S-75 Dvina

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V-750 missile on camouflaged launcher. Photo by Nellis AFB.

The Lavochkin OKB S-75 (Russian С-75, NATO reporting name SA-2 Guideline) is a high-altitude surface-to-air guided missile (SAM) system of the Soviet Union and is the most widely deployed and used air defense missile in history.

They gained notoriety when they shot down a USAF U-2 spy plane in 1960, and during the Vietnam War when they were briefly the cause of much consternation among US air-war planners. It has also been locally-produced in the People's Republic of China as the HQ-1 and HQ-2.

1 History
2 Description
3 Models
4 Related content
5 Links

[edit] History

V-750 missile in elevated position. Photo by GulfLINK.

Development of the S-75 started in 1953 at the Lavochkin OKB, under the direction of Petr Grushin. It was designed to attack non-maneuvering high-altitude targets, namely US SAC B-52 bombers. Testing was underway by the middle of the decade. One night-time test was witnessed by a US Congressman traveling in the Soviet Union, who interpreted it as a flying saucer, thereby setting off a wave of panic in the US. The missile was first shown publicly in the 1957 May Day parade in Moscow.

Wide scale deployment started in 1957, with various upgrades following over the next few years. Although they were not used to replace the SA-1 Guild defenses around Moscow, they did replace all other air defense systems, notably the remaining high-altitude anti-aircraft guns, the 130 mm KS-30 and 100 mm KS-19. Between mid-1958 and 1964 more than 600 SA-2 sites in the USSR were located via aerial reconnaissance by US intelligence in the USSR, mostly in defense of population centers, industrial complexes, and government control centers. A ring of sites was also located around the approaches to the Soviet heartland, and by the mid-1960s when deployment ended it is estimated that over 1,000 sites were operational.

Several sites were set up in East Germany to protect Soviet forces stationed there in the early 1960s. Later the system was sold to most countries in the Warsaw Pact, with the heaviest deployment remaining in East Germany.

The first aircraft to be shot down by the SA-2 was a Taiwanese RB-57 high-altitude reconnaissance aircraft, hit near Beijing on October 7, 1959. Over the next few years the Taiwanese ROCAF would lose a number of aircraft to the SA-2, both RB-57's and various drones. On May 1, 1960, Gary Powers' U-2 was shot down while flying over the testing site near Sverdlovsk, although it took 14 missiles to hit his high-flying plane and a Soviet MiG-19 was also destroyed in the action by mistake. That action led to the U-2 Crisis of 1960. It is also believed that Chinese SA-2s downed some ROCAF-piloted U-2s based on Taiwan.

North Vietnamese S-75 site. Note the typical hexagonal pattern that made the sites easy to spot from the air; the Vietnamese later abandoned the layout for this reason.

In 1965 North Vietnam asked for some assistance against the U.S.'s airpower, to which they were essentially defenseless at the time. After some discussion it was agreed to supply the NVA with the S-75, although the decision was not taken lightly as it greatly increased the chances that one would fall into US hands for study. Site preparation started early in the year, and the US detected the program almost immediately on April 5, 1965. While military planners pressed for the sites to be attacked before they could become operational, their political leaders refused, fearing that Soviet technical staff might be killed.

Then on July 23, 1965, a US Navy F-4C aircraft was shot down. The US responded with Operation Iron Hand three days later to attack the other sites before they could become operational. Most of the SA-2s were deployed around the Hanoi-Haiphong area and were off limits to attack (as were local airfields) for political reasons. Then, President Lyndon Johnson announced on public TV that one of the other sites would be attacked the next week. The Vietnamese removed the missiles and replaced them with decoys, while moving every available anti-aircraft gun into the approach routes. The tactic worked, causing some American casualties indirectly.

