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        <title>Frontiers in Space Technologies | Microgravity section | New and Recent Articles</title>
        <link>https://www.frontiersin.org/journals/space-technologies/sections/microgravity</link>
        <description>RSS Feed for Microgravity section in the Frontiers in Space Technologies journal | New and Recent Articles</description>
        <language>en-us</language>
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        <pubDate>2026-04-13T15:41:40.466+00:00</pubDate>
        <ttl>60</ttl>
        <item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2026.1791484</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2026.1791484</link>
        <title><![CDATA[Beneficial microbes mitigate molecular stress responses and accelerate developmental pathways in host animals during spaceflight]]></title>
        <pubdate>2026-03-18T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Eric J. Koch</author><author>Ana Conesa</author><author>Timothy J. Garrett</author><author>Rachel Ormsby</author><author>Ryan Bohl</author><author>David W. Reed</author><author>Jamie S. Foster</author>
        <description><![CDATA[As humans continue the manned exploration of space, it is critical to understand the impact of this harsh environment on the beneficial microbes that interact with their bodies. Here, we explore whether the onset of symbiotic associations between microbes and animals are impacted during spaceflight. We used the association between the bobtail squid Euprymna scolopes and its beneficial bacterium Vibrio fischeri as an animal model system to examine how spaceflight affects symbiotic interactions at the transcriptomic, metabolomic, and lipidomic levels over time. Our results suggest that in the spaceflight environment, symbiotic microbes can mitigate molecular stress responses of the host animal and accelerate normal developmental pathways, such as neurogenesis and tissue morphogenesis. Overall, this work provides evidence that beneficial microbes can effectively colonize nascent host epithelial tissues in microgravity and play a critical role in shaping the host tissue environment to promote stability of symbiosis during spaceflight.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2025.1677728</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2025.1677728</link>
        <title><![CDATA[Cytoskeleton changes of mammalian cells in microgravity: results from three decades of low-gravity research]]></title>
        <pubdate>2025-09-25T00:00:00Z</pubdate>
        <category>Review</category>
        <author>Simon L. Wuest</author>
        <description><![CDATA[With the onset of human space flight, the profound consequences of microgravity (or weightlessness) on living organisms became apparent. Subsequently, understanding the biological processes and developing effective countermeasures has moved into the research focus. Despite their small size, isolated cells also show many adaptations in microgravity, but many fundamental processes are not understood. Because the cytoskeleton largely determines cells’ mechanical properties and is thought to play an important role in cellular mechanosensing, cytoskeleton adaptation in microgravity have been the focus of many research studies. More than 35 years ago, microtubules assembled in a cell-free system were demonstrated to be gravity dependent. Since then, multiple studies have described cytoskeleton adaptations in varieties of cells exposed to short- or long-term microgravity. In this paper on cytoskeletons in microgravity research, I aimed to grasp the published results as a bigger picture and quantify the reported effects in a systematic and more objective manner. The paper focuses on mammalian cells exposed to real microgravity (free fall) and starts with a brief review on the mechanisms how cells can or could sense their physical environment and the role of the cytoskeleton in mechanobiology.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2025.1552919</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2025.1552919</link>
        <title><![CDATA[Improved biochemical properties of roots of selected economic crops after simulated microgravity impact]]></title>
        <pubdate>2025-04-01T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Funmilola A. Oluwafemi</author><author>Omodele Ibraheem</author><author>Afolabi R. Olubiyi</author>
