Reflection of sound by Sonic Crystals: an application to the aerospace engineering

Abstract

[EN] From the acoustical point of view one of the most extreme events is the lift-off of a rocket. In such events, an enormous amount of energy is liberated in the form of acoustic waves that are reflected in the launch pad, coming back over the rocket and affecting both the rocket and the load contained in the fairing. Here we propose a possible solution to reduce the sound pressure level in the area of the spacecraft-launcher: placing structures based on Sonic Crystals (SCs) at the launch pad to control waves reflecting on it. In this work preliminary reults, in linear regime and without considering dissipation, about the use of SCs to control the reflected waves in a broadband range of frequencies are presented. This proof of concept is experimentally tested in a sub-scale system, that works at ultrasonic frequencies in water. Different types of SCs and different geometries of the reflecting backing are tested. In particular, geometries that mimic that of the VEGA's launch pad of the European Space Agency (ESA).