3R41 Volna Design Question.

stealthflanker

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So yeah, one part of the story of the S-300P SAM's was that it was standardized for Navy and PVO low altitude target Requirements. The story then continues with assignments of design bureaus where Almaz proceeded with ground based variant while the naval variant fell into the hand of Antey and Altair. Antey develops probably the radar while Altair develops the seeker. Both systems use standard 5V55 missiles (The naval variant tho is designated as 5V55RM).

Here is the curious question. has anybody wonder on why 3R41 Volna greatly differs to the 5N63 family ?

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As one can see the 3R41 Volna adopts unique space feed arrangement with Frontal feed instead of backplane feed of ground based 5N63 or even Antey designed 9S32 family. Considering that later 30N6 radar used in Peter the great and Chinese S-300F use basically the same radar as ground based variant. I dont really see a reason why "Navalized" 5N63 cant exist.


One interesting speculation i found in a Japanese website was that the Volna operates in 2 frequencies. Thus it has 2 feeds, 1 is frontal while the 2nd frequency is in the backplane, with following speculative schematics.

Volna-2.jpg

Source :

I lend to support this assessment, because for naval environment, tracking low flying target popping above the horizon creates a low angle target tracking situation which requires rather narrow beamwidth probably less than 1 degree. Why ? So that the beam hopefully doesnt illuminate the surface which may result in multipath error which can creates phenomenon where target appears to change attitude sharply or disappear and reappear to radar. The second frequency is probably higher than the first like Soviet practices for the Smerch radar. The example given in 3rd edition of "Introduction to radar systems" by Skolnik gives 9 GHz and 35 GHz dual frequency for low angle target tracking. Plus the ECCM consideration.

But what do you guys say ? Maybe i can have second or third opinions on the matter.

As a side note. The Soviet navy back in 70's and 80's seems to favor space feed with forward mounted feed for their phased array radar's. Another example is Klinok (Naval Tor) One may see that the Cross Sword radar it use is Greatly differs to the one in surface application. The Cross Sword radar also appears to have much greater element counts compared to its surface based sibling. One possible reason is that to allow greater angle of electronic beamsteering.

The ground based TOR's target tracking radar, only have about 7 degrees of electronic beamsteering capability. It is a thinned array with 3 wavelength of element spacing, the elemen counts is about 500. It is done mainly to reduce cost while still allowing narrow beamwidth for tracking and tracking of several targets simultaneously. However thinned array is not suitable for large angle beamsteering as grating lobe may enter the "real space" of the antenna and rob the gain of the main antenna. The space feed solves this issue by allowing large element counts yet feed can be kept simple as there is nothing in between the main feed and the antenna elements.
 
It may not actually be too different. What follows is mostly speculation as I've not found any internal drawings or photos of TOP DOME either. The reason the 5N63 appears to be rectangular is that the central octagonal array is surrounded by four smaller circular antennas for sidelobe cancelling. There are also two other arrays above and below the main array, likely used for IFF and missile tracking/uplink. Remove all of this, leaving the main array, and you can get something similar to TOP DOME. The smaller radome on TOP DOME is the one used for missile uplink, and the three antennas below that one may be used for missile tracking or sidelobe cancelling (other antennas aboard ship could possibly perform some of those functions as well). That leaves the main array. If you encase the main array and the optical space feed, not the worst idea in a maritime environment, you could get something similar to TOP DOME. Why a frontal feed? There's an access door on the back of the radar housing, likely to enter to replace electronic components or perform minor maintenance without removing the array face's cover. Could simply be that this arrangement necessitated not having the feed behind the array.
 
It may not actually be too different. What follows is mostly speculation as I've not found any internal drawings or photos of TOP DOME either. The reason the 5N63 appears to be rectangular is that the central octagonal array is surrounded by four smaller circular antennas for sidelobe cancelling. There are also two other arrays above and below the main array, likely used for IFF and missile tracking/uplink. Remove all of this, leaving the main array, and you can get something similar to TOP DOME. The smaller radome on TOP DOME is the one used for missile uplink, and the three antennas below that one may be used for missile tracking or sidelobe cancelling (other antennas aboard ship could possibly perform some of those functions as well). That leaves the main array. If you encase the main array and the optical space feed, not the worst idea in a maritime environment, you could get something similar to TOP DOME. Why a frontal feed? There's an access door on the back of the radar housing, likely to enter to replace electronic components or perform minor maintenance without removing the array face's cover. Could simply be that this arrangement necessitated not having the feed behind the array.

This brings question on where the control room for the 3R41's.

If it follows the same arrangement as the ground based the 5N63 family where the control room is elsewhere. Then using the reflective array is nearly senseless considering the performance penalty it brought. 5N63 is ideal not only because it is flat which radar likes (radome error slope is small) It also free of obstruction which feed structure may present. Lesser sidelobe and error slope = happy radar.

If it use reflective array anyway..then there has to be something that make it worth.. hence i supported the 2 frequencies speculations.

However if the control room Is right below the antenna then it could make sense as the radar transmitter and receivers have to go somewhere and it cannot be in same place as the crew. This then putting those behind the array make sense and the feed, will then have to be located at front.
 

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