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Low solar absorption surface coatings of aluminum, silver and silica with controlled emittance for spacecraft thermal control
New system requirements pertaining to thermal optical properties and coating electrical properties are commonly specified on non-low earth orbit missions. An increasing number of projects are specifying coatings with a surface resistivity of less than lE-9 ohm/square to mitigate electrostatic charge buildup events over a range of operational temperatures. There are a limited number of coatings that. meet these electrical property requirements while having flight derived optical properties in representative environments. Goddard Space Flight Center Code 546, Contamination and Thermal Coatings Group has recently explored the variety of electrically conductive white coatings available through domestic vendors to evaluate properties to meet project requirements in a geostationary orbit. The lack of significant flight data in representative environments required the careful selection of samples in ground based tests to establish end of life thermal properties. Attention must be given to the origin and pedigree of samples used on past on-orbit experiments to insure that the present formulations for the materials are similar and will react in similar manner.
Preparation of zinc oxide pigmented methyl silicone coating for thermal protection of space flight structures
Test chamber to simulate vacuum and heat sink characteristics of space, measuring optical constants of coatings
Modified process for anodizing 5657 aluminum alloy results in Al2O3 surfaces with infrared emissivities as great as 0.92 and solar absorptivities as small as 0.2. Coating enables fabrication of radiators requiring less surface, and hence less weight: radiators with coating weigh approximately 7 percent less than thermally equivalent radiators made with older anodizing processes. Coating applied easily and economically, and retains all of desirable properties of standard anodized coatings.
A white porcelain enamel coating was developed for application to high temperature metallic alloy substrates on spacecraft. The coating consists of an optically opacifying zirconia pigment, a lithia-zirconia-silica frit, and an inorganic pigment dispersant. The coating is fired at 1000 to 1150 C to form the enamel. The coating has a solar absorptance of 0.22 and a total normal emittance of 0.82 for a 0.017 cm thick coating. The coating exhibits excellent adhesion, cleanability, and integrity and is thermal shock resistant to 900 C. Capability to coat large panels has been demonstrated by successful coating of 30 cm x 30 cm Hastelloy X alloy panels. Preliminary development of low temperature enamels for application to aluminum and titanium alloy substrates was initiated. It was determined that both leaded and leadless frits were feasible when applied with appropriate mill fluxes. Indications were that opacification could be achieved at firing temperatures below 540 C for extended periods of time.
Effect of ultraviolet radiation on spacecraft low solar absorptance white coatings
Space-stable temperature control coatings - paints with low solar absorption/emittance ratios
Flight test of long term stability of temperature control coatings for spacecraft surfaces
Space environment simulation facility using solar simulator and other calibration and monitoring equipment
Powdered metal oxide pigments by nucleation for temperature control coatings
Space simulation tests on temperature control, inorganic and silicone coatings, zinc titanate pigment synthesis and evaluation, and silicone photolysis
SNAP-10A high emittance white coating, noting stability at 600 degrees F, irradiation and vacuum and mechanical vibration
Ferrocyanide and ferricyanide additives for prevention of optical degradation of coatings by ultraviolet radiation and vacuum
Control of vapor phase reaction kinetics to produce pigments by homogeneous nucleation
Theoretical models and spectral reflectance measurements of white pigmented, low solar absorptance coatings for spacecraft temperature control
Low concentration alkaline solution treatment of aluminum with metal phosphate surface coatings to improve chemical bonding and reduce coating weight
Formation of radiation-generated color centers using single crystals of magnesium oxide is discussed. Crystal structure of magnesium oxide is described. Chemical processes used to produce magnesium oxide with desired color center kinetics are presented. Proton irradiation of magnesium oxide crystals was conducted to determine lattice defects.