Military Review

Seven nannies have hydroacoustics - orphan

24

The Russian submarine of the 877 project is called a “black hole” for the difficulty of detecting it with sonar tools.



Viktor Kuryshev’s article “Underwater, gloom and silence,” published in Independent Military Review No. 16 from 17.05.13, evoked many responses both in support and against the author’s suggested way to solve the current hydroacoustics problem.

In response to this publication in his article “Neither darkness nor silence” (“NVO” No. 26 from 25.07.13), the head of the working group on the “Hydroacoustics-2020” program, Academician of the Russian Academy of Sciences Vladimir Peshekhonov ensures that works will lead to the creation of a new generation of hydroacoustics and bring it to a qualitatively new level. ” We are informed that the “scale of the problem” demanded “unification of efforts of all enterprises engaged in research and development in the field of hydroacoustics”. As a result of these efforts, the concept of hydroacoustics development, the target program “Hydroacoustics-2020”, was developed, financing in the amount of 48 million rubles was secured. and a working group of 30 specialists was organized.

LASTING FOR DECADES

The problem of licensed specialists is solved, though with a delay of 30 years. Victor Kuryshev was engaged in solving this problem. True, for this he used the signals of the standard hydroacoustic station (GUS). 30 years have passed, there was a change in the effective owner of the problem issue. Viktor Kuryshev, with his experience in resolving technical issues, is not involved in the work, since he is not a sound engineer and does not know how to lead discussions. Now everything is back to the original positions, although the reserve already exists.

The tradition of Russian hydroacoustics is to be late and catch up, to borrow other people's decisions, to conduct broad campaigns to master them. There is little benefit from such a strategy. It is difficult to imagine that concerns such as Okepribor, Gidropribor, Atoll, Elektropribor, are able to quickly respond to problems in underwater acoustics. It is unacceptable to show initiative, it is impossible to have your own point of view. For this reason, brainwashing occurs. Initiative energetic experts go into a small business. It is on the shoulder of small business - to quickly resolve issues, promptly recognize and correct mistakes, correct technical solutions. The hydroacoustic industry is categorically rejecting the use of the potential of small business. The consequences of this practice are sad. The lag in the development of passive hydroacoustics for more than 20 years. Obviously, this gap will only increase.

However, let us return to the task of the invention - reducing structural interference from the carrier. And what about the reception of signals with stationary HAS and hydroacoustic buoys? For them, there is also the problem of receiving signals.

The authors are aware of the construction of a dipole receiver from two hydroacoustic sensors, which allows for receiving a signal only from certain directions. This antenna system intend to use to reduce structural interference from the carrier.

Opinion of a member of the Scientific Council on the complex problem of Hydrophysics of the Russian Academy of Sciences, captain of the 1 rank, retired Mikhail Volzhensky: “Work on vector-phase reception in Russia has been and is being conducted during the last 40 years. Apparently, the problem is that the research results are unstable or of little use for practical use. ” Indeed, “the level of interference recorded by PGD (pressure gradient receiver) is much higher than the same level for PD (pressure receiver). At the frequency of 10 Hz, this difference reaches 50 dB "(from the book by VA Gordienko" Vector-phase methods in acoustics "). The authors of the application intend to solve hydroacoustical problems on such sensors.

FAILURE OF ARGUMENTS

Interference compensation is possible with high identity of sonar sensors. The higher the identity, the higher the degree of compensation. The authors of the application, apparently, do not attach importance to the fact that ensuring the identity of the piezoceramic sensors is an unsolvable problem.

The conversion of hydroacoustic signals using piezoceramic sensors is characterized by limitations in terms of:

1) depending on changes in static pressure and temperature;

2) reduce the conversion efficiency in the low-frequency region of the spectrum of effects;

3) low identity of sensitive elements (at the level of 10%).

Explanatory notes on 1. Renowned American hydroacoustic specialist R. J. Bober in his book “Hydroacoustic Measurements” concludes: “The stability of their parameters over time with a change in static pressure and temperature was in many cases much worse than it should have for exemplary measuring transducers”. And further: "Thus, despite the significant progress achieved during the Second World War, the state of affairs in this area in 1945 was still unsatisfactory." This conclusion was made in relation to the model converters. Consequently, working transducers have obviously the worst parameter changes as a result of changes in static pressure and temperature. Thus, the mandatory certification of working converters loses practical meaning. The main parameters of the converters will still go away as a result of the influence of the specified operating factors. The conditions of hydroacoustic measurements are always not constant, therefore, fluctuations of the measured parameters are inevitable.

