Manned Missions Research Articles

DNA break clustering as a predictor of cell death across various radiation qualities: influence of cell size, cell asymmetry, and beam orientation

Abstract Cosmic radiation, composed of high charge and energy (HZE) particles, causes cellular DNA damage that can result in cell death or mutation that can evolve into cancer. In this work, a cell death model is applied to several cell lines exposed to HZE ions spanning a broad range of linear energy transfer (LET) values. We hypothesize that chromatin movement leads to the clustering of multiple double strand breaks (DSB) within one radiation-induced foci (RIF). The survival probability of a cell population is determined by averaging the survival probabilities of individual cells, which is function of the number of pairwise DSB interactions within RIF. The simulation code RITCARD was used to compute DSB. Two clustering approaches were applied to determine the number of RIF per cell. RITCARD outputs were combined with experimental data from four normal human cell lines to derive the model parameters and expand its predictions in response to ions with LET ranging from ~0.2 keV/μm to ~3000 keV/μm. Spherical and ellipsoidal nuclear shapes and two ion beam orientations were modeled to assess the impact of geometrical properties on cell death. The calculated average number of RIF per cell reproduces the saturation trend for high doses and high-LET values that is usually experimentally observed. The cell survival model generates the recognizable bell shape of LET dependence for the relative biological effectiveness (RBE). At low LET, smaller nuclei have lower survival due to increased DNA density and DSB clustering. At high LET, nuclei with a smaller irradiation area—either because of a smaller size or a change in beam orientation—have a higher survival rate due to a change in the distribution of DSB/RIF per cell. If confirmed experimentally, the geometric characteristics of cells would become a significant factor in predicting radiation-induced biological effects. Insight Box: High-charge and energy (HZE) ions are characterized by dense linear energy transfer (LET) that induce unique spatial distributions of DNA damage in cell nuclei that result in a greater biological effect than sparsely ionizing radiation like X-rays. HZE ions are a prominent component of galactic cosmic ray exposure during human spaceflight and specific ions are being used for radiotherapy. Here, we model DNA damage clustering at sub-micrometer scale to predict cell survival. The model is in good agreement with experimental data for a broad range of LET. Notably, the model indicates that nuclear geometry and ion beam orientation affect DNA damage clustering, which reveals their possible role in mediating cell radiosensitivity.

Optimizing lunar regolith beneficiation for ilmenite enrichment

Over the past few years, the international space industry has focused extensively on advancing technologies to enable prolonged human space exploration missions. The primary limiting factor for these endeavors is the spacecraft’s capacity to transport and store essential supplies from Earth to support human life and mission equipment throughout the mission’s duration. In-situ resource utilization (ISRU) is the preferred solution for this challenge. Previous lunar missions have identified the presence of oxygen within the lunar regolith, which is an important resource for human space exploration missions. Oxygen is present in many different minerals within the lunar regolith out of which, ilmenite provides the highest yield of oxygen per unit mass using hydrogen reduction. However, the distribution of ilmenite is neither high nor uniform throughout the lunar surface and therefore, needs beneficiation, which is an important intermediate step for ilmenite-based oxygen production. A regolith beneficiation testbed was developed at DLR Bremen which is a TRL 4 level representation of the technology. The testbed has multiple process parameters that can be adjusted to produce the desired feedstock. This work focuses on the optimization of this testbed to produce a feedstock with higher ilmenite content than the input regolith. The testbed comprises three beneficiation techniques, viz. gravitational, magnetic and electrostatic beneficiation that work sequentially to produce the desired feedstock. The optimized parameter configuration achieved up to three-fold increase in the ilmenite grade relative to the input with about 32 wt% of the total ilmenite being recovered in the enriched output. These experiments have highlighted other underlying factors that influenced the experimental research such as the design of testbed components, system residuals and limited availability for Off-the-shelf components. The observations made from these experiments have also provided insights into the further development of the technology. The work has thus produced evidence for the effectiveness of the beneficiation testbed in producing an enriched feedstock while outlining avenues for future improvements.

Non-destructive real-time analysis of plant metabolite accumulation in radish microgreens under different LED light recipes.

