Mid-high frequency vibrations of full-scale launch vehicles

Abstract

Launch vehicles are subjected at lift-off and during-flight ascent to a severe aerodynamic environment. This environment is broadband and random in nature. Electronic equipments and satellites are consequently excited and the random vibration levels induced must be predicted before flights for safety reasons mainly. There are several methods for predicting low- and high-frequency responses of structures such as finite-element methods (FEMs) and statistical energy analysis (SEA). However, mid-frequency range is still numerically difficult to reach. Two main issues are addressed in this article. The validation and implementation of a mid-frequency vibroacoustic strategy based on both the FEM and an energetic approach, the SEA-like approach, is the first objective. The validation of the hybrid method by comparison with the proper SEA is the second objective of the study. A full-scale numerical test case of the considered techniques was performed.