MODAL TEST OF A LARGE SPACECRAFT USING A MASS-LOADED INTERFACE

A finite-element mathematical model of a large spacecraft structure is validated through a modal test survey. The spacecraft is bolted via its adapter to a steel base plate which served as an inertial reaction mass. The inertial base plate supported by five low-frequency air supports provides a free-free boundary for the combined plate/spacecraft system. Sufficient separation between rigid and flexible mode frequencies is verified by measuring rigid-body mode frequencies. This technique is aimed at producing test boundary conditions which could be easily reproduced in analysis and a modal vector set to simulate the in-service modal vectors. (O.G.)