Explosive devices, and in particular cluster explosively-formed penetrator warhead devices, are described herein. In accordance with an exemplary embodiment, a spherically-shaped explosive device comprises an initiator, a fuze component system configured to ignite the initiator, and a substantially spherical explosive charge surrounding the initiator. The substantially spherical explosive charge has a substantially spherical surface. A plurality of liners are on the substantially spherical surface of the substantially spherical explosive charge.

FIELD OF THE INVENTION

The present invention generally relates to explosive devices, and more particularly relates to cluster explosively-formed penetrator warheads.

BACKGROUND OF THE INVENTION

Explosively-formed penetrator (EFP) warheads have proven useful against steel and other re-enforced armors. In a conventional single EFP, illustrated inFIG. 1, a main explosive charge12proximate to a detonator ignition train18is pressed or cast and machined in a steel casing or shell14that accommodates a liner16having a hemispherical, trumpet, conical or other similar shape. The liner is pressed into a machined cavity of the explosive charge. The liner is made of a highly ductile metal having a high density, such as copper, molybdenum, tungsten, aluminum, or the like. As illustrated inFIG. 2, when the explosive charge12is detonated by the detonator ignition train18, the liner16is projected forward as a molten metal elongated slug, referred to as a penetrating jet, that can travel typically at speeds above 9.66 kilometers per second (6 miles per second). The high velocity, high density jet is able to pierce metal armors and other similar re-enforced targets.

Present-day EFP warheads exhibit several drawbacks, however. Some conventional EFP warheads use multiple EFPs that are projected forward in a unidirectional, i.e., single, direction. Accordingly, such EFP warheads are useful against a single armored vehicle. However, where numbers of tanks, vehicles, ships, jets, helicopters, and the like are positioned and/or may be advancing from several directions in a 360 degree battlefield theater, time is critical to the outcome of the battle. The effectiveness of a single or multiple EFPs unidirectionally projected becomes insufficient to gain ground on the battlefield theater.

In addition, having recognized the vulnerability of battlefield armors to high velocity penetrating jets, armor manufacturers have advanced today's battlefield armor design significantly. Through the use of ceramic materials and advanced composites, effectiveness of EFPs has decreased from a lethality standpoint and are much less damaging to an armor.

Accordingly, it is desirable to provide a multidirectional, spherically-shaped explosive device with significantly more lethality and higher destructive effects than conventional warheads. In addition, it is desirable to provide a spherically-shaped explosive device having a plurality of liners that are projected uniformly and radially from a center point of the device upon detonation of the device. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

BRIEF SUMMARY OF THE INVENTION

Explosive devices, and in particular cluster explosively-formed penetrator warhead devices, are described herein. In accordance with an exemplary embodiment, a spherically-shaped explosive device comprises an initiator, a fuze component system configured to ignite the initiator, and a substantially spherical explosive charge encasing the initiator. The substantially spherical explosive charge has a substantially spherical surface. A plurality of liners are on the substantially spherical surface of the substantially spherical explosive charge.

In another exemplary embodiment, a cluster explosively-formed penetrator (CEFP) warhead comprises a spherically-shaped explosive charge having a surface comprising a plurality of non-overlapping dimples, a means for detonating the spherically-shaped explosive charge, and a plurality of liners. Each liner is embedded in one of the plurality of non-overlapping dimples.

In a further exemplary embodiment, a warhead comprises an initiator, a fuze component system configured to ignite the initiator, and a spherically-shaped explosive charge encasing the initiator and having a center point. The spherically-shaped explosive charge comprises a PBX composition comprising octanitrocubane homogeneously dispersed within a binder matrix. A booster charge is interposed between the initiator and the spherically-shaped explosive charge. A plurality of non-overlapping liners is on the spherically-shaped explosive charge. Each of the plurality of non-overlapping liners has a central axis that extends through the center point of the spherically-shaped explosive charge.

