- Email: [email protected]
Maintenance of masking and limited performance of fire-fighting equipment from means of aircraft location
Measurement 136 (2019) 558–563
Contents lists available at ScienceDirect
Measurement journal homepage: www.elsevier.com/locate/measurement
Maintenance of masking and limited performance of fire-fighting equipment from means of aircraft location Igor Korobiichuk a,⇑, Maciej Kachniarz b, Volodimir Karachun c, Viktorij Mel’nick c, Sergii Fesenko c a
Warsaw University of Technology, Institute of Automatic Control and Robotics, Boboli 8, 02-525 Warsaw, Poland Warsaw University of Technology, Institute of Metrology and Biomedical Engineering, Boboli 8, 02-525 Warsaw, Poland c National Technical University of Ukraine ‘‘Igor Sikorsky Kyiv Polytechnic Institute”, 37, Avenue Peremogy, Kyiv 03056, Ukraine b
a r t i c l e
i n f o
Article history: Received 6 October 2017 Received in revised form 28 December 2018 Accepted 29 December 2018 Available online 6 January 2019 Keywords: Circumferential vibrations Wave size Aberration Caustic Wave coincidence
a b s t r a c t The paper presents description and analysis of the technical possibility of artificial formation of camouflage of military equipment and its limited prominence in open firing positions by creating an isolating barrier for air reconnaissance echo-location facilities. The discussed technical solution is presented in the example of a single tank. The conditions for partial and complete masking at the resonant level of wave coincidence with the help of caustic zones are substantiated. The semi-real tests, carried out with the material for the practical implementation of the camouflage of firearms on the defense line of open fortifications, gave satisfactory results. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction
1.2. Purpose and objectives of research
As it is commonly known, the decisive role in field fortification is occupied by shelters for military equipment and materiel. A wide use was made of structures of both open and closed type. The open structures are the most massive and have the form of excavations. For weapons, such as tanks, self-propelled artillery, the basic type of fortification on the position is the trench. The suddenness of the use of combat weapons multiplies its strength. So the purpose of presented work is to solve the problem of proper disguise allowing to maximize suddenness of the combat weapon use. Modern disguise should provide the necessary concealment effect from enemy air reconnaissance, as well as from its weapons control systems.
The aim of the research was to evaluate the prospect of a technical solution for the concealment of military equipment in fortifications of the open type of the defense line in the laboratory conditions. The idea of the investigated technical solution is based on the artificial formation of a surface that fences the fire technique in the form of a caustic zone (zone of kaustikos) [1]. In order to provide technical solution applicable in the military equipment, the problems of estimating the influence of wave size and wave coincidence on the degree of realization of camouflage and also the elucidation of its prominence, must be solved. For the performed investigation the example of tank in the trench was used. The efficiency of the technical solution at the resonant level is estimated.
1.1. Object of research The object of the conducted studies is the process of elastic interaction of acoustic waves artificially generated with a cylindrical shell in the form of two coaxial cylindrical components, separated by a liquid, forming a unique tunnel, partially submerged in the ground around the pit trench and ramp (from French appareil). ⇑ Corresponding author. E-mail addresses: [email protected] (I. Korobiichuk), m.kachniarz@mchtr. pw.edu.pl (M. Kachniarz), [email protected] (V. Karachun), [email protected] (V. Mel’nick), [email protected] (S. Fesenko). https://doi.org/10.1016/j.measurement.2018.12.102 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
2. Analysis of literature data and formulation of the problem The appearance and development of armored vehicles capable of protecting the crew and supporting their units with fire leads to the creation and improvement of antitank vehicles. Lately, a lot of new means of protection have appeared. Not so long ago the tank had enough to have high-quality armor, which would protect from bullets and splinters. In [2–5] the fundamentals of the dynamics of apparatuses of various classes in solving problems of echolocation are presented [6]. The ways of creating acoustically
I. Korobiichuk et al. / Measurement 136 (2019) 558–563
‘‘invisible” objects when solving detection problems and acoustically ‘‘opaque” are being analytically justified – when solving support tasks. But time does not stand still and the military industry is developing rapidly. One of the examples of modern military equipment is the missile system Spike-NLOS used is a multipurpose multiplatform electro-optical missile system that is designed to defeat enemy armored vehicles, well-protected objects (such as bunker) and other engineering structures, as well as enemy personnel and its surface targets. In the summer of 2015, Israel officially recognized the presence of a previously classified form of military equipment – a mobile missile system on the caterpillar chassis of the tank – Pereh. According to Israeli experts, this machine, armed with anti-tank missiles, changes the idea of modern combat. This is the world’s first over-the-horizon anti-tank self-propelled unit. The effective range of these missiles is up to 25 km. The weight of one missile in a transport container is 71 kg. On the flight trajectory, the average speed of the rocket is 130–180 m/s, armor penetration – up to 1000 mm of steel homogeneous armor. These missiles can be effectively used at temperatures from 32 to +49 degrees Celsius and stored at temperatures from 45 to +71 degrees Celsius. Depending on the tasks to be solved, the missile can be equipped with different kinds of warheads – fragmentation, cumulative or multifunctional [7]. Technical solutions are proposed for the improvement of the M60A3 tank called Sabra – the use of a 120 mm gun and a modern digital fire control system. But this model has its own significant drawbacks – homogeneous armor and relatively low