Two kinds of carbon doped particles, graphene and toner, were used to directionally modify solid propellant. The influence of different doping ratios and working conditions on the divergence angle of the modified propellant was compared and analyzed by high-speed photography technology and a self-built beam divergence angle measurement system, so as to determine the optimal doping ratios and working conditions of the doped particles. It is found that the optimal doping ratio of graphene and toner is 7%, and the beam divergence angle of graphene is smaller, and the response time of generating stable plasma flow is shorter. At the same time, graphene is more suitable for the working conditions under the small laser energy supply, and toner is more suitable for the working conditions under the large laser energy supply.

The electrode structures in ignition devices for Electrically Controlled Solid Propellants (ECSP) can be classified into fixed and movable types. In movable electrode structures, springs are typically used to push the electrodes and the propellant. The effects of spring pressure on the ignition and combustion of propellants have not yet been studied. In this paper, a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate (HAN)-ECSP. The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa. When the spring pressure increased from 5.1 kPa to 20.4 kPa, the propellant resistance decreased from 56.8 Ω to 36.8 Ω. Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage. Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant, increase the electrification current, and thus reduce the initial ignition delay time of the propellant. When the spring pressure is 20.4 kPa, the squeezing speed of the propellant is too fast, making it difficult for the propellant to be adequately heated at the electrode interface, which is unfavorable for ignition. Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate, hindering the mixing and diffusion of hot gases during the second ignition process, preventing the gaseous flame of the propellant. When the spring pressure is 5.1 kPa, improving the working voltage can enhance the repeated ignition characteristics of the propellant.

Fault diagnosis is one of the key technologies to ensure the safety of liquid rocket engines. The model-based diagnostic methods are limited by the irreconcilable contradiction between diagnostic accuracy and model accuracy, while data-driven diagnostic methods, typified by signal processing techniques, rely heavily on expert domain knowledge. With the rapid development of artificial intelligence and big data, the data-driven intelligent fault diagnosis methods have received extensive attention and achieved great success in a great variety of engineering applications. Therefore, the application modes of the data-driven intelligent fault diagnosis methods in liquid rocket engines was reviewed from the perspectives of model structures and feature engineering of machine learning. The three major challenges faced by the the data-driven intelligent fault diagnosis methods in the practical health monitoring application of liquid rocket engines were further analyzed, and the corresponding solutions based on research achievements of our team were presented, respectively. Finally, review conclusions and future works of the data-driven intelligent fault diagnosis technology were proposed to inspire further exploration in this field.

The Atmosphere-Breathing Electric Propulsion（ABEP）technology can capture the rarefied atmosphere as the propellant for electric thrusters, potentially meeting the thrust requirements of Ultra-Low Earth Orbit（ULEO）satellites during operation without carrying any propellant from the ground. This paper designs a RadioFrequency（RF）plasma thruster through adding a nozzle and an enhanced magnetic field based on the Inductively Coupled Plasma（ICP）source. The main atmospheric components in the ULEO are nitrogen and atomic oxygen. Given the low ionization energy of atomic oxygen and its difficulty in storage and use under ground conditions, experiments were conducted on the thruster using nitrogen as the propellant with different gas flows, RF powers, and magnetic field settings. Results indicate that the use of the enhanced magnetic field can effectively improve the thrust and specific impulse of the thruster, and achieve full compensation for the sparse atmospheric drag within a certain orbital range, thus providing an effective approach for the development and application of ABEP systems.

The plume divergence angle is an important reference index for evaluating the thrust efficiency and propellant utilization of space propulsion systems. However, the characteristics of the dynamic variation of plume divergence angle over time cannot be measured using current methods. This paper utilizes high-speed photography and image processing methods to develop a strategy that can give a quick, non-destructive and real-time detection of the divergence angle. Effectiveness of the strategy is verified, and the characteristics of plume divergence angles of different laser-controlled solid propellants were further analyzed and fitted. The experimental results indicate that graphene could effectively reduce the divergence angle, while oxide-doped samples had larger divergence angles than alloy-doped and carbon-doped samples.