Prefragmented warheads with enhanced performance

A deliverable weapon, such as a missile, an artillery round, an aerial bomb, or a mortar round, having an explosive warhead, utilizes concentric annular sleeves that upon detonation provide placement of smaller fragments of an inner annular sleeve interstitially with respect to larger fragments of an outer annular sleeve in an expanding fragmentation curtain that contains expanding gases to increase the pressure of the explosion and the kinetic energy transferred to the fragments. In embodiments, the sleeves are comprised of ordered layers of spherical metal fragments encased in binder material and an outer casing.

FIELD OF THE TECHNOLOGY

The present disclosure relates generally to weapons and, more particularly, to warheads including preformed fragments.

BACKGROUND

When U.S. military personnel go into battle, they rely on sophisticated and efficient weaponry to defeat enemy forces. In an effort to reduce the number of causalities suffered by U.S. forces, modern weapons are designed to deliver payloads from great distances with uncanny accuracy. Examples of these modern weapons include guided missiles, guided bombs dropped from aircraft including unmanned aerial vehicles (UAVs), and guided artillery shells. The primary destructive power of these weapons is provided by the warheads they carry.

Warheads are used in a variety of military applications to deliver a distribution of high-velocity fragments across a target area. The penetration effectiveness of a fragment when it strikes a target is directly proportional to the fragment's kinetic energy. The fragments kinetic energy is derived from an explosion. An explosion is a rapid increase in volume and release of energy accompanied by the generation of high temperatures and the release expanding gases. Supersonic explosions created by high explosives are known as detonations and travel via supersonic shock waves.

SUMMARY OF THE INVENTION

A deliverable weapon, such as a missile, an artillery round, an aerial bomb, a mortar round, or a grenade, having an explosive warhead, utilizes concentric annular sleeves that upon detonation provide placement of smaller fragments of an inner annular sleeve interstitially with respect to larger fragments of an outer annular sleeve in an expanding fragmentation curtain that contains expanding gases to increase the pressure of the explosion and the kinetic energy transferred to the fragments. In embodiments, the sleeves are comprised of ordered layers of spherical metal fragments encased in binder material and an outer casing.

According to an example embodiment, a warhead for a deliverable or non-deliverable weapon comprises an explosive charge and a first sleeve comprising a first set of uniform sized spherical fragments embedded in a binder disposed about the explosive charge. The warhead also includes a second sleeve comprising a second set of uniform sized spherical fragments embedded in a binder and disposed about the first sleeve. In this example embodiment, the first set of fragments comprise small fragments and the second set of fragments comprise large fragments. The warhead may also include a housing containing the first sleeve, the second sleeve, and the explosive charge.

In some example embodiment, the second sleeve has a single row of spherical fragments in an ordered arrangement. In some example embodiments, the arrangement of the spherical fragments may be somewhat chaotic generally due to the fragment sleeve thickness being greater than the fragment diameter. In some example embodiments, the large fragments in the second set of fragments are arranged in a plurality of axial columns and circumferential rows with adjacent circumferential rows being offset from one another in an axial direction and adjacent axial columns being offset from one another in a circumferential direction. It is contemplated that the fragments may have various non-spherical shapes in some embodiments.

In some cases, the large fragments are larger than the small fragments diametrically by at least 50%. In other embodiments, the large fragments are larger than the small fragments diametrically by at least 100%. In embodiments, volumetrically, the large fragments are at least 300% larger than the small fragments. In embodiments, volumetrically, the large fragments are at least 600% larger than the small fragments.

In some cases, the mean sizes of the large fragments are larger than the mean size of the small fragments diametrically by at least 50%. In other embodiments, the means size of the large fragments are larger than the mean size of the small fragments diametrically by at least 100%. In embodiments, volumetrically, the mean sizes of the large fragments are at least 300% larger than the mean size of the small fragments. In embodiments, volumetrically, the mean sizes of the large fragments are at least 600% larger than the mean size of the small fragments. In embodiments, substantially all of the large fragments are larger than substantially all of the small fragments. In some cases, the mean sizes of the greatest linear dimension of the large fragments are larger than the mean size of the greatest linear dimension of the small fragments by at least 50%. In other embodiments, the means size of the greatest linear dimension of the large fragments are larger than the greatest linear dimension of the mean size of the small fragments by at least 100%. In other embodiments, the means size of the greatest linear dimension of the large fragments are larger than the greatest linear dimension of the mean size of the small fragments by at least 300%.

