PASSIVE CONTROL OF LAUNCH NOISE IN ROCKET PAYLOAD BAYS

摘要

In space launch vehicles, external excitation of the vehicle fairing by acoustic orrnstructural loads can produce large acoustic pressure fluctuations in the internal payloadrnbay. These fluctuations can damage or destroy the payload, and have been blamed forrnmany first day satellite malfunctions.rnPassive vibration and acoustic absorbers, called vibro-acoustic devices or VADs,rnhave previously been used experimentally to reduce the levels of noise transmittedrnthrough the fairing. The aim of this project was to produce a model of the system (fairingrnand cavity) coupled to the VADs which allows the optimum VAD placement and designrnto be determined.rnThe modeling procedure used modal coupling to calculate the internal acousticrnpotential energy, which was used as a cost function to measure the efficiency of the noisernreduction strategy. The modal coupling method was validated against a fully coupled,rndirect finite element model and was found to provide results 1000 to 2000 times faster.