NEWTONIAN THEORY FOR THE STAGNATION REGION OF TWO OPPOSING HYPERSONIC STREAMS

It is proposed that the zone of interaction between two opposing hypersonic streams can be described in terms of a thin layer of compressed gases bounded on either side by shock waves. Newtonian flow theory is used to analyze the interaction when one of the streams corresponds to the exhaust gas flow from a retro-rocket firing during flight of a high-altitude missile or spacecraft. The ambient density is taken to be sufficiently small that the exhaust gas flow expansion is large and can be assumed to be radial. The Newtonian thin layer solution yields adequately the shape of the interacting gas layers and their thicknesses in the stagnation region along the axis of symmetry of the colliding gases, but fails to provide accurate answers for downstream regions. This is a greater limitation on the utility of this solution as compared with the corresponding hypersonic blunt-body flow results, since, in contrast to the latter case, the sonic point, and hence the region of hot subsonic flow, extends a considerable distance downstream of the stagnation region. The theory is applicable in a band of high altitudes, the range being determined at low altitudes by rocket and vehicle sizes relative to the interaction zone dimensions, and at high altitude by viscous diffusion effects. Quantitative relationships are given that can be used to determine the altitudes of validity of the results. (Author)