In some example embodiments, the first sleeve is disposed between the explosive charge and the second sleeve so that expanding gases produced by the explosive charge upon detonation push the small fragments into contact with the large fragments. Also in some example embodiments, the small and large fragments have curved outer surfaces that facilitate migration of the small fragments into interstitial spaces between the large fragments when small fragments are forced into contact with large fragments upon detonation of the explosive charge so that the flow of the expanding gases through the interstitial spaces is restricted by the small fragments. The small fragments and the large fragments may form an expanding fragmentation curtain that provides improved containment of expanding gases compared to other fragmentation arrangements, and increases the total kinetic energy of the fragments.

The acceleration of the smaller fragments compared to the larger fragments, presuming common densities, varies with the inverse of the radii of the fragments. Thus, under the same explosive pressure, the larger fragments will not accelerate as fast as the smaller fragments, and immediately post detonation, will have less velocity and less kinetic energy. Placing small fragments interior to the large fragments such that the small fragments acceleration is impeded by larger fragments, the small and large fragments coalesce into a curtain immediately after the explosion providing an enhanced dynamic containment of the expanding gases increasing the pressure of the explosion and ultimately the kinetic energy of the fragments. Thus, a feature and advantage of embodiments of the invention is that with the bound uniform small fragments interior to the bound large fragments in an explosive condition, after the small and large fragments are unbound as the binder disintegrates, the small and large fragments provide an improved coalescence, that is, a generally greater density of fragments large and small, providing improved containment of the expanding explosive gases, increasing the explosive pressure providing enhanced acceleration and velocity to the fragments, large and small, and providing a net increase in kinetic energy of the totality of the fragments.

In some example embodiments, the first wall of the first sleeve comprises a first binding material, the second wall of the second sleeve comprises a second binding material, and the first binding material is substantially the same as the second binding material. In some example embodiments, the first binding material and/or the second binding material may comprise a thermoplastic resin. In some example embodiments, the first binding material and/or the second binding material may comprise a thermosetting polymer. In some example embodiments, the first binding material and/or the second binding material may comprise an epoxy.

In some example embodiments, the first binding material and the second binding material hold the small fragments separate from the large fragments prior to detonation of the explosive charge and the first binding material and the second binding material break into pieces and/or disintegrate upon detonation of the explosive charge so that the small fragments and the large fragments are free to contact each other.

In some example embodiments, the small fragments and the large fragments have a first infrangibility, the first binding material and the second binding material have a second infrangibility, and the first infrangibility is greater than the second infrangibility. It is contemplated that small fragments and/or large fragments may be deformed after detonation of explosive charge. Whether or not the fragments are deformed, the infrangibility of the fragments may be sufficient to prevent each fragment from breaking into a plurality of pieces.

In some example embodiments, the binding material is generally frangible and the fragments generally are not; stated differently, the first binding material is more frangible than the first fragments and the second binding material is more frangible than the second fragments. That is, for example, during the detonation of the explosive charge the first binding material disintegrates and the first fragments mostly remain intact; additionally the second binding material disintegrates and the second fragments mostly remain intact.

In embodiments, the binding material is generally frangible and the fragments are generally are not. The fragments are ductile and the binding material is not. In embodiments, upon detonation, the binding material is generally frangible and the fragments are generally are not, and the fragments are ductile and the binding material is not.

In some example embodiments, the small fragments and the large fragments comprise the same material. For example, the small fragments and the large fragments may both comprise a tungsten alloy or they may comprise steel.

In some example embodiments, the majority of the small fragments in the first set of fragments have a generally spherical outer surface. For example, substantially all of the small fragments in the first set of fragments have a generally spherical outer surface in some embodiments. In some example embodiments, the majority of the small fragments in the first set have substantially equal diameters. For example, substantially all of the small fragments in the first set of fragments may have substantially equal diameters in some embodiments.

In some example embodiments, the majority of the large fragments in the second set of fragments have a generally spherical outer surface. For example, substantially all of the large fragments in the second set of fragments have a generally spherical outer surface in some embodiments.

