Space Exploration Activities Research Articles

Digital Twin of Space Environment: Development, Challenges, Applications, and Future Outlook

This paper explores and discusses the revolutionary applications of digital twin technology in space environments and its profound impact on future space exploration activities. Originating from a proposal by the National Aeronautics and Space Administration (NASA) in 2002, digital twin technology aims to enhance the safety and reliability of space missions by creating precise virtual models. As the technology has evolved, its applications have successfully expanded beyond aerospace to include Industry 4.0, healthcare, and urban management, demonstrating remarkable cross-industry adaptability and broad impact. In space applications, digital twin technology can not only improve spacecraft design and maintenance processes but also enhance the efficiency of mission planning and execution. It plays a crucial role in astronaut training and emergency response as well. Particularly in extreme space conditions, this technology provides real-time monitoring and fault prediction, significantly enhancing mission safety and success rates. However, despite its recognized potential, the implementation of digital twins in space environments faces numerous challenges, including data transmission delays, model accuracy, and the design of user–system interactions. In the future, as artificial intelligence (AI) and machine learning (ML) technologies become mature and integrated, the digital twin will play a more central role in space missions, especially in remote operations, complex system management, and deep space exploration. This article is to overview key technical features, application examples, and challenges of digital twin technology, aiming to provide a comprehensive reference framework for researchers and developers while inspiring further in-depth studies and innovative applications.

Bioinspired flexible gripper for vacuum non-cooperative target capture

With the development of space exploration activities, the proliferation of non-cooperative targets in space, such as defunct satellites and space debris, has made the development of efficient and reliable non-cooperative target capture technologies in space a priority for space exploration. In this paper, a flexible gripper inspired by the dermo-muscular sac found in flatworms is presented to address the challenges of non-cooperative target capture in the vacuum environment of space. The gripper design leverages magnetorheological fluid and a magnetic field to enable adjustable stiffness, facilitating the effective grasping of delicate target objects while ensuring a stable connection post-capture. Extensive tests demonstrate the strong potential of the gripper for space applications, showcasing its ability to adjust pre-grip contact force and increase gripping force by adjusting indentation depth. The simplicity of the design contributes to ease of manufacturing, making it a promising tool for future space missions.

Low-thrust trajectory optimization of deep space exploration based on discrete pulse method

Deep space exploration is gradually becoming the hot mission of human space activities, and this kind of mission has the characteristics of a long mission cycle, complex space environment, high fuel demand, and difficult telemetry track and command, etc. It is the future trend to carry out deep space exploration activities using low-thrust propulsion systems, and the trajectory optimization of interplanetary missions is one of the significant difficulties. Considering the characteristics and difficulties of interplanetary missions, a method of transfer orbit preliminary design in the multi-body system is proposed in this paper. The simulation results illustrate that the transfer orbit obtained by the method in this paper can provide a reliable initial guess for the optimization of high-precision orbit and decrease convergence sensitivity. The research results can provide a significant reference for the implementation of deep space exploration missions in China in the future.

Modeling and experimental evaluation of membrane distillation aimed at urine treatment for direct potable reuse in space stations

Improving wastewater reuse systems represents a game changer for the economy of space exploration activities. The goal of this research is to evaluate direct contact membrane distillation for the treatment of urine aimed at direct potable reuse in space stations. A transient, 2-D model able to predict the membrane distillation system behavior under different operating conditions is developed. The model is validated by experimental tests conducted with a synthetic urine-like feed solution, considering both productivity and final water quality. The water flux and quality analyses imply high rejection of soluble salts and organics. However, direct water reuse may be compromised by the ammonia passage. A sensitivity analysis is thus performed to investigate the effects of feed pH, temperature, and cross-flow velocity on water flux and ammonia passage. The system shows the capability of treating 8 L of urine up to 90–95 % recovery rate, during 10 h of daily operation at 40 °C feed and 20 °C distillate inlet temperatures. This amount is sufficient to satisfy four crew members while meeting high system compactness. Concurrently, the ammonia passage may be limited by lowering the feed pH, thus easing the post-treatment steps necessary for safe direct reuse.

