Effects of slag ejection on solid rocket motor performance

One-Dimensional, Two-Phase Flow Modeling Toward Interpreting Motor Slag Expulsion Phenomena

“…1): air and water, consistent with Whitesides' subscale testing 4 , and aluminum oxide slag with RSRM propellant combustion gas. In the latter case, the main combustion products are assumed to act as a heavy gas.…”

“…Previous analyses 4,5 have treated the slag flow as a monolithic inert mass partially blocking the nozzle as it flows overboard. These estimate the momentum of the inert mass, but do not account for the momentum reduction of the gas required to accelerate the inert mass, thus violating conservation of momentum.…”

“…A good starting point for estimating this behavior is the subscale air flow tests with water injection that Whitesides 4 directed at Marshall Space Flight Center. Two scaled RSRM contour nozzles were used with water injected in different ways.…”

“…The prevailing model in the literature for quantifying slag mass flowed and thrust effects is the "Slag Ballistics Model (SBM)," presented with the air/water flow study used herein 4 . That model computed an effective throat area required to raise the pressure the amount measured, with the c* unaffected.…”

“…This can be carried further to relate the bulk motor parameters pressure, thrust and mass flow rate under the different exhaust conditions driven by the addition of condensed phase mass flow. An unknown parameter is correlated to airflow testing with water injection 4 . Also, comparison is made to full-scale static test motor data, where thrust and pressure changes are known, and similar behavior is shown.…”