The maiden flight of LM-8 performed perfectly on December 22, 2020. The design concept of modularization, seriation and combination has been perfectly exhibited in LM-8. The four main technical innovations, including rapid integrated design based on modularization, engine thrust regulation, modal parameters acquisition technology based on numerical simulation, and flight load control, were verified during the maiden flight. LM-8 is now positioned to be the main force in China’s medium launch vehicles for commercial launch. In the future, the mission adaptability of LM-8 will be improved to provide efficient and low-cost launch services. In addition, new technologies to allow repeated use and autonomous flight will be validated.

Throttling of large-thrust liquid rocket engines, which can improve mission adaptability of a carrier rocket, reduce risk and facilitate rocket recovery, is a key technology for current and future space development. This paper summarizes the state of the art and trends of throttling technology for large-thrust liquid rocket engines at home and abroad. According to the working principles of propulsion for rocket engines, throttling the propellant flow rate is a major way of adjusting thrust, and regulation devices along with adjustable injectors are primary measures of throttling propellant flow rates. This paper clarifies the working principles of typical regulation devices and adjustable injectors, introduces the regulation schemes of typical large-thrust engines such as YF-100, RD-170, and SSME, and summarizes the main characteristics of current throttleable large-thrust engines. Finally, critical technologies and development trends of throttling are discussed, including combustion stability and reliable cooling of thrust chambers at low thrust levels, turbopump stability, and stable regulation and precise control in a wide range of operating conditions.

This paper introduces the autonomous control technologies for a new generation launch vehicle for guidance and attitude control. Based on the iterative guidance mode (IGM) of Long March launch vehicles, the autonomous compensation IGM (ACIGM) for the terminal attitude deviation during the coasting phase is proposed. Considering the characteristics of large static instability and weak bearing capacity, the attitude control technology based on active disturbance rejection control (ADRC) and a control method based on an accelerometer are proposed. Targeting at non-fatal failures that may occur during flights, autonomous guidance reconstruction technology, nozzle fault diagnosis and reconstruction technology in the coasting phase are studied. Some of the autonomous control technologies proposed in this paper have achieved good control results as seen through flight verification.

To meet the application requirements for a Ka-band space-based TT&C terminal for a launch vehicle, this paper proposes the implementation scheme of a space-based TT&C terminal, analyzes and solves the miniaturized design of equipment and the key technology for high-efficiency heat dissipation. The phased array antenna test shows that without external heat dissipation measures, the phased array antenna can work for a long time to meet the working requirements of launch vehicle, which has been verified in the LM-8 mission, and has wide engineering application prospects.

LM-8 inherited mature modules from other launch vehicles, adapting the overall design through the combination of engine throttling, wind compensation and load relief control, so as to reduce the aerodynamic load during flight. This paper proposes a rapid evaluation method for load relief performance, which takes launch vehicle’s characteristics, wind field, control parameters, aerodynamic deviation and structure deviation into consideration, and provides a quick estimation method for load relief performance. The load relief performance of the LM-8 launch vehicle estimated by this method achieved 10%−20% in pitch and 20%−40% in yaw. The specific results are related to parameter deviation, the altitude of wind shear and the relationship between wind direction and trajectory angle. Simulation results for a typical case with six degrees of dynamic freedom of flight proves that the comprehensive load relief performance would be between 14% to 34%, which is in line with the aforementioned method. In addition, simulation results indicate that the more severe the wind shear is, the better performance of load relief can be achieved.

LM-8 was China’s first launch vehicle which designed its dynamic characteristics without carrying out a fullscale modal test, and then in the absence of test data to establish the dynamic model. The issue was, how to accurately obtain the mode data of LM-8 with numerical simulations which directly affects the control reliability of flight. In this paper, various approaches to obtain the dynamic characteristics of LM-8 are described from the perspective of refined dynamic modeling and simulating, mode slope prediction, vertical modal test, etc. The numerical simulations were found to be in good agreement with the experimental data, and satisfied the requirements for the engineering application, which effectively supported the successful maiden flight mission of LM-8.

An electro-hydraulic actuator for the thrust vector control (TVC) of a throttlable kerolox rocket engine is introduced in this paper. The creative feature is an integrated hydraulic power drive unit, where a constant speed kerosene motor is used to draw high pressure kerosene from the engine and to drive a constant pressure variable displacement piston pump, acting as the power supply for the actuator. Its operational mechanism, to accommodate the varying pressure from the turbo-pump of a throttling engine, lies in a pressure-reducing flow regulator inserted at the motor inlet. Another key point is that the displacement of the motor is reasonably bigger than the pump so that a sufficiently wide range of pressures can be adapted. Modeling analysis and flight test results were well matched, which show the outstanding performance of this novel type actuator.

The strength of the connection structure has always been a key issue in the structural design of a launch vehicle. In this paper, the finite element analysis method is used for the strength of typical connection structures of a new launch vehicle. The research scope includes the inter-stage connection structure and the bundle connection structure. Aiming at establishing the strength of these two connection structures under flight conditions, we built a refined finite element model, simulated the bolt tensile test and obtained a calculation criteria, and carried out finite element analysis of the connection structures under flight conditions. As a result, we not only established the analysis and evaluation method of the connection structures based on the refined finite element modeling analysis, but also provided a fast numerical simulation design method for the development of the launch vehicle’s connection structures, which greatly improved the design efficiency and reduced the design risk.

Aiming at the low-frequency pressure fluctuation phenomena in certain liquid oxygen delivery systems during dual engine operation, a numerical study on the intrinsic frequency of the liquid oxygen delivery system was conducted by adopting an acoustic unit in Abaqus. Factors such as condensation characteristics of the oxygen-enriched gas gas in the liquid oxygen’s pipeline between pumps, flexibility of the accumulator, and cavitation flexibility of the engine were considered in the simulation models. The simulation results show that the second order frequency of the liquid oxygen delivery system is 8.77 Hz, and the phase difference of the corresponding acoustic modal is 180°, which is the liquid circuit frequency of the small loop between the two branches of the tee. This is consistent with the low-frequency fluctuation phenomenon during flight. Moreover, the simulation results were consistent with the liquid circuit frequency solved via the transfer matrix, which also verified the effectiveness of the frequency analysis method based on acoustic theory.

A launch pad is an important part of the launch vehicle system. It bears the weight of launch vehicles and payloads, and is burnt due to the high-temperature and high-pressure gas flow during launch. This study analyzes the development of launch pads in the world, reviews a reconfigurable mobile launch pad for multiple launchers, then proposes common points and development trends of future launch pads in the world.