UNCLASSIFIED
Distribution Statement A: Approved for public release. Distribution unlimited.
UNCLASSIFIED
2018 International Explosives Safety Symposium & Exposition
San Diego, CA
August 6-9, 2018
Ballistic Trajectory Modeling for the Insensitive Munitions Type IV/V Hazardous
Fragment Threshold
Kevin T. Miers*, Daniel J. Pudlak, Brian E. Fuchs
US Army RDECOM-ARDEC, RDAR-MEE-W, Picatinny, NJ 07806
*Kevin Miers, (973) 724-1180, kevin.t.miers.civ@mail.mil
(U) Currently, the 20J fragment projection curve in TB-700-2 [1] (which also
appears in AOP-39 [2]) is being used by the Insensitive Munitions (IM) community to
distinguish between Type IV (deflagration) and Type V (burn) responses, in conjunction
with other experimental evidence. Each fragment is collected after an IM test, and its
distance from the origin is compared to a critical throw distance which depends on its mass,
defined by the 20J curve. If this distance is exceeded for any of the fragments, the reaction
is deemed a Type IV. Substantial resources are being expended to obtain Type V reactions
for various munition systems, and thus it is important for this criterion to be meaningful
and sufficiently accurate, while also being practical and inexpensive to use.
(U) The current 20J curve is relatively restrictive in the sense that it is too mass-
dependent, and thus causes Type IV designations due to large, slow-moving fragments
which do not appear to be dangerous. For this reason, various efforts have recently been
undertaken by the community to come up with an improved and more meaningful criterion
for what a Type V should indicate. Some matters of contention included the intent of the
curve (severity and mechanism of injury), the appropriate hazard metric (energy, energy
per unit area, etc.), the conditions at which the metric applies (launch, impact, impact at
some distance), if and how the criterion should vary for different shapes and materials, how
many fragments must fail the criterion before a Type IV is declared, and the meaning of a
15m distance requirement which appears frequently in the documents [1, 2]. These
ambiguities led to some exploratory trajectory modeling being performed to try to
reproduce the curve, as there was no documentation available which adequately explained
its origin. A point mass ballistic trajectory code similar to TRAJ [5] and a univariate
optimization tool were written and validated for this purpose. It was found that the curve
in [1, 2] represents the maximum distance a chunky steel warhead fragment [4] could travel
with a 20J launch energy. While a 20J impact energy curve would be desirable, the
hazardous distances associated with non-negligibly small masses become unbounded.
(U) The community decided to keep 20J as the hazard metric, but changed it to a
20J impact at 15m criterion, with a different curve for each of several fragment densities.
This curve guarantees that if the criterion is violated, a person standing at 15m would be
hit with a 20J impact if the trajectory were lowered. The authors have constructed the mass-
distance curves being incorporated into the new version of AOP-39. This paper documents
the methodology and assumptions involved in generation of the new curves. It is hoped
that this work will help elucidate the details and limitations of the criterion as well as areas
in which potential improvements can be made, since the criterion is currently of significant
consequence to the success or failure of various IM programs.
