Deep Space Exploration Missions Research Articles

Millimeter micro‐coaxial beam steering array for high‐speed satellite communications

AbstractWide‐band low‐loss passive beam steering array presents to be essential part of the RF front‐ends for high‐speed detection during deep space exploration missions. In this letter, the copper‐based additive manufacturing technology is proposed for the implementation of low‐profile (~0.1λ) antenna design. Adopting the micro‐coaxial line as the basic design unit enables wide bandwidth design. In addition, the broadband designs of Butler matrix, planar antenna element, and transmission transitions are proposed, respectively. The miniaturization of the metallic patch antenna is realized using a double slotted design, ensuring an array space of ~0.5λ, which beneficial for the low‐lobe beam steering. Experimental results show that the antenna array with an overall size of 39 × 29 × 0.5 mm presents four beams located at ±14° and ±43°, respectively. The bandwidth of return loss better than −10 dB ranges from 65 to 71 GHz. The measured result matches well with the simulated ones, which makes its potential operation for satellite applications.

Initial trajectory design of low-thrust spacecraft considering attitude constraints

The fuel carried by deep space exploration spacecraft is crucial for the completion of their exploration missions, and the fuel for attitude control engines is even more precious. In order to reduce the control requirements for attitude control systems, this paper proposes a shape-based trajectory optimization algorithm that considers attitude constraints for low-thrust spacecraft. This method obtains a more accurate transfer trajectory by considering the change rate and change range constraints of the propulsion acceleration direction of spacecraft. By comparing the simulation results without considering spacecraft attitude constraints, it is confirmed that the proposed algorithm considering attitude constraints is very important for the initial design of transfer trajectories. This is of great significance for high-precision initial trajectory optimization of deep space exploration missions.

Insight into rechargeable batteries in extreme environment for deep space exploration

AbstractSince the beginning of the new century, the objectives of deep space exploration missions targeting celestial bodies such as the Moon and Mars shift from “understanding celestial bodies” to “utilizing celestial bodies.” With respect to the successful operation of various load missions, secondary battery systems play a crucial role in supplying energy. However, unlike terrestrial environment, extremely harsh extraterrestrial conditions, including extreme temperatures and radiation, severely limit the application of batteries in deep spaces. This work covers recent advancements in batteries, including electrolyte/electrode optimization strategies and thermal management under extreme low‐ and high‐temperature conditions and the mechanism analysis of key battery components under radiation environments. Finally, perspectives are given on the remaining challenges posed by battery applications in extreme deep space environment.

Preliminary neutronics design and analysis of lithium heat pipe cooled space reactor with low-enriched uranium

The space nuclear reactor cooled by heat pipes has become the preferred choice for future space missions and deep space exploration missions. The use of low-enriched uranium (LEU) is promoted to achieve the goal of nuclear non-proliferation worldwide. In this study, a lithium heat pipe cooled space reactor with LEU (HP-LEU) was proposed based on Heat Pipes-Segmented Thermoelectric Module Converters (HP-STMCs), with the addition of moderators. The HP-LEU employs yttrium hydride (YH2) as the moderator and 19.9 % enriched uranium nitride (UN) as the fuel. The neutronics analysis has been performed on the HP-LEU reactor and the results have showed that the HP-LEU has a lifetime of more than 12 years. Two control systems have been applied in the reactor and have demonstrated the capacity to independently regulate and shut down the reactor. The total temperature reactivity coefficients are consistently negative, indicating that the HP-LEU reactor is inherently safe during operation. During normal operation, the temperatures of the materials are all acceptable. This study can serve as a reference for lithium heat pipe cooled space reactors with LEU.

