Design of a Support and Foundation for a Large Lunar Optical Telescope

by Koon Meng Chua, Univ of New Mexico, Albuquerque, NM, USA,
Stewart W. Johnson, Univ of New Mexico, Albuquerque, NM, USA,
R. Sahu, Univ of New Mexico, Albuquerque, NM, USA,

Abstract: NASA is considering a large lunar telescope [LLT] and a smaller diameter precursor telescope experiment on the Moon. The preliminary design of the 16-meter optical aperture is being performed at the NASA George C. Marshall Space Flight Center. This paper presents the design analysis and consideration for the support structure and the foundation for this telescope. The proposed support structure is a hexapod which will be supporting the 52.5-ft (16-m) mirror through a gimbal and trunnion assembly. Each hexapod leg will consist of seven 2 inches (51 mm) diameter thin-walled tubes bundled together. Graphite-epoxy, graphite-aluminum and graphite-magnesium were considered for these tubes. The hexapod legs were found to be critical in buckling. The foundation is a multiple contact points spud-can type footing. A finite element analysis was performed using GEOTZD which was written at the University of New Mexico. This code considers nonlinearly elastic materials, large deformation, and is computationally stable even when analyzing very low stiffness materials and at low stress levels. This code was used to predict the load-displacement characteristics of the footings. The proposed footings are 60 inches (152 cm) in diameter and are shown to be applicable over the known extremes of the regolith stiffness. The effects of temperature fluctuation were compensated for by specifying a structural material with near zero thermal expansivity.

Subject Headings: Telescopes | Foundation design | Moon | Footings | Support structures | Federal government | Tubes (structure) | Minerals

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