Insensitive munitions

Insensitive munitions are munitions that are designed to withstand stimuli representative of severe but credible accidents. The current range of stimuli are shock, (from bullets, fragments and shaped charge jets), heat (from fires or an adjacent thermal events) and adjacent detonating munitions. A munition can have its vulnerability reduced by a number of means used on their own or in combination such as a reduced vulnerability energetic material, design features, additions or changes to packaging etc. The munition must still retain its terminal effect and performance within acceptable parameters.

Insensitive munitions (IM) will only burn (rather than explode) when subjected to fast or slow heating, bullets, shrapnel, shaped charges or the detonation of another nearby munition. The term refers to warheads, bombs, rocket motors, although different countries' armed forces may have their own definitions.

Due to “accidents, and the subsequent loss of human life, cost of repairing and replacing material, and the toll taken on operational readiness and capability, Insensitive Munitions (IM) improvements are mandated by law in the U.S.”

Three approaches are taken when designing insensitive munitions: Firstly, the high energy device can be protected and transported with an external protection of some kind. Some munition shipping containers are designed to provide some protection and thermal insulation. Secondly, the chemistry of the high energy fill is chosen to provide a higher degree of stability, for example by using plastic bonded explosives. Lastly, the casings of high energy devices can be designed in such a way as to allow venting or some other form of pressure relief in a fire.

Beyond the three approaches above, other threats need addressing when designing IM, e.g., slow and fast cook-off, sympathetic detonation, bullet and fragment impact, and shaped charge jet impact. Extensive testing requirements for potential IM candidates to address these threats are extremely costly. Modeling programs are being designed to simulate the threat of bullet and fragment impact in an effort to reduce testing costs. One of the most promising methods that engineers and scientists within the U.S. Department of Defense (DoD) are employing to help to enhance IM performance is by using advanced multiphysics modeling programs. Also, another effort is underway developing 2-D numerical code that will simulate the threat of slow and fast cook-off.

...
Wikipedia