A long-life and high-stability grease is developed to meet the demand of long-life lubrication condition with storage requirement. The physical and chemical properties,biodegradability, bearing life and rheology of the grease are studied. The results show that compared with the commercial grease, long-life and high-stability grease has lower evaporation loss at high temperature and lower oil separation ratio, which shows that it has better volatility and colloidal stability. The wear scar diameter of SRV test is smaller, and the life of wheel bearing and FE9 is longer, indicating that it has better anti-wear performance, lubrication performance and oxidation stability. The cumulative biodegradation rate in 28 days is 1.82%, which is much lower than 29.19% of the commercial grease. The rheological tests show that it has better structural stability. The developed long-life and high-stability grease has excellent comprehensive performance and can be used in the long-life application environment with long-term storage requirements and harsh working conditions.

To investigate the effects of grease degradation induced by long-term storage on the control characteristics of servo systems, the viscosity properties of the grease during storage are analyzed according to the results from the high-temperature accelerated storage test. Subsequently, the friction of the roller screw transmission is modeled to investigate the influence of lubrication degradation on the friction characteristics of servo system. Eventually, the friction models for various lubrication conditions are integrated into the servo system control simulation model to assess the impact of lubrication degradation on its performance characteristics. The obtained result is that the viscosity properties do not exhibit a clear correlation with the accelerated storage time. Selecting the degradation grease with high viscosity as the research subject, analysis indicates that the lubrication causes the increase of friction torques, the attenuation in amplitude and phase hysteresis in mid-high frequency range in servo system control characteristics. Besides, the attenuation and hysteresis aggravate as the load increases.

Jet-deflector servo-valve is known for high resistance to contamination and is widely used in aerospace where reliability is critical. However, the internal structure of jet-deflector device is very complex which makes it more challenging to a performance indication. When Computational Fluid Dynamics is introduced into an analysis of a jet-deflector servo valve, the dispersion of experimental data is always intolerable for a precise verification because of manufacturing or assembling accuracy. In this research, a distribution of experimental results is presented. After a comparison of different turbulence models, the low Reynolds number k-ε model shows more precision in pressure characteristic analysis of jet-deflector device.

To address the issues of penetration and precision attacking for air-to-air missiles, an analytical solution for the miss distance of a non-zero-order guidance system is derived. The solution is then extended to advanced guidance laws beyond proportional navigation guidance. Based on these results, the effectiveness of evasion under different maneuvering strategies is analyzed which theoretically explaining the typical characteristics of miss distances in step and serpentine maneuvers and factors influencing the optimal maneuvering strategy are studied. Through reasonable adjustment of maneuver timing and direction, the effectiveness of evasion is improved. Furthermore, considering the integration of penetration and attacking through intelligent guidance laws, an adaptive-stepsize sparsified sampling prior model theory infusion remedial training agent learning (ASTRAL) is introduced. Simulation results show that the missile agent trained with the ASTRAL can effectively evade defender while maintaining its attacking capability during penetration. In addition, the generated guidance law demonstrates good engineering feasibility.

For Falcon 9 rocket launch missions in 2024 and before, a reuse indicator system has been initially established. Statistical analysis is conducted in the time dimension and status dimension, and the development rules of Falcon 9 rocket one-stage reuse technology are initially obtained. By the analysis of the rules, the development and evolution process of Falcon 9 rocket recovery and reuse technology is divided into three stages. Finally, a preliminary prediction is made on the development of China's reusable rockets.

In response to the problems of large deformation, multi-contacts, and time-varying folding stiffness during the deployment of flexible folding spacecraft, research has been conducted on the dynamic modeling methods of the deployment process of large-flexibility folding structures. Based on the folding method of such large-flexibility structures, a typical folding model is simplified and extracted, and a three-dimensional finite-segment discrete model suitable for the deployment of large-flexibility folding structures is established using the finite segment method. Utilizing vector mechanics, a mechanical model of the connecting forces between adjacent units is derived from the Newton-Euler equations, and the stiffness matrix of the connection forces is provided. Nonlinear equivalent contact spring damping and a continuous friction coefficient Coulomb friction force model are introduced to simulate the contact and friction states between units, ensuring the stability and efficiency of the solution. A time-varying nonlinear elastic connection model at the crease is proposed, along with a parameter identification method for bending stiffness. Using ADAMS software, dynamic simulations of deployment are conducted for typical folding models under four working conditions, and corresponding deployment experiments are designed. The comparison between the two results shows that the change in tensile force during the deployment process of typical folding models matches well, validating the feasibility and accuracy of dynamic modeling for such structures, and laying the foundation for subsequent simulations of the overall structure's unfolding.

In the process of rocket engine development, the test work is very important, and the main result of the test is a large number of data measured in the test, so the measurement is very important. The rocket engine has a harsh working environment, high test cost, high test risk, many measuring points, high precision and large scale, and requires wide measuring range and frequency to ensure high accuracy of steady-state parameter measurement and no distortion of transient process measurement. Therefore, special requirements are also proposed for the test system. In order to meet the new requirements of rocket engine test, a digital filter is proposed for optimizing the performance of rocket engine test system, which can optimize the dynamic characteristics of the test system on the basis of not changing the original equipment hardware, and meet the requirements of high accuracy of steady-state parameters an no distortion of transient parameters. The experimental results show that the proposed method can obviously improve the performance of rocket engine test system.

To ensure the reliability of dynamic seal performance of low temperature valve in liquid rocket engine, the sealing pressure and performance of a new type of labyrinth packing dynamic seal structure are simulated and tested. Firstly, the structure of traditional packing dynamic seal is optimized, and a new PTFE-Graphite-Metal labyrinth composite seal is designed. Then, based on the thermal stress coupling method, the influence of the working condition on the dynamic sealing performance is analyzed, and two empirical models for PTFE and Graphite are proposed to represent the dependence of contact stress on both the loading pressure and temperature. Finally, the sealing performance of the new labyrinth dynamic seal is tested at room and low temperature. The results show that the new labyrinth dynamic seal can achieve good sealing performance at room and low temperature, which is consistent with the simulation results.

This study investigates the combustion performance of gas-oxygen and gas-methane pintle injectors, which discusses the influence of pintle injector structure design parameters and thrust chamber combustion design parameters on the combustion performance. Theoretical analysis is carried out by numerical simulation and other methods. The simulation results show that the oxidizer central pintle injector has a higher combustion performance. A larger angle of the pintle head and a smaller distance of the intermediate sleeve have a higher combustion performance. A smaller pintle head radius can significantly play a role in cooling the pintle head, but there is a certain loss of combustion performance. When the speed ratio is about 1.1, the combustion performance is higher, and the temperature of the pintle head is lower. When the mixing ratio of oxygen and methane is around 3, the combustion performance is higher.

As the key interface between launch vehicle and ground support equipment, the cryogenic connector is used for filling and venting of cryogenic propellant, and it falls off before or after launch. Affected by the high temperature and high humidity environment of Hainan launch site, the low temperature surface of the rocket-ground interface is more prone to frost and ice after long-time filling, which hinders the action of the separation and increases the resistance of the connector to fall off. Quality problems affecting the launch process occurred in historical missions. An improved scheme for the rocket-ground interface is proposed, which can reduce or avoid icing at the unlocking part and reduce unlocking resistance through thermal design optimization.