Analysis of the Aerodynamic Ablation of a Metal Sphere

Abstract

Abstract : An approximate analytic solution has been developed for the ablated volume and shape of a metal sphere at hypersonic speeds in the early stages of aerodynamic ablation. The process of ablation, due to aerodynamic heating, is a very complicated phenomenon because of the possible existence of two layers - gas and liquid. If the metal surface is molten, then a liquid layer of molten metal is formed between the boundary layer of gas and the solid surface. The interdependent factors flight time, flight conditions, and body shape cause a variation of aerodynamic characteristics as a function of the trajectory. Furthermore, the aerodynamic ablation is responsible for a change in the shape of the body. Two cases of aerodynamic ablation were investigated. The first case considered the melting of body material alone, and the second considered melting with partial evaporation. The analysis given in this report is useful to determine the flight conditions under which the metal sphere may travel with little or no ablation. With the assumption that the flow over the sphere is laminar, Newton's impact theory is applicable and the gas does not dissociate; the total ablated volume and shape of the sphere can be computed as a function of flight trajectory by using the analysis developed in this report. (Author)