Large silicon carbide optics for manufacturability

摘要

For space-based use, projected needs are for large optics of the one-meter class that lie under 30 kg/m~2 in mass areal density. Current space programs using glass optics, such as Kepler, exhibit a mass of 45 kg/m~2, while JWST beryllium optics, including hardware attachment, are as low as 18 kg/m~2. Silicon carbide optics can be made lighter than glass, although not as light as beryllium; however, distinct advantages in thermal conductivity and expansion coefficient are evidenced at all temperatures, allowing for greater thermal flux , minimizing gradients and maximizing performance, both earth and space looking. For manufacturability and production, it is desirable to minimize weight while maintaining reasonable cell spacing for open back lightweight design, which will reduce both cost and risk. To this end we perform a trade study to design such an optic that meets both mass and stiffness requirements while being within the regime of ease of manufacture. The design study chooses a hexagonal segment, 1.2 meters across flats (1.4 meters corner to corner), mimicking the JWST design. Polishing, mounting, test, and environmental operational errors are duly considered.