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S-75 Dvina

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The first widely deployed Soviet surface-to-air missile was the S-75 Dvina, designated by NATO as the SA-2 GUIDELINE. In the Soviet nomenclature, the S-75 was the entire system of missiles, radars, launchers, etc., while the actual missile was the V-750 in its first version[1]. Both electronics and missiles were constantly upgraded over the system' life.

Originally deployed to protect Soviet areas other than Moscow, which had a special system (NATO designation SA-1), the S-75 is a transportable rather than mobile system: it could not operate on the move, but could be delivered to an area and set up in a reasonable period of time (days).

The V-75 (SA-2) surface-to-air missile system was designed for the defense of both fixed targets and field forces. The V-75 was designed to cope with the threat posed by small groups of aircraft rather than massed raids. Flexibility and mobility are its chief advantages over the SA-1.

In contrast to the massive SA-1 sites, each of which is capable of defending only a limited sector around the target area, each SA-2 site is capable of 360° coverage. This flexibility is obtained at the expense of target handling capacity and rate of fire relative to the SA-1. It is intended for defeat of manned and pilotless air attack weapons at the heights from 100 m to 30 km, which fly with speeds of up to 3000 km/h, at the distances to 58 km.[2]

Unit organization

Air defense units armed with the Dvina were formed as regiments, usually of three battalions each, with several batteries of six launchers and the associated radars. Some operators, however, do not use the battalion as a grouping of several batteries, but either assumes one firing battery per battalion, no battalion level at all. The regiment and the battery levels are the operational one; the battalion is more an administrative level, for doing such things as organizing logistics.

Although there are a variety of arrangement patterns, all sites consist of six launching positions -- usually revetted - deployed around a guidance radar and linked by service roads to facilitate loading. While the sites were permanent installations, all operating components of the system are mounted on wheeled vehicles and are capable of movement by road or raiL [2]

The 295 kg nuclear warhead used only on the SA-2E variant is believed to have a yield of 15 kT.

The V-75 system is designed to be simple and easy to operate with the minimum of specialized training. The standard deployment pattern of a battalion site consists of six semi-fixed trainable single rail launchers are deployed in the familiar hexagon arrangement about 60-100 meters apart. The launchers may be dug into pits, left at ground level or hardened in concrete revetments. The battery command post fire control team and its computer, the FAN SONG missile control radar, the P-12 SPOON REST early warning radar, and typically six reload rounds on their articulated trailers are all located in the center of the launchers array.

Missiles

With a solid-fuel booster and a liquid fuel sustainer rocket engines, the V-75 can engage medium to high altitude targets. It had little low-altitude capability, which had the tactical implication, used by SEAD aircraft against V-75/SA-2 sites in North Vietnam, that the SEAD planes could attack the missile site by flying at low altitude, typically to drop cluster bombs. A countermeasure was to surround the missile site with low-level anti-aircraft artillery (AAA), but the AAA would have only a very limited time to engage the low-flying aircraft.

A set of four cropped delta-shaped wings are located near the mid-section, with a second in-line set of smaller fixed fins at the nose, and a third in-line set of slightly larger powered control fins at the tail.[2] The missile physically resembles its rough U.S. counterpart, the MIM-3 Nike Ajax.

Warhead

While a nuclear warhead was available for the E variant of the V-75, most warheads were blast-fragmentation, with a 195 KG total warhead weight, of which 130 KG was explosive. The warhead was physically behind the nose-mounted guidance electronics, but in front of the first set of fins. The 295 kg nuclear warhead used only on the SA-2E variant is believed to have a yield of 15 kT.

Effective warhead radius varied with altitude, and was greater (250 meters) in the thinner air of higher altitude. At medium altitudes, the blast radius dropped to 100-120 meters, with a lethal radius of 65 meters.

Electronics

The SPOON REST search radar, at a battery, could track three targets, but the FAN SONG fire control radar can manage only one missile at a time. [2] It was quite common practice for a battery to have additional FAN SONGs, ideally one per launcher, so that several missiles could be launched at a target.

It is still quite common practice, even with advanced systems such as SM-2 and PATRIOT, to fire at least two SAMs at a target. In addition, once the first salvo completes its flight, if the target has not been destroyed, additional salvoes may be launched.

Firing battery level

The first surface-to-air missile (SAM) system deployed by the Soviet Union, the S-75 Dvina (NATO identifier SA-2, designation name GUIDELINE) had, in its original versions, two primary radars at the firing battery level, SPOON REST long-range search (range 170mi/275km) and FAN SONG C-band (range 40 mi/65 KM) acquisition/fire control. Later versions increased both the radar's range and resistance to jamming.

FAN SONG has two antennas operating on different frequencies, one to track the target's compass bearing and the other to track its altitude.

Engagement process: electronic and physical

To understand what happens when an S-75 is fired at a target, it will be confusing to try to think of the electronic tracking and control, versus the engine and aerodynamic controls of the missile.

