4.2.2 Tension Brace Antenna Feasibility Assessment 4.2.2.1 Background The Tension Brace concept may offer weight and cost advantages over a built-up section approach. The flat array is relatively insensitive to out-of-plane thermal distortions since the braces maintain a positive force on the flat array tension wires. The brace and flat array wires can serve as both structural members and conducting elements. In order to assess the concept feasibility structural arrangement drawings must be drawn, structural members need to be sized, the combined effects of thermal cycling, long term creep on wires, joints and braces need to be evaluated, and the feasibility of using structure for power transmission needs definition. In addition, methods of assembly to produce a flat pre-tensioned array in space needs to be evaluated along with alternate materials and relative costs. 4.2.2.2 Desired Output • Preliminary drawings of configuration options and selection of one of the following: - Square array - Triangular array - Round array • Selection of rectangular, triangular or radial grid for the flat array • Recommendation of the number of braces per assembly, brace size and wire size • Material options • Method of assembly in space • Long term strength/thermal and creep effects on wires and braces • Structural weight/cost analysis comparing three tension brace options with built-up section approach. 4.2.3 Local Crippling Stress Evaluation A study is required for the prediction of local compression crippling failure modes of very thin (0.1 - 0.15 mm) structural sections for various materials. The study should include tubular as well as other structural shapes such as hat sections, channels angles, sections of circles, etc. Of prime interest in the evaluation are the effects of initial imperfections induced in the fabrication process.
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