Abstract
Ground acoustic tests using stationary acoustic environments have been conducted to verify spacecraft resistance design against the transient random acoustic load during launch. Traditionally, a stationary acoustic test spectrum has been derived from a kind of short-time Fourier transform performed on transient random acoustic load, being enveloped. The envelopment, however, inevitably results not only in an excessively conservative spectrum, but also in the innate disparity between stationary and transient-random acoustic environments in their vibro-acoustic responses, diverting them from exhibiting equivalency for design verification. Furthermore, an excessively conservative spectrum forces unnecessary cost increase upon product design. One solution proposed in this paper is a method based on a vibro-acoustic single degree of freedom model, to derive the stationary acoustic environment condition with equivalent maximum load and cumulative fatigue damage of vibro-acoustic structure as in transient random acoustic environment condition, using extreme response spectrum and fatigue damage spectrum. The application of this method to actual flight acoustic data during launch demonstrates that it outweighs the conventional method in environmental resistance of structures with reduced conservative margin.
