Manned Deep Space Exploration Research Articles

Design of Entire-Flight Pinpoint Return Trajectory for Lunar DRO via Deep Neural Network

Lunar DRO pinpoint return is the final stage of manned deep space exploration via a lunar DRO station. A re-entry capsule suffers from complicated dynamic and thermal effects during an entire flight. The optimization of the lunar DRO return trajectory exhibits strong non-linearity. To obtain a global optimal return trajectory, an entire-flight lunar DRO pinpoint return model including a Moon–Earth transfer stage and an Earth atmosphere re-entry stage is constructed. A re-entry point on the atmosphere boundary is introduced to connect these two stages. Then, an entire-flight global optimization framework for lunar DRO pinpoint return is developed. The design of the entire-flight return trajectory is simplified as the optimization of the re-entry point. Moreover, to further improve the design efficiency, a rapid landing point prediction method for the Earth re-entry is developed based on a deep neural network. This predicting network maps the re-entry point in the atmosphere and the landing point on Earth with respect to optimal control re-entry trajectories. Numerical simulations validate the optimization accuracy and efficiency of the proposed methods. The entire-flight return trajectory achieves a high accuracy of the landing point and low fuel consumption.

Effect of finned configuration of circular tube based on fluid-structure coupling on hydrogen flow characteristics

Nuclear thermal propulsion has the characteristics of high specific impulse, large thrust, green and efficient, and is the primary choice of manned deep space exploration propulsion system. Because the circulating flow of propellant hydrogen in the internal pipeline of the engine is always affected by the harsh environment of high temperature and high pressure, it is very important to study the flow characteristics of hydrogen in the pipeline, the heat exchange characteristics of hydrogen and pipeline and the deformation characteristics of pipeline under heat stress. In this paper, the flow phenomena of hot hydrogen in round tubes in a laminar flow state were analyzed by numerical simulation with COMSOL Mulitiphisics6.0, and the fluid-structure coupling between hot hydrogen fluid and pipe was investigated by a multi-physics field. It is concluded that the smoother the inner wall of the pipeline is, the smaller the hydrogen flow velocity is, the smaller the surface pressure of the pipe wall is, and the smaller the fluid extrusion and impact deformation of the pipe in the typical pipe with the inner fin is. It inspires studying the application of hot hydrogen flow and pipeline configuration in nuclear thermal rocket engines, including improving heat transfer energy and uniformity.

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.

Progress in Lightweight Design Methods for Large-Size Panel Structures in Manned Pressurized Capsules

The pressurized capsule structure provides the pressure environment for astronauts or payloads in space, which is thus considered as the most crucial structural component for manned spacecraft. The manned deep space exploration mission (MDSEM) brings new challenges to the pressurized capsule structure: extremely low structural weight, long service life, reusability and adaptability to the harsh deep space environment. The conventional welded panel pressurized capsule structure (WPPCS) is not able to meet these new requirements. To address the above challenges, this paper comprehensively expounds why the current WPPCS cannot meet the requirements of MDSEMs based on the analysis of the vibration environment and structural characteristics of the pressurized capsule structure. Furthermore, a new type of integrated panel pressurized capsule structure (IPPCS) is proposed, showing the lightweight advantage compared with WPPCS. Finally, the technical details and research results of the strength criterion, design method, material upgrading and structural integrity manufacturing process of the IPPCS are fully introduced. The conclusions drawn in this paper will provide useful and meaningful references for the future development of large-size, lightweight pressurized capsule structures.

