A highly reflective, white conductive coating system was developed using various layered coatings to maximize the structural, electrical, and optical reflectance properties for spacecraft radiators. The top layer of the system contains a highly reflective white pigment within a dissipative inorganic binder. This layer is above a highly conductive second layer containing a white conductive pigment within the same binder system.

The top layer reflects or scatters the majority of short wavelength (250 to 350 nm) incident solar flux while allowing the longer wavelength radiation to scatter within the coating to the second layer. Normally, this wavelength of light is absorbed by other inorganic white conductive coatings. This top layer is approximately 0.002 to 0.003 in. (≈51 to 76 μm) in dry film thickness and resides above a second layer that contains a conductive white inorganic system of 0.002 to 0.003 in. (≈51 to 76 μm) in thickness. The top layer is spray applied shortly after the lower layer application to allow for proper bonding.

The combination of the two layers provides a coating that has a lower solar absorptance than most other coatings less than 5 mils (127 μm) in dry thickness, and allows for dissipation of charge buildup on the surface. The system is applied using standard spray techniques for silicate coatings, and can be used in all situations where silicate-based coatings are acceptable.

The resulting finished coating has a beginning-of-life optical property of 0.09 (25% improvement over the best-performing available dissipative coatings), is no more than 0.006 in. (≈152 μm) in thickness, and has similar or improved static discharge capability than white dissipative coatings that have been baselined for spacecraft projects over the last two decades at GSFC.

The new layered thermal control coating allows a solar absorptance of 0.09 or lower, as measured on a Cary 5000 spectrophotometer at dry film thicknesses less than 0.006 in. (≈152 μm).

This work was done by Mark Hasegawa and John Petro of Goddard Space Flight Center and Kenneth O’Connor of Stinger Ghaffarian Technologies. GSC-16153-1


NASA Tech Briefs Magazine

This article first appeared in the October, 2014 issue of NASA Tech Briefs Magazine.

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