Patent Publication Number: US-2021180929-A1

Title: Device and method for obtaining a horizontal dispersion pattern

Description:
BACKGROUND AND SUMMARY 
     The present invention relates to the field of spin stabilized projectiles comprising a releasable payload and dispersion patterns, more particularly to horizontal dispersion patterns suitable for combatting surface targets. 
     Direct fire refers to the launching of a projectile directly at a target within the line-of-sight of the firer. Projectiles used in direct fire usually transport various payloads for various purposes and various uses, such as surface to surface, surface to air, and air to air. The Phalanx CIWS (Raytheon) is a close-in weapon system for defence against anti-ship missiles. The system comprise optimized gun barrels (OGB), and Enhanced Lethality Cartridges (ELC) for additional capabilities against asymmetric threats such as small manoeuvring surface craft, slow-flying fixed and rotary-winged aircraft, and unmanned aerial vehicles thus providing tighter dispersion and increased “first-hit” range. The rounds are armour-piercing tungsten penetrator rounds or depleted uranium with discarding sabots. 
     U.S. Pat. No. 4,002,121 discloses a ballistic projectile comprising an incendiary-type payload for a heavy duty ballistic projectile. The payload is comprised in a plurality of payload containers successively disposed between the nose and tail sections of the projectile and the payload containers are ejected from the tail in a scattered ring-like area of the targeted terrain and remain intact upon impact with the target terrain. 
     U.S. Pat. No. 5,817,969 discloses a spin-stabilized projectile containing a payload chamber comprising sub-projectiles that are released via the chamber wall when the payload chamber opens along a casing line from the bottom to the top (cap). The dispersion pattern is circular, which is suitable for air targets but less suitable for surface targets. The construction of the carrier shell is complex and the aim is to fill the casing with maximum number of sub-projectiles for improved hit rate, i.e., quantity. The drawbacks by prior art is that the high number of sub-projectiles makes the projectile heavy, and the circular dispersion pattern provides a quite low hit rate close to ground or water when sub-projectiles going upward into the air or downward hitting the ground early are wasted and may increase the risk for collateral damage. 
     In view of the background art there is a need of developing improved devices and methods that enable a horizontal dispersion pattern, thereby providing increased hit rate and efficiency, and decreased risk for unintended damage to the surroundings. 
     It is desirable to provide a device for providing a horizontal dispersion pattern i.e., a payload container. 
     The payload container according to an aspect of the present invention is in the form of a cylinder. The container comprises at least two sub-projectiles arranged in a core. The core can be of any suitable material. The core and the sub-projectiles are enclosed by a container wall. The container wall may be a part of the core, i.e., the sub-projectiles are embedded in and enclosed by the core material. 
     The at least two sub-projectiles are arranged in a line. The sub-projectiles are linearly disposed along a cord. The sub-projectiles can be arranged in more than one line. The sub-projectiles may also be disposed in at least two parallel lines or cords. The sub-projectiles can be arranged in more than one line, along a cord. 
     The sub-projectiles may be disposed in at least two layers. The layers are substantially arranged in one plane. 
     The orientation of the sub-projectiles is vertical when the sub-projectiles are released from the payload container against a target. 
     The number of sub-projectiles arranged in one payload container depends on the type and aim of the projectile. The number may be in the range of 2-1000 sub-projectiles. 
     In one aspect the sub-projectiles may be any of flechettes, rods, balls, spheres, discs, cubes or hexagons. In another aspect the sub-projectiles may be a combination of different kinds of payload, sub-projectiles. 
     In yet another aspect the sub-projectiles may be made of hard metal or heavy metal. 
     In one embodiment, the at least one payload container is arranged to at least one more payload container, forming a stack of containers. The first payload container (A) is displaced in relation to the second payload container (B). The displacement φ of the containers results in that the direction of sub-projectiles in the first container (A) is not the same as the direction of the sub-projectiles in the second container (B). The displacement angle φ results in that the sub-projectiles in respective payload container is in a vertical direction when the mechanical force from the projectile wall disappears, resulting in a horizontal dispersion pattern. The angle φ between the payload containers is predetermined. 
     The number of payload containers in a stack depends on the aim of the projectile. In one embodiment the number of payload containers is in the range of 2 to 1000. Each payload container is in one embodiment displaced φ in the range of 0-180 degrees to the next payload container. 
     It is also desirable to provide a spin stabilized projectile for providing a horizontal dispersion pattern. The projectile according to an aspect of the invention comprises at least one payload container comprising at least two sub-projectiles arranged in at least one line as described above. The payload container may comprise a plurality of layers of sub-projectiles wherein the layers are arranged in substantially on plane. The payload containers are arranged and displaced in relation to each other as described above. 
