FI129961B

FI129961B - Sea mine

Info

Publication number: FI129961B
Application number: FI20187034A
Authority: FI
Inventors: Roope Kotiranta
Original assignee: Surma Oy
Priority date: 2017-12-01
Filing date: 2018-03-12
Publication date: 2022-11-30
Also published as: EP3717861A1; ES2927545T3; FI20187034A1; EP3717861B1; EP3717861A4

Abstract

The invention provides a sea mine (100) that can detect the direction of a target and produce a directed explosion towards the target. The sea mine comprises at least a detector arrangement (140) for detection of a vessel, a control unit (130) for determining the direction of a detected vessel, an arrangement (150) for producing a directed shock wave, and an arrangement (160) for directing a shock wave towards the direction of a detected vessel.

Description

Sea mine

BACKGROUND OF THE INVENTION

Sea mines are explosive devices which are utilized in maritime environment with the intention to severely damage or sink target vessels. Sea mines can roughly be divided into three categories, namely contact mines, remotely operated mines and influence mines. As the name implies, contact mines are triggered by the contact between the mine and the vessel. This means that contact mines are usable only in relatively shallow waters and narrow fairways. Contact mines are considered to be old technology, as they are relatively easy to detect and dispose of. Remotely operated mines are triggered by the operator, when a target vessel is in a suitable position. This means they can only be used effectively in situations when the minefield can be observed. Nowadays the most used mine type is the influence mine, which normally uses several different sensors to detect and identify the target vessels and computerized logic to decide when to detonate. The typical sensors used in influence mines include acoustic, magnetic and pressure sensors. The computerized logic utilizes algorithms to characterize detected vessels and optimize the time of detonation.

The damaging effects of a sea mine detonation can basically be separated into three different phenomena: the initial shock wave and its reflections, the low frequency gas bubble pulsation, and the water jet effect. . The initial shock wave is imparted to the water from the detonation and travels in

N the water with the speed of sound as a thin high pressure front and reflects from all

N encountered surfaces like sea bottom and free surface. As the shock wave (or a 3 reflected wave) hits the target, it causes violent transient loading on the under water = 30 part of the vessel. This loading can rupture the shell plating and always induces a

I structural shock wave which inflicts damage upon structures, equipment and 5 personnel as it travels through the vessel. 0

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© The low frequency gas bubble pulsation is caused by the hot gaseous detonation a 35 products, which expand and shrink as a bubble when migrating up towards the free surface. This oscillation causes low freguency pressure pulses, typically of the order of few Hertz, which might excite the lowest bending modes the vessel’s hull girder,

if the pressure pulses are high enough and the frequency is close to vessel’s natural frequency.

The water jet effect is caused by the collapse of the gas bubble, when in vicinity of a surface. This effect may rupture the shell plating and severely damage the exposed part of the structure. However, this effect requires proximity of the vessel, e.g. contact or detonation directly below the vessel.

Since a large damaging power is needed, existing sea mine constructions typically — are large and heavy. The size and weight of the sea mines require heavy machinery for handling the sea mines. The large size and weight limit the number of mines a mine laying vessel can carry. Lighter and smaller mines would be desirable.

Some solutions providing for lighter mines have been presented in prior art. Patent

US4274333 describes a target-seeking mine. Patent publication FR2874253A1 describes a mine with a directional explosive. Patent US5033354 describes a device with a target detection system. Patent publications GB2251220A and

DF3238229A1 describe mines that approach the target.

SUMMARY OF THE INVENTION

An objective of the invention is to enhance the primary damage effect of a sea mine, namely the initial shock wave, by utilizing its explosive energy in a more efficient manner.

N A further objective of the invention is to provide sea mines, that are lighter than

N conventional sea mines with comparable destructive power. 3 = 30 These objectives are reached by focusing the detonation waves to form a directed

I shock wave or, in other words, a shock beam instead of letting the explosive energy 5 radiate spherically, and by directing the shock beam towards the target vessel. The

S correct direction can be defined based on normal influence mine sensor data and the © shock beam can be directed at the target by various different means described later i 35 on in this specification.

This arrangement yields a cone shaped shock wave with characteristically higher energy density at the target vessel, than that resulting from a conventional sea mine.

