Introduction
The S-75 / SA-2 Guidelinefamily of SAM systems remains the most widely exported area defencemissile system, and was supplied in large numbers by the Soviets toWarsaw Pact nations, Third World Soviet allies and other non-alignednations. Over thirty nations deployed one or another variant of theSA-2, and China manufactured indigenous derivatives well after thisdesign was out of production in the Soviet Union.
The basic design qualifies as semi-mobile, requiring several hours toset up or redeploy a battery. Typical battery composition is a singleSNR-75 Fan Song series engagement radar, six SM-90 single raillaunchers, and multiple PR-11AM transporter/transloader trucks carryingreload rounds for the SM-90s.
Many S-75 operators deploy the system in fixed sites, with revetmentsusing concreted pads and bays, and/or earthwork berms, to protect themissile system components.
The PLA reverse engineered the Soviet V-75/S-75 Dvina / SA-2 GuidelineSAM system during the 1960s, including the SNR-75 Fan Song radar, theSM-90 launcher and the PR-11AM transporter/transloader. Since then thePLA developed a significantly improved HQ-2B variant.
RSNA-75/SNR-75Fan Song Engagement Radar
The Fan Song is the engagementradar for the S-75/SA-2 family of SAMs. First deployed in strengthduring the Vietnam conflict, and later used extensively in the MiddleEast and Africa, the SA-2 was the first Soviet SAM to be used in angerand accounted for large numbers of Western aircraft until electroniccountermeasures were developed. The system was cloned by PLA and stillremains widely in use, even though Russia has replaced it with theSA-10/20 system.
The are at least six known variants, one of which is a PLA clone.Details of PLA modifications to the design are not public knowledge.There are sufficient differences in the PLA designs to regard these asunique derivatives. The antenna configuration of the PLA variantsgenerally follow the Fan Song A arrangement.
The SNR-75 family of radars employ, by modern standards, a complexantenna arrangement which is employed to effect range and angletracking of the intended target, and of the transponder beacon in thetail of the missile round. The proximity fused missile round is“dumb” in the sense that it is a pure command link design, whichis flown to a collision with the target using a command uplink embeddedin the SNR-75 radar.
A more detailed discussion can be found under Engagement andFire Control Radars.
| 1D (V-750) Guideline Cutaway (viaVestnik-PVO/Tekhnika i Vooruzheniya) | |
| 1 | Radio proximityfuse transmit antenna |
| 2 | Shmel radioproximity fuse |
| 3 | V-88 warhead |
| 4 | Radio proximityfuse receive antenna |
| 5 | AK-20F oxidiser1melange tank |
| 6 | TG-02propellanttank |
| 7 | Compressed air tank |
| 8 | AP-75 autopilotmodule |
| 9 | FR-15Yu commandlink module |
| 10 | Battery |
| 11 | Transducer |
| 12 | Cruciform controls |
| 13 | OT-155 Isonite(isopropyl nitrate) turbopump gas-generator propellant tank |
| 14 | Isayev S2.711(S5.711) liquidpropellant sustainer powerplant |
| 15 | Adaptor fairing |
| 16 | PRD-18 boostpowerplantwith2-4 sec burn duration / 14 tubes of NMF-2 propellant |
| Note 1:Oxidiser to propellant ratio ~3.2:1 AK-20F oxidiser ~80% nitricacid / ~20% N2O4 /fluorine inhibitor additive TG-02propellant [GOST 17147-80] 50% isomeric xylidine / 48.5%triethylamine / 1.5% diethylamine | |
S-75 / SA-2 Guidelineengagement envelope (Almaz image). 
1D/13D/DM/DA/DAM/20D/DP/DSU/5Ya23/15DSurface toAir Missiles
The configuration of the 1Dthrough 5Ya23 missiles is a direct evolution of the earlier SA-25/S-25/ SA-1 Guild, itself evolved from the 1944 German Wasserfall design.Unlike its predecessors, the S-75 / SA-2 family of missiles were twostage designs, using a solid rocket first stage booster for launch anda variable thrust liquid propellant motor sustainer. Midbody cruciformwings were employed to improve range and turning ability, with canardand tail winglets for pitch, roll and yaw control and stability.
By modern standards, the missiledesign is unusually simple, with most of the complexity in the liquidpropellant sustainer and fuel system. The choice of this sustainer fortwo reasons, the first being immaturity of high impulse solidpropellants, the second being in the ability to modulate thrust throughthe flight profile.
An important consideration is theSoviet philosophy of making the missile round as simple and cheap aspossible, and putting the cost and complexity into the engagementradar. The operational economics of this model were to minimise thecost of the expendable component of the weapon system.
The nose of the missile housesthe radio proximity fuse. In early variants this was the 5E11 Shmelseries, the later Ovod variant, and then the 5E29. Early variants usedseparate linear transmit and receive antennas flush with the skin ofthe missile, later variants used a characteristic dielectric bandradome. Later variants included programmable ECCM modes, such asalternating emissions between the two hemispheres of antenna coverage.