Positive mood-related gut microbiota in a long-term closed environment: a multiomics study based on the “Lunar Palace 365” experiment

BackgroundPsychological health risk is one of the most severe and complex risks in manned deep-space exploration and long-term closed environments. Recently, with the in-depth research of the microbiota–gut–brain axis, gut microbiota has been considered a new approach to maintain and improve psychological health. However, the correlation between gut microbiota and psychological changes inside long-term closed environments is still poorly understood. Herein, we used the “Lunar Palace 365” mission, a 1-year-long isolation study in the Lunar Palace 1 (a closed manned Bioregenerative Life Support System facility with excellent performance), to investigate the correlation between gut microbiota and psychological changes, in order to find some new potential psychobiotics to maintain and improve the psychological health of crew members.ResultsWe report some altered gut microbiota that were associated with psychological changes in the long-term closed environment. Four potential psychobiotics (Bacteroides uniformis, Roseburia inulinivorans, Eubacterium rectale, and Faecalibacterium prausnitzii) were identified. On the basis of metagenomic, metaproteomic, and metabolomic analyses, the four potential psychobiotics improved mood mainly through three pathways related to nervous system functions: first, by fermenting dietary fibers, they may produce short-chain fatty acids, such as butyric and propionic acids; second, they may regulate amino acid metabolism pathways of aspartic acid, glutamic acid, tryptophan, etc. (e.g., converting glutamic acid to gamma–aminobutyric acid; converting tryptophan to serotonin, kynurenic acid, or tryptamine); and third, they may regulate other pathways, such as taurine and cortisol metabolism. Furthermore, the results of animal experiments confirmed the positive regulatory effect and mechanism of these potential psychobiotics on mood.ConclusionsThese observations reveal that gut microbiota contributed to a robust effect on the maintenance and improvement of mental health in a long-term closed environment. Our findings represent a key step towards a better understanding the role of the gut microbiome in mammalian mental health during space flight and provide a basis for future efforts to develop microbiota-based countermeasures that mitigate risks to crew mental health during future long-term human space expeditions on the moon or Mars. This study also provides an essential reference for future applications of psychobiotics to neuropsychiatric treatments.3wJ6S91ppJCbbcXcW_ZHEyVideo

Extraterrestrial photosynthesis by Chang’E-5 lunar soil

<h2>Summary</h2> In light of significant efforts being taken toward manned deep space exploration, it is of high technological importance and scientific interest to develop the lunar life support system for long-term exploration. Lunar <i>in situ</i> resource utilization offers a great opportunity to provide the material basis of life support for lunar habitation and traveling. Based on the analysis of the structure and composition, Chang'E-5 lunar soil sample has the potential for lunar solar energy conversion, i.e., extraterrestrial photosynthetic catalysts. By evaluating the performance of the Chang'E-5 lunar sample as photovoltaic-driven electrocatalyst, photocatalyst, and photothermal catalyst, full water splitting and CO₂ conversion are able to be achieved by solar energy, water, and lunar soil, with a range of target product for lunar life, including O₂, H₂, CH₄, and CH₃OH. Thus, we propose a potentially available extraterrestrial photosynthesis pathway on the moon, which will help us to achieve a "zero-energy consumption" extraterrestrial life support system.

MOSCOW INTERNATIONAL SYMPOSIA ON SOLAR SYSTEM RESEARCH (10M-S3 AND 11M-S3) REPORTS REVIEW. Part 1. Mars exploration

A review of the reports of the last two Moscow International Symposia on Solar System Research has been completed. In the first part of the review, 43 reports of the main session of the "Mars" section are considered. The works of leading experts in the field of planetary science cover a wide range of scientific and applied problems - from the study of the geological history and climate of Mars, the search for traces of life and subsurface water reserves, to new technologies in planetary research, mission planning, as well as monitoring solar activity and radiation conditions in the interplanetary space, orbit and the surface of Mars. The data obtained in the last two decades has made it possible to significantly advance in understanding the nature of Mars, but many unresolved questions remain regarding the climate in the early era, the existence of the Martian oceans in the past, biological and geological activity. The scientific results obtained by unmanned spacecraft should be fully taken into account in the development of manned deep space exploration programs. Key words: Solar system, planetology, international symposium, deep space, automatic interplanetary stations, Mars, Moon, reports review

A Membrane Reactor with Microchannels for Carbon Dioxide Reduction in Extraterrestrial Space