mobility [8]. On the basis of experience of the local military conflicts, the theory of modern tank design was developed [9]. According to this theory, in order to dominate the battlefield, a modern tank must meet a number of very important requirements and be created on the basis of the principle of ‘‘six zones”: avoid a collision, avoid detection, avoid escorting, avoid getting, avoid penetration and avoid defeat. The means of protection in the near zone can include a container with anti-aircraft missiles, controlled by the same ‘‘artificial intelligence”. When the tank receives data from the UAV about the use of aircraft weapons against itself, it counterattacks with anti-aircraft guided missiles with a high degree of speed and destroys them when approaching a tank, where ‘‘air control” is carried out by its own on-board radar [10]. In recent decades, numerous theoretical studies have been carried out in the field of modern military equipment and means of its defense. One of the latest examples are some results of the American FCS program (Future Combat Systems). The result of one of the studies within the FCS program was the concept of Survivability Onion or Onion Skin. This concept implies the division of the protection of an armored vehicle into six conventional ‘‘layers”: Avoid Encounter, Avoid Detection, Avoid Acquisition, Avoid Hit, Avoid Penetration and Avoid Kill. Each of them deals with different moments of enemy attack and is associated with the use of certain systems designed to prevent certain enemy actions [11–13]. Also, an elastic polymer is proposed that replicates the ability of the skin of a squid and an octopus: it changes its color and texture of the surface. Camouflage from such an elastomer can hide a soldier or armored car in any situation. Elastomeric camouflage has one drawback: each type of elastomer can only reproduce one pattern of texture and color. The scientists created a simple mimicry camouflage [14]. Utilization of intensity for predicting the distribution of sound in confined spaces has recently been used within computer simulation to represent sound coming from various sources [15]. This creates the possibility of reduction of the amount of information to be computed and makes the simulation system simple enough to be presented on a desktop computer. Availability of new technologies has made it viable to simulate sound distribution in
559
confined spaces using pressure, including phase information [16]. Possibilities of simulation are also considered using methods of transforming optics for layers of bending waves within elongated frame constructions [17]. Sound is transmitted through double walls of a cylindrical shell with a steam-tight pad in an active zone, which excites pressure oscillations due to an external turbulent boundary layer [18]. It is proposed to use acoustics of a conformal transformation for creating camouflage devices with layered homogeneous structures that can acoustically generate object illusions [19]. A camouflage coating that can mask an arbitrary object simulating electromagnetic scattering of an empty V-shaped cavity under a metal surface is proposed to be used on the basis of optical conversion. This camouflage device will mislead and confuse detectors and people, and, therefore, any object hidden under this camouflage coating will not be detected [20]. A coherent phantom track method is considered as an illusion of a radar network by controlling several electronic combat vehicles [21]. This paper analyzes the effect of dispersion of electromagnetic parameters and thickness on absorbing material characteristics [22]. Technical supply of masking means for firing and fighting equipment, primarily for open fortifications, is an inevitable problem for a regular army in a combat zone. Idea and structure of this problem are to artificially introduce, in the recording device, changes in means of locating the images of firing and fighting equipment in whole or its individual fragments using a standing screen. The purpose of these actions is to form more or less false (distorted) perception of images of firing and fighting equipment. Solution of this problem will serve as a foundation for implementation of a global strategic advantage: ‘‘To surprise is to win!” The presented work analyzes the advantage of one of the possible technical solutions, namely, the use of ultrasonic devices to create a masking barrier for firing equipment in the form of two coaxial shells separated by fluid [23]. Given a considerable length of outer shell wave being much greater than one, sound waves emitted by the outer shell into fluid at low frequencies, which are below the boundary frequency f lv , occur in the intermediate liquid layer of intershell space and form a closed circuit, the socalled caustic zone, where there is a sharp increase in energetic state of fluid separating the shell. These phenomena occur due to aberration of sound waves emitted by an outer shell into fluid. Availability of wave coincidence provides the maximum energy fraction of ultrasonic radiation directed to creation of a more highly turbulent caustic zone at the resonance level, as a result of the so-called effect of ‘‘acoustic transparency” of the outer shell [24]. The turbulent zone will be perceived by means of location as a set of images of grass, branches, etc. of a battlefield landscape. Thus, the problem of camouflage of armored vehicles appears to be an important component of combat support and the solution of this problem is extremely urgent [25].
3. Materials and methods In the presented paper, one of the technical implementations of camouflage and the limited prominence of fire weapons from aerial reconnaissance is investigated. The open-type fortification on the line of defense in the form of a trench for a tank with a limited firing sector is considered. The trench contains a pit, a ramp (from French appareil) and parapet. It is proposed to cover the trench and the tank with a cylindrical shell of two coaxial fragments separated by a liquid. Moreover, the lower part of the shell is partially submerged in the ground under the foundation pit. By acting on the outer shell with an acoustic beam, in its surface a circular wave is excited that is at a frequency below the boundary wave f bo when the condition of the large wave size of the outer shell is satisfied, i.e.
