High-lethality low collateral damage fragmentation warhead

Abstract

The present invention provides a high-lethality low collateral damage fragmentation warhead. The case is formed of a material that is pulverized upon detonation of the explosive. As a result, the lethality radius of the pulverized case fragments is no greater than that of the gas blast, thus reducing potential collateral damage. Warhead lethality is improved by placing a pattern shaper between the fragment assembly and the explosive. The explosive and pattern shaper have a conformal non-planar interface that shapes the pressure wavefront as it propagates there through to expel metal fragments from the fragmentation assembly with a desired pattern density over a prescribed solid angle.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to fragmentation warheads.[0003]2. Description of the Related Art[0004]Fragmentation warheads expel metal fragments upon detonation of an explosive. Fragmentation warheads are used as offensive weapons or as countermeasures to anti-personnel or anti-property weapons such as rocket-propelled grenades. A typical warhead includes an explosive inside a steel case. A booster explosive and safe and arm device are positioned in an aft section of the case to detonate the explosive. A fragmentation assembly is placed in an opening in a fore section of the case against the flat leading surface of the explosive. The fragmentation assembly will typically include ‘scored’ metal or individual fragments such as spheres or cubes to control the size and shape of the fragments so that the fragments are expelled in a predictable pattern and speed. Scored metal produces about an 80% mass efficiency while individual f...

AI Technical Summary

Benefits of technology

[0008]This is accomplished by forming the case of a material that is pulverized upon detonation of the explosive. The lethality radius of the pulverized case fragments is no greater than that of the gas blast, thus reducing potential collateral damage. Warhead lethality is improved by placing a pattern shaper between the fragment assembly and the explosive. The explosive and pattern shaper have a conformal non-planar interface that shapes the front of the pressure wave as it propagates there through to expel metal fragments from the fragmentation assembly with a desired pattern density over a prescribed solid angle. In an exemplary embodiment, the pattern shaper provides a more uniform density over only the prescribed solid angle. This improves lethality and further reduces collateral damage. The expelled metal fragments exhibit a mass efficiency of at least 70% with typical values of approximately 80% for scored metal and near 100% for discrete fragments such as cubes or spheres. By comparison the pulverized case fragments exhibit a mass efficiency of no more than 1% with preferred values near 0%. A metal retaining ring around the periphery of and at least coextensive with the fragmentation assembly provides a measure of confinement that directs fragments at the edges in the desired direction to reduce any tails outside the prescribed solid angle. The warhead may be configured as forward or side-firing. Although the preferred embodiment includes both the case material that is pulverized upon detonation and the pattern shaper, the fragmentation warhead may be improved by employing either feature alone to reduce collateral damage or improve lethality.

[0009]In an exemplary embodiment of a forward firing warhead, the case is made of a material that is pulverized with a mass efficiency near 0% upon detonation. Detonation is initiated with a single-point booster positioned aft along the body axis aft of the explosive. The fore end of the explosive and the pattern shaper are designed to progressively slow the advancing pressure wave with increasing radius from the body axis to make the number of expelled fragments per unit area more uniform across a prescribed solid angle. This is achieved by providing the explosive with a convex conical shape about the body axis having radius R1 and slope S1. The explosive and pattern shaper are also designed (suitably in conjunction with the retaining ring) to gradually speed the advancing pressure wavefront at the periphery to direct expelled fragments along the body axis to reduce the tails outside the prescribed solid angle. This is achieved by providing the explosive with a convex annular shape from radius R2 to the other edge with slope S2. The two shaped regions are typically separated by a planar annular region of R2−R1. The interior surface of the pattern shaper conforms to the shape of the explosive. The exterior surface is typically planar and abuts the fragment assembly. The thickness of the pattern shaper is dictated by the shock impedance of the material from which it is formed. The pattern shaper can be an integral part of the fragmentation assembly. However, discrete parts simplify machining and allows for more flexibility in the selection of the pattern shaper material.

Problems solved by technology

In other words, the mass efficiency is the ratio of the total mass less the interstitial mass that was consumed during the launch process (therefore ineffective against the intended target) to the total mass.

As a result, the warhead has a maximum lethality confined to a very narrow angle and expels a certain amount of lethal fragments outside the desired target area that may cause collateral damage.

As a result, the aimpoint and detonation timing tolerances to engage and destroy the threat while minimizing collateral damage are tight.

Detonation of the steel case increases the potential for collateral damage without improving the lethality of the warhead to destroy the threat.

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