Multifunction smart coatings for space applications

This paper describes a new multifunction smart coating that can provide atomic oxygen (AO) and electrostatic discharge (ESD) protection, while also improving the thermal control of space structures. The methodology is based on a passive thin-film structure employing VOn transition metal oxides that exhibit a metal to insulator transition. The coating, depending on its formulation, can provide a variable heat-transfer/emitter structure that operates passively in response to changes in the temperature of the space structure, by dynamically varying the ratio of solar absorptance (alpha) to thermal emittance (epsilon). This enhances self-heating of the structure at lower temperatures and cooling through thermal radiation at elevated temperatures. Work is currently underway to apply this coating to various polymers and membranes to improve their performance in space. In the space environment, such as low Earth orbit (LEO), the coating will be subject to various stresses including VUV radiation and AO. Atomic oxygen testing in a simulated environment at CSA indicated no resolvable change in the morphology or thickness of the coatings. The thermo-optic characteristics after AO exposure were similar to the "as deposited" films. Additional long-term radiation exposure at the Centre National d'Etudes Spatiales-France (CNES), equivalent to three years in a geostationary orbit (GEO) environment, resulted in a change in the coating epsilon and alpha of less than 0.002.