DETAILED DESCRIPTION OF THE INVENTION

The various embodiments contemplated herein relate to spherically-shaped explosive devices that exhibit superior explosive output and thus, upon detonation, are capable of projecting liners or penetrators in a three-dimensional direction. In particular, various embodiments contemplated herein are directed to cluster explosively-formed penetrator (CEFP) warheads having a number of liners on a spherically-shaped explosive charge. Upon detonated, the explosive charge projects the liners, at hypervelocity, in three-dimensions. The liners are positioned on the warhead with a central axis that runs through the center point of the warhead. The lines are of such a size and are uniquely offset from each other so that, upon detonation of the warhead, each travels upon a unique forward path. As the liners travel at hypervelocity, they invert and collapse upon their axes to become high kinetic energy slugs or penetrators of molten metal. (The terms liner and penetrator will be used herein interchangeably.) Such shaped devices are effective penetrators of targets formed from single or multiple layers of materials such as rolled steel armor. Because the the penetrators are projected at hypervelocity in a 360 degree direction, the penetrators can pierce armors of land, air, and sea vehicles substantially simultaneously.

Referring toFIGS. 3 and 4, in accordance with an exemplary embodiment, a CEFP warhead20comprises an ignition train of at least one initiator22. The initiator22may comprise azide-based explosives such as lead azide and lead styphnate, lead picrate, mercury fulminate, zirconium potassium perchlorate (ZPP) and derivatives thereof, thermite, combinations thereof, and the like. In a preferred embodiment, the initiator comprises an insensitive munition-type (IM) explosive material of cis-bis-(5-nitrotetrazolato) tetramine cobalt (III) perchlorate (hereinafter “BNCP”), also referred to as Bis, nitro-cobalt-III-perchlorate, particles, and desensitized BNCP, essentially BNCP that is encapsulated by a surfactant. Explosives with IM properties are capable of withstanding sympathetic detonation as a result of mechanical shocks, fire, electrostatic discharge, and impact by shrapnel, yet is still capable of high-order detonation per design intent. Explosive materials comprising surfactant-encapsulated BNCP particles and methods for manufacturing the explosive materials are disclosed in U.S. patent application Ser. No. 12/636,935 filed Dec. 14, 2009 by the same inventors of the inventions disclosed herein.

A fuze component system24is physically and/or electrically coupled to the initiator22and comprises a fuze to ignite the initiator upon receiving a signal. The signal can be transmitted to the fuze component system via radio or electromagnetic waves from a transmitter located remote from the CEFP warhead and can be received by a receiver within the CEFP warhead within or outside of the fuse component system. The fuze component system may include a sensor (not shown) such as, for example, a height-of-burst sensor, an acceleration-deceleration sensor, an impact sensor, a pressure sensor, a time delay sensor, a heat sensor, an optical sensor, a microelectromechanical (MEMs) sensor, or a combination thereof, that can activate the fuze component system24to ignite the fuze. The sensor can be configured to provide the signal to the fuze component system24based upon acceleration, height, barometric pressure, electronic, or dynamic movement of the CEFP warhead20, a predetermined time or time period, distance from a target, or a combination thereof. For example, the sensor may be able to sense the distance the CEFP warhead is from the ground or from an object/target on the ground and, thus, transmit a signal to the fuze component system24that activates the initiator22so that the CEFP warhead detonates at predetermined distances from enemy tanks, vehicles, missile launchers, mine fields, etc., on the ground, bunkers, enemy aircrafts, helicopters, etc., in the air, and/or submarines, boats, aircraft carriers, underwater mine fields, etc., in the water. While CEFP warhead20is shown inFIG. 4with one fuze component system24, it will be appreciated that CEFP warhead20may comprise multiple fuze components systems24for igniting initiator charge22.

In an optional embodiment, a secondary explosive, or booster, charge28may encase the initiator22by being cast about the initiator22and, in turn, is encased by a main explosive charge having IM properties. The booster charge may comprise materials such as PBXN-5, PBXN-7, PBXN-9, CH-6, and the like. The CEFP warhead20is detonated when the initiator22is ignited by the fuze component system24, generating a shock wave in the booster charge28that detonates the main explosive charge26. In other embodiments, such as when the initiator22is sufficiently brisant, a booster charge28may not be necessary and the initiator22may be used to detonated the main explosive charge26.

