Manufacture of Large-Scale Lightweight SiC Mirror for Space

Large-scale lightweight silicon carbide (SiC) mirrors were manufactured for space. Sintered SiC (SSiC) ceramic was adopted as the material to manufacture these mirrors. Complex structure designed for highly weight reduction and installation requirements was near-net-shape formed on SiC green body by digital machining technique before the high temperature sintering process. The dimensional accuracy of thin ribs and faceplate can be precisely controlled above 99.5%. During sintering process, the temperature distribution was kept uniform enough to avoid residual stress and deformation in the whole furnace. Isotropic shrinkage occurs during densification from SiC green body to ceramic with a fluctuation less than 0.3%, which is the dimension error of the final size as well. Mirror surface with low surface roughness, high shape accuracy and reflectivity was finished by polishing and plating. Moreover, large-scale lightweight SSiC mirror was demonstrated to be suitable for space use by tests simulating launch conditions and space environments.