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Cable effects study : tangents, rat holes, dead ends, and valuable results

An overview of the study of the effects that electrical power and signal cables introduce on the dynamic response of precision structures is presented, along with a summary of lessons learned and most significant results. This was a three-year effort conducted at the Air Force Research Laboratory, Space Vehicles Directorate to discover a set of practical approaches for updating well defined dynamical models of cableless structures where knowledge of the cable type, position, and tie-down method are known. While cables can be found on many different types of structures, the focus of this effort was on precision, low-damping, and low-first modal frequency structures. Various obstacles, classified as tangents, rat holes, and dead ends, were encountered along the way. Rather than following a strictly technical flow, the paper presents the historical, experiential progression of the project. First, methods were developed to estimate cable properties. Problems were encountered because of the flexible, highly damped nature of cables. A simple beam was used as a test article to validate experimentally derived cable properties and to refine the assumptions regarding boundary conditions. A spacecraft bus-like panel with cables attached was designed, and finite element models were developed and validated through experiment. Various paths were investigated at each stage before a consistent test and analysis methodology was developed. These twists and turns are described.