        <description><![CDATA[Introduction: Microgravity science involves studies of physical phenomena in which the Earth’s-gravity is significantly decreased, and these have given uniquely-new advancements towards understanding cellular metabolic processes. Under this status, plants have developed cellular readjustment mechanisms that allows adaptation to these external physical factors. Peanut (Arachis hypogaea L.), corn (Zea mays) and tomato (Solanum lycopersicum) are essential economic crops; with nutritional, medicinal and economic-values of the seeds, germinated roots and seedlings.Methods: In this study, the effects of simulated microgravity (using Clinostat) on peanut, corn and tomato germinated roots were investigated on the resistance of abiotic salinity [NaCl; 30 mM–100 mM] and heavy metal [Pb(NO3)2; 30 mM–100 mM] through antioxidants assay, and activities of root germination and elongation enzymes. The simulated microgravity equipment used in this project is a two-dimensional (2D) Clinostat. The antioxidant-potentials were done using DPPH (2,2-diphenylpicrylhydrazyl), FRAP (Fluorescence Recovery After Photobleaching) and ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6- sulfonic acid) assays. The root germination enzymes (alpha-amylase and lipase) and root elongation enzyme (beta-glucanase) activities were determined and read with ELISA (Enzyme-Linked-Immunosorbent Serologic Assay) spectrophotometer.Results: Results revealed that simulated-microgravity root samples had significantly better antioxidant-potentials than control for all the selected crops. Also, all the unstressed and stressed simulated microgravity samples had significant higher enzyme activities than the gravity (unstressed and stressed) samples.Discussion: The collection and analysis of these root samples provided a valuable resource of improved biochemical properties of the simulated microgravity samples.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2024.1376163</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2024.1376163</link>
        <title><![CDATA[Designing payload and spaceflight operations for plants from extreme terrestrial environments]]></title>
        <pubdate>2024-04-03T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Agata K. Zupanska</author><author>Emily Lockwood</author><author>Ye Zhang</author><author>Natasha J. Haveman</author><author>John A. Carver</author><author>Charles W. Spern</author><author>Emily Senyk</author><author>Jeffrey T. Richards</author><author>Lawrence L. Koss</author><author>Dinah I. Dimapilis</author><author>Stuart F. McDaniel</author>
        <description><![CDATA[Terrestrial plants from the very limits of life are likely to harbor genes that confer an advantage in human space exploration. These plants are seemingly capable of performing mission critical functions in spaceflight and on extraterrestrial farms while informing directed gene manipulation in target plant species. However, their adaptations to physiologically extreme habitats may hinder the efficacy of routine laboratory techniques for model plants. We here present the development of Antarctic moss Ceratodon purpureus payload and flight operations for the ANT1 Radiation Tolerance Experiment with Moss in Orbit on the Space Station (ARTEMOSS) experiment to the International Space Station (ISS) given limited physical space and crew time. We demonstrate that the hydrophobic surface of Antarctic moss impedes chemical tissue fixation and precludes the use of RNAlater coupled with payload hardware deployed in standard plant spaceflight experiments. We show that deep-freezing the moss tissue on Petri plates provides adequate tissue fixation and allows the extraction of high-quality RNA suitable for gene expression profiling. We replaced hardware with stacks of Petri plates housing Antarctic moss and chemical fixation with deep-freezing in a cryogenic GLACIER freezer. Our design can be translated to other plant species to expand current experimentation techniques with plants from extreme terrestrial environments in order to advance human space exploration.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2023.1282850</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2023.1282850</link>
        <title><![CDATA[Phenotypical changes in Escherichia coli K12 after prolonged exposure to simulated microgravity]]></title>
        <pubdate>2024-01-10T00:00:00Z</pubdate>
        <category>Brief Research Report</category>
        <author>Alba Chavez</author><author>Collin Topolski</author><author>Janelle Hicks</author><author>Mitchell Villafania</author><author>Natalie Baez</author><author>Marissa Burke</author><author>Hugo Castillo</author>
        <description><![CDATA[Over the past few decades there has been a steady increase in interest in the study of the role of space environment in the genetic and phenotypical changes of microorganisms. More specifically, there are concerns with astronaut health being compromised during missions to the Moon and beyond from changes in many conditions. These include changes in the physiology of bacteria leading to alterations directly related to human health such as virulence and antibiotic resistance or to the functioning of life support systems such as the increase in biofilm formation in the water supply or treatment components. The effects of space conditions on microorganisms have been studied for more than a decade; however, there is still a need to determine the impact of the physiological effect of microgravity not only of bacterial growth, but also on the different virulence-related phenotypes that might contribute to phenotypic plasticity and microbial adaptation. This study focuses on deciphering the phenotypical changes of the commensal bacterium E. coli K12 after growth under simulated microgravity conditions using a 2D microgravity analog. Using a 2D clinostat, Escherichia coli was grown up to 22 days and used to measure changes in phenotypes commonly related to virulence. The phenotypes measured included cell population growth, biofilm development and the response to acidic pH and oxidative stress. Results from our studies showed the tendency to enhanced biofilm formation and a decreased resistance to oxidative stress and to grow under acidic conditions. These results suggest that microgravity regulates the adaptation and phenotypic plasticity of E. coli that could lead to changes in virulence.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2023.1263496</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2023.1263496</link>
