Nowadays carbon materials are widely used as ablating thermal protection for high-temperature structural elements in aerospace technology. Prediction of changes in the shape of the external surfaces of these elements, due to the burning of thermal protection, is closely related to the use of computational-theoretical methods describing the flow of various physicochemical and mechanical processes associated with the occurrence of the phenomenon under consideration. At the same time, it is crucial to test such methods on the results of experimental studies conducted under conditions which are implemented during the process of testing thermal protection in jets of aerodynamic units. The main elements of ablation of carbon materials include their erosion, i.e., mechanical ablation of mass, observed in high-pressure gas flows. In the process of experimental development, it is necessary to carry out research on large-scale models, which has led to widespread use of underexpanded jets of combustion products of liquid rocket engine combustion products for modeling the erosion process of thermal protection. The theoretical model of ablation of thermal protection in such jets requires taking into account the complex chemical composition of the gas mixture flowing into the model; physical and chemical interaction of this gas with thermal protection, which causes gasification of the latter; use of mathematical models describing the process of material erosion due to mechanical impact of high-pressure gas flow. The paper describes the development of the carbon material ablation calculating and theoretical methodology which could be used to determine the material erosion characteristics on the basis of solving a complex problem of circumfluence, heating, heat penetration and ablation of thermal protection.