Alumina Optical Surface Heat Shield for Use in Near-Solar Environment

摘要

Experiments indicate that coating a heat shield with alumina can significantly reduce spacecraft temperature during operation near the sun. A thin alumina (Al_2O_3) coating applied to carbon-carbon (C-C) reflects the majority of the visible solar irradiance while reemitting absorbed energy in the infrared. Testing on Al_2O_3-coated C-C coupons using visible and NIR lasers (from ambient to 1773 K) show that the solar-absorptance-to-IR emittance ratio (α_s/ε_(ir)) of the Al_2O_3-coated heat shield was 0.6 or less. Compared with an uncoated carbon-carbon heat shield, the coated version is at least 12% cooler, enabling thermal insulation mass reductions, improved scientific measurements, and the use of less exotic thermal protection materials.