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The present paper presents the in-flight measurement of the transpiration cooling experiment Aktive Kühlung durch Transpiration im Versuch (often referred to as AKTiV) flown on the suborbital reentry configuration Sharp Edge Flight Experiment II (often referred to as SHEFEX II). Thermal response of the structure is measured just upand downstream of a cooled sample with a noncooled reference setup on the opposite side of the vehicle. The measurement shows that the heat flux is reduced upon coolant exhaust. The maximum temperature reduction with 87 K is observed on the porous sample, while downstream the sample, the temperature is reduced by 75 K by film cooling. This corresponds to cooling efficiencies of 58 and 42% on the sample and downstream, respectively. The evaluation is supported by the semi-analytical tool HEATS, based on a transient heat balance at the surface. Comparison of the results with HEATS shows that the heat flux predicted with HEATS is in good concurrence with the measured temperatures on the cooled sample, as well as upstream and downstream with a maximum deviation by 14%. The analysis suggests that the flow condition around the sharp-edged, faceted vehicle remained laminar longer than expected. Nomenclaturem M = Mach number, -_ m = mass flow rate, kg∕s Nu = Nusselt number, -Pr = Prandtl number p = pressure, Pa R = gas constant, J∕kg · K Re = Reynolds number, -r = recovery factor, -_ q = heat flux, W∕m 2 St = Stanton number, -T = temperature, K t = time, s u = velocity, m∕s α A = heat transfer coefficient, W∕m 2 · K α V = heat transfer coefficient, W∕m 3 · K ϵ = emissivity, -η = cooling efficiency, -κ = isentropic coefficient, -λ = thermal conductivity, W∕m · K μ = dynamic viscosity, Pa · s ρ = density, kg∕m 3 σ = Stefan-Boltzmann constant, W∕m 2 · K 4 ϕ = porosity, -Subscripts C = at panel C c = coolant cond = heat conduction conv = heat convection F = film HG = hot gas p = at constant pressure r = recovery rad = radiation res = reservoir S = surface x, y = coordinates W = wall 0 = plenum ∞ = ambient

The present paper presents the in-flight measurement of the transpiration cooling experiment AKTiV flown on the sub-orbital re-entry configuration SHEFEX II. Thermal response of the structure is measured just up-and downstream of a cooled sample with a non-cooled reference set-up on the opposite side of the vehicle. The measurement shows that the heat flux is reduced upon coolant exhaust. The maximum temperature reduction by transpiration-cooling is observed on the porous sample with 87 K, while downstream the sample, the temperature reduction by film cooling is 75 K. This corresponds to cooling efficiencies of 61% and 46% on the sample and downstream, respectively. The evaluation is supported by the semi-analytical tool HEATS, based on a transient heat balance at the surface. Comparison of the results with HEATS shows that the heat flux predicted with HEATS is in good concurrence with the measured temperatures on the cooled sample, as well as upstream and downstream with a maximum deviation by 14%. The analysis shows that the flow condition around the sharp-edged, faceted vehicle remains longer laminar than expected.