An illustrative method of manufacturing a warhead may include loading a first multiplicity of spherical fragments of a uniform first size within a first annular containment in an ordered arrangement and filling the first annular containment with a first annular containment binder for at least substantially covering the first multiplicity of spherical fragments. The first annular containment binder may have a flowable condition to facilitate filling of the first annular containment. The illustrative method may include allowing the binder to harden wherein the spherical fragments are embedded within the first annular containment binder in a first annular form having the shape of the first annular containment. This illustrative method may also include loading a second multiplicity of spherical fragments of a uniform second size within a second annular containment having a wall surface that corresponds to a wall surface of the first annular containment. This method may additionally include filling the second annular containment with a second annular containment binder for at least substantially covering the multiplicity of spherical fragments. The second annular containment binder may have a flowable condition to facilitate filling of the second annular containment. The method may include allowing the second annular containment binder to harden wherein the spherical fragments are embedded within the second annular containment binder in a second annular form with the shape of the second annular containment. An explosive material may be positioned within a cavity defined by the annular forms. The first annular form, the second annular form and the explosive material may be positioned within a housing with one annular form interior to the other annular form.

In embodiments, a method of manufacturing a warhead comprises, loading a first multiplicity of spherical fragments of a uniform first size within a first annular containment in an ordered arrangement; filling the first annular containment with a first annular containment binder for at least substantially covering the first multiplicity of spherical fragments, the first annular containment binder having a flowable condition; allowing the binder to harden wherein the spherical fragments are embedded within the first annular containment binder in a first annular form having the shape of the first annular containment; loading a second multiplicity of spherical fragments of a uniform second size within a second annular containment having an inner wall surface that dimensionally corresponds to an outer wall of the first annular containment, the uniform second size diametrically at least 50 percent larger than the uniform size of the first multiplicity of spherical fragments; filling second annular containment with a second annular containment binder for at least substantially covering the multiplicity of spherical fragments, the first annular containment binder having a flowable condition; allowing the second annular containment binder to harden wherein the spherical fragments are embedded within the second annular containment binder in a second annular form with the shape of the second annular containment; positioning explosive material within a cavity defined by the first annular form; and affixing the first annular form and the second annular form within a housing with the first annular form interior to the second annular form; whereby upon detonation, an enhanced coalescence of small and large fragments post detonation increases the post explosion pressurization providing a net increase in kinetic energy.

Some example methods may include utilizing the first annular form to define part of the second annular containment and/or utilizing the second annular form to define part of the first annular containment.

Some example methods may include loading the second multiplicity of fragments such that each fragment that is not at a periphery of the ordered arrangement is in contact with at least four other adjacent fragments of the same size.

In embodiments of the invention, a method of increasing the kinetic energy of a multiple layered fragmentation device includes providing a layer of smaller fragments each with a mass inside of a layer of larger fragments, the larger fragments having a greater mass than the smaller fragments, and placing explosive material inside the layer inside the layer of smaller fragments.

In embodiments of the invention, a method of increasing the kinetic energy of a multiple layered fragmentation device includes providing a layer of fragments, the fragments in the layer all having substantially the same size, providing fragments with substantially the same mass, the layer of fragments each with a mass inside of a layer of larger fragments, the larger fragments having a greater mass than the smaller fragments.

Some example methods may include overmolding one of the first annular form and the second annular form over the other of the first annular form and the second annular form.

Some example methods may include utilizing a thermoplastic resin as the first annular containment binder. A thermoplastic resin may also be utilized for the second annular containment binder in some example methods.

Some example methods may include installing the warhead in a deliverable weapon such as a missile, an artillery round, an aerial bomb, a mortar round, or other fired projectiles, or a grenade. The methods and apparatus herein may also be utilized in a fixed application, such as a land mine or other non-delivered applications.

Some example methods may include selecting a uniform size for the large fragments that is diametrically at least 100 percent larger than the uniform size of the small fragments.

Some example methods, may include selecting a uniform size for the greatest linear dimension of the large fragments that is at least 100 percent larger than the greatest linear dimension of the small fragments. Where there is some variability in the size of the large fragments and/or the small fragments, the greatest linear dimension is the mean greatest linear dimension of the large and/or small fragments.

Some example methods may include utilizing steel for the spherical fragments of the first multiplicity of spherical fragments and for the second multiplicity of spherical fragments.

Some example methods may include utilizing a tungsten alloy for the spherical fragments of the first multiplicity of spherical fragments and for the second multiplicity of spherical fragments.

In some example embodiments, the maximum diameter of the spherical fragments of the second multiplicity of spherical fragments is 0.300 inches or less.

In some example embodiments, the majority of the large fragments in the second set have substantially equal diameters. For example, substantially all of the large fragments in the second set of fragments may have substantially the equal diameters in some embodiments.