Explanatory notes on 2. Every hydroacoustical expert is aware of a reduction in the efficiency of converters with a decrease in the frequency of effects - 6 dB per octave. It is known that transducers work well in the field of sound frequencies. By reducing the exposure frequency from 2 kHz to 2 Hz, the conversion efficiency is reduced by 60 dB. Consequently, with a decrease in the frequency of impacts, we have significant distortions and losses of an important part of the information. A free-time reader is referred to the book “Hydroacoustic Measurements”, which presents a typical frequency response of a piezohydrofon with a “shelf” in the region of medium sound frequencies and a decrease in the area of ​​infrasound.

However, the spectral and energy characteristics of noise fields have an increasing characteristic with decreasing frequency. This is an increase at 1 Hz on average by 60 dB higher compared to high sound frequencies. Thus, piezoceramic sensors have a typical, far from adequate conversion characteristic.

Repeated attempts to improve the efficiency of piezotransformation in the area of ​​low sound frequencies did not work, since, together with informative influences, the useful signal is modulated by powerful infrasound frequencies that are outside of the frequencies accepted for consideration. In this case, the question arises of the allocation of the useful signal on the background of intense noise. This is a separate, unsolvable problem when using a known method for converting hydroacoustic signals.

Explanatory notes on 3. To isolate the useful signal from the noise background, it is necessary to provide differential signal conversion. The quality of the differential transformation is determined by the identity of the primary transformation elements used. Here is a quote from R. J. Bober with respect to dipole transducers: “The electrical signal at the output is proportional to the phase difference between the sound pressure on the two probes. Such a design requires the identity of the electroacoustic characteristics of probe hydrophones, which is difficult to implement in practice. "

A similar conclusion is made later 30 years Valery Gordienko in relation to the two spaced in space pressure receivers. "Requires channel identity in amplitude of at least 0,1 dB." “Since it is easier to make a single-element PGD than to provide the indicated path identity, the PGD constructions based on two separated hydrophones have not found wide application in hydroacoustics.” Thus, when using a differential transformation, the requirements for the identity of elements increase. Such opportunities are absent today.

Thus, based on the well-known piezoceramic transducers, “creating a new generation of hydroacoustics tools and bringing it to a qualitatively new level” is an unrealistic task.

Valery Gordienko makes the main conclusion: “At present, methods based on the use of information recorded by pressure receivers have reached their limits.” High-quality primary conversion of hydroacoustic information over 70 years remains problematic. To solve this problem, it is necessary to search for other effective methods for the primary conversion of hydroacoustic information. Is academician Vladimir Peshekhonov ready to solve this urgent problem? Is it possible to develop hydroacoustics at a faster pace?

SOLUTION NOT FOUND

All история passive military underwater acoustics is determined by the possibility of long-range detection of ships of a potential enemy. The spectrum of hydroacoustic information accepted for consideration is in the frequency range 10 – 10 000 Hz. The most informative is the low-frequency region of the spectrum of effects. Low-frequency effects extend over long distances without significant attenuation. The amplitudes of these effects can significantly exceed the amplitudes of the signals in the middle part of the frequency spectrum. The abundance of infrasound sources, including at frequencies below 10 Hz, necessitates the selection of a useful signal in the background of noise.

Impacts in the middle part of the sound range are characterized by low amplitudes and high attenuation. According to Mikhail Volzhensky, these signals extend to units of kilometers. Known piezoceramic transducers provide reception of signals in the middle part of the audio range. So we have to deal with the "tails" of real hydroacoustic information.

The measures taken to reduce the noise of submarines are effective in the middle of the frequency spectrum. The useful spectrum of the signal is almost shifted to the low-frequency region. This gives the effect of "smooth spectrum". Thus, the individual signs of objects are shifted to infrasound. And we can not work in it. No efficient primary transducers. This question today is a problem. And not only for Russia, but, obviously, for hydroacoustics of other countries. Such a well-known SOSUS system was removed from duty, probably for the obvious reason for the low resolution in the low-frequency region of the spectrum. This is the result of measures to de-humidify our submarines. It can be assumed that the hydroacoustics of the likely adversary are actively engaged in exploratory development in the field of receiving infrasonic signals. Do we have adequate solutions to this issue?

