How does S-75 SAM's SNR-75/Fan Song radar works?

[Dilandu]

Recently after having a discussion about legacy S-75 SAM system, I decided to look more for data about it - and to my puzzlement found that many sources describe the SNR-75 (NATO "Fan Song") radar operations wrongly or with significant mistakes. And therefore many peoples have rather wrong assumption, how exactly this complicated thing worked.

The SNR-75/"Fan Song" radar was the heart of the whole S-75 family of SAM's. It was a direct decendant of B-200 multi-channel radar, used in monumental S-25 "Berkut" multi-channel SAM. But SNR-75, while following the same general idea - scanning for azimuth and elevation by two synchronized antennas, simultaneous track-while-scan, using the same radar to both track the target and guide missiles - was from the beginning designed to be smaller, cheaper, transportable (S-25's B-200 was fixed in place) and trainable (S-25's B-200 could not train - its two antennas required precise positioning relative to each other, and were too heavy to be put on single frame - so it could only scan the targets in fixed area).


Let's look at basic model - for SA-75 "Dvina" SAM system:



As you could see, there are three antennas over the cabin:

* On the right side, a vertical through-like antenna (P-12) was placed to scan for elevation. The scanning was achieved by the use of Lewis rotating scanner, fed from separate magnetron;
* On the top of cabin, a horizontal through-like antenna (P-11) was placed to scan for azimuth. It too used the Lewis rotating scanner, and its own magnetron. The scanners were synchronized, so both vertical and horizontal beams moved together - but on different working frequences, so they could be easily separated on receive;
* On the left side, a parabolic dish antenna (P-16) was placed to send guidance command to missiles. It wasn't scanning, it was merely a transmitter that send command signal in relatively narrow area;

All antennas are put on single frame, rotating in elevation, so they always maintain the same position relatively to each other. Training the whole antenna set is achieved by rotating the whole cabin on its mount.

When scanning for target (usually by warning of separate early warning radar), two antennas produce synchronized fan-shaped beams (about 7 degrees wide) moving at right angle to each other in the 20 degrees sector in front of the cabin. The recieved echo signals were visualized by a pair of B-scopes; one for azimuth, one for elevation, both produced range data also. So basically the SNR-75 radar have two separate channels for azimuth and elevation data, which weren't directly connected.

When the target(s) was detected, operators used manual controls to turn the SNR-75 in azimuth and elevation until the chosen target was directly in the middle of both scopes - which means, at the direct boresight of both azimuth and elevation antennas. Then the azimuth, elevation and range gates were set for tracking.

The radar have three tracking modes; automatic (used for single targets), manual (used for tight group targets that automatic have troubles discriminating between), and semi-manual (the azimuth and elevation were tracked automatically, while range was set manually). The third mode was used because in 1950s range jamming was considered the greatest problem - it was rather easy to implement on plane jammers.

One important detail - the SNR-75 continued scanning the area around target even while scanning it. Any other targets nearby (within the 20 degrees angle) were therefore constantly scanned, and if operators decided to switch to another target, it could be done without initiating new search pattern.



When the target was sucsessfully tracked - manually or automatically - the missiles came into play. Up to six launchers were directly connected with SNR-75 by cables, and followed radar azimuth and elevation. The launched missiles were, therefore, "thrown into basket" of constantly scanning beams. The same beams that were used to scan for target, were also used to scan for flying missiles & determine their position in scanned sector. A special circuit amplified the transponders reports & filtered them as missile position data for fire control systems.

Tracking of the missiles was fully automatic, by using the onboard transponders on missiles. The P-16 parabolic dish antenna was constantly sending identification signals, on which missile transpoders replied, and those replies were received by scanning antennas. The missile track gates were actually prepared before missiles were launched, and "moved" along their projected courses until missile actually meet the track gate. After that, the track gate "stuck" to missile and fire control system started to track it. Three time-modulated fire control channels were available, which means up to three missiles could be controlled simultaneously (all against the same target).

After the missile were gained by fire control channel, the fire control system started to generate course commands to guide missile to target. Two guidance modes were available:

* Automatic command-to-the-line-of-sight (ACLOS) mode, when missiles were simply hold on the same azimuth and elevation as target. This method was considered efficient only on relatively short distances, but have an advantage of not requiring range data;
* Automatic "semi-straightening" mode, when a leading point was calculated for a target, and missiles were guided straight to that point. This method was used for long-range interceptions, since missile did not need to "chase" the target and followed more efficient trajectory;

The control signals were time-modulated, with "opening" pulse being the transponder identification pulse, and then a course correction commands (for each of control axis separatedly) followed. At the end of control period there were time slots for two specific high-amplitude command signals; the first set the missile proximity fuze delay mode (it have several), and the second activated the fuze itself, when the missile was relatively close to target (so the target would not have enough time to jam it or something).

The later modes - S-75 "Desna" and S-75M "Volkhov" - generally used the same radar set, but with improved functionality. Since S-75M "Volkhov" have much longer range than basic SA-75, its usual wide-beam scanning mode was not sufficient anymore; on long distances, the target data become too inaccurate.



To solve the problem, a pair of parabolic dish antennas were installed, each paired with one through antenna & fed from the same magnetron. Those parabolic dishes were used to generate very narrow, pencile-like beams, for long-range target acquisition. The through-like antennas served as receivers for the echos.

The improved radar thus have two main work modes: a narrow beam, and wide beam:

* A narrow-beam mode was used to seek and acquire targets at long distances with pencil-like beams scanning the narrow (+/- 3.45 degrees) sector. This mode was also used to seek for low-altitude targets, to reduce ground clutter;
* A wide-beam mode was used to seek and acquire targets at short distances with broad fan-like beams, scanning the wide (+/- 10 degrees) sector. The wide beam allowed for much quicker search and acquisition - important when the target was close and moving fast! - but wasn't accurate at long distances;

That's what I wanted to describe about those legacy Soviet radars. Pretty sophisticated tech for 1950s, heh? As far as I know, the cotemporary Western radars did not use two-beam track-while-scan mode.

 

[T. A. Gardner]

Recently after having a discussion about legacy S-75 SAM system, I decided to look more for data about it - and to my puzzlement found that many sources describe the SNR-75 (NATO "Fan Song") radar operations wrongly or with significant mistakes. And therefore many peoples have rather wrong assumption, how exactly this complicated thing worked.

The SNR-75/"Fan Song" radar was the heart of the whole S-75 family of SAM's. It was a direct decendant of B-200 multi-channel radar, used in monumental S-25 "Berkut" multi-channel SAM. But SNR-75, while following the same general idea - scanning for azimuth and elevation by two synchronized antennas, simultaneous track-while-scan, using the same radar to both track the target and guide missiles - was from the beginning designed to be smaller, cheaper, transportable (S-25's B-200 was fixed in place) and trainable (S-25's B-200 could not train - its two antennas required precise positioning relative to each other, and were too heavy to be put on single frame - so it could only scan the targets in fixed area).


