Flight Simulation and Drag Prediction for a Pitching-Accelerating Hypersonic Reentry Vehicle

Abstract

A nonwinged reentry vehicle, such as the upper stage of a ballistic missile, endures harsh aerodynamic loads during the phase of reentry. This phase is characterized by sophisticated flight phenomena including hypersonic speed, continuous variation of surrounding atmospheric conditions, and pitching transient vehicle motion. During the flight in this descent phase, drag is considered the dominant aerodynamic force where accurate prediction is crucial as far as reliable trajectory prediction and mission planning are concerned. This study aims to investigate drag on a generic bi-cone nonwinged reentry vehicle resembling an upper stage of a ballistic missile during descent. This is done by using both trajectory prediction and numerical simulation of vehicle–air interaction. To obtain the vehicle dynamics and instantaneous flight conditions through descending phase, a three-degree-of-freedom pitch flight trajectory model is utilized starting from point of separation. It was concluded that the vehicle experiences small-amplitude pitching motion while descending from about 90 to 30 km and accelerating in a hypersonic regime (Mach 5.7–7). Drag is then calculated via time-dependent numerical simulations. The results show the flowfield pattern evolution in addition to the temporal variation of drag on the vehicle during the flight phase in concern.