Abstract:As the main module of space station， the Mengtian lab module mainly provides support for in-orbit tests of various inner and outer payloads. It has the unique capabilities of supporting payload inbound and outbound transportation and micro-satellite and cubesat releasement， and can promote the comprehensive application efficiency of space station. After launching into orbit on October 31， 2022， the Mengtian lab module finished the initial state setting， in-orbit tests， and several times of payload inbound and outbound transportation missions. All functions of the Mengtian lab module are normal， and all indicators meet the requirements. In this paper， the development process of the Mengtian lab module is reviewed. The overall design is overviewed， the technical characteristics and the innovation points are summarized， and the in-orbit tests and operations are introduced.

Abstract:During the space station development， it is of great significance to obtain accurate dynamic characteristics of the Mengtian lab module， and the dynamic test of the whole spacecraft is an essential large-scale test project. Aiming at the analysis of the dynamic characteristics of the Mengtian lab module， a finite element model of the bolt-flange local connection structure is established， and the relationship between the structural stiffness and the external force is analyzed. The substructure synthesis method was adopted to obtain the main dynamic characteristics of the Mengtian lab module based on the component-level modal test results. The results show that the dynamic characteristics can be predicted accurately when the bolt-flange is equivalent to a bilinear spring. So， through the fine modeling of the connection structure and the substructure method， only the module level modal test is needed for prediction of the dynamics of large spacecraft， which saves the development cost and shorts the development cycle. This practice can provide guidance for the development of space station and other large spacecraft.

Abstract:In order to enhance the China Space Station's ability to support extravehicular loads， improve the cargo entry and exit efficiency of China Space Station， and reduce the number and risk of astronauts' extravehicular activities. The China Space Station Mengtian Lab Module is designed with cargo automatic egress and ingress function. Based on the cargo automatic egress and ingress function， this article introduces the ground test verification and in-orbit test verification of the key sub functions， including cargo transfer function， outer hatch function， air reuse， repressurization and repressurization function. The comparison of experimental verification results between space and earth shows that the design of cargo automatic egress and ingress function is reasonable， the ground verification results are consistent with the in-orbit data， and the product performance is stable. Mengtian Lab Module can enhance the cargo entry and exit efficiency of China Space Station efficiently.

Abstract:The initial orbit is the key criterion for the evaluation of spacecraft into orbit. The fast and accurate calculation of initial orbit can gain time for the emergency life-saving control when the orbit is abnormal. In order to solve the problem that the time and accuracy obtained by the traditional initial orbit calculation method cannot be balanced， a fast initial orbit calculation strategy is designed. The separation time of module and arrow is determined according to the acceleration change rate of the launch vehicle. the real-time orbit sliding batch processing algorithm based on dynamic constraints is used to accumulate the data after ultra-short arc separation for the initial orbit calculation， and the logical optimization of multiple groups of initial orbits determined by various data sources is determined. The simulation data of the Mengtian lab module show that using the designed strategy to calculate the initial orbit can achieve the same accuracy of post-precision orbit determination， the calculation time is controlled within 1 min， and the timeliness is much higher than that obtained by the post-precision orbit determination method.

Abstract:In view of the mission requirements for supporting automatic cargo entry and exit and testing scientific loads in the Mengtian lab module， as well as its configuration characteristics of high mass and large size，combined with the general configuration requirements for the dual-degree-of-freedom solar orientation of the China Space Station，in this paper，the design constraints，design concepts，and technical implementation approaches for the Mengtian lab module are summarized from two aspects，i.e.，general configuration and layout，and the general configuration and layout design status of the Mengtian lab module are introduced.Through the verification means such as simulation analysis，experimental simulation，and in-orbit flight，the design effect is verified，and the general configuration and layout characteristics of the Mengtian lab module are analyzed and summarized，which can provide reference for the general design of similar spacecrafts.

