Autonomous double-circuit magnetocumulative radiofrequency generator

Abstract

This utility model relates to pulsed electrophysics and the generation of high-power radio-frequency pulses using explosive energy. The technical result is an increase in the penetration depth of radio waves during radar probing of media. A generator is proposed for this purpose, comprising two coupled oscillatory circuits with coaxial solenoids and a common coupling capacitor. A conical metal liner containing an explosive charge is coaxially positioned within these circuits, providing a high-frequency electrical current beat mode during an explosion. Powerful permanent magnets are installed around each solenoid, creating an autonomous initial magnetic flux. The capacitors of the circuits are adjustable for adjusting the radiation frequency before detonation. The liner has an adjustable wall cone angle to adapt to the detonation velocity of a specific explosive type. The solenoid windings have a variable pitch, decreasing as the detonation progresses. 1 fig.

Description

[0001] This utility model pertains to the field of pulsed energy, specifically to autonomous sources of powerful radiofrequency and ultrahigh-frequency (UHF) radiation based on magneto-cumulative generators (MCGs). These devices convert the chemical energy of explosives into a powerful electromagnetic pulse.

[0002] The creation of compact, ultra-powerful, and fully autonomous radio emission sources is a critical task for modern scientific research instrumentation. The main applications of such systems include:

[0003] 1. Deep ground penetrating radar (GPR) of the earth's interior – for the rapid search for minerals and hidden tectonic faults in hard-to-reach areas without the deployment of heavy stationary stations.

[0004] 2. Space exploration of near and deep space - radio probing of the structure of asteroids, comets and the icy shells of natural satellites of planets (for example, Europa or Enceladus) from orbital, descent or impact scientific research probes (penetrators).

[0005] Currently available explosive radio frequency current generators face a number of severe physical and engineering limitations that significantly reduce their practical value:

[0006] 1. The problem of inefficient energy dissipation: at the final stage of liner collapse, classic single-circuit circuits lose a colossal portion of their energy as heat due to a drop in inductance and an avalanche-like increase in skin-layer resistance.

[0007] 2. The problem of rigid attachment to the explosive type: the geometry of the generator's internal components is calculated for a single, strictly defined detonation velocity, which precludes the possibility of quickly loading the device with other types of explosive compositions in field or expeditionary conditions.

[0008] 3. The problem of lack of environmental adaptability: different geological environments (dry ice, granite, wet soil) have radically different radio wave attenuation coefficients. Existing MCG systems generate a fixed-frequency signal that cannot be optimized for the specific physical properties of the object being studied, resulting in the radio wave either being completely absorbed by the environment or not providing the required resolution.

[0009] 4. Dependence on power infrastructure: the need to use bulky external capacitor banks to create a starting ("seed") magnetic field negates the advantage of the compactness of the explosive generator itself during its autonomous reset.

[0010] 5. Thus, the urgent task is to develop a fully autonomous, energy-efficient explosive radio wave source with the ability to quickly adjust its frequency parameters and geometry to changing environmental conditions and the characteristics of the explosive used.

[0011] A self-contained magnetocumulative generator is known, which contains a cylindrical cavity of explosive compression, inside which a conical expandable liner (conductor) with an explosive charge is coaxially placed. The cavity is surrounded by a solenoid (spiral inductor), connected to an electrical circuit. Permanent magnets are arranged radially around the solenoid, which create an initial (seed) magnetic flux inside the cavity. When the explosive charge is detonated, the liner expands, deforms the solenoid turns and compresses the magnetic flux, converting the kinetic energy of the explosion products into a powerful current pulse (patent RU No. 2 260 896 C1, IPC H03K 3 / 38, published 20.10.2005).

[0012] The disadvantages of such a generator are:

[0013] 1. Low efficiency of energy conversion into radio frequency radiation. The known device is a single-circuit generator of a quasi-constant or monotonically increasing current pulse. It is incapable of directly generating high-frequency oscillations (radio waves) without the use of complex external microwave units or explosive current interrupters. In the final stage of compression, when the solenoid inductance approaches zero, most of the accumulated energy is converted into heat due to count-joule losses in the skin layer, never being transformed into useful radiation.

[0014] 2. Strict limitations on peak power. The radial arrangement of permanent magnets around the solenoid limits the maximum initial magnetic induction to the physical properties of magnetic materials (usually no more than 1.2-1.5 T). Due to the fixed geometry of the solenoid and liner, the device is unable to effectively compress the process time to the nanosecond range, preventing the achievement of gigawatt peak radio emission powers necessary for deep probing of dense celestial bodies or the Earth's interior.