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1 kR
ð1Þ
where k ¼ c0 is wave number; x is radiation frequency; c0 is speed x
of sound in air; R is radius of outer shell. This will lead to the penetration of radiation inside, those in the sheath of the sound wave separating the shell at an angle of aberration, the angle a (Fig. 1)
cos a ¼
c0 V ob
ð2Þ
where V ob – circumferential velocity in the shell. The aberration created by this condition radiated sound waves will create caustic zone in a liquid in the form of a confocal inner surface of the outer shell with a cross-section in the form of a circle (Fig. 1).
x2 y2 þ ¼1 2 c R cos2 arc sin V 0 R cos2 arc sin Vc0 2
ob
ð3Þ
ob
With the artificial formation of wave coincidence, the caustic zone creates such a degree of turbulence, which will become an insurmountable obstacle to echolocation and on the screen of the sensor only the vague spot will be visible instead of the image with the contours of the tank. Technical specifications of installation are as follows: Power supply: 220 ± 10% V; Network frequency: 50 Hz; Power consumption: NMT 700 ± 10 W; Ultrasound frequency: 35 ± 2.0 kHz. Phenomenon calculations: For ease of perception of the studied phenomenon, the selected material for shells is glass (speed of sound is co = 1497 m/s), and the liquid in the intershell space is ordinary drinking water (V = 5370 m/s). Radius of the outer shell is R = 22.5 mm and radius of the inner shell is R1 = 18.5 mm. Wavelength is:
kR ¼
x ca R
¼ 35; 41 103 ;
ð4Þ
where ca = 331 m/s is the speed of sound in the air. Thus, the requirement 1 << kR for the magnitude of outer shell wavelength is fulfilled; x is the frequency of radiation; Ris the radius of the outer shell, leading to emission inside, that is, into fluid separating the shells, the sound wave at an angle of aberration, the angle a:
sin a ¼
c0 0; 06 V
where V is the velocity of a circular wave in water. Of course, it is possible to use bending waves instead of circumferential, but in this case the periphery of the surface of the tank will be clearly seen on the screen. The main element of the test stand is the generator of acoustic oscillations. Its functions are entrusted to the ultrasonic installation of an industrial sample, which forms an ultrasonic beam with a frequency of 36 kHz (Fig. 2) with a flat wave front. Radiation power is 700 W. The cascade ultrasonic radiator consists of a titanium rod, which is enclosed in a shell of stainless steel, and an ultrasonic generator. A rod is an emitter that converts electrical energy into ultrasonic vibrations. On the rear wall of the generator the output of the network wire is located. The immersion unit is connected to the ultrasonic generator.
ð5Þ
4. Experiments and results The model of the tank is located in a round shell immersed in the water. When the irradiation is off, the contours of the tank layout are clearly visible on the screen (Fig. 3, a). The inclusion of an ultrasonic device forms a circumferential wave in the circumference of the outer shell, which emits a sound wave into the separating fluid between the shells at an angle a to the velocity vector of the circumferential wave. Thus, a cylindrical caustic zone is created in the liquid near the inner surface of the outer shell of the tunnel. The surface of the caustic, in contrast to the static state of the liquid, has an increased energy state, which manifests itself in the form of a turbulent structure (Fig. 3, b). The image of the tank, due to this, gets less clear outlines, but, at the same time, the prominence of the test specimen is sufficient to classify it as a means of fire equipment. Changing the direction of the ultrasonic beam with respect to the outer normal of the outer shell at an angle of incidence 10 degrees the manifestation of a resonant situation is achieved, which is expressed in the form of ‘‘acoustic transparency” of the outer shell. This leads to a significant increase in the power of the ultrasonic beam penetrating the interior of the liquid, practically without dissipation of sound energy, which allows to achieve the desired result, namely - to transform the tank image into a blurred spot on the screen (Fig. 3, c). It is also very important to remove images of locator outlines of serving people in military equipment on the sensor screens. The effect of the invisibility of personnel and material support of fire
a ¼ 3 410
Fig. 1. Formation of caustic zone: R – outer shell diameter, R1 – inner shell diameter.
Fig. 2. Appearance of the test stand.
