Integrated Fragment Insult Studies

50-cal powder gun firing into a target assembly.

Weapons Response

The response of weapon systems to generalized fragment insult is one of the critically important issues to understand and manage throughout handling and deployment processes. Both the Department of Energy (DOE) and the Department of Defense (DoD) have implemented continuously evolving sets of guidelines to manage these processes. Over ≈15 years we have lead and/or participated in team efforts in this arena by creating and executing key experimental components to integrated projects from which fundamental understandings, numerical simulation, and ultimately operations guidance can be based.

Underlying Issues

High explosives product gases blowing over 1"x1"x1/2" and 1"x1"x1/4" Cu fragments

For many decades two limiting behaviors in the system of equations prescribing mass, momentum and energy continuity have been successfully utilized; the small amplitude limit, from which linear acoustics derives, and the strong shock limit, where dynamic stresses are much greater than yield strengths. In both cases simplifications occur in the governing differential system that facilitate solutions. Even with these simplifications accurate calculations of relevant solution spaces can be exceedingly difficult, and even fail, though there are many notable successes too.

Problems of generalized fragment insult on systems containing heterogeneous energetic material(s), however, generally do not permit such simplifications, but rather the entire range of amplitudes must be considered over characteristic scales that might vary by six to eight orders of magnitude; that is, fast transport processes can initiate dynamics whereby space and time exists for relatively slow processes to evolve, which, in turn, can lead to fast processes at much later relative times. For example, a slow dynamical response initiated by an early fragment can occur such that changes in the fifth or six decimal place over the EOS surface might lead to a catastrophic response from (slow) fragments ½ a millisecond later.

Transposition experiment

To make matters even more interesting, stochastic behavior generally is important, both within the definition of a continuum element, and for transporting mass, momentum and energy between continuum elements. Furthermore, much care must be taken to maintain hyperbolic transport.
Integrated Fragment Insult Studies (pdf)