Linearized Aeroelastic Gust Response Analysis of a Launch Vehicle

A methodology for aeroelastic gust response of launch vehicles in flight is developed by using a previously validated aeroelastic stability analysis. The effects on the aeroelastic vibrations of a launch vehicle encountering a wind gust while operating at a particular supersonic flight condition are determined. A linearized dynamic aeroelastic analysis of the launch vehicles is performed using the previously developed procedure, but this time in supersonic flow. Then, the pressure on the moving launcher surface resulting from the combined motion induced by each elastic mode is obtained from the solution of the Euler equation. These effects are superimposed to determine the combined aerodynamic effects of all the modes. Thus, a generalized aerodynamic force matrix of the aerodynamic loads caused by the motion of the launch vehicles (rigid body, as well as elastic deformations) and the effect of a gust encountered in the flight is constructed. Finally, a generalized (iterative) eigenvalue analysis is performed to evaluate the aeroelastic stability of the linearized model of the launch vehicles, operating at the prescribed flow conditions, when it encounters a gust. This approach, along with the use the matched-filter theory on the resulting frequency response function, allows one to evaluate the effects of the worst-case excitation on the launch vehicle's aeroelastic response. The methodology has been applied to predict successfully the aeroelastic stability of LYRA launch vehicles when it flies through transverse gusts.