        <title><![CDATA[An investigation of phase change induced Marangoni-dominated flow patterns using the Constrained Vapor Bubble data from ISS experiments]]></title>
        <pubdate>2023-11-14T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Unmeelan Chakrabarti</author><author>Ayaaz Yasin</author><author>Kishan Bellur</author><author>Jeffrey S. Allen</author>
        <description><![CDATA[Kinetic models of liquid-vapor phase change often implicitly assume that the interface is in equilibrium. This equilibrium assumption can be justified for large flat interfaces far from the source of thermal energy, but it breaks down when the liquid surface is near a solid wall, or there is significant interface curvature. The Constrained Vapor Bubble (CVB) experiments conducted on the International Space Station (ISS) provide a unique opportunity to probe this common assumption and also provide unique data and insight into phase change-driven flow physics. The CVB experiment consists of a quartz cuvette partially filled with pentane such that a vapor bubble is formed at the center. The setup is heated and cooled at opposite ends, resulting in simultaneous evaporation and condensation. CVB data from the NASA Physical Science Informatics (PSI) database was used to reconstruct the entire 3D interface shape using interferometric image analysis and obtain an estimate of the net heat input to the bubble. The reconstructed interface shape is used to develop a liquid-only CFD model embedded with a custom-built “active surface” method that sets a variable interfacial temperature/phase change flux boundary condition. Phase change flux varies in both the axial and transverse directions, leading to a small (∼1 K) but discernible temperature variation along the liquid-vapor interface. The positive phase change flux near the heater end (denoting evaporation) gradually reduces and becomes negative near the cooler end (denoting condensation), resulting in an axial bulk flow of liquid from the cold to the hot end. There is also a higher flux in the thin film as opposed to the thick film, resulting in a transverse bulk flow. However, the interfacial temperature gradients along both axial and transverse directions induce a separate thermocapillary flow in a direction opposite to the bulk flows, leading to complex “wavy” flows with recirculation. A qualitative analysis of the flow pattern is presented in this paper and correlated with optical signatures from experimental images.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2023.1162268</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2023.1162268</link>
        <title><![CDATA[Comparing the effects of microgravity and amyotrophic lateral sclerosis on mouse dorsal root ganglia]]></title>
        <pubdate>2023-07-03T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Masaaki Yoshikawa</author><author>Mutsumi Matsukawa</author><author>Hideki Oshima</author><author>Chihiro Ishikawa</author><author>Haiyan Li</author><author>Takashi Kudo</author><author>Dai Shiba</author><author>Masaki Shirakawa</author><author>Masafumi Muratani</author><author>Satoru Takahashi</author><author>Mamoru Uemura</author><author>Shin Aizawa</author><author>Takashi Shiga</author>
        <description><![CDATA[Introduction: Microgravity (MG) exposure causes motor deficits and decreased neuronal activity, effects that resemble the ones observed in motor neuron diseases such as amyotrophic lateral sclerosis (ALS). Several recent studies have shown that exposure to MG and ALS also impacts the sensory systems. Yet, the role of sensory impairment in this degenerative process of exposure to MG and ALS remains unknown. In this study, we aimed at elucidating how the sensory system is affected by exposure to MG and ALS.Methods: To this end, we compared gene expression in the mouse lumbar dorsal root ganglia (DRG) of MG-exposed animals with that of control animals that remained under artificial gravity conditions. We then investigated the effects of the human superoxide dismutase 1 (SOD1) G93A mutation in a mouse model of ALS (SOD1G93A mice) on gene expression in the DRG.Results: The overlap of genes with negatively correlated expression was greater than those with positively correlated expression between the DRG of MG-exposed and SOD1G93A mice. Additionally, genes related to Imoonglia (characteristics of both immune and