Exhaust Gas and Plume Modeling Effects for Space Launch System Abort Scenarios

Abstract

Viscous computational fluid dynamics simulations depicting Space Launch System post Mode-1 abort scenarios are conducted and analyzed. The purpose of these simulations is to study the effect of attitude control motor and abort motor plume modeling on the drag of the aborted core stage. The simulations are first conducted with a multispecies and chemically reacting thermodynamic model. Following this, equivalent species are created for the exhaust gases. These equivalent species aim to provide results for core stage drag similar to the chemically reacting model at a lower computational cost. Finally, the exhaust gases are modeled as calorically perfect air. Under most scenarios, both simplified models predict the drag on the core stage close to that predicted by the chemically reacting simulations. In these cases, the flow conditions do not induce significant changes in the composition of the exhaust gas via afterburning. For simulations in which this is not the case, the properties of the simplified models deviate from the true mixture, yielding unsatisfactory results. Finally, the chemically reacting model is weighed against the associated increase in computational costs. The simplified models are at least four times less computationally expensive than the reacting model.