Sensitivity Analysis for the Dynamic Aeroelasticity of a Launch Vehicle

A linearized aeroelastic analysis for a launch vehicle in the neighborhood of its transonic flight phase together with a local sensitivity study are presented. This investigation includes only dynamic aeroelastic instabilities, namely, flutter instabilities. Indeed, the launch vehicle considered for the applications is assumed to be initially free from other static instabilities like aeroelastic divergence, buckling, or from follower propulsive-force destabilizing effects, the study of which has not been included in the present paper. A modal description for the structural dynamics of the launcher in terms of the first nonzero natural frequencies and modes of vibration is carried out. Moreover, a reduced-order model for the unsteady transonic aerodynamics is obtained, performing several prescribed modal transient boundary conditions by laminar-based computational fluid dynamics. Thus, a modal input/output system identification for the aerodynamics, performed in the frequency domain, allows one to identify the linearized unsteady aerodynamic operator in the neighborhood of the specific transonic flight condition. Both the structural and aerodynamic models are finally employed in the aeroelastic coupled model given by the generalized Lagrangian equations of motion. An eigenanalysis, in terms of aeroelastic-system poles and complex eigenvectors on the linearized model, is performed to check the local dynamic stability of the launch vehicle. Finally, the proposed approach also allows one to give an evaluation of the uncertainty in the obtained stability scenario in terms of perturbing flight parameters like angle of attack, Much number, flight speed, and air density.