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Parametric Study of the Aftbody Design of an Airbreathing Hypersonic Accelerator

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The results of a parametric, numerical study of aftbody exhaust flows on a conical, airbreathing, hypersonic vehicle are presented. Three-dimensional Euler simulations were performed at Mach 9 and steered to a pitch-trimmed lift-equals-weight condition. Quasi-1-D cycle analysis was employed to model the scramjet propulsion and viscous forces were accounted for using a separate boundary-layer code. The simulation method is presented and credibility demonstrated before parameters controlling the aftbody design and their effect on vehicle performance are reviewed. The parameter sweep resulted in a wide range of predicted performance (thrust-to-drag ratios of 1.17 to 1.79) with 3-D flow features, interaction between engine modules, and trim penalties identified as strong drivers. The large variation in the thrust-to-drag ratio observed in the results of this study highlights the criticality of the aftbody design of an accelerator.