US20070006768A1

US20070006768A1 - Mushroom warhead

Info

Publication number: US20070006768A1
Application number: US11/174,486
Authority: US
Inventors: Gilad Peleg; Yacob Hal Wani; Menashe Bar
Original assignee: Rafael Advanced Defense Systems Ltd
Current assignee: Rafael Advanced Defense Systems Ltd
Priority date: 2005-07-06
Filing date: 2005-07-06
Publication date: 2007-01-11

Abstract

A warhead including a first section with a dish-shaped first fragmentation layer, and a second section with a barrel-shaped second fragmentation layer.

Description

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to fragmentation warheads and, more particularly, to a fragmentation warhead that achieves wide angular coverage.
In attacking a ground target with a guided missile, it is desirable to get a reasonable dense coverage by the missile's explosive charge over a broad angle, relative to the missile axis, to take into account the fact that the target might not be a point target but might instead be dispersed around the aiming point, and also to take into account the fact that the actual point of impact could be displaced from the aiming point. FIG. 1 is a schematic axial cross section of the forward part of a guided missile 10 with the prior art barrel-shaped fragmentation warhead 12 of Zulkoski et al., U.S. Pat. No. 5,038,686, which patent is incorporated by reference for all purposes as if fully set forth herein. Guided missile 10 also includes, forward of warhead 12, a seeker head 14 for guiding guided missile 10 to its target. FIG. 2 is a partial schematic axial cross section of warhead 12, showing that warhead 12 consists of a central explosive charge 16 encased by a fragmentation layer 18 and two bulkheads 20 and 22. Explosive charge 16 also has a cylindrical recess 24 for a detonation fuse. Fragmentation layer 18 is a barrel-shaped layer of tungsten cubes held in a binder of potting material.
FIG. 3 shows the angular fragmentation pattern of warhead 12 when warhead 12 is detonated. This angular fragmentation pattern is the envelope of the angular distribution of the trajectories of the fragments (the tungsten cubes in this case) of fragmentation layer 18 when warhead 12 is detonated. The abscissa is azimuth, in degrees, laterally around guided missile 10 and warhead 12, and the ordinate is polar angle, in degrees, relative to the cylindrical symmetry axes of guided missile 10 and warhead 12, assuming that these axes are coincident. A polar angle of zero degrees is straight forward relative to guided missile 10. A polar angle of 180 degrees is straight aft relative to guided missile 10. Warhead 12 achieves annular coverage. i.e. a full 360 degrees of azimuthal coverage but only partial (120 degrees) polar angle coverage and no axial (straight forward or straight aft) coverage. In particular, a 60 degree solid angle forward of guided missile 10 is left uncovered. Continuing fragmentation layer 18 to cover the forward part of warhead 14 in place of bulkhead 22 would provide forward coverage, except that the fragments emerging from warhead 12 in the forward direction would lose kinetic energy while traversing seeker head 14 and would emerge from guided missile 10 with insufficient kinetic energy to inflict damage on the target.
There is thus a widely recognized need for, and it would be highly advantageous to have, a fragmentation warhead, for a guided missile, that achieves uniform forward and lateral coverage.

