Gravity Conditions Research Articles

Systematic screening of 42 vancomycin-resistant Enterococcus faecium strains for resistance, biofilm, and desiccation in simulated microgravity

Vancomycin-resistant Enterococcus faecium (VRE) presents significant challenges in healthcare, particularly for hospitalized and immunocompromised patients, including astronauts with dysregulated immune function. We investigated 42 clinical E. faecium isolates in simulated microgravity (sim. µg) using a 2-D Clinostat, with standard gravity conditions (1 g) as a control. Isolates were tested against 22 antibiotics and characterized for biofilm formation and desiccation tolerance. Results showed varied responses in minimum inhibitory concentration (MIC) values for seven antibiotics after sim. µg exposure. Additionally, 55% of isolates showed a trend of increased biofilm production, and 59% improved desiccation tolerance. This investigation provides initial insights into E. faecium’s changes in response to simulated spaceflight, revealing shifts in antibiotic resistance, biofilm formation, and desiccation tolerance. The observed adaptability emphasizes the need to further understand VRE’s resilience to microgravity, which is crucial for preventing infections and ensuring crew health on future long-duration space missions.

Modulation of Root Hydrotropism and Recovery From Drought by MIZ1-like Genes in Tomato.

Drought limits crop performance worldwide. Plant roots' ability to grow toward moisture, termed hydrotropism, is considered one strategy for optimizing water recruitment from the growth medium. Based on the sequence of the hydrotropism-indispensable MIZ1 protein in Arabidopsis thaliana, we identify hydrotropism and drought-responsive genes in tomato. We utilized CRISPR/Cas9 genome-editing technology for targeted mutagenesis of three hydrotropism-associated loci (MIZ1-like) in tomato (Solanum lycopersicum). We show that the three tomato MIZ1-like genes are drought-responsive and two of them are hydrostimulation-responsive. Examination of the root hydrotropic response of triple and double mutants indicated the gene SlMIZ1-1 as indispensable for tomato root hydrotropism. Moreover, expression of the SlMIZ1-1 gene in the Arabidopsis miz1 mutant effectively complemented the lost MIZ1 functionality, including root hydrotropic bending and generation of hydrotropic Ca2+ signals. Transcriptome analysis of hydrostimulated tomato root tips under control gravity and continuous clinorotation conditions was performed to identify gravitropism- and hydrotropism-responsive genes. This analysis suggested the involvement of ethylene and ABA signalling in modulating the interplay between hydrotropism and gravitropism. Unveiling the molecular mechanisms that underlie hydrotropism and drought response holds great potential for improving crop performance under limiting water availability due to global climate changes.

A duty to enhance? Genetic engineering for the human Mars settlement.

Humans living off-world will face numerous physical, psychological and social challenges and are likely to suffer negative health effects due to their lack of evolutionary adaptation to space environments. While some of the necessary adaptations may develop naturally over many generations, genetic technologies could be used to speed this process along, potentially improving the wellbeing of early space settlers and their offspring. With broad support, such a program could lead to significant genetic modification of off-world communities, for example, to limit radiation damage on body systems or prevent bone and muscle loss in reduced gravity conditions. Given the extreme stressors of living off-world, and the need to have a healthy workforce to support a fledgling human settlement, those in favour of using genetic technologies to enhance settlers might even claim there is a moral imperative to protect their health in the face of the unique threats of space travel, especially for children born in settlements who did not take on these risks voluntarily. For some, this might simply be an extension of procreative beneficence. However, ethical concerns arise regarding the risks of embracing a eugenicist agenda and the potential impacts on the rights of future settlers to refuse such genetic enhancements for themselves or their children.

Hydroponic: A Study of Space Farming

This paper demonstrates the possibility of supporting human life in space, by growing fresh vegetables and producing them through simulated growing conditions. Supplying fresh vegetables to space stations and manned space missions is complicated and prohibitively expensive. Growing plants can be tough in space because of zero gravity, unavailability of soil, fertilizers, etc. Hydroponic is an advanced technology for growing plants without using natural resources (i.e. soil, air, natural fertilizers, etc.). It is a combination with greenhouses, it is advanced technology and highly intensive. The hydroponic technology takes place inside the enclosures to control air, temperature, and humidity using a vapor pressure deficit (vpd) controller, nutrient flow, and water flow controller. A major concern is the micro-gravity, which causes roots to grow differently than those from earth farming. In microgravity and hypo-gravity conditions, space farming utilizes a variety of methods like hydroponics, aeroponics, etc. This paper focuses on the hydroponics design, structure, operations, technique, substrate suitable for the plants, pH values, water level, and controllers required for hydroponic technology. The main objective of the paper is to build a preliminary design that is completely automatic that is robust and foolproof and find the definitive solution to the problems in the substrate and multi-spectrum lighting aroused due to gravity and vacuum conditions. The fully automated systems help to the reduction of labor and provide good healthy food to astronauts.

