The design, analysis, construction, and testing of a multifunctional composite satellite structure

Abstract

A small space based telescope is being designed by the Charles Stark Draper Laboratory, Inc. in conjunction with MIT. The design goal of this project is to use existing technology to gather ground data from low earth orbit at a minimal cost. A structure was constructed at MIT that allows the satellite to survive launch loads and maintains the optical stability of the satellite. The structure is a double hull design constructed of AS4/3501-6 graphite epoxy with a zero coefficient of thermal expansion lay-up to prevent defocussing of the optics due to thermal loading. The overall design goal at MIT is to construct a space worthy structure. This thesis includes the preliminary design of the inner structure that houses the optics for the telescope. Design of the outer structure, the connections between the inner and the outer structure and detailed design of the inner structure are not included in this work. The analytical techniques used in this project included thermal analyses of structures in various earth orbits, determination of structural requirements from optical performance calculations, designing of near zero Coefficient of Thermal Expansion (CTE) laminates, consideration of manufacturing and material variations in design, strength analysis of composite laminates, and determination of vibration modes and associated frequencies of tubular structures with anisotropic sandwich construction. Experimental work included the building of co-cured honeycomb panels, curved panels, and tubular sections to verify the structure as designed was manufacturable. These efforts culminated in the production of a space-worthy component. Testing was preformed to verify the analysis and design. Testing included flatwise tension testing to verify integrity of the honeycomb bonding, tensile testing to verify stiffness calculations and experimentally determine the failure load for the desired lay-up, and testing to verify the CTE was within acceptable bounds to prevent the optics from defocussing.