Developing Solid Rocket Motor Insensitive Munitions Solutions for Impact Threats

The Phase II objective is to demonstrate technology that will provide IM solutions to bullet and fragment impact threats in large diameter solid rocket motors. We have taken a comprehensive approach in which a number of IM mitigation techniques are combined into a design that reduces the violence of the response to BI and FI. These techniques, which were assessed and evaluated in Phase I, are integrated into the analog motor for the Phase II demonstration. The principal elements in this approach are: Ignition delay liner(IDL), Tough Propellant, and Bore Mitigant. Each element contributes to reducing the overall pressurization rate generated by the projectile impact. For instance, the IDL delays ignition of the grain burning surface, the tough propellant minimizes the fragmentation and debris thereby reducing burning surface, and the bore mitigant retards exposure of the grain surface to combustion gases and reduces the pressurization rate. Our design also incorporates a graphite composite case which is known to reduce the violence of rocket motor response to IM stimuli. The evaluation of HTPB and HTPE in the analog motors will provide a comparison of the IM performance in a common configuration. We will also measure detailed internal pressure, stress - time response to the impact events at critical locations in the analog motor. This will provide an understanding of the ignition process and the pressure rise rates that lead to the violent responses typically observed.