Fluid-Structure Coupled Post-Flight Analysis of the Ascent Phase of SHEFEX II

The Sharp Edge Flight Experiment II (SHEFEX~II) provides a unique dataset for investigating the aerodynamic and structural behavior of sharp-edged vehicles, while this work is focusing on fluid-structure interaction (FSI) simulations to enhance load prediction and structural analysis. Building on previous studies, this study compares rigid body and FSI-based load predictions, analyses torsional and bending responses of the main fins under various atmospheric conditions, and evaluates the influence of wind models affecting pitching oscillations, roll rates and groundtrack. The results reveal that rigid body simulations overestimate fin loads, potentially leading to overly conservative designs. Flight mechanically coupled FSI simulations predict smaller torsion angles and reduced bending of the main fins. Incorporating wind models, the fin dynamics and deformations enlarge. Including both FSI and wind model effects within the fully coupled process chain, yields to resulting flight oscillations that agree well with the measured data gathered during the flown experiment. The coupled model also reproduces the observed rollrate envelope and groundtrack with high accuracy. It is shown, that wind dominates trajectory differences while structural deformation governs roll dynamics. These results confirm that using accurate vehicle geometry, material properties, and environmental reconstruction, a high fidelity coupled FSI flight-mechanics simulation predicts ascent phase behavior within a narrower error band than the in-flight measurement uncertainty. Consequently, the presented methodology enables reliable reduction of safety factor driven mass penalties while preserving structural integrity and flight performance, offering a robust design tool for future sub-, super- and hypersonic spacecraft system design.