glial cells) and macrophage increased in response to MG exposure, while satellite glial cell genes were expressed in response to SOD1 mutation. Next, we examined genes related to sensory neuron subtypes in the DRG. We found altered gene expression in genes related to proprioceptive and mechanoreceptive neurons in the DRG of MG-exposed and SOD1G93A mice. Remarkably, the expression of Atf3 and genes related to nociceptive neurons in the DRG of SOD1G93A mice at postnatal day (P) 120 was considerably altered, whereas MG-exposed and SOD1G93A mice at P30 presented little changes.Discussion: These results indicate that exposure to MG and ALS affect gene expression in genes related to neurons and non-neuronal cells in the DRG, with significant differences between the effects of MG and the SOD1 mutation. Elucidation of the impact of exposure to MG and ALS pathogenesis in the DRG, including identification of the molecular pathways that regulate DRG dysfunction, will help better understand the differences in vulnerability and the triggering processes of impaired motor function associated with MG and ALS.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2023.1186127</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2023.1186127</link>
        <title><![CDATA[Erratum: High mass resolution fs-LIMS imaging and manifold learning reveal insight into chemical diversity of the 1.88 Ga Gunflint chert]]></title>
        <pubdate>2023-03-27T00:00:00Z</pubdate>
        <category>Erratum</category>
        <author> Frontiers Production Office</author>
        <description></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.1092802</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.1092802</link>
        <title><![CDATA[Editorial: Transport phenomena in microgravity]]></title>
        <pubdate>2022-12-16T00:00:00Z</pubdate>
        <category>Editorial</category>
        <author>D. Beysens</author>
        <description></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.981668</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.981668</link>
        <title><![CDATA[Cold for gravity, heat for microgravity: A critical analysis of the “Baby Astronaut” concept]]></title>
        <pubdate>2022-11-22T00:00:00Z</pubdate>
        <category>Hypothesis and Theory</category>
        <author>Alexander Meigal</author><author>Liudmila Gerasimova-Meigal</author>
        <description><![CDATA[The existing literature suggests that temperature and gravity may have much in common as regulators of physiological functions. Cold, according to the existing literature, shares with gravity common effects on the neuromuscular system, while heat produces effects similar to those of microgravity. In addition, there are studies evidencing unidirectional modification of the motor system to heat and hypoxia. Such agonistic relationship in a triad of “microgravity, heat, and hypoxia” and in a pair of “cold and gravity” in their effect on the neuromuscular system may have evolutionary origins. To address this problem, ten years ago, we came up with a concept with the working name Baby Astronaut hypothesis, which posed that “Synergetic adaptation of the motor system to different environments comes from their ontogenetic synchronicity.” More specifically, the synchronicity of microgravity (actually, the “wet immersion” model of microgravity), higher temperature, and hypoxia are the characteristics of the intrauterine environment of the fetus. After childbirth, this group of factors is rapidly replaced by the “extrauterine,” routine environment characterized by Earth gravity (1 G), normoxia, and lower ambient temperature. The physiological effect of cold and gravity on the motor system may well be additive (synergistic). We earlier estimated a “gravity-substitution” potential of cold-induced activity and adaptation to cold as 15–20% of G, which needs further validation and correction. In this study, we sought to critically analyze the interaction of temperature and gravity, based on the concept of Baby Astronaut, using data from the new academic literature. We have come to the conclusion that the concept of Baby Astronaut can be regarded as valid only for species such as a rat (immature, altricial species), but not for a human fetus. Several confirmatory experiments were suggested to verify (or falsify) the concept, which would allow us to consider it as empirical. In addition, the interaction of temperature and gravity may be of practical interest in the fields of neurorehabilitation and habilitation in childhood for constructing a physical environment, which would help strengthen or weaken muscle tone in specific muscles.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.971229</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.971229</link>
        <title><![CDATA[Matrix-assisted laser desorption/ionization analysis of the brain proteome of microgravity-exposed mice from the International Space Station]]></title>
        <pubdate>2022-11-16T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Correy Vigil</author><author>April Daubenspeck</author><author>Heidi Coia</author><author>Jerremy Smith</author><author>Camilla Mauzy</author>