The initiator22, and the booster charge28if present, is encased by the substantially spherically-shaped main explosive charge26that is detonated upon ignition of the initiator22. A substantially spherical surface27of the main explosive charge26has a plurality of recessed and concave cavities or dimples25that have been formed thereon. Each dimple has a center point29and an axis31that extends through the center point29and to a center point54of the CEFP warhead20. Each axis31of the dimples25only intersect at center point54. Further, the dimples are of such a size, to be discussed in further detail below with respect to liners36, that they do not overlap.

In one exemplary embodiment, the main explosive charge26is a plastic-bonded explosive, also called a PBX or a polymer-bonded explosive. A PBX generally contains an energetic fuel or “oxidizer” homogeneously dispersed in a matrix of a synthetic thermoset or thermoplastic polymer commonly referred to as a “binder matrix”. In this form, the PBX is a high output explosive and may be formulated to exhibit IM properties. Conventional PBXs typically comprise oxidizers such as HMX (or “high melting point explosive”), chemically known as cyclotetramethylene tetranitramine, RDX (or “royal demolition explosive”), chemically known as cyclotrimethylene trinitramine, C1-20, chemically known as 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, TATB, chemically known as triaminotrinitrobenzene (also using IUPAC designation, 3,5-triamino-2,4,6-trinitrobenze), FOX-7, also known as 1,1-diamino-2,2-dinitroethene (DADNE), or combinations thereof.

In a preferred embodiment, the main explosive charge26is a PBX composition having an oxidizer comprising octanitrocubane (ONC) homogeneously and intimately dispersed within a binder matrix. ONC has the empirical formula C8N8O16and the structure illustrated inFIG. 5. The heat of formation of ONC is about +163 kilocalories per mole (Kcal/mole) and the theoretical density of ONC is in the range of about 1.92 to about 2.2 g/cm3. Important factors in determining explosive output are the heat of formation and the theoretical density, as the Velocity of Detonation (VOD) is directly proportional to the square of the theoretical density and the detonation pressure (PCJ) is proportional to the theoretical density. ONC is extremely insensitive and considered as the most powerful non-nuclear explosive with superior energy density compared to HMX (theoretical density of 1.86-1.91 grams per cubic centimeter (g/cm3)), RDX (theoretical density of 1.80-1.82 g/cm3), and C1-20 (theoretical density of 1.90-2.04 g/cm3). In this regard, an ONC-based PBX composition comprising ONC and a thermoset resin or high-temperature, high-performance thermoplastic elastomer has a VOD of about 9-11 kilometers per second (km/s), which is about 11-23% greater than that of a comparable HMX-based composition (about 8.5-9.8 km/s). Further, an ONC-based PBX composition has a PCJof about 465-625 kilobars, about 34% greater than the PCJof a comparable HMX-based PBX composition (about 396.3 kilobars).

ONC has a zero “oxygen balance” and therefore is capable of complete combustion in the absence of air under ideal conditions. “Oxygen balance” is a ratio of the amount of oxygen in an explosive to the amount of oxygen needed for complete combustion, which dictates the extent of the combustion reaction and the composition of the by-products of the combustion or detonation. The fewer solid byproducts and the more moles of gas produced during combustion of an explosive, the greater the detonation pressure of the explosive. When synthesized stoichiometrically, ONC is a solid, white, granular powder that decomposes upon melting at a temperature of about 297° C. according to the following reaction scheme:
C8(NO2)8→8CO2+4N2, ΔH+163 Kcal/mole.
Thus, because the byproducts of the combustion of ONC are carbon dioxide and nitrogen gases, and because of ONC's high positive heat of formation, ONC has superior detonation output compared to prior art explosives. In addition, ONC is markedly insensitive to shock, impact and electrostatic discharge and is thermally-stable when formulated into the PBX composition using temperatures of up to 350° C. In one exemplary embodiment, the PBX composition comprises ONC oxidizer in the range of about 80 to about 98 weight percent (wt. %) of the PBX composition.

