Flight Stability Analysis and Flap Size Optimization along a Trajectory of a Waverider Concept

Abstract

The High Lift Reentry Vehicle (HLRV) and its reference trajectory introduced in earlier studies will serve as the baseline for the work in this paper. The generic waverider is utilized for code-to-code validation and comparison due to its simple geometry features and short solution times. First, results of an implemented low-fidelity Second Order Shock Expansion as well as Modified-Newton codes gets compared to simulated data of the high-fidelity DLR TAU code. Especially in combination on specific geometric features, e.g. computation of blunt leading edges using the Modified-Newton mehtod and SOSE otherwise, the results show great agreement in the quantitative as well as excellent agreement in the overall trend of the analyzed body fixed forces and pitching moments along the trajectory. The validated panel codes are then employed to map the HLRVs static pitching-stability envelope over the entire trajectory, revealing that a waverider with a center of gravity of 60 % of its length remains stable in its trimmed configuration, whereas the uniformly mass-distributed vehicle becomes unstable without flap deployment. Free-flight simulations in the trimmed state demonstrate that the baseline HLRV can be trimmed with flap deflections under 4° at trim angles between 2° to =3°. Leveraging the DLR SMARTy optimization toolbox, surrogate models are generated along the trajectory to optimize the upper and lower flap sizes while preserving pitch stability. Two separate optimizations are performed: (I) minimizing drag and (II) maximizing lift-over-drag ratio, establishing the performance bounds of the reference HLRV. Several optimal geometries have been identified on the resulting Pareto front, depending on the objective functions. The integrated multi-point optimization chain accelerates aerodynamic and aerothermal load predictions, enabling low-fidelity tools to be used for targeted analyses such as pitch-stability assessment. This facilitates broader optimization strategies, improves thermal-protection-system design, and supports the development of more efficient hypersonic reentry vehicles.