The future of human space missions relies on the ability to provide adequate food resources for astronauts and also to reduce stress due to the environment (microgravity and cosmic radiation). In this context, microgreens have been proposed for the astronaut diet because of their fast-growing time and their high levels of bioactive compounds and nutrients (vitamins, antioxidants, minerals, etc.), which are even higher than mature plants, and are usually consumed as ready-to-eat vegetables. Our study aimed to identify the best light recipe for the soilless cultivation of two cultivars of radish microgreens (Raphanus sativus, green daikon, and rioja improved) harvested eight days after sowing that could be used for space farming. The effects on plant metabolism of three different light emitting diodes (LED) light recipes (L1-20% red, 20% green, 60% blue; L2-40% red, 20% green, 40% blue; L3-60% red, 20% green, 20% blue) were tested on radish microgreens hydroponically grown. A fluorimetric-based technique was used for a real-time non-destructive screening to characterize plant methabolism. The adopted sensors allowed us to quantitatively estimate the fluorescence of flavonols, anthocyanins, and chlorophyll via specific indices verified by standardized spectrophotometric methods. To assess plant growth, morphometric parameters (fresh and dry weight, cotyledon area and weight, hypocotyl length) were analyzed. We observed a statistically significant positive effect on biomass accumulation and productivity for both cultivars grown under the same light recipe (40% blue, 20% green, 40% red). We further investigated how the addition of UV and/or far-red LED lights could have a positive effect on plant metabolite accumulation (anthocyanins and flavonols). These results can help design plant-based bioregenerative life-support systems for long-duration human space exploration, by integrating fluorescence-based non-destructive techniques to monitor the accumulation of metabolites with nutraceutical properties in soilless cultivated microgreens.

Simulated microgravity facilitates stomatal ingression by Salmonella in lettuce and suppresses a biocontrol agent

As human spaceflight increases in duration, cultivation of crops in spaceflight is crucial to protecting human health under microgravity and elevated oxidative stress. Foodborne pathogens (e.g., Salmonella enterica) carried by leafy green vegetables are a significant cause of human disease. Our previous work showed that Salmonella enterica serovar Typhimurium suppresses defensive closure of foliar stomata in lettuce (Lactuca sativa L.) to ingress interior tissues of leaves. While there are no reported occurrences of foodborne disease in spaceflight to date, known foodborne pathogens persist aboard the International Space Station and space-grown lettuce has been colonized by a diverse microbiome including bacterial genera known to contain human pathogens. Interactions between leafy green vegetables and human bacterial pathogens under microgravity conditions present in spaceflight are unknown. Additionally, stomatal dynamics under microgravity conditions need further elucidation. Here, we employ a slow-rotating 2-D clinostat to simulate microgravity upon in-vitro lettuce plants following a foliar inoculation with S. enterica Typhimurium and use confocal microscopy to measure stomatal width in fixed leaf tissue. Our results reveal significant differences in average stomatal aperture width between an unrotated vertical control, plants rotated at 2 revolutions per minute (2 RPM), and 4 RPM, with and without the presence of S. typhimurium. Interestingly, we found stomatal aperture width in the presence of S. typhimurium to be increased under rotation as compared to unrotated inoculated plants. Using confocal Z-stacking, we observed greater average depth of stomatal ingression by S. typhimurium in lettuce under rotation at 4 RPM compared to unrotated and inoculated plants, along with greater in planta populations of S. typhimurium in lettuce rotated at 4 RPM using serial dilution plating of homogenized surface sterilized leaves. Given these findings, we tested the ability of the plant growth-promoting rhizobacteria (PGPR) Bacillus subtilis strain UD1022 to transiently restrict stomatal apertures of lettuce both alone and co-inoculated with S. typhimurium under rotated and unrotated conditions as a means of potentially reducing stomatal ingression by S. typhimurium under simulated microgravity. Surprisingly, rotation at 4 RPM strongly inhibited the ability of UD1022 alone to restrict stomatal apertures and attenuated its efficacy as a biocontrol following co-inoculation with S. typhimurium. Our results highlight potential spaceflight food safety issues unique to production of crops in microgravity conditions and suggest microgravity may dramatically reduce the ability of PGPRs to restrict stomatal apertures.