Let's look at basic model - for SA-75 "Dvina" SAM system:

View attachment 795138

As you could see, there are three antennas over the cabin:

* On the right side, a vertical through-like antenna (P-12) was placed to scan for elevation. The scanning was achieved by the use of Lewis rotating scanner, fed from separate magnetron;
* On the top of cabin, a horizontal through-like antenna (P-11) was placed to scan for azimuth. It too used the Lewis rotating scanner, and its own magnetron. The scanners were synchronized, so both vertical and horizontal beams moved together - but on different working frequences, so they could be easily separated on receive;
* On the left side, a parabolic dish antenna (P-16) was placed to send guidance command to missiles. It wasn't scanning, it was merely a transmitter that send command signal in relatively narrow area;

All antennas are put on single frame, rotating in elevation, so they always maintain the same position relatively to each other. Training the whole antenna set is achieved by rotating the whole cabin on its mount.

When scanning for target (usually by warning of separate early warning radar), two antennas produce synchronized fan-shaped beams (about 7 degrees wide) moving at right angle to each other in the 20 degrees sector in front of the cabin. The recieved echo signals were visualized by a pair of B-scopes; one for azimuth, one for elevation, both produced range data also. So basically the SNR-75 radar have two separate channels for azimuth and elevation data, which weren't directly connected.

When the target(s) was detected, operators used manual controls to turn the SNR-75 in azimuth and elevation until the chosen target was directly in the middle of both scopes - which means, at the direct boresight of both azimuth and elevation antennas. Then the azimuth, elevation and range gates were set for tracking.

The radar have three tracking modes; automatic (used for single targets), manual (used for tight group targets that automatic have troubles discriminating between), and semi-manual (the azimuth and elevation were tracked automatically, while range was set manually). The third mode was used because in 1950s range jamming was considered the greatest problem - it was rather easy to implement on plane jammers.

One important detail - the SNR-75 continued scanning the area around target even while scanning it. Any other targets nearby (within the 20 degrees angle) were therefore constantly scanned, and if operators decided to switch to another target, it could be done without initiating new search pattern.

View attachment 795160

When the target was sucsessfully tracked - manually or automatically - the missiles came into play. Up to six launchers were directly connected with SNR-75 by cables, and followed radar azimuth and elevation. The launched missiles were, therefore, "thrown into basket" of constantly scanning beams. The same beams that were used to scan for target, were also used to scan for flying missiles & determine their position in scanned sector. A special circuit amplified the transponders reports & filtered them as missile position data for fire control systems.

Tracking of the missiles was fully automatic, by using the onboard transponders on missiles. The P-16 parabolic dish antenna was constantly sending identification signals, on which missile transpoders replied, and those replies were received by scanning antennas. The missile track gates were actually prepared before missiles were launched, and "moved" along their projected courses until missile actually meet the track gate. After that, the track gate "stuck" to missile and fire control system started to track it. Three time-modulated fire control channels were available, which means up to three missiles could be controlled simultaneously (all against the same target).

After the missile were gained by fire control channel, the fire control system started to generate course commands to guide missile to target. Two guidance modes were available:

* Automatic command-to-the-line-of-sight (ACLOS) mode, when missiles were simply hold on the same azimuth and elevation as target. This method was considered efficient only on relatively short distances, but have an advantage of not requiring range data;
* Automatic "semi-straightening" mode, when a leading point was calculated for a target, and missiles were guided straight to that point. This method was used for long-range interceptions, since missile did not need to "chase" the target and followed more efficient trajectory;

The control signals were time-modulated, with "opening" pulse being the transponder identification pulse, and then a course correction commands (for each of control axis separatedly) followed. At the end of control period there were time slots for two specific high-amplitude command signals; the first set the missile proximity fuze delay mode (it have several), and the second activated the fuze itself, when the missile was relatively close to target (so the target would not have enough time to jam it or something).

The later modes - S-75 "Desna" and S-75M "Volkhov" - generally used the same radar set, but with improved functionality. Since S-75M "Volkhov" have much longer range than basic SA-75, its usual wide-beam scanning mode was not sufficient anymore; on long distances, the target data become too inaccurate.

View attachment 795162

To solve the problem, a pair of parabolic dish antennas were installed, each paired with one through antenna & fed from the same magnetron. Those parabolic dishes were used to generate very narrow, pencile-like beams, for long-range target acquisition. The through-like antennas served as receivers for the echos.

The improved radar thus have two main work modes: a narrow beam, and wide beam:

* A narrow-beam mode was used to seek and acquire targets at long distances with pencil-like beams scanning the narrow (+/- 3.45 degrees) sector. This mode was also used to seek for low-altitude targets, to reduce ground clutter;
* A wide-beam mode was used to seek and acquire targets at short distances with broad fan-like beams, scanning the wide (+/- 10 degrees) sector. The wide beam allowed for much quicker search and acquisition - important when the target was close and moving fast! - but wasn't accurate at long distances;

That's what I wanted to describe about those legacy Soviet radars. Pretty sophisticated tech for 1950s, heh? As far as I know, the cotemporary Western radars did not use two-beam track-while-scan mode.

Yes, and no. They were still just pulse radars using conical scan. Basically, the Russians, at that time, were still stuck with largely Western WW 2 technology like the SCR 584 as a basis for design. Use of a doppler feature helped with chaff, but the basic methods used for scanning allowed for relatively easy noise, range, and angular gate pull off jamming. A lack of frequency diversity didn't help. These combined to make the guidance system, in all forms, pretty easy to jam. This became serious enough in Vietnam that the Russians adopted a television optical guidance system that was semi-manual to back up the radar system. It was more desperation than inspiration.

https://dn720703.ca.archive.org/0/items/history-of-the-electro-optical-guided-missiles/SA-2F_English.pdf

https://ia801900.us.archive.org/26/items/history-of-the-electro-optical-guided-missiles/S-75%20family.pdf

The US adopted far more sophisticated systems much earlier. Nike Ajax, for example, used the first operational monopulse radar system for guidance. The radars associated with it, and then HAWK were very frequency diverse making jamming harder. They also had a back up beam riding mode that was specifically designed for high jamming environments where burn through was possible. While this reduced the effective range of these systems, they could remain viable in the face of heavy jamming, unlike the S-75 system.

The Talos missile system used a Lundberg lens with monopulse (the SPG 49) and a separate guidance radar (SPW-2) that could fly the missile to an intercept without being locked on the target. This made jamming the in-flight radar difficult or impossible and the SPG -49 difficult to jam as it only needed to illuminate the target in the final phase of intercept.

https://www.okieboat.com/SPG-49 description.html

SPW-2 Description

The really important system in all of these was the fire control computer. The speed of it, computation-wise, was what was critical. This was an area that the Russians had difficulty keeping up with the West in. It wasn't they didn't or couldn't make faster systems, but rather that they were nowhere near able to make production runs with their levels of manufacturing available. S-25 Berkut for example, pretty much ate up every bit of available tube production outside of vital military systems and even made a dent in those. If you can't make enough sophisticated tubes to meet demand...

 

[T. A. Gardner]

The US system used with Nike Ajax, somewhat contemporary to the S-75, was to use two radars using a pencil beam, operating with a monopulse signal output. One radar tracked the target, the other tracked the missile. Respectively, these were called the Target Tracking Radar (TTR) and Missile Tracking Radar (MTR). Both were similar in design but ran on different frequencies to make jamming harder. The MTR included a feed for commands to be sent to the missile piggybacked on the radar signal, an early use of sideband technology. This eliminated the need for a separate antenna for command of the missile.

An electro-analog computer took the inputs from the two radars to calculate an intercept. There was also an analog plotting table that graphed the intercept both for record and to give the officer in charge a better view of it.

