Innovative Vibroacoustic Control Approaches in Space Launch Vehicles

Vibroacoustics during space vehicle launch has been blamed for as many as 60% of first day satellite failures. At the Air Force Research Laboratory in Albuquerque NM USA, modeling and analysis was performed to determine the feasibility of various control approaches to reduce noise levels of the shroud interior. Candidate active actuation technologies included PMA’s, piezoceramics and volume-velocity acoustic sources. 1 INTRODUCTION This paper combines the work of three feasibility studies on innovative active noise transmission reduction approaches directed at a specific launch vehicle [1,2]. Analytical studies using piezoceramics and proof mass actuators were accomplished using a modal interaction model along with an optimal control approach. The focus of these studies was to calculate the maximum performance of each approach when realistic constraints were imposed. The third study started with experimental results at relatively low acoustic levels. These results were then scaled to project the power and actuator requirements necessary to accomplish the same performance at more realistic acoustic levels. The objective in the first two studies was to reduce acoustic transmission directly, whereas the objective in the third study was to add dissipation to low frequency cavity modes. The goal of all three approaches is lower interior acoustic levels during launch. 2 FEASIBILITY STUDIES All three feasibility studies have in common the fairing geometry shown in Figure 1. The modal interaction model is given by ż = [ A B′′′ B′′ A′ ]