L-224 Reaction Mechanisms For Rocket Motors to Mechanical Threats

February 2019

Solid Rocket Motors (SRMs) have been used for decades to propel tactical and ballistic missiles as well as space launchers. The high impulse delivered by today’s solid propellants and their availability mean that they continue to be widely used by the military. However, the current design (presence of a central bore in most cases) and the use of HD 1.1 propellant materials has led to some solid rocket motors becoming more likely to detonate under the extreme but credible operational threats described in AOP-39. This is especially true for mechanical threats such as fragment/bullet impacts, shaped charge jet attacks and sympathetic reaction, which represent a major challenge for current and future solid rocket motor designs.

The aim of this report is to provide an overview of past and on-going studies that have contributed to better understand the specific reaction mechanisms likely to occur within a solid rocket motor under mechanical and intense shock stimuli. 

The first two parts deal with definitions related to rocket motors and solid propellants.  The report then considers different decomposition regimes appropriate to rocket motors. These are discussed as well as the transition pathways from one regime to another. The last part of this document considers the key factors influencing the IM signature and existing ways to mitigate the rocket motor response to mechanical threats.

Key words: solid rocket motor, solid propellant, mechanical threats, bullet impact, fragment impact, shaped charge jet, explosively formed penetrator, reaction mechanism, decomposition regime, combustion, deflagration, detonation, DDT, SDT, BVR, XDT, mitigation technologies


Yves Guengant (ArianeGroup SME Environnement), Benjamin Keefe (UK DOSG)

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Christelle Collet
Propulsion Technology TSO
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