Long-term continuous oxygen supply is of vital importance during the process of space exploration. Considering the cost and feasibility, in situ resource utilization (ISRU) may be a promising solution. The conversion of CO2 to O2 is a key point for ISRU. In addition, the utilization of the abundant CO2 resources in the atmosphere of Mars is an important topic in the field of manned deep space exploration. The Sabatier reaction, Bosch reaction, and solid oxide electrolysis (SOE) are well-known techniques for the reduction of CO2. However, all the above techniques need great energy consumption. In this article, we designed an electrochemical membrane reactor at room temperature based on microfluidic control for the reduction of CO2 in extraterrestrial space. In this system, H2O was oxidized to O2 on the anode, while CO2 was reduced to C2H4 on the cathode. The highest Faraday efficiency (FE) for C2H4 was 72.7%, with a single-pass carbon efficiency toward C2H4 (SPCE-C2H4) of 4.64%. In addition, a microfluidic control technique was adopted to overcome the influence of the microgravity environment. The study may provide a solution for the long-term continuous oxygen supply during the process of space exploration.

A publish-subscribe networking architecture for future manned deep space exploration

With the further development of the Deep Space Networking (DSN), more and more satellites and space probes will be put into space which makes the DSN more diverse and complex. We argued that Information Centric Networking (ICN) may be a suitable architecture for the DSN. In this paper, a publish-subscribe networking architecture based on ICN is proposed for future manned deep space exploration network. It adopts the publish-subscribe mechanism and decouples the control plane and data plane logically. In the proposed architecture, the improvement of routing is made to tolerant the long propagation delay and frequent link disruptions of deep space. And the multi-source transmission is considered to deal with the large amount of data in the future manned deep space exploration network. We evaluated the feasibility of the architecture and the performance of the protocol stack, the improved routing mechanism and the multi-source transmission. The results indicate that Publish-Subscribe Networking (PSN) can cope with the harsh transmission conditions, and the multi-source transmission can reduce the delivery time of data. It enables the network to allocate and share resources more efficiently and keeps the network well managed.

Psychophysiological and cognitive effects of strawberry plants on people in isolated environments.

In manned deep-space exploration, extremely isolated environments may adversely affect the mood and cognition of astronauts. Horticultural plants and activities have been proven to be effective in improving their physical, psychological, and cognitive states. To assess the effects of applying horticultural plants and activities in isolated environments, this study investigated the influence of viewing strawberry plants on the mood of people in a laboratory experiment as indicated by heart rate, salivary cortisol, and psychological scales. The results showed that heart rate and salivary cortisol were significantly decreased after viewing strawberry plants for 15 min. "Tension" and "confusion" scored using the Profile of Mood States negative mood subscales, and anxiety levels measured using the State-Trait Anxiety Inventory scale were also significantly reduced. This study further explored the impact of viewing strawberry plants on cognition. A notable reduction of the subjects' reaction time after 15-min plant viewing was observed. Based on these findings, a long-duration isolated experiment in a bioregenerative life support system-"Lunar Palace I"-was conducted. A similar trend was obtained that crew members' mood states were improved by viewing the strawberry plants, but no significant change was observed. This study provided some experimental evidence for the benefits of interacting with strawberry plants in isolated environments.

Thermal performance optimization of a fuel element in particle bed reactors for nuclear thermal propulsion

Nuclear Thermal Propulsion (NTP) provides the leading potential due to its high thrust, improved specific impulse and long accumulated lifetime in the manned deep space exploration. Particle Bed Reactor (PBR) is the most efficient one among all proposed NTP concepts, which employs a radial flow pattern to reduce the pressure drop and fuel particles of high surface-to-volume ratio to increase the heat removal capability. The technical challenges, however, have arisen with the enhanced performance of PBR, such as the thermal hydraulic design. In this paper, a procedure based on the Non-dominated Sorting Genetic Algorithm with elitisms approach (NSGA-2) and uncertainty quantification is developed to prepare an optimal fuel element for PBR with regard to the thermal performance. The procedure has been verified through three cases, in which the thermal performance of all fuel elements has improved a lot after the optimization process.

