Culla A., La Mendola S.

Aim of this paper is the study of the sound pressure and the vibration levels of the upper part (fairing, AVUM, IS-3AVUM) of the VEGA launch vehicle during the liftoff and the transonic flight by the Statistical Energy Analysis (SEA). The acoustic loads applied to the launch vehicle upon the liftoff and the transonic flight are broad band and random. They may be dangerous for the payload and the equipments. A fast and cheap prediction of the sound pressure and of the vibration levels may be obtained by numerical procedures rather than performing measurements on real prototypes. The classical numerical techniques (FEM, BEM) fail to solve high-frequency dynamic problems, because the computational burden grows excessively, but also because the sensitivity of the numerical algorithms to uncertainties in the modal parameters increases with frequency so that the predicted response becomes meaningless. In this case a statistical approach seems more appropriate. SEA is, at present, the most useful method for solving this kind of vibroacoustic problems, by providing information on the stored mechanical energy and on the dissipated mechanical power between subsystems.