Abstract
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.