Advances in fabrication technologies for light weight CVC SiC mirrors

Abstract

Chemical Vapor Composite (CVC) Silicon Carbide (SiC) material has demonstrated superior optical polishing properties and high specific stiffness characteristics. These unique characteristics make CVC SiC a highly desirable material for aerospace reflective optics applications. The lack of material fabrication processes for CVC SiC has hindered the introduction of this material into the aerospace marketplace. Traditional methods of fabrication such as diamond grinding and lapping have proven to be expensive for CVC SiC material in aperture diameters that approximate 25cm or larger. Because of the extreme hardness of CVC SiC, the material removal rates are low and therefore larger size parts become very time consuming and thus cost prohibitive. Over the past two years several development efforts have been focused specifically toward fabrication technologies and methods to enhance the economical producibility of CVC SiC material. The results of these development efforts have revealed viable economical fabrication processes for CVC SiC. These fabrication processes have demonstrated material removal rates that are vastly greater than that of traditional diamond grinding and lapping process. This paper describes fabrications technologies and processes and material removal rates for fabricating monolithic, ultra pure, optical grade CVC SiC material.