Digital Twin Technologies for Autonomous Environmental Control and Life Support Systems

Environmental control and life support systems will require enhanced self-awareness and self-sufficiency as human spaceflights are designed to reach further destinations. These requirements have led to the development of autonomous technologies and systems to enable more Earth independence, while at the same time relying more heavily on the knowledge contained in their computational models (as opposed to the knowledge of ground control experts). For environmental control and life support systems, these consist of disparate models often tailored to specific subsystems and use cases, such as temperature control and CO2 removal. Therefore, there is a need for technologies supporting the integration of existing models. We propose to extend existing digital twin frameworks to integrate models and serve as a tool for answering onboard queries during operation. Toward this vision, we identify research directions for three types of technologies: i) streamlining the process of merging information models without redundancies by leveraging model-based systems engineering languages; ii) the calibration of simulation models that requires a better understanding of how to encode domain knowledge into a probabilistic representation of subsystem states and model parameters; and iii) automating the query understanding process and constructing a mapping between information and simulation models.

Fluid simulation for detachment process in magnetic nozzle of magnetoplasma rocket engine

Magnetoplasma rocket engine has a broad application prospect in the deep space exploration, manned space flight and other space missions. The ion energy is converted into the directed velocity in the magnetic nozzle of the engine. The investigation into the detachment process of the plasma with the magnetic field is of great significance for improving the engine propulsion efficiency. However, there are roughly five kinds of physical mechanisms which can all contribute to the detachment process and make the detachment in the magnetic nozzle quite complicated. Furthermore, the ion temperature is much higher than the electron temperature in the magnetic nozzle of the magnetoplasma rocket engine due to the heating effect of the ion cyclotron resonance stage. As a result, previous numerical model which were based on the assumption of cold ions are unapplicable for the simulation of the engine. In this work, a fluid simulation model is developed which is used for simulating the magnetic nozzle in the magnetoplasma rocket engine. The model includes the electron and the ion of single charge. For the characteristics of the magnetoplasma rocket engine, the ion energy equation is added into the governing equations. In order to analyze the effect of the inertial detachment, the static electric field due to the charge separation is also included. The simulations are performed under the conditions of different inlet ion temperatures and background magnetic fields. The results show that the ion axial velocity gradually increases in the magnetic nozzle and the ion stream lines detach from the magnetic field lines gradually. The loss of adiabaticity is the dominant mechanism in the detachment process. The ion axial velocity increases with the inlet ion temperature rising, and the ion streamlines detach earlier from the magnetic field lines. The resistive diffusion is unaffected by the inlet ion temperature while the detachment interfaces of other three mechanisms all move toward the upstream. With the increase of the background magnetic field, ion axial velocity decreases and the angle included between the streamline and the axis becomes smaller. The loss of adiabaticity is still the dominant physical mechanism when the magnetic field is changed.

Terminological correctness of the information environment through the eyes of physicists

The incorrectness of the concepts of "information society" and "information civilization" is considered, the justification of which is given by the author on the basis of the development of the information space and information technologies. It is shown that the use of these terms is one of the elements of the program of globalism, which threatens the transformation of the world space with the disappearance of nation-states and the domination of a transnational government. The latest trends in physical science are identified, where questions are raised about the importance of synthesizing quantum theory and general relativity with the existing problem of the possibility of combining local and non-local observations, the hypothesis of the existence of information fields. The integration of educational technologies is designed to show that the development of the information space is an important step in civilization, but humanity also faces more global challenges about the place and mission of Man in this world.

Far-red light photoacclimation in a desert Chroococcidiopsis strain with a reduced FaRLiP gene cluster and expression of its chlorophyll f synthase in space-resistant isolates.