In some embodiments an inner layer is sandwiched between an explosive portion and an outer layer, with portions of the inner layer having smaller fragments than a coinciding portion of the outer layer. Other portions of the inner layer may not have smaller fragments than a respective coinciding portion of the outer layer, for example at corners or end portions of the inner layer. Thus, in embodiments, a particular pair of layers of fragments need not have uniformity of fragmentation sizes or uniformity of the differentiation between the sizes of the inner and outer layer throughout the respective layers. In embodiments, the inner layer may be comprised of spherical fragments and the outer layer non-spherical fragments.

DETAILED DESCRIPTION

FIG. 1is a perspective view showing a partially cross-sectioned warhead100in accordance with the present detailed description. Warhead100ofFIG. 1comprises an explosive charge108. Explosive charge108may comprise a cylindrical container filled with high explosives. A first sleeve102comprising a first set122of preformed fragments is disposed about explosive charge108. A second sleeve104comprising a second set124of preformed fragments is disposed about both first sleeve102and explosive charge108. With reference toFIG. 1, it will be appreciated that first sleeve102is sandwiched between explosive charge108and second sleeve104in the embodiment ofFIG. 1. In embodiments, the fragments may be spherical as illustrated and are formed of metal, such as steel or tungsten.

In the embodiment ofFIG. 1, the fragments of first sleeve102comprise relatively small fragments120and the fragments of second sleeve104comprise relatively large fragments130that are larger than small fragments120. In the embodiment ofFIG. 1, small fragments120are held in place by a first binding material132of first sleeve102. Large fragments130are held in place by a second binding material134of second sleeve104in the embodiment ofFIG. 1. In some embodiments, first binding material132and second binding material134may comprise the same material. Upon detonation of explosive charge108, first binding material132and second binding material134may disintegrate so that small fragments120and large fragments130become unbound. When this is the case, small fragments120and large fragments130are free from the binding effect of first binding material132and second binding material134after detonation of explosive charge108. In some example embodiments, the first binding material and/or the second binding material may comprise a thermoplastic resin. In some example embodiments, the first binding material and/or the second binding material may comprise a thermosetting polymer. In some example embodiments, the first binding material and/or the second binding material may comprise an epoxy.

It is contemplated that small fragments120and/or large fragments130may be deformed after detonation of explosive charge108. In some useful embodiments, small fragments120and large fragments130are both preformed fragments having sufficient infrangibility and sufficient ductility to remain intact after detonation of explosive charge108. First binding material132and second binding material134hold the fragments in place until detonation of explosive charge108. However, first binding material132and second binding material134lack sufficient strength to remain intact after detonation of explosive charge108. Said another way, the binding materials are more frangible and more brittle than the fragments. In particular, first binding material132is more frangible than small fragments120and second binding material134is more frangible than large fragments130. In some embodiments, first binding material132and second binding material134obliterate upon detonation of explosive charge108. Small fragments120and large fragments130are free to move relative to each other after first binding material132and second binding material134have broken into small pieces.

In the embodiment ofFIG. 1, each small fragment120and each large fragment130has a generally spherical outer surface. With reference toFIG. 1, it will be appreciated that small fragments120of first sleeve102are sandwiched between explosive charge108and the large fragments130of second sleeve104. With first sleeve102disposed between explosive charge108and second sleeve104, expanding gases produced by explosive charge108upon detonation will push small fragments120into contact with large fragments130. In some useful embodiments, small fragments120and large fragments130have curved outer surfaces that facilitate migration of small fragments120into interstitial spaces between large fragments130when small fragments120are forced into contact with large fragments130upon detonation of explosive charge108. The presence of small fragments120in the interstitial spaces between large fragments130may restrict the flow of the expanding gases between large fragments130. In this way, small fragments120and large fragments130may cooperate to contain the expanding gases for a longer time before venting of expanding gases has occurred. Increased containment of the expanding gases over a longer period of time may increase the kinetic energy transferred to the large fragments130, while only minimally reducing the kinetic energy of the small fragments upon detonation of the explosive charge, thus increasing the total fragmentation kinetic energy significantly.

Warhead100ofFIG. 1includes a sheath126that is disposed about second sleeve104, first sleeve102and explosive charge108. A first cap136is fixed to a first end of sheath126and a second cap138is fixed to a second end of sheath126. InFIG. 1, a detonator128of warhead100can be seen contacting explosive charge108.