Abstract:The airflow distribution in the sealed cabin of the space station has a significant effect on the safety and comfortableness of astronauts in orbit for a long time. To ensure sufficient air convection inside the sealed cabin， the way of supplying air from the top while returning air from the bottom is usually adopted. In view of the ventilation flow field problem in the activity area of astronauts in the Mengtian lab module， a combination of flow field tests and simulations is usually adopted to analyze the airflow organization in the area. The comfortable speed ratio and blowing feeling are selected as the evaluation indices. The results indicate that the deviation between the test data and the simulation data is within ±15%， and the statistical deviation of the wind speed in the entire area is within ±5%， which shows that the simulation model is effective. The proportion of the comfortable speed in the activity area of astronauts in the Mengtian lab module reaches as high as 92.15%， and the blowing feeling index is less than 40， which meets the requirements of personnel safety and comfortableness. The study can be used as a reference for the ventilation design， test， and simulation of manned spacecrafts.

Abstract:The thermal control fluid loop technology with multiple parallel branches has been widely used in manned spacecraft. Factors such as external heat flux， gravity， and resistance characteristics can affect the flow resistance， and thereby affects the flow distribution and heat dissipation potential， which may cause fluid freezing and loop failure and threaten the spacecraft safety. Therefore， it is urgent to analyze the influence factors affecting the flow distribution. A simplified model is established based on the fluid loop with six parallel branches in the Mengtian lab module， and the effects of the external heat flux， gravity， and resistance characteristics on the flow distribution are studied. The results indicate that the variations of the fluid physical properties caused by the radiation heat dissipation can lead to an uneven flow distribution in each branch， which would be increased with a higher heat dissipation caused by the external heat flux change and gravity. In addition， during the design and operation of the loop， the working medium temperature should be avoided to enter the area of drastic changes in the fluid physical properties， otherwise the flow rate of each branch might be easily affected by the external environmental changes.

Abstract:In view of the characteristics of oxygen sensor and zirconia oxygen sensor， it can be concluded that the sensor will have precision error and measured drifts at the end of its life. Based on the multi-sensor data fusion technology， the measured sensor data with good stability and consistency are selected as the reference values for automatic calibration. Based on the single-point k-factor calibration method， a multi-point k-factor calibration method is proposed. The results show that when the voltage drift reaches 0.1 v， the oxygen partial voltage drift of the conventional calibration method will exceed 2 kPa， but the drift of this method will not exceed 0.5 kPa. Therefore， the calibration method enhances the adaptive range of the oxygen sensor drift， reduces the measurement error and reduces the calibration frequency.

Abstract:With the further advancement of China's space station construction and the Chinese National Manned Space Program，the extravehicular activities of astronauts will become an important means for complex space operations. In order to ensure the feasibility and efficiency of on-orbit space manipulator maintenance missions，it is necessary to carry out simulation analyses and ground test verification for the on-orbit maintenance process and device operation process of the astronauts.An on-orbit space manipulator maintenance mission is a systematic project，including many aspects such as the maintenance process design，the spare part transfer，and the analyses of astronauts' operational space and operational capability. In this paper，a mission planning and verification system for the on-orbit manipulator maintenance missions in the space station is established. The astronaut attainability is verified，the operability of the maintenance process is analyzed，and the safety and maintenance efficiency of the on-orbit manipulator maintenance mission design are evaluated，which will provide a theoretical basis for the extravehicular activity training and implementation of the astronauts.

Abstract:In view of the center distance offset and tilt deviation problems caused by the large size of the gear pair at the transmission end of the large-scale solar-orientated device of the space station， a new involute-circular gear with center distance separability is proposed. The gear has the ability of center distance compensation， and can effectively solve the problem of the center distance deviation of terminal gear transmission. According to the index requirements and constraints of the terminal transmission， the involute-circular gear transmission technology is used in the design， strength calibration， and simulation analysis of the gear pair. Multiple sets of products are designed and multi-round gear pair life tests are carried out under the equal proportion scheme. To verify the center distance compensation ability and feasibility of the new gear， the transmission efficiency is tested， and the gear surface status is observed. The research of this paper lays the foundation for the design of the gear pair of large transmission mechanism， and provides a reference for the development of new involute-circular gear.