One difference is that the S-75 climbed to the target to make the intercept while Nike was flown on a ballistic path (like Talos) to fall on the target from above.

The Russian solution, using two fan beams was a unique on they came up with. The German systems they knew about and suggested systems impressed German engineers suggested postwar were rejected in favor of the homegrown system. These systems were also similar in concept to the Nike system but independently arrived at. With S-25 Berkut, the Russian homegrown system allowed a single set of radars to track multiple targets and missiles. It still required a separate fire control computer for each missile and target pair and that's where that system got expensive as hell. The S-75 was simplified with it handling one target at a time, like Nike.

 

[Dilandu]

A lack of frequency diversity didn't help.

Later model included frequiency-hopping tech; they weren't included in export models, though, AFAIK. Other nation also have this "downgrade" tendency with export technology (for example, "Sea Dart" SAM on Argentinean destroyers lacked home-on-jam circuits...)

This became serious enough in Vietnam that the Russians adopted a television optical guidance system that was semi-manual to back up the radar system. It was more desperation than inspiration.

Erm, it was merely a standard for the time period, when jamming became more a problem. Other nations also started to add electro-optical guidance to SAM's at this time.



See that hole in AN/SPG-60 reflector dish? That's where the camera go.



You could see the camera looking through the hole on top dish.

The US adopted far more sophisticated systems much earlier. Nike Ajax, for example, used the first operational monopulse radar system for guidance.

Yeah, but a bit of problem; Nike-Ajax was single channel for BOTH target & missile. It could engage only one target with only one missile. And it took a lot of time to aquire a new target, since it needed to initiatq new search pattern each time. It didin't make it inefficient, of course, but it was a major limitation, than Nike-Hercules inherited too.

While this reduced the effective range of these systems, they could remain viable in the face of heavy jamming, unlike the S-75 system.

Again, why did you assume that S-75 did not have anti-jamming tech? Early models didn't, because they were, well, early models (early US SAM models also lacked coherent anti-jamming). Later model incoporated such.

S-25 Berkut for example, pretty much ate up every bit of available tube production outside of vital military systems and even made a dent in those. If you can't make enough sophisticated tubes to meet demand...

S-25 would likely be problematic even for US industry to meet demands. This system was order of magnitude more complicated than anything comparable, save of maybe SAGE. It was literally ahead of time - so even USSR itself admitted that & didn't return to the idea of multi-channel SAM till solid chip tech.

The Talos missile system used a Lundberg lens with monopulse (the SPG 49) and a separate guidance radar (SPW-2) that could fly the missile to an intercept without being locked on the target. This made jamming the in-flight radar difficult or impossible and the SPG -49 difficult to jam as it only needed to illuminate the target in the final phase of intercept.

Not that simple. The opponent could jam the AN/SPG-49 pulse tracking beam. If AN/SPG-49 lost the target, the fire control computer won't have any data for AN/SPW-2 to guide the missile, since AN/SPW-2 interception point was calculated by the data from AN/SPG-49. In fact, jamming of Talos was considered to be significant enough problem (due to missile polyrode interferometer array, succeptible to side signals), that there were both anti-jamming mode (missile flied low & climbed to the target, to reduce influence of remote rammers) and home-on-jam mode.

 

[Dilandu]

Okay, about jamming & counter-ECM for S-75:

* First of all, even the basic system (SA-75 "Dvina") have some capability against range jamming. Because two separate channels (for azimuth and elevation) were both tracking the range, jamming one would not deny system of range data of target;

* If no range data for target was available, the system simply switched to CLOS; target was tracked in azimuth and elevation, and missiles were CLOS'ed along the target tracking line, with proximity fuze activated well in advance;

* The proximity fuze was activated only close to target, so it won't have time to actually jam the fuze;

Later models - like S-75 "Volkhov" and S-75M "Desna" - incoprorated additional anti-jamming tech:

* The passive decoys were automatically discriminated by Doppler shift by special circuit in automatic tracking system;

* The background noise filters were introduced against broadband jamming;

* The rapid tracking beam frequency hopping was introduced - separate for both tracking channels - against precise frequency jamming;

The Vietnam War experience demonstrated some vulnerabilities (and you should took into account, that - due to secrecy - only the basic SA-75 "Dvina" systems were used in Vietnam, not the more capable ones), which were remedied:

* The power of missile transponders was increased, to avoid the risk of missile tracking channels being jammed;

* The special filters were introduced on missile tracking channels, to narrow the window for gating the missiles (only signatures moving in specific directions with specific speed would be gated);

* The imitation "false launch" mode was introduced, when all electronic equipment worked as during real launch - but without actually launching the missile. The idea was to provoke target into maneuvering and implementing ECM's on detected frequences - after wich the radar just shifted to other frequency, and made a REAL launch before target could realize that it was duped;

 

[T. A. Gardner]

Later model included frequiency-hopping tech; they weren't included in export models, though, AFAIK. Other nation also have this "downgrade" tendency with export technology (for example, "Sea Dart" SAM on Argentinean destroyers lacked home-on-jam circuits...)

That's not what I'm saying. Frequency diversity is important. It means some radars don't get jammed while others might. Having to cover a broad spectrum of frequencies makes jamming more difficult. Frequency hopping is something else.

Erm, it was merely a standard for the time period, when jamming became more a problem. Other nations also started to add electro-optical guidance to SAM's at this time.

View attachment 795321

See that hole in AN/SPG-60 reflector dish? That's where the camera go.

View attachment 795322

You could see the camera looking through the hole on top dish.

Electro-optical systems have been around since WW 2. That, again, isn't the point. If you have a system that is largely automatic--that is, the optic is kept on target and once locked on everything is automatic, that's a far cry from a system using largely manual tracking system.

Yeah, but a bit of problem; Nike-Ajax was single channel for BOTH target & missile. It could engage only one target with only one missile. And it took a lot of time to aquire a new target, since it needed to initiatq new search pattern each time. It didin't make it inefficient, of course, but it was a major limitation, than Nike-Hercules inherited too.

So were virtually all SAM systems up through the 90's. However, the engagement time from one target to the next was minimal as the LOPAR search radar could already have the next target lined up, and with Missile Master added, it was possible for targets to be assigned remotely from other launch batteries. The limitation was one target per battery at a time, not the time from one target to the next.

Again, why did you assume that S-75 did not have anti-jamming tech? Early models didn't, because they were, well, early models (early US SAM models also lacked coherent anti-jamming). Later model incoporated such.

It did, but because the radar system used largely dated technology for beam forming it proved highly vulnerable to jamming. Early US SAMs did incorporate both passive and active anti-jamming features including Nike, Talos, and Terrier. HAWK also had such features.

S-25 would likely be problematic even for US industry to meet demands. This system was order of magnitude more complicated than anything comparable, save of maybe SAGE. It was literally ahead of time - so even USSR itself admitted that & didn't return to the idea of multi-channel SAM till solid chip tech.

S-25 was something impossible for the West to build in peacetime. The one system built consumed about 10% of Russia's GDP at the time. Yes, it was grotesquely expensive. That's why it wasn't duplicated. That cost led to looking at alternatives and as it became apparent that a 1000 bomber raid was not the future, the need for it disappeared.