FIG. 2is a perspective view showing a set of preformed fragments240arranged to form a sleeve250. In the embodiment ofFIG. 2, sleeve250includes a generally tubular wall252comprising a single layer of fragments240and each fragment240has a generally spherical outer surface. The fragments240are stacked so that adjacent pairs of fragments240are in tangential contact with one another in the embodiment ofFIG. 2. The single layer of stacked spheres illustrated inFIG. 2has a high compressive strength yet almost no shear strength. When sleeve250is incorporated into a warhead, a binding material may be used to hold fragments240in place prior to detonation of the warhead's explosive charge.

In the embodiment ofFIG. 2, the fragments240of sleeve250are arranged in a plurality of axial columns244and circumferential rows246. A first circumferential row246A of sleeve250includes plurality of fragments240positioned along a first curved line256A. Sleeve250also includes a second circumferential row246B, a third circumferential row246C, and a fourth circumferential row246D. Second circumferential row246B comprises a plurality of fragments240that are positioned along a second curved line256B. Third circumferential row246C comprises a plurality of fragments240that are positioned along a third curved line256C. In the embodiment ofFIG. 2, adjacent circumferential rows, such as second circumferential row246B and third circumferential row246C are offset from one another in an axial direction. Fourth circumferential row246D comprises a plurality of fragments240that are positioned along a fourth curved line256D.

In the embodiment ofFIG. 2, sleeve250includes a plurality of fragments240positioned along a first line254A to form a first axial column244A. First line254A is generally parallel to a central longitudinal axis242of sleeve250in the embodiment ofFIG. 2. A plurality of fragments240are positioned along a second line254B to form a second axial column244B. In the embodiment ofFIG. 2, adjacent axial columns, such as first axial column244A and second axial column244B, are offset from one another in a circumferential direction. A plurality of fragments240are positioned along a third line254B to form a third axial column244B. A plurality of fragments240are positioned along a fourth line254B to form a fourth axial column244B.

FIG. 3Ais a stylized cross-sectional view illustrating a warhead300including an explosive charge308.FIG. 3Bis a stylized axial view illustrating the operating of the warhead shown inFIG. 3A. More particularly,FIG. 3Bprovides a stylized illustration showing elements of warhead300after detonation of the explosive charge using solid lines. Dashed lines are used to illustrate the elements of warhead300prior to detonation of the explosive charge.

With reference toFIG. 3A, it will be appreciated that warhead300comprises an explosive charge308. A first sleeve302comprising a first set322of preformed fragments is disposed about explosive charge308. A second sleeve304comprising a second set324of preformed fragments is disposed about both first sleeve302and explosive charge308. With reference toFIG. 3A, it will be appreciated that first sleeve302is sandwiched between explosive charge308and second sleeve304in the embodiment ofFIGS. 3A and 3B.

In the embodiment ofFIGS. 3A and 3B, the fragments of first sleeve302comprise relatively small fragments320and the fragments of second sleeve304comprise relatively large fragments330that are larger than small fragments320. In the embodiment ofFIGS. 3A and 3B, small fragments320are held in place by a first binding material332of first sleeve302. Large fragments330are held in place by a second binding material334of second sleeve304in the embodiment ofFIGS. 3A and 3B. In some embodiments, first binding material332and second binding material334may comprise the same material.

In the embodiment ofFIGS. 3A and 3B, small fragments320and large fragments330are both preformed fragments having sufficient strength to remain intact after detonation of explosive charge308. For example, small fragments320and large fragments330may both comprise a tungsten alloy. First binding material332and second binding material334hold the fragments in place until detonation of explosive charge308. However, first binding material332and second binding material334lack sufficient strength to remain intact after detonation of explosive charge308. Said another way, the binding materials are sufficiently frangible to disintegrate upon detonation of explosive charge308.

FIG. 3Bis a stylized axial view showing elements of warhead300after detonation of the explosive charge using solid lines. Dashed lines are used to illustrate the elements of warhead300prior to detonation of the explosive charge.

With reference toFIG. 3B, it will be appreciated that expanding gases348produced by the explosive charge upon detonation have pushed small fragments320into contact with large fragments330. The presence of small fragments320are disposed in interstitial spaces358between large fragments330. The presence of small fragments320in interstitial spaces358between large fragments330may restrict the flow of the expanding gases348between large fragments330. In this way, small fragments320and large fragments330may cooperate to contain expanding gases348for a longer time before venting of expanding gases348has occurred. Increased containment of expanding gases348over a longer period of time may increase the kinetic energy transferred to large fragments330, while only reducing the energy of the small fragments slightly, upon detonation of explosive charge308thus significantly increasing the total kinetic energy of the fragmentation.

