Aeroelastic behavior of launcher thermal insulation panel, accounting for various aerodynamic and structural models

Versatile Thermal Insulation panels, have been introduced for the first time with U.S. space launchers during the ’60, and immediately represented an element of high complexity, due the wide range of design parameters and the difficult operating conditions. Cases of flutter affecting VTI panels, have been observed since the first applications, stimulating the development of theories able to predict the phenomenon with sufficient accuracy. Numerical study of the panel flutter, has led to the development of different structural and aerodynamic models, useful for investigate this aeroelastic stability. The quasi-steady Piston Theory formulation may be applied only above M = 1.5, reducing the study capability to the supersonic range. This work proposes an un-steady formulation of the Piston Theory, derived by Vedeneev, aiming to extend its range of validity also for 1.3 < M < 1.5. Various comparison between these aerodynamic theories, have been carried out in order to underline the main differences in the previous range of Mach and in the accuracy with which the critical conditions are detected. Hand in hand, have been tested different structural models, of increasing complexity, based on 1D and 2D formulation, and also panels with a more advanced structure, multi-layer and sandwich and for last, a typical VTI configuration consists of a semi-circle sandwich panel. Using Shell models such as Equivalent Single Layer or Layer Wise, you may observe relevant variations in final results, highlighting the necessity of more complex structural models in Multi-Layered panels.