Advanced Celestial Tracker Techniques

摘要

This report includes the results of ten months of study, with the objective to evaluate spectral radiation intensities from the shock and boundary layers associated with a hypersonic vehicle. The intended application is to predict the amount of radiant energy reaching the sensing element of a celestial tracker. The analytical phase of the study consisted of numerical solutions of the viscous and inviscid flow equations and the correlation of flow field properties in terms of readily available flight and vehicle parameters. The flow properties, in turn, were used to compute theoretical values of spectral intensity. The intensities were in turn correlated in the form of easy-touse charts and equations. The experimental phase consisted of the measurement of absolute spectral intensities from the conical portion of blunt cone models in a hypersonic wind tunnel. A scanning spectrometer was built and used to obtain multiple frequency scans, each lasting about five milliseconds, at two locations in the flow field. The observed spectral intensity curves were found to be several orders of magnitude greater than those predicted in the analytical phase. The experimental intensities increased toward the red end of the spectrum, whereas the theoretical intensities decreased. These facts, plus the observation of appreciable radiation when using nitrogen as a test gas, indicate that the experimental intensities are due to contaminants in the flow. (Author)