IL160500A

IL160500A - Method of retrofiting a munition for enhancing fragmentation effectiveness

Info

Publication number: IL160500A
Application number: IL16050004A
Authority: IL
Original assignee: Rafael Advanced Defense Sys
Priority date: 2004-02-20
Filing date: 2004-02-20
Publication date: 2009-02-11
Also published as: WO2005079163A2; WO2005079163A3

Description

160500/3 A METHOD OF RETROFITING A MUNITION FOR ENHANCING FRAGMENTATION EFFECTIVENESS A METHOD OF RETROFITTING A MUNITION FOR ENHANCING FRAGMENTATION EFFECTIVENESS FIELD AND BACKGROUND OF THE INVENTION The present invention relates to munition and, in particular, it concerns the retrofit of pre-existing legacy munition to improve the effectiveness of the legacy munition.

A large number of older type legacy munition which exist in the arsenal of various armed forces have the characteristic of being of a simple general purpose (GP) design. GP design legacy munition typically exhibits natural fragmentation, which has a limited effectiveness. Natural fragmentation produces a random number of fragments with a random variation in shape, size and mass. Additionally, GP design legacy munition typically exhibits unsatisfactory precision. Therefore, GP design legacy munition has a low kill probability rate per unit of munition in most combat situations. The relative ineffectiveness of the legacy munition makes them unattractive to be used in combat situations leading to the build-up of large inventories of munition, most of which are practically unusable.

The outcome of this stockpiling process has three major undesirable consequences. First, the accumulation of old munition poses a threat to the local population. Second, the accumulation of old munition poses a threat to the environment when the munition is ultimately disposed of. Third, expenditure of public funds on modernizing the arsenal by replacing old munition with new munition poses a financial drain on the economy.

By way of introduction, modern munition has become more effective than legacy GP design munition due to inclusion of one or more of the following improvements in modern designs. First, navigation, guidance, and homing modules are included in air bombs. Second, various aerodynamic surfaces are included in bombs and projectiles. Third, clusters of bomblets are included in a single munition. Fourth, warheads of munition are produced with controlled fragmentation means. Fifth, munition is fitted with proximity fuzes. Sixth, advanced explosives are used. Seventh, hardened bomb casings and shells as well as penetration means are incorporated into the munition design.

Upgrading of GP legacy weapons is known in the prior art. Upgrading of GP legacy weapons currently includes two main methods. First, fitting navigation, guidance, and homing modules as an add-on to air bombs. This is an expensive process. Second, fitting various aerodynamic surfaces, such as control or lifting surfaces, as an add-on, to bombs and projectiles. This process usually leads to only minor improvements in the kill rate per bomb or projectile.

Incorporating controlled fragmentation in the design of new munition has been widely described in prior art. Some leading examples of the prior art are as follows. U.K. patent No. 2,100,846 to Renson teaches the use of a helix wire of fragments wound around an explosive charge, and installed over a continuous wall. P.C.T. publication No. 01/90683 to Arnold teaches the positioning of fragments between the external shell and an internal shell of a fragmentation bomb. U.S. Patent No. 6,598,534 to Lloyd et al. teaches placement of projectiles in a hull formed around an explosive core. U.S. Patent No. 6,584,909 to Brede et al. teaches a manufacturing method of fragmentation by introducing a sealant in the gap between the projectile and the case parts of a cartridge. U.S. Patent No. 6,484,642 to Kuhns et al. teaches a fragmentation matrix created by a pre-formed fragmentation shell. U.S. Patent No. 6,374,744 to Schmacker et al. teaches a shrouded airborne bomb designed as an upgrade preserving legacy properties to eliminate the need to conduct re-qualification tests. U.S. Patent Nos. 5,41 9,024 and 5,337,673 to Koontz :e/ al. teach the use of an internal metal liner to produce controlled fragmentation of a casing. U.S. Patent No. 5,320,044 to Walters teaches forming a charge liner that produces two distinct fragmentation jets. U.S. Patent No. 5,313,890 to Cuadros teaches use of a fabric liner to extend the effect of the explosion gases. Finally, Russian Inventor Certificate 2, 1 79,297 to Kamchatnikov et al. teaches a fragmentation warhead with a controlled fragmentation subsystem that is located in an annular cavity in the body of the warhead. However, the systems and methods of the above prior art patents and publications cannot be used for cost effective and simple upgrading of existing GP design legacy munition from stockpiles.