The above summary relates to only one of the many embodiments of the invention disclosed herein and is not intended to limit the scope of the invention, which is set forth in the claims herein. These and other features of the present invention will be described in more detail in the following in this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be described in detail below, by way of example only, with reference to the accompanying drawings, of which

Figure 1 illustrates the structure of a sea mine according to an embodiment of the invention,

Figure 2 illustrates a cutout diagram of an explosive charge according to an embodiment of the invention,

Figure 3 illustrates an explosion lens structure according to an embodiment of the invention,

Figure 4 illustrates a structure of a charge according to an embodiment of the invention,

Figure 5 illustrates a structure of a charge according to a further embodiment of the . vention,

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N Figure 6 illustrates the structure of a sea mine according to an embodiment of the 3 invention, and

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I Figure 7 illustrates an embodiment of the invention using a spherical structure.

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The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s), this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may be combined to provide further embodiments.

In the following, features of the invention will be described with a simple example of a sea mine with which various embodiments of the invention may be implemented. Only elements relevant for illustrating the embodiments are described in detail. Details that are generally known to a person skilled in the art may not be specifically described herein.

Figure 1 illustrates a block diagram of a sea mine according to an embodiment of the invention. Figure 1 shows a sea mine 100 a body 110 of the sea mine, and an anchor 120 or a weight 120 on the sea bottom 195. The anchor is connected to the body 110 of the sea mine with a cable 121, a chain 121, a rope 121 or another similar connection member 121.

Figure 1 also shows a control unit 130, a sensor system 140, an arrangement 150 for producing a directed shock wave, and an arrangement 160 for directing a shock wave to a desired direction. Various examples of these are discussed in more detail later in this specification.

Although figure 1 shows the anchor as being a separate object from the body of the sea mine and connected to the body of the sea mine with a cable, a chain, a rope or similar, this is only one example of various configurations of how the anchor can be implemented. For example, in further embodiments of the invention the anchor can — be integrated in the body of the sea mine.

N In the following, we describe certain embodiments of the invention.

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3 Next, we describe in more detail certain major functional features of a sea mine = 30 according to an embodiment of the invention. These major functional features

I described in the following are detecting and determining the location of a target 5 vessel with respect to the location of the mine; focusing the shock wave from the

S explosion of the mine to form a shock beam; and directing the focused shock wave © caused by explosion towards the target vessel in an efficient manner.

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Detection of a target vessel and determination of the location of the target vessel with respect to the location of the mine can in various embodiments of the invention be implemented in different ways. For example, detection and location determination can be implemented using acoustic sensors, which are known by a man skilled in the art, and commonly used in influence mines for detection of vessels. 5 The needed directional angles describing the direction of the target vessel as observed from the mine can be determined by at least two ways. For example, by arranging a plurality of sensors in two arrays on the body of the mine or to an extension boom attached to the mine, and calculating the directional angles from the differences of the received signal and the distances of the sensors. In an embodiment which comprises a sensor that can determine distance to the observed vessel, the vertical (attitude) angle can be determined from the depth of the mine and the distance of the observed vessel.

Focusing the shock wave from the explosion of the mine to form a shock beam can be achieved in various ways. In one embodiment of the invention, the focused explosion is created with the aid of a so-called explosion lens. An explosion lens can be implemented for example using a shaped charge such as the one illustrated in figure 2. Figure 2 illustrates a cutout diagram of a charge, where a heterogeneous explosive 310 is shaped in a cone-like and partly convex manner. When the — explosive is detonated with a detonator 320 situated close to the narrow end of the cone-shaped depression, the resulting blast wave front is highly directional.

In a further embodiment of the invention, an explosion lens is implemented using a metal ring structure as shown in figure 3. Figure 3 illustrates the structure of a directional charge, which comprises two cylindrical charges 410, 411 and a metal . ring 420 and a pocket of air or gas 425 between the cylindrical charges 410, 411.

N Figure 3 also shows a detonator 430 and a booster explosive 432 for igniting the

N detonation of the whole structure. 3 = 30 When the detonator 430 and the booster explosive 432 start the detonation, the

I shape of the detonation front within the first cylindrical charge 410 is roughly 5 spherical. The air-metal barrier between the cylindrical charges affects the shape of

S the detonation front, when the detonation front travels from the first cylindrical © charge 410 to the second cylindrical charge 411. This causes the shape of the

N 35 detonation front, when it finally reaches the outward end 411A of the second cylindrical charge, be non-spherical enough to produce a directed blast wave.