     A suitable spin stabilized projectile comprises an elongated casing having a longitudinal axis extending from a nose portion of said elongated body to a rear portion of said elongated body, the nose part is arranged to a front portion and comprises a fuze for activating the primer device and a sensor. The sensor may in one embodiment be a gyro. A payload chamber is disposed in the front portion and comprises at least one payload container having at least two sub-projectiles arranged substantially in one plane as described above. 
     In one embodiment the payload chamber of the projectile comprises at least one payload container as described above. 
     In one embodiment the payload chamber comprises a plurality of sequentially arranged payload containers. The number of payload containers may be in the range of 2-1000. 
     The containers are displaced in relation to each other. The displacement angle, φ, may be in the range of 0-180 degrees. 
     It is also desirable to use the projectile described above, comprising at least one of the above described payload chambers for providing a horizontal dispersion pattern. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention is now described, by way of examples, with reference to the accompanying drawings, in which: 
         FIGS. 1 a   - c:  Show a cross section of a projectile comprising sub-projectiles of prior art (a), the velocity tangent of each sub-projectile upon separation from a projectile (b) and an illustration of a circular dispersion pattern (c). 
         FIGS. 2 a   - e:  Show cross sections of different embodiments of sub-projectiles arranged in a payload container (a, c); the velocity tangent of each sub-projectile upon separation from a projectile (b, d) of the embodiments shown in a) and c), and an illustration of the displacement angle φ is shown in e. 
         FIGS. 3 a - d    Show perspective views of three payload containers in a line (a, b), the embodiment of (b) arranged in a stack of six payload containers displaced in relation to each other (c), and a stack of payload containers (d) comprising sub-projectiles of different size. 
         FIGS. 4 a   - b:  Show illustrations of the dispersion pattern obtained by using a payload container comprising sub-projectiles of the same size (a), and by using sub-projectiles of different sizes (b). 
         FIGS. 5 a - b    Show a side view of a payload container (a) and a section along line A-B of a payload container as shown in (a) comprising a plurality of spherical sub-projectiles arranged in lines, and in two layers (b). 
         FIGS. 6 a - c    Show a cross-section of a payload container comprising small cuboid sub-projectiles arranged in two lines (a), a stack of payload containers comprising larger cuboid sub-projectiles (b), and an illustration of the obtained dispersion pattern (c). 
         FIGS. 7 a - c    Show a payload container comprising sub-projectiles with a hexagonal cross section, with small sub-projectiles in a first layer (a), and larger sub-projectiles in a second layer (b), and first and second layer with offset angle (c). 
         FIGS. 8 a - b    Illustrates a cross section of a payload container comprising sub-projectiles with a rectangular cross section (a), and an embodiment for providing a denser dispersion pattern. 
         FIG. 9  Shows an example of a projectile suitable for carrying the payload containers of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before the invention is disclosed and described in detail, it is to be understood that this invention is not limited to particular materials or configurations disclosed herein as such configurations and materials may vary. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims. 
     In the context of the present invention the term dispersion pattern means the distribution of rounds fired from a weapon. 
     In context of the present invention the term sub projectile means a small weapon or device that is part of a larger warhead and separates from it prior to impact, e.g., rods, flechettes, arrow-like darts, cylindrical, rectangular, hexagonal, cuboid, disc, spherical or ball-shaped i.e., not only munitions of various kinds, but all kinds of payloads, from which a specific continued flight on a determined flight path is expected after its release. 
     In context of the present invention the term payload container defines a device that encloses an assembly of sub-projectiles, at least two sub-projectiles. 
     In context of the present invention the term substantially one plane means that sub-projectiles arranged in at least two layers in the same payload container may be somewhat displaced in relation to each other see for example  FIG. 7 a - c    for illustration. 
     In context of the present invention the term stack defines a plurality of payload containers arranged after each other. 
     The term displaced means that the first line of sub-projectiles in the first payload container is rotated a certain angle, φ, in respect of the second line of sub-projectiles in the second payload container. 
     The term chord of a circle is a straight line segment whose endpoints both lie on the circle. Among properties of chords of a circle are the following: Chords are equidistant from the centre if and only if their lengths are equal; Equal chords are subtended by equal angles from the centre of the circle; A chord that passes through the centre of a circle is called a diameter, and is the longest chord. Every diameter is a chord, but not every chord is a diameter. In this application chords are used to illustrate that the projectiles are not radially disposed. 