The ONC is mixed and distributed homogenously throughout the binder matrix of the PBX composition and can be present in the PBX composition in one or various particle sizes. For example, in one embodiment, ONC is present as particles with substantially the same dimensions or sizes. In a second embodiment, the ONC is bimodal, having, for example, a blend of coarse ONC particles with a particle size distribution of about 150 to about 400 micrometers (μm) and fine particles with a particle size distribution of about 15 to about 45 μm. In a third embodiment, the ONC is bimodal, having a blend of coarse and fine particles in the ratio of about 5:2, respectively. In a fourth embodiment, the ONC is trimodal, having, for example, a blend of coarse ONC particles with a particle size distribution of about 150 to about 400 μm, fine particles with a particle size distribution of about 15 to about 45 μm, and ultrafine particles with a particle size distribution of about 1 to about 15 μm. In a fifth embodiment, the ONC is trimodal, having a blend of coarse, fine, and ultrafine particles in the ratio of about 5:3:2, respectively. Of course, the ONC particles may be present in any other sizes and size distributions suitable for a particular explosives application.

Depending on a desired explosives application, in addition to ONC, the oxidizer of the PBX composition may also comprise other oxidizers, such as TATB, DADNE, HMX, RDX, C1-20, or combinations thereof. For example, in various explosives applications, it may be desirable to combine oxidizers that impart different characteristics, namely, ballistics properties coupled with mechanical properties, mechanical properties coupled with ease of processing properties, or consolidation characteristics coupled with particle size and hardness properties, etc. Alternatively, in other various explosives applications, it may be desirable to minimize cost of the PBX composition by using an oxidizing component that can be purchased at a lower price than ONC. Most desirably, a PBX composition that imparts the highest IM properties and the highest explosive output is used. Thus, a preferred embodiment comprises ONC, TATB, DADNE, HMX, C1-20, or combinations thereof. In one embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 to about 5 wt. % HMX. In a second embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 to about 5 wt. % C1-20. In a third embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 to about 5 wt. % RDX. In a fourth embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 to about 5 wt. % aluminum. In a fifth embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 go about 5 wt. % TATB. In a sixth embodiment, the oxidizer may comprise from about 5 to about 95 wt. % ONC and from about 95 to about 5 wt. % DADNE. In a seventh embodiment, the oxidizer may comprise from about 5 to about 5 wt. % ONC and from about 95 to about 5 wt. % of any combination of TATB, DADNE, HMX, RDX, C1-20, aluminum, and/or other oxidizers.

The various embodiments of the PBX composition also contain a binder matrix comprised of a thermoset synthetic resin or a high-temperature, high-performance thermoplastic synthetic elastomer. The binder matrix, in addition to allowing the PBX composition to be manipulated during fabrication into various shapes and forms, also serves as a desensitizer and a fuel for the detonation of the PBX composition. The binder matrix is the backbone component used in the PBX composition, as it provides the skeletal structure for the explosive charge upon which the remaining constituents reside. The binder matrix can comprise energetic or inert synthetic resins. Examples of inert synthetic resins suitable for use in various embodiments of the PBX composition include, but are not limited to, polysulfone (PS), polyether sulfone (PES), polyphenyl sulfone (PPS), polyphenylene sulfide, Viton® fluoroelastomer available from DuPont Performance Polymers of Wilmington, Del., PTFE and other fluoropolymers, polyaryl ketones, such as polyetherether ketone (PEEK), polyetherketone (PEK), and polyetherketoneketone (PEKK), polyisobutylene (PIB), hydroxyl-terminated polybutadiene (HTPB), carboxyl-terminated polybutadiene (CTPB), polybutadiene-acrylic acid-acrylonitrile (PBAN), polyurethanes, polyesters, polyimides, cellulose acetate (CA), cellulose acetate butyrate (CAB), ethylene vinyl acetate (EVA), and combinations thereof. Examples of energetic synthetic resins suitable for use in various embodiments of the PBX composition include, but are not limited to, glacidyl azide polymer (GAP), nitropolyurethanes, nitrocellulose, polyvinyl nitrate, and combinations thereof. In one preferred embodiment, the synthetic resin comprises polyisobutylene (PIB). In another preferred embodiment, the PBX composition comprises a synthetic resin in an amount of from about 2 to about 20 wt. % of the PBX composition. ONC-comprising PBX materials and methods for manufacturing the compositions are disclosed in U.S. patent application Ser. No. 12/579,202 filed Oct. 14, 2009 by the same inventors of the CEFP warheads contemplated herein.

