Abstract

The requirements for extremely lightweight low- distortion/high-stiffness optical components continue to grow across a wide spectrum of use from very small scanner mirrors to very large space- based telescope mirrors. The traditional materials for these applications, low-expansion glasses and beryllium, have limitations in both properties and fabricability, and both are very expensive and time-consuming to fabricate into lightweight configurations. Silicon carbide has a modulus equal to or greater than beryllium, a density equivalent to aluminum, a low coefficient of thermal expansion, and a high thermal conductivity, making it an excellent material, propertywise, for many uses. It is also relatively inexpensive, abundant, and nontoxic. Until recently silicon carbide was limited in application to the desired devices by its extremely difficult fabricability. It simply could not be formed into lightweight structures. A new process developed by United Technologies Optical Systems (UTOS) now not only allows the fabrication of lightweight structures but also allows them to be structurally highly efficient. Using their precision forming process, UTOS can now fabricate honeycomb sandwich structures that are both lighter and stiffer than even beryllium structures due to limitations in achievable configurations of the beryllium fabrication processes. Many low- weight high-performance applications may benefit from this technology.

© 1988 Optical Society of America