        <description><![CDATA[Manned spaceflight exposes humans to extreme environmental conditions, including microgravity exposures. The effects of microgravity during spaceflight could lead to changes in brain structure, gene expression, and vascular physiology. Given the known physiological effects, it is highly likely that there are microgravity-initiated proteomic differentials in the brain, possibly domain specific. MALDI-TOF (matrix-assisted laser desorption/ionization time of flight) Imaging Mass Spectrometry allows the visualization of the spatial distribution of highly abundant intact proteins in tissue specimens. This study utilized this technique to visualize global proteomic changes induced by microgravity exposure in brain tissue received from the Rodent Research-1 Center for the Advancement of Science in Space (CASIS)/National Aeronautics and Space Administration (NASA). Proteome profiles were obtained from isolated whole brain tissue from microgravity exposed, Habitat control, and baseline. While a total of 135 mass peaks equating to individual proteins were identified, statistical analysis determined that there were no significant differences in the spectra profiles from the three test groups utilizing this methodology, possibly due to sample collection logistics rather than lack of cellular response.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.1032610</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.1032610</link>
        <title><![CDATA[Development of an inexpensive 3D clinostat and comparison with other microgravity simulators using Mycobacterium marinum]]></title>
        <pubdate>2022-10-28T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Joseph L. Clary</author><author>Creighton S. France</author><author>Kara Lind</author><author>Runhua Shi</author><author>J.Steven Alexander</author><author>Jeffrey T. Richards</author><author>Rona S. Scott</author><author>Jian Wang</author><author>Xiao-Hong Lu</author><author>Lynn Harrison</author>
        <description><![CDATA[2D and 3D Clinostats are used to simulate microgravity on Earth. These machines continuously alter the sample’s orientation, so the acceleration vector changes faster than the biological endpoint being monitored. Two commercially available microgravity simulators are the Rotary Cell Culture System (Synthecon Inc.), which is a 2D clinostat, and the RPM 2.0 (Yuri), which is a 3D clinostat that can operate as a random positioning machine or in constant frame velocity mode. We have developed an inexpensive 3D clinostat that can be 3D printed and assembled easily. To determine the optimal combination of inner (I) and outer (O) frame velocities to simulate microgravity, two factors were considered: the time-averaged magnitude and the distribution of the acceleration vector. A computer model was developed to predict the acceleration vector for combinations of frame velocities between 0.125 revolutions per minute (rpm) and 4 rpm, and a combination of I = 1.5 rpm and O = 3.875 rpm was predicted to produce the best microgravity simulation. Two other frame velocity combinations were also used in further tests: I = 0.75 rpm and O = 3.625 rpm, and I = 2 rpm and O = 1.125 rpm. By operating the RPM 2.0 in constant velocity mode at these three velocity combinations, the RPM 2.0 algorithm data confirmed that these operating conditions simulated microgravity. Mycobacterium marinum was selected for biological comparison experiments as this bacterium can grow as a biofilm or a planktonic culture. Biofilm experiments revealed that the RPM 2.0 and the 3D clinostat with I = 1.5 rpm and O = 3.825 rpm produced similar structures in attached biofilm, and similar changes in transcriptome for the bacteria in suspension compared to the normal gravity transcriptome. Operating the 3D clinostat at I = 2 rpm and O = 1.125 rpm, and the Synthecon 2D clinostat in simulated microgravity orientation at 25 rpm resulted in the same decreased planktonic growth and increased rifampicin survival compared to normal gravity. This study validates the inexpensive 3D clinostat and demonstrates the importance of testing the operating conditions of lab-developed clinostats with biological experiments.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.989416</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.989416</link>
        <title><![CDATA[Editorial: Technologies for handling, preparation, and liquid-based analysis of fluidic samples in space]]></title>
        <pubdate>2022-09-23T00:00:00Z</pubdate>
        <category>Editorial</category>
        <author>Florian Kehl</author><author>Kathryn Bywaters</author><author>Alberto G. Fairén</author><author>Timothy Granata</author><author>Antonio J. Ricco</author><author>Luis Zea</author>
        <description></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.899242</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.899242</link>
        <title><![CDATA[Direct Robotic Extrusion of Photopolymers (DREPP): Influence of microgravity on an in-space manufacturing method]]></title>
