Multi-Mode Random Response Analysis Procedure

A frequency domain procedure for solving large-scale, multi-mode, multi-force, random vibration problems is described. The study was motivated by the need to perform transonic buffet load analyses for the Delta IIGlobal Positioning System GPS vehicle, for which wind-tunnel tests had been performed to collect fluctuating pressure data. The procedure can be applied to random response problems which are described by a general set of parameters. These include random support-excitation base-shake problems typical of component test situations. The main features of the procedure and the corresponding computer program, when compared to traditional procedures, are that, by taking advantage of modern computational capabilities, information such as frequency- dependent power spectral densities and cross-power densities can be used. To establish confidence in the implementation of the procedure, results from test problems were compared to values obtained by directly integrating the equations of motion in the time domain. These test problems, one of which was the Delta IIGPS, also demonstrate the feasibility of performing a buffet loads analysis in the time domain. Keywords Buffeting, Launch vehicle loads, Random vibration, Spacecraft loads.