Research progress of space radiation protection technologies in manned deep space exploration missions

Unlike the low-Earth orbit (LEO) project, space radiation, mainly coming from galactic cosmic radiation (GCR) and solar particle event (SPE), has been generally considered to be one of the most important health risk factors for astronauts in manned deep space exploration missions. In fact, space radiation environment in deep space is substantially different from that in low Earth orbit, in which high-energy protons and heavy nuclei provide the main contribution to the equivalent dose and health risk. Both the total equivalent dose and health risk in deep space are significantly higher than those in LEO missions, which may exceed the permissible radiation exposure limits in the career of astronauts. And, health risks from space radiation exposure remain a primary concern for manned deep space explorations. Space radiation protection is an important strategy to reduce astronauts’ risks of damage and disease induced by space radiation and ensure their health and safety in manned deep space exploration missions. Therefore, space radiation protection is considered to be an important technical problem to be solved in the further manned spaceflight project. However, the complexity and particularity of space radiation environment in manned deep space exploration missions make space radiation protection extremely difficult. Based on the analysis of space radiation environment characteristics in manned deep space exploration missions, this review systematically summarizes and analyzes the current research progresses of space radiation protection, including physical protection and biomedical protection. In general, the physical protection refers to the passive shielding and acitve shielding. The passive shielding of materials with different thickness is the simplest and feasible physical countermeasure to deal with deep space radiation, especially in the case of SPE occurrences. The passive shielding technologies were raised and reviewed from four aspects, including radiation shielding performance indexes and their applications in new material selections, manned spacecraft radiation shielding, personal radiation shielding, and astral surface soil radiation shielding. However, the passive shielding is problematic for GCR due to the penetration of primary high-energy particles, the production of secondary radiation and the mass constraints of manned spacecraft. While, active shielding, involving the generation of electromagnetic fields to deflect space radiation, is a promising and interesting technical improvement to overcome challenging technical hindrance to prevent GCR. But different kinds of active shielding technologies, such as electrostatic shielding, plasma shielding, confined and unconfined magnetic field shielding, have not been applicable in practical cases. Moreover, a series of radioprotectors and radiomitigators in the biomedical protection, including (1) antioxidants, (2) inhibitors of various pathways, (3) cytokines, chemokines, growth factors and hormones, (4) protein molecules, (5) cellular therapeutic agents, and (6) plant derived products, were also summarized and reviewed. Most radioprotectors and radiomitigators are currently being researched and developed under early preclinical phase, and have not been approved by the food and drug administrations. At the same time, the deficiency of some present radioprotectors and radiomitigators, such as the unclear biomedical mechanisms and unavoidable side-effects, limited the popularity in actual applications. In a word, the review points out that the current space radiation protection technologies still face a series of problems and challenges, and puts forward the key technologies and countermeasures of the current space radiation protection. The summary and analysis of the critical challenges and key countermeasures of space radiation protection are of great significance for the follow-up researches and provide a theoretical basis and a solution for the implementation of manned deep space exploration mission.

Nuclear microbomb propulsion for manned deep space exploration with return travel

For manned deep space exploration with return travel a novel nuclear microbomb propulsion concept is proposed. It assumes the presence of easily mineable natural uranium and lithium deposits on Solar System planets. The concept makes use of large negative mass densities in a rapidly rotating reference system predicted by Hund as a consequence of Einstein's general theory of relativity. It permits the ignition of the deuterium thermonuclear reaction by the implosion of Li6D salt inside a rapidly rotating natural uranium shell by an intense relativistic electron beam of over 100 MJ. This concept avoids the drawbacks of carrying along liquid deuterium-tritium and Plutonium 239 or Uranium 235 for fission spark plugs on a deep space mission.The generation of the pulsed high-energy relativistic beams can be done by solar collectors charging the high-voltage Marx generators, or by a small natural uranium reactor, requiring not much more than a small chemical factory, not a large isotope separating facility. A small chemical plant is also needed to make the high explosives used to achieve the large rotational target velocity.