Some cyanobacteria can use far-red light (FRL) to drive oxygenic photosynthesis, a phenomenon known as Far-Red Light Photoacclimation (FaRLiP). It can expand photosynthetically active radiation beyond the visible light (VL) range. Therefore, it holds promise for biotechnological applications and may prove useful for the future human exploration of outer space. Typically, FaRLiP relies on a cluster of ~20 genes, encoding paralogs of the standard photosynthetic machinery. One of them, a highly divergent D1 gene known as chlF (or psbA4), is the synthase responsible for the formation of the FRL-absorbing chlorophyll f (Chl f) that is essential for FaRLiP. The minimum gene set required for this phenotype is unclear. The desert cyanobacterium Chroococcidiopsis sp. CCMEE 010 is unusual in being capable of FaRLiP with a reduced gene cluster (15 genes), and it lacks most of the genes encoding FR-Photosystem I. Here we investigated whether the reduced gene cluster of Chroococcidiopsis sp. CCMEE 010 is transcriptionally regulated by FRL and characterized the spectral changes that occur during the FaRLiP response of Chroococcidiopsis sp. CCMEE 010. In addition, the heterologous expression of the Chl f synthase from CCMEE 010 was attempted in three closely related desert strains of Chroococcidiopsis. All 15 genes of the FaRLiP cluster were preferentially expressed under FRL, accompanied by a progressive red-shift of the photosynthetic absorption spectrum. The Chl f synthase from CCMEE 010 was successfully expressed in two desert strains of Chroococcidiopsis and transformants could be selected in both VL and FRL. In Chroococcidiopsis sp. CCME 010, all the far-red genes of the unusually reduced FaRLiP cluster, are transcriptionally regulated by FRL and two closely related desert strains heterologously expressing the chlF010 gene could grow in FRL. Since the transformation hosts had been reported to survive outer space conditions, such an achievement lays the foundation toward novel cyanobacteria-based technologies to support human space exploration.

Artificial gravity in heat and mass exchange apparatus for the life support system of manned space missions

Different water recovery systems for deep space flight are analyzed; the existing systems and their shortcomings are briefly shown. The construction of a centrifugal mass transfer apparatus is presented, it could work in weightlessness conditions. The experimental data for the centrifugal apparatus in the mode of separation of the gas and liquid mixture are presented. The pressure was about 8 meters of water column for proposed construction. The formula for calculating the pressure for a scoop pump is given, which takes into account the rotation frequency, volume flow rate, the geometric dimensions and location of the scoop. Principle schemes for using a new centrifugal mass exchange device for water recovery systems and for capturing atmospheric moisture condensate are proposed. The features of the proposed schemes are analyzed and their potential advantages are determined. The main tasks for future experimental studies of the heat and mass transfer centrifugal apparatus are defined.

Highly sensitive detection of a neurodegenerative protein biomarker by using the pyro-electrohydrodynamic jet

A set of protein biomarkers are largely recognized as responsible of neurodegeneration mechanisms and hence as potential targets to be detected in low abundant concentrations in body fluids for performing early diagnosis. As an example, the Tau protein experiences a transition phase from a native disorder conformation into a preaggregation state, which leads to fibrillization processes. Here we show the possibility to detect Tau in urine samples at sub-picogram level, through the concentration effect of the pyro-electrohydrodynamic (p-jet) technique. An immunofluorescence protocol is applied to concentrated p-jet spots able to reduce drastically the diffusion effects in the antibody-antigen reaction. A set of diluted samples were prepared, and the fluorescence signal was detected by a confocal scanner. We achieved an excellent linear response with a significant signal-to-noise ratio down to 0.25 pg/mL. In perspective, the technique could be integrated into a compact device to be used for monitoring the early stage associated to neurodegenerative syndromes in different scenarios such as for example in long-term human space exploration missions.

The Apollo-Soyuz Experimental Flight as a Political, Scientific and Technical Detente Project (On Materials from Russian Archives)

The Détente Era — as political defusing of international tensions in the 1960s and 1970s — represents an interesting period in World History. The study of this era has a special appeal in connection with the experience of positive political, scientific and technical interaction between two superpowers: the USSR and the United States, — an experience that lacks at present days. One of the brightest symbols of the Détente was the joint Soviet-American space experimental program “Apollo-Soyuz Test Project” (ASTP), within the framework of which joint docking of spacecraft in orbital space was carried out. Based on documents from the Archive of Foreign Policy of the Russian Federation, the Russian State Archive of Contemporary History and other published sources, including American ones, the article examines the history of the ASTP program as an important element of cooperation between superpowers in space during the years of detente. Special attention is paid to the factors that led to the beginning of cooperation, as well as the reasons why the docking of Soyuz and Apollo was not followed by projects comparable in scale and brightness. The authors come to two key conclusions. Firstly, the ASTP program, which arose as a purely scientific and technical project arising from the urgent tasks of developing manned space exploration, was inscribed in 1972 into the general agenda of bilateral relations between Moscow and Washington and became a politically significant project for both sides, the value of which was not directly related to its scientific and technical content. Secondly, the history of the ASTP clearly reflected the specifics of bilateral relations in the context of detente — both sides sought cooperation, but at the same time had clear limits of permissible actions and concessions, for which they did not go over.