In some useful embodiments, small fragments320and large fragments330have curved outer surfaces that facilitate migration of small fragments320into interstitial spaces358between large fragments330when small fragments320are forced into contact with large fragments330upon detonation of explosive charge308. In the embodiment ofFIGS. 3A and 3B, each small fragment320and each large fragment330comprise a generally spherical outer surface. In the embodiment ofFIGS. 3A and 3B, each small fragment320comprises a preformed sphere having a first diameter DA. Each large fragment330comprises a preformed sphere having a second diameter that is larger than the first diameter DB in the embodiment ofFIGS. 3A and 3B.

FIG. 4Ais a stylized cross-sectional view illustrating a first warhead configuration460A.FIG. 4Bis a stylized cross-sectional view illustrating a second warhead configuration460B. Hydrocode analysis was performed on both first warhead configuration460A and second warhead configuration460B. The results of the hydrocode analysis are plotted inFIG. 5AandFIG. 5B.

The first warhead configuration460A shown inFIG. 4Acomprises a first sleeve402comprising a first set422of preformed fragments disposed about an explosive charge408. A second sleeve404comprising a second set424of preformed fragments is disposed about both first sleeve402and explosive charge408. In the embodiment ofFIG. 4, the fragments of first sleeve402comprise relatively large fragments and the fragments of second sleeve404comprise relatively small fragments that are smaller than the fragments of first sleeve402. First warhead configuration460A includes a first cap436that is located at first end of the sleeves and a second cap438that is located at a second end of the sleeves. InFIG. 4A, a detonator428can be seen contacting explosive charge408.

The second warhead configuration460B shown inFIG. 4Bcomprises a first sleeve502comprising a first set522of preformed fragments disposed about an explosive charge508. A second sleeve504comprising a second set524of preformed fragments is disposed about both first sleeve502and explosive charge508. In the embodiment ofFIG. 4B, the fragments of first sleeve502comprise relatively small fragments and the fragments of second sleeve504comprise relatively large fragments that are larger than the fragments of first sleeve502. Second warhead configuration460B includes a first cap536that is located at first end of the sleeves and a second cap538that is located at a second end of the sleeves. InFIG. 4B, a detonator528can be seen contacting explosive charge508.

With reference toFIG. 4AandFIG. 4B, it will be appreciated that warhead configuration460A and warhead configuration460B both include an explosive charge. For purposes of the hydrocode analysis, warhead configuration460A and warhead configuration460B had identical explosive charges including the same mass of high explosives. Warhead configuration460A and warhead configuration460B both include a set of relatively small fragments and a set of relatively large fragments. For purposes of the hydrocode analysis, warhead configuration460A and warhead configuration460B had identical sets of small and large fragments having identical masses. The primary difference between the two configurations was the arrangement of the two sets of fragments. With reference toFIG. 4AandFIG. 4B, it will be appreciated that, in the first warhead configuration460A shown inFIG. 4Athe large fragments are located between the explosive charge and the small fragments. It will also be appreciated that, in the second warhead configuration460B shown inFIG. 4Bthe small fragments are located between the explosive charge and of the large fragments.

FIG. 5AandFIG. 5Bare graphs illustrating the results of the hydrocode analysis performed on the two warhead configurations illustrated inFIG. 4AandFIG. 4B.

The graph shown inFIG. 5Aillustrates the energy profile of the first warhead configuration460A. Fragment kinetic energy vs. polar location is plotted on this graph. The data points representing the kinetic energy of the large fragments are shown as open triangles and the data points representing the kinetic energy of the small fragments are shown as closed triangles.

The graph shown inFIG. 5Billustrates the energy profile of a warhead with the second warhead configuration460B. Fragment kinetic energy vs. polar location is plotted in this graph. The data points representing the kinetic energy of the large fragments are shown as open circles and the data points representing the kinetic energy of the small fragments are shown as closed circles.

The results of the hydrocode analysis showed a substantial increase in fragment kinetic energy of the second warhead configuration460B as compared to the first warhead configuration460A.