Figure 4 illustrates a structure of a charge according to a further embodiment of the invention. Figure 4 illustrates a spherical charge 500 comprised of a plurality of spherically concentric layers 510 of explosives with different detonation speeds.

After ignition by detonator 530, the detonation front initially travels spherically from the initiation point, but the different layers of explosives 510 with different detonation speeds affect the shape of the detonation front. Dashed lines 520 indicate schematically the shape of the detonation front at various times after ignition by detonator 530. When the detonation front reaches the surface of the charge 500 at a point opposite to initiating detonator 530, a blast wave is created. The shape of the detonation front causes the blast wave to be directed.

Figure 4 illustrates only an example of an arrangement of explosives with different speeds of detonation suitable for producing a directed blast wave. Many variations of such a structure are possible. For example, a plurality of detonators 530 can be applied to the charge 500, and the shape of the detonation front be determined by the time sequence of detonation of the detonators 530.

Figure 5 illustrates another structure of a charge according to a further embodiment of the invention. Figure 5 shows a cutout diagram of a spherical charge 810 having — a spherical inert layer 820 of e.g. metal or a combination of metal 821 and air 822 between an explosive outer layer 830 and an explosive inner core 840. As in the example of figure 3, the inert layer 820 affects the shape of the detonation front when the front travels starting from one or a plurality of detonators 530 on the outer layer 830 to the inner core 840 in order to produce a directed blast wave. . Figure 5 shows a plurality of detonators 530 at different locations of the outer layer

N 830 for initiating the explosion. The shape of the detonation front can be affected

N by selection of one or more detonators to fire, and the timing and the order of firing 3 of the detonators. Consequently, the direction of the blast wave created by the = 30 structure shown in figure 5 can be affected by selection of one or more of the

I detonators 530 for firing, and the timing and the order of firing of the selected 5 detonators.

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N 35 more sublayers of explosives with different detonation speeds in order to further affect the shape of the detonation front.

In a further embodiment of the invention the inner core 840 can comprise one or more layers of explosives with different detonation speeds in order to further affect the shape of the detonation front.

Directing the focused shock wave caused by the detonation of the mine towards the target vessel can be implemented in various ways in different embodiments of the invention.

Figure 6 illustrates a sea mine according to an embodiment of the invention. Figure 6 shows a a simplified diagram of a sea mine 100. The sea mine 100 comprises a body 110 connected by a cable 121 to an anchor 120 which keeps the sea mine in place on the sea bottom 195. The body of the mine comprises a propulsion energy source 610 such as an air or gas tank 610, an explosive device 620, propulsion devices 630, 631 such as nozzles for changing the positional angles of the sea mine body, a sensor and control unit 640 and a casing 650.

The sensor and control unit 640 comprises one or more sensors and a control unit for detection of a target vessel and determining the direction of the vessel, and for controlling the propulsion devices 630, 631 to change the positional angles of the — mine body, i.e. turn the body of the mine towards the determined direction. The explosive device 620 is then detonated by the control unit in order to produce a directed blast wave in the determined direction.

In an embodiment of the invention the propulsion is based on compressed gas such — as air or nitrogen or any other gas which is readily available for such a purpose. In . such an embodiment, the propulsion devices are nozzles which exert a reaction

N force on the body of the mine when gas is led through the nozzle, and the

N propulsion energy source 610 is a gas tank 610. 3 = 30 In a further embodiment of the invention, the elevation and azimuth controls 630,

I 631 are implemented using electrical propulsion. In such an embodiment the mine 5 comprises an electrical power source 610 such as a battery 610 instead of an air or

S gas tank, and electrically powered thrusters 630, 631 instead of nozzles. 0 a 35 In a further embodiment of the invention the physical turning of the sea mine towards the target is implemented using a spherical construction. Such an embodiment is illustrated in figure 7. Figure 7 shows a half spherical charge 710 which produces a directed blast wave when detonated, set in a protective spherical casing 720. The half spherical charge 710 can be rotated within the protective spherical casing 720 using e.g. an electrically or pneumatically driven mechanism in order to control the direction of the blast wave.

