Lockheed Martin Space Systems Company (LMSSC) and Vicus Technologies have conducted a study to obtain the thermal, structural and optical property data required to predict the flight performance of Multispectral Zinc Sulfide (MS ZnS) windows. The Naval Air Systems Command (NAVAIR) provided technical guidance during the planning, test execution and data analysis segments of this study.Test coupons were fabricated by the Pacific Optical Division of Recon/Optical, Inc. from two lots of Rohm and Haas optical-grade MS ZnS. Witness coupons from each lot established the microstructure at two stages during processing as grown by chemical vapor deposition and after hot isostatic pressing. Test coupon fabrication was controlled by specifications applicable to full-scale windows. Coupons from both lots were included in all tests.Thermophysical tests were conducted at the Thermophysical Properties Research Laboratory (TPRL). The thermal conductivity, specific heat and thermal expansion of three coupons were measured from 40 C to 370 C. Thermal conductivity was measured using two variations of the laser flash diffusivity technique (ASTM-E-1461).Transmittance and reflectance of uncoated coupons were measured at the National Institute of Standards and Technology (NIST) at selected wavelengths from 2 to 14 mm. Coupons were tested at temperatures of 23 C to 250 C and at angles of incidence of 0 to 60 degrees. Two measurement techniques were applied to span the range of test conditions. Duplicate testing at selected conditions compared the results from both measurement techniques.Measurements of the optical scatter of uncoated coupons were conducted at Schmitt Industries. Two locations on coupons from both lots were tested. Bidirectional transmittance and reflectance distribution functions were measured using laser sources at wavelengths of 3.39 and 10.6 mm and at selected angles of incidence up to 70 degrees.Structural tests were conducted at the University of Dayton Research Institute (UDRI). ASTM-C-1161 four-point flexure tests were conducted at 21 C on 24 coupons and at 200 C on 23 coupons. A fully-articulated fixture was used to test the type-C-sized flexure bars. Nomarski photographs documented the pre-test condition of the tensile face and edges of each flexure bar. Young s modulus and Poisson s ratio were measured using the ASTM-E-1259 technique. Coupons were tested at temperatures of 21, 100 and 200 C.Fractography to document the failure origin in all flexure bars was conducted at NAVAIR. Selected coupons were also evaluated by the University of Florida to establish crack sizes at each failure origin. Statistical analysis of flexure data was performed at NAVAIR.This study has yielded much of the data required to design MS ZnS windows and predict flight performance.
Proceedings Title: Proceedings| |11th DoD Electromagnetic Windows Symposium
Conference Dates: May 1-4, 2006
Conference Title: DOD Electromagnetric Windows Conference
Pub Type: Conferences
fractography, optical properties, thermal conductivity, young's modulus, zinc sulfide