Not that simple. The opponent could jam the AN/SPG-49 pulse tracking beam. If AN/SPG-49 lost the target, the fire control computer won't have any data for AN/SPW-2 to guide the missile, since AN/SPW-2 interception point was calculated by the data from AN/SPG-49. In fact, jamming of Talos was considered to be significant enough problem (due to missile polyrode interferometer array, succeptible to side signals), that there were both anti-jamming mode (missile flied low & climbed to the target, to reduce influence of remote rammers) and home-on-jam mode.

This is incorrect. The 3D search radar, typically an SPS-30, provided the data needed for the SPW-2 to guide the missile close to the target. The SPS 49 only had to switch on and paint the target in the terminal phase of intercept. In any case, the SPS 49 was continuous wave when painting the target as Talos used an interferometer for guidance terminally, not semi-active homing.

The Mk 111 computer followed progress of the missile with signals from the SPW-2 guidance radar. When the missile neared the target the computer switched on the illumination transmitter for the AN/SPG-49. The computer calculated the Doppler shift due to the relative motion between the target and the ship, and also calculated the Doppler shift between the missile and target. It computed the resulting frequency of the radar echo from the target to the missile. This information was encoded in the illumination signal from the AN/SPG-49. This caused the missile to home in on only that specific frequency, making it impossible to jam the missile. In fact, the missile scored higher success rates against jamming targets than for targets that weren't trying to jam it!

SPG-49 Tracking Radar

 

[Dilandu]

That's not what I'm saying. Frequency diversity is important. It means some radars don't get jammed while others might. Having to cover a broad spectrum of frequencies makes jamming more difficult. Frequency hopping is something else.

The cotemporary Western systems weren't good in that matter also. The limitations of vacuum tube electronics were too great.

Electro-optical systems have been around since WW 2. That, again, isn't the point. If you have a system that is largely automatic--that is, the optic is kept on target and once locked on everything is automatic, that's a far cry from a system using largely manual tracking system.

So what's your point? You are claiming that electro-optical system on S-75 was "act of desperation", then immediately claim that it isn't on Western systems. Clarify, please.

So were virtually all SAM systems up through the 90's. However, the engagement time from one target to the next was minimal as the LOPAR search radar could already have the next target lined up, and with Missile Master added, it was possible for targets to be assigned remotely from other launch batteries. The limitation was one target per battery at a time, not the time from one target to the next.

Except Soviet ones, I should remind you.

It did, but because the radar system used largely dated technology for beam forming it proved highly vulnerable to jamming. Early US SAMs did incorporate both passive and active anti-jamming features including Nike, Talos, and Terrier. HAWK also had such features.

You realize that Talos, for example, used the same rotating scanner for beam forming of AN/SPG-59?

In any case, the SPS 49 was continuous wave when painting the target as Talos used an interferometer for guidance terminally, not semi-active homing.

One note - the early Talos models were pulse-only. Granted, the CW illumination system was introduced quite early - but not immediately.

 

[Dilandu]

One point that I'd like to empathise: I do not claim superiority of Soviet system. What I wanted to demonstrate was its ingenuity. And original - quite elegant - solutions used in it.

 

[T-80U_Valodyana]

是，也不是。它们仍然只是使用锥形扫描的脉冲雷达。基本上，当时的苏联人仍然主要沿用二战时期西方的技术，例如SCR 584雷达。多普勒效应有助于抵御箔条干扰，但基本的扫描方式使得噪声干扰、测距干扰和角度门控干扰都相对容易。

In fact, mainlobe noise jamming is effective against any radar. As LPRF radars, the RSNA-75(1957) series features PRF agility, which severely weakens the effect of range deception jamming. Starting from the RSN-75M(1959-1964 around) radar, it gained a certain frequency modulation capability to counter narrowband jamming,Starting from the RSN-75M3(1975), it possesses a practical pre-programmed pulse group frequency agility capability to counter spot jamming,and also acquired the GshV circuit to counter angle jamming and sidelobe jamming.

美国更早地采用了更为先进的系统。例如，耐克阿贾克斯导弹系统就使用了首个投入使用的单脉冲雷达制导系统。与其配套的雷达，以及后来的霍克导弹系统，都具有极高的频率分集，这使得干扰更加困难。

The MIM-3 (1953) missile system, serving as the last line of defense against bombers, was actually benchmarked against Moscow’s S-25 (1955) system rather than the mobile S-75. Although the MIM-3 was indeed the first to adopt the monopulse angle measurement method, it long suffered from limited angle measurement accuracy and could not distinguish a single bomber from a formation. The S-25, however, was not troubled by this issue.Actually, this is a small advantage of TWS radar.

The HAWK (1959) and I-HAWK (1971) are believed to lack “true” frequency agility and both use conical scanning. In fact, due to the pure semi-active guidance mode, the HAWK becomes even less usable when encountering inverse gain jamming, whereas the SA-75M (1969, with its actual technical level dating to around 1957, merely utilizing better missiles) at least has an optical channel.

塔洛斯导弹系统使用了一个带有单脉冲的伦德伯格透镜（SPG 49）和一个独立的制导雷达（SPW-2），该雷达可以在不锁定目标的情况下引导导弹进行拦截。这使得干扰飞行中的雷达变得困难甚至不可能，而且SPG-49本身也很难被干扰，因为它只需要在拦截的最后阶段照射目标即可。

The Talos system (1958) is indeed impressive, but please note that its sheer size and cost are unimaginable. Compared to the larger and heavier Soviet S-200 (1966), its advantages are not significant.

111计算机利用SPW-2制导雷达的信号跟踪导弹的飞行轨迹。当导弹接近目标时，计算机开启AN/SPG-49的照射发射器。计算机计算目标与舰艇之间相对运动产生的多普勒频移，以及导弹与目标之间的多普勒频移。它计算出从目标到导弹的雷达回波频率。这些信息被编码到AN/SPG-49的照射信号中。这使得导弹只能追踪该特定频率，从而无法被干扰。事实上，该导弹对干扰目标的成功率比对非干扰目标的成功率更高！

Its missile employs phase-comparison continuous wave angle measurement, which can be regarded as a variant of monopulse angle measurement—a truly impressive feature. For anti-jamming, it uses a narrowband filter with a width of approximately 100 Hz and employs a method resembling the later "inverse monopulse angle measurement" technique. This proves effective against sea clutter and simple noise jamming. However, it cannot counter chaff with Doppler frequency spread characteristics or DRFM jammers developed decades later. Moreover, I have found no conclusive evidence that it possesses a HOJ (Home-On-Jam) mode.

 

[T-80U_Valodyana]

Due to the presence of the webpage's built-in translator, my quotes have turned into Chinese, and I apologize for that.

 

[T-80U_Valodyana]

The later modes - S-75 "Desna" and S-75M "Volkhov" - generally used the same radar set, but with improved functionality. Since S-75M "Volkhov" have much longer range than basic SA-75, its usual wide-beam scanning mode was not sufficient anymore; on long distances, the target data become too inaccurate.

The narrow beam mode serves two purposes: reducing the radar's exposure to SEAD platforms, and increasing radiated power to counter the new "dirty bird" low-reflectivity coating emerging in the United States, as well as other small cross-section weapons. In fact, since the wavelength remains unchanged, there seems to be no reason to believe that using an early radar at long ranges would result in lower accuracy.