A reverse chain search algorithm for the resource constraint in deep space detectors

Deep space exploration activities can effectively promote the development and application of space technology, which holds significant scientific and strategic value. Detectors operating in deep space are of long mission periods and substantial distance from Earth, posing challenges in timely resource replenishment. Moreover, scheduled missions may face external uncertainties, hindering their smooth execution. Therefore, resource constraint processing strategies that possess dynamic adjustment capabilities play a crucial role in ensuring the successful execution of deep space detectors. Existing methods mainly focus on studying fixed mission sequences, and the efficiency of planning methods is not high. Specifically, the single uncertainty is only considered, and there is a lack of detection and processing mechanisms, rendering the requirements of deep space detectors inadequate. In this paper, we propose a reverse chain search algorithm, aiming to efficiently plan missions subject to resource constraints and let the mission sequence to possess a certain degree of dynamic repair capability. The results have demonstrated that the resource allocated to each mission is within the resource value range. Compared with the classic algorithm, the proposed algorithm has fewer iterations and whose maximum flow value is accurate. Meanwhile, the potential resource constraints problem during execution can be alerted with the detection and warning system. The missions that were warned are repaired by a dynamic resource repair system, and the proposed algorithm is of higher efficiency and a certain ability to resist external uncertainties. Overall, this paper lays a solid foundation for the processing of resource constraints for deep space detectors.

Electrochemical Catalytic Synthesis of CH3OH for In‐situ Resource Utilization

AbstractIn space exploration activities, a large amount of materials needs to be carried, which limits the sustainable development of exploration activities. In‐situ resource utilization (ISRU) is an important means to realize resource recycling and continuous space exploration, which converts space resources into oxygen and hydrocarbon fuels. The traditional ISRU in outer space mainly uses high temperature and high pressure to electrolyze water or reduce CO2, having problems such as low conversion efficiency, high energy consumption, and excessive equipment volume. Here, an electrochemical catalytic synthesis technology based on a microfluidic device is proposed, which can convert H2O and CO2 into O2 and organic matter by electrocatalytic method at room temperature and achieve efficient energy and matter conversion. The gas‐liquid mixing and electrochemical reaction were analyzed. A mathematical model of gas‐liquid two‐phase mixing and microfluidic chemical reaction was established. The research results demonstrate the reliability and efficiency of the microfluidic reaction device designed in this paper for ISRU.

An algorithm of dynamic temporal constraints for the mission series in deep space detectors

Deep space exploration activities can effectively promote the development and application of space technology, which holds significant scientific and strategic value. The multi-mission and long-period detector is executed in deep space, and numerous temporal constraints are generated by mission planning. Moreover, scheduled missions may face external uncertainties, hindering their smooth execution. Therefore, temporal constraint processing strategies that possess dynamic adjustment capabilities play a crucial role in ensuring the successful execution of deep space detectors. Existing methods primarily concentrate on investigating fixed mission series, with limited efficiency in planning. Specifically, these methods do not rigorously enforce temporal constraints and lack the capability to handle the disruptions caused by emergencies, which hinder the smooth execution of planned missions. In this paper, we propose a dynamic temporal constraints algorithm, aiming to efficiently plan missions subject to temporal constraints and let it possess a certain degree of dynamic adjust capability. The simulation results demonstrate the effective simplification of redundant temporal constraints in mission networks by the proposed algorithm. In comparison to the classical algorithm, the computation time exhibits a clear advantage. Furthermore, the proposed algorithm possesses the capability to perform local, small-scale dynamic adjustments in response to emergencies that may disrupt the normal execution of missions. Consequently, this research establishes a robust basis for addressing temporal constraints in deep space detectors.

