Low collateral damage bi-modal warhead assembly

Abstract

A warhead assembly, comprising a cylindrical or conical metal body, having an inner wall with a plurality of channels or grooves extending parallel to a central longitudinal axis. Preformed fragments are inserted in the channels or grooves and a liner with an explosive fill is positioned within the metal body, retaining the preformed fragments in place. The warhead assembly on detonation produces a bimodal distribution of fragments with adequate mass and velocity with optimized mixed fragmentation that defeats or otherwise incapacitates a target or set of targets.

Claims

1. A warhead assembly, adapted to be mounted at the head of a missile or projectile designed to deliver the warhead assembly to a target, said warhead assembly comprising, in combination: (a) a round metal body having an inner wall with a plurality of grooves extending parallel to a central longitudinal axis of the metal body; (b) a plurality of preformed fragments inserted in the grooves in said inner wall; (c) a liner, thinner than said metal body, positioned within the metal body and configured to retain the preformed fragments in place in said grooves; and (d) an explosive fill inside the liner; whereby the warhead assembly on detonation produces a bimodal distribution of fragments with adequate mass and velocity to create an optimized mixed fragmentation effect on the target that can defeat the target even when it is fitted with ballistic protection and/or when it comprises mixed targets of both enemy vehicles and personnel.

2. A warhead assembly, as recited in claim 1, wherein the liner physically separates the preformed fragments from the explosive fill.

3. A warhead assembly, adapted to be mounted at the head of a missile or projectile designed to deliver the warhead assembly to a target, said warhead assembly comprising, in combination: (a) a round metal casing having an outer surface with an aeroballistic shape and an inner wall with a plurality of grooves extending parallel to a central longitudinal axis thereof, said grooves being of such a size as to contain and fit preformed fragmentation elements; (b) a plurality of preformed metal fragmentation elements disposed in said grooves in the casing and balanced to provide for a stable gyroscopic spin of the warhead assembly and its delivery missile or projectile when in ballistic flight; and (c) an explosive charge within the metal casing; wherein distances between the grooves along the casing surface and depths of the grooves produce a fragmentation of the metal casing such that, on detonation of the explosive charge, the fragmentation is substantially shaped and defined by the grooves; whereby the combined effect of the metal casing fragmentation and the preformed fragmentation elements creates a terminal effect upon said detonation, exhibiting a multimodal distribution of fragments with an optimized effect on the target that defeats the target when it is either a single target or a mixed target of enemy vehicles and personnel.

4. A warhead assembly, as recited in claim 3, wherein the grooves extend forward along the inner wall of the casing from a vicinity of a base thereof which is attachable to the missile or projectile toward a nose thereof.

5. A warhead assembly, as recited in claim 3, wherein the grooves extend rearward along the inner wall of the casing from the vicinity of a nose thereof toward a base thereof which is attachable to the missile or projectile.

6. A warhead assembly, as recited in claim 3, wherein the grooves extend along the inner wall of the casing from a vicinity of a base thereof which is attachable to the missile or projectile to a vicinity of a nose thereof.

7. A warhead assembly, as recited in claim 3, wherein shaping of the casing fragments, upon detonation, is influenced by effects the preformed metal fragmentation elements interacting with an overall geometry of the metal casing, as determined by at least one parameter selected from the group consisting of: (a) casing wall thickness, (b) distance between the casing grooves, (c) depth of the casing grooves, (d) type of metal forming the casing, and (e) a forming process used in producing the casing.

8. A warhead assembly, as recited in claim 3, wherein the preformed metal fragmentation elements fit tightly into the grooves' inner channels and thereby substantially retain their form after detonation.

9. A warhead assembly, as recited in claim 3, wherein the shape of the preformed metal fragmentation elements is selected from the group consisting of spheres, notched rods, wire and cylindrically shaped rods.

10. A warhead assembly, as recited in claim 3, further comprising a nose cap fitted to the metal casing, on an end thereof opposite to the end which is fitted to the missile or projectile, said nose cap incorporating a fuze that initiates a detonation in a designated post firing or launch environment.