FIG. 5Dis a theorized pressure curve chart illustrating gains associated with embodiments of the invention.FIG. 5Dincludes a first curve546and a second curve548, with the second curve representing the theorized pressure gains associated with embodiments of the invention.

FIG. 6AthroughFIG. 6Dare a series of stylized perspective views illustrating example methods in accordance with this detailed description and apparatus associated with those methods.

AtFIG. 6A, a first sleeve602is assembled over an explosive fill container662. High explosives may be placed in explosive fill container662at various times without deviating from the spirit and scope of this detailed description. In the embodiment ofFIG. 6A, first sleeve602has a generally annular shape including an inner surface that defines a first cavity668A. Although one half of an annular shape is shown, embodiments will include assembly of complete annular sleeves and partial annular sleeves. With reference toFIG. 6A, it will be appreciated that first cavity668A is dimensioned to receive explosive fill container662. First sleeve602comprises a first set622of preformed fragments. In the embodiment ofFIG. 6A, first set622comprise small fragments620.

AtFIG. 6B, a second sleeve604is assembled over first sleeve602and explosive fill container662. Second sleeve604has a generally annular shape including an inner surface664that defines a second cavity668B. It will be appreciated that second cavity668B is dimensioned to receive first sleeve602and explosive fill container662. With reference toFIG. 6C, it will be appreciated that first sleeve602will be sandwiched between explosive charge608and second sleeve604after second sleeve604is assembled over first sleeve602.

In the embodiment ofFIG. 6B, the fragments of first sleeve602comprise relatively small fragments620and the fragments of second sleeve604comprise relatively large fragments630that are larger than small fragments620. In the embodiment ofFIG. 6B, small fragments620are held in place by a first binding material632of first sleeve602. Large fragments630are held in place by a second binding material634of second sleeve604in the embodiment ofFIG. 6B. In some embodiments, first binding material632and second binding material634may comprise the same material.

AtFIG. 6C, a sheath626is installed over second sleeve604, first sleeve602and explosive fill container662. In the embodiment ofFIG. 6C, sheath626has a generally annular or tube-like shape.

AtFIG. 6D, a first cap636is fixed to a first end of sheath626and a second cap638is fixed to a second end of sheath626. First cap636, second cap638and sheath626may cooperate to contain, secure and protect all components located therein.

FIGS. 7A through 7Gare a series of cross sectional views of a mold and steps of manufacturing in accord with embodiments of the invention.

AtFIG. 7A, a mold770is provided. With reference toFIG. 7A, it will be appreciated that mold770defines a first annular containment782. In the embodiment ofFIG. 7A, mold770comprises a first core772, a mold body780, and a first plug776. First core772, mold body780, and first plug776cooperate to define the first annular containment782in the embodiment ofFIG. 7A. With reference toFIG. 7A, it will be appreciated that the first plug776defines passageways that fluidly communicate with the first annular containment782.

AtFIG. 7B, a first multiplicity of spherical fragments of a uniform first size are loaded within the first annular containment782. In the exemplary embodiment ofFIG. 7B, the first multiplicity of spherical fragments are arranged to form a wall comprising a single layer of fragments. The fragments are arranged so outer spherical surfaces of adjacent pairs of fragments are in tangential contact with one another in the embodiment ofFIG. 7B.

AtFIG. 7C, the first annular containment782is filled with a first annular containment binder786. In the illustrative embodiment ofFIG. 7C, the first annular containment binder786has a flowable condition so that the first annular containment binder flows into space between fragments. In this way, the first annular containment binder786fills the volume of the first annular containment that is not occupied by fragments so that the first annular containment binder786may hold the fragments in place after the first annular containment binder786has been allowed to harden. The hardened first annular containment binder786and spherical fragments embedded within the first annular containment binder786form a first sleeve702. With reference toFIG. 7C, it will be appreciated that first sleeve702generally has the shape of the first annular containment782.

AtFIG. 7D, the first mold insert776and the first core772are removed from the mold770. A second core774is placed in the position formerly occupied by the first core772. With reference toFIG. 7D, it will be appreciated that the second core774and first sleeve702defined a second annular containment784. AtFIG. 7D, a second multiplicity of spherical fragments of a uniform second size are loaded within the second annular containment784.

AtFIG. 7E, a second mold insert778has been placed in the position formerly occupied by first mold insert776. Second plug778defines passageways that fluidly communicate with the second annular containment784.