SUMMARY OF THE INVENTION

According to the present invention there is provided a warhead including: (a) a first section including a substantially dish-shaped first fragmentation layer; and (b) a second section including a substantially barrel-shaped second fragmentation layer.
According to the present invention there is provided a method of designing a warhead to fit inside a space bounded by an envelope, including the steps of: (a) selecting a first radius of curvature sufficient to provide a desired fragment density; (b) selecting a first center of curvature within the space; (c) drawing a first circular arc centered on the first center of curvature and having the first radius of curvature until the first circular arc intersects the envelope; (d) drawing a straight line from the intersection of the first circular arc with the envelope through the first center of curvature; (e) selecting a second radius of curvature sufficient to provide the desired fragment density; (f) selecting a second center of curvature; and (g) drawing a second circular arc centered on the second center of curvature and having the second radius of curvature, the second circular arc starting from the straight line, the first circular arc and a portion of the straight line between the first and second circular arcs defining a first section of the warhead, the second circular arc defining a second section of the warhead.
The warhead of the present invention includes two sections, an aft section similar to prior art warhead 12, and a forward section with a substantially dish-shaped forward-facing fragmentation layer. Preferably, the forward-facing fragmentation layer is concave towards the second section.
FIGS. 4A and 4B are partial schematic axial cross sections of two basic embodiments 30A and 30B of the warhead of the present invention. The forward section 32A of embodiment 30A includes a substantially dish-shaped forward-facing fragmentation layer 36A and a forward explosive charge 40A. The aft section 34A of embodiment 30A is geometrically similar to prior art warhead 12, and includes an aft fragmentation layer 38A and an aft explosive charge 42A. Fragmentation layer 36A is concave towards aft section 34A. Similarly, the forward section 32B of embodiment 30B includes a substantially dish-shaped forward-facing fragmentation layer 36B and a forward explosive charge 40B; the aft section 34B of embodiment 30B, which also is geometrically similar to prior art warhead 12, includes an aft fragmentation layer 38B and an aft explosive charge 42B; and fragmentation layer 36B is concave towards aft section 34B. Having two separate fragmentation layers provides fragmentation coverage in the forward direction as well as laterally; but of the two embodiments, only embodiment 30B is sufficiently long and heavy to generate fragments with a velocity sufficient to traverse seeker head 14 and exit with sufficient residual velocity to inflict damage on the target.
Nevertheless, as discussed below, in preferred embodiments of the warhead of the present invention, the two sections share a single common explosive charge that, when detonated, produces both a forward fragmentation pattern corresponding to the forward-facing fragmentation layer and an aft fragmentation pattern corresponding to the aft fragmentation layer. The common explosive charge includes a recess for a fuse.
When the warhead of the present invention is detonated, the two sections produce respective fragmentation patterns. Preferably, the two fragmentation patterns overlap and span a polar angle range of at least 150 degrees. Preferably, the overlap is annular. Preferably, the first section produces a conical fragmentation pattern and the second section produces an annular fragmentation pattern.
Fragmentation layers 36A and 36B both include central apertures. Alternatively, the forward-facing fragmentation sheet of the present invention is continuous.
The scope of the present invention also includes a guided missile that includes a warhead of the present invention. The warhead is aft of the guided missile's seeker head, and, of course, the aft section of the warhead is aft of the forward section of the warhead. Preferably, the first section of the warhead spans the missile's fuselage.
The scope of the present invention also includes a method of designing a warhead that is to fit inside a confined space or envelope, such as the fuselage of a guided missile. To outline the forward section, a first radius of curvature sufficient to provide a desired fragment density is selected, a first center of curvature is selected within the fuselage, and a first circular arc centered on the first center of curvature and having as its radius the first radius of curvature is drawn inside the fuselage until the first circular arc intersects the inner wall of the fuselage. A straight line is drawn through that intersection point and through the first center of curvature. To outline the aft section, a second radius of curvature sufficient to provide the desired fragment density is selected, a second center of curvature is selected within the fuselage, preferably on the straight line, and a second circular arc centered on the second center of curvature and having as its radius the second radius of curvature is drawn inside the fuselage. The portion of the first circular arc within the fuselage and the portion of the straight line between the two circular arcs define the forward section. The second circular arc defines the aft section.