Development of waterless extra-terrestrial concrete using Martian regolith

Human colonization on Martian land is gaining significant attention in space exploration activities that demand in-situ resource utilization in the development of construction and building materials for human habitation. This research explores the utilization of Martian regolith simulant and sulfur to create extra-terrestrial concrete (ETC) with a property suitable for constructing human habitat on Mars. The primary objective of the study is to maximize the utilization of Martian regolith simulant to achieve the desired compressive strength of 25 MPa (average compressive strength specified for concrete used in residential buildings on Earth). Mechanical properties, phase transition, and microstructural characteristics of Martian regolith based-ETC under varied temperature conditions (0 °C, 40 °C, and 50 °C) on Mars were investigated. The optimal mixture proportion of ETC had 70% (by wt.) of Martian regolith and exhibited an average compressive strength of 27 MPa. The formulated ETC could retain up to 25 MPa of compressive strength at 40 ℃ and 50 ℃, and could reach up to 35 MPa at 0 ℃ temperature conditions. The change in compressive strength was attributed to the sulfur sublimation and pore closure brought about by freezing at extreme temperatures, respectively.

Modeling the Radiation Environment of Energetic Particles at Mars Orbit and a First Validation against TGO Measurements

Sending astronauts to Mars will be a milestone of future deep space exploration activities. However, energetic particle radiation in deep space and in the Mars environment is a major risk to the health of future human explorers. The nominal Martian surface radiation field contains primary Galactic Cosmic Ray (GCR) particles and secondary particles generated in the Martian atmosphere and the regolith. Some of these secondary particles may propagate upward and even be detected at the orbit of Mars contributing to the orbit radiation. Studying the Mars orbit radiation environment is critical for planning future Mars orbital missions. Therefore, we calculate the Martian orbit radiation dose rate considering the primary GCR spectra provided by the Badhwar-O’Neill 2014 model and the secondary particles modeled by the state-of-the-art Atmospheric Radiation Interaction Simulator. Specifically, we calculate the integral dose rate of each particle type and its dependence on orbit height, surface pressure, and solar modulation intensity. Our analysis shows that modulation intensity is the most dominating factor and that different surface pressures make less than a 1% impact. We also derive the sensitive energy range of detected particles contributing to the dose rate and further validate our prediction against the measured data by Liulin-MO on TGO at a circular orbit around Mars. This may conduce to predicting the radiation risks in Mars orbit and providing constructive reference parameters for the crewed space industry.

Biomimetics for innovative and future-oriented space applications - A review

Nature benefits from a progressive evolution over millions of years, always adapting and finding individual solutions for common problems. Hence, a pool of diverse and efficient solutions exists that may be transferable to technical systems. Biomimetics or bio-inspiration has been used as a design approach for decades, revolutionizing products and processes throughout various industries. Thus, multiple examples can also be found in the space sector, since many characteristics found in biological organisms are also essential for space systems like response-stimuli adaptability, robustness and lightweight construction, autonomy and intelligence, energy efficiency, and self-repair or healing capabilities. This review focuses on biomimetics within the field of aerospace engineering and summarizes existing bio-inspired concepts such as drilling tools (wood wasp ovipositor drilling), telescopes (lobster eye optics), or gasping features (gecko feet adhesion capabilities) that have already been conceptualized, partially tested, and applied within the space sector. A multitude of biological models are introduced and how they may be applicable within the space environment. In particular, this review highlights potential bio-inspired concepts for dealing with the harsh environment of space as well as challenges encountered during rocket launches, space system operations and space exploration activities. Moreover, it covers well-known and new biomimetic concepts for space debris removal and on-orbit operations such as space-based energy production, servicing and repair, and manufacture and assembly. Afterwards, a summary of the challenges associated with biomimetic design is presented to transparently show the constraints and obstacles of transferring biological concepts to technical systems, which need to be overcome to achieve a successful application of a biomimetic design approach. Overall, the review highlights the benefits of a biomimetic design approach and stresses the advantage of biomimetics for technological development as it oftentimes offers an efficient and functional solution that does not sacrifice a system’s reliability or robustness. Nevertheless, it also underlines the difficulties of the biomimetic design approach and offers some suggestions in how to approach this method.

