Light Weight Thermally Balanced Graphite Reinforced Mg Structural Substrates for Replicated Mirror Membranes

Magnesium reinforced with a quasi-isotropic high stiffness graphite preform has the highest combination of specific stiffness (E/r) and thermal stability (thermal conductivity/CTE) of any material other than expensive CVD/SiC.This unique combination of properties coupled with ease of fabrication and machining makes it the most attractive candidate for light weight space and airborne mirrors. Mg/Gr can be CTE tailored to a replicated membrane material, machined to figure andbonded to a low cost membrane. The result will be a high performance, low mass mirror material with short delivery lead time. Polymeric and metallic nanolaminate replicated membranes will be attached to a tailored Mg/Gr structural substrate and examinedfor print-through and fidelity to the figure and finish of the master optical mandrel. With stiff Mg/Gr mirror substrate planes and planar-isotropic Mg/Gr core, the areal density is projected to be less than 6 kg/m2. The development of high stiffnessgraphite fiber reinforced Mg and Al would result in the lowest mass and lowest cost mirrors available without sacrificing performance. Lead time for manufacturing would be a few weeks rather than months to years once the master optical mandrel has beeninstalled. A 5-10 kg/m2 areal density rigid space mirror material will become readily available to the space and missile defense community with short lead times. Cost of fabricating mirrors will be a fraction of that of glass, beryllium or other competitivematerials. Innovative control of fiber architecture will result in low thermal expansion, high thermal conductivity and high stiffness, and hence, in a highly stable mirror with high vibration dampening capacity. Economic benefits will be measured inlaunch weight reductions and increased system performance as well as system procurement savings. Immediate applications will be for EKV, CEKV, LEAP, directed energy applications, ABL as well as a number of AF, NRO and NASA applications. Alternativeapplications in electronic thermal management markets will also benefit from the concurrent development of the preforming technology developed for mirror substrates.