The paper analyzes main control aspects of thrust jet engines, which use fuel components in different states of aggregation (solid fuels - liquid oxidant, a solid oxidizer - liquid fuel). Following the analytical review of literature a conclusion has been drawn that it is technically and functionally complicated to provide a process of thrust control by changing the mass flow and the combustion rate of a solid fuel charge.

The objective of this work is to give a theoretical prediction of how the thermal knife impacts on the local combustion rate.

The paper presents a diagram of interaction between thermal knife and solid fuel. There are three modes, namely: pyrolysis, transition (from pyrolysis to cutting charge), and fuel cut. In the computational model generation it is assumed that the solid fuel combustion rate is not dependent on the combustion direction, and the temperature distribution along the length of the charge (in the direction perpendicular to the face) obeys the Michelson dependence without considering a resistance of the heated layer at the surface of the combustion charge. The paper considers mechanical interaction of the thermal knife with the surface of charge. The Hertz formula describes the relationship between the pressing force, the penetration depth and the radius of thermal knife mark in the fuel.

Numerical modeling methods and direct calculations allow us to obtain relationships to describe the changing local combustion rate under the action of the thermal knife on a solid fuel charge in its mechanical penetration, depending on the blade geometry, mechanical properties of charge and pressing force.