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Fig. 3. Appearance of the model of the tank exposed to ultrasonic radiation: a) ultrasound generator is disconnected; b) ultrasound generator included; c) direction of the ultrasonic beam changes until the onset of resonance-wave coincidence.
equipment as in the first case is realized in the same volume and in the same quality (Fig. 4). Thus, as it can be seen, the image of the personnel and material support is absent. 5. Discussion The degree of turbulence of the liquid in the caustic zone is maximal when irradiated with an ultrasonic beam at frequencies below the boundary (infrared component, IR radiation). Its effectiveness for solving the tasks of masking the tank and the degree of admissibility of fire weapons in open fortifications directly depends on the angle h between the wave vector of infrared radiation and the outer normal of the outer shell of the enclosing tunnel – known Kremer rule for shells of considerable wave size, when
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Fig. 4. Operating personnel of fire equipment: a) in the absence of artificial irradiation of the installation with an acoustic beam; b) in the absence of a resonant environment in the outer shell; c) offensive of resonance.
kuk the relation (kp ¼ sinh , where kP – circumferential wavelength of outer shell, kuk – circumferential wavelength of infrared radiation) about the necessity of equality of the trace of the incident infrared ray and the circumferential wave of the outer shell, the so-called coincidence angle h. That is, depends on the proximity of the presence of the wave vector of radiation to the resonance zone of wave coincidence – geometric resonance. The circuit under analysis obviously does not build the second caustic zone, but already flexural oscillations of the outer shell, which are known to occur at frequencies above the cut-off frequency. If bending vibrations formed a caustic zone, then the radius of the cylindrical caustic zone realized by the bending waves would, as it is well known, be much less than the radius of the cylindrical caustic from the infrared ray (if there was liquid inside the enclosing tunnel). But, since the liquid is only between the
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outer and inner shell of the enclosing tunnel, and inside the safety tunnel there is no liquid, and air is present, then the second caustic at high frequencies cannot be formed in this construction. Experimental semi-detailed studies were carried out on a tank model located in a shielding tunnel of a modular construction of two coaxial cylindrical shells separated by a liquid. Irradiation of the outer shell with ultrasound at a frequency of 36 kHz with the help of the UZP-6-1 device of the Ukrainian production made it possible to confirm the theoretical justification for the possibility of masking fire equipment in open fortifications - near the resonance region (wave coincidence), and also in the zone of geometric resonance, when the trace of the emitter wave and the circumferential wave of the outer shell coincide (Kremer’s rule). In the photographs of the experiment presented in the manuscript, the second image corresponds to the finding of radiation near the resonance region of the wave coincidence, the third photograph shows the result of masking the mock-up of the fire equipment in the resonance region of the wave coincidence. It is obvious that the resonance zone provides maximum turbulence of the caustic surface in the inter-shell space and, thus, ensures the fulfillment of the requirements of limited prominence and absolute camouflage of the investigated object of fire equipment. The result of the semi-full-scale tests satisfactorily confirms the predicted situation of aberration of sound waves emitted by the outer shell into the liquid and the formation, with their help, of the surface of the cylindrical caustic zone, which forms the maximum possible turbulence of the fluid of the interlobar space of the enclosing tunnel and serves as a sufficient technical means for demanding complete masking of defense equipment. The above photographs show that finding the beam of an ultrasonic radiator near the resonance region of wave coincidence allows only a slight distortion of the prominence of the contours of the fire equipment, as well as its surface, at which the main details of the weapons will be still seen quite well by the means of the location of air and space reconnaissance. By displacement of the direction of the ultrasonic beam into the resonance zone, when the trace of the incident wave and the circumferential wave of the envelope coincide, it makes it possible to increase the energy state of the liquid to a value providing complete masking of the product and blurring its contours to an indefinite form. The photographs are quite convincing confirmation of the theoretical premises. Further deepening of research, their specification to certain classes of fire equipment should be carried out at defense enterprises in a certain sequence – experimental design development, factory testing of fire equipment, state testing of fire equipment. For understandable reasons, the coverage of this information is the prerogative of the respective enterprises. 6. Conclusions The possibility of securing the disguise of fire weapons in fortified structures of an open type line defense against enemy air reconnaissance based on the use of resonant phenomena in acoustic media is presented in the paper. The values of the necessary parameters of the laboratory installation are numerically established - wave size, wave coincidence and zones of the caustic of the phenomenon being investigated. The possibility of masking not only military equipment on positions, but also the military units of the logistical support is discussed. The technical decision taken to ensure the necessary level of camouflage and admissible fidelity of the defense line weapons, tested on a laboratory installation, opens the possibility for further expansion and deepening for the proposed technical solution in combat conditions. First of all, this is connected with the possibility of remote control and regulation of military equipment and logistical support not only in positions, but also in the course of hostilities.
The proposed technical solution allows to significantly influence the level of unexpected use of firearms in combat conditions, and also to form false fortifications of an open type with remote control on the line of defense, which can also serve as an advantage of the defending side and the isolation of echolocational means of aerial reconnaissance. The semi-real tests, carried out with the material for the practical implementation of the camouflage of firearms on the defense line of open fortifications, gave satisfactory results. At this stage, the consent of the special design bureau for carrying out experimental design work in terms of tasks assigned and the Act on the implementation of the results of theoretical studies of authors was signed. For known reasons, the details and depth of disclosure of raised issues cannot be covered in the open access, therefore the authors explain this reason for the incomplete measure of disclosure of practical results.
Funding This research was funded by the statutory funds of the Institute of Metrology and Biomedical Engineering, Warsaw University of Technology.
Conflicts of interest The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of the data, in the writing of the manuscript, or in the decision to publish the results.
