Protective coatings for LEO environments in spacecraft applications

Abstract

Spacecraft operating in the low Earth orbit (LEO) are exposed to an environment characterized by very low pressure, various atomic species, temperature extremes, ultraviolet (UV) radiation, electromagnetic radiation and atomic oxygen (AO), which is produced by the dissociation of molecular oxygen by UV radiation. The destructive influence of AO on polymer-based materials and composites and the synergistic effects between AO and other environmental factors have been dramatically demonstrated in LEO flights and ground-based simulators. This paper investigates the effects of contamination, structure and the synergism between temperature and AO fluence on polymer-based materials, and provides an overview of the recent developments in the design and use of protective coatings for polymer and composite materials in the LEO environment and their testing in ground-based space environment simulators. Three trends in protective coatings research are identified and discussed: (a) the improvement of technologies for high-performance oxide-based coatings; (b) self-healing coatings based on special semi-organic polymers; (c) protective multilayered structures. An evaluation is made of the properties and behaviour of different protective coatings on the polymers and composite materials used in spacecraft applications.