Low Cost, Precision Composite Mirrors for Exoatmospheric Interceptor Seekers

Exoatmospheric interceptor seeker mirrors and metering structures have traditionally been designed and fabricated from beryllium. While beryllium has many structural advantages, it is expensive and requires a substantial lead time for fabrication that seriously curtails designer's options. A Phase I study concluded that there is only one other material system, carbon-carbon, that satisfies all of the opto-structural, structural dynamic, humidity and nuclear threat environments. The Phase II program will design, fabricate, and test a carbon-carbon primary mirror. Figure and surface finish will be achieved through a combination of carbon-carbon substrate replication, SiOx, glass, coating applied to the substrate using a vacuum deposition process, and magneto-rheological finishing. In addition, a chemical vapor infiltration process will be used to fill the pores and provide a seal coat in the carbon-carbon to preclude dust and moisture contamination during storage and operation. The two characteristics that differentiate carbon-carbon from other materials are radiation hardening and dimensional insensitivity to moisture. The primary benefits of carbon-carbon are lower cost and reduced fabrication lead time. This program will fabricate primary mirrors that will be evaluated for its natural frequencies, its long term thermal stability, its compatibility with gold coatings, and its radiation hardness performance.