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Contents lists available at ScienceDirect
Measurement journal homepage: www.elsevier.com/locate/measurement
Maintenance of masking and limited performance of fire-fighting equipment from means of aircraft location Igor Korobiichuk a,⇑, Maciej Kachniarz b, Volodimir Karachun c, Viktorij Mel’nick c, Sergii Fesenko c a
Warsaw University of Technology, Institute of Automatic Control and Robotics, Boboli 8, 02-525 Warsaw, Poland Warsaw University of Technology, Institute of Metrology and Biomedical Engineering, Boboli 8, 02-525 Warsaw, Poland c National Technical University of Ukraine ‘‘Igor Sikorsky Kyiv Polytechnic Institute”, 37, Avenue Peremogy, Kyiv 03056, Ukraine b
a r t i c l e
i n f o
Article history: Received 6 October 2017 Received in revised form 28 December 2018 Accepted 29 December 2018 Available online 6 January 2019 Keywords: Circumferential vibrations Wave size Aberration Caustic Wave coincidence
a b s t r a c t The paper presents description and analysis of the technical possibility of artificial formation of camouflage of military equipment and its limited prominence in open firing positions by creating an isolating barrier for air reconnaissance echo-location facilities. The discussed technical solution is presented in the example of a single tank. The conditions for partial and complete masking at the resonant level of wave coincidence with the help of caustic zones are substantiated. The semi-real tests, carried out with the material for the practical implementation of the camouflage of firearms on the defense line of open fortifications, gave satisfactory results. Ó 2019 Elsevier Ltd. All rights reserved.
1. Introduction
1.2. Purpose and objectives of research
As it is commonly known, the decisive role in field fortification is occupied by shelters for military equipment and materiel. A wide use was made of structures of both open and closed type. The open structures are the most massive and have the form of excavations. For weapons, such as tanks, self-propelled artillery, the basic type of fortification on the position is the trench. The suddenness of the use of combat weapons multiplies its strength. So the purpose of presented work is to solve the problem of proper disguise allowing to maximize suddenness of the combat weapon use. Modern disguise should provide the necessary concealment effect from enemy air reconnaissance, as well as from its weapons control systems.
The aim of the research was to evaluate the prospect of a technical solution for the concealment of military equipment in fortifications of the open type of the defense line in the laboratory conditions. The idea of the investigated technical solution is based on the artificial formation of a surface that fences the fire technique in the form of a caustic zone (zone of kaustikos) [1]. In order to provide technical solution applicable in the military equipment, the problems of estimating the influence of wave size and wave coincidence on the degree of realization of camouflage and also the elucidation of its prominence, must be solved. For the performed investigation the example of tank in the trench was used. The efficiency of the technical solution at the resonant level is estimated.
1.1. Object of research The object of the conducted studies is the process of elastic interaction of acoustic waves artificially generated with a cylindrical shell in the form of two coaxial cylindrical components, separated by a liquid, forming a unique tunnel, partially submerged in the ground around the pit trench and ramp (from French appareil). ⇑ Corresponding author. E-mail addresses: [email protected] (I. Korobiichuk), m.kachniarz@mchtr. pw.edu.pl (M. Kachniarz), [email protected] (V. Karachun), [email protected] (V. Mel’nick), [email protected] (S. Fesenko). https://doi.org/10.1016/j.measurement.2018.12.102 0263-2241/Ó 2019 Elsevier Ltd. All rights reserved.
2. Analysis of literature data and formulation of the problem The appearance and development of armored vehicles capable of protecting the crew and supporting their units with fire leads to the creation and improvement of antitank vehicles. Lately, a lot of new means of protection have appeared. Not so long ago the tank had enough to have high-quality armor, which would protect from bullets and splinters. In [2–5] the fundamentals of the dynamics of apparatuses of various classes in solving problems of echolocation are presented [6]. The ways of creating acoustically
I. Korobiichuk et al. / Measurement 136 (2019) 558–563
‘‘invisible” objects when solving detection problems and acoustically ‘‘opaque” are being analytically justified – when solving support tasks. But time does not stand still and the military industry is developing rapidly. One of the examples of modern military equipment is the missile system Spike-NLOS used is a multipurpose multiplatform electro-optical missile system that is designed to defeat enemy armored vehicles, well-protected objects (such as bunker) and other engineering structures, as well as enemy personnel and its surface targets. In the summer of 2015, Israel officially recognized the presence of a previously classified form of military equipment – a mobile missile system on the caterpillar chassis of the tank – Pereh. According to Israeli experts, this machine, armed with anti-tank missiles, changes the idea of modern combat. This is the world’s first over-the-horizon anti-tank self-propelled unit. The effective range of these missiles is up to 25 km. The weight of one missile in a transport container is 71 kg. On the flight trajectory, the average speed of the rocket is 130–180 m/s, armor penetration – up to 1000 mm of steel homogeneous armor. These missiles can be effectively used at temperatures from 32 to +49 degrees Celsius and stored at temperatures from 45 to +71 degrees Celsius. Depending on the tasks to be solved, the missile can be equipped with different kinds of warheads – fragmentation, cumulative or multifunctional [7]. Technical solutions are proposed for the improvement of the M60A3 tank called Sabra – the use of a 120 mm gun and a modern digital fire control system. But this model has its own significant drawbacks – homogeneous armor and relatively low mobility [8]. On the basis of experience of the local military conflicts, the