11. A warhead assembly, as recited in claim 3, further comprising a fuze fitted to the metal casing, at a base thereof which is fitted to the missile or projectile, that initiates a detonation in a designated post firing or launch environment.

12. A warhead assembly, as recited in claim 3, further comprising a liner, housing an explosive fill, positioned within the casing and retaining the preformed metal fragmentation elements in place, said liner physically separating the preformed metal fragmentation elements from the explosive fill.

13. A warhead assembly, as recited in claim 12, wherein the metal casing and the preformed metal fragmentation elements fitted into the grooves, coupled with the liner, form a configuration that mitigates the impact threat from an assailant projectile or fragment deep penetration into the cavity housing the warhead assembly's explosive fill.

14. A warhead assembly, as recited in claim 13, wherein a diversion of an assailant projectile or fragment attack reduces the peak pressure imparted directly on the explosive fill housed in the warhead assembly and thereby reduces the peak pressure point precluding the detonation of the warhead's explosive, reducing the overall sensitivity to outside stimuli of an assailant projectiles or fragments.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows cutaway views of a 40 mm warhead assembly according to a preferred embodiment of the present invention.

(2) FIG. 1B shows cutaway views of a 105 mm warhead assembly according to a preferred embodiment of the present invention.

(3) FIG. 1C shows cutaway views of a 155 mm warhead assembly according to a preferred embodiment of the present invention.

(4) FIG. 2A is a view of a 40 mm warhead body with internal grooves according to a preferred embodiment of the present invention.

(5) FIG. 2B is a view of a 105 mm warhead body with internal grooves according to a preferred embodiment of the present invention.

(6) FIG. 2C is a view of a 155 mm warhead body with internal grooves according to a preferred embodiment of the present invention.

(7) FIG. 3A is a view of a 40 mm projectile with spherical pre-fragments according to a preferred embodiment of the present invention.

(8) FIG. 3B is a view of a 105 mm projectile with cylindrical or notched wire preformed fragments according to a preferred embodiment of the present invention.

(9) FIG. 3C is a view of a 155 mm projectile with notched rods according to a preferred embodiment of the present invention.

(10) FIG. 4A is a view of a 40 mm liner and spherical preformed fragments according to a preferred embodiment of the present invention.

(11) FIG. 4B is a view of a 105 mm projectile liner and cylindrical or notched wire preformed fragments according to a preferred embodiment of the present invention.

(12) FIG. 4C is a view of a 155 mm line and notched rod preformed fragments according to a preferred embodiment of the present invention.

(13) FIG. 5A shows typical bimodal distributions for a warhead assembly according to the present invention.

(14) FIG. 5B shows a typical multimodal distribution for a warhead assembly according to the present invention.

(15) FIG. 5C shows a multimodal distribution with confidence levels for a warhead assembly according to the present invention.

(16) FIG. 5D shows an estimated 155 mm fragment mass distribution (total Fragment Weight) for a warhead assembly according to the present invention.

(17) FIG. 5E shows an estimated 155 mm fragment mass distribution (total Fragment Count) for a warhead assembly according to the present invention.

(18) FIG. 6A is a cross sectional view of a 40 mm warhead assembly according to a preferred embodiment of the present invention.

(19) FIG. 6B is a cross sectional view of a 105 mm warhead assembly according to a preferred embodiment of the present invention.

(20) FIG. 6C is a cross sectional view of a 105 mm warhead assembly according to a preferred embodiment of the present invention.

(21) FIG. 7A is a diagram of preformed fragments for a warhead assembly according to the present invention.

(22) FIG. 7B is a diagram of fragments from a warhead body according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

(23) The preferred embodiments of the present invention will now be described with reference to FIGS. 1-7B of the drawings. Identical elements in the various figures are designated with the same reference numerals.