UNDERSTAND AND REPORT. And IN RESPONSE - SILENCE

I am an engineer, for about 30 years I have been engaged in independent development of the method of differential data conversion. The method has significant advantages over the known conversion method. In the process of development, we managed to find solutions for two problematic tasks. One of these tasks is to provide high-quality conversion of acoustic information. In the process of development, a technical solution was determined for the sensor, the conversion efficiency of which at low frequencies is more than 40 dB higher than that of known hydrophones.

There is a rule: to understand and report. I have understood the problems and the possibilities of their practical implementation. No one to report. More than 30 organizations that specialize in acoustic signal conversion are familiar with the development. Specialists and management of these organizations demonstrate a complete lack of interest in the development. Military customers respond that they have no right to direct the actions of the industry. Attempts to present materials of developments to the leadership of the country remain unanswered. Letters to the addressee do not reach. The administration usually forwards these letters to other departments. Response of the Russian Academy of Sciences: The Academy of Sciences does not deal with issues and issue opinions, and recommends publishing development materials in an open press. The answer from the Ministry of Education and Science of the Russian Federation prescribes participation in open competitions and presenting its own research in publications. The answer from the All-Russian Scientific Research Institute of Physico-Technical and Radio Engineering Measurements - the leading organization for the provision of metrology: "There is no need."
Author:
Originator:
http://nvo.ng.ru/armament/2014-02-21/9_hydroacoustic.html
24 comments
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  1. svp67
    svp67 23 February 2014 12: 51
    +5
    In a word -
    UNDERSTAND AND REPORT.
    and point belay
    1. lelikas
      lelikas 23 February 2014 13: 07
      +9

      -And how to be with Yeti?
      - Yeti - need to wash more often.

      The article is good, but too narrow-profile. I honestly read it twice, but as in that rhyme about Japanese doctors, I didn’t understand anything laughing
    2. Arberes
      Arberes 23 February 2014 13: 13
      +11
      More than 30 organizations specializing in the field of acoustic signal transformations are familiarized with the development. The specialists and management of these organizations demonstrate a complete lack of interest in the development. Military customers respond that they have no right to lead industry. Attempts to submit development materials to the country's leadership remain unanswered. Letters do not reach the addressee.
      How is everything sad? This is not the point, but the ellipsis should be! Someone will be responsible for this in the end then ???
  2. Name
    Name 23 February 2014 13: 18
    +7
    And all, if only superfluous of what .....
  3. Shadowcat
    Shadowcat 23 February 2014 13: 18
    +4
    Ahem ... And to write a letter to Putin and Shoigu, as they used to write in the name of Comrade Stalin and Comrade Zhukov (Comrade Beria), not? In mymoy, quite open comrades. Even the other conferences make one straight line.
    1. Ivan Petrovich
      Ivan Petrovich 23 February 2014 18: 25
      +3
      compared comrade Stalin with GDP? wrong scale
      1. Shadowcat
        Shadowcat 23 February 2014 19: 46
        0
        You know here how in the cards - you need to play with what is on hand, and not that a good buy will come right now. There was Stalin, but now he is gone, but there is some Putin. At least he will be better Jerkel, Holland, Obama.
      2. valentin1947
        valentin1947 April 16 2014 13: 34
        0
        Absolutely right! Modern "supreme commanders" are "open" only on television screens. If you want to know something else, similar to that stated in Viktor Kuryshev's article, you can read the article "Who benefits from the lagging of hydroacoustic weapons in bourgeois Russia?" and "About Viktor Kuryshev's article" In the underwater environment, darkness and silence "in LiveJournal at: http://lexin-valentin.livejournal.com
        Valentine and Victor Leksiny
    2. valentin1947
      valentin1947 April 16 2014 13: 33
      0
      Modern "supreme commanders" are "open" only on television screens. If you want to know something else, similar to that stated in the article by Viktor Kuryshev, you can read the article "Who benefits from the lagging of hydroacoustic weapons in bourgeois Russia?" and "About Viktor Kuryshev's article" In the underwater environment, darkness and silence "in LiveJournal at: http://lexin-valentin.livejournal.com
      Valentine and Victor Leksiny
  4. kundyshev
    kundyshev 23 February 2014 13: 40
    -5
    Where HYDROACOUSTICS begins, SCIENCE ends ....
  5. me
    me 23 February 2014 14: 19
    +4
    Seven nannies have fourteen boobs.
  6. homosum20
    homosum20 23 February 2014 14: 25
    +15
    The author, apparently, wrote for colleagues and himself:
    "Explanations to point 2. Every hydroacoustician knows about a decrease in the efficiency of transducers with a decrease in the frequency of impacts - 6 dB per octave. It is known that transducers work well in the audio frequency range. When the frequency of impacts decreases from 2 kHz to 2 Hz, the conversion efficiency decreases by 60 dB. Consequently, with a decrease in the frequency of impacts, we have significant distortion and loss of an important part of information.
    "However, the spectral-energy characteristics of noise fields have an increasing characteristic with decreasing frequency. This increase at a frequency of 1 Hz is, on average, 60 dB higher than at high audio frequencies. Thus, piezoceramic sensors have a typical, far from adequate conversion response."
    Awesomely accurately said, and, most importantly, expressed in an accessible language.
    I (our company) work with Okeanpribor (we make equipment for them). We communicate with people at the level of deputy CEOs - i.e. exactly those problems that the author is talking about. But we have never carried this engineering nonsense. Why discuss engineering problems in such a wide audience? You can talk about this at the edge of the pool where measurements are taken.
    Money is allocated, facilities needed to develop equipment are built, equipment is purchased. And that we are late - otherwise the author did not see what was happening to the country, thanks to the labeled (for which he even gave him the Order of Andrew the First-Called) and the drunk was going on. We do not live in a fairy tale. And in fairy tales it is said (at least in Russians) "the word speaks quickly, but not soon the thing is done ...".
    Not enough specialists? You will talk with the developers of computer chips. We are generally unable to create a modern computer. Few ? I can still talk about a lot. What for? And so we know.
    An empty article, in my opinion. It just took time and place.
    1. lapo32
      lapo32 23 February 2014 15: 44
      -1
      PR itself is not otherwise, some kind of nonsense, the level at low frequencies of the signal drops, and the level of harmonics grows
    2. Penzyac
      Penzyac 23 February 2014 17: 58
      +3
      It is written in too much detail, there are too many narrowly technical details, so the meaning is hidden behind the details. Managers do not read such details, for them it is easier to write, at the level of dummies, only meaning, and details in case of interest. Engineers are not only hydroacoustics, but any electronic engineers of the author understood, but most of the others are not. Alas.
    3. Nayhas
      Nayhas 23 February 2014 22: 26
      0
      Quote: homosum20
      An empty article, in my opinion. It just took time and place.