        <pubdate>2022-08-23T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Michael Kringer</author><author>Christoph Böhrer</author><author>Moritz Frey</author><author>Jannik Pimpi</author><author>Markus Pietras</author>
        <description><![CDATA[A method using Direct Robotic Extrusion of Photopolymers (DREPP) to manufacture structures in space in a cost- and power-efficient way is presented in this article. The DREPP technology has the potential to outperform conventional deployable structures, which generally suffer from severe limitations: long and high-cost development phases, dimensioning driven by launch loads instead of operational loads, mechanical complexity as well as constraints to the maximum structure size due to volume limitations on the spacecraft. In-Space Manufacturing (ISM) and especially AM offer a solution to circumvent these limitations. Fundamental investigations on AM in space have already been carried out on the International Space Station (ISS). Numerous test prints have shown that Fused Filament Fabrication (FFF) provide satisfactory results under microgravity and controlled environmental conditions. With the investigated manufacturing process, a photoreactive resin is robotically extruded through a nozzle and directly cured by UV-light. Unlike most conventional Additive Manufacturing (AM) methods, which manufacture layer-by-layer, the DREPP technology is able to create three-dimensional structural elements in one continuous movement. To investigate the feasibility under microgravity conditions, multiple experiments were performed on parabolic flights, where it was shown that different geometries can be successfully manufactured under microgravity conditions. When examining the printing process at zero-gravity and under 1 g conditions, differences in the printing behaviour can be observed, which are investigated in detail. In addition, the evaluation shows that a large curing zone – the transition area between the liquid and cured state of the extruded resin – is easier to handle in zero-gravity than under 1 g conditions. This contributes to an increased overall process stability and enables new ways for controlling the process. This article provides details on the ground, zero and altered gravity testing, process quality evaluation and gives an outlook on future investigations of the DREPP approach and preparations for experiments in microgravity and vacuum on a sounding rocket.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.900549</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.900549</link>
        <title><![CDATA[Algorithms for Large Scale Additive Manufacturing in a Free-Flying Environment]]></title>
        <pubdate>2022-07-22T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Oliver Tauscher</author><author>Declan Jonckers</author><author>Aditya R. Thakur</author>
        <description><![CDATA[Large scale additive manufacturing (LSAM) refers to the fabrication of structures that exceed the build volume of conventional additive manufacturing setups. This can be used for in-space manufacturing (ISM), facilitating the production of large functional structures in space which cannot fit within the payload fairing of a launcher system. In this paper, a new approach for a continuous fabrication process of structural elements is presented, combining the reach of a free-flying satellite and a robotic arm, utilizing a fused filament fabrication (FFF) 3D-printing setup. A motion planning algorithm was developed which calculates energy-efficient movement trajectories based on a truss design input combined with the movement constraints of the satellite and robotic arm. Using this printing paradigm, a long support-free truss was manufactured. This approach was further elevated by extending the truss structure along the second planar axis, thus facilitating the manufacture of structures larger than generally possible through a layer-by-layer approach. Subsequently, combining the segmented and continuous printing approach, a planar truss structure was produced.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.880012</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.880012</link>
        <title><![CDATA[CFD-Based Feasibility Study of Laser-Directed Energy Deposition With a Metal Wire for On-Orbit Manufacturing]]></title>
        <pubdate>2022-07-08T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Seyyed Mohammad Ali Noori Rahim Abadi</author><author>P. Hagqvist</author><author>F. Sikström</author><author>I. Choquet</author>