Decadal Quasi-2-Day Wave Observations in the Equatorial Mesopause Region by a Meteor Radar over Kototabang (0.2°S, 100.3°E) and TIMED/TIDI and Comparison with Quasi-2-Day Wave Observations at Mid-Latitudes

We studied the characteristics of quasi-two-day wave (QTDW) using the meridional wind in the mesosphere and lower thermosphere (MLT) obtained from a meteor radar over Kototabang (KB, 0.2°S, 100.3°E) from 2003 to 2012. Atmospheric oscillations have a crucial impact on atmospheric dynamics, which contributes to more accurate space weather forecasting, thus providing a more secure space environment for human space exploration activities such as remote sensing and satellite navigation. QTDWs are typical atmospheric oscillations in the upper stratosphere, mesosphere and lower thermosphere. The occurrence time, amplitudes, periods and vertical wavelengths of QTDW events are analyzed statistically. Data obtained from the TIMED Doppler Interferometer (TIDI), which can measure wind and temperature and is onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite, are used to analyze the global distribution and spatial structure of QTDWs with different zonal wavenumbers. The characteristics of the QTDWs over KB are compared with the QTDWs at the middle latitudes using the meridional wind data from a meteor radar over Wuhan (114.4°E, 30.6°N), Beijing (116.5°E, 39.9°N) and Mohe (121.1°E, 50.1°N). The amplitudes of the QTDW and spectral analysis are calculated by the least squares fitting method. Our results demonstrate that QTDWs are present almost all year around over KB. The occurrence time, amplitudes, periods and vertical wavelengths of QTDW events with different zonal wavenumbers are determined in this study. We also find that the statistical characteristics of the QTDWs in KB are different from those at middle latitudes. The westward zonal wavenumber −4 (W4) events gradually increase with increasing latitude, whereas westward zonal wavenumbers −1, −2, and −3 (W1, W2 and W3, respectively) events all decrease with increasing latitude.

Implementing safety zones for lunar activities under the Artemis Accords

Improving technology could enable new commercial and scientific activities in outer space, including crewed stations, space mining, and advanced planetary science in locations like the Moon or asteroids. To facilitate novel space exploration activities, the United States led the development of a new multilateral set of principles, the Artemis Accords. The Accords and other soft law propose the ability to establish “safety zones” surrounding space operations of participant states and mission-authorized nationals. Safety zones are controversial because their implementation could violate the non-appropriation and other principles of the Outer Space Treaty. Thus, successfully implementing safety zones is essential to the Artemis Accords’ framework to unlock space resources and encourage other novel activities. This study reviews the history and principles behind safety zones in outer space. It identifies the requirements such zones place on operators and the obligations they can create for other states and actors. In evaluating three hypothetical case studies on the Moon, it proposes an algorithm for the establishment, alteration, management, and termination of a safety zone. Finally, it recommends pathways to develop and implement safety zones in an iterative manner consistent with international law and best practices for industry, including conceiving of safety zones as “safety conditions.”

Highlight Advances in Planetary Physics in the Solar System: In Situ Detection Over the Past 20 Years

Planetary science is the science of studying planets, moons, and planetary systems. The scale of the research objects ranges from small meteoroids to large gas giant planets, and the research purpose is to determine their composition, dynamics, formation, evolution, mutual relationship, and history. With the development of human space technology, planetary exploration has become one of the most important space exploration activities of mankind. According to statistics from the Spacecraft Encyclopedia website, as of December 2021, a total of 252 planetary probes have been launched around the world. The missions reveal the deep space to humankind. In this paper, we review some advances in planetary science made by these missions in the past years. The topics involve interior structures, geological features, atmospheres, magnetospheres, and so on, not every aspect but as much as possible. Although there are still many extraordinary scientific results that have not been included, we believe that this review can already help people learn about the scientific results of planetary exploration and hopefully inspire the next generation of planetary missions.

Design of a non-cooperative target capture mechanism for capturing satellite launch adapter ring

Space debris is growing dramatically, which poses a serious threat to space exploration activities. Especially the large non-cooperative target, such as malfunctioning satellites. This paper proposes a capture mechanism for the launch adapter ring that is usually available on satellites as the capture object, which used for in-orbit capture of malfunctioning satellites. Firstly, introduce the design conditions, the overall design plan, carry out the mechanical mechanism design, sensor system configuration, electrical system design, and explain the capture process. Secondly, analyze the capture tolerance. Thirdly, by establishing the kinematics model of the captured finger, use D-H parameter method for kinematic analysis, and analyze the dynamic in the capturing process. In addition, the control strategy is proposed, and the clamping force model, friction identification model, and servo control strategy are established. Then, the prototype is manufactured, and the clamping force, stiffness, capture loads, and capture tolerance are tested. Finally, the air-floating platform is used to verify the capture test of the launch adapter ring in a microgravity environment. The experimental results show that the developed capture mechanism meets the design conditions and has the ability to capture launch adapter ring of satellites in orbit.

