Abstract:In recent years, the military application value of near space has received more and more attention. In order to study the aero-optical problems of the typical backward step structure of hypersonic aircraft, the direct simulation monte carlo(DSMC) method, which is a simulation method of rarefied gas dynamics, is used to study the flow characteristics of the backward step under different jet control in near space, and the ray-tracing method is used to study the aero-optical effect of flow field under different flow control. The calculation results show that as the flying height increases, the temperature of wall increases, and the aero-optical effect becomes weak. Among the four jet cooling methods, jet method A has the best cooling effect without increasing the aero-optical effect. Method B and D have certain cooling effects but make the aero-optical effect more serious.