        <description><![CDATA[Additive manufacturing of parts on-site in space requires investigating the feasibility of adapting to zero-gravity and near-vacuum conditions, a technology applied today on Earth at standard conditions. While a few studies have been conducted for powder bed fusion, a feasibility study remains to be explored for direct energy deposition using a laser beam and a metal wire. This is the purpose of this study, which is conducted using a modeling approach based on computational fluid dynamics. The simulation model developed includes melting, re-solidification, vaporization, prediction of beam energy absorption as a function of the local surface temperature and curvature, ray tracing, tracking of free surface deformation and metal transfer, and wire-resistive heating. The study is carried out by starting from process parameters suited for stable on-Earth metal deposition. These conditions were also studied experimentally to validate the simulation model, leading to satisfactorily results. A total of three other test cases with ambient pressure lowered down to near-vacuum and/or gravitation down to zero are investigated. It is found that, compared to on-Earth conditions, in-space conditions can induce vaporization of the metal alloy that is large enough to result in a curvature of the melt pool free surface but too small to lead to the formation of a keyhole. The in-space conditions can also modify the force balance at the liquid melt bridge between the wire and the melt pool, leading to small changes in the curvature and temperature field at the free surface of the wire tip. Among the observed consequences are a small increase of the melt pool length and a small elevation of the bead height. More importantly, for process control, changing to in-space conditions might also affect the stability of the process, which could be assessed through the width of the liquid metal bridge. However, by using appropriate process control to maintain a continuous liquid metal bridge, it is concluded that direct energy deposition of metal using a laser and a wire could be used for manufacturing metal parts in-space in a tempered atmosphere.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.883899</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.883899</link>
        <title><![CDATA[Transport Properties of Critical Sulfur Hexafluoride From Multiscale Analysis of Density Fluctuations]]></title>
        <pubdate>2022-06-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Ana Oprisan</author><author>Dereck Morgado</author><author>David Dorf</author><author>Seth Zoppelt</author><author>Sorinel A. Oprisan</author><author>Inseob Hahn</author><author>Yves Garrabos</author><author>Carole Lecoutre-Chabot</author><author>Daniel Beysens</author>
        <description><![CDATA[Density fluctuations near critical points have a wide range of sizes limited only by the boundaries of the enclosing container. How would a fluctuating image near the critical point look if we could break it into disjoint spatial scales, like decomposing white light into narrow-band, monochromatic waves? What are the scaling laws governing each spatial scale? How are the relaxation times of fluctuations at each spatial scale related to the dynamics of fluctuations in the original image? Fluctuations near the critical point of pure fluids lead to different patterns of phase separation, which has a significant influence on the materials’ properties. Due to the diverging compressibility of pure fluids near the critical temperature, the critical phase collapses under its weight on Earth. It limits both the spatial extent of fluctuations and their duration. In microgravity, the buoyancy and convection are suppressed, and the critical state can be observed much closer to the critical point for a more extended period. Local density fluctuations induce light intensity fluctuations (the so-called “critical opalescence”), which we recorded for a sulfur hexafluoride (SF6) sample near the critical point in microgravity using the ALI (Alice Like Instrumentation insert) of the DECLIC (Dispositif pour l’Etude de la Croissance et des Liquides Critiques) facility on the International Space Station (ISS). From the very short (approximately 173 s total recording) data set very near, within 200 μK, the critical temperature, we determined the effective diffusion coefficient for fluctuations of different sizes. For transient and non-stationary data recorded very near the critical point immediately after a thermal quench that steps through critical temperature, we separated fluctuations of various sizes from the original images using the Bidimensional Empirical Mode Decomposition (BEMD) technique. Orthogonal and stationary Intrinsic Mode Function (IMF) images were analyzed using the Fourier-based Dynamic Differential Microscopy (DDM) method to extract the correlation time of fluctuations. We found that a single power-law exponent represented each IMF’s structure factor. Additionally, each Intermediate Scattering Function (ISF) was determined by fluctuations’ unique relaxation time constant. We found that the correlation time of fluctuations increases with IMF’s order, which shows that small size fluctuations have the shortest correlation time. Estimating thermophysical properties from short data sets affected by transient phenomena is possible within the BEMD framework]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.876585</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.876585</link>
        <title><![CDATA[Mechanical Design of Self-Reconfiguring 4D-Printed OrigamiSats: A New Concept for Solar Sailing]]></title>