Also of general interest is U.S. Statutory Invention Registration No. H1930 to Crabtree and U.K. Patent No. 2,384,291 to Gethings et al . Crabtree teaches fitting a precursor warhead to an existing rocket by a friction fit. Gethings et al. similarly requires a second warhead to be added in front of the legacy warhead. A shortcoming of the systems of Crabtree and Gethings et al. is that the legacy munition is used as a basic component of a new and essentially different system, thus the old type munition is essentially integrated into a new type of munition. Additionally, the new warhead is formed by adding an improved warhead to the legacy warhead thereby substantially changing the properties and form of the legacy weapon. An additional shortcoming of the system of Crabtree and Gethings et al. is that the upgrading of the legacy munition is very expensive and complex due to renewed qualification of the munition.

Also of interest is European Publication No. 0,409¾441 to Hughes which teaches replacing an existing probe module of a tube launched missile. A shortcoming of the system of Hughes is that the upgrading of the legacy munition is very expensive and complex due to renewed qualification of the munition.

There is therefore a need for a low cost method and system for improving the kill rate of GP legacy munition without changing the configuration and qualification of the munition.

SUMMARY OF THE INVENTION The present invention is a retrofit munition construction and method of production thereof.

According to the teachings of the present invention there is provided, a method for increasing the effectiveness of pre-existing munitions, comprising the steps of: (a) providing a munition having an explosive disposed therein; and (b) disposing at least part of a controlled fragmentation module on the munition, the controlled fragmentation module including at least one preformed fragment.

According to a further feature of the present invention, the controlled fragmentation module includes a plurality of preformed fragments.

According to a further feature of the present invention, there, is also provided the step of processing at least one element of the munition in order to remove a part of the at least one element thereby forming at least one cavity in the munition, wherein the step of disposing is perforfned'by disposing at least part of the controlled fragmentation module in the cavity.

According to a further feature of the present invention, there is also provided the step of mechanically interconnecting the preformed fragments.

According to a further feature of the present invention, there is also provided the steps of: (a) disposing the preformed fragments on a strand; and (b) winding the strand around the munition.

According to a further feature of the present invention, there is also provided the step of removing a majority of the explosive from the munition prior to performing the step of processing.

According to a further feature of the present invention, there is also provided the step of removing a fuze of the munition prior to performing the step of processing.

According to a further feature of the present invention, the step of processing is performed while a majority of the explosive remains disposed in the munition.

According to a further feature of the present invention, a mass reduction of the munition resulting from the step of processing is at least 50% of a mass increase of the munition resulting from the step of disposing.

According to a further feature of the present invention, the steps of i processing and disposing are performed, such that a mass distribution of the ' ,: -y munition is substantially unchanged by the steps of processing and disposing. According to a further feature of the present invention, the steps of processing and disposing are performed, such that aerodynamics of the munition are substantially unchanged by the steps of processing and disposing.

According to a further feature of the present invention, the step of processing includes forming the cavity in an outer shell of the munition.

According to a further feature of the present invention, the munition is a munition selected from the group consisting of an air to surface general-purpose bomb and a part of an artillery round.

According to a further feature of the present invention, the step of processing is performed such that, at least part of an existing fragmentation element of the munition is removed from the munition in order to form at least part of the cavity.

According to a further feature of the present invention, the step of processing includes a cutting process.

According to a further feature of the present invention, the step of processing includes an etching process.

According to a further feature of the present invention, at least part of the cavity is symmetrically disposed around an axis of the munition.

According to a further feature of the present invention, the cavity includes at least one of a bore, an annular hollow, a conical hollow, a hemispherical hollow, a hollow an ogive cross-section and a hollow having an elliptic cross-section.

According to a further feature of the present ' invention, the controlled fragmentation module includes a filler material which is disposed between the at least one fragment and the munition in order to reduce air gaps between the at least one fragment and the munition.