     The present invention will now be described in detail with reference to the accompanying figures, in which embodiments of the invention are shown. 
     The present invention provides an arrangement of payload containers comprising sub-projectiles for providing an elongated dispersion pattern, i.e., a horizontal dispersion pattern. A horizontal dispersion pattern is suitable for combatting surface targets; targets having little vertical extent located on for example the water surface, Fast Inshore Attack Craft (water vehicle; various locations, FIAC), shore targets, ground targets, i.e., land or sea targets moving in two dimensions in general. 
       FIGS. 1 a  and  b    show cross-sections of a projectile  50  comprising sub-projectiles  1  of prior art. The sub-projectiles  1  are evenly distributed in a circular pattern in the projectile (a). When the projectile is fired it is travelling forward in the flight direction and rotates around its longitudinal axis. At a predetermined time the separation charge is initiated and the sub-projectiles are released from the shell. The sub-projectiles departs in the tangential direction from the carrier shell (b) resulting in a circular dispersion pattern (c). 
       FIG. 2 a    shows a two dimensional cross sections of a payload container  10  comprising two sub-projectiles  1  arranged substantially linear to each other in a payload container  10 . The sub-projectiles are arranged, embedded, enclosed or fixed at least partially by a core material  3 . The core  3  disposes the sub-projectiles  1  in position in the payload container, enclosed by the container wall  2 . The container wall may be a part of the core material  3 . The core  3  material may be one of those known by the art. The core  3  may also be designed as a holding device (not shown) enclosing each of the sub-projectiles  1  in a payload container. The holding device may function as a payload chamber. The design of a holding device may vary. In one embodiment the support device is designed as a core with at least two legs protruding from the core  3 . Each leg encloses at least partly one sub-projectile  1  each. The number of legs depends on the number and type of sub-projectiles, projectile, aim and target, etc. The supporting device may also have the effect of decreasing disturbances i.e., tumbling, when sub-projectiles separate from a projectile e.g., a cylinder or carrier shell. By decreasing the number of contact-impact events the effect and/or penetration of the sub-projectiles into a target is improved. A supporting device may also be used in combination with any core material  3 . The payload container may be dividable along line  4 . The invention is not limited to a two-part construction. The construction can be dividable in two or several parts or not dividable at all. 
     In one embodiment, the centre of the core  3  may comprise a bore for arrangement of a continuous detonator wire, for example a shock tube or an electric wire. 
       FIG. 2 b    illustrates on the left hand the velocity tangent (straight arrows) of the sub-projectiles in (a) during rotation (curved arrow) of the projectile, and on the right hand the sub-projectiles  1  in a first payload container in relation to the sub-projectiles  1  in a second payload container (dashed circle). 
       FIG. 2 c    shows a payload container  10  comprising four sub-projectiles  1  arranged in line, the payload container  10  comprises a container wall  2 , a core  3 , and a line  4 . Line  4  may be a dividing line. This embodiment of the payload container comprises two sub-projectiles  1  described above. 
     In another embodiment the centre of the core  3  may comprise a bore for arrangement of a continuous detonator wire, for example a shock tube or an electric wire. 
       FIG. 2 d    illustrates on the left hand the velocity tangent (straight arrows) of the sub-projectiles  1  during rotation (curved arrow) of the projectile, and on the right hand the sub-projectiles  1  in a first payload container in relation to the sub-projectiles  1  in a second payload container (dashed circle). 
     The number of sub-projectiles  1  is not limited to the examples shown here. The number of sub-projectiles  1  in one payload chamber  10  can be in the range of 2-1000 depending on the size of the sub-projectiles  1 , the aim, target and/or the payload container  10  and the projectile  50 . In other embodiments the number of sub-projectiles  1  may be in the range of 2-500, or 2-100, or  2 -75, or 2-50, and in other embodiments in the range of 2-25.  FIG. 2 e    shows the displacement angle φ between the first payload container A comprising sub-projectiles arranged in a line  1 A (solid line), in relation to the next payload container B comprising sub-projectiles arranged in line  1 B (dotted line). The angle of displacement φ of the payload containers  10  in relation to each other depends on the spin velocity and the longitudinal velocity relative to the carrier shell  50  from which the payload containers are ejected. A separation charge may give the payload containers  10  slightly different exit velocities, and therefore the displacement angle of each payload container may have to be different. 
     Generally, the displacement angle φ is the angle in degrees that the projectile rotates during the time t (s). φ (°) corresponds to the displacement angle that the payload container  10  is displaced for providing a horizontal dispersion patent. φ is calculated by the formula: 
     