Exergy analysis of a lunar based solar thermal power system with finite-time thermodynamics

Abstract The exploration of the moon and the construction of the manned lunar outpost are the important parts of the deep space exploration. The continuous supply of thermal energy and power for deep space explorers and scientific equipment is a crucial issue to accomplish manned lunar missions. For most locations on the lunar surface, darkness lasts for periods of about 350 hours, so it is a great challenge for the solar photovoltaic cells and radioisotope thermoelectric generators to launch too much material from Earth. In the mission of manned deep space exploration, it is very necessary to utilize in situ resource effectively and sufficiently to reduce the hardware must be brought from Earth and to meet the requirement of energy and life support system. This paper describes an exergy analysis of a lunar based solar thermal power system using the method of finite-time thermodynamics. The calculations indicate that the system can provide the desired energy for the equipment. The aim of this article is to provide the basis for the design of a solar-powered Stirling engine using thermal energy from the processed lunar regolith.

Issues and challenges of space radiation risk assessment in manned deep space exploration missions

The plan and implementation of manned deep space exploration missions should first ensure the health and safety of astronauts. Space radiation, mainly coming from galactic cosmic rays (GCR), solar particle events (SPE) and trapped belt radiation (TBR), has been generally considered to be one of the most important risk factors threatening the health of astronauts in deep spaceflight missions. Health risks from these exposures mainly include four aspects: carcinogenesis, acute radiation syndrome, central nervous system damage and degenerative tissue effects, and the risk of carcinogenesis remains a primary concern for manned deep space explorations. The difference in the radiation environment between the deep space and the ground leads to a high uncertainty on the estimated health risk, which is currently the main hindrance to manned interplanetary exploration. The issues and challenges related to health risk assessment of space radiation for astronauts during manned deep space exploration missions are systematically summarized and analyzed in this paper. Six main issues were raised in space radiation risk assessment, including estimation of space radiation quality, extrapolation of low-dose/dose-rate radiation risk, prediction of dose- and dose-rate reduction effectiveness factor (DDREF), screening of differences in individual radiosensitivity, effects of microgravity and other stressors on space radiation risk, and assessment of acute radiation syndromes caused by SPE. In addition, six corresponding key technologies were also discussed to address these scientific issues and challenges for future studies and practice: (1) The more dose-response data in experimental animals is needed for estimating the relative biological effectiveness (RBE) for different high-energy charged (HZE) particle types in different tissues. (2) The improved radiobiological models including targeted and non-targeted effects models, are required for accurately estimating space radiation quality factors. (3) It is necessary to accurately estimate the DDREF for low dose and dose-rate radiations, and it should be further comfirmed whether the linear-no-threshold (LNT) model is the most appropriate way to extrapolate risk estimates in low dose and dose-rate through more relevant theoretical and experimental researches. (4) The biomarker selection techniques are important to identify the potential biomarkers associated with space radiation, and the integrated risk assessment models based on the space radiation sensitive biomarkers using systems biology approaches can improve the accuracy of predicting individual radiosensitivities and disease risks induced by space radiation. (5) The influence of microgravity and other stressors on space radiation risk need to be further investigated. (6) More accurate SPE prediction models and the corresponding acute radiation risk assessment models are also necessary in further studies. The goal of reducing the uncertainties in space radiation risk assessment can be fulfilled by an international co-operative effort in these critical technologies. The arrangement and analysis of the critical issues and key technologies of space radiation risk assessment in manned deep space exploration missions can provide the strategies of reducing the health risk of astronauts induced by space radiation.

Carbon dioxide splitting using an electro-thermochemical hybrid looping strategy

Reclaiming oxygen (O2) efficiently from carbon dioxide (CO2), a major product of human metabolism, is a key technology to minimize the oxygen supply required for challenging missions such as manned deep space exploration.