* If no range data for target was available, the system simply switched to CLOS; target was tracked in azimuth and elevation, and missiles were CLOS'ed along the target tracking line, with proximity fuze activated well in advance;

* The proximity fuze was activated only close to target, so it won't have time to actually jam the fuze;

This circuit, known as the I-87V circuit, uses trigonometric methods and high-power altimetry radars from other sites (or any other means to obtain target altitude) to activate the fuze several kilometers before the expected target position. It appeared only on certain versions of the S-75 series, not on the SA-75 series.

Meanwhile, the S-75 also featured a switch called "Rab ot BM" – a switch flipped after launch to immediately activate the radio fuze. On systems without the I-87V, missiles engaging noise-jamming targets lacking range information would use this switch. However, the systems supplied to Vietnam only had the Rab ot VM – a switch flipped before launch, which disarmed the radio fuze safety 11 seconds after launch.

During the Vietnam War, a large number of V-755 missiles were wasted in the chaff corridors deployed by F-4 fighters, failing to hit B-52 bombers, due to the absence of the I-87V and the BM switch.

In normal guidance mode, the proximity fuze release insurance at a distance of 300-500 meters from the target.

* The imitation "false launch" mode was introduced, when all electronic equipment worked as during real launch - but without actually launching the missile. The idea was to provoke target into maneuvering and implementing ECM's on detected frequences - after wich the radar just shifted to other frequency, and made a REAL launch before target could realize that it was duped;

To the best of my knowledge, most versions of the S-75 also have this mode, which is used to intimidate enemy aircraft, especially tactical aircraft, causing them to abandon their ground attack missions.

 

[T-80U_Valodyana]

and you should took into account, that - due to secrecy - only the basic SA-75 "Dvina" systems were used in Vietnam, not the more capable ones

The Soviet Union was afraid that China would intercept military aid trains and obtain more advanced S-75M systems, so they chose to assist Vietnam with the older SA-75M system. And other socialist sister countries have basically obtained the updated S-75 system.
The export of S-75 to non socialist countries was also later, but it began exporting to these non socialist countries around 1970

 

[Dilandu]

Due to the presence of the webpage's built-in translator, my quotes have turned into Chinese, and I apologize for that.

No problem, everything is understandable.

 

[T. A. Gardner]

In fact, mainlobe noise jamming is effective against any radar. As LPRF radars, the RSNA-75(1957) series features PRF agility, which severely weakens the effect of range deception jamming. Starting from the RSN-75M(1959-1964 around) radar, it gained a certain frequency modulation capability to counter narrowband jamming,Starting from the RSN-75M3(1975), it possesses a practical pre-programmed pulse group frequency agility capability to counter spot jamming,and also acquired the GshV circuit to counter angle jamming and sidelobe jamming.

The MIM-3 (1953) missile system, serving as the last line of defense against bombers, was actually benchmarked against Moscow’s S-25 (1955) system rather than the mobile S-75. Although the MIM-3 was indeed the first to adopt the monopulse angle measurement method, it long suffered from limited angle measurement accuracy and could not distinguish a single bomber from a formation. The S-25, however, was not troubled by this issue.Actually, this is a small advantage of TWS radar.

The HAWK (1959) and I-HAWK (1971) are believed to lack “true” frequency agility and both use conical scanning. In fact, due to the pure semi-active guidance mode, the HAWK becomes even less usable when encountering inverse gain jamming, whereas the SA-75M (1969, with its actual technical level dating to around 1957, merely utilizing better missiles) at least has an optical channel.

The Talos system (1958) is indeed impressive, but please note that its sheer size and cost are unimaginable. Compared to the larger and heavier Soviet S-200 (1966), its advantages are not significant.

Its missile employs phase-comparison continuous wave angle measurement, which can be regarded as a variant of monopulse angle measurement—a truly impressive feature. For anti-jamming, it uses a narrowband filter with a width of approximately 100 Hz and employs a method resembling the later "inverse monopulse angle measurement" technique. This proves effective against sea clutter and simple noise jamming. However, it cannot counter chaff with Doppler frequency spread characteristics or DRFM jammers developed decades later. Moreover, I have found no conclusive evidence that it possesses a HOJ (Home-On-Jam) mode.

Note: HAWK radars use pulse and continuous wave operation, not conical scan. The various radars also operate on diverse frequencies to make jamming of everything harder. HAWK was a beam rider as far as the guidance went (Homing All the Way Killer).

With Nike, the radars used were more than adequate and accurate for use with Ajax as this had a 25-to-30-mile practical intercept range. When Hercules was introduced, initially it was limited to the same range but had a built-in option that would allow it to be extended to 50 NM range. Against a formation of bombers, versus one, it didn't really matter if the resolution was insufficient to pick out individual targets. The aim point was the center of the formation, and a nuclear warhead would have been used. That was the whole point of Hercules. It was, from inception, to be a nuclear armed version of Nike.

S-25 and S-75 are more akin to the Nike system as medium to high altitude SAMs. HAWK is more like Thunderbird or Swiss RSA to D SAMs in conception. That is, it is for use at shorter ranges against low to medium altitude targets.

As for Talos:

Talos Mk 77 Missile Fire Control System

Talos also had a Home-On-Jam mode.

Home On Jamming​

The CW homing receiver had several characteristics that made it less susceptible to countermeasures. The narrowband seeker rejected most jamming frequencies. The short 6 to 10 second homing period gave little time for countermeasure equipment to respond. The signal tracking method in the STAPFUS seeker was not sensitive to signal amplitude. The homing system could discriminate between multiple jammers and home on the strongest received signal. However there were some jamming techniques that would work against it. A new "monopulse" seeker was designed to precondition the interferometer to reject jamming interference before the signals were passed to the STAPFUS seeker, and a faster method of tuning to the search frequency was added. The resulting seeker was immune to virtually any type of jamming.

After extensive laboratory testing the new seeker was flight tested against a variety of jamming targets. 25 of the initial 26 tests were successful with many direct hits. Test results showed that the new seeker had a higher probability of kill against a jamming target than against a non-jamming target. In essence a jammer broadcast a "here I am, come and get me" signal that Talos couldn't miss.

Additional home on jamming improvements for the Talos seeker were devised but were never implemented because the phaseout of Talos was planned.

Talos Missile Guidance and Homing History

 

[T-80U_Valodyana]

Home On Jamming​

The CW homing receiver had several characteristics that made it less susceptible to countermeasures. The narrowband seeker rejected most jamming frequencies. The short 6 to 10 second homing period gave little time for countermeasure equipment to respond. The signal tracking method in the STAPFUS seeker was not sensitive to signal amplitude. The homing system could discriminate between multiple jammers and home on the strongest received signal. However there were some jamming techniques that would work against it. A new "monopulse" seeker was designed to precondition the interferometer to reject jamming interference before the signals were passed to the STAPFUS seeker, and a faster method of tuning to the search frequency was added. The resulting seeker was immune to virtually any type of jamming.

After extensive laboratory testing the new seeker was flight tested against a variety of jamming targets. 25 of the initial 26 tests were successful with many direct hits. Test results showed that the new seeker had a higher probability of kill against a jamming target than against a non-jamming target. In essence a jammer broadcast a "here I am, come and get me" signal that Talos couldn't miss.

Additional home on jamming improvements for the Talos seeker were devised but were never implemented because the phaseout of Talos was planned.

