L-157 IM State-of-the-Art on Mortar Shells

In-service mortar shells are usually filled with Composition B.  These mortars, however, exhibit a poor IM signature as shown in table 1.  Their response ranges from type I to type III reaction to fast cook-off, slow cook-off and is systematically type I reaction to shaped charge jet aggression and sympathetic reaction in a palletized configuration.  The reaction level to bullet impact is generally lower compared to the other threats but the response is explosion or worse for most shells listed in table 1.

Table 1: Response of Mortar Shells Filled with Composition B to IM Threats

Many studies have been carried out to improve the IM signature of mortar shells.  A large number of these studies are focused on the development of new formulations with melt-castable explosives in order to maintain the existing filling facilities.  Cast-cured compositions have also been evaluated and are already available for large scale industrial production.

This document presents a state-of-the-art of IM achievements for mortar shells.  It is focused on in-service/advanced development shells with significant IM improvements as well as R&D studies.  The first section of this document details the available IM signature of the different mortar shells.  Available information on explosive compositions and venting devices used to improve IM signature are then presented.