Review of Nuclear Thermal Propulsion Technology Development

NTP(Nuclear Thermal Propulsion)has special features of high specific impulse,powerful force and long operating time. NTP could be used for manned deep space exploration and large-scale cargo shipment between stars. The NTP research history and technology development in America and Russia are introduced in this paper. The trends of NTP development are summarized,namely medium thrust engine,modularized reactor core,high performance fuel element,non-nuclear experiment method and multiple function design. The key technologies of reactor design,nuclear safety protection design,fuel preparation,fuel element manufacture,exhaust handling,and engine startup,are analyzed. At last,some suggestions for NTP development in China are given,including cooperation between nuclear and aerospace industries,drawing lessons from American and Russian experiences and initiating research work as soon as possible.

Key Problems of Space Environmental Engineering for Manned Deep Space Exploration Mission

Space environments such as solar cosmic ray, galactic cosmic ray, microgravity, dust and dust storm, deep space microbe and so on, which will be encountered during the course of manned deep space exploration, are firstly introduced. Then, the threat of different deep space environments to the astronauts is discussed, and some countermeasures such as physical protection, monitoring and early warning of radiation risks, radiation protection drugs, astronaut selection, etc, is given. Finally, the further work should be done for manned deep space mission, which includes damage mechanism of space radiation on the astronaut, development of drug against space radiation and microgravity, protection of structure and material from space radiation environments, self cleaning materials and technology for space suit, research and development of materials against microbial erosion, etc, are discussed.

Does the worsening galactic cosmic radiation environment observed by CRaTER preclude future manned deep space exploration?

AbstractThe Sun and its solar wind are currently exhibiting extremely low densities and magnetic field strengths, representing states that have never been observed during the space age. The highly abnormal solar activity between cycles 23 and 24 has caused the longest solar minimum in over 80 years and continues into the unusually small solar maximum of cycle 24. As a result of the remarkably weak solar activity, we have also observed the highest fluxes of galactic cosmic rays in the space age and relatively small solar energetic particle events. We use observations from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter to examine the implications of these highly unusual solar conditions for human space exploration. We show that while these conditions are not a show stopper for long‐duration missions (e.g., to the Moon, an asteroid, or Mars), galactic cosmic ray radiation remains a significant and worsening factor that limits mission durations. While solar energetic particle events in cycle 24 present some hazard, the accumulated doses for astronauts behind 10 g/cm2 shielding are well below current dose limits. Galactic cosmic radiation presents a more significant challenge: the time to 3% risk of exposure‐induced death (REID) in interplanetary space was less than 400 days for a 30 year old male and less than 300 days for a 30 year old female in the last cycle 23–24 minimum. The time to 3% REID is estimated to be ∼20% lower in the coming cycle 24–25 minimum. If the heliospheric magnetic field continues to weaken over time, as is likely, then allowable mission durations will decrease correspondingly. Thus, we estimate exposures in extreme solar minimum conditions and the corresponding effects on allowable durations.

Bi-Directional Excitation of Radio Frequency Waves Using a Helical Antenna in Non-Uniform Plasmas towards a Compact Magnetoplasma Thruster

Magnetoplasma thruster is one of the attractive plasma engines for space propulsion in future manned deep space exploration. Usually two helical antennas are equipped to produce and heat plasmas with separate radio frequency sources. It is presented in this paper that a helical antenna, which is used to launch one wave mode in one direction so far, exhibits bi-directional nature, where the waves with different mode numbers are launched and couple with electrons and ions selectively in opposite directions. A two-dimensional numerical calculation is performed to predict wave propagation and power absorption in a non-uniform hydrogen plasma immersed in a non-uniform external static magnetic field, based on the hot plasma theory. It is confirmed that appropriate choice of the excitation condition of the antenna can select axial propagation direction of specific wave modes and consequently select a species that absorbs power from generated waves. A small-scale experiment is performed to confirm the prediction of the calculation. By measuring a change in electron and ion temperatures due to the wave launch from the helical antenna, it is found that both the production and heating at different axial positions are accomplished simultaneously by one antenna showing that another type of the radio frequency driven magnetoplasma thruster would be achieved.