(24) Assembly:

(25) FIG. 1 depicts a view of 40 mm bimodal warhead assembly. FIG. 2 depicts views of a 105 mm bimodal projectile assembly. FIG. 3 depicts views of a 155 mm bimodal projectile body. The warhead assembly includes a fuze (110), and may include a body form (120). The warhead body (130) may also include a driving band (140). The warhead body (130) includes channels or grooves (220) that when assembled house preformed fragments (150). Where setback forces or loading techniques necessitate, a liner (160) may be added to retain the preformed fragments (150) in position and separate the explosive fill (170), and simplify the loading of an appropriate explosive fill. The axis of rotation (180) is also depicted about which the fragment (density) and location are matched in each channel providing the warhead with good gyroscopic balance characteristics.

(26) Liner:

(27) FIGS. 1-3 depict how the liner (160) firmly fits to the warhead's metal body (130) and the preformed fragments (150). An explosive fill (170) is cast, pressed or melt poured into the liner. FIGS. 4A-4C illustrate how the liner interfaces with the preformed fragments (150). The liner (160) can be constructed with a density and geometry to mitigate impact and insulate the explosive from aerodynamic heating encountered in flight.

(28) Preformed Fragments:

(29) FIGS. 4A-4C and FIG. 7A depict how pre-fragmented fragments (150) are metal spheres (310), cylinders produced with cut metal rods or cut wire (320), or notched rods (330).

(30) Warhead Body:

(31) FIGS. 2A-2C depict how the warhead body (130) includes channels or grooves (220). FIGS. 6A-6C cross-sectional views that depict grooves (220), included as a feature in the inner diameter (690) of a warhead body (130). In medium caliber projectiles such as the 40 mm warhead body depicted in FIG. 2A, channels may be produced from progressive metal work such as flow forming and post forming machining. In large projectiles, as depicted in FIGS. 2B and 2C, channels may be forged or cast and/or machined. The channels, grooves and preformed fragments, when viewed from the side orientation of the projectile, are parallel or conical to the axis of rotation (180) as seen in the side cutaway views in FIGS. 1A, 1B and 1C. The construction materials and geometry, with groves housing preformed fragments, provide a highly gyroscopically balanced warhead assembly about the axis of rotation (180). The cross sectional views of FIGS. 6A-6C depict features such as warhead body (max) wall thickness (610), depth of grooves (620), warhead body wall thickness (min)(630), and placement of preformed fragments (150) and a liner (160) filled with an explosive (170) about the center of rotation (180).

(32) Fracture Mechanics and Physics Creating Fragments from the Warhead Body:

(33) Again referring to FIGS. 6A-6C it is useful to discuss how detonation creates fragments out of the warhead body (130). In the initial microseconds after the initiation of a warhead detonation, pressure expands the warhead body (130) until the stretching metal yields creating a symmetrical fracture (650) in the vicinity of warhead body's thinnest wall (620). The fracture (650) induced at detonation by the wall yielding occurs under the tremendous expansion pressure of detonation. The underlying metallurgy, grooves (220) housing preformed fragments (120) influence the creation of fragments at detonation as the groove to groove spacing (640) and depth of the grooves (620) and the wall thickness (610) produce in detonation a fragment of a predictable size (670). The fragmentation of the other wall may result in the loss of some metal mass (740) which is effectively transformed into unrecoverable micro fragments. With fracture of the outer case, pre-fragmented metal (120) housed in the channels is propelled and enveloped by the escaping gases of detonation. While the process of detonation may slightly reduce the mass of a pre-fragmented projectile (120), these fragments are ejected at high velocity based on the warhead assembly's orientation.

(34) Post Detonation Fragment Distribution:

(35) Reference to FIGS. 5A-5E is useful in considering the generation of fragments. Post detonation recovery of fragments verifies that the detonation of warheads based on designs according to the invention produces a bimodal (or multimodal) distribution of fragments where a horizontal scale (510) categorizes recovered fragments, a vertical scale categorizes fragment weight (or mass) (520) and fragment count (530) where the pattern of fragments includes at least two modes (540, 550) about a mean value (570) and median value (580). The fragment pattern distribution is identified with greater degrees of confidence (592, 594, 596) which is useful in establishing the likelihood that the warheads will create unintended collateral damage.