Abstract:The space radiator is responsible for dissipating the redundant heat from spacecraft to outside space. It is a key equipment of the thermal control system for spacecraft，especially for manned spacecraft. The currently launched manned spacecrafts all use fluid loop radiators，which should meet the requirements of long lifetime，high reliability，and stability. In this paper，the fluid loop-heat pipe coupled radiator for the China Space Station (CSS) is tested and analyzed，and the expression of the heat rejection capacity of the radiator is concluded. First，the scheme and process of the tests are briefly introduced，and the test results are given. Then，through the analysis of the obtained test data，the relationships between the heat transfer resistance and the heat rejection capacity with the fluid loop parameters and the external heat flux parameters are obtained. Based on the test data，the simulation analysis model of the radiator is improved. The results obtained by the improved model are compared with the test data，and good agreement is achieved. The simulation analysis model can be used to predict and analyze the on-orbit performance of the radiator. This article has certain reference for the design of spacecraft radiator，and can provide data support for spacecraft thermal balance tests and radiator working state settings in orbit.

Abstract:In order to solve the problem that the solar cell wing is difficult to orient to the sun due to the large variation of the incidence angle of the sunlight under different configurations and flight attitudes of the space station，a configuration of split combined double-degree-of-freedom solar-oriented system is proposed.The configuration and flight attitude of the space station are studied，by which the solar-oriented mode to independently operate and separately control the A- and B-axes is determined.The two axes are orthogonally connected through the truss structure.During the single cabin flight of the Mengtian lab module，the A-axis does not move，the B-axis tracks the sun according to the orbital period，and the change of the sunlight incidence angle is compensated by adjusting the attitude of the aircraft. When the combined body flies，the B-axis is used to compensate for the solar altitude angle，and the A-axis drives the B-axis and the solar cell wing to track the sun together according to the orbital period so as to achieve the double-degree-of-freedom orientation to the sun.The in-orbit flight results show that under different module configurations and flight attitudes，the fluctuation amplitude of the power channel output power is reduced from 60% to 7%，and the configuration of split combined double-degree-of-freedom solar-oriented system can adapt to the complex flight conditions of the space station.

Abstract:In view of the lubrication schemes for the moving parts of solar array α rotary joints of the Wentian and Mengtian lab modules， the tribological characteristics of MoS2-， PM6-， and Au-TiN-based solid lubricating films are studied. By atomic oxygen attack tests， the resistance ability of the MoS2-based solid lubricating film against the atomic oxygen irradiation is verified， and the physical characteristics of the PM6-based solid lubricating film with solid-liquid composite lubrication are analyzed. The equivalent real product state life parts are used to carry out vacuum life tests for the lubricating films， and the obtained results verify the feasibility of the long-life lubrication technology. The study is of guidance and reference significance for the subsequent design of long-life spacecrafts.

Abstract:The flexible solar cell wing has been successfully applied in China's Space Station for the first time. It is one of the most complex and difficult mechanical and electrical products in the space station system. As a key component of the flexible solar cell wing system，the mechanism is used to realize the protection of the flexible solar cell wings in the ascent stage andunlock andrelease the flexible solar cell wings in the orbital section. Therefore，the success of the space mission depends heavily on the proper functioning of the restraint release mechanism. Based on the task ，this paper introduces the structure、principle、design、simulation and application in orbit ，and analyzes the technical characteristics and key technologies. The ground verification and in-orbit flight have verified the correctness and rationality of the design for the restraint release mechanism，and provided a novel and reliable solution for the multipoint and large-area repeatable compression and unlocking for the Chinese spacecraft.