Over the next year the US delivered a number of solutions to the SA-2 problem. The Navy had the Shrike missile in service by mid-August, and mounted their first offensive strike on a site in October. The Air Force responded by fitting B-66 bombers with powerful jammers that blinded the early warning radars, and developed smaller jamming pods for fighters which denied range information to the radars. Later developments included the Wild Weasel aircraft fitted with jammer pods and ECM systems, dedicated to jamming and then shooting the sites with Shrikes of their own.

The Soviets and Vietnamese, however, were able to adapt to some of these tactics. The USSR upgraded the radar several times to improve ECM resistance. They also introduced a passive guidance mode, whereby the missile could lock on the jammer itself. This had an added advantage, since the radar could be kept off thus preventing Shrikes from being fired. Moreover, some new tactics were developed to combat the Shrike. One of them was to point the radar to the side and then turn it off briefly. Since the Shrike was a relatively primitive anti-radiation missile, it would follow the beam away from the radar and then simply crash when it lost the signal (after the radar was turned off). Another was a "false launch", when the tracking radar was turned on but the missiles were not actually fired. This allowed the missile crew to see if the target was equipped with a Shrike. If the aircraft fired one, it could be neutralized with the above techique without sacrificing any missiles.

Despite these advances, the US was able to come up with effective ECM packages for the B-52E models. These planes were able to fly raids against Hanoi with relatively few losses (though still significant enough to cause some concern, see linebacker 2).

PVO Strany started to replace the SA-2 with the much more effective SA-10 and SA-12 systems in the 1980s. Today only a few hundred, if any, of the 4,600 missiles are still in Russian service, even though they underwent a modernization program as late as 1993.

The SA-2 remains in widespread service throughout the world, with some level of operational ability in 35 countries. Vietnam and Egypt are tied for the largest deployments at 260 missiles each, while North Korea has 270, and Poland has 240. The Chinese also deploy the HY-2, an upgrade of the SA-2, in relatively large numbers.

[edit] Description

S-75 Dvina with V-750V 1D missile on a launcher

The S-75 system is organized into a regimental structure with three battalions consisting of launcher sites, and the regimental headquarters with early-warning radars and communications. Each battalion consists of six semi-fixed trainable single-rail launchers for their V-750 missiles about 60-100 meters apart, deployed in a hexagonal "flower" pattern around the central radars and guidance systems. It was the unique shape of the "flower" that led to the sites being easily recognizable in reconnaissance photos. Typically another six missiles are stored on tractor-trailers near the center of the site.

The V-750 is a two-stage missile, consisting of a solid-fuel booster and a storable liquid-fuel upper stage burning red fuming nitric acid as the oxidizer, and kerosene as the fuel. The booster fires for about 4-5 seconds, and the main engine for about 22 seconds, by which time the missile is traveling at about Mach 3. The booster mounts four large cropped-delta wing fins with small control surfaces in their trailing edges, used to control roll. The upper stage has smaller cropped-deltas near the middle of the airframe, with a smaller set of control surfaces are at the extreme rear and (in most models) much smaller fins on the nose.

The missiles are guided using radio control signals from the guidance computers at the site, sent on one of three channels. The earlier SA-2 models received their commands via two sets of four small antennas in front of the front most fins, while the D models and on used four much larger strip antennas running between the forward and middle fins. The guidance system at an SA-2 site can handle only one target at a time, but can direct three missiles against it. Additional missiles could be fired against the same target after one or more missiles of the first salvo had completed their run and the radio channel was freed.

The missile typically mounts a 195 kg (430 lb) fragmentation warhead, with proximity, contact and command fusing. The warhead has a lethal radius of about 65 m (215 ft) at lower altitudes, while at higher altitudes the thinner atmosphere allows for a wider radius of up to 250 m (820 ft). The missile itself is accurate to about 75m (250 ft), which explains why two were typically fired in a salvo. One version, the SA-2E, mounted a 295 kg (650 lb) nuclear warhead of an estimated 15 kT yield, or a conventional warhead of similar weight.