theory of modern tank design was developed [9]. According to this theory, in order to dominate the battlefield, a modern tank must meet a number of very important requirements and be created on the basis of the principle of ‘‘six zones”: avoid a collision, avoid detection, avoid escorting, avoid getting, avoid penetration and avoid defeat. The means of protection in the near zone can include a container with anti-aircraft missiles, controlled by the same ‘‘artificial intelligence”. When the tank receives data from the UAV about the use of aircraft weapons against itself, it counterattacks with anti-aircraft guided missiles with a high degree of speed and destroys them when approaching a tank, where ‘‘air control” is carried out by its own on-board radar [10]. In recent decades, numerous theoretical studies have been carried out in the field of modern military equipment and means of its defense. One of the latest examples are some results of the American FCS program (Future Combat Systems). The result of one of the studies within the FCS program was the concept of Survivability Onion or Onion Skin. This concept implies the division of the protection of an armored vehicle into six conventional ‘‘layers”: Avoid Encounter, Avoid Detection, Avoid Acquisition, Avoid Hit, Avoid Penetration and Avoid Kill. Each of them deals with different moments of enemy attack and is associated with the use of certain systems designed to prevent certain enemy actions [11–13]. Also, an elastic polymer is proposed that replicates the ability of the skin of a squid and an octopus: it changes its color and texture of the surface. Camouflage from such an elastomer can hide a soldier or armored car in any situation. Elastomeric camouflage has one drawback: each type of elastomer can only reproduce one pattern of texture and color. The scientists created a simple mimicry camouflage [14]. Utilization of intensity for predicting the distribution of sound in confined spaces has recently been used within computer simulation to represent sound coming from various sources [15]. This creates the possibility of reduction of the amount of information to be computed and makes the simulation system simple enough to be presented on a desktop computer. Availability of new technologies has made it viable to simulate sound distribution in
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confined spaces using pressure, including phase information [16]. Possibilities of simulation are also considered using methods of transforming optics for layers of bending waves within elongated frame constructions [17]. Sound is transmitted through double walls of a cylindrical shell with a steam-tight pad in an active zone, which excites pressure oscillations due to an external turbulent boundary layer [18]. It is proposed to use acoustics of a conformal transformation for creating camouflage devices with layered homogeneous structures that can acoustically generate object illusions [19]. A camouflage coating that can mask an arbitrary object simulating electromagnetic scattering of an empty V-shaped cavity under a metal surface is proposed to be used on the basis of optical conversion. This camouflage device will mislead and confuse detectors and people, and, therefore, any object hidden under this camouflage coating will not be detected [20]. A coherent phantom track method is considered as an illusion of a radar network by controlling several electronic combat vehicles [21]. This paper analyzes the effect of dispersion of electromagnetic parameters and thickness on absorbing material characteristics [22]. Technical supply of masking means for firing and fighting equipment, primarily for open fortifications, is an inevitable problem for a regular army in a combat zone. Idea and structure of this problem are to artificially introduce, in the recording device, changes in means of locating the images of firing and fighting equipment in whole or its individual fragments using a standing screen. The purpose of these actions is to form more or less false (distorted) perception of images of firing and fighting equipment. Solution of this problem will serve as a foundation for implementation of a global strategic advantage: ‘‘To surprise is to win!” The presented work analyzes the advantage of one of the possible technical solutions, namely, the use of ultrasonic devices to create a masking barrier for firing equipment in the form of two coaxial shells separated by fluid [23]. Given a considerable length of outer shell wave being much greater than one, sound waves emitted by the outer shell into fluid at low frequencies, which are below the boundary frequency f lv , occur in the intermediate liquid layer of intershell space and form a closed circuit, the socalled caustic zone, where there is a sharp increase in energetic state of fluid separating the shell. These phenomena occur due to aberration of sound waves emitted by an outer shell into fluid. Availability of wave coincidence provides the maximum energy fraction of ultrasonic radiation directed to creation of a more highly turbulent caustic zone at the resonance level, as a result of the so-called effect of ‘‘acoustic transparency” of the outer shell [24]. The turbulent zone will be perceived by means of location as a set of images of grass, branches, etc. of a battlefield landscape. Thus, the problem of camouflage of armored vehicles appears to be an important component of combat support and the solution of this problem is extremely urgent [25].
3. Materials and methods In the presented paper, one of the technical implementations of camouflage and the limited prominence of fire weapons from aerial reconnaissance is investigated. The open-type fortification on the line of defense in the form of a trench for a tank with a limited firing sector is considered. The trench contains a pit, a ramp (from French appareil) and parapet. It is proposed to cover the trench and the tank with a cylindrical shell of two coaxial fragments separated by a liquid. Moreover, the lower part of the shell is partially submerged in the ground under the foundation pit. By acting on the outer shell with an acoustic beam, in its surface a circular wave is excited that is at a frequency below the boundary wave f bo when the condition of the large wave size of the outer shell is satisfied, i.e.
