Development of a Variable Emittance Radiator Based on a Perovskite Manganese Oxide

Two types of thermal control materials developed for space use are described. These new materials use a variable emittance radiator called the smart radiation device SRDs. The SRDs are based on La0.825Sr0.175MnO3 and La0.7Ca0.3MnO3 and comprise a thin and light ceramic tile. The materials undergo a metal-insulator transition near room temperature, and this allows the infrared emissivity of the device to change from low to high as the temperature is increased from 173 to 375 K. This is beneficial for thermal control applications on spacecraft. For example, bonded only to the external surface of the spacecraft, the SRD controls the heat radiated to deep space without electrical instruments or mechanical parts. Its function is similar to the thermal louver, but the SRD is lighter. This new device reduces the energy consumption of the electrical heater fur thermal control and decreases the weight and the cost of the thermal control system. Optical properties, such as the total hemispherical emittance and the solar absorptance, have been measured. Space environmental simulation tests were performed with independent irradiation by protons, electrons, and UV on the ground. Degradation of the materials' optical properties is discussed.