also considered collision-course weapons (like the German radio-controlled concepts) and launched Project Thumper in 1946. This was merged with another project, Wizard, and emerged as theCIM-10 Bomarc in 1959. TheBomarc had a range of over 500 km, but it was quite expensive and somewhat unreliable.[17]Development ofOerlikon'sRSD 58[18] started in 1947, and was a closely held secret until 1955. Early versions of the missile were available for purchase as early as 1952,[19] but never entered operational service. The RSD 58 usedbeam riding guidance, which has limited performance against high-speed aircraft, as the missile is unable to "lead" the target to a collision point. Examples were purchased by several nations for testing and training purposes, but no operational sales were made.[20]
TheSoviet Union began development of a SAM system in earnest with the opening of theCold War.Joseph Stalin was worried thatMoscow would be subjected to American and Britishair raids, like those againstBerlin, and, in 1951, he demanded that a missile system to counter a 900 bomber raid be built as quickly as possible. This led to theS-25 Berkut system (NATO reporting name: SA-1 "Guild"), which was designed, developed and deployed in a rush program. Early units entered operational service on 7 May 1955, and the entire system ringing Moscow was completely activated by June 1956.[21] The system failed, however, to detect, track, and intercept the only overflight of the Soviet capital Moscow by a U-2 reconnaissance plane on July 5, 1956.[22][23] The S-25 was a static system, but efforts were also put into a smaller design that would be much more mobile. This emerged in 1957 as the famousS-75 Dvina (SA-2 "Guideline"), a portable system, with very high performance, that remained in operation into the 2000s.[24] The Soviet Union remained at the forefront of SAM development throughout its history; and Russia has followed suit.
The early British developments withStooge andBrakemine were successful, but further development was curtailed in the post-war era. These efforts picked up again with the opening of the Cold War, following the "Stage Plan" of improving UK air defences with new radars, fighters and missiles. Two competing designs were proposed for "Stage 1", based on common radar and control units, and these emerged as the RAF'sBristol Bloodhound in 1958,[25] and the Army'sEnglish Electric Thunderbird in 1959.[26] A third design followed the AmericanBumblebee efforts in terms of role and timeline, and entered service in 1961 as theSea Slug.[27]
The Vietnam War was the first modern war in which guided anti-aircraft missiles seriously challenged highly advanced supersonic jet aircraft. It would also be the first and only time that the latest and most modernair defense technologies of theSoviet Union and the most modern jetfighter planes andbombers of the United States confronted each other in combat (if one does not count the Yom Kippur War wherein IAF was challenged by Syrian SA-3s).[28]
TheUSAF responded to this threat with increasingly effective means. Early efforts to directly attack the missiles sites as part ofOperation Spring High andOperation Iron Hand were generally unsuccessful, but the introduction ofWild Weasel aircraft carryingShrike missiles and theStandard ARM missile changed the situation dramatically. Feint and counterfeint followed as each side introduced new tactics to try to gain the upper hand. By the time ofOperation Linebacker II in 1972, the Americans had gained critical information about the performance and operations of the S-75 (via Arab S-75 systems captured by Israel), and used these missions as a way to demonstrate the capability ofstrategic bombers to operate in a SAM saturated environment. Their first missions appeared to demonstrate the exact opposite, with the loss of three B-52s and several others damaged in a single mission.[29] Dramatic changes followed, and by the end of the series, missions were carried out with additional chaff, ECM, Iron Hand, and other changes that dramatically changed the score.[30] By the conclusion of the Linebacker II campaign, the shootdown rate of the S-75 against the B-52s was 7.52% (15 B-52s were shot down, 5 B-52s were heavily damaged for 266 missiles)[31]
During the war, The Soviet Union supplied 7,658 SAMs to North Vietnam, and their defense forces conducted about 5,800 launches, usually in multiples of three. By the war's end, the U.S. lost a total of 3,374 aircraft in combat operations. According to the North Vietnamese, 31% were shot down by S-75 missiles (1,046 aircraft, or 5.6 missiles per one kill); 60% were shot down by anti-aircraft guns; and 9% were shot down by MiG fighters. The S-75 missile system significantly improved the effectiveness of North Vietnamese anti-aircraft artillery, which used data from S-75 radar stations[32] However, the U.S. states only 205 of those aircraft were lost to North Vietnamese surface-to-air missiles.[33]
All of these early systems were "heavyweight" designs with limited mobility and requiring considerable set-up time. However, they were also increasingly effective. By the early 1960s, the deployment of SAMs had rendered high-speed high-altitude flight in combat practically suicidal.[nb 2] The way to avoid this was to fly lower, below the line-of-sight of missile's radar systems. This demanded very different aircraft, like theF-111,TSR-2, andPanavia Tornado.