Immediately aft of the fuse isthe V-88 series blast fragmentation warhead, which weighs between 190kg and 250 kg, depending on missile variant. The large warhead size wasintended to produce a large lethal envelope, to offset the accuracylimitations of the command link guidance and proximity fusing. Warheadperformance evolved over the life of the missile, the early 11D roundproducing 8,000 fragments, the 20D 32,000 fragments and the very late5Ya23 29,000 fragments. Initial fragment velocity was 2,500 m/s. Thetiming of the proximity fuse trigger point was programmable via thecommand uplink, with shorter delays for closing versus recedingtargets. Lethal radius was nominally 60 metres (~400 ft lethaldiameter).
Much of the missile's internalvolume is occupied with propellant tanks for the sustainer engine.
The 43 kg dry weight IsayevS2.711(S5.711) liquidpropellant powerplant burns a hypergolic propellant mix. The oxidiseris either AK-20F or AK-20K fuming nitric acid melange depending on themotor variant, comprising ~80% nitricacid and ~20% N2O4 with an inhibitor additive.The fuel is TG-02, comprising 50% isomeric xylidine, 48.5%triethylamine and 1.5% diethylamine, this propellant mix wasessentially an evolution of the 1944 Wasserfall fuel. The S2.711 usedin early variants produced a thrust rating between 2,650 and 3,000 kp(5,800 lbf and 6,600 lbf), the later S2.720 used in the 20D roundproduced between 2,075 kp and 3,500 kp (4,580 lbf and 7,700 lbf) thrustusing a different propellant mix. Specific impulse for the S2.711 was224 up to 252.7 kp.sec/kg.
The turbopump for the enginewas fuelled by a tank of OT-155 Isonite(isopropyl nitrate). The propellant payload permitted a burn durationbetween 25 and 60 seconds, subject to thrust profile. All propellanttanks were pressurised from a compressed air tank.
This fuel system arrangement as used in the earlier 1D through 11Dvariants was supplanted in the 20D and later missile rounds. The latervariants used the AK-27I oxidiser, comprising ~73% nitricacid, ~27% N2O4 and an inhibitor additive.The fuel was TM185 comprising 56% Kerosene and 40% Trikresol. As thisfuel did not ignite spontaneously, an additional tank of TG-02 “starterfuel” was employed to ignite the rocket. The later propellant mix wasmore energetic and provided better storage life, with the TM185 fuelbeing less toxic, and the primary propellant components safer to fueland defuel.
The first stage which was used to accelerate the missile at launch useda PRD-18 solid rocketpowerplant with 2-4 sec burn duration. This design used 14 tubes ofNMF-2 propellant and a variable cross section throat.
The missile guidance system is relatively simple, comprising anautopilot and a command link receiver, with a missile beacon in thetail to facilitate tracking by the Fan Song radar.
The command link channel produced four distinct pulse modulatedwaveforms. The K1 and K2 waveforms carried climb/dive and left/rightturn commands, the K3 waveform arms the radio proximity fuse, and theK4 waveform is used to program the proximity fuse delay depending onmissile engagement geometry.
In operation, the Fan Song radar would track the target andcontinuously compute an optimal missile trajectory for intercept, whiletracking the missile via its transponder beacon. The uplink would thenbe used to continuously drive the missile flightpath as close aspossible to the intended trajectory, in a closed loop scheme.
Two control laws were employed, the“Treokh Tochek (TT - threepoint)” and “Polavinoye Spravleniye(PS - half correction)” techniques.
The TT control law is essentially a Soviet implementation of Command toLine of Sight (CLOS), where the missile flightpath is continouslyadjusted so that it follows the line of sight between the radar and thetarget. While this technique does attempt to minimise flightpathlength, it does not maximise missile range per propellant payload, andtends to subject the missile, in some geometries, to large transverseaccelerations. The latter facilitated defeat of the missile by high Gmanoeuvres.
The PS control law was more sophisticated and used against manoeuvringtargets. An earth bias was often included in the control law whenfiring against low altitude targets, to preclude unwanted proximityfuse initiation, or inadvertent ground collision caused by autopilotinputs.
The command link guidance scheme and need to carefully select controllaws and radar modes resulted in a need for high levels of operatorskill and a good understanding of engagement geometries. The combateffectiveness of the S-75 / SA-2 Guideline varied widely as a result,with Warsaw Pact instructors and their Vietnamese students typicallyperforming much better in combat compared to their counterparts in theMiddle East.
Production and Exports
The S-75 / SA-2 Guideline was manufactured by the Soviets from themid-1950s through to the 1980s, with spare part manufacture to supportexported installations continuing since then. The Chinese reverseengineered the missile system during the 1960s, as the HQ-1, and thenproduced indigenous improved HQ-2 variants thereafter. The Soviets andChinese have exported the weapon globally, and it would appear thatthis system has been built in more variants and exported more widelythan any other SAM system.
Attempting to survey current global deployments of this system is achallenging task. While Russia retired the system, it remains deployedin large numbers by China, by many former Soviet Republics, some formerWarsaw Pact nations, and many former Soviet client nations in thedeveloping world. Much of Iran's air defence system comprises Chinesesupplied HQ-2s.
A number of electronics and mobility upgrades have been developed, amore detailed discussion can be found under Legacy Air DefenceSystem Upgrades.
