KEW Fragmentation Warhead
Some anti-missile systems, such as the Patriot missile system used in the Gulf War, use blast-fragmentation. In a blast-fragmentation system, high power explosives detonate shortly before the collision of the interceptor and threat. This causes the airborne threat to be destroyed by an explosion and subsequent debris field of shrapnel in its immediate flight path. The explosion also causes a destructive shock wave that mechanically and electrically destroys the airborne threat, and/or renders its electronic systems useless. These blast fragmentation systems are popular for lower-tier defensive applications.
In the past, a number of fragment type warheads have been proposed, but these have suffered from numerous disadvantages, including the fact that a comparatively high explosive-charge-to-metal parts ratio was required in order to achieve the desired fragment projection velocity. Many if not most prior art configurations typically involved a single explosive burster charge surrounded by fragments, but because of low coupling efficiencies, a considerable amount of explosive was required if desirably high fragment velocities were to be achieved with a limited number of fragments.
Fragmentation structures, such as fragmentation warheads, mines, etc., are employed by the military against a wide variety of targets where dispersion of fragments over a target area is required. A problem which arises in their use is that fragmentation warheads suitable for use against personnel are generally not suitable for use against "hard" targets such as armored vehicles and emplacements, where fragments of relatively greater size and mass are required. Military units have therefore been required to maintain supplies of several types of fragmentation warheads, each type adapted for use against a particular type of target. This results in an increased burden of logistics and supply and is, of course, highly undesirable. In the past, it has been attempted to minimize this problem by constructing warheads having two sections, one section being adapted to disperse fragments of one size and the other being adapted to disperse fragments of another size. In this manner, a single warhead may be utilized against a variety of targets. Such a construction, however, is inefficient in that, in each case, portions of the warhead not designed for the particular application are largely ineffective; furthermore, in order to produce a given amount of destructive force, a warhead of larger dimensions is necessary than would be the case for one designed for the specific application.
Other problems related to the construction of fragmentation warheads have involved the expense of machining or casting a multiplicity of grooves or openings in the metal casings to induce fragmentation of the casing in a desired pattern by establishing preferential fracture lines. Alternatively, an inner casing having openings or grooves formed therethrough is disposed within an outer metal casing and configured such that it directs explosive shock waves from an internal explosive charge against the outer casing in a grid-like pattern, such that the outer casing is fractured along the grid lines. In all cases, the molding, machining, or forging of metal structures into a desired, grid-like pattern is undesirably expensive, particularly when large quantities of weapons are to be manufactured. A further, related problem present with any explosive device is the danger of accidental detonation of the explosive charge by either mechanical shock or heat. Under combat conditions, for example, stored ammunition may be jarred by incoming rounds or careless handling, or it may be heated by fires started by incoming rounds. In any case, it is desirable that the ammunition be as resistant as possible to such heat and shock.
To avoid random distribution of fragments propelled by exploding anti-property and personnel devices, it is necessary to control the size, shape, and weight of the fragments. Small fragments have low mass and will not possess optimum amount of kinetic energy against a desired target compared to a larger mass fragment traveling at the same velocity. Large fragments, and in particular, bar, plate, and diamond shapes, however, offer more atmospheric drag causing the fragment velocity to slow down rapidly, resulting in a reduced kinetic energy on the target. It can be appreciated that inconsistant fragment size, shape and weight are undesirable.
Heretofore, fragmentation control has included providing grooves on either the external or internal surfaces of the wall of the case or a liner inserted into the case. The grooves create stress concentrations that cause the case to fracture along the grooves forming fragments. Generally these grooves are longitudinal, circumferential, or both, or constitute a series of intersecting helical grooves designed to produce diamond shape fragments.
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