Evaluation of plasma-sprayed alumina as thermal control coatings for micro-satellites

• Main Author: Li, Renming
• Other Authors: Ng Heong Wah
• Format: Theses and Dissertations
• Published: 2008
• Subjects: DRNTU::Engineering::Materials::Plasma treatment
• Online Access: https://hdl.handle.net/10356/5595
• Institution: Nanyang Technological University

The thermal control subsystem becomes more important for micro-satellites, in view of reduction in packaging space and thermal mass. Therefore passive thermal control methods are preferred. However, most conventional thermal control materials (TCMs) deteriorate in the severe space environment, often leading to unanticipated mission problems. New and better TCMs are thus constantly sought to reduce difficulties in satellite thermal design. In this thesis, the suitability of plasma sprayed alumina coating as TCM for a satellite was examined. The results reveal that the alumina coating has good potential as a substitute for conventional TCMs for micro-satellite components. During these investigations, surface roughness of the coating was found very important because the roughness affects the radiation heat exchange between the surface and its surrounding. Roughness parameters cannot properly evaluate such effects on radiation properties of opaque surfaces. Two geometrical energy absorption models were therefore developed and applied, which predict effective normal solar absorptance and effective hemispherical IR emittance for a rough surface. Both of the models were validated. The model formulations are generic enough to be employed for the surfaces either of similar opaque materials or coated with such opaque materials where the substrates have little influence on the radiation properties.