Emissivity of rocket plume particulates.

Abstract

The optical properties of motor aluminum oxide are required inputs to current plume signature prediction codes, such as SIRRM. Accurate predictions are possible only if variations in the particle emissivity due to changes in particle size, contamination, and changing temperature, etc. , are known . This investigation demonstrated a simplified method for determination of the emissivity of rocket motor generated alumina. Plume particulate material was collected on tungsten alloy wire during motor firings. A DC circuit was used to resistively heat the material, and the temperature was determined at various points by relating the wire resistivity to circuit current and voltage. An Agema Thermovision infrared (3.5-5 (j.) camera and microscope were used to observe the material during heating, and broad-band emissivity was computed using system software. It was estimated that the emissivity could be measured with an accuracy of ± 3%. Motor alumina was found to have significantly greater emissivity than pure alumina in the temperature range of 500-1200K.