This article conceals an unstated element, namely that the continuous wave phase-comparison angle-measuring guidance system lacked HOJ capability for a certain unknown period—since HOJ angle measurement against noise jamming targets must employ amplitude comparison rather than phase comparison—and was later improved, which actually partially aligns with my judgment.

The signal tracking method in the STAPFUS seeker was not sensitive to signal amplitude.

*this

Note: HAWK radars use pulse and continuous wave operation, not conical scan. The various radars also operate on diverse frequencies to make jamming of everything harder. HAWK was a beam rider as far as the guidance went (Homing All the Way Killer).

Considering the low hit probability of the MIM-23A [Tony Cullen and Christopher F. Foss (Eds), *Jane's Land-Based Air Defence Ninth Edition 1996–97*, p. 296, Coulsdon: Jane's Information Group, 1996] and the fact that other literature additionally mentions the replacement of the seeker with an X-band monopulse seeker in the MIM-23B, I am convinced that the MIM-23A missile most likely employed the conical scan angle measurement method, which was only improved upon in the MIM-23B. In fact, the conical scan method suffers from decreasing accuracy at shorter ranges and has an inherent time delay in angle measurement, which aligns with the less-than-expected hit performance of the MIM-23A.

S-25 and S-75 are more akin to the Nike system as medium to high altitude SAMs. HAWK is more like Thunderbird or Swiss RSA to D SAMs in conception. That is, it is for use at shorter ranges against low to medium altitude targets.

The S-75 system explicitly added a moving target indication function in a certain version (possibly the S-75V) and improved fuze sensitivity (300 meters, 100 meters, and command detonation). Its capability to engage low-altitude targets may be comparable to that of the Hawk.
Due to the issue with its radar scanning method [having a minimum scanning angle], the S-25 indeed struggles to deal with ultra-low altitude targets.

 

[NMaude]

HAWK was a beam rider as far as the guidance went (Homing All the Way Killer).

The MIM-23 was never a beam-rider, it used a semi-active radar seeker.

 

[Dilandu]

S-25 and S-75 are more akin to the Nike system as medium to high altitude SAMs.

Functionally - yes. Technically, the S-25 have literally no analogue till 1980s (multi-channel SAM's capable of dozens spontaneous interceptions were too much a challenge for available technology - even USSR decided NOT to repeat the S-25 due to extravagant cost of the system!) and S-75 was more mobile and tactically capable than Nike (at the cost of lesser range, of course).

 

[Dilandu]

. HAWK was a beam rider as far as the guidance went (Homing All the Way Killer).

Erm, no. It was a semi-active homing missile, not a beam-rider. It homed on the reflected radar echo from target; it did not follow the radar beam direction.

 

[T. A. Gardner]

Functionally - yes. Technically, the S-25 have literally no analogue till 1980s (multi-channel SAM's capable of dozens spontaneous interceptions were too much a challenge for available technology - even USSR decided NOT to repeat the S-25 due to extravagant cost of the system!) and S-75 was more mobile and tactically capable than Nike (at the cost of lesser range, of course).

Not really. The only unique part of the system is the radar. The two rotating 'triangles' are a continuous scan set. One scans vertically, the other horizontally. This gives an X, Y set of coordinates for each target and missile fired. Those are fed into one of 20 sets of computers that feed the firing and target data to a console that handles up to 4 targets. Each missile fired had a separate command guidance radio link from the ground controlling it. These signals were put out through one of 5 transmitters in a shallow revetment in front of the control bunker and ahead of the radars.

As there were 5 control consoles, a firing regiment could have up to 20 targets selected and being fired on simultaneously.

The system is unique in terms of the target detection and tracking, but the fire controls are nothing different from other SAM systems of the period. It was all necessary to meet Stalin's demand for a system capable of stopping a 1000 bomber raid of the WW 2 type.

One of the biggest drawbacks to S-25 was that each firing regiment had a fixed field of fire facing outward.

Once you have a small nuclear warhead, any grouped formation of aircraft is vulnerable to being shot down by a single missile so the massed fires of the S-25 were no longer needed. Even the S-25 got a nuclear version eventually.

 

[NMaude]

The S-25 I assume refers to the SA-1 Guild?

 

[T. A. Gardner]

The S-25 I assume refers to the SA-1 Guild?

S-25 is the Russian designation. It was Berkut (Golden Eagle) initially until Stalin died. After his death, the new 'management' so-to-speak wanted to eliminate anything Stalin they could and the designation was changed to S-25.

Here's an interesting site on this system:

Official Illustrated Guide Moscow Anti-Aircraft Defense System 1955

www.allworldwars.com

 

[P-STICKNEY]

Note: HAWK radars use pulse and continuous wave operation, not conical scan. The various radars also operate on diverse frequencies to make jamming of everything harder. HAWK was a beam rider as far as the guidance went (Homing All the Way Killer).

With Nike, the radars used were more than adequate and accurate for use with Ajax as this had a 25-to-30-mile practical intercept range. When Hercules was introduced, initially it was limited to the same range but had a built-in option that would allow it to be extended to 50 NM range. Against a formation of bombers, versus one, it didn't really matter if the resolution was insufficient to pick out individual targets. The aim point was the center of the formation, and a nuclear warhead would have been used. That was the whole point of Hercules. It was, from inception, to be a nuclear armed version of Nike.

S-25 and S-75 are more akin to the Nike system as medium to high altitude SAMs. HAWK is more like Thunderbird or Swiss RSA to D SAMs in conception. That is, it is for use at shorter ranges against low to medium altitude targets.

As for Talos:

Talos Mk 77 Missile Fire Control System

Talos also had a Home-On-Jam mode.

Home On Jamming​

The CW homing receiver had several characteristics that made it less susceptible to countermeasures. The narrowband seeker rejected most jamming frequencies. The short 6 to 10 second homing period gave little time for countermeasure equipment to respond. The signal tracking method in the STAPFUS seeker was not sensitive to signal amplitude. The homing system could discriminate between multiple jammers and home on the strongest received signal. However there were some jamming techniques that would work against it. A new "monopulse" seeker was designed to precondition the interferometer to reject jamming interference before the signals were passed to the STAPFUS seeker, and a faster method of tuning to the search frequency was added. The resulting seeker was immune to virtually any type of jamming.

After extensive laboratory testing the new seeker was flight tested against a variety of jamming targets. 25 of the initial 26 tests were successful with many direct hits. Test results showed that the new seeker had a higher probability of kill against a jamming target than against a non-jamming target. In essence a jammer broadcast a "here I am, come and get me" signal that Talos couldn't miss.

Additional home on jamming improvements for the Talos seeker were devised but were never implemented because the phaseout of Talos was planned.

Talos Missile Guidance and Homing History

Hawks were always Semi-Active. The seeker was derived from the contemporary AIM-7 seeker. There were no Command or Beam-Rider modes - the seeker locked on while the missile was on the rail, and that took it all the way to the target. (Hence Homing All the Way).

 

[Dilandu]

One of the biggest drawbacks to S-25 was that each firing regiment had a fixed field of fire facing outward.

Believe me, I knew all that) I'm a bit puzzled about your "not really", because your post basically elaborate on mine - unique system, but far too costly for mass production.

 

[T. A. Gardner]

Believe me, I knew all that) I'm a bit puzzled about your "not really", because your post basically elaborate on mine - unique system, but far too costly for mass production.