[0015] The closest technical solution (prototype) is a magneto-cumulative generator containing two coaxially located solenoids, inside which an expandable metal conical liner filled with an explosive charge is coaxially placed, and two coupled oscillatory circuits with a common coupling capacitor, forming a mode of electrical beats of high-frequency current (patent for utility model RU No. 157 383 U1, IPC H03K 3 / 38, published 11 / 27 / 2015).

[0016] The disadvantages of the prototype are:

[0017] 1. Lack of autonomy and high weight due to external power systems. The prototype design lacks built-in sources of a constant magnetic field. To generate the initial (seed) magnetic flux in the solenoids, the device requires a bulky external source—a high-capacity capacitor bank. This makes it impossible to use the generator as a fully autonomous probe (for example, when dropped from a spacecraft onto the surface of an asteroid).

[0018] 2. Inability to adapt to the physical properties of the environment being studied. The capacitors in the prototype circuit have a fixed electrical capacitance, which rigidly sets the carrier frequency of the radio emission ω0 and the beat frequency ω. When studying planets or subsurfaces with unknown or changing soil characteristics, a fixed frequency leads to severe signal attenuation or a loss of radar resolution.

[0019] 3. Rigid binding to a single explosive type. The prototype liner has a constant, fixed cone angle. Effective energy accumulation is only possible when using explosives with a strictly defined detonation velocity. When changing the explosive type (for example, when loading the generator with available surrogate compositions in the field), the synchronization between the liner movement and the current buildup is disrupted, leading to a drop in efficiency.

[0020] 4. Limited inductance rise rate. The prototype solenoids are designed with a constant turn pitch. With this design, the rate of inductance decrease dL / dt during turn deformation is linear, which limits the maximum current pulse rise time and prevents the emission spectrum from shifting to a higher frequency (microwave) range for precision location.

[0021] The problem, which the proposed utility model is aimed at solving, is the creation of a fully autonomous explosive radio frequency generator, capable of flexibly adapting to the physical properties of the probed environment and the characteristics of the explosive used immediately before use, while simultaneously increasing the steepness of the front of the generated pulse and the overall efficiency of the device.

[0022] The technical result of the proposed utility model is an increase in the penetration depth of radio waves during radar probing of environments.

[0023] The problem is solved and the technical result is achieved by the fact that in a dual-circuit magneto-cumulative radio frequency radiation generator, containing two coaxially located solenoids, inside which an expandable metal conical liner filled with an explosive charge is coaxially placed, and two coupled oscillatory circuits with a common coupling capacitor, forming a mode of electrical beats of a high-frequency current, according to the utility model, permanent magnets are coaxially installed around each solenoid to create an autonomous initial magnetic flux; the capacitors of the coupled oscillatory circuits are made adjustable with the possibility of changing their electrical capacitance before the device is triggered; the conical liner is made with the possibility of adjusting the angle of the cone of its wall to the detonation speed of a specific type of explosive;the winding of the turns of the first and second solenoids is made with a variable pitch, progressively decreasing in the direction of the detonation wave.

[0024] The essence of the device is shown in the figure. The magneto-cumulative generator consists of an explosive charge 1, a metal liner 2 (shaped like a truncated cone), an air gap 3 (in which the liner expands), solenoid windings 4 (the pitch of which decreases in the direction of detonation), powerful permanent magnets 5, magnetic cores 6, and adjustable capacitors C1, C2, C3.

[0025] The magneto-cumulative radio frequency generator works as follows.

[0026] In the initial state, the permanent magnets 5, through the end magnetic circuits 6, create a stable longitudinal (axial) magnetic flux in the air gaps 3 of both solenoids.

[0027] The explosive charges 1 are initiated synchronously from the outer (wide or narrow, depending on the initiation scheme; in this case, from the ends) directions. Under the action of the explosion products, the metal liners 2 begin to coaxially expand into the air gap 3.

[0028] Expanding metal liners 2 sequentially, turn by turn, short-circuit the windings of solenoid 4. Due to the progressively decreasing pitch of the winding of solenoid 4 toward the center, the rate of decrease in inductance dL / dt increases nonlinearly in the final stage of compression. The magnetic flux forced out of gap 3 induces an avalanche-like increase in high-frequency current. The electrical power is determined by the formula

[0029] (1)

[0030] where I is the current in the winding, t is the time elapsed from the moment the field compression begins. The power increases sharply at the final stage of compression due to the growth of the derivative modulus. which is ensured by the mentioned reduction in the pitch of the winding turn.