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1 kR
ð1Þ
where k ¼ c0 is wave number; x is radiation frequency; c0 is speed x
of sound in air; R is radius of outer shell. This will lead to the penetration of radiation inside, those in the sheath of the sound wave separating the shell at an angle of aberration, the angle a (Fig. 1)
cos a ¼
c0 V ob
ð2Þ
where V ob – circumferential velocity in the shell. The aberration created by this condition radiated sound waves will create caustic zone in a liquid in the form of a confocal inner surface of the outer shell with a cross-section in the form of a circle (Fig. 1).
x2 y2 þ ¼1 2 c R cos2 arc sin V 0 R cos2 arc sin Vc0 2
ob
ð3Þ
ob
With the artificial formation of wave coincidence, the caustic zone creates such a degree of turbulence, which will become an insurmountable obstacle to echolocation and on the screen of the sensor only the vague spot will be visible instead of the image with the contours of the tank. Technical specifications of installation are as follows: Power supply: 220 ± 10% V; Network frequency: 50 Hz; Power consumption: NMT 700 ± 10 W; Ultrasound frequency: 35 ± 2.0 kHz. Phenomenon calculations: For ease of perception of the studied phenomenon, the selected material for shells is glass (speed of sound is co = 1497 m/s), and the liquid in the intershell space is ordinary drinking water (V = 5370 m/s). Radius of the outer shell is R = 22.5 mm and radius of the inner shell is R1 = 18.5 mm. Wavelength is:
kR ¼
x ca R
¼ 35; 41 103 ;
ð4Þ
where ca = 331 m/s is the speed of sound in the air. Thus, the requirement 1 << kR for the magnitude of outer shell wavelength is fulfilled; x is the frequency of radiation; Ris the radius of the outer shell, leading to emission inside, that is, into fluid separating the shells, the sound wave at an angle of aberration, the angle a:
sin a ¼
c0 0; 06 V
where V is the velocity of a circular wave in water. Of course, it is possible to use bending waves instead of circumferential, but in this case the periphery of the surface of the tank will be clearly seen on the screen. The main element of the test stand is the generator of acoustic oscillations. Its functions are entrusted to the ultrasonic installation of an industrial sample, which forms an ultrasonic beam with a frequency of 36 kHz (Fig. 2) with a flat wave front. Radiation power is 700 W. The cascade ultrasonic radiator consists of a titanium rod, which is enclosed in a shell of stainless steel, and an ultrasonic generator. A rod is an emitter that converts electrical energy into ultrasonic vibrations. On the rear wall of the generator the output of the network wire is located. The immersion unit is connected to the ultrasonic generator.
ð5Þ
4. Experiments and results The model of the tank is located in a round shell immersed in the water. When the irradiation is off, the contours of the tank layout are clearly visible on the screen (Fig. 3, a). The inclusion of an ultrasonic device forms a circumferential wave in the circumference of the outer shell, which emits a sound wave into the separating fluid between the shells at an angle a to the velocity vector of the circumferential wave. Thus, a cylindrical caustic zone is created in the liquid near the inner surface of the outer shell of the tunnel. The surface of the caustic, in contrast to the static state of the liquid, has an increased energy state, which manifests itself in the form of a turbulent structure (Fig. 3, b). The image of the tank, due to this, gets less clear outlines, but, at the same time, the prominence of the test specimen is sufficient to classify it as a means of fire equipment. Changing the direction of the ultrasonic beam with respect to the outer normal of the outer shell at an angle of incidence 10 degrees the manifestation of a resonant situation is achieved, which is expressed in the form of ‘‘acoustic transparency” of the outer shell. This leads to a significant increase in the power of the ultrasonic beam penetrating the interior of the liquid, practically without dissipation of sound energy, which allows to achieve the desired result, namely - to transform the tank image into a blurred spot on the screen (Fig. 3, c). It is also very important to remove images of locator outlines of serving people in military equipment on the sensor screens. The effect of the invisibility of personnel and material support of fire
a ¼ 3 410
Fig. 1. Formation of caustic zone: R – outer shell diameter, R1 – inner shell diameter.
Fig. 2. Appearance of the test stand.