The only part of the guidance system that was unique was the radar. The rest of it was based off designs the Germans had produced during WW 2. In fact, it was a German engineer that had been sent to NII 88 and later transferred to KB 1 that did most of the design on it. The radar and its workings were wholly Russian, and the engineers involved had a hard time convincing Sergey Beria to adopt it as he was fixated on the Germans knowing the electronics.

 

[Dilandu]

The only part of the guidance system that was unique was the radar. The rest of it was based off designs the Germans had produced during WW 2. In fact, it was a German engineer that had been sent to NII 88 and later transferred to KB 1 that did most of the design on it. The radar and its workings were wholly Russian, and the engineers involved had a hard time convincing Sergey Beria to adopt it as he was fixated on the Germans knowing the electronics.

Not exactly correct. The S-25 system was not based on any kind of German designs at all. Its development was initiated exactly because it was realized that R-101 (derivative of German Wasserfal) is a dead end, and a completely new system is required. While German specialists worked on S-25 project, they were only allowed to work with theoretical and mathematical parts, and have only limited access to hardware.

 

[T. A. Gardner]

Not exactly correct. The S-25 system was not based on any kind of German designs at all. Its development was initiated exactly because it was realized that R-101 (derivative of German Wasserfal) is a dead end, and a completely new system is required. While German specialists worked on S-25 project, they were only allowed to work with theoretical and mathematical parts, and have only limited access to hardware.

The Germans did have indirect and direct influence on the S-25 system. The engine for the V-300 (ZUR 205) missile was a direct descendent of the P IX Wasserfall engine. The original German engine copied, with some minor improvements was the SO8.01 in Russian usage. Alexei M Isaev at NII 88 used that starting point to develop the TG-02 engine the ZUR 205 used. The fuel remained RFNA and a modified mix of German Tonka 250.

In guidance, German engineers taken to the Soviet Union played a critical role. Johannes Hoch was a key figure in the development of the autopilot for the ZUR 205. Kurt Magnus developed an integrating gyroscope that was critical for flight control of the missile. Hoch also developed a PID control system that allowed tracking of the target and missile relative to each other without need for an outside reference point. That allowed the B-200 radar system and associated guidance system to use a single tracking radar for both the missile and target.

The radio control system used was derived from wartime German designs for use with Bergund and Elass. The end system had a lot of Russian input, particularly from TsNII-108 but was still derived from captured German technology. The A-100 early warning and surveillance radars were derived from US and British Lend-Lease technology.

On the other hand, Alexander A Raspletin at KB-1 came up with the idea for the B-200 tracking radars. These were uniquely Russian in design and owed nothing to foreign technology. That design has not been copied since, largely due to the fixed field of scan those radars had which worked well with the S-25 system.

Interestingly, D L Tomashevich head of Section 32 at KB-1 came up with an alternative missile for use with the S-25 system, the 32-B. This used no directly derived German technology in its design and was a two-stage missile with a solid fuel booster. In testing in 1953 - 54, it proved superior to the ZUR 205. But it was turned down for use in the S-25 system because the ZUR 205 was already too far advanced in the design process to change over everything to accommodate the 32-B. Instead, this became the basis for the S-75 Diva (SA-2)

 

[xena]

Just because German engineers were involved does not mean that the technology originated in the Second World War. After all, the engineers did not stop in 1945. They certainly continued to develop their technology and expertise, building on the knowledge they had acquired in the 1940s, from which the whole world, including the USA, benefited. Everyone learnt from the Germans, including the US and the Russians. If German engineers developed parts of the S-25, they did so using the knowledge they had further developed, not the knowledge from 1945. And the Russians benefited from this exchange of knowledge; indeed, this knowledge was expanded with the help of the Russians.

 

[T. A. Gardner]

Just because German engineers were involved does not mean that the technology originated in the Second World War. After all, the engineers did not stop in 1945. They certainly continued to develop their technology and expertise, building on the knowledge they had acquired in the 1940s, from which the whole world, including the USA, benefited. Everyone learnt from the Germans, including the US and the Russians. If German engineers developed parts of the S-25, they did so using the knowledge they had further developed, not the knowledge from 1945. And the Russians benefited from this exchange of knowledge; indeed, this knowledge was expanded with the help of the Russians.

No, it doesn't. Some of it was post war, and what was WW 2 in origin was always improved upon repeatedly. The SO8.01 engine started off as a direct copy of the German Wasserfall P IX, and then improved. New throttling allowed for more efficient power levels giving longer run time and the missile greater range. The combustion chamber was modified several times, before an ideal one was found as an example. The Russians and French, both being in a position of catch up due to the war and inability to do lots of R&D, milked the Germans and their technology as much as they could but by 1950 it was apparent that had run its course and had little left to offer. Sure, getting some German engineers stretched resources, but it wasn't a panacea either.

The one piece of gear I would say was universally copied or used as a starting point was the US SCR 584 radar. The British copied it. The French copied it. The Russians copied it. In 1945, it was the world standard for fire control radars, and everybody knew it. I'm not trying to be all rah rah about the US here, but that one piece of equipment was simply a tour de force in radar at the time.

There were contemporaries that simply weren't as good, like the SCR 525 or British GL Mk III. The British caught up with the post war Radar AA No. 3 Mk 7, aka Blue Cedar introduced in 1952.

 

[T. A. Gardner]

Functionally - yes. Technically, the S-25 have literally no analogue till 1980s (multi-channel SAM's capable of dozens spontaneous interceptions were too much a challenge for available technology - even USSR decided NOT to repeat the S-25 due to extravagant cost of the system!) and S-75 was more mobile and tactically capable than Nike (at the cost of lesser range, of course).

No, it was rather a case of cost or in other cases complexity. Nike was that way for example. The system handled one target at a time which was considered sufficient when you have nuclear weapons for mass formations. Talos and Terrier were limited to two targets at a time per launcher on a ship due mainly to space and weight requirements. Land based Talos, considered for a short while by the US Army, could handle 4 targets per battery simultaneously.

The S-25 cost the Soviet Union something like 10% of their GDP over its development and deployment life. That's an insane level of spending for a single SAM system. Once the Soviets had nuclear weapons, they could do what the US was doing. That is, firing a single nuclear armed missile to take down a whole formation of planes at once. No need for dozens upon dozens of missiles going after individual targets.

The S-75 was, I think, what the US Army initially envisioned as Nike. Nike evolved into a semi-static system simply because of cost plus intended use (defense of the continental US).

 

[Dilandu]

No, it was rather a case of cost or in other cases complexity. Nike was that way for example. The system handled one target at a time which was considered sufficient when you have nuclear weapons for mass formations.

One target with one missile. Which... wasn't good idea, considering the problematic reliability of 1950s missiles. S-75, for compairson, have three missile channels - i.e. could fire three missiles simultaneously against the single target.

 

[T. A. Gardner]

One target with one missile. Which... wasn't good idea, considering the problematic reliability of 1950s missiles. S-75, for compairson, have three missile channels - i.e. could fire three missiles simultaneously against the single target.

It was for what was expected. The original intent of Nike was to replace a battery of heavy AA guns with a missile battery. Either could engage one target at a time. The system was to maximize extant technology, not cutting edge or stuff that was proposed in the future. For that, Nike Ajax was exactly what was ordered.

