SBIR-STTR Award

In order to enhance missile performance, future missile designs will incorporate domes with a more aerodynamic shape than the traditional hemisphere. Significant additional benefits in areas of performance and cost reduction would be realized if a new material with more robust properties and the ability to be formed to near net shape replaced more common materials, such as sapphire. One promising replacement is polycrystalline alumina (PCA) with sub-micron grain size. It can be made to have improved toughness and nearly the same optical transmission in the mid-wave infrared (MWIR) band as sapphire. There is no established fabrication process suitable for this material or the aerodynamic shapes of interest; conventional finishing processes used to manufacture flat and spherical optics are not appropriate for such complex shapes. A process that utilizes deterministic micro-grinding, Magnetorheological Finishing (MRF) and newly developed MR Jet provides significant and unique advantages for finishing both the convex and concave surfaces of such conformal shapes. Work in Phase I will demonstrate: 1) a full manufacturing process on PCA flats from material blank through final polishing that meets transmission specifications and 2) the ability to fabricate precision domes with the proposed process. Successful completion of Phase I activities will enable the manufacture of PCA ogives during Phase II.

Keywords:
Magnetorheological Finishing (Mrf), Magnetorheological (Mr) Jet, Jet Polishing, Spot, Sub-Aperture Polishing, Sub-Aperture Stitching Interferometry (Ssi), Conformal Optics

In order to enhance missile performance, future missile designs will incorporate domes with a more aerodynamic shape than the traditional hemisphere. Significant additional benefits in areas of performance and cost reduction would be realized if a new material with more robust properties and the ability to be formed to near net shape replaced more common materials, such as sapphire. One promising replacement is polycrystalline alumina (PCA) with sub-micron grain size. It can be made to have improved toughness and nearly the same optical transmission in the mid-wave infrared (MWIR) band as sapphire. There is no established fabrication process suitable for this material or the aerodynamic shapes of interest; conventional finishing processes used to manufacture flat and spherical optics are not appropriate for such complex shapes. A process that utilizes Magnetorheological Finishing (MRF®) and newly developed MR Jet provides significant and unique advantages for finishing both the convex and concave surfaces of such conformal shapes. Work in Phase I demonstrated the suitability for MRF and MR Jet to finish PCA material, as well as the advantages of using MR Jet to finish the concave surface of domes to achieve extremely high precision. The work in Phase II will be a collaborative effort that will culminate in finished ogive domes suitable for testing in missile systems.

Keywords:
Magnetorheological Finishing (MRF), Magnetorheological (MR) Jet, jet polishing, sub-aperture polishing, sub-aperture stitching interferometry (SSI)