Flat absorber coating for spacecraft thermal control applications

SolarBlack is a bone-char-based surface developed as a flat absorber (black) thermal control surface for use on spacecraft. The surface, originally developed for use on the front shield of "ESAs" Solar Orbiter, is deposited using a technique known as CoBlast, developed by ENBIO Ltd. The resulting surface makes use of the material's highly stable ratio of solar absorptance to near-normal thermal emissivity (αs/ϵN) as well as its low electrical resistivity to regulate both temperature and electrostatic dissipation in service. SolarBlack is suitable for use on rigid and flexible metallic substrates, including titanium, aluminum, copper, stainless steel, nitinol, Inconel, and magnesium alloys. This work describes the thermo-optical properties, stability, and qualification of this surface for use on spacecraft components, as well as material characterization of the coating and bone char itself. The thermooptical stability of SolarBlack was determined using the Synergistic Temperature Accelerated Radiation facility space environment simulator in the European Space Research and Technology Centre, having previously qualified for use on Solar Orbiter. Material characterization was carried out using simultaneous thermal analysis, scanning electron microscopy, ultraviolet/visible/near-infrared spectrometry, and infrared emissometry.