(36) Bimodal or Multimodal Distribution of Fragments:

(37) When operating against a single target, fragments produced from detonation of the assembly have a bimodal distribution (540, 550) to incapacitate targets with both fragments from the warhead body (670, 710, 720, 730) and preformed fragments (150). A bimodal (540, 550) multimodal (540, 550, 560) distribution of fragments is useful in defeating certain targets or target sets as set forth in the following example:

(38) A bimodal or multimodal distribution of fragments are useful in defeating a single target as provided in Example 1.

(39) Example 1:

(40) An enemy soldier with a flak jacket creates a difficult target to incapacitate inasmuch as a certain geometry, mass and velocity will optimize performance in penetrating a flak jacket while a different geometry, mass and velocity will optimize performance against exposed limbs.

(41) In other cases, when operating against multiple targets (a target set composed of both enemy soldiers and equipment), a bimodal distribution of fragments is desired, so that a different velocity, fragment mass and geometry is an optimized defeat mechanism for mixed targets.

(42) Example 2:

(43) To defeat a mixed target set with a unitary warhead is challenging. To defeat such targets, the impact energy of larger fragments should produce a desired terminal effect against vehicles while smaller fragments spread with a greater density (spacing) in the target area producing a desired incapacitation of enemy soldiers.

(44) Geometry of Inset Channels and Warhead Body Fragmentation:

(45) The outer warhead has a maximum wall thickness (610), groove depth (620) and a minimum wall thickness (630) and a specified groove-to-groove radial spacing (640). The foregoing geometry induces the creation of a fracture point (650) at the thinnest point in the warhead wall at detonation, such that the warhead body provides adequate structural strength at setback and in flight. The liner (150) fits into the warhead body's inner diameter (690). Fragmentation is directly influenced by groove depth (620), radial spacing (640) and the shape of the channels or grooves (220) in the warhead. The size of fragments produced by detonation of the warhead body (710, 720, 730 and 670) produce one mode (550) as depicted in FIG. 5A, 5B or 5C. Some mass of the outer wall may be lost as a result of detonation (740).

(46) Characteristics of Preformed Fragments:

(47) The explosive fill (140) is cast, pressed or melt-poured into the liner as depicted in FIGS. 1A-1C. At detonation, preformed fragments are ejected at a velocity and a reliable size that, measured after recovery, fall within a specific measured mode (540).

(48) Multimodal Rear Fragmentation:

(49) At the rear of a 40 mm projectile, a designer may wish to provide adequate confidence in “safe separation” to protect the gunner firing the projectile. Since a variation of design at the rear of the warhead may not degrade the gyroscopic balance of a projectile, it is possible to introduce a multimodal design with rearward fragment throw that varies from the side fragments thrown from a projectile. In these circumstances, the rearward fragments optimized for short range effect, while still affording safe separation, would create a third mode (560) when the fragments are recovered.

(50) There has thus been shown and described a novel bimodal warhead assembly which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.

REFERENCE NUMBERS

(51) 110 Fuze 120 Body Form 130 Warhead Body 140 Driving Band 150 Preformed Fragments 160 Liner 170 Explosive Fill 180 Axis of Rotation 210 Fuze Well 220 Channels or Grooves 310 Metal Spheres 320 Notched Wire or Forms Using Cylinders 330 Notched Rods 510 Horizontal Scale—Weight Category of Fragments from Warhead Assembly 520 Vertical Scale A—Total Weight of Fragments by Weight Category 530 Vertical Scale B—Number of Fragments by Weight Category 540 Mode 1 550 Mode 2 560 Mode 3 570 Mean Value 580 Median Value 590 Distribution 592 Distribution with 1σ Confidence 594 Distribution with 2σ Confidence 596 Distribution with 3σ Confidence 610 Warhead Body (Max) Wall Thickness 620 Depth of Grooves 630 Warhead Body (Min) Wall Thickness 640 Groove to Groove Radial Separation 650 Outer Body Fracture Point 660 Fragment Location 670 Estimated Fragment Size from outer wall 680 Outer Diameter 690 Inner Diameter 710 40 mm Outer Wall Fragment 720 105 mm Outer Wall Fragment 730 155 mm Outer Wall Fragment 740 155 mm Outer Wall Fragment with Mass Loss