  1. Target range, altitude and bearing, as determined by search radar and associated computers, are converted to launcher-relative azimuth and elevation for the best hit probability, and then sent to the battery by wired or wireless communications. The firing command will not be sent if the fire control system determines that a given missile does not have enough propulsion energy and aerodynamic control to put itself on the computed starting trajectory,.
  2. As soon as it is fired, the missile uses its aerodynamic controls to move from its alignment on the launcher proper, to the calculated azimuth and elevation. There is relatively little intelligence on the missile itself; the corrections are sent by the FAN SONG radar, which tracks both a single target and a single missile. Simultaneously, the missile is gaining speed, using a 4.5 second burn on its solid rocket motor, which drops away from the missile after burnout. The liquid fuel motor burns for 22 seconds. After that burns out, the missile has enough speed to allow its aerodynamic surfaces to allow continuing course adjustments.
  3. As the missile nears its target, the FAN SONG sends a command to arm the missile detonation system. The missile warhead will detonate on contact with the target, by proximity from the missile's final guidance, or by command signal.

Especially after burnout of the liquid fuel engine, the S-75 cannot maneuver too radically; it relies on speed (typically Mach 3.5) to overcome its target, rather than maneuvering. Fighter aircraft, using both power and aerodynamics, are more maneuverable, and, if the S-75 were seen, a skilled pilot could often turn into the missile's path in a manner that confused its onboard fuzing such the missile would fly path. Of course, if the ground controller saw this happening and could command-detonate the missile when the missile was about to miss, it would be a very bad day for the target. The missile had an accuracy of about 75 meters, and a relatively large warhead to make up for inaccuracy.

Regimental command and control level radars

SA-2 regimental headquarters have an additional SPOON REST, a truck-mounted FLAT FACE long-range radar as well a trailer-mounted SIDE NET height-finder; the regimental headquarters coordinates the multiple batteries. See for details of the electronics. A control truck linked to the firing units via a MERCURY GRASS communications system.

Combat record

The U-2 incident, of 1 May 1960, was the first combat success of the S-75. Soviet air defenses had been aware of the high-altitude U-2, flown by Francis Gary Powers, but both fighters and SAMs could not engage it at operational altitude. It is generally thought that the U-2 had had an engine flameout and was at a much lower altitude when hit.

An operational U-2, however, was shot down over Cuba on October 27, 1962. The pilot, MAJ Rudolf Anderson, was killed. It is not clear if he was at a lower altitude, if the Cubans used an improved missile version, or there was some other peculiarity of engagement geometry that let the SAM reach the U-2. Against aircraft flying at lower altitudes, the S-75 could be quite effective unless there was extensive jamming and ECM support, as well as dedicated SEAD missions to attack the S-75 sites, and air tactics to outmaneuver the S-75.

S-75's were first detected in North Vietnam in 1965. [3]Over North Vietnam S-75's downed 15 B-52 heavy bombers, and between 68 to 105 fighter-bombers, with a great many more fighter-bombers damaged. U.S. electronic countermeasures and SEAD tactics constantly improved, but so did the Soviet equipment and tactics. For the maneuverable fighters, accompanied by WILD WEASEL SEAD missions, the loss rate was below 0.03% per sortie. When attacking a SAM site, however, the SEAD aircraft came into range of anti-aircraft artillery that could engage them below the S-75 minimum altitude.

Flying at medium to high altitude, B-52 bombers had very little maneuverability against the missiles, but more powerful electronic countermeasures than fighters. In the worst case of when the B-52s, in the intense Operation LINEBACKER II campaign of 1972-3, flew over sites covered by SAMs, they suffered 3% per sortie loss rate until their tactics radically changed.

U.S. electronic warfare intended to counter this missile concentrated on its tracking and command guidance radar; the North Vietnamese, during Linebacker II, fired salvoes of the missile, not relying on active guidance, and triggering them with the proximity fuze, against which there were few countermeasures. As many as 2,000 missiles may have been needed for those 15 kills. Nevertheless, the "flying telephone pole", as the long, thin missile was described, was taken as a very serious threat by B-52s.

The S-75 was less effective in the Arab-Israeli wars of 1967 and 1973, partially because the Israeli aircraft were not as hampered by restrictive rules of engagement as were the U.S. aircraft in Vietnam. Political rules forced the U.S. aircraft into sometimes predictable flight paths, while the Israelis could come from any direction. By the Balkans and Iraqi operations of the 1980s and 1990s, the S-75 was much less effective than newer missiles, especially against aircraft with even more modern countermeasures and against air forces with sophisticated SEAD tactics. Nevertheless, they still were a threat; an aircraft evading a more modern SAM might fly into the engagement geometry of a SA-2.[1]

Derivatives

The People's Republic of China, Egypt, and possibly other countries produced derivatives. China, in particular, mixed the basic antiaircraft versions with home-on-jam variants to turn electronic defenses into liabilities.

References

  1. 1.0 1.1 Astronautix, S-75
  2. 2.0 2.1 2.2 2.3 Globalsecurity, "V-75 SA-2 GUIDELINE", Globalsecurity
  3. "First NVN SAM strike", Marine Corps Aviation Reconnaissance Association