Experimental investigation of gamma effects on heat transfer to a 0.006 scale Shuttle Orbiter at Mach 6

Real-gas effects on heating to the windward centerline of the Shuttle Orbiter and shock shape were simulated by testing a 0.006-scale Orbiter model in Mach 6 air and CF4 flows. The range of free-stream Reynolds number, based on model length, was 0.4 x 10 to the 6th to 5.3 x 10 to the 6th for air, resulting in laminar and turbulent heating. The Reynolds number for CF4 was 0.3 x 10 to the 6th and gamma was equal to 1.13, corresponding to a normal shock density ratio of 12 as compared to 5.25 in air. Angle of attack was varied from 15 deg to 45 deg in 5 deg increments. Centerline heating distributions were compared for the two gases, and to Mach 8 wind-tunnel data, predictions, and flight (STS-1 and STS-2) data. The present results revealed a significant increase in heating with increasing density ratio and decreasing Reynolds number at the lower angles of attack; the effects of density ratio and Reynolds number diminished with increasing angle of attack and were relatively small at the angles of attack for the hypersonic portion of Space Shuttle Orbiter flights STS-1 and STS-2. Wind-tunnel and flight heating distributions were in relatively good agreement, and the present heating rates in air were accurately predicted by a local infinite swept cylinder analysis.