Consequently, SAMs evolved rapidly in the 1960s. As their targets were now being forced to fly lower due to the presence of the larger missiles, engagements would necessarily be at short ranges, and occur quickly. Shorter ranges meant the missiles could be much smaller, which aided them in terms of mobility. By the mid-1960s, almost all modern armed forces had short-range missiles mounted on trucks or light armour that could move with the armed forces they protected. Examples include the2K12 Kub (SA-6) and9K33 Osa (SA-8),MIM-23 Hawk,Rapier,Roland andCrotale.
The introduction ofsea-skimming missiles in the late 1960s and 1970s led to additional mid- and short-range designs for defence against these targets. The UK'sSea Cat was an early example that was designed specifically to replace theBofors 40 mm gun on its mount, and became the first operational point-defense SAM.[34] The AmericanRIM-7 Sea Sparrow quickly proliferated into a wide variety of designs fielded by most navies. Many of these are adapted from earlier mobile designs, but the special needs of the naval role has resulted in the continued existence of many custom missiles.
As aircraft moved ever lower, and missile performance continued to improve, eventually it became possible to build an effective man-portable anti-aircraft missile. Known asMANPADS, the first example was a Royal Navy system known as theHolman Projector, used as a last-ditch weapon on smaller ships. The Germans also produced a similar short-range weapon known asFliegerfaust, but it entered operation only on a very limited scale. The performance gap between this weapon and jet fighters of the post-war era was so great that such designs would not be effective.
By the 1960s, technology had closed this gap to a degree, leading to the introduction of theFIM-43 Redeye,SA-7 Grail andBlowpipe. Rapid improvement in the 1980s led to second generation designs, like theFIM-92 Stinger,9K34 Strela-3 (SA-14),Igla-1 andStarstreak, with dramatically improved performance. By the 1990s to the 2010s, the Chinese had developed designs drawing influence from these, notably theFN-6 and theQW series.
Through the evolution of SAMs, improvements were also being made toanti-aircraft artillery, but the missiles pushed them into ever shorter-range roles. By the 1980s, the only remaining widespread use was point-defense of airfields and ships, especially againstcruise missiles. By the 1990s, even these roles were being encroached on by new MANPADS and similar short-range weapons, like theRIM-116 Rolling Airframe Missile.
Surface-to-air missiles are classified by theirguidance, mobility,altitude andrange.
Missiles able to fly longer distances are generally heavier, and therefore less mobile. This leads to three "natural" classes of SAM systems; heavy long-range systems that are fixed or semi-mobile, medium-range vehicle-mounted systems that can fire on the move, and short-rangeman-portable air-defense systems (MANPADS).
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Modern long-range weapons include theMIM-104 Patriot andS-300 systems, which have effective ranges on the order of 150 km (93 mi) and offer relatively good mobility and short unlimbering times. These compare with older systems with similar or less range, like theMIM-14 Nike Hercules orS-75 Dvina, which required fixed sites of considerable size. Much of this performance increase is due to improved rocket fuels and ever-smaller electronics in the guidance systems. Some very long-range systems remain, notably the RussianS-400, which has a range of 400 km (250 mi).[36]
Medium-range designs, like theRapier and2K12 Kub, are specifically designed to be highly mobile with very fast, or zero, setup times. Many of these designs were mounted on armoured vehicles, allowing them to keep pace with mobile operations in a conventional war. Once a major group unto itself, medium-range designs have seen less development since the 1990s, as the focus has changed to unconventional warfare.
