Air Force

Improved reactive liner for warheads

Liner design creates smaller and faster-moving fragments upon detonation of the warhead

Military Technology

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A cross-sectional view of the warhead: steel case 1, the reactive liner 2, and the explosive 3. The reactive liner is sculpted along its interior surface with semi-cylindrical open linear cells that form voids 4 in the reactive liner, which is the crux of the design. The contact points 5 are at the explosive-reactive liner interface.

While reactive liners enhance the blast of high brisance explosives, the first problem is that they are inefficient. The chemical constituents mix behind the shocked air, which is known to have a low concentration of available oxygen. Therefore, the only mechanism with which the reactive liner can enhance blast is through shear-induced mixing typically encountered by a reflecting surface.

The second problem with reactive liners is that they reduce the specific kinetic energy to the case wall due to impedance mismatch and additional mass. This subsequently increases the specific impulse and causes large and slower moving fragments.

Air Force scientists and engineers have developed a design which enhances the blast of a lined warhead by mixing the reactive liner earlier in time than an annularly lined warhead upon detonation. This is accomplished by notching the reactive liner along its interior surface with semi-cylindrical linear open cells that form voids in the reactive liner. The voids are concave toward the explosive.

The design increases the ejection velocity of the fragments via impendence matching, shocked fluid instability and multi-phase reactive flow. The semi-circular voids create enough stress diffusion to allow the case to expand to 95% of its natural limit and yet, create enough stress concentrations to govern case fragmentation. The fragments are not as well formed as those created by other plastic liners, such as wedges, but they are faster moving, and more abundant due to the fact that gases inside the case remain under pressure for a longer duration of time.

The geometry maximizes the reactive liner mixing and prevents the case from prematurely failing. As the turbulent mixing generated by the semi-cylindrical voids is unstable, it defocuses the stresses as the case wall expands. The defocused stresses prevent premature case rupture, as in Pearson notches, allowing the case to expand to nearly its full extent before fracturing. As a result of the nearly full expansion, the fragments achieve higher ejection velocity than a typically lined generic warhead. And as result of the turbulent mixing, the blast peak pressure and maximum impulse are higher than typically lined generic warheads, as well.

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