      Please clarify if possible. When I came across an article by Kuryshev, the question that he covers aroused interest. I found an article in which hydrophones with fiber optic sensors, which are supposedly installed on Virginia's nuclear submarines in conformal onboard passive GAS BQG-5A, are named as an alternative to vector-phase hydrophones. But fiber optic sensors allegedly have a problem with multiplexing and the solution is fiber laser sensors. But the most promising are named precisely the vector-phase hydrophones, as the most sensitive.
      Questions:
      1.Vector-phase hydrophones is the real future of passive ASEs?
      2. Are fiber optic hydrophones really used in passive sonar? Is it a dead end or a prospect?
      1. valentin1947
        valentin1947 April 16 2014 13: 46
        0
        We have been the developers of hydroacoustic equipment for the Navy since 1981. On tests of our experimental and prototypes in comparison with the best equipment of the head in the Sudprom, the developer of hydroacoustic equipment of the Oceanpribor concern spent in the mode of hydroacoustic operators of net total time (minus sleep, etc.) 2-3 years. We believe that we can quite competently judge the provisions of Viktor Kuryshev's article (which, basically, that is, according to most of the provisions, we support; we do not agree with Kuryshev's opinion on vector receivers). If you are interested in our opinion, you can read the article "Who benefits from the lagging of hydroacoustic armament in bourgeois Russia?" and "About Viktor Kuryshev's article" In the underwater environment, darkness and silence "in LiveJournal at:
        http://lexin-valentin.livejournal.com
        Valentine and Victor Leksiny
      2. valentin1947
        valentin1947 April 16 2014 14: 06
        0
        We have been the developers of hydroacoustic equipment for the Navy since 1981. On tests of our experimental and prototypes in comparison with the best equipment of the head in the Sudprom, the developer of hydroacoustic equipment of the Oceanpribor concern spent in the mode of hydroacoustic operators of pure total time (excluding sleep, etc.) 2-3 years. We believe that we can quite competently judge the provisions of Viktor Kuryshev's article (which, basically, that is, according to most of the provisions, we support; we do not agree with Kuryshev's opinion on vector receivers). If you are interested in our opinion, you can read the article "Who benefits from the lag of the hydroacoustic armament of bourgeois Russia?" and "About Viktor Kuryshev's article" In an underwater environment, darkness and silence "in LiveJournal at:
        http://lexin-valentin.livejournal.com
        Valentine and Victor Leksiny
  7. Duke
    Duke 23 February 2014 14: 33
    +3
    Opinion of a member of the Scientific Council on the complex issue of Hydrophysics of the Russian Academy of Sciences, retired rank 1 captain Mikhail Volzhensky: “Vector-phase reception in Russia has been and has been ongoing for the past 40 years. Apparently, the problem is that the research results are unstable or of little use for practical use. ”

