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The broad overall objective of this continuing program is to develop equipment and procedures for measuring the important thermal radiation properties of materials, particularly those used in aircraft, missiles and space vehicles, at temperatures up to the melting point of the most refractory material, and to develop physical standards for checking such equipment and procedures. During the period covered by the report the specific objectives were (1) continued development of the laser-source integrating sphere reflectometer, (2) an error analysis of the shallow cavity technique for measuring normal spectral emittance, and (3) a study of the feasibility of preparing emittance standards for use at temperatures above 1400K (about 2000F). An error analysis of the shallow cavity technique for measuring total normal emittance of ceramic materials at very high temperatures showed that there was an error due to the translucency of the specimens that was as much as +60% for alumina, and a second error due to thermal gradients in the specimen that was on the order of -10%. Two new techniques were devised in the hope of greatly reducing the translucency error. Progress was made in developing codes to compute and correct for the thermal gradients present in the specimen. The laser-source integrating sphere reflectometer for measuring reflectance of specimens at very high temperatures was extensively redesigned to eliminate errors due to flux reaching the detector on the first reflection, and to convert the reflectometer from the substitution to the comparison mode. (Author), Rept. on projs. 'Materials Applications' and 'Design Information Development.'

The broad objective of this program is to develop equipment and procedures for measuring the important thermal radiation properties of materials, particularly those used in aircraft, missiles, and space vehicles, at temperatures up to the melting points of the most refractory materials. During the period covered by this report the specific objectives were to complete development of the laser-source integrating sphere reflectometer, and to prepare emittance standards for use at temperatures above 1400 K (1200F). The laser-source integrating sphere reflectometer consisted of (1) a 35 cm (20 The laser-source integrating sphere reflectometer consisted of (1) a helium-neon laser as a source, capable of operation at 0.6328, 1.15, and 3.39 micrometers; (2) a 35 cm (14 inc.) diameter sphere coated with barium sulphate or sodium chloride; (3) a lead sulfide detector; and (4) a radio-frequency generator for heating the sample by induction. (Author)