Typical range for the missile is about 45 km (30 miles), with a maximum altitude around 20,000 m (60,000 ft). The radar and guidance system imposed a fairly long short-range cutoff of about 500-1,000 m (3,000 ft), making them fairly safe to attack at low level.

'Fan Song' radar (left) and what looks like a 'Low Blow' to the right. Photo by Nellis AFB.

The main search radar, known as the Spoon Rest in the west, has a range of about 275 km (170 miles), while the tracking/guidance radars, the Fan Song, have a range of about 65 km (40 miles). Earlier versions used a targeting radar known as Knife Rest, which was replaced in Soviet use, but can still be found in older installations. The Fan Song system consisted of two antennas operating on different frequencies, one for elevation and the other for azimuth. The regimental HQ also includes a Spoon Rest, as well as a Flat Face long-range C-band radar and the Side Net height-finder. Information from these radars is forwarded to the battalion Spoon Rest operators to allow them to coordinate their searches.

[edit] Models

V-750 missile in transit.

SA-2A; S-75 Dvina (Russian Двина - Dvina River) with Fan Song-A guidance radar and V-750 or V-750V missiles. Initial deployment version from 1957. 10.6 m (34.8 ft) long, with a booster diameter of 0.65 m (25.5 in), and missile diameter 0.5 m (19.7 in). Launch weight is 2287 kg (5,041 lb). The missile has a maximum effective range of 30 km (19 miles), a minimum range of 8 km (5 miles) and an intercept altitude envelope of between 450 and 25,000 m (1,500-82,000 ft).

SA-N-2A; S-75M-2 Volkhov-M (Russian Волхов - Volkhov River): navalized version of the -2A fitted to the Sverdlov Class cruiser Dzerzhinski. Generally unsuccessful and not fitted to any other ships.

SA-2B; S-75 Desna (Russian Десна - Desna River), Fan Song-B radars and V-750VK and V-750VN missiles. Second deployment version, entered service in 1959. The missiles were slightly longer at 10.8 m (35.4 ft), due to a more powerful booster. The system could engage targets at altitudes between 500 m and 30 km (1,640-98,450 ft) and ranges up to 34 km (21 miles).

SA-2C; S-75M Volkhov, Fan Song-C radar with V-750 m missiles. Improved -2B deployed in 1961. The V-750 m was externally identical to the V-750VK/V-750VN, but with improved performance for range up to 43 km (27 miles) and reduced lower altitude limits of 400 m (1,312 ft).

SA-2D; Fan Song-E radar and V-750SM missiles. Differed significantly from the A/B/C in having the new antennas and a longer barometric nose probe and several other differences associated with the sustainer motor casing. The missile is 10.8 m (35.4 ft) long, has the same body diameters and warhead as the SA-2C, but the weight is increased to 2450 kg (5,400 lb). The effective maximum range is 43 km (27 miles), the minimum range is 6 km (4 miles) and the intercept altitude envelope is between 250 and 25000 m (820-82,000 ft). The Fan Song-E was introduced to make it more difficult to jam.

SA-2E: Fan Song-E radar and V-750AK missiles. Similar rocket to the D, but uses a bulbous warhead section lacking the forward fins. The SA-2E is 11.2 m (36.7 ft) long, has a body diameter of 0.5 m (19.7 in) and weighs 2450 kg (5,400 lb) at launch. The missile can be fitted with either a command detonated 15 kT nuclear or 295 kg (650 lb) conventional HE warhead.

SA-2F: Fan Song-F radar and V-750SM missiles. After watching jamming in Vietnam and the Six-Day War render the SA-2 completely ineffective, the existing systems were quickly upgraded with a new radar system designed to help ignore wide-band scintillation jamming. The command system also included a home-on-jam mode to attack aircraft carrying strobe jammers, as well as a completely optical system (of limited use) when these failed. F's were developed starting in 1968 and deployed in the USSR later that year, while shipments to Vietnam started in late 1970.

S-75M Volga (Russian С-75М Волга - Volga River). Version from 1995.