Heat Transfer and Forces on a LiF Single-Crystal Disc in Hypersonic Flow

Abstract

The heat transfer, recovery temperature, pressure force and shear force were measured on LiF single-crystal discs at 300 K - 800 K and 60^o to 90^o angle of attack in a helium free jet wind tunnel. The smallest energy accommodation coefficient determined in free molecular flow was sigma E &#61 0,15, which reduced the heat transfer significantly also in the transition regime. The recovery temperature was larger than expected for complete accommodation. The sacttering distribution of a helium molecular beam on the crystals in UHV was measured after the wind tunnel tests and showed that the surface quality was good.