Effect of Microgravity on Rare Earth Elements Recovery by Burkholderia cepacia and Aspergillus niger

Rare earth elements (REEs) are indispensable in modern industry and technology, driving an urgent demand for innovative, eco-friendly recovery technologies. As space exploration advances, the impact of microgravity on microorganisms has become a focal point, yet the effects on microbial growth and REEss recovery remain uncharted. This study investigates the biosorption of REEs by Burkholderia cepacia (B. cepacia) and Aspergillus niger (A. niger) from a mixed solution containing La, Ce, Pr, Nd, Sm, Er, and Y under varying initial concentrations, pH levels, and microgravity conditions. We observed that the medium’s pH rose with B. cepacia and fell with A. niger when cultured in normal gravity conditions, suggesting distinct metabolic responses. Notably, microgravity significantly altered microbial morphology and metabolite profiles, significantly enhancing REEs recovery efficiency. Specifically, the recovery of B. cepacia of Ce and Pr peaked at 100%, and A. niger achieved full recovery of all tested REEs at pH 1.5 (suboptimal growth conditions). This study pioneers the application of biosorption for the recovery of REEs in microgravity conditions, presenting a promising strategy for future resource exploitation by space biomining.

Study on the Continuous Whole Process Preparation of Peptizable Pseudoboehmite by High Gravity Strengthening Reaction of CO2 and Heat Transfer.

The preparation of highly peptizable pseudoboehmite faces challenges such as slow reaction rate, prolonged aging times leading to poor peptization performance, and difficulty in achieving continuous production. In this study, a novel approach was proposed involving a high gravity reactor to enhance carbonation reaction control for pseudoboehmite nucleation, a high gravity steam heating process, and a continuous aging process in pipelines. By coupling these three processes, the continuous whole process production of highly peptizable pseudoboehmite under high gravity conditions was achieved. First, the effect of high gravity reactor enhancement on the reaction and the resulting solid phase was investigated. Second, the impact of aging temperature and time on the solid phase formed at different reaction end points was studied using high gravity and steam heating of the liquid phase. Furthermore, the influence of synthesis conditions on the peptization performance of pseudoboehmite was extensively examined. Finally, the nucleation and growth mechanisms of pseudoboehmite under high gravity conditions were analyzed. It was found that increasing high gravity factor, CO2 gas flow rate, and CO2 content accelerated carbonation reaction rate, promoting pseudoboehmite crystal nucleation. Increasing aging temperature and time facilitated the growth of pseudoboehmite nuclei and improved peptization performance. The high gravity device altered the gas-liquid phase contact state of traditional kettle-type equipment, reducing the reaction time and heating time from minutes to seconds, thus achieving the continuous whole process production of pseudoboehmite with a peptization index of 100% from sodium aluminate solution by kiln flue gas.

Effect of Microgravity on the Metal Droplet Transfer and Bead Characteristics in the Directed Energy Deposition-Arc Process

Abstract Directed energy deposition-arc (DED-arc) is a viable method of metal 3D printing for manufacturing in-space under microgravity conditions. This study investigates the effect of reduced gravity on the droplet transfer in a gas metal arc welding (GMAW)-based DED-arc process. Single bead deposited using GMAW welding process under microgravity and standard terrestrial gravity (1 g) are compared. Microgravity was simulated in a drop tower where the experimental capsule was subjected to 2.5 s of free-fall. The experimental setup for GMAW welding process, including high-speed cameras and sensors, was present within the experimental capsule. Droplet frequency and diameter were measured and compared between microgravity and 1 g using the images obtained. Further, the impact of reduced gravity on weld bead geometry and the distribution of gas porosity was investigated. Microhardness analysis was also conducted on both 1 g and reduced gravity samples to assess variations in material hardness. A statistically significant difference in droplet diameter and frequency was found. This difference is attributed to the reduction in gravitational force. Upon analyzing the weld bead geometry, noticeable variations are detected in the contact angles and the reinforcement of beads formed under different gravity conditions. These differences are attributed to alterations in convection within the molten weld pool. The blowhole analysis revealed a noticeable trend, wherein reduced gravity facilitated the coalescence of gas porosity, resulting in larger diameters due to alterations in weld pool convection. There were no statistically significant changes observed in both microhardness and surface finish.