    The vector-phase technique has long been tested in radio engineering complexes. It is necessary to connect enterprises, not only hydroacoustic ones, to the problem. For example NPO "Vector". There were real advances in separating signal from interference using the vector-phase method.
  8. Nitarius
    Nitarius 23 February 2014 15: 10
    +3
    in my opinion, many people want to know too much ..... here they provoke open and closed information.
    nothing to discuss what is not supposed to be!
  9. zaharov50
    zaharov50 23 February 2014 15: 12
    +7
    Again the Kuryshevs. How much public funds were used to get these gentlemen to confirm their technical proposals. And that, but nothing! Zero! But everything develops in a spiral, a lot has already been forgotten, new people have come - you can start over. Someone Boris Voronkov decided that time had passed and all attempts were forgotten to integrate vector-phase detection methods into ship and stationary SACs. And if you have forgotten, then maybe once again you can get money from the state defense order on this topic. And his argumentation is very similar (almost word for word) to the one that was in the 80s. But I would like to advise those who are currently making decisions on the financing of such "projects" to get acquainted with the results of the work up to state tests of prototypes that implement vector-phase methods. Then it will become clear to them what to do with the restless funnel and chickens. I will not dwell on the methods of suppressing ship jamming "at the entrance" of the SAC, I think it will not be long to wait when the "active" gentlemen will saddle this topic and once again open America.
    Alexander
    1. Nayhas
      Nayhas 23 February 2014 22: 25
      0
      Quote: zaharov50
      Kuryshevs again.