Long‐Term Variation of the Galactic Cosmic Ray Radiation Dose Rates

AbstractIn this work, a model for calculating the galactic cosmic rays (GCRs) radiation dose rate is developed. The model is based on a GCR modulation model, which is established by Shen and Qin, and the fluence‐dose conversion coefficients (FDCCs) published by the International Commission on Radiological Protection (ICRP). With the model, the radiation absorbed dose rate of GCRs near the lunar surface over long time periods is calculated and compared with the observation data from the Cosmic Ray Telescope for the Effects of Radiation and the Lunar Lander Neutron and Dosimetry. First, the energy spectrum of GCRs at 1 AU in the ecliptic, where the lunar orbit is located, is computed using the GCR modulation model. Then, using the FDCCs of ICRP 123, the absorbed dose rates of 15 human organs/tissues at the lunar orbit position are calculated to represent the general absorbed dose rate of the body (in water). Furthermore, considering the albedo radiation (excluding neutrons) and using the water‐silicon conversion coefficients, the total absorbed dose rates of GCRs near the lunar surface (in silicon) are calculated, it is shown that our modeling results generally agree with the observations from spacecraft. This work is useful for future manned space exploration to the Moon or other celestial bodies in the solar system.

The Effects of Simulated and Real Microgravity on Vascular Smooth Muscle Cells

Abstract As considerations are being made for the limitations and safety of long-term human spaceflight, the vasculature is important given its connection to and impact on numerous organ systems. As a major constituent of blood vessels, vascular smooth muscle cells are of interest due to their influence over vascular tone and function. Additionally, vascular smooth muscle cells are responsive to pressure and flow changes. Therefore, alterations in these parameters under conditions of microgravity can be functionally disruptive. As such, here we review and discuss the existing literature that assesses the effects of microgravity, both actual and simulated, on smooth muscle cells. This includes the various methods for achieving or simulating microgravity, the animal models or cells used, and the various durations of microgravity assessed. We also discuss the various reported findings in the field, which include changes to cell proliferation, gene expression and phenotypic shifts, and renin-angiotensin-aldosterone system (RAAS), nitric oxide synthase (NOS), and Ca2+ signaling. Additionally, we briefly summarize the literature on smooth muscle tissue engineering in microgravity as well as considerations of radiation as another key component of spaceflight to contextualize spaceflight experiments, which by their nature include radiation exposure. Finally, we provide general recommendations based on the existing literature's focus and limitations.

Analysis of Electric Sensor for Space Detectors: Mass Spectrometer, Particle Detector and CMOS/CCD Sensor

As a matter of fact, with the participation of government agencies and the exploration of private enterprises, space exploration is undergoing rapid development as well as change in recent years. With this in mind, these trends will continue to promote human exploration and utilization of space, providing more opportunities for scientific research, commercial applications and exploration. In order to realize accuracy observation, high precision detectors are necessary to be developed and implemented. To be specific, a large number of electric sensors are applied on the space detectors, including mass spectrometer, particle detector as well as CMOS/CCD image sensor, etc. On this basis, this paper presents the principles, structures and applications of these three electric sensors in detail. According to the analysis, this study also analyzes the existing shortcomings of the state-of-art facilities as well as proposes future developments. Overall, these results shed light on guiding further exploration of space detectors.

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.

Exploring Frontiers: Interdisciplinary Insights into Human Space Flight Advancements

This review article comprehensively examines the multifaceted landscape of human space flight, focusing on the transformative role of the International Space Station (ISS) and the evolving challenges and opportunities associated with deep space exploration. Anchored in the synergy between space science, engineering, and human physiology, our exploration unfolds across key domains, shedding light on the scientific, technological, and psychological dimensions of human space missions.