According to a further feature of the present invention, the filler material is a sheet liner.

According to a further feature of the present invention, there is also provided a step selected from the group consisting of: (i) casting the at least one fragment in the filler material; (ii) adhesively attaching the at least one fragment onto the filler material; and (iii) embossing the at least one fragment into the filler material.

According to a further feature of the present invention, there is also provided the steps of: (a) molding a mixture the at least one fragment and filler material into a mold; and (b) disposing the molded mixture into the at least one cavity.

According to a further feature of the present invention the step of molding the molded mixture is performed by disposing the molded mixture and the mold into the at least one cavity.

According to a further feature of the present invention, the step of disposing includes a step selected from the group consisting of: (i) injecting the filler material into the at least one cavity; (ii) casting the filler material in the at least one cavity; and (iii) adhesively attaching the filler material to the at least one cavity.

According to a further feature of the present invention, the fragment is selected from a fragment of the group consisting of a spherically shaped fragment, perforated ring, segmented strand, segmented ring, nail, dart and a precut sheet.

According to a further feature of the present invention, the fragment includes at least one of a metal, an incendiary material, a chemical and a biologically active material.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is axial sectional view of a munition having a cavity formed therein that is constructed and operable in accordance with a preferred embodiment of the present invention; Fig. 2 is an axial sectional view of the munition of Fig. 1 having a controlled fragmentation module disposed in the cavity; Fig. 3 is an isometric view of the munition of Fig. 2; Figs. 4a to 4c are schematic views of controlled fragmentation modules for disposing in the cavity of the munition of Fig. 1 ; Fig. 4d is a plan view of a segmented wire strand for disposing in the cavity of the munition of Fig. 1 ; i Fig. 4e is an isometric view of the segmented wire stand of Fig. 4d; •V Fig. 4f is a plan view of a segmented and perforated: ring for disposing in the cavity of the munition of Fig. 1 ; Fig. 4g is a side view of the segmented and perforated ring of Fig. 4f Fig. 4h is an isometric view of a cut sheet for disposing in the cavity of the munition of Fig. l ;and Fig. 5 is a schematic view of a retrofit munition that is constructed and operable in accordance with an alternate embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a retrofit munition construction and method of production thereof.

The principles and operation of a retrofit munition according to the present invention may be better understood with reference to the drawings and the accompanying description.

By way of introduction, the present invention teaches retrofitting older munition types having uncontrolled natural fragmentation by a'dding controlled fragmentation modules to the older munition. The retrofit process of the present invention leads to enhanced kill effectiveness per munition at relatively low costs as well as maintaining many of the original features of the munition, such as size class definition. The retrofit process of the present invention results in munition having a different structure from both older and newer munition. For ι example, a retrofit munition of the present invention has the shape of older ■i . munition but exhibits controlled fragmentation on explosion. However, the number and location of controlled fragmentation elements of the retrofit munition of the present invention differ from the typical number and typical location of controlled fragmentation elements of a modern munition initially produced with controlled fragmentation features.

Reference is now made to Fig. 1, which is axial sectional view of a munition 10 having a cavity 12 formed therein that is constructed and operable in accordance with a preferred embodiment of the present invention. The retrofit method of the present invention includes the following steps. First, munition 10 having an explosive 14 disposed therein is provided from an ordnance stockpile.

Munition 10 is generally an non-propelled type such as a bomb or a projectile, or a propelled type such as a missile or a rocket. Alternatively, munition 10 is a guided type such as a missile or a sophisticated bomb, or an unguided type such as a rocket or projectile or simple bomb, or an air-to- surface type, or a surface-to-surface type, or a surface-to-air type, or an air-to- air type. Munition 10 is typically, for example, but not limited to, an air to surface general purpose bomb, a part of an artillery round, an air to surface unguided rocket, an air to surface guided missile, an air to air guided missile, a surface to air missile, a surface to surface missile, a surface to surface unguided rocket, a mortar bomb, a bullet. It will be appreciated by those ordinarily skilled in the art that the retrofit method of the present invention can be applied to other munition types, for example, but not limited to maritime depth charges, maritime torpedoes, land mines, maritime buoy mines, hand grenades and rifle - or gun launched grenades.

