MEASUREMENT OF THE MODAL PARAMETERS OF A SPACE STRUCTURE IN ZERO-GRAVITY

An analytic and experimental study of the changes in the modal paramet ers of space structural test articles from 1 to 0 g is presented. Depl oyable, erectable, and rotary modules were assembled to form three one - and two-dimensional structures in which variations in bracing wire a nd rotary joint preload could be introduced. The structures were model ed as if hanging from a suspension system in 1 g, and unconstrained, a s if free floating in 0 g. The analysis is compared with ground experi mental measurements made on a spring/wire suspension system with a nom inal plunge frequency of 1 Hz and with measurements made on the Shuttl e middeck, The degree of change in linear modal parameters, as well as the change in nonlinear nature of the response, is examined. Trends i n modal parameters are presented as a function of force amplitude, joi nt preload, and ambient gravity level.