AtFIG. 7F, the second annular containment784is filled with a second annular containment binder788. In the illustrative embodiment ofFIG. 7F, the second annular containment binder788has a flowable condition so that the second annular containment binder788flows into space between fragments. In this way, the second annular containment binder788fills the volume of the second annular containment that is not occupied by fragments so that the second annular containment binder788will hold the fragments in place after the second annular containment binder788has been allowed to harden. The hardened second annular containment binder788and spherical fragments embedded within the second annular containment binder788form a second sleeve704. With reference toFIG. 7F, it will be appreciated that second sleeve704generally has the shape of the second annular containment784.

AtFIG. 7G, the first sleeve702and the second sleeve704have been removed from the mold770. With reference toFIG. 7G, it will be appreciated that second sleeve704defines a cavity790. A warhead in accordance with this detailed description may include first sleeve702, second sleeve704and an explosive charge disposed in cavity790. The explosive charge may comprise, for example, a container filled with high explosives.

With continuing reference toFIGS. 7A through 7G, it will be appreciated that a method of manufacturing a warhead in accordance with this detailed description may include loading a first multiplicity of spherical fragments of a uniform first size within a first annular containment in an ordered arrangement and filling the first annular containment with a first annular containment binder for at least substantially covering the first multiplicity of spherical fragments. The first annular containment binder may have a flowable condition to facilitate filling of the first annular containment. The method may include allowing the binder to harden wherein the spherical fragments are embedded within the first annular containment binder in a first annular form having the shape of the first annular containment. This example method may also include loading a second multiplicity of spherical fragments of a uniform second size within a second annular containment having a wall surface that corresponds to a wall surface of the first annular containment. This method may additionally include filling the second annular containment with a second annular containment binder for at least substantially covering the multiplicity of spherical fragments. The second annular containment binder may have a flowable condition to facilitate filling of the second annular containment. The method may include allowing the second annular containment binder to harden wherein the spherical fragments are embedded within the second annular containment binder in a second annular form with the shape of the second annular containment. An explosive material may be positioned within a cavity defined by the annular forms. The first annular form, the second annular form and the explosive material may be positioned within a housing with one annular form interior to the other annular form.

Some example methods may include utilizing the second annular containment to define part of the first annular form and/or utilizing the first annular containment to define part of the second annular form.

Some example methods may include loading the second multiplicity of fragments such that each fragment that is not at a periphery of the ordered arrangement is in contact with a plurality of other adjacent fragments of the same size.

Some example methods may include overmolding one of the first annular form and the second annular form over the other of the first annular form and the second annular form.

Some example methods may include utilizing a thermoplastic resin as the first annular containment binder. A thermoplastic resin may also be utilized for the second annular containment binder in some example methods.

Some example methods may include installing the warhead in a deliverable weapon such as a missile, an artillery round, an aerial bomb, a mortar round, or a grenade.

FIG. 8is a side view showing an assembly fabricated using the manufacturing steps illustrated inFIGS. 7A through 7G. An outer surface of first sleeve702is visible inFIG. 8

FIGS. 9-11are perspective views of illustrative warheads according to embodiments of the invention. With reference toFIGS. 9-11, it will be appreciated that warheads may have various three dimensional shapes without deviating from the spirit and scope of this detailed description.

FIG. 12Ais a perspective of a missile according to embodiments of the invention. The missile ofFIG. 12Amay include a warhead such as the illustrative warheads discussed in this detailed description. The missile may deliver the warhead to a precise location near a target. Once the warhead is near the target, the explosive charge may be detonated. The warhead may include concentric annular sleeves that upon detonation provide placement of smaller fragments of an inner annular sleeve interstitially with respect to larger fragments of an outer annular sleeve in an expanding fragmentation curtain that contains expanding gases to increase the pressure of the explosion and the kinetic energy transferred to the fragments. The fragments may neutralize the target.

FIG. 12Bis a perspective view of an artillery projectile according to embodiments of the invention. The artillery projectile ofFIG. 12Bmay include a warhead such as the illustrative warheads discussed in this detailed description. Warheads in accordance with this detailed description may be carried by various deliverable weapons. Examples of deliverable weapons include missiles, artillery rounds, aerial bombs, mortar rounds, and grenades. Warheads in accordance with this detailed description may also be incorporated into non-deliverable weapons. It is contemplated that warheads in accordance with this detailed description may be incorporated into landmines. In some applications, a warhead in accordance with this detailed description may a generally planar shape rather than an annular shape.