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.

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.

Satellite Internet is becoming the new battlefield of global competition. With the development of Chinese satellite network and G60 satellite chain, there is a huge market space for commercial launch of launch vehicles. Under the commercial application, the design, production and launch of Chinese launch vehicle show the trend from fixed launch site, customized research and months of preparation time to random launch site, mass production and several days of preparation time. A heterogeneous network and SDN management based wireless test and launch control system architecture universal for land and sea is proposed, and the integrated design of mobile cabin based test and launch control system is presented. Aiming at the requirements of rapid response, economic efficiency, high reliability and strong environmental adaptability of commercial aerospace, a fast workflow method based on system decoupling, test integration and automatic interpretation is proposed, and a system integration method based on assisting business with commercial general hardware procurement and special software development, improvement of system reliability replacing equipment reliability and ground integrated protection replacing individual adaptation is proposed to achieve a balance between economy and reliability. On this basis, the trend of test and launch technology is introduced from five aspects which are the integration of vehicle functions and ground functions, the test and launch technology with remote assistance, low-cost test and launch mode, test and launch control for recyclable rocket, and application of advanced technology

In response to the complex and time-consuming process of adjusting the center of gravity of aircraft, k-means clustering method is used to cluster the historical data of aircraft counterweight. Based on the clustering results of samples, the standard counterweight of aircraft under different samples is calculated. Then, the centroid offset of aircraft with standard counterweight is calculated through simulated assembly, and a series of statistical data are obtained. After that, the comprehensive evaluation method based on entropy weight is used to compare the results of centroid adjustment, and the optimal standard counterweight of aircraft is selected, thus simplifying the adjustment process of aircraft centroid and greatly improving the producting efficiency of aircraft.

Aiming at the characteristics of multiple hypersonic vehicles cooperative combat, a time cooperative reentry guidance scheme based on deep deterministic policy gradient and linear quadratic regulator (DDPG-LQR) is proposed. Firstly, the sequential convex programming method is used to generate the time cooperative reentry trajectory satisfying multiple constraints and its corresponding steady-state control quantity. The Radau pseudospectral method is used to discretize the motion equations to improve the discretization accuracy of trajectory optimization. Secondly, the linear quadratic regulator (LQR) is used to track the time cooperative reentry trajectory. In order to improve the cooperative guidance accuracy and guidance effect, the deep deterministic policy gradient (DDPG) is used to optimize the weight matrix coefficients of the LQR online. In the DDPG algorithm, the optimization performance of the algorithm is improved by introducing an appropriate reward function. The simulation results show that the cooperative guidance scheme proposed has better cooperative guidance effect and guidance accuracy than the traditional LQR controller in the case of initial state error and uncertainty.

When the design input is limited during the initial stage of scheme argumentation, in order to solve the problem of how to conduct control capability analysis quickly and effectively, the adaptability of traditional control capability analysis method is analyzed. A set of controllability analytical method for reentrant launch vehicles is researched by dynamic modeling and original method improving. And under the premise of limited control capability, the constraint conditions for allowable flight conditions is limited preliminary in order to quickly locate and feedback the closure of the overall unit control capability.

Vibration testing is one of the key methods for verifying the structural performance of solid rocket engines. It involves securing the test piece on the vibration table with fixtures to ensure accurate transmission of vibration loads, preventing resonance or tailing phenomena, which are the desired outcomes of vibration testing for solid rocket engines. This research focuses on a certain model solid rocket engine shell vibration testing fixture clamping methods and proposes a vibration testing fixture optimization method based on a proportionality coefficient. A simulation model of the solid rocket engine shell and the fixtures is established. Modal analysis and harmonic response analysis are carried out for the structure under different proportionality coefficients of the clamping methods. The vibration testing of the shell is conducted on a ${90}\mathrm{{kN}}$ electromagnetic vibration table. The test results indicate that a proportionality coefficient of 0.9 is the optimal clamping method for the vibration testing of the solid rocket engine shell with a slenderness ratio of 2.6, which is generally consistent with the simulation analysis results. This clamping optimization method has practical reference value for vibration testing of solid rocket engine shells.

Based on the AMSAA model, which is centered on the failure data of the same or similar products collected during the R&D stage, the principle of minimization of discrete coefficients is innovatively introduced as an optimization criterion, which is used to guide the selection of goodness-of-fit test statistics. After integrating multivariate information such as mean and variance, a new algorithm for solving the time-environmental folding coefficients is constructed, aiming at effectively folding the original failure data and then accurately estimating various parameters of the model. By solving the resulting folding coefficients, the one-sided lower confidence limits of MTBF (Mean Time Between Failure) are calculated one by one for each of the 10 different confidence settings when the product design is being molded. Example studies show that when the confidence interval is between 0.9 and 0.99, the method consistently produces better results than the existing literature regardless of the same confidence level, i.e., the accuracy of the method is significantly improved for predicting the reliability growth of aerospace products. In addition, the values of the time-environment folding coefficients solved by the improved method do not change at different confidence levels, i. e., the quantitative relationship between the environmental stresses and the real environmental stresses for each test item does not change due to the increase in confidence level, which also proves that the improved method is closer to the engineering practice from another perspective.

The engine nozzle is prone to work with a state of over-expansion in a high-pressure underwater environment, which will influence the jet flow field and thrust. Experiments of over-expansion supersonic underwater gas jets at different co-flow velocities are conducted using a circulating water tunnel, various forms of wake cavity and their corresponding thrust time-frequency characteristics are analyzed. It is shown that at low velocities, the over-expanded gas jet is difficult to form a cavity attached to the wake or a pulsating foam-type wake cavity. Under such flow conditions, the vehicle experiences pronounced thrust oscillations with a rich frequency spectrum (36 to ${743}\mathrm{\;{Hz}}$). As the Froude number at the co-flow velocity increases to ${Fr}= {8.57}$, the jet eventually forms an intact tail cavity, at which point the amplitude of the thrust oscillations decreases significantly and the mean thrust value increases significantly. The internal gas reflux phenomenon in the jet-induced tail cavity is also directly observed, and the observed reflux velocity at ${Fr}= {8.57}$ is about ${1.13}\mathrm{\;m}/\mathrm{s}$.

In response to the low detectability requirements of micro radar detectors, a hybrid polarization-frequency selective rasorber (PFSR) is proposed. Firstly, based on the equivalent circuit analysis method derived from transmission line theory, the mechanism for achieving wave absorption and transmission compatibility is explored. Furthermore, by employing a bilaterally asymmetric loading approach with resistive sheet, the polarization-selective functionality of the transmission window is realized. Finally, through a hybrid design of resistive sheet, the challenge of achieving wideband absorption and transmission compatibility is addressed. Simulation results indicate that when TE waves are incident, this structure exhibits integrated functionalities with wave transmission in the frequency range of 6.8 to ${7.8}\mathrm{{GHz}}$ and low scattering across 2.2 to${18.0}\mathrm{{GHz}}$. In contrast, when TM waves are incident, it demonstrates an effective wave-absorbing capability with low scattering in the frequency range of 3.2 to 18.0 GHz. This design offers a viable solution for enhancing wideband low detectability in flight communication platforms such as satellites.