       
         
           
             ϕ 
             = 
             
               
                 ω 
                 projectile 
               
               · 
               
                 
                   L 
                   
                     payload 
                      
                     
                         
                     
                      
                     container 
                   
                 
                 
                   v 
                   separation 
                 
               
               · 
               
                 
                   180 
                    
                   ° 
                 
                 π 
               
             
           
         
       
     
     wherein 
     ω is the angular velocity (rad/s) of the projectile  50 ; 
     v is the velocity (m/s) of the payload container  10  in relation to the projectile  50 ; 
     L is the length (m) of the payload chamber  80 ; 
     t is the time (s) it takes for the payload container  10  to leave the projectile  50 . 
     The displacement angle φ (°) can thus vary between the containers  10  in a stack  100 , the condition is that the line of sub-projectiles  1  are in a vertical position when leaving the projectile  50  and payload container  10  resulting in the horizontal dispersion pattern. 
       FIGS. 3 a  and  b    show perspective views of three (A, B, C) payload containers  10  arranged after each other in a line, wherein each payload container comprises two (a) or four (b) sub-projectiles  1 . The second payload container B is displaced with the angle φ in relation to the first payload container A, and the third payload container C is displaced in relation to the second payload container B and the first payload container A etc. 
       FIG. 3 c    shows a perspective view of six payload containers  10  comprising in this embodiment  4  sub-projectiles  1  each, arranged in a stack  100 . Each payload container  10  is angularly displaced in relation to the next container as shown in  FIGS. 3( a ) and ( b ) , respectively. The embodiment of the stack  100  shown in d) comprises payload containers  10  comprising four (A, C, E) or two (B, D, F) sub-projectiles  1 , respectively. The displacement angle φ of the payload containers  10  compensates for the rotation of the projectile resulting in a horizontal dispersion pattern of the sub-projectiles  1 . 
     The invention is not limited to a particular size or number of sub-projectiles. The sub-projectiles  1  do not need to be of the same size in the same payload container  10 . Payload containers  10 , arranged after each other i.e., first, second, and third payload container etc. can comprise different types of sub-projectiles  1 . A payload container  10  can also comprise more than one layer of sub-projectiles  1 ,  1 ′. 
       FIGS. 4 a  and  b    show illustrations of the obtained dispersion pattern by using sub-projectiles  1  having the same size (a), or sub-projectiles  1  of different size (b). Projectiles  50  of 57 mm were used and each payload container  10  was displaced in an angle φ of about 15 degrees to the next payload container  10 . 
     Suitable projectiles  50  for exercising the present invention are in the range of 30-155 mm. 
     The empty projectile  50  is shown in the middle of the illustration and parts of the container wall  2  are shown in the outermost. Released sub-projectiles  1  are lined up horizontally and continue their path to finally hit a predetermined target. The dispersion pattern is horizontal in both cases. The arrangement of the sub-projectiles  1  in the payload container  10  and the degree of displacement angle φ of the payload containers  10  to each other are used to influence the dispersion pattern. The displacement angle φ between the payload containers  10  is arranged in such way that the sub-projectiles  1  have the position as shown in  FIGS. 2 b  and 2 d    when the mechanical force from the projectile wall  2  disappears and the sub-projectiles  1  are released. The sub-projectiles  1 ,  1 ′are vertically lined at the time when the mechanical force from the carrier shell disappears. 
