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Design of structural geometries for large telescope enclosures Wong, Vanessa

Abstract

With the rapid advancements in telescope technology, the next generation telescopes will be on the order of 20 - 50 [m] in diameter. Since traditional telescopes have been substantially smaller, this huge increase in telescope size necessitates a study into new solutions for telescope enclosure geometry. In an attempt to come up with new geometries for large telescope enclosures, a study was carried out on Platonic and Archimedean spheres. After careful consideration, the Platonic icosahedral sphere (a type of geodesic dome) and the Archimedean rhombicosidodecahedral sphere was selected for further analysis. Sensitivity analysis was performed on the two selected configurations by varying the enclosure radius (R), and the member cross-section size (CSS), thickness (T), and type (CT). A 3-dimensional model of each case was generated in a finite element analysis program and the corresponding nodal deflections and member forces were obtained. After plotting the results, it was discovered that for both the rhombicosidodecahedron and icosahedron configuration, the optimal R is 25 [m]. The optimal CSS for the rhombicosidodecahedron configuration is 0.35 [m] while the optimal CSS for the icosahedron configuration is 0.3 [m]. The optimal T for both configurations is 0.02 [m]. In addition, the optimal CT for the rhombicosidodecahedron configuration is circular while the optimal CT for the icosahedron configuration is square. The two configurations were also compared against one another and it was discovered that the icosahedron configuration generally performs better than the rhombicosidodecahedron configuration. In addition to exploring new structural geometries for telescope enclosures, one must not forget all the expertise which has been put in older telescope enclosures. PhotoModeler is a photogrammetry software which allows its user to take pictures of an existing structure then generate 3-dimenional models using various functions in the software. Using this program, one can combine structural attributes from older telescope enclosures with new geometries to create a hybrid enclosure suitable for next generation telescopes. Finally, as a supplementary to the structural geometries suggested in this report, several composite materials which may be suitable for use as cladding are also presented. These composite panels include: metal composites, polymer composites, and honeycomb core composites.

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