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 a schematic axial cross section of the forward part of a guided missile with a prior art warhead;
FIG. 2 is a partial schematic axial cross section of the warhead of FIG. 1;
FIG. 3 shows the angular fragmentation pattern of the warhead of FIG. 1;
FIGS. 4A and 4B are partial schematic axial cross sections of two basic embodiments of a warhead of the present invention;
FIG. 5 is a schematic axial cross section of a preferred embodiment of a warhead of the present invention;
FIG. 6 shows the angular fragmentation pattern of the warhead of FIG. 5,
FIG. 7 shows plots of calculated fragment velocities for the warheads of FIGS. 4A, 4B and 5;
FIG. 8 is a schematic axial cross section of the forward part of a guided missile with a warhead of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a fragmentation warhead which provides sufficient kinetic energy to forward-emerging fragments to inflict damage on a target after traversing components of a missile that are positioned forward of the warhead.
The principles and operation of a fragmentation warhead according to the present invention may be better understood with reference to the drawings and the accompanying description.
Returning now to the drawings, FIG. 5 is a schematic axial cross section of a preferred embodiment 50 of a warhead of the present invention. As in embodiments 30A and 30B, the forward section 52 of embodiment 50 includes a substantially dish-shaped forward-facing fragmentation layer 56 and the aft section 54 of embodiment 50 includes a substantially barrel-shaped aft fragmentation layer 58. Forward-facing fragmentation layer 56 is concave towards aft section 54. Note that to be within the scope of the present invention, the forward-facing fragmentation layer needs to be only substantially dish-shaped: whereas forward-facing fragmentation layer 56 is truly dish-shaped, in the sense of being continuous and without any holes or apertures, forward-facing fragmentation layers 36A and 36B both have central apertures where the base of the dish would be. Fragmentation layers 56 and 58 are cylindrically symmetric and coaxial. Unlike embodiments 30A and 30B, embodiment 50 has a single explosive charge 60 that provides kinetic energy to the fragments of both fragmentation layers 56 and 58. Explosive charge 60 is provided with a cylindrical recess 62 for a detonation fuse.
FIG. 6 shows the angular fragmentation pattern of warhead 50 when warhead 50 is detonated. The fragmentation pattern 64 produced by forward section 52 is a conical pattern that spans an 80 degree solid angle in the forward direction. The fragmentation pattern 66 produced by aft section 54 is identical to the fragmentation pattern of prior art warhead 12. Fragmentation patterns 64 and 66 have an annular overlap region 68 between a polar angle of 30 degrees and a polar angle of 80 degrees. The total polar angle span of the combined fragmentation pattern of warhead 50 as a whole is 150 degrees.
FIG. 7 shows plots of calculated fragment velocities for all three embodiments of the warhead of the present invention. The “+” symbols refer to warhead 30A. The “*” symbols refer to warhead 30B. The circles refer to warhead 50. All three curves have two branches: a first branch that spans a polar angle range from zero degrees to 80 degrees and whose fragments come from the forward-facing fragmentation layer, and a second branch that spans a polar angle range from 30 degrees to 150 degrees and whose fragments come from the aft fragmentation layer. The fragments from all three aft fragmentation layers have similar velocities, as functions of polar angle. The fragments from forward-facing fragmentation layers 36B and 56 also have similar velocities, as functions of polar angles; and for polar angles less than 60 degrees, the velocities of fragments from forward-facing fragmentation layers 36B and 56 are significantly higher than the velocities of fragments from forward-facing fragmentation layer 36A. The use of a common explosive charge 60 for both fragmentation layers of warhead 50 enables warhead 50 to have the same fragment velocity profile as warhead 30B while being significantly shorter and lighter than warhead 30B. In particular, there is synergy between the forward portion of explosive charge 60 in forward section 52 and the aft portion of explosive charge 60 in aft section 54 in accelerating forward-facing fragmentation layer 56.
FIG. 8 is a schematic axial cross section of the forward part of a guided missile 80 of the present invention. Like prior art guided missile 10, guided missile 80 has seeker head 14 in its nose. Aft of seeker head 14 is a warhead 70 of the present invention. Warhead 70 includes a forward section 72 and an aft section 74. Aft of the nose of guided missile 80, the fuselage 82 of guided missile 80 is a cylinder with an axis 84 of cylindrical symmetry. Forward section 72 spans fuselage 82, as shown.
FIG. 8 also illustrates a method of designing a warhead of the present invention. A radius of curvature R₁is selected for forward section 72 that is sufficiently large to provide the desired fragment density. A center of curvature C₁is selected within fuselage 82. A circular arc of radius R₁centered on point C₁is constructed. The intersection of the circular arc of radius R₁with the inner wall of fuselage 82 defines the maximum transverse extent of forward section 72. A straight line L is drawn from that intersection point through point C₁. A radius of curvature R₂is selected for aft section 74 that is sufficiently large to provide the desired fragment density. A center of curvature C₂is selected on line L. A circular arc of radius R₂centered on point C₂is constructed. Note that, in general, points C₁and C₂are not on axis 84. The circular arc of radius R₁and the portion of line L between the two circular arcs define forward section 72. The circular arc of radius R₂defines aft section 74. (More precisely, the surface of revolution obtained by rotating the circular arc of radius R₁and the portion of line L between the two circular arcs about axis 84 defines forward section 72, and the surface of revolution obtained by rotating the circular arc of radius R₂about axis 84 defines aft section 74.)
If the circular arc of radius R₂does not intersect fuselage 82 then the circular arc of radius R₂is continued until the desired fragmentation pattern polar angle range is obtained. If the circular arc of radius R₂intersects fuselage 82 then the process is repeated to design a third section of the warhead.
While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.

