Spacecraft, such as satellites and deep-space craft, are exposed to a wide range of thermal conditions during service. A side facing the sun is heated by absorption of direct solar radiation, while a side facing the void of space is cooled by emission of thermal radiation. If the temperature of the structure or payload becomes too hot or too cold, structural distortion can occur resulting in reduced system capability. Furthermore, payloads such as electronics, batteries and other critical systems can experience lower efficiency, non-operation, shortened lifetimes or failures. Thermal control of the spacecraft is therefore important. Various techniques have been developed to reduce temperature variations in external structural elements such as antennas and booms, and to maintain the interior of the spacecraft at a temperature suitable for sensitive equipment, payloads, and occupancy by human beings.
In one thermal control approach, the external surface of the spacecraft is covered with an inorganic white coating. The coating is designed to absorb very little solar radiation, yet efficiently radiate thermal energy in the infrared spectrum, thus biasing the overall temperature of the satellite structure on which it is disposed towards cooler temperatures. The coating is substantially stable to the radiation and low pressure gaseous environment encountered in space without losing its thermal properties by discoloring, darkening, or otherwise degrading over time in the harsh environment of low to high earth orbit. For some applications, the coating also must be sufficiently electrically conductive to dissipate electrostatic charge on the surface of the spacecraft.
While prior art inorganic coatings may work well to prevent overheating of rigid spacecraft structures, they tend to be brittle and impliable, making them unsuitable for use on inflatable structures, deployable structures, flexible structures, reconfigurable or movable structures, and the like. However, deployable, inflatable, reconfigurable, flexible, and/or movable structures are becoming more prevalent on spacecraft. While mechanically flexible thermal control coatings can be made from organic binders and resins, they are highly susceptible to darkening and degradation over time due to solar and other sources of radiation, which increases their solar radiation absorbance and therefore increases their surface temperatures eventually leading to abnormal functioning or even premature failure of spacecraft components.
Accordingly, it is desirable to provide flexible thermal control coatings suitable for use on deployable, inflatable, reconfigurable, movable, or otherwise flexible structures of spacecraft. In addition, it is desirable to provide flexible thermal control coatings that maintain low solar radiation absorbance and high infrared emissivity during extended exposure to space environments. It is also desirable to provide methods for fabricating such thermal control coatings. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.