Definition of multispectral camera system parameters to model the asteroid 2001 SN263

In 2012, Brazil began the studies to send its first deep space exploration mission, ASTER, which would be the first mission to orbit a triple asteroid system, 2001 SN263. We aim to contribute to the ASTER mission by defining the parameters of a multispectral camera system that will be used to study the asteroid system 2001 SN263, through software simulations that should help planning the data collection. We inserted the shape model of the objects in the software POV-Ray and modeled two cameras, a Wide Angle (WAC) and a Narrow Angle (NAC). We inserted the asteroid's parameters and simulated the satellite position. We created various scenes so we could obtain a good view of the asteroid. Alpha is entirely visible only in the WAC images, while the NAC is expected to reveal surface details. Beta seems relatively small in the WAC images, whereas we obtain a broad view from the NAC at 100 km distance. Gamma, smaller than Beta, should provide more detailed images through the NAC, whereas the WAC images should be able to show its inclined orbit around Alpha. To see Gamma behind Alpha in its revolution movement, we would have to elevate the camera's orbit. The method employed to simulate images generated by satellite cameras can be applied to other scenarios where the target requires imaging, extending beyond the field of planetary geology.

Cascade control system design for a space nuclear reactor

Space nuclear reactors with high power density and long operational life are suitable for deep space exploration missions. The design and dynamics of space nuclear reactors are different from those of conventional reactors. Thus, it is necessary to develop a space reactor control system design and validation simulation system to study its dynamic characteristics and control strategy. In this study, a simulation system of the space reactor was established, and steady-state and dynamic calculations were performed to obtain the operating characteristics of the space reactor. Based on the operating characteristics of the space reactor, the control strategy of the space reactor was proposed, and the cascade control strategy of electric power was designed. The control performance was tested under typical operating conditions. The correctness and effectiveness of the control method was verified, and the proposed method provided a reference for space nuclear reactor control studies.

Orbit Determination of High Orbit Spacecraft based on BDS-3 using Extended Kalman Filter

The positioning of highly elliptical orbit (HEO) spacecraft is very important in deep space exploration and other missions. The Beidou Navigation Satellite System (BDS-3), which was completed in 2020, has put forward new ideas for using GNSS technology to make up for the lack of earth-based TT&C systems. At the same time, the selection of the gravity field order and the perturbation forces must be considered when using dynamical methods for HEO spacecraft positioning. In this paper, simulation experiments are carried out based on the Two-Line Orbital Element (TLE) data of BDS. Two HEO satellites with different semimajor-axis (67509.6 km, 212857.3 km) are selected as the target spacecraft orbits. The single point positioning (SPP) method and Extended Kalman Filter (EKF) method are used for HEO spacecrafts positioning respectively. The experiments show that a 20×20 order gravity field model can be chosen for the orbital integral of HEO spacecraft orbits, and the integration error caused by solar gravity and lunar gravity should be taken into account with the change of orbital altitude. Adding Geostationary Orbit (GEO) and Inclined GeoSynchronous Orbit (IGSO) navigation satellites improved the visibility of these two orbits by 19.45% and 16.64%, respectively, and improved the GDOP value by 14.1% and 3.8%, respectively, compared to observing MEO satellites only. The use of the EKF method can effectively improve the positioning accuracy of the HEO spacecraft compared to the SPP method. For the spacecraft in HEO-1, the RMS value of the positioning errors of the EKF method was 67.82 m, and the accuracy of each direction was improved by 44.28%, 38.85%, and 38.62%, respectively. For the spacecraft in HEO-2, the positioning errors in the x direction of EKF method was within 12 km and within 2 km in the y and z directions. The accuracy of these three directions was improved by 84.91%, 79.24%, and 58.64%, respectively.

Study of long-term in-orbit pressure control of liquid krypton cryogenic storage tank

Due to its high specific impulse, low toxicity, contamination, safety, and cost, krypton has gradually replaced other propellants as the primary choice for electric thrusters on deep-space exploration and large-orbit transfer missions with long-range, long-duration, and large-thrust requirements. However, due to the cryogenic propellant itself having a low boiling point, controlling the pressure change of krypton cryogenic propellant during the process of long-term cryogenic storage has emerged as one of the most important issues that must be resolved and proven to achieve non-destructive storage of cryogenic propellant. This paper examines the necessity and viability of a cryogenic gas propellant liquefaction storage scheme and quantifies the effectiveness of tank pressure control of the supercooled liquid krypton injection mixing scheme to solve the problem at present. Its purpose is to offer scheme examples for the design of a krypton thruster propellant storage unit and the in-tank pressure control during the long-term application process.