A numerical approach for response of whipple shields with coated and monolithic front bumper to hypervelocity impact by spherical projectiles

Orbital debris in space offers a constant threat to spacecraft, satellites, and the International Space Station (ISS). There is a growing concern as the number of satellites and other space objects keep increasing year-on-year with advancements in space exploration and orbital activities. The threat posed by the small debris or MMODs (micrometeoroid orbital debris) to satellites and spacecraft can be prevented using Whipple shields made of impact-resistant materials. In the current work, a numerical approach has been utilized to simulate hypervelocity impact of spherical projectiles of diameter 4 mm on monolithic and coated whipple shields to determine the extent of damage, and the deformation behaviour. The simulations were conducted at 3.5 km/s and 5.5 km/s. The computational work was carried out using AUTODYN® module of ANSYS® finite element software.

Preliminary design of Martian Moons eXploration (MMX)

Martian Moons eXploration (MMX) is a mission under development in JAXA in cooperation with NASA, CNES, ESA, DLR to be launched in 2024. This paper introduces the result of its preliminary design and the latest status of the MMX program, putting more weight on the novel part of the mission. The goal of MMX is to reveal the origin of the Martian moons and then to make progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer part of the early solar system. Additionally, the mission is to survey two Martian moons and return samples from Phobos. Add to those MMX's contribution to the planetary science field, on the growing discussion on the International Space Exploration activities, MMX's contribution to future human Mars exploration is also considered as an essential aspect of the program. Following the system definition study results presented in the previous conference, the following items will be reported in this paper. First, as a result of the comprehensive completion of the Phase-B activities, the preliminary design is completed in coordination with the design of the spacecraft system, mission instruments, and operation plans. This paper describes the proximity and surface operations around Phobos in detail. Second, Phase-C activities have started, incorporating engineering models manufacturing and tests. Those of critical technologies for surface exploration are described in detail. Moreover third, the programmatic aspects, including international cooperation frameworks and the program schedule, are presented.

Solar noise influence on TT&C link of Mars Exploration Mission

<p indent="0mm">During deep space exploration activities, solar conjunction occurs due to changes in the relative motion between the Earth, the spacecraft and the Sun. During solar conjunction, the main beam of the antenna of the ground deep space TT&amp;C equipment is aligned with the spacecraft as well as the sun. At this time, the strong electromagnetic radiation generated by the sun will enter the main beam of the ground deep space TT&amp;C antenna and bring strong interference to the spacecraft signal received. Therefore, solar noise is an important factor affecting the performance of deep space TT&amp;C communication link. During China’s first Mars Exploration Mission—Tianwen-1, the opportunity of the Sun-Earth-Mars angle-off less than 5° will be used for the first time, that is, from September 23 to October 23, 2021, the <sc>35 m</sc> diameter deep space TT&amp;C equipment of China’s Deep Space Tracking and Control Network located in Kashi, Xinjiang and Jiamusi, Heilongjiang. The influence of solar noise on the TT&amp;C communication link of Tianwen-1 during solar conjunction was studied, the latest experimental results were obtained, and the preliminary law of the influence of solar noise on the X band TT&amp;C link of China’s deep space TT&amp;C equipment when the distance from the Earth is 400 million kilometers was obtained. The completeness and correctness of the downlink telemetry data after frame synchronization of the deep space TT&amp;C station were verified, and the effect of solar noise on the reception performance of the deep space TT&amp;C station was evaluated by calculating the frame error rate of the telemetry received. According to data analysis, when the azimuth deviation angle is less than 3°, the influence of solar thermal noise increases, and when the azimuth deviation angle is less than 1°, the influence of solar thermal noise increases significantly. When the deviation angle is less than 2°, the influence of solar thermal noise increases, and when the deviation angle is less than 0.5°, the influence of solar thermal noise increases significantly. Since the Tianwen-1 Mission is in the midst of an 11-year lull in solar activities, the impact of solar noise is relatively small. During the extended mission of Tianwen-1, the ground deep space TT&amp;C system will continue to monitor the influence of the TT&amp;C link during solar conjunction, and strive to obtain the influence information of a complete solar activity cycle, so as to provide more accurate reference for the analysis of the influence of solar noise in the subsequent deep space exploration activities. Considering that Ka-band will be an important frequency band for deep space TT&amp;C communication in the future, it is necessary to further strengthen research and experimental verification of the influence of solar noise on the deep space TT&amp;C link at Ka-band.

