| الوصف: |
Thin carbon fibre reinforced polymer (CFRP) tape-springs are attractive structures for use in space-based instruments because of their compact stowed configuration, highly repeatable unfolding and relatively high dimensional stability. Potentially, high-accuracy applications such as optical telescopes might benefit from this technology. In the era of miniaturisation in the space industry and given the relevance of the Earth Observation (EO) sector, the launch of multiple smaller spacecraft equipped with deployable payloads would provide a cost-effective solution for frequent coverage. Within this thesis, the dimensional stability of deployable optics in the space thermal environment is investigated. In the past, some relevant missions employing deployable booms experienced significant thermally-induced disturbances which might be particularly detrimental for satellite imagery. The thermo-mechanical properties driving the thermo-structural response have been identified by implementing screening methods based on Elementary Effects (EE) into the Finite Element (FE) model of the telescope. The novel implementation of this statistical approach for the analysis of laminates has been also supported by analytical examples, and has proven to be fast and versatile. The most influential parameters have been found to depend strongly on the stacking sequence. Then, the FE model has been updated with coefficients of thermal expansion (CTE) found experimentally using strain gauge techniques, which are inexpensive and adjustable for a variety of materials and specimens. Different orbit scenarios and illumination conditions have been also explored. The suitability of tape-springs for a telescope has been found highly influenced by the thermo-optical properties, which ultimately depend on the surface finish. The mock-up of the telescope in the deployed configuration has been tested following an interferometric approach. A 3 degrees of freedom (3-DoF) interferometer has been developed by using commercial-off-the-shelf (COTS) optical components, hence reducing the costs considerably. The reconstruction of axial displacements and relative tilts, with a resolution of 10⁻⁹ m and 10⁻⁶ rad respectively, has been performed by analysing the interference fringe pattern moving on the CMOS sensor. Uncoated and coated configurations have been tested, showing approximately a 50% decrease in the maximum axial displacements. |