Abstract:A semi-rigid riveted structure with large openings is proposed for the payload cabin of the Mengtian lab module on the China Space Station. The integrated design of structural bearing， load engress and ingress，and load test platform is achieved. In view of the effects of factors such as the flight of the ascent stage and the ground lifting load，the numerical simulation method is used to analyze the structural strength iteration， identify the potential weak links of the structure， and carry out targeted local structural tests to verify the weak links. Finally，a static test platform with large openings is designed and built，and the whole cabin static test is implemented. The numerical calculation and test results are in good agreement，verifying the correctness of the design for the payload cabin with large openings. The design methods and verification ideas of the payload cabin structure can provide references for other aircraft structures.

Abstract:According to the structural and mechanical characteristics of large-scale solar-oriented devices，the optimized design is carried by optimizing the force transfer structure and making full use of the designability of fiber reinforced composite materials.In order to ensure the demands of high stiffness and lightweight and overcome the insufficient bearing capacity caused by large opening structure，the main bearing frame products with the weight-to-bearing ratio of only 5.2% are designed for large-scale solar-oriented devices. It has both the function of the spacecraft module section and the function of the mechanism shell. The finite element analysis model is developed by using two strength failure criteria，i.e.，Tsai-Wu and maximum strain.Static tests are performed，and the information such as strain is collected. The obtained data are compared with the finite element analysis results. The results show that the overall trend is consistent，which verifies the feasibility of the present design.

Abstract:With the increasing complexity of spacecraft functions and the improvement of software scale，there are many problems in the operating systems commonly used in the aerospace industry，e.g.，insufficient drivers and third-party library resources. Linux system has the characteristics such as stability，open source， and rich support，and has been widely used in high-reliability areas. Therefore，it is expected to meet the demands of complex applications to the aerospace industry. However，the amount of Linux system code is huge，and it is difficult to carry out aerospace software engineering and reliability assurance work. Based on the practical application of aerospace engineering，in this paper，an engineering method for Linux system software quality assurance is proposed according to the commercial and self-developed demands，which provides engineering ideas for the development of aerospace operating system related products.

Abstract:The space station era has brought new challenges to the tracking， telemetry， and command (TT&C) and communication system， such as longer guarantee time， higher coverage requirements， stronger data transmission capability， and better in-orbit working and living experience for astronauts. Combined with the capability characteristics of space-based TT&C and communication means such as the tracking and data relay satellite system (TDRSS) and the satellite navigation system， a solution based on space-based means is proposed， and tracking and data relay satellites are adopted， by which the coverage rate of TT&C for astronaut extravehicular activities is increased to nearly 100%. Furthermore， a multi-satellite and multi-target working mode is adopted to guarantee various rendezvous and docking modes， and the safe operation of the space station is ensured in a regular manner through the continuous or short message service by the S-band multiple access (SMA) links of tracking and data relay satellites and the Beidou short message service. The space-ground integrated network technology is provided to service for astronauts in the activities of in-orbit internet access， space-ground communication， and load experiment data transmission.

Abstract:In order to grasp the ignition temperature characteristics of multi-engine clusters in the space station， a high-altitude simulated thermal test is carried out on a 150N twin-engine cluster. The effects of single-engine ignition， twin-engine ignition， and thermal control components of the cluster frame wrap on the engine operation are studied. The test results show that the long-time ignition of a single engine leads to approximate linear increases in the temperatures of the oxidizer and fuel solenoid valves of the non-ignited engine， and the average maximum temperature rise rates are 0.033°C/s and 0.047°C/s， respectively. When the twin engines are ignited simultaneously， the throat temperature of the combustion chamber with the center-axis spacing of 180 mm will not be affected by the ignition of the adjacent engines. The temperature of the oxidizer solenoid valve remains basically unchanged， and the temperature rise rate of the fuel solenoid valve installed obliquely increases by 0.018 ℃/s due to the thermal baking of the adjacent unit， accounting for about 35% of the total temperature rise rate. The long-time ignition of a single engine on the twin-engine cluster will continue to produce thermal baking effects on the head flange and solenoid valve of the non-ignited engine， and the thermal control components can effectively reduce the thermal effect of baking after the twin-engine cluster frame is wrapped with the thermal control components.