Next, one or more elements, such as an outer shell 18 of munition 10, are processed in order to remove part of these elements, thereby forming cavity 12. Outer shell 18 typically includes the natural uncontrolled fragmentation element of munition 10. Therefore, part of the existing natural uncontrolled fragmentation element of munition 10 is removed from munition 10 in order to form cavity 12. The volume of cavity 12 is defined as the volume enclosed by a remaining portion of munition 10 and the original, now removed, surface 22 of munition 10. Cavity 12 is formed as an annular hollow which is symmetrically disposed around an axis 20 of munition 10. However, It will be appreciated by those ordinarily skilled in the art that cavity 12 may have a variety of shapes. Cavity 12 is typically performed by: a cutting process, for example, but not limited to lathing, milling or drilling; or an etching process, for example, but not limited to chemical etching, laser and electron beam etching. In accordance with a most preferred embodiment of the present invention, the step of forming cavity 12 is performed while explosive 14 and fuze 16 remain disposed in munition 10 thereby saving resources required to dissemble munition 10 as part of the retrofit process. It should be noted that in accordance with this most preferred embodiment of the present invention cavity 12 is formed, such that explosive 14 and fuze 16 are not disturbed by the process of forming cavity 12. i In accordance with an alternate embodiment of the present invention, fuze 16 is removed from munition 10 prior to forming1 cavity 12.

In accordance with another alternate embodiment of the present invention, fuze 16 and a majority of explosive 14 are removed from munition 10 prior to forming cavity 12.

Reference is now made to Fig. 2, which is an axial sectional view of munition 10 of Fig. 1 having a controlled fragmentation module 24 disposed in cavity 12. Reference is also made to Fig. 3, which is an isometric view of munition 10 of Fig. 2. Once cavity 12 has been formed, controlled fragmentation module 24 is disposed, at least partially, in cavity 12. Controlled fragmentation module 24 includes a plurality of metal spherically shaped preformed fragments 26. It will be appreciated by those ordinarily skilled in the art that preformed fragments 26 can be of varying size, number and shape.

Additionally, it will be appreciated by those ordinarily skilled in the art that preformed fragments 26 can be arranged in different formations in cavity 12.

Some preferred examples of controlled fragmentation modules are described with reference to Figs. 4a to 4c. Optionally, preformed fragments 26 are coated for example, but not limited to a coating of a heavy metal, an incendiary material, a corrosive and/or poisonous chemical, a biologically active material. The benefits of using controlled fragmentation instead of natural uncontrolled fragmentation are known to those skilled in the art. The term "controlled fragmentation module" is defined, herein, to include an arrangement of one or more preformed fragments, such that, on explosion of explosive 14, fragments of a predetermined size, mass, quantity and shape are propelled in generally predetermined directions. This is opposed to natural or uncontrolled fragmentation legacy elements, which have a predominantly random fragment distribution after their carrying munition has been exploded. Preformed fragments 26 are, optionally, either inter-connected or non-interconnected. Optionally, preformed fragments 26 are disposed in a dedicated sub-container (not shown) which is disposed in cavity 12. Controlled fragmentation module 24 also includes a filler material 28 which is disposed between preformed fragments 26 and outer shell 18 in order to reduce air gaps between preformed fragments 26 and outer shell 18. Materials suitable for filler material 28 are known to those skilled in the art of warhead liners. Filler material 28 helps prevent performance degradation of preformed fragments 26 on explosion of munition 10 due to pressure losses, reduction in the blast effect, or from inter-fragment collisions.

