SBIR-STTR Award

Brashear LP proposes to further develop ULE(TM) Lightweight Mirrors. The overall structural efficiency of primary mirrors, such as the one used in ABL or proposed for SBL, is currently limited by the minimum thickness of the core cell walls, and front and back face sheets that is achievable with traditional glass manufacturing methods. The technical objectives of this Phase I activity is to establish the lightest weight ULE(TM)primary mirror design that is achievable while retaining the performance characteristics necessary to satisfy the existing ABL program requirements using novel PM mirror manufacturing techniques. Special attention will be given to launch and/or landing requirements of SBL and ABL. This will entail trading front and rear face sheet thickness, core thickness, as well as cell wall thickness, cell size and geometry. In addition, Brashear LP will evaluate manufacturing techniques that allow an aggressively light-weighted PM to be realized without the complications of quilting print-thru of the core due to polishing pressures as well as 1-G release quilting for Space Based systems. Also, core manufacturing techniques will be evaluated which allow thinner face sheets and improve mirror manufacturing time by altering the current process by which cores and final mirrors are made.

Benefits:
The primary initial beneficiary for this SBIR effort is the USAF/BMDO Airborne Laser (ABL) program. The technology and processes developed under this SBIR will enable the ABL aircraft to meet aggressive weight targets at reasonable costs. Current technology is expensive and heavy. The higher level of performance will help support additional sale of ABL aircraft. The current approach uses conventional lightweight mirror technology, which has a significant weight penalty compared to the proposed approach. The reduced weight of the proposed optics will allow additional reductions in the size and weight of the structure required to support them. The technology developed will benefit all applications requiring the use of lightweight optical systems in dynamic environments. As substrate costs are reduced and performance goals are demonstrated, the market for space based and terrestrial applications will be opened to the technology as well. The ability to address terrestrial applications will be very cost dependent.

Keywords:
Light-weight, Primary Mirror, ULE(TM), Glass Mirror, Airborne, ABL, Structural efficiency

The technical objectives of this Phase 2 activity are to: 1) finalize the design, analysis, and generate drawings for an ultra lightweight primary mirror designed to meet the requirements currently specified on ABL, and 2) design, develop and generate a subscale, aggressively light-weighted primary mirror capable of demonstrating scalability and establishing a foundation for extruded core technology. The specific deliverable item to AFRL for this Phase 2 will be a 0.5 meter extruded core Fused Silica polished mirror (not coated) made with existing extrusion technology and dies assembled from 5 inch by 5 inch extruded core segments fused to a common face plate and back plate of appropriate thickness to demonstrate that a core with an areal density of less than 35 kg/m^2 can be manufactured with a curved surface. Additional parameters of the blank envisioned at this time include 0.25 inch by 0.25 inch square cells with 0.030 to 0.040 inch thick cell walls. These parameters may change as other dies for the extruded process are examined and evaluated for application to mirror technology.

Keywords:
Ultra Lightweight Mirror, Ule (Tm), Glass Technology, Extruded Core, Primary Mirror