[0031] Calculating the optimal cone angle of the liner for a specific type of explosive is produced according to the Knopfel ratio

[0032] (2)

[0033] where D is the detonation velocity of the explosive (for example, for hexogen m / s); - the speed of the liner's takeoff, which is determined by the Gurney formula

[0034] (3)

[0035] where E is the specific energy of the explosive (for example, for hexogen kJ / kg); - liner mass; - mass of explosives.

[0036] Formulas (2)-(3) allow you to find the optimal liner angle for a specific type of explosive, which, in turn, will increase the efficiency of energy use of this explosive.

[0037] Peak pulse power is also increased by the use of permanent magnets, which create a static, perfectly symmetrical, and uniform axial field, increasing the circuit's Q factor and ensuring maximum efficiency in the beat mode. Furthermore, thanks to the use of permanent magnets, the magneto-cumulative generator becomes completely autonomous and does not require an external power source to generate the "seed" current, eliminating parasitic losses in the supply cables and eliminating dynamic losses due to field diffusion into the metal before cumulation begins.

[0038] Due to the presence of two coupled circuits with a common coupling capacitor C3, intense electrical beats are generated in the system. The deformation energy is effectively transferred into the electromagnetic field, transforming it into a powerful frequency-modulated radio wave packet emitted by the solenoids directly into the surrounding space (the medium being studied).

[0039] Before using the device, the carrier frequency and beat frequency are adjusted by changing the capacitance of the adjustable capacitors C1, C2, C3 (for example, by switching matrices of high-strength capacitors) to suit the physical parameters of the probed environment.

[0040] The adjustable capacitors are adjusted to ensure maximum spatial resolution of the radar (corresponding to the minimum wavelength) with guaranteed reception of the reflected signal from a depth of H, which is mathematically expressed through maximizing the operating frequency ω б , satisfying the criterion of electrodynamic attenuation in a medium with specific conductivity σ.

[0041] The beat frequency is determined by the formula

[0042] (4)

[0043] where - the frequency of free electrical oscillations in circuits. At a given power radio signal from the MCG and a given thickness of the medium H, for the radio signal reflected from the interface between the media, the condition must be met

[0044] (5)

[0045] where - the minimum radio emission power required for its registration by the receiving station; - reflection coefficient from the interface between the media; H - depth at which the interface between the media is located; - the rate of attenuation of a radio signal in a specific environment, depending on the beat frequency and from the parameters of the given environment

[0046] (6)

[0047] where σ is the specific permittivity of the medium, cm / m; ε is the relative permittivity of the medium; ε0 is the electric constant; μ0 is the magnetic constant. Using formulas (4)-(6), it is possible to select such values ​​of capacitance of the adjustable capacitors C1, C2, C3, at which radar detection to a given depth H is possible with given parameters of the studied medium (σ, ε), while ensuring the highest possible radar resolution under these conditions.

[0048] Thus, optimizing the liner angle using formulas (2)-(3) maximizes the efficiency of converting explosive energy into radio energy. Combined with reducing the pitch of the solenoid windings in the direction of detonation propagation, this allows for an increase in the radio power from the MCG (P МКГ ) in accordance with formula (1) due to the concentration of the specified radiation energy over time at the final stage of compression.

[0049] The penetration depth of radio waves during radar probing of environments is determined from condition (5). The penetration depth of radio emission increases due to the increase in the radio emission power P МКГ and by optimizing the frequency of radio emission according to the criterion of minimizing the attenuation of radio emission in a specific environment while ensuring the required radar resolution.

[0050] Thus, the proposed utility model ensures an increase in the penetration depth of radio waves during radar probing of environments due to a combination of the indicated essential features.

Claims

A dual-circuit magneto-cumulative radio-frequency radiation generator comprising two coaxially arranged solenoids within which an expandable metal conical liner filled with an explosive charge is coaxially positioned, and two coupled oscillatory circuits with a common coupling capacitor, which form a mode of electrical beats of a high-frequency current, characterized in that permanent magnets are coaxially mounted around each solenoid to create an autonomous initial magnetic flux; the capacitors of the coupled oscillatory circuits are made adjustable with the possibility of changing their electrical capacitance before the device is triggered; the conical liner is made with the possibility of adjusting the angle of the cone of its wall to the detonation velocity of a specific type of explosive; the winding of the turns of the first and second solenoids is made with a variable pitch, progressively decreasing in the direction of travel of the detonation wave.

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