Warhead fragmentation effectiveness is determined by the number, mass, shape, and velocity of the fragments. By using a controlled fragmentation design, warhead fragmentation can generally be achieved quickly and cost effectively. Exemplary controlled fragmentation techniques are described in U.S. Pat. Nos. 3,491,694; 4,312,274; 4,745,864; 5,131,329; and 5,337,673.
In general, conventional designs use “cutter” liners that form fragments by generating a complex pattern of high-velocity “penetrators” for fragmenting the shell. Although these conventional fragmentation designs have proven to be useful, it would be desirable to present additional functional, cost and safety improvements that minimize the warhead weight, reduce manufacture expenses, and advance current United States Insensitive Munition (IM) requirements.
What is therefore needed is a controlled fragmentation technique through the use of patterned liners which introduce shear stress into the warhead body and creates the desired fragmentation patterns. Fragment size, fragment numbers, and patterns thereof may be influenced through novel liner configurations. The need for such a controlled fragmentation technique has heretofore remained unsatisfied.
The present invention satisfies these needs, and presents a munition or warhead such as a projectile, and an associated method for generating controlled fragmentation patterns. According to the present invention, warhead fragmentation is achieved more efficiently and more cost effectively than conventional techniques, through the use of a relatively inexpensively formed plastic liner with a predetermined pattern of recessed areas and a plastic liner with a predetermined pattern of raised areas, sized to fit within the recessed areas, and capable of being moved about relatively and locked that way before detonation, to create varying levels of overall liner thickness in select regions, that is experienced during a detonation. The more thin regions will more likely lead to larger fragments ultimately, than will the more thick regions, as will be appreciated from the discussion here after. The liners could also be made of steel, tungsten, tantalum, or other materials.
According to one embodiment of the present invention, the warhead includes two movable liners that are disposed inside the warhead body which include predetermined patterns that are created with areas of different overall thicknesses presented to the exploding core, such allowing the detonation shock wave to correspondingly propagate into the fragmenting case through various effective thicknesses of liner material. The liner recessed and raised areas, and combinations thereof by physical positioning can, by varying thicknesses in regions, create contours of localized transitional regions with high-gradients of pressures, velocities, strains, and strain-rates acting as stress and strain concentration factors. Unstable thermoplastic shear (adiabatic shear) eventually transfers the entire burden of localized strain, to a finite number of shear planes leading to ultimately to an outer shell break-up and formation of fragments.
As a result, the explosion produces a complex pattern of shear planes in the warhead body, causing the case break-up and formation of fragments with various, predetermined sizes. This design is distinguishable from existing fragmentation liner technologies that attempt to score or cut the warhead body.
One of the advantages of the present embodiment compared to existing technologies is the cost effectiveness of the manufacturing process of the present design, in that it is faster and more economical to fabricate and to pattern plastic liners as opposed to notching or cutting a steel warhead body itself. Another advantage of the present invention is that the use of plastic material reduces the overall weight of the warhead compared with use of other materials. Fortuitously, the use of plastic is also a great safety feature. An unwanted ignition of the explosive due to the heat of launch would normally be catastrophic as well as fratricidal, but here the plastic liners in this invention are mounted to cover the explosive inside the casing body. In the event of unwanted heat/ignition, the plastic (which is also low melt temperature material), would melt to seal the explosive which adds to safety. Moreover the (melted) plastic would also flow and could push out overflows that are usually provided in these rounds. Because of the plastic, neither sudden pressure nor heat/ignition inside the round would therefore be as catastrophic. Therefore, choice of low-melt temperature plastic as liner materials in this invention, adds safety to the round. This benefit is favorable, consistent with current Insensitive Munition (IM) requirements in minimizing accidental ammunition explosion due to fire hazards.
It is an object of the present invention to provide means for generating fragments upon detonation of a warhead, with a relatively less expensive to manufacture structure of plastic liner components, and;
It is a further object of the present invention to provide a fragmentation warhead which generates fragments upon detonation wherein the size and shape of such fragments may be selected through liner design, and;
It is a still further object of the present invention to provide a fragmentation warhead which generates fragments upon detonation wherein the size and shape of such fragments may be selected prior to detonation by manually dialing in a change to positioning of liner components within said warhead, and;
It is a yet another object of the present invention to provide a fragmentation warhead of increased safety and sensitivity against unwanted fratricide of other warheads by reason of melting properties of the plastic materials within the warhead providing protection there against.
These and other objects, features and advantages of the invention will become more apparent in view of the within detailed descriptions of the invention and in light of the following drawings, in which:
The time delay between the moments when the shock waves arrive is determined by the differences between the detonation velocity of the explosive 104 and the shock wave propagation speed of liner material, in various thicknesses of the liner material, respectively. It can be appreciated that this generates a high gradient of pressures, velocities, and strains between parts of the liners, acting as stress and strain “concentration factors”. Unstable thermoplastic shear (adiabatic shear) eventually transfers the entire burden of localized strain to a finite number of shear planes leading to the warhead body 102 break-up and formation of fragments. As a result, a predetermined pattern of liner recessed areas or tabs can “stamp out” a pattern of localized transitional regions so as to cause the warhead body 102 to shear and break into fragments, accordingly, with controlled sizes. The thinnest liner material presented to the explosion would be a recessed area 202 alone. As an example, twice as much material in thickness would be seen in an explosion, where a tab 302 fills part of that recessed area.
The thickness of a liner in various locations and type of explosive help determine the fragment results. A selectively controlled pattern of recessed areas can comprise sections of equal size or, alternatively, sections ranging in size from a relatively large size to smaller sections. The larger size of such sections is selected for more heavily armored targets, while the smaller size of such sections is applicable for lightly armored or soft targets. Consequently, the pattern efficiently enables variable and selective lethality of the warhead 100 that can range from maximum lethality for more heavily armored targets to a maximum lethality for lightly armored or soft targets.
Mechanical adjustments to the grids could be translational (in or out) or rotational (but rotational only if the tab 302 widths were made less than the recessed area 202 widths). As will be further described, all these movements will have an ultimate influence on sizes for the fragments to be formed on the exploding fragmenting warhead housing 102.
While the invention has been described with reference to certain embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.
This application is a Continuation-in-Part of U.S. patent application Ser. No. 12/709,534 filed on Feb. 22, 2010 now U.S. Pat. No. 8,272,330 by the like inventors, and is commonly assigned.
The inventions described herein may be made, used, or licensed by or for the U.S. Government for U.S. Government purposes.
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Number | Date | Country | |
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Parent | 12709534 | Feb 2010 | US |
Child | 13215510 | US |