L-248 Variability of Munition Response to Operational and Peace Time Threats

July 2020
M.M. van der Voort (MSIAC), W.D. Smith (NOSSA), Dr. E.L. Baker (MSIAC), C. Collet (MSIAC), F. Djédis (ENSTA Bretagne), K. Tomasello (NOSSA)
An Insensitive Munition (IM) signature is determined by the munition response to various operational and peace time threats. The responses are obtained through standardized IM tests for slow and fast heating (SH and FH), bullet and fragment impact (BI and FI), as well as shaped charge jet attack (SCJ) and sympathetic reaction (SR).
the 2018 MSIAC Improved Explosives and Munitions Risk Management (IEMRM) workshop it was concluded that the blast and fragmentation measurements conducted in the IM tests can also be used to inform safety distances, as well as consequence and risk analysis. However, to date, IM test data has not been consistently used for this purpose. An important issue is the variability in the observed munition response. This may not always be clear as typically only one or very few tests are carried out. In this report we discuss various aspects and examples of variability in munitions testing.
Firstly, we consider a bonfire stack test of many hundreds of non-mass detonating (HD1.2) rounds, resulting in large variations in observed munition response and TNT equivalence. This type of test does not provide insight into the cause of the variability, which can be either through differences in received thermal loads or by stochastic variability. Secondly, we discuss variations of the response observed in multiple “identical” repetitions of the bullet impact test conducted by DOSG in the UK. In this case the variations are of a stochastic nature, although some variations may exist in terms of aim point and tilt. Thirdly, we consider the assigned munition response in a large number of IM tests conducted by the US Navy and the French DGA. Based on blast measurements, a correlation was established between the assigned response type and TNT equivalence for any desired confidence level.
This report also presents the MSIAC IM TNT tool for determination of TNT equivalence based on blast measurements. The tool is available for MSIAC members upon request.

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Jakob Breiner
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Christelle Collet
Propulsion Technology TSO
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Munitions Transport and Storage Safety TSO
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