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.

On-demand fabrication of piezoelectric sensors for in-space structural health monitoring

Inflatable structures, promising for future deep space exploration missions, are vulnerable to damage from micrometeoroid and orbital debris impacts. Polyvinylidene fluoride-trifluoroethylene (PVDF-trFE) is a flexible, biocompatible, and chemical-resistant material capable of detecting impact forces due to its piezoelectric properties. This study used a state-of-the-art material extrusion system that has been validated for in-space manufacturing, to facilitate fast-prototyping of consistent and uniform PVDF-trFE films. By systematically investigating ink synthesis, printer settings, and post-processing conditions, this research established a comprehensive understanding of the process-structure-property relationship of printed PVDF-trFE. Consequently, this study consistently achieved the printing of PVDF-trFE films with a thickness of around 40 µm, accompanied by an impressive piezoelectric coefficient of up to 25 pC N−1. Additionally, an all-printed dynamic force sensor, featuring a sensitivity of 1.18 V N−1, was produced by mix printing commercial electrically-conductive silver inks with the customized PVDF-trFE inks. This pioneering on-demand fabrication technique for PVDF-trFE films empowers future astronauts to design and manufacture piezoelectric sensors while in space, thereby significantly enhancing the affordability and sustainability of deep space exploration missions.

The Reliability Modeling and Evaluation of a Cusped Field Thruster When Undertaking a Gravitational Wave Detection Mission

The propulsion system, particularly electric propulsion, holds immense significance in the context of gravitational wave detection missions. One of the key factors of a deep space exploration mission is the lifetime of the electric propulsion. Ensuring the high reliability of the propulsion system is of paramount importance; however, achieving this is challenging in the absence of adequate failure data. Conducting ground tests for a thruster tends to encounter two limitations: a lack of failure data and time constraints. To address these challenges, we propose a semi-physics sputtering method that combines a physical erosion model with empirical processes. In this study, we focus on evaluating the lifespan of a cusped field thruster (CFT) for potential application in gravitational wave detection missions. Our analysis revolves around modeling non-conservative forces in a space environment and examining their impact on a thruster’s longevity. The results indicate that, in gravitational wave missions, the survival rate of a thruster’s lifespan at 8000 h is 0.75. At a constant voltage of 500 V, the maximum corrosion depth after 5000 h is 3.1 mm, while the minimum is 0.49 mm.

Energy-efficient craters detection based on spiking neural network using digital elevation models

Craters are the primary topographic features on celestial bodies and play a vital role in deep space exploration missions. Recently, artificial neural networks (ANNs) have excelled in crater detection. However, when compared to ANNs, spike neural networks (SNNs) have the advantage of low power consumption, making them more suitable for resource-limited deep space environments. To the best of our knowledge, this is the first spiked-based crater detection model. Firstly, two conversion learning algorithms based on cluster neurons and vary-time windows neurons are proposed to address the non-differentiability problem of SNNs. Secondly, a calibration mechanism is introduced to correct the conversion loss between ANNs and SNNs. Thirdly, the experimental results demonstrate that the proposed scheme exhibits sufficient precision, while reducing the energy consumption cost by more than 10 times compared to the previous method. Additionally, this method is expected to offer new insights for segmentation tasks in resource-constrained environments.

Influence of magnetohydrodynamics configuration on aerothermodynamics during Martian reentry