Developments have also been made in onboard maneuverability. Israel'sDavid's Sling Stunner missile is designed to intercept the newest generation of tactical ballistic missiles at low altitude. The multi-stage interceptor consists of a solid-fuel, rocket motor booster, followed by an asymmetricalkill vehicle with advanced steering for super-maneuverability during the kill-stage. A three-pulse motor provides additional acceleration and maneuverability during the terminal phase.[35]
MANPAD systems first developed in the 1960s and proved themselves in battle during the 1970s. MANPADS normally have ranges on the order of 3 km (1.9 mi) and are effective againstattack helicopters and aircraft making ground attacks. Against fixed wing aircraft, they can be very effective, forcing them to fly outside the missile's envelope and thereby greatly reducing their effectiveness in ground-attack roles. MANPAD systems are sometimes used with vehicle mounts to improve maneuverability, like theAvenger system. These systems have encroached on the performance niche formerly filled by dedicated mid-range systems.
Ship-based anti-aircraft missiles are also considered to be SAMs, although in practice it is expected that they would be more widely used againstsea skimming missiles rather than aircraft[citation needed]. Virtually all surfacewarships can be armed with SAMs, and naval SAMs are a necessity for all front-line surface warships. Some warship types specialize in anti-air warfare e.g.Ticonderoga-class cruisers equipped with theAegis combat system orKirov-class cruisers with theS-300FFort missile system. Modern Warships may carry all three types (from long-range to short-range) of SAMs as a part of their multi-layered air defence.
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SAM systems generally fall into two broad groups based on their guidance systems, those usingradar and those using some other means.
Longer range missiles generally use radar for early detection and guidance. Early SAM systems generally used tracking radars and fed guidance information to the missile usingradio control concepts, referred to in the field ascommand guidance. Through the 1960s, thesemi-active radar homing (SARH) concept became much more common. In SARH, the reflections of the tracking radar's broadcasts are picked up by a receiver in the missile, which homes in on this signal. SARH has the advantage of leaving most of the equipment on the ground, while also eliminating the need for the ground station to communicate with the missile after launch.
Smaller missiles, especially MANPADS, generally useinfrared homing guidance systems. These have the advantage of being "fire-and-forget", once launched they will home on the target on their own with no external signals needed. In comparison, SARH systems require the tracking radar to illuminate the target, which may require them to be exposed through the attack. Systems combining an infrared seeker as aterminal guidance system on a missile using SARH are also known, like theMIM-46 Mauler, but these are generally rare.
Some newer short-range systems use a variation of the SARH technique, but based onlaser illumination instead of radar. These have the advantage of being small and very fast acting, as well as highly accurate. A few older designs use purely optical tracking and command guidance, perhaps the best known example of this is the BritishRapier system, which was initially an all-optical system with high accuracy.
All SAM systems from the smallest to the largest generally includeidentified as friend or foe (IFF) systems to help identify the target before being engaged. While IFF is not as important with MANPADs, as the target is almost always visually identified prior to launch, most modern MANPADs do include it.
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Long-range systems generally use radar systems for target detection, and depending on the generation of system, may "hand off" to a separate tracking radar for attack. Short range systems are more likely to be entirely visual for detection.
Hybrid systems are also common. TheMIM-72 Chaparral was fired optically, but normally operated with a short range early warning radar that displayed targets to the operator. This radar, theFAAR, was taken into the field with aGama Goat and set up behind the lines. Information was passed to theChaparral via adata link. Likewise, the UK's Rapier system included a simple radar that displayed the rough direction of a target on a series of lamps arranged in a circle. The missile operator would point his telescope in that rough direction and then hunt for the target visually.
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