The MyoGravity project to study real microgravity effects on human muscle precursor cells and tissue

Microgravity (µG) experienced during space flights promotes adaptation in several astronauts’ organs and tissues, with skeletal muscles being the most affected. In response to reduced gravitational loading, muscles (especially, lower limb and antigravity muscles) undergo progressive mass loss and alteration in metabolism, myofiber size, and composition. Skeletal muscle precursor cells (MPCs), also known as satellite cells, are responsible for the growth and maintenance of muscle mass in adult life as well as for muscle regeneration following damage and may have a major role in µG-induced muscle wasting. Despite the great relevance for astronaut health, very few data are available about the effects of real µG on human muscles. Based on the MyoGravity project, this study aimed to analyze: (i) the cellular and transcriptional alterations induced by real µG in human MPCs (huMPCs) and (ii) the response of human skeletal muscle to normal gravitational loading after prolonged exposure to µG. We evaluated the transcriptomic changes induced by µG on board the International Space Station (ISS) in differentiating huMPCs isolated from Vastus lateralis muscle biopsies of a pre-flight astronaut and an age- and sex-matched volunteer, in comparison with the same cells cultured on the ground in standard gravity (1×g) conditions. We found that huMPCs differentiated under real µG conditions showed: (i) upregulation of genes related to cell adhesion, plasma membrane components, and ion transport; (ii) strong downregulation of genes related to the muscle contraction machinery and sarcomere organization; and (iii) downregulation of muscle-specific microRNAs (myomiRs). Moreover, we had the unique opportunity to analyze huMPCs and skeletal muscle tissue of the same astronaut before and 30 h after a long-duration space flight on board the ISS. Prolonged exposure to real µG strongly affected the biology and functionality of the astronaut’s satellite cells, which showed a dramatic reduction of responsiveness to activating stimuli and proliferation rate, morphological changes, and almost inability to fuse into myotubes. RNA-Seq analysis of post- vs. pre-flight muscle tissue showed that genes involved in muscle structure and remodeling are promptly activated after landing following a long-duration space mission. Conversely, genes involved in the myelination process or synapse and neuromuscular junction organization appeared downregulated. Although we have investigated only one astronaut, these results point to a prompt readaptation of the skeletal muscle mechanical components to the normal gravitational loading, but the inability to rapidly recover the physiological muscle myelination/innervation pattern after landing from a long-duration space flight. Together with the persistent functional deficit observed in the astronaut’s satellite cells after prolonged exposure to real µG, these results lead us to hypothesize that a condition of inefficient regeneration is likely to occur in the muscles of post-flight astronauts following damage.

DNS of laboratory-scale turbulent premixed counterflow flames under elevated gravity conditions

In the present work, direct numerical simulations (DNSs) of laboratory-scale turbulent premixed counterflow flames are performed to understand the effect of elevated gravity on flame structures. In the DNS, a turbulent jet of CH4/N2/O2 mixture is injected in opposition to a stream of combustion product. Three cases were considered, i.e., one case with normal gravity and two cases with elevated gravity in different directions. The DNS results of the case under normal gravity conditions were found to be in good agreement with the experimental data. The turbulent flame speed is the highest in the case with elevated gravity aligned with the mean flame propagating direction, which is due to the increase in flame surface area and stretch factor. The gravity levels have a substantial influence on the flame extinction characteristics. It was observed that the flame front is pushed toward the direction of the gravity. When the elevated gravity antialigns with the mean flame propagating direction, the flame front travels across the stagnation plane toward the combustion product stream, leading to significant reactant dilution and flame extinction. The flame normal vector preferentially aligns with the most compressive strain rate for various gravity conditions. The tangential strain rate is the greatest (smallest) when elevated gravity antialigns (aligns) with the mean flame propagating direction. The impact of elevated gravity on the tangential strain rate at the flame fronts ultimately leads to a displacement in the flame front location relative to the stagnation plane, thereby influencing flame extinction.

Estimation of joint moments during ball throwing in simulated altered gravity conditions using a musculoskeletal modelling approach: preliminary results

Estimation of joint moments during ball throwing in simulated altered gravity conditions using a musculoskeletal modelling approach: preliminary results

Physical Modeling of Hydrate Dissociation in Sandy Sediment by Depressurization under Hypergravity and Normal Gravity Conditions

Physical Modeling of Hydrate Dissociation in Sandy Sediment by Depressurization under Hypergravity and Normal Gravity Conditions

Numerical investigation of two-phase flow control based on the coalescence under variation of gravity conditions

Numerical investigation of two-phase flow control based on the coalescence under variation of gravity conditions

Superrotations at spacelike infinity

We propose a consistent set of boundary conditions for gravity in asymptotically flat spacetime at spacelike infinity, which yields an enhancement of the Bondi-Metzner-Sachs group with smooth superrotations and new subleading symmetries. These boundary conditions are obtained by allowing fluctuations of the boundary structure which are responsible for divergences in the symplectic form, and a renormalization procedure is required to obtain finite canonical generators. The latter are then made integrable by incorporating boundary terms into the symplectic structure, which naturally derive from a linearized spin-two boundary field on a curved background with positive cosmological constant. Finally, we show that the canonical generators form a nonlinear algebra under the Poisson bracket and verify the consistency of this structure with the Jacobi identity. Published by the American Physical Society 2024