A Comprehensive Overview of ISRO's Ambitious Space Station Project and Collaborative Endeavors

The Bharatiya Antariksha Station, colloquially known as the Indian Space Station (ISS), symbolizes India's ambitious foray into space exploration. Proposed and operated by the Indian Space Research Organisation (ISRO), the station is designed to weigh 20 tonnes, orbiting approximately 400 kilometers above Earth. Intended for accommodating astronauts for up to 20 days, it fosters scientific research and technological advancements. Originally slated for completion by 2030, delays ensued due to challenges in the Gaganyaan mission and the global COVID-19 pandemic, pushing the target year to 2035. ISRO Chief K. Sivan unveiled the space station details in 2019, and in 2022, highlighted progress in the Gaganyaan project. The space station's development aligns with India's broader space exploration goals, with an ambitious timeline spanning the next two to two-and-a-half decades, encompassing human spaceflight and lunar exploration by 2040. In a noteworthy development, NASA Administrator Bill Nelson expressed NASA's readiness to collaborate on a commercial space station by 2040 during his 2023 visit to India. As of December 28, 2023, ISRO Chief S. Somanath reiterated ISRO's commitment to a comprehensive roadmap until 2047, encompassing a space station, lunar exploration, and Moon-based economic activities. This strategic vision underscores India's dedication to advancing space exploration and technology. The Bharatiya Antariksha Station stands as a testament to ISRO's growing capabilities, poised to contribute significantly to scientific discovery and international collaboration in the evolving landscape of human space exploration.

Thriving on Mars: Potatoes as the Answer to Martian Challenges

Humans have committed themselves to the exploration of space and the quest for a habitable planet. Central to the development of a sustainable ecosystem that can provide essential resources like food and water is the implementation of space plant cultivation systems. In the pursuit of bio-regenerative life support systems for human space exploration, the inclusion of plants is imperative. This study focuses on assessing potential challenges associated with cultivating Potatoes (Solanum tuberosum) under simulated Martian conditions. Potatoes exhibit adaptability to extremely cold and dry environments, making them a promising candidate for extraterrestrial agriculture. The advantages of potatoes include their high yield, rich content of easily digestible carbohydrates, elevated protein levels, and simplicity of propagation. When induced to tuberize, potatoes can achieve a harvest index exceeding 80%, approximately double that of traditional grain crops. Notably, unlike certain crops such as soybeans and certain grains, potatoes do not necessitate elaborate processing procedures before consumption. The Potato, specifically varieties like Norland, Denali, and Russet Burbank, has garnered attention in research funded by the US National Aeronautics and Space Administration (NASA). Tests have revealed that these cultivars can successfully undergo tuberization even under constant bright light conditions, emphasizing their potential suitability for life support functions in space exploration contexts

Experimentally backed model of bubbly flow in a CNTP reactor

Centrifugal Nuclear Thermal Propulsion is a second-generation propulsion concept currently being researched to succeed traditional solid core nuclear thermal propulsion. Current efforts across the space industry are focusing on development of technologies for enabling manned flight to Mars and scientific missions to the outer planets. To enable these types of mission's direct injection trajectories are needed to decrease exposure to astronauts and scientific payloads to the harsh environment of space. Current efforts in nuclear thermal propulsion have shown great promise in higher specific impulses ∼900 s, but even these levels of specific impulse fall short for manned Mars missions with durations less than two years or direct injection to orbit of the outer ice giants Uranus and Neptune without the use of gravity assists. High performance nuclear thermal propulsion has been proposed using bubble through nuclear reactors to reach specific impulses as high as 1800 s, however significant challenges exist to prove the feasibility of such a system. One of the major challenges is the fluid mechanics within the core of the engine since little is known about uranium in the liquid phase. An experimental study has been conducted to better understand the fluid dynamics to better inform the thermodynamic and nucleonic models. Using the data from the experiment, high-fidelity simulations have been developed to predict the fluid dynamics of the uranium fuel. This information can then be further fed into thermodynamics models in development to predict core temperatures and system behaviour. The validated models show that small bubbles reach thermal equilibrium, and high centrifugal forces and surface tension assist in confining the molten uranium within the reactor core. Injector methods suggest feasible configurations to encourage bubble flow while minimizing backflow of the propellant, motivating further study of Centrifugal Nuclear Thermal Propulsion based systems.

Back to the Moon ... to stay?

Despite a lack of public enthusiasm, NASA’s Artemis program will endure because human spaceflight has strong congressional support and signals great-power status.