Claims

1. A warhead comprising:

(a) a first section including a substantially dish-shaped first fragmentation layer; and

(b) a second section including a substantially barrel-shaped second fragmentation layer.

2. The warhead of claim 1, wherein said first fragmentation layer is concave towards said second section.

3. The warhead of claim 1, wherein said first fragmentation layer is continuous.

4. The warhead of claim 1, wherein said first fragmentation layer includes a central aperture.

5. The warhead of claim 1, further comprising;

(c) a single explosive charge that, when detonated, produces both a first fragmentation pattern corresponding to said first fragmentation layer and a second fragmentation pattern corresponding to said second fragmentation layer.

6. The warhead of claim 5, wherein said explosive charge includes a recess for a fuse.

7. The warhead of claim 5, wherein said fragmentation patterns overlap.

8. The warhead of claim 7, wherein said first fragmentation pattern is conical and wherein said second fragmentation pattern is annular.

9. The warhead of claim 7, wherein said overlap is annular.

10. The warhead of claim 7, wherein said fragmentation patterns span a polar angle range of at least about 150 degrees.

11. The warhead of claim 5, wherein said first fragmentation pattern is conical and wherein said second fragmentation pattern is annular.

12. The warhead of claim 1, wherein, when the warhead is detonated, said sections produce overlapping respective fragmentation patterns.

13. The warhead of claim 12, wherein said fragmentation patterns span a polar angle range of at least about 150 degrees.

14. The warhead of claim 12, wherein said overlap is annular.

15. The warhead of claim 1, wherein, when the warhead is detonated, said first section produces a conical fragmentation pattern and said second section produces an annular fragmentation pattern.

16. A missile comprising the warhead of claim 1.

17. The missile of claim 16, further comprising a fuselage, and wherein said first section substantially spans said fuselage.

18. The missile of claim 16, wherein said second section is aft of said first section.

19. The missile of claim 16, further comprising a seeker head, the warhead being aft of said seeker head.

20. A method of designing a warhead to fit inside a space bounded by an envelope, comprising the steps of:

(a) selecting a first radius of curvature sufficient to provide a desired fragment density;

(b) selecting a first center of curvature within the space;

(c) drawing a first circular arc centered on said first center of curvature and having said first radius of curvature until said first circular arc intersects said envelope;

(d) drawing a straight line from said intersection of said first circular arc with said envelope through said first center of curvature;

(e) selecting a second radius of curvature sufficient to provide said desired fragment density;

(f) selecting a second center of curvature; and

(g) drawing a second circular arc centered on said second center of curvature and having said second radius of curvature, said second circular arc starting from said straight line, said first circular arc and a portion of said straight line between said first and second circular arcs defining a first section of the warhead, said second circular arc defining a second section of the warhead.

21. The method of claim 20, wherein said second center of curvature is on said straight line.