Gravity effects on a bio-inspired self-burrowing probe in granular soils

In recent years, self-burrowing probes have been studied since they can be suitable for soil monitoring in locations with limited access such as outer space bodies and underneath existing structures. We study the performance of a self-burrowing probe under different gravity conditions, from low gravity (i.e., 1/6g, 1/3g and 1g) to high gravity (i.e., 5g, 10g and 15g), specifically in terms of penetration distance and energy consumption. Results show that the probe reaches efficient penetration in all gravity conditions and that it achieves larger penetration distances in high gravity conditions. However, the penetration efficiency, shown as unit energy per meter, is higher in low gravity. Additionally, we prove that a simple dimensional analysis provides reasonable scaling factors for first order effects in forces, velocities and energy. The findings in this study give confidence to the potential use of self-burrowing probes in campaigns of soil testing and sensor deployment in outer space or centrifuges in which the gravity conditions can differ from Earth.

Experimental investigation and modelling of hydrodynamics and heat transfer in flow boiling in normal and microgravity conditions

The development of long-term space thermal management systems has informed research into the influence of gravity on boiling. This work explored the influence of gravity on the hydrodynamics and heat transfer of boiling flow. Experiments were carried out using two test loops each consisting of a 6 mmID transparent cylindrical test section. Upward (+1░g) and downward (−1░g) flow boiling experiments were carried out in the laboratory while microgravity (μg) experiments were carried out during a parabolic flight campaign. The results of flow visualisation showed significant influence of gravity on the flow patterns and the influence of gravity was generally limited to mass flux, G≤400kg/m2s and/or vapor quality, x≤0.35. In all three gravity conditions, the measured heat transfer coefficient was influenced by heat flux, mass flux and/or vapor quality. For liquid Reynolds number, Relo≤2000(G≤150kg/m2s) and boiling number Bo<0.002 the measured heat transfer coefficient was highest in −1g flow and lowest in μg flow but becomes comparable at Bo>0.002. A correlation for predicting microgravity heat transfer coefficient was proposed in this work and the proposed correlation predicted 100 % of the μg data in the current work within ±20%, predicted nearly 100 % of the μg data of Ohta et al. (2013) within ±30% and around 85 % of the μg data of Narcy (2014) within -20 % to +50 %. A correlation for predicting the gravity dependent regime as it relates to heat transfer coefficient in +1g and μg flows was also proposed in this work. The proposed criterium correctly predicted over 85 % of the gravity-dependent heat transfer coefficient in the current work and the works of Lebon et al. (2019), Narcy (2014), Ohta et al. (2013).

Fibrous anion exchanger with ternary amino groups as a component of the substrate for plants growing

A set of studies necessary to determine the suitability of a fibrous anion exchanger with ternary amino groups based on industrial polyacrylonitrile fiber Nitron C as a component of ion substrates was carried out. A laboratory-prepared ion exchanger sample had a working exchange capacity equal to 0.9 meq/g for the nitrate anion, which limits the biological productivity of the substrate for growing plants, in the physiological pH range = 5.5–7.5 and the concentration of the equilibrium nutrient solution is 0.02 eq/l. This capacity is at the level of the best granular ion exchangers and significantly exceeds the capacity of the previously used fibrous ion exchangers for growing plants in zero gravity conditions on space stations in 1970–1994 (Mir, Soyuz TM-10 – TM-17). The synthesized ion exchanger is a polyampholyte and contains three types of ion exchange groups, has high hydrophilicity and mechanical properties that allow it to be processed into textiles and used for any purpose, in which fibrous ion exchangers can be used (air and water purification, human protection means, etc.).

A low-Mach volume-of-fluid model for the evaporation of suspended droplets in buoyancy-driven flows

This study introduces a comprehensive numerical model capable of simulating the evaporation of suspended droplets under different gravity conditions. Unlike previous studies, this work provides a detailed description of the multicomponent evaporation process by integrating: (i) interface-resolved evaporation; (ii) suspension by the action of the surface tension force, and (iii) variable physical properties. The model effectively captures complex phenomena such as thermal expansion, natural convective fluxes, and liquid internal recirculation, which cannot be directly resolved using more widespread spherically-symmetric models. Validation against experimental data confirms the model’s accuracy in predicting the droplet evaporation dynamics, and its utility in resolving discrepancies between prior numerical simulations results and experimental data. The model was implemented in the Basilisk framework; both the code and the simulations setups are freely available on the Basilisk sandbox.

Effect of electric field on bubble dynamics in channel flow boiling using lattice Boltzmann method

The application of an electric field in flow boiling has been proven to effectively enhance heat transfer and reduce pressure drop instability. This study aims to elucidate the mechanism of the