Preformed fragments 26 and filler material 28 are generally disposed in cavity 12 using one of the following four methods. The first method includes mechanically connecting preformed fragments 26 to filler material 28 to form controlled fragmentation module 24. for example, but not limited to: (i) casting preformed fragments 26 in filler material 28; (ii) adhesively attaching preformed fragments 26 onto filler material 28 (see Fig. 4c) and (iii) embossing preformed fragments 26 in filler material 28. Controlled fragmentation module 24 is then disposed in cavity 12. The second method includes disposing filler material 28 in cavity 12 by: (i) injecting or casting filler material 28 into ί cavity 12 using a mold (not shown) as necessary; or (ii) by adhesively attaching filler material 28 to outer shell 18. Preformed fragments 26 are then disposed on to filler material 28. The third method includes disposing a mixture of preformed fragments 26 and filler material 28 in cavity 12 typically by injecting or casting preformed fragments 26 and filler material 28 into cavity 12 using a mold as necessary. The fourth method includes molding a mixture of preformed fragments 26 and filler material 28 in a mold (not shown). The molded mixture is then disposed, with or without the mold, in to cavity 12. The molded mixture is typically adhesively connected to cavity 12.

It should be noted that the mass reduction of munition 10 resulting from forming cavity 12 is at least 50%, preferably 100%, of the mass increase of munition 10 resulting from disposing controlled fragmentation module 24 in cavity 12.

Preferably, the mass distribution and aerodynamics of munition 10 are substantially unchanged by the combined retrofit steps of forming cavity 12 and disposing controlled fragmentation module 24 in cavity 12. The term "substantially unchanged" is defined as, munition 10 after retrofit does not require extensive design modifications, re-verifications and re-qualifications. Aerodynamics of munition 10 is defined herein as the aerodynamic coefficients of lift, drag and moment. These aerodynamic coefficients are within the range of the aerodynamic coefficients of munition 10 prior to retrofit. Additionally, these aerodynamic coefficients do not significantly effect the margin of stability of the legacy aerodynamic configuration.

Reference is now made to Fig. 4a, which is a schematic view of a controlled fragmentation module 30 including nails or darts 32, for disposing in cavity 12 of munition 10 of Fig. 1. The preformed fragments of controlled fragmentation module 30 are implemented as darts 32 which are mechanically interconnected.

Reference is now made to Fig. 4b, which is a schematic view of a controlled fragmentation module 33, including a plurality of fragments 34 disposed on a strand 36, for disposing in cavity 12 of munition 10 of Fig. 1.

Fragments 34 are mechanically connected to strand 36. Strand 36 is then wound around munition 10 at cavity 12.

Reference is now made to Fig. 4c, which is a schematic view of a controlled fragmentation module 35 having a plurality of fragments 38 arranged in a matrix, for disposing in cavity 12 of munition 10 of Fig. 1.

Controlled fragmentation module 35 includes a sheet liner 40 which acts as a filler material. Fragments 38 are mechanically connected to sheet liner 40, typically using adhesive.

Reference is now made to Figs. 4d to 4h, which are various views of controlled fragmentation modules for use with munition 10. It will be appreciated by those ordinarily skilled in the art that controlled fragmentation module 35 can include other preformed fragments including preformed fragment modules known to those skilled in the art. For example, but not limited to a perforated ring, a segmented strand, a segmented ring, a precut sheet. US Patent No. 2,933,799 and UK Patent No. 2, 100,846, which are incorporated by reference for all purposes as if fully set forth herein, teach the use of segmented wire strands 52 (Figs. 4d to 4e) in i the design of new munition. UK patent No. 2,167,537, which is incorporated by reference for all purposes as if fully set forth herein, teaches the use of a segmented and perforated ring 54 (Fig. 4f and 4g) in the design of new munition. US Patent No. 3,878,704, which is incorporated by reference for all purposes as if fully set forth herein, teaches the use of a precut sheet 56 (Fig. 4h) in the design of new munition. Reference is now made to Fig. 5, which is a schematic view of a retrofit munition 42 that is constructed and operable in accordance with an alternate embodiment of the present invention. The method to produce retrofit munition 42 includes the following steps. First, a plurality of cavities 44 is formed in the outer shell 50 of munition 42, typically using a drill or milling machine. Second, one or more preformed fragments 46 along with a filler material 48 are disposed in each cavity 44. It will be appreciated by those ordinarily skilled in the art that cavity 44 can be formed to include many shapes, for example, but not limited to a bore, a conical hollow, a hemispherical hollow, a hollow having an ogive or elliptic cross-section. Additionally, it will be appreciated by those ordinarily skilled in the art that each cavity 44 can be orientated such that preformed fragments 46 are propelled in desired directions on explosion of explosive 14 (Fig. 1 ).

