To control the position of the windward side along the vehicle for reducing the impact of harsh re-entry force and thermal environment on the vehicle, an active continuous roll control method based on the aerodynamic coefficient fitting model is proposed. Firstly, an aerodynamic coefficient fitting model combining quadratic term and negative exponential term model is established, and the aerodynamic coefficients are fitted using the least squares method. Secondly, based on the coordinate system transformation relationship, the windward angle model and the windward error angle model are proposed to describe the trajectory of the windward side along the cone of the vehicle. Then, based on the BTT/STT composite control method, linear roll control commands are designed, and the effect of different roll control commands on the flight process is compared and analyzed. Furthermore, nonlinear rolling control commands are created based on the loads to ensure that the roll rate is consistent with the trend of the loads. Finally, the proposed roll control commands are verified to generate excellent roll control effect through six degrees of freedom simulation, and can make the windward side evenly distributed along the vehicle. The standard deviation of the load on each meridian of the vehicle in rolling condition is 20% of that without rolling.

Hydrogen-oxygen mixtures are widely used as aerospace propellant. Their thermodynamic properties, transport properties and chemical reaction processes are far more complex than pure air, and it is more difficult to analyze and predict their flow process. The self-developed device-detonation tunnel is used to provide high temperature hydrogen-oxygen combustion gas. Combined with CFD, the flow and aerodynamic heating characteristics of air and combustion gas under the same total temperature and total pressure are analyzed. It is found that, when flowing in the nozzle, the combustion gas has higher temperature, speed and smaller Mach number; the standoff distance and stagnation pressure of the combustion gas are smaller than air; the skin friction and wall heat flux are greater than air. Active chemical reactions in combustion gas make aerodynamic heating more serious.

The nodes of the unmanned aircraft are fast maneuvering and confronting fiercely in the complex environment. There are bad conditions such as position change and link interference suppression. The robust routing technology adapted to wireless network is studied in order to solve the problem of network resource management caused by the frequent change of wireless network topology and the sharp increase of management and control cost, and realize the goal of tenacious, timely and accurate service carrying of wireless communication service in the specific environment. A lightweight hybrid routing scheme with layered management and control is constructed, and topology awareness and fault detection technologies are used to detect network changes quickly and accurately. The damaged residual network is quickly optimized scheduling and compensation through layered route construction, intra-segment route repair and inter-segment route repair, and the communication service capability of the damaged network is improved.

Aiming at the problem of difficulty in quickly and accurately estimating the pose of non-cooperative structures of satellites during the operation of space robotic arms, a neural radiation field based method for estimating and tracking the pose of non-cooperative key structures of satellites is proposed. This method first obtains the scene point cloud online through an RGBD camera, segments the point cloud to obtain satellite key structures, and then uses neural radiation fields to automatically establish a three-dimensional model of the key structures. Finally, based on the initial pose generation network and pose evaluation network, accurate pose estimation is obtained. An experimental platform consisting of an RGBD depth camera, a robotic arm, and a satellite model is constructed to conduct pose estimation experiments on key structures of satellites with different poses. The experimental results show that the algorithm proposed can automatically construct a 3D model of non-cooperative targets online without the need for human preparation of target data in advance. At the same time, it can effectively deal with target object occlusion and motion situations, thus achieving true non cooperative target pose estimation and tracking in spatial operations.

Composite materials used in engineering design often exhibit different properties in tension and compression in addition to anisotropy. The tensile and compressive anisotropy of constitutive behavior can affect the stress and strain distribution of composite structures under operating conditions, further consideration of the difference between tension strength and compression strength may have an impact on the strength analysis results of the structure. This article takes the carbon-carbon composite material air rudder shaft as the research object, implements secondary development through ABAQUS' USDFLD interface, compares and analyzes the changes in rudder shaft stress before and after considering tensile and compressive anisotropy. Then, considering the tensile, compressive and in-plane shear strength of the material, corresponding stiffness reduction models are introduced to analyze the failure process of the rudder shaft under bending and shear loads. The analysis results indicate that different properties in tension and compression will have a significant impact on the stress distribution of composite structures, and this analysis method can achieve more accurate simulation of the failure process of the rudder shaft.

As artificial intelligence technology developing rapidly, the intelligence level of unmanned systems is much increasing. Specially, intelligent reconnaissance technology is more mature and widely used. To solve the above problems, an adversarial patch attack based camouflage and deception method is proposed. Convolutional neural network is used to build a classifier as the attack object, and a novel patch generation method and loss function are designed to attack target samples, which effectively maps the attacked target samples to the specified wrong target category. A directed evaluation method and wealthy experiments are provided to verify the advancement and effectiveness of this method.

