Mitigation of solid booster ignition over pressure by water aerosol sprays

Interaction of acoustic waves with water aerosol layers is analyzed in the context of the problem of solid booster ignition overpressure suppression. In contrast to the conventional approach to ignition overpressure suppression, which aims at using water to quench the sourcesof the ignition overpressure waves, this study focuses on blocking the ignition overpressure wave propagation, using reflection and attenuationofthe wave by the water aerosol layers. The study considers interactionof the waves with aerosol layers of large mass loading for varying sizesofthe droplets. The size of the droplets is shown to substantially affect the mechanisms of interaction with the waves. The criteria for the crossover between different mechanisms are established as functions of the droplet size and the ignition overpressure wave parameters. The optimal parameters and designs for water aerosol sprays are proposed that maximize the ignition overpressure suppression. These results were obtained using the nozzle and the exhaust hole geometries similartothoseofthe space shuttle. Remarkably, itis found that variousa priori reasonable designsof the aerosol and water sprays may increase the ignition overpressure impact on the vehicle, increasing the risk of vehicle damage.