        <pubdate>2022-05-31T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Aloisia Russo</author><author>Bonar Robb</author><author>Stefania Soldini</author><author>Paolo Paoletti</author><author>Gilles Bailet</author><author>Colin R. McInnes</author><author>Juan Reveles</author><author>Ahmed K. Sugihara</author><author>Stephane Bonardi</author><author>Osamu Mori</author>
        <description><![CDATA[In this article, a self-reconfiguring OrigamiSat concept is presented. The reconfiguration of the proposed OrigamiSat is triggered by combining the effect of 4D material (i.e. origami’s edges) and changes in the local surface optical properties (i.e., origami’s facets) to harness the solar radiation pressure acceleration. The proposed OrigamiSat uses the principle of solar sailing to enhance the effect of the Sun radiation to generate momentum on the Aluminised Kapton (Al-Kapton) origami surface by transitioning from mirror-like to diffusely reflecting optical properties of each individual facet. Numerical simulations have demonstrated that local changes in the optical properties can trigger reconfiguration. A minimum of 1-m edge size facet is required for a thick-origami to generate enough forces from the Sun radiation. The thick-origami pattern is 3D-printed directly on a thin Al-Kapton film (the solar sail substrate which is highly reflective). An elastic filament (thermoplastic polyurethane TPU) showed best performance when printing directly on the Al-Kapton and the Acrylonitrile Butadiene Styrene with carbon fiber reinforcement (ABS/cc) is added to augment the origami mechanical properties. The 4D material (shape memory polymer) is integrated only at specific edges to achieve self-deployment by applying heat. Two different folding mechanisms were studied: 1) the cartilage-like, where the hinge is made combining the TPU and the 4D material which make the mounts or valleys fully stretchable, and 2) the mechanical hinge, where simple hinges are made solely of ABS/cc. Numerical simulations have demonstrated that the cartilage-like hinge is the most suitable design for light-weight reconfigurable OrigamiSat when using the solar radiation pressure acceleration. We have used build-in electric board to heat up the 4D material and trigger the folding. We envisage embedding the heat wire within the 4D hinge in the future.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.876642</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.876642</link>
        <title><![CDATA[A Review on Transport Phenomena Near the Critical Point of Fluids Under Weightlessness]]></title>
        <pubdate>2022-05-25T00:00:00Z</pubdate>
        <category>Review</category>
        <author>D. Beysens</author>
        <description><![CDATA[Fluids near their liquid-vapor critical point, liquid mixtures near their miscibility critical point, exhibit universal behavior in their transport properties. Weightlessness is most often mandatory to properly evidence these properties. This review is concerned with some of the most important results obtained thanks to space experiments concerning thermal, mass, and momentum transport. Thermal aspects in pure fluids are mainly concerned with the discovery of a new thermalization process, the Piston Effect, leading to paradoxical effects such as a “critical speeding up” instead of the classical “critical slowing down”, heat seemingly flowing backwards and cooling resulting from heating. Mass transport deals with the process of boiling in the liquid phase, and phase transition when the fluid or the liquid mixture is thermally quenched from the homogeneous, supercritical region, to the two-phase region where it phase separates. Weightlessness makes universal the dynamics of phase separation. Momentum transport is concerned with the scaled behavior of viscosity and the effects of vibrations. Vibrations lead to effects (interface position, instabilities) that resemble buoyancy effects seemingly caused by an artificial gravity. Although weightlessness has led to solve important problems, many questions are still opened.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frspt.2022.835464</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frspt.2022.835464</link>
        <title><![CDATA[Instabilities in a Spherical Liquid Drop]]></title>
        <pubdate>2022-05-24T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Roger Prud'homme</author>
        <description><![CDATA[We examine cases of stationary vortices that can appear inside spherical liquid drops in microgravity conditions. The first case is that of an incompressible external flow of uniform speed at infinity, leading the liquid in the drop by friction to form a Hill vortex. In the second case, the external fluid does not interact by friction with the liquid, but the drop is subjected to an axial temperature gradient causing a variation in surface tension. This time it is the induced movement which entrains the internal liquid. Note that the two situations can lead to the same Hill vortex. Combined effects are envisioned. We are also interested in the time factor in these phenomena.]]></description>
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