Optimized Asphere Fabrication and Finishing, for Future Optical Windows

Aspherical domes provide lower drag and radar signatures than hemispherical window designs but conventional finishing technologies have not been able to provide adequate optical surfaces. The fabrication of aspherical windows therefore remains a relatively under-developed technology for E/O windows for hypervelocity missiles. Development of deterministic microgrinding, coupled with magnetorheological polishing has made the optical finishing of aspherical domes possible. Hypervelocity windows are exposed to extreme thermal loads as well as requiring high resistance to erosion. Magnesium aluminate spinel is a hard optically transparent material with good thermal shock resistance and is presently being produced in hemispherical domes up to seven inches in diameter as a low-cost replacement for sapphire. Technology Assessment and Transfer will demonstrate that the existing fabrication technology can be extended to produce aspherical domes, and that these domes can be optically finished thereby producing a low-cost approach for the manufacture of hard, aspherical windows for a wide range of missile and hypervelocity applications in the UV, visible and MWIR.