The stability of lubricating grease performances is a significant factor that restricts the long-term storage reliability of aerospace electro-mechanical servo actuators. The rheological properties of lubricating grease can directly affect the transition characteristics of servo actuators. Accelerated degradation test at high temperature stresses is designed and carried out. Three grades of lubricating grease with different base oil systems, including soap based, non-soap based and mixed lubricating grease are investigated for their theological properties. The rheological properties of different lubricating grease changed in thermal aging time and temperature stress are analyzed. It is found that the viscosity of lubrication dose not change unidirectionally with the increase of thermal aging time. In addition, the rheological properties of mixed lubricating grease at high temperature is better than that of soap based lubricating grease and non-soap based lubricating grease, which is valuable to evaluate the properties of lubricating grease during long-term storage of aerospace electromechanical servo system.

With the increasing frequency of human space activities, there are surviving debris of re-entry spacecraft and debris that impact the Earth's surface, causing typical damage cases and affecting the future technological development of spacecraft. Firstly typical re-entry damage cases and disposal methods of foreign spacecraft that have attracted significant social attention are analyzeds. Secondly the main international norms and standards for re-entry casualty risk are introduced. Then those assessment methods of re-entry casualty risk are studied together with re-entry risk analysis tools of NASA and ESA. Finally it's looked forward to the furture development and existing problems of major space powers in the technical directions of active deorbit, assisted deorbit, large-scale reentry, and reusable spacecraft. Research shows that although the re-entry casualty risk of spacecraft and debris is still difficult to predicte very accurately, it is expected to be moderately controlled by the design of risk-reduction measures along with technological development.

To address the issue of harmonic concentration near fixed switching frequencies caused by high-speed switching actions in traditional PWM strategy, the random modulation strategies in the PMSM servo drive system are studied. On the basis of conventional RSF-PWM strategy, DRM-PWM strategy enhances EMC by introducing randomization of the zero-vector action time. However, this strategy struggles to balance EMI suppression effectiveness with system control performance. Subsequently, MARSF-SVPWM strategy is investigated, with a focus on comparing and analyzing the two modulation strategies. Compared to DRM-PWM strategy, MARSF-SVPWM strategy maintains overall spread spectrum range and average switching frequency while narrowing the distribution range of differences between adjacent switching frequencies, thereby further reducing harmonic peaks. Simulation and experimental results demonstrate that MARSF-SVPWM strategy achieves better harmonic dispersion performance compared to DRM-PWM, and maintains a lower impact on system control performance, optimizing the EMI suppression effect.

For higher reliability, higher efficiency and easier maintenance, three TVC actuators for a hydrolox launch vehicle block are studied comparatively, in aspects of designs, models and testing performances, namely, a Servo-Valve Controlled Electro-Hydraulic Actuator (SHA), an Electro-Mechanical Actuator (EMA) and an Electro-Hydrostatic Actuator (EHA), each outputting a peak power of 3 kW. A fully packaged duplex EHA design is proposed, lightweight and compact by means of innovating indepth integrations in the actuator, Electro-Hydrostatic Module (EHM), Servo Motor Pumps (SMPs) and Electronic Control Units (ECUs). The weight of a TVC system with four EHAs is 85 kg, reduced by 37%, compared to the SHA counterpart of 135 kg. The dynamic capability of three TVC actuators is almost on a par, with the first-order frequency bandwidth of greater than 30 rad/s. As to the overall efficiency of energy conversion, it is one order of magnitude higher for an EMA or an EHA than a SHA. In an operation profile on ground with a duration of 1 200 s, the efficiency is lowest for an SHA, less than 1%, and heated quickly, with the temperature reaching over 100 ℃ at the hydraulic pump. In contrast, as to the EMA and EHA,the efficiency is remarkably upgraded to over 20%, with the temperature only slightly increasing by 5 ℃ at the pump or the electric motor. It demonstrates that an EHA embodies both the heavy loading, high reliability of a SHA, and the high efficiency, good maintenance of an EMA, at the same time overcoming the weak points in dynamics, power density, oil sealing, etc., providing an intriguing option for highly reliable and secure launch vehicles. The EHA has finished its maiden flight as the first one for launch vehicles.