The international legal regime of outer space between Res Communis and Res Nullius

The publication is devoted to the issue of the international legal regime of outer space. The author attempts to determine the optimal model of international legal regulation for relations regarding the utilization of outer space and its resources. The basic international legal regimes applied to areas outside the exclusive national jurisdiction are studied. The main attention is paid to the regimes of res nullius, res communis, and the principle of the common heritage of mankind. The current international legal regulation of outer space exploration and utilization activities is analyzed through the prism of these regimes, as well as in the context of the category of global commons, which often includes outer space. It is emphasized that the mentioned category, although widely used in modern scientific legal discourse, is not clearly defined. Given that the concept of public goods has received a special development in economic theory, it is proposed to take into account the economic properties of such goods in developing regimes for their legal regulation. The peculiarities and complexity of outer space utilization relations as an object of legal regulation are identified. In this regard, a comprehensive and complex international legal regime that combines elements of res nullius, res communis, and the common heritage of mankind in relation to the objects of outer space with different natural and, consequently, economic properties should be elaborated. In addition, the latest trends in national and international law-making related to the formation of a legal regime for the extraction of celestial bodies resources and the commercialization of these activities are analyzed. Their influence on the international legal regime of outer space and tendencies of its future evolution is determined. The importance of a balanced national approach to a new legal regulation of space resources commercial development is emphasized.

Rigid-Flexible Coupled Dynamic and Control for Thermally Induced Vibration and Attitude Motion of a Spacecraft with Hoop-Truss Antenna

As space exploration activities are developing rapidly, spacecraft with large antennas have gained wide acceptance in providing reliable telecommunications and astrophysical observations. In this paper, the dynamic responses and control strategy for a spacecraft with a large hoop-truss antenna under solar flux shock are studied. According to the momentum and angular momentum principle, the rigid-flexible coupled rotational dynamic equation and the translational dynamic equation of the system are established, which include the attitude motion of the rigid main body and the vibration of the antenna. Then, a finite element model of the antenna is established to analytically obtain the corresponding vibration modal shape matrix and natural frequencies. Last, the coupled responses for the attitude motion and vibration are investigated. The corresponding control strategy is designed based on a double-loop structure sliding mode control method. The Lyapunov method is used to demonstrate the global asymptotic stability of the system. Simulations verify the effectiveness of the proposed rigid-flexible coupled model and control strategy.

Research Status and Future Development of Deep Space Security

As deep space exploration activities increase worldwide, the exploration environment becomes increasingly complex and the exploration tasks become increasingly difficult. Therefore, it is of great practical significance to research on deep space security issues. In this study, we first clarify the basic connotation of deep space security, briefly describe the significance and key issues of deep space security research, and summarize the research status and future development of four key deep space security issues: space radiation threat, planetary protection, space heritage protection, and space legislation. The study indicates that space radiation has the characteristics of multiple threat sources and high radiation intensity and should be researched from the perspectives of physical, biomedical, and chemical protection. Planetary protection mainly faces the challenges of pollution and impact of deep space spacecraft, and research should be conducted from the perspectives of deep space microbial detection and disinfection technologies as well as policy formulation. Space heritage protection is controversial in terms of evaluation and protection measures owing to political, cultural, and legal differences among countries, and it should be researched from the perspectives of international cooperation, deep space spacecraft, and reduction of human impact. Due to the complex international relations among countries, it is difficult for the effectiveness of current laws and regulations to become the consensus of the international community; therefore, research should be conducted from the aspects of international legislative organizations, domestic research institutions, and the improvement of domestic legal systems.