Spacecraft operating in the low Earth orbit (LEO) are exposed to an en
vironment characterized by very low pressure, various atomic species,
temperature extremes, ultraviolet (UV) radiation, electromagnetic radi
ation 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 bet
ween AO and other environmental factors have been dramatically demonst
rated in LEO flights and ground-based simulators. This paper investiga
tes 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 protecti
ve 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 c
oatings; (b) self-healing coatings based on special semi-organic polym
ers; (c) protective multilayered structures. An evaluation is made of
the properties and behaviour of different protective coatings on the p
olymers and composite materials used in spacecraft applications.