Nonlinear Combustion Stability Prediction of Solid Rocket Motors

"Software & Engineering Associates, Inc., proposes to develop a new tool to analyze solid rocket motor combustion stability which will predict for an unstable motor the combustion chamber's maximum over-pressurization. When a rocket motor experiencescombustion instability, it often does not experience a catastrophic failure, but a temporary amplitude limited pressure fluctuation. If the magnitude of the fluctuation can be predicted, one can then determine if it is sufficiently low as to be ignored,or if it will damage the payload or cause unacceptable flight variations. The current stability analysis code examines each of the combustion chamber's acoustic modes separately. As such, it cannot model the transfer of energy between unstable and stableacoustic modes, transfers which can act to dampen the unstable mode, resulting in an amplitude limited pressure fluctuation (limit cycle). A new non-linear analysis technique developed at Cal Tech compares a given unstable acoustic mode with the othermodes in the system, and from that predicts the maximum amplitude of the over-pressurization. The focus of this Phase I SBIR will be to identify the algorithms and inputs required to implement a non-linear stability analysis into the current solid rocketmotor combustion stability code. This research will result in an innovative design tool to predict combustion instability amplitudes of an unstable solid rocket motor during the design phase