Shock Tunnel Testing of the Transpiration-Cooled Heat Shield Experiment AKTiV

Abstract

The present paper presents shock tube testing of the transpiration cooling experiment AKTiV flown on the sub-orbital re-entry body SHEFEXII. The campaign comprises testing of a 1:3 subscale model at original Reynolds number, Mach number and velocity, so that the subscaling has to be compensated for by rising the gas density. This, in turn, results in increased heat flux to the surface compared to the original. The shock tube experiments are supported by fluid dynamics computations by code TAU. Moreover, for lay out and design of the transpiration-cooled thermal protection element, the semi-analytical tool HEATS is introduced, based on a transient heat balance at the surface. Heat flux to the structure is measured just up- and downstream of the cooled sample. The measurement shows that heat flux is reduced upon coolant exhaust. Comparison of these results with HEATS shows that the heat flux predicted with HEATS is in good concurrence with the measured heat flux values at various angles of attack. HEATS results enables prediction of the cooling efficiency, giving an average heat flux reduction to 11.11% upon transpiration cooling for a coolant gas flow of 0.39 g/s and a variety of angles of attack.