      Please clarify if possible. When I came across an article by Kuryshev, the question that he covers aroused interest. I found an article in which hydrophones with fiber optic sensors, which are supposedly installed on Virginia's nuclear submarines in conformal onboard passive GAS BQG-5A, are named as an alternative to vector-phase hydrophones. But fiber optic sensors allegedly have a problem with multiplexing and the solution is fiber laser sensors. But the most promising are named precisely the vector-phase hydrophones, as the most sensitive.
      Questions:
      1.Vector-phase hydrophones is the real future of passive ASEs?
      2. Are fiber optic hydrophones really used in passive sonar? Is it a dead end or a prospect?
    2. valentin1947
      valentin1947 April 16 2014 13: 50
      0
      We have been the developers of hydroacoustic equipment for the Navy since 1981. On tests of our experimental and prototypes in comparison with the best equipment of the head in the Sudprom, the developer of hydroacoustic equipment of the Oceanpribor concern spent in the mode of hydroacoustic operators of pure total time (excluding sleep, etc.) 2-3 years. We believe that we can quite competently judge the provisions of Viktor Kuryshev's article (which, basically, that is, according to most of the provisions, we support; we do not agree with Kuryshev's opinion on vector receivers). If you are interested in our opinion, you can read the article "Who benefits from the lag of the hydroacoustic armament of bourgeois Russia?" and "About Viktor Kuryshev's article" In an underwater environment, darkness and silence "in LiveJournal at:
      http://lexin-valentin.livejournal.com
      Valentine and Victor Leksiny
  10. AlexxxNik
    AlexxxNik 23 February 2014 15: 56
    +2
    I see no reason not to believe how, at one time, submarine officers wrote to the Central Committee, in my opinion, due to the KB’s reluctance to engage in reducing the noise level of boats, but instead they stupidly increased tonnage. Now the Russian Academy of Sciences, when it deals with real estate transactions, ignores the needs of submariners, Putin’s kick is needed again, although the experience of NK-93 shows that this kick can be easily ignored
  11. Volkhov
    Volkhov 23 February 2014 16: 41
    0
    For those who are replacing this power with good hydroacoustics and this topic has long been covered, for those who steers the remnants of the boats of the Russian Federation, the main problem is the export of capital and themselves - just like the course jumped, everyone needs a currency.
  12. Arh
    Arh 23 February 2014 17: 35
    +2
    Project 877 submarine !!! ***
  13. Igarr
    Igarr 23 February 2014 17: 59
    +4
    Interesting movie ....
    It turns out that they are also fighting for these - vector-phase methods .... from the same, damn it, the followers of the "Right Sector".
    Eh heh ..... well, of course, it’s more important for us ... a cultural consumer ... than a sonar practitioner .. and that's all.
    It is unrealistic to implement the Morskiy Ukha system on a boat scale.
    Hydroacoustics, within the existing framework, has reached the limit of its capabilities.
    The breakthrough shines in other areas .... offhand - PWM, noise-like signals, geomagnetic anomalies ... in the end, agree with the Mariinsky Depression civilization (just kidding).
    Interesting article. It’s a pity that it’s not vital.
  14. Michael_59
    Michael_59 23 February 2014 18: 22
    +2
    For 30 years, one should try to learn not only to flaunt highly specialized terminology, juggling with rarely used words, but also clearly indicate the essence of the issue and the possibility of practical application of the results of its solution. And not just on the wave of awareness of one's own significance, so many background noise can be generated that a useful signal is completely lost.
  15. duchy
    duchy 23 February 2014 19: 01
    +5
    Strange article. At VO I read about the "Black Hole", there are completely different opinions and solutions to this problem. Two "brothers of the acrobat" have developed technology and algorithms for detecting objects in an aquatic environment at long distances, more than that they have already been tested in real conditions, and it seems that they are already under construction underwater laboratory. And what to believe ?? PR of the author or reprint of old material? sad
    1. valentin1947
      valentin1947 April 16 2014 13: 58
      0
      For duche: If you already mentioned the "two brothers-acrobats", then indeed the distances were 190 km in the Pacific Ocean (there was a huge reserve of potential; the submarines simply did not go further, beyond the range). Well, as for the "underwater laboratory under construction" in today's bourgeois Russian Federation, which has everything on its side, these are fantasies. We have been the developers of hydroacoustic equipment for the Navy since 1981. On tests of our experimental and prototypes in comparison with the best equipment of the head in the Sudprom, the developer of hydroacoustic equipment of the Oceanpribor concern spent in the mode of hydroacoustic operators of net total time (minus sleep, etc.) 2-3 years. We believe that we can quite competently judge the provisions of Viktor Kuryshev's article (which, basically, that is, according to most of the provisions, we support; we do not agree with Kuryshev's opinion on vector receivers). If you are interested in our opinion, you can read the article "Who benefits from the lag of the hydroacoustic armament of bourgeois Russia?" and "About Viktor Kuryshev's article" In an underwater environment, darkness and silence "in LiveJournal at:
      http://lexin-valentin.livejournal.com
      Valentine and Victor Leksiny
  16. navigator
    navigator 25 February 2014 11: 31
    0
    It is a sensible article. Not without excesses. And to consider pr 877 a miracle, a black hole and the fear of all villains is a strong delusion.
    1. valentin1947
      valentin1947 April 16 2014 14: 03
      0
      We confirm that Project 877 is a "black hole" relative to other submarines, with the exception of low-noise ones with a water-jet propulsion unit. We have been the developers of hydroacoustic equipment for the Navy since 1981. On tests of our experimental and prototypes in comparison with the best equipment of the head in the Sudprom, the developer of hydroacoustic equipment of the Oceanpribor concern spent in the mode of hydroacoustic operators of net total time (minus sleep, etc.) 2-3 years. If you are interested in our opinion on the problems of hydroacoustic armament in the modern Russian Federation, you can read the article "Who benefits from the lagging of hydroacoustic armament in bourgeois Russia?" and "About Viktor Kuryshev's article" In the underwater environment, darkness and silence "in LiveJournal at:
      http://lexin-valentin.livejournal.com
      Valentine and Victor Leksiny
  17. navigator
    navigator 25 February 2014 11: 31
    0
    It is a sensible article. Not without excesses. And to consider pr 877 a miracle, a black hole and the fear of all villains is a strong delusion.