The objective of this paper is to numerically investigate the three-dimensional side loads and associated flow physics of a conical nozzle during the fire-in-the-hole staging event of the multistage rocket. The transient flow in nozzle is examined by a three-dimensional time-accurate numerical method with the start-up process of the upper-stage motor and the prescribed nominal separating motion of the lower stage. The impacts of asymmetric lateral motion due to non-nominal staging movement on the nozzle side loads are also numerically analyzed. These motion deviations include the relative angle between axes of two stages, relative lateral displacement between two stages, superposition of relative angle with relative lateral displacement, and angle of thrust vector control. As presented in the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage. With the location of shockwave reflection approaching the dome of lower stag...

In this paper, the radome of 3/4 power series generatrix is taken as the object of study, and fluid-thermal-structure coupling field of it is simulated and analyzed with sequential coupling method. The aerodynamic load under Ma=6 flight condition is calculated using k ε-standard model. Then the finite element method is used to make structure thermal analysis and simulate the temperature field and strain field. The results show that the maximum thermal stress, strain and deformation of the structure always occur at the tip of the structure where the thermal expansion effect is obvious. The calculation results can provide an effective theoretical reference for the design of hypersonic vehicle structures and thermal protection systems.

This paper focuses on the integrated guidance and autopilot design with control input saturation in the end-game phase of hypersonic flight. Firstly, uncertain nonlinear integrated guidance and autopilot model is developed with third actuator dynamics, where the control surface deflection has magnitude constraint. Secondly, neural network is implemented in extended state observer (ESO) design, which is used to estimate the complex model uncertainty, nonlinearity and state coupling. Thirdly, a command filtered back-stepping controller is designed with hybrid sliding surfaces to improve the terminal performance. In the process, different command filters are implemented to avoid the influences of disturbances and repetitive derivation, meanwhile solve the problem of unknown control direction caused by saturation. The stability of closed-loop system is proved by Lyapunov theory, and the principles abided by the controller parameters are concluded through the proof. Finally, series of 6-DOF numerical simulations are presented to show the feasibility and validity of the proposed controller.

Loitering munitions would quickly reach the target area in the complex battlefield environment, and perform a variety of application advantages, such as total field reconnaissance, flexible cruise monitoring, weather monitoring, the battlefield damage assessment, relay communication and target attack, which has attached the widespread attention around the world. In this paper, each functional system model of the typical loitering munitions has been established. With the fact that the loitering munitions are faced with the problem of complex terrain, its launch battlefield environment and launch strategies under different terrain is analyzed and studied. And through the wind tunnel test of aerodynamic characteristics, the dynamic model of a small loitering munition is developed. In a typical topographical environment, based on genetic algorithm, trajectory optimization for a launch loitering munition is accomplished, eschewing the battlefield obstacles, the calculation results have great significance in technical guidance to engineering practices.