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior .art which would occur to persons skilled in the art upon reading the foregoing description.

Claims

1. ^r- -fflttfriod for increasing the effectiveness of pre-existing munitions, comprising the steps of: (a) providing a munition having an explosive disposed and having at least one element therein; (b) disposing at least part of a controlled fragmentation module on said munition, said controlled fragmentation module including at least one preformed fragment; and (c) processing the at least one element of said munition in order to remove a part of said at least one element thereby forming at least one cavity in said munition, wherein said step of disposing is performed by disposing at least part of said controlled fragmentation module in said cavity.

2. The method of claim 1 wherein said controlled fragmentation module includes a plurality of preformed fragments and said munition has a fuze and an outer shell.

3. The method of claim 2, further comprising the step of mechanically interconnecting said preformed fragments.

4. The method of claim 2, further comprising the steps of: (a) disposing said preformed fragments on a strand; and \- 160500/3 winding said strand around said munition.

5. The method of claim 2, further comprising the step of removing a majority of said explosive from said munition prior to performing said step of processing.

6. The method of claim 2, further comprising the step of removing said fuze of said munition prior to performing said step of processing.

7. The method of claim 2, wherein said step of processing is performed while a majority of said explosive remains disposed in said munition.

8. The method of claim 2, wherein a mass reduction of said munition resulting from said step of processing is at least 50% of a mass increase of said munition resulting from said step of disposing.

9. The method of claim 2, wherein said steps of processing and disposing are performed, such that a mass distribution of said munition is substantially unchanged by said steps of processing and disposing.

10. The method of claim 2, wherein said steps of processing and disposing are performed, such that aerodynamics of said munition are substantially unchanged by said steps of processing and disposing. 160500/3

11. The method of claim 2, wherein said step of processing includes forming said cavity in said outer shell of said munition.

12. The method of claim 11, wherein said munition is a munition selected from the group consisting of an air to surface general purpose bomb and a part of an artillery round.

13. The method of claim 2, wherein said step of processing is performed such that, at least part of an existing fragmentation element of said munition is removed from said munition in order to form at least part of said cavity.

14. The method of claim 2, wherein said step of processing includes a cutting process.

15. The method of claim 2, wherein said step of processing includes an etching process.

16. The method of claim 2, wherein at least part of said cavity is symmetrically disposed around an axis of said munition.

17. The method of claim 2, wherein said cavity includes at least one of a group including: a bore, an annular hollow, a conical hollow, a hemispherical hollow, a hollow having an ogive cross-section, and a hollow having an elliptic cross-section. OB- 160500/3

18. The method of claim 1, wherein said controlled fragmentation module includes a filler material which is disposed between said at least one fragment and said munition in order to reduce air gaps between said at least one fragment and said munition.

19. The method of claim 18, wherein said filler material is a sheet liner.

20. The method of claim 18, further comprising a step selected from the group consisting of: (i) casting said at least one fragment in said filler material; (ii) adhesively attaching said at least one fragment onto said filler material; and (iii) embossing said at least one fragment into said filler material.

21. The method of claim 18, further comprising the steps of: (a) molding a mixture said at least one fragment and filler material into a mold; and (b) disposing said molded mixture into said at least one cavity.

22. The method of claim 21, wherein said step of disposing said molded mixture is performed by disposing said molded mixture and said mold into said at least one cavity.

23. The method of claim 22, wherein said step of disposing includes a step selected from the group consisting of: (i) injecting said filler material into said at least one cavity; (ii) casting said filler material in said at least one 160500/3 cavity; and (iii) adhesively attaching said filler material to said at least one cavity.

24. The method of claim 1, wherein said fragment is selected from a fragment of the group consisting of a spherically shaped fragment, perforated ring, segmented strand, segmented ring, nail, dart and a precut sheet.

25. The method of claim 1, wherein said fragment includes at least one of a metal, an incendiary material, an active material. floor