This paper investigates the role of magnetohydrodynamics (MHD) on the aerothermodynamics (ATD) of a representative entry vehicle while flying into the Martian atmosphere. By strategically placing a flight-ready superconducting magnet at varied positions in the Schiaparelli reentry capsule of the ExoMars mission, we discern its impact on essential flow properties. The primary consequence of MHD during atmospheric entry is the generation of the Lorentz force, which increases the shock standoff distance resulting in a reduction of the heat flux on the spacecraft by pushing high-energy plasma particles away. Through different magnet configurations, three distinct cases are formed to comprehensively understand the effects and implications of each setup. The study is performed using the COOLFluiD MHD for EnTries, an in-house ATD solver. For case 1, the magnet's placement behind the ExoMars forebody at the stagnation point reduces the heat flux. In case 2, the magnet's relocation to the shoulder region explores its potential to mitigate communication blackouts by influencing the wake region's flow. However, this positioning also induces shock bending, leading to variations in post-shock species mass fractions and heat flux spikes in the post-shock region. Case 3, involving an additional magnet where the shock bends in case 1, showcases a consistent increase in shock standoff distance across the forebody, providing a longer relaxation zone for species equilibration. Our findings highlight that while the strength of the applied magnetic field is crucial, the magnet's size is equally pivotal in determining ATD behavior. Case 3 emerges as the most promising configuration, consistently reducing heat flux across the forebody and maintaining it in the afterbody. This study underscores the potential of multi-magnet configurations as next-generation MHD heat shields for Martian atmospheric entry, emphasizing the criticality of magnet placement and configuration in enabling future MHD-enhanced deep space exploration missions.

A Signal-Based Auto-Focusing Method Available for Raman Spectroscopy Acquisitions in Deep Space Exploration

With the development of technology and methodologies, Raman spectrometers are becoming efficient candidate payloads for planetary materials characterizations in deep space exploration missions. The National Aeronautics and Space Administration (NASA) already deployed two Raman instruments, Super Cam and SHERLOC, onboard the Perseverance Rover in the Mars 2020 mission. In the ground test, the SHERLOC team found an axial offset (~720 μm) between the ACI (Autofocus Context Imager) and the spectrometer focus, which would obviously affect the acquired Raman intensity if not corrected. To eliminate this error and, more importantly, simplify the application of Raman instruments in deep space exploration missions, we propose an automatic focusing method wherein Raman signals are optimized during spectrum collection. We put forward a novel method that is realized by evaluating focus conditions numerically and searching for the extremum point as the final focal point. To verify the effectiveness of this method, we developed an Auto-focus Raman Probe (SDU-ARP) in our laboratory. This method provides a research direction for scenarios in which spectrometers cannot focus on a target using any other criterion. The utilization of this auto-focusing method can offer better spectra and fewer acquisitions in focusing procedure, and the spectrometer payload can be deployed in light-weight bodies (e.g., asteroids) or in poor illumination conditions (e.g., the permanently shadowed region in the Lunar south polar area) in deep space exploration missions.

A Comprehensive Comparison of Various Galactic Cosmic-Ray Models to the State-of-the-art Particle and Radiation Measurements

Galactic cosmic rays (GCRs) are the slowly varying background energetic particles that originate outside the solar system, are modulated by the heliospheric magnetic field, and pose ongoing radiation hazards to deep space exploration missions. To assess the potential radiation risk, various models have been developed to predict the GCR flux near Earth based on propagation theories and/or empirical functions. It is essential to benchmark these models by validating against the state-of-the-art measurements. In this work, a comprehensive model–observation comparison of the energy-dependent particle flux has been performed, by combining five typical GCR models and observational data from the Cosmic Ray Isotope Spectrometer on board the Advanced Composition Explorer spacecraft at relatively lower energies and data from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics and Alpha Magnetic Spectrometer at higher energies. The analysis shows that, out of the five models investigated in this study, the optimal model, characterized by minimal relative difference or reduced chi-square divergence from measurements, depends on the particle type, energy range, and epoch of interest. Furthermore, a silicon slab is applied to compute the absorbed dose rate using conversion factors applied to GCR model outputs, and the results are compared to measurements from the Cosmic Ray Telescope for the Effects of Radiation. The comparisons in this paper have implications for the strengths and limitations of individual GCR models, advance our comprehension of the underlying GCR transport mechanisms, and also have strong application aspects for mitigating space radiation risks.

