In order to achieve lightweight, low cost and refined thermal design, the refined design method of coating thermal protection structure based on ablation mechanism is proposed. It can calculate the thickness of ablative carbon layer with using ablation mechanism, build thermal simulation model of ablation refinement and calculat accurate thermal simulation results. The application of this method can provide an effective and scientific theoretical analysis method for the demonstration of coating thermal protection scheme. It can guide the design of thermal protection scheme, reduce the design cost and shorten the development period.

The use of sinusoidal scanning vibration to simulate low-frequency transient vibration environment is a traditional testing method in the aerospace industry, and its environmental assessment of products may have both under testing and over testing simultaneously. Firstly, the equivalence between the two is analyzed, and then relevant theories such as impact response spectrum and maximum response spectrum are used to study the scanning rate and damping coefficient in the formulation of equivalent sinusoidal scanning vibration test conditions, and parameter selection suggestions are provided. Finally, steps are proposed to establish the testing conditions for sinusoidal scanning vibration environment, providing reference for the low-frequency transient environment adaptability assessment using sinusoidal scanning testing.

In order to investigate the evolution of vertical water-entry cavity of a sphere, a numerical simulation for modeling the vertical water-entry of a sphere was performed, which is based on Navier-Stokes equations, volume of fluid model and dynamic mesh. It showed that numerical results compared favorably with the experimental results, which verified the accuracy of the simulation method. In addition, during the early period of the water entry, there was a high impact load on the sphere and a splash rose from the surface, and then a water-entry cavity which was open to the atmosphere formed. The cavity experienced development, closure and collapse periods after its formation. Pressure acting on the cavity was the main cause of the deep closure, and high speed up-jet and down-jet appeared after the closure.

Aiming to study the wave effects on the water-exit process of aquatic-aerial vehicles, a hemispherical-head axisymmetric vehicle are simulated to exit through different irregular waves based on the P-M spectrum. Both kinetic and dynamic profiles of the vehicle are extracted. The results demonstrate that the normal force mainly originates from the asymmetric pressure distribution on the cylinder part of the vehicle, and the pitching moment from the asymmetry on the head and the tail. Concerning the horizontal displacement of the gravity center and the pitching angle, the magnitudes are entwined with the height difference between the crest and trough that the vehicle encounters, while the directions with the stage of the crest/trough transition.

The flow regulator is the key component to realize the thrust regulation of liquid propellant rocket engine. The dynamic model of the flow regulator is established according to the structure and working principle of the flow regulator of a hydrogen-oxygen engine, and the simulation calculation model of the flow regulator is established by using AMESim software. The simulation work is carried out by using the simulation model of the flow regulator: calculating the flow characteristics of the regulator under different working conditions, verifying the steady-flow characteristics of the regulator, simulating and analyzing the dynamic characteristics of the regulator, and analyzing the influence of the structural parameters on the dynamic characteristics of the regulator. The simulation results reveal the flow and dynamic characteristics of the flow regulator, and provide a direction for the improvement and optimization of the flow regulator.

The tilting of the rotor of constant speed hydraulic motor driven by high pressure kerosene (hydraulic motor for short) is introduced, and the tilting mechanisms are analyzed. According to the causes, the tilting phenomenon is grouped into initiative tilting and passive tilting. The research on initiative capsizing is carried out emphatically, the mathematical expression is derived based on the mechanics analyzing of the rotor and pistons, and the dimensionless tilting safety factor is introduced to quantify the tilting risk. The causes of passive capsizing are analyzed, and the corresponding solutions are proposed. The initiative tilting and passive tilting should be avoided during the product designing process.

The reusable launch vehicle based on liquid oxygen methane engine has excellent performance in reuse and maintenance, and is easier to achieve low cost. Countries around the world are accelerating relevant research and engineering development. Typical representatives include the Vulcan launch vehicle of the United States, and the ZhuQue-2 launch vehicle of LandSpace. The technical characteristics and technical challenges of the reusable launch vehicle based on liquid oxygen methane engine are analyzed. The following key research contents are proposed, including the overall design and evaluation of reuse, GNC technology for ascent and reentry and return landing, large-scale lightweight structure and manufacturing technology, reuse of LOX engine, health prediction management and reuse operation and maintenance technology, reuse thermal protection technology etc. It will lay a foundation for further development of liquid oxygen methane reusable launch vehicle.

In order to better and faster calculate nozzle performance, a program for calculating the chemical dynamic flow field of two dimensional nozzles is developed by using the method of characteristic and boundary layer correction. The nozzle field corresponding to different for a liquid oxymethane engine, and the influence of different design parameters on nozzle efficiency are studied, the design parameters include thrust, chamber pressure, nozzle area ratio and nozzle outlet angle, etc. Geometric loss, boundary layer loss and chemical dynamic loss are considered in the calculation of nozzle efficiency. The results show that the program can obtain the number important for engineer quickly and accurately, improve the simulation efficiency greatly, and can be used to optimize the nozzle contour.

The matching design of thrust and drag is the core issue in the design of air-breathing vehicles. In order to obtain the drag trait of the inlet and reduce the interior drag, and then improve the overall performance of the air-breathing vehicles, a study on the cold-flow drag trait of a supersonic, twin-duct inlet is conducted with a CFD method. By comparing the flow characteristics and drag trait of the inlets with different length, turning angle, divergence ratio of the curved ducts, drag allocation proportion of different parts of the inlet is acquired and effects of the geometric parameters on the flow structure and drag are attained. Results indicate that a flow separation will probably generate in the curved duct of a twin-duct inlet at a cold-flow condition, which results in a large loss of the flow. It is noted that the drag of the curved duct accounts for majority of the entire inlet when there is no spilled flow. The drag of the curved duct can be reduced by decreasing the turning angle or increasing the divergence ratio of the curved duct. However, due to the interrelationship between the curved ducts' length and turning radius, the drag of the curved duct firstly reduces and then turns to rising with the increment of the curved ducts' length at a fixed design condition.

In order to obtain the load-bearing characteristics of large diameter bolt under typical connection structure, ground test research on the basis of finite element analysis is carried out, which obtains the axial force and additional bending moment of large diameter bolt and revealsits failure mechanism. Analysis and test show that the additional bending moment is an important factor affecting the load-bearing capacity of large diameter bolts. After considering the additional bending moment, the equivalent axial force is several times of the initial axial force, which must be paid attention to in the design work. The formula for calculating the strength of large diameter bolt considering the influence of additional bending moment is proposed, which improves the accuracy. In addition, the method of reducing the additional bending moment of large diameter bolt is studied, and the direction of structural optimization is pointed out.