The USAF contemporary GAPA SAM program showed what happens when you ask for too much and want to push the envelope.

With Nike, multiple batteries engaging a target was possible. That's why the Army developed Missile Master to go with that system. In the long run, Missile Master and the Air Force's SAGE were better investments. SAGE, like the S-25 system, was ungodly expensive. The figures I've seen say it was something like 10 Manhattan Projects in cost over its lifetime.

 

[Dilandu]

It was for what was expected. The original intent of Nike was to replace a battery of heavy AA guns with a missile battery. Either could engage one target at a time. The system was to maximize extant technology, not cutting edge or stuff that was proposed in the future. For that, Nike Ajax was exactly what was ordered.

The USAF contemporary GAPA SAM program showed what happens when you ask for too much and want to push the envelope.

With Nike, multiple batteries engaging a target was possible. That's why the Army developed Missile Master to go with that system. In the long run, Missile Master and the Air Force's SAGE were better investments. SAGE, like the S-25 system, was ungodly expensive. The figures I've seen say it was something like 10 Manhattan Projects in cost over its lifetime.

Yeah, but engaging one target with one missile - which wasn't exactly even remotely close to 100% efficient - was just not reliable. If the first missile failed to knock down the target, the second could be launched only after the first one detonated. Considering the limited range of Nike Ajax, there was a serious danger that enemy bomber could cross the engagement area before battery would manage to shoot it down. There, Soviet experience with multi-channel S-25 gave USSR actual advantage; S-75 could control up to three missiles against single target, greatly increasing interception probability.

 

[T. A. Gardner]

Yeah, but engaging one target with one missile - which wasn't exactly even remotely close to 100% efficient - was just not reliable. If the first missile failed to knock down the target, the second could be launched only after the first one detonated. Considering the limited range of Nike Ajax, there was a serious danger that enemy bomber could cross the engagement area before battery would manage to shoot it down. There, Soviet experience with multi-channel S-25 gave USSR actual advantage; S-75 could control up to three missiles against single target, greatly increasing interception probability.

At the time (mid- to late-50's) reliability was an issue for everyone with SAM systems. The use of tubes and what the state-of-the-art was in electronics, pretty much ensured it. Tubes were unreliable. Capacitors were prone to losing their capacitance. This was a major problem for every nation.

The US had this issue with every one of their SAM systems. All of them got dedicated "get well" programs intended to improve reliability. One way that happened was replacing tubes with solid state components ASAP. The introduction of circuit boards instead of point-to-point soldered wiring helped immensely.

 

[Dilandu]

At the time (mid- to late-50's) reliability was an issue for everyone with SAM systems. The use of tubes and what the state-of-the-art was in electronics, pretty much ensured it. Tubes were unreliable. Capacitors were prone to losing their capacitance. This was a major problem for every nation.

Yep. That's why most SAM system designers assumed that more than one missile should be launched against each target to ensure acceptable chance of hitting it.

 

[xena]

Yes, but the technology wasn’t advanced enough back then to use multiple independent guided missiles against a single target. You needed a tracking radar for every single target and every single missile. It was, after all, the early stages of development. So we shouldn’t be too harsh on it.

 

[T. A. Gardner]

Yep. That's why most SAM system designers assumed that more than one missile should be launched against each target to ensure acceptable chance of hitting it.

The US Army found that it was more important that each firing battery not duplicate effort and engage the same target while ignoring others. That's why they put their efforts into Missile Master. Both SAGE and Missile Master, which became linked fairly early on, allowed a nationwide coordination of air defenses, SAMs, interceptors, etc., to occur. This was considered far more important and valuable than a SAM battery being able to engage multiple targets simultaneously.

The other thing the US did with early Nike was build defense in depth for the most valuable targets. That is, they had SAM batteries placed where they could engage targets and those that leaked through the first set would be engaged by a second, etc.

 

[Dilandu]

The US Army found that it was more important that each firing battery not duplicate effort and engage the same target while ignoring others. That's why they put their efforts into Missile Master. Both SAGE and Missile Master, which became linked fairly early on, allowed a nationwide coordination of air defenses, SAMs, interceptors, etc., to occur. This was considered far more important and valuable than a SAM battery being able to engage multiple targets simultaneously.

You misunderstood me again. The major problem of Nike wasn't that it have single target channel; it's major problem was a single missile channel. At any given time, no more than one missile could be in air, because fire control system have only one missile tracking radar. The second missile could not be launched before the first one exploded. And since hit probability for Nike wasn't exactly 0.9, this was a major disadvantage for Nike Ajax. The battery crew was forced to fire one missile, wait till it exploded, determine the outcome & if target wasn't destroyed, then fire a second one. Not efficient.

Other cotemporary SAM's did not have such limitations at all. The S-75 have three missile control channels; up to three missiles could be fired against one target simultaneously. And Bristol Bloodhound could fire any number of missiles against single target, due to being semi-active homing. The Nike single-missile channel limitation was unique for this system.

 

[NMaude]

Other cotemporary SAM's did not have such limitations at all. The S-75 have three missile control channels; up to three missiles could be fired against one target simultaneously. And Bristol Bloodhound could fire any number of missiles against single target, due to being semi-active homing. The Nike single-missile channel limitation was unique for this system.

It makes one wonder why the US Army didn't develop a terminal homing seeker for the Nike Hercules.

 

[T. A. Gardner]

Yeah, but engaging one target with one missile - which wasn't exactly even remotely close to 100% efficient - was just not reliable. If the first missile failed to knock down the target, the second could be launched only after the first one detonated. Considering the limited range of Nike Ajax, there was a serious danger that enemy bomber could cross the engagement area before battery would manage to shoot it down. There, Soviet experience with multi-channel S-25 gave USSR actual advantage; S-75 could control up to three missiles against single target, greatly increasing interception probability.

I would rate Nike Ajax at around 75% to 85% efficient against a subsonic bomber in level flight. That was its intended target. I'd say the S-75 was about the same. Against a target that was heavily jamming the guidance, either would fall to around 5 to 10% effectiveness at most. In terms of reliability, that really depends on the crew and parts availability. I'd say based on general historical levels of those that the US would have at least some missiles ready to fire that were fully reliable in terms of testing and such and that the fire controls would be in working order. This would be because the US was working with crews that were mostly long-term veteran servicemen and gave far more annual in service training with live fires than the Soviets did.

With the Soviets using almost all short-term conscript manpower and often iffy supply availability they would still have one or two missiles that worked in a battery and the fire controls likely would work. Their problem would be compounded by poor levels of training and a general lack of live fire practice.

It makes one wonder why the US Army didn't develop a terminal homing seeker for the Nike Hercules.

The difference overall would be the US would have somewhere around 75% reliable, working missiles and systems while the Soviets would be down around 50% or less.

I'd say it's because Nike Hercules was only in limited use and in its later years mostly as a substitute ABM system. There was no real threat from a Soviet bomber force to counter so that sort of precision wasn't necessary. With a nuclear warhead (ABM role), command detonation was a legal requirement Congress set on such systems. The control had to be positive and continuous from launch to intercept.

 

[Dilandu]

It makes one wonder why the US Army didn't develop a terminal homing seeker for the Nike Hercules.

Mostly because they viewed it as nuclear SAM first and foremost - and nuclear SAM did not require homing to be efficient. Also, because command-guided missiles were significantly cheaper than homing ones.