Microgravity Inhibits Cell Proliferation and Promotes Senescence and Apoptosis in Embryonic Stem Cells

With advancements in deep space exploration missions, long-term spaceflights pose potential hazards to the reproductive and developmental functions of astronauts. Embryonic stem cells (ESCs), which are crucial to the development and growth of individual organisms, are observably altered by a microgravity environment. However, the role and mechanisms of microgravity in other activities of ESCs are still unclear. Here, mouse embryonic stem cells (mESCs) were used to investigate and understand the effect of microgravity on their activities. Combined with the SJ-10 satellite and random position machine, which were utilized for spaceflight and microgravity simulation, respectively, the bioinformatic tools were also used to assess the effect that microgravity might have on mESC activities. Based on differentially expressed genes (DEGs) analysis, 114 DEGs were significantly up-regulated and 859 DEGs were significantly down-regulated in mESCs after being subjected to spaceflight. The activities, such as cell proliferation, senescence, and apoptosis, were selected and confirmed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. It demonstrated a reduced proliferation capability of mESCs but increased the number of senescent and apoptotic cells after being subjected to simulated microgravity. Real-time polymerase chain reaction analysis of the screened activity-related DEGs demonstrated approximately consistent trends of these gene expressions in both spaceflight and simulated microgravity, as was predicted by bioinformatics analysis. Overall, these findings suggest that microgravity inhibits the proliferation of mESCs and induces senescence and apoptosis, shedding light on the impact of microgravity on the fundamental functions of mESCs in reproductive and embryonic development.

Effect of TiO2 on the thermal performance and emissivity of glass coatings

Deep space exploration missions pose significant challenges to the temperature stability and thermal management of electronic components in spacecraft.

Research on Isolation and Protection Technology for Returning Astronauts of Deep Space Exploration Missions

With the acceleration of deep space exploration missions such as the moon, mars and asteroids, planetary protection has become an important issue that must be faced. In the near future, astronauts will perform extraterrestrial celestial operations in more distant and complex unknown environments, which may lead to a large increasing in probability and uncertainty of carrying unknown microorganisms after the spacecraft returning to the earth. From the perspective of protecting astronauts and the Earth's biosphere, it is necessary to conduct safe isolation and protection for astronauts returning from the outer space. In this paper, biological isolation and protection technologies at home and abroad are studied. For China’s future manned deep space exploration missions, we carry out a demand analysis, and propose a design scheme of isolation protection platform.

Analytical three-dimensional propulsion process of electric sail with fixed pitch angle

This paper proposes an analytical three-dimensional propulsion process of electric sail considering constant thrust angle. Due to the small characteristic acceleration of electric sails, its dimensionless form is defined as a perturbation parameter. For an electric sail with a determined initial state, an analytical approximate three-dimensional trajectory consisting of a primary term and perturbation terms can be derived by considering a reasonable approximation in the equation of motion. Furthermore, rectification steps are introduced to minimize approximation error caused by reasonable approximation and continuous changes in elements of osculating orbit. Despite the addition of fixed step rectification, the analytical estimation time is much shorter than the integration time, as the entire approximation process, including the rectification step, is analytical. The time required for analytical approximation is much lower than that for integration. Significantly, the parking orbit of the electric sail required for analytical approximation can be arbitrary. Based on the characteristics, the proposed analytical approximate three-dimensional trajectory is suitable for fast trajectory prediction of various complex deep-space exploration missions, especially for splicing trajectories with different pitch angles to solve problems with fixed targets.

Intelligent navigation for the cruise phase of solar system boundary exploration based on Q-learning EKF

With the continuous advancement of deep space exploration missions, the solar system boundary exploration mission is established as one of the China's most important deep space scientific exploration missions. The mission of the solar system boundary exploration has many challenges such as ultra-remote detection distance, ultra-long operation time, and ultra-long communication delay. Therefore, the problem of high-precision autonomous navigation needs to be solved urgently. This paper designs an autonomous intelligent navigation method based on X-ray pulsars in the cruise phase, which estimate the motion state of the probe in real time. The proposed navigation method employs the Q-learning Extended Kalman filter (QLEKF) to improve navigation accuracy during long periods of self-determining running. The QLEKF selects automatically the error covariance matrix parameter of the process noise and the measurement noise by the reward mechanism of reinforcement learning. Compared to the traditional EKF and AEKF, the QLEKF improves the estimation accuracy of position and velocity. Finally, the simulation result demonstrates the effectiveness and the superiority of the intelligent navigation algorithm based on QLEKF, which can satisfy the high-precision navigation requirements in the cruise phase of the solar system boundary exploration.