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Fig. 3. Appearance of the model of the tank exposed to ultrasonic radiation: a) ultrasound generator is disconnected; b) ultrasound generator included; c) direction of the ultrasonic beam changes until the onset of resonance-wave coincidence.
equipment as in the first case is realized in the same volume and in the same quality (Fig. 4). Thus, as it can be seen, the image of the personnel and material support is absent. 5. Discussion The degree of turbulence of the liquid in the caustic zone is maximal when irradiated with an ultrasonic beam at frequencies below the boundary (infrared component, IR radiation). Its effectiveness for solving the tasks of masking the tank and the degree of admissibility of fire weapons in open fortifications directly depends on the angle h between the wave vector of infrared radiation and the outer normal of the outer shell of the enclosing tunnel – known Kremer rule for shells of considerable wave size, when
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Fig. 4. Operating personnel of fire equipment: a) in the absence of artificial irradiation of the installation with an acoustic beam; b) in the absence of a resonant environment in the outer shell; c) offensive of resonance.
kuk the relation (kp ¼ sinh , where kP – circumferential wavelength of outer shell, kuk – circumferential wavelength of infrared radiation) about the necessity of equality of the trace of the incident infrared ray and the circumferential wave of the outer shell, the so-called coincidence angle h. That is, depends on the proximity of the presence of the wave vector of radiation to the resonance zone of wave coincidence – geometric resonance. The circuit under analysis obviously does not build the second caustic zone, but already flexural oscillations of the outer shell, which are known to occur at frequencies above the cut-off frequency. If bending vibrations formed a caustic zone, then the radius of the cylindrical caustic zone realized by the bending waves would, as it is well known, be much less than the radius of the cylindrical caustic from the infrared ray (if there was liquid inside the enclosing tunnel). But, since the liquid is only between the
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outer and inner shell of the enclosing tunnel, and inside the safety tunnel there is no liquid, and air is present, then the second caustic at high frequencies cannot be formed in this construction. Experimental semi-detailed studies were carried out on a tank model located in a shielding tunnel of a modular construction of two coaxial cylindrical shells separated by a liquid. Irradiation of the outer shell with ultrasound at a frequency of 36 kHz with the help of the UZP-6-1 device of the Ukrainian production made it possible to confirm the theoretical justification for the possibility of masking fire equipment in open fortifications - near the resonance region (wave coincidence), and also in the zone of geometric resonance, when the trace of the emitter wave and the circumferential wave of the outer shell coincide (Kremer’s rule). In the photographs of the experiment presented in the manuscript, the second image corresponds to the finding of radiation near the resonance region of the wave coincidence, the third photograph shows the result of masking the mock-up of the fire equipment in the resonance region of the wave coincidence. It is obvious that the resonance zone provides maximum turbulence of the caustic surface in the inter-shell space and, thus, ensures the fulfillment of the requirements of limited prominence and absolute camouflage of the investigated object of fire equipment. The result of the semi-full-scale tests satisfactorily confirms the predicted situation of aberration of sound waves emitted by the outer shell into the liquid and the formation, with their help, of the surface of the cylindrical caustic zone, which forms the maximum possible turbulence of the fluid of the interlobar space of the enclosing tunnel and serves as a sufficient technical means for demanding complete masking of defense equipment. The above photographs show that finding the beam of an ultrasonic radiator near the resonance region of wave coincidence allows only a slight distortion of the prominence of the contours of the fire equipment, as well as its surface, at which the main details of the weapons will be still seen quite well by the means of the location of air and space reconnaissance. By displacement of the direction of the ultrasonic beam into the resonance zone, when the trace of the incident wave and the circumferential wave of the envelope coincide, it makes it possible to increase the energy state of the liquid to a value providing complete masking of the product and blurring its contours to an indefinite form. The photographs are quite convincing confirmation of the theoretical premises. Further deepening of research, their specification to certain classes of fire equipment should be carried out at defense enterprises in a certain sequence – experimental design development, factory testing of fire equipment, state testing of fire equipment. For understandable reasons, the coverage of this information is the prerogative of the respective enterprises. 6. Conclusions The possibility of securing the disguise of fire weapons in fortified structures of an open type line defense against enemy air reconnaissance based on the use of resonant phenomena in acoustic media is presented in the paper. The values of the necessary parameters of the laboratory installation are numerically established - wave size, wave coincidence and zones of the caustic of the phenomenon being investigated. The possibility of masking not only military equipment on positions, but also the military units of the logistical support is discussed. The technical decision taken to ensure the necessary level of camouflage and admissible fidelity of the defense line weapons, tested on a laboratory installation, opens the possibility for further expansion and deepening for the proposed technical solution in combat conditions. First of all, this is connected with the possibility of remote control and regulation of military equipment and logistical support not only in positions, but also in the course of hostilities.
The proposed technical solution allows to significantly influence the level of unexpected use of firearms in combat conditions, and also to form false fortifications of an open type with remote control on the line of defense, which can also serve as an advantage of the defending side and the isolation of echolocational means of aerial reconnaissance. The semi-real tests, carried out with the material for the practical implementation of the camouflage of firearms on the defense line of open fortifications, gave satisfactory results. At this stage, the consent of the special design bureau for carrying out experimental design work in terms of tasks assigned and the Act on the implementation of the results of theoretical studies of authors was signed. For known reasons, the details and depth of disclosure of raised issues cannot be covered in the open access, therefore the authors explain this reason for the incomplete measure of disclosure of practical results.
Funding This research was funded by the statutory funds of the Institute of Metrology and Biomedical Engineering, Warsaw University of Technology.
Conflicts of interest The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of the data, in the writing of the manuscript, or in the decision to publish the results.
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