Figure 7 also shows a base 730 which functions as an anchor, and comprises a sensor and controller unit for detection of a target vessel and determination of the direction of the target vessel. The controller unit also controls turning of the charge 710 so as to point the resulting directional blast wave towards the target vessel, and ignition of the explosive charge.

Directing the focused shock wave caused by the detonation of the mine towards the target vessel can in certain embodiments of the invention be implemented by selecing which detonator to ignite or which sequence of detonators to ignite, instead of physically turning the body of the sea mine towards a desired direction. As described previously with reference to figure 4, an embodiment of the invention can use a an explosive charge that is able to produce a directed blast wave in different directions depending on which detonator is ignited first, and/or which sequence of ignition of a plurality of detonators is applied. In such an embodiment, the control of the direction of the blast is implemented through selection of detonator or detonator ignition sequence by the control unit in the mine.

The inventive sea mine yields a cone shaped shock wave with characteristically higher energy density at the target vessel, than a shock wave resulting from a conventional sea mine having a similar amount of explosive. . This brings the benefit of the mine having a smaller size for eguivalent damage

N potential compared to traditional sea mines. This further makes the inventive sea

N mines easier to store and handle than traditional sea mines of equivalent damage 3 potential, whereby existing mining ships can store and carry a larger number of the = 30 inventive mines. = 5 In the following, we describe certain further embodiments of the invention. In an

S embodiment of the invention, a sea mine comprises at least a detector arrangement © for detection of a vessel, a control unit for determining the direction of a detected a 35 — vessel, an arrangement for producing a directed shock wave, and an arrangement for directing a shock wave towards the direction of a detected vessel.

In a further embodiment of the invention, said arrangement for directing a shock wave comprises at least an arrangement for changing a positional angle of at least a part of the sea mine, and a control unit for controlling said arrangement for changing a positional angle, and said control unit is arranged to change a positional angle of at least a part of the sea mine to direct the shock wave of the mine towards the direction of a detected vessel.

In a further embodiment of the invention, said arrangement for changing a positional angle of at least a part of the sea mine comprises gas thrusters.

In a further embodiment of the invention, said arrangement for changing a positional angle of at least a part of the sea mine comprises electrically driven propulsion units.

In a further embodiment of the invention, said arrangement for directing a shock wave comprises at least a control unit arranged to select one or more detonators of a plurality of detonators to ignite.

In a further embodiment of the invention, said control unit is arranged to ignite a plurality of detonators in a predetermined time sequence, and to select said plurality of detonators to ignite in said predetermined time sequence in order to direct a shock wave in a desired direction.

In view of the foregoing description it will be evident to a person skilled in the art — that various modifications may be made within the scope of the invention. While a i preferred embodiment of the invention has been described in detail, it should be

N apparent that many modifications and variations thereto are possible, all of which

N fall within the true spirit and scope of the invention. 3 = 30 It is to be understood that the embodiments of the invention disclosed are not

I limited to the particular structures, process steps, or materials disclosed herein, but 5 are extended to equivalents thereof as would be recognized by those ordinarily

S skilled in the relevant arts. It should also be understood that terminology employed © herein is used for the purpose of describing particular embodiments only and is not a 35 intended to be limiting.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such — list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the . invention.

N While the foregoing examples are illustrative of the principles of the present 3 invention in one or more particular applications, it will be apparent to those of = 30 ordinary skill in the art that numerous modifications in form, usage and details of

I implementation can be made without the exercise of inventive faculty, and without 5 departing from the principles and concepts of the invention. Accordingly, it is not

S intended that the invention be limited, except as by the claims set forth below.

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Claims

1. Sea mine (100), having an anchor (120, 730) for keeping the sea mine in place on the sea bottom, a detector arrangement (140) for detection of a vessel, a control unit (130) for determining the direction of the detected vessel, an arrangement (150) for producing a directed shock wave, and an arrangement (160) for directing a shock wave towards the direction of the detected vessel, — characterized in that said arrangement for directing a shock wave comprises at least the control unit (130) arranged to —- select one or more detonators (530) of a plurality of detonators to ignite, and - ignite the selected detonators (530) in a predetermined time sequence in order to direct a shock wave in a desired direction. N QA O N o <Q MN O I a E 0 O N 0 O N