A spherical case or housing30comprising a rigid, hollow sphere contains the main explosive charge26and the ignition train comprising the fuze component system24, the initiator22, and the booster charge28. The housing may be fabricated from a metal, such as steel or aluminum, or any other suitable structural composite, such as a carbon fiber composite. The housing comprises a number of circular openings32. The openings32may be but are not necessarily spaced equidistance from each other across a surface34of the housing30. The circular openings may be all of the same diameter or may have various diametric openings, optimally spaced without overlapping and in a manner that imparts most effective functionality of the liners, without compromising performance or reliability.

The CEFP warhead20further comprises a plurality of liners36. Each liner is positioned within one of the circular openings32of the housing30and is embedded, pressed or otherwise positioned against a concave, recessed dimple25of the surface27of the main explosive charge26. Each liner further comprises an axis50that extends through a center point52of the liner, to the center point54of the CEFP warhead20, and is uniaxial with the axis31of the dimple25within which it resides. In this regard, the liners may be but are not necessarily uniformly spaced from each other, are centered within the dimples25of the explosive charge26, and are of a size such that they do not overlap.FIG. 6is a side cross-sectional close-up view of the liner36embedded against the main explosive charge26. A retaining ring or similar retainer38may be used to retain the liner within the housing30. In one exemplary embodiment, as in the case of an explosive charge penetrator geometry (EFP geometry), the liner has an arc-shaped geometry, as illustrated inFIG. 6. The arc can have an apex angle41of from about 130 to about 175 degrees. The liner can range in diameter depending on armor penetration depth requirements but is no less than twice a predetermined penetration depth and no more than ⅓ the main explosive charge diameter. The liner thickness may be in the range of about 3% to about 5% of the main explosive charge diameter. In another exemplary embodiment, as in the case of a shaped-charge (SC) geometry, the liner has a trumpet geometry or, as illustrated inFIG. 7, a conical geometry, having an apex angle designated by double-headed arrow44. The apex angle may be in the range of about 15 to about 125 degrees. The liner may be made of any suitable ductile, dense metal material. The penetration of the liner through re-enforced military armor steel is proportional to the density of the material from which it is made. Examples of suitable materials include copper, molybdenum, tungsten, aluminum, tantalum, depleted uranium, lead, tin, cadmium, cobalt, magnesium, titanium, zinc, zirconium, beryllium, nickel, silver, or any combinations, thereof. Alternatively, the liner may be made from rhenium, palladium or combinations thereof, as set forth in the U.S. application entitled “Improved Liners for Warheads and Warheads Having Improved Liners,” filed on the same date as this disclosure and co-owned by the assignee of this disclosure.

FIGS. 8-10illustrate the CEFP warhead20following detonation. Detonation of the initiator22by the fuze component system24generates a shock wave in the booster charge28that travels through the main explosive charge26. Upon the violent initiation of the main explosive charge26, the liners36are expelled forward in a 360 degree spread. As illustrated inFIG. 10, the liners collapse upon themselves and invert, transforming into carrot-shaped penetrator jets of molten metal slugs. The penetrator jets travel at hypervelocity speeds. For example, the penetrators can travel at speeds of 9 to 10 kilometers per second. The kinetic energy of the penetrator/slug is a product of the mass of the material that forms the penetrator/slug and the velocity of the penetrator/slug. Such shaped devices are effective penetrators of targets formed from single or multiple layers of materials such as rolled steel, ceramic, or composite armors. Because the explosive charge projects the liners, at hypervelocity, in a 360 degree direction, the hypervelocity penetrators/slugs can pierce armors of land, air, and sea vehicles substantially simultaneously.