Aerodynamic heating during re-entry of space vehicles at hypersonic speeds is one of the key problems of space transportation as the knowledge of the heating rates is very important for the dimensioning of the thermal protection systems. For quantitative heat transfer measurements in short-duration facilities a high-speed infrared camera is applied by the DLR Institute of Aerodynamics and Flow Technology..
The evaluation of the measured temperature pictures is analyzed by the self developed software tool HeatFIT that allows a fast calculation and visualization of heat flux distributions directly after the test run. The automatic marker-based 3D-reconstruction of the thermal images and the mapping of the data values onto the 3D grid of the model surface, implemented in this tool, enables some precise heat-flux calculations also at vibrating or moving (e.g. rotating) test objects. The analysis of the data on the node points of these surface grids facilitates the comparison with results of complementary CFD-calculations.
Typical results of heat-flux measurements on a body of revolution, evaluated by HeatFIT and visualized via TECPLOT, are presented on the picture right.
This technique is not limited only to short-duration wind tunnels and can be used in continuous working facilities for qualitative heat-flux measurements (transition-detection, etc.).
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