       FIG. 5 a    shows a side view of a payload container  10  (left side). The payload container is in the form of a cylinder. A section of the payload container  10  along line A-B is shown to the right. 
     The straight line segments (Ø, C 1 , C 2 ) inside the circle are chords, wherein the diameter Ø is the longest chord and C 1 , C 2  are shorter. The invention is not limited to 3 lines of sub-projectiles, this example is only for illustrating that the sub-projectiles  1  are disposed along chords in the payload container  10 . The sub-projectiles  1 , do not have to extent the whole way to the wall  2 . A cross section of a projectile  50  in the same direction as above a, left) is shown in  FIG. 5 b    (to the left). The projectile  50  comprises a payload container  10  and the sub-projectiles  1  are in this example spherical and arranged in a plurality of lines. The diameter Ø of the projectile  50  is in this case 155 mm. The section on the right shows that the payload container  10  comprises sub-projectiles arranged in two layers; sub-projectiles  1  correspond to a first layer and sub-projectiles  1 ′ correspond to a second layer. The layers are in one plane. In this example there are a total number of 246 sub-projectiles arranged in two layers. 123 spherical sub-projectiles  1  are arranged in the first layer and 123 spherical sub-projectiles are arranged in the second layer. The number of layers may be at least one. The upper limit of the numbers of layers in a payload container  10  is only limited by the aim, the projectile  50  and the payload  1 ,  1 ′. 
       FIG. 6 a - c    show examples of the use of cuboid sub-projectiles  1 . The first example shows the use of small cuboid sub-projectiles  1  arranged in two lines (a) in a payload container  10 . A stack  100  of six payload containers  10  comprising larger cuboid sub-projectiles  1  arranged in one line is shown in  FIG. 6   b.  The payload containers  10  are angularly displaced a predetermined angle φ in relation to each other as described above. The obtained horizontal dispersion pattern by the cuboid sub-projectiles  1  is illustrated in  FIG. 6 c   . 
     An example of using sub-projectiles  1  with hexagonal cross section is shown in  FIG. 7 . Small sub-projectiles  1  are arranged in a first layer (a), and large sub-projectiles  1 ′ are arranged in a second layer (b) of a payload container  10 . The layers are disposed in substantially one plane but with an offset angle between the first and second layer of sub-projectiles  1 ,  1 ′ ( FIG. 7 c   ). By small variations of the offset angle between the layers the sub-projectiles  1 , can be more spread vertically but still providing a horizontal dispersion pattern. 
       FIG. 8 a    illustrates a payload container  10  comprising sub-projectiles  1  with rectangular cross section arranged in a line, and disposed symmetric on each side of the dividing line  4 .  FIG. 8 b    shows an embodiment for providing a denser dispersion pattern. Two of the sub-projectiles in the payload container  10  are truncated resulting in sub-projectiles of a different size  1 . Each centre of gravity is moved a distance x from the dividing line  4 . By varying the distance x in each layer of sub-projectiles  1  a denser spread pattern is obtained. The dispersion velocity for each sub-projectile can be varied by changing the distance to the centre of the payload container ( 10 ) 
       FIG. 9  shows a spin stabilized projectile  50 , in the form of a carrier shell, suitable for comprising at least one payload container  10  of the present invention. The projectile  50  comprises a front projectile body  20  and a rear projectile body  30  and a rotating band  40 . The front and rear projectile body is joined by means of for example a threaded connection, or splines in combination with some form of axial locking. The rear projectile body  30  comprises a separation charge  130  and a pyrotechnic primer device  60  for initiating the separation charge  130 . The primer device  60  is arranged in front of the separation charge  130  behind a drive plate  70  adjacent to the rear end of a payload chamber  80  and the front projectile body  20 . The separation charge  130  may consist of or comprise a propellant charge of conventional type, for example a propellant charge comprising a smokeless nitrocellulose propellant, or in an alternative embodiment a composite propellant. 
     The payload chamber  80  arranged in the front projectile body  20  comprises at least one payload container  10  comprising sub-projectiles  1 . A time fuze  145 , comprising an activation unit for activating the primer device  60  is arranged in the nose part  140  of the front projectile body  20  in front of the payload chamber  80 . The nose part  140  is fitted to the front projectile body  20  by a second drive plate  110  and by for example shears pins  90 , which are designed to rupture under the effect of the pressure on the separation of the payload chamber  80  from the projectile  50 . In an alternative embodiment a continuous detonator wire  120 , for example a shock tube, is connected to the pyrotechnic primer device  60  for the propellant charge  130  in the rear part  30 , and a primer device in the nose part  140  for initiating the reaction in the shock tube  120  for separating the nose part  140  from the projectile  50 . 
     The separation from the projectile  50  is initiated by a signal from the time fuze  145 . 
     A sensor  150  (for example a gyro, lateral laser/radar) arranged in the nose part  140  keeps track of the rotational position of the projectile  50  relative to ground/water signals and initiates the separation charge  130  in the rear end  30  of the projectile  50 . A pressure is built up behind the payload chamber  80  and the payload containers  10  are pressed out from the rotating projectile  50  one by one. The displacement angle φ of each payload container  10  in relation to the next payload container  10  is arranged in such way that the sub-projectiles  1  in the payload container  10  are vertically lined (see  FIGS. 2 b, d   ) when the mechanical force from the carrier shell disappears and the sub-projectiles  1  are released. The sub-projectiles  1  are spread to the left and to the right, and the empty projectile  50  continues straight forward. Several projectiles  50  are preferably fired in succession. 
     Other embodiments may have a plurality of sensors for example to provide flight position data by detecting the relative orientation of the projectile body  50  during operation. The output of the sensors is fed into a guidance control system to enable flight corrections when necessary. The guidance control system may be any systems suitable for guiding spin stabilized projectiles during flight. 
     The payload container  10  is for example manufactured separately; suitable sub-projectiles  1  are arranged in substantially one plain in a payload container  10  in a core  3  material. The at least one payload container  10  comprising sub-projectiles  1  is thereafter arranged in a suitable projectile/carrier shell  50 . If a plurality of payload containers  10  (e.g., a stack  100 ) are arranged in the projectile  50 , they are angularly displaced in relation to each other in such way that a horizontal dispersion pattern is obtained when they are ejected against a target. 
     The sub-projectiles  1  may be made of hard- or heavy metal. 
     The payload container  10  of the present invention is intended to be used in direct fire, and in commercially available projectiles. Sub-projectiles suitable for the holding device  10  of the present invention are for example rods, flechettes, armor-piercing tungsten carbide projectiles, tungsten spheres, tungsten discs, tungsten cubes, tungsten hexagons etc. 
     Other features and uses of the invention and their associated advantages will be evident to a person skilled in the art upon reading the description and the examples. 
     In summary, the present invention provides an inventive device in the form of a payload container and a method for providing a horizontal dispersion pattern optimal for direct fire against surface targets. The invention increase both hit rate, effectiveness and decrease the risk of collateral damage, which are important factors contributing to the economic advantage of the present invention. The sub-projectiles can be made bigger and heavier without increasing the weight of the carrier shell itself, which increase the penetration capability of the sub-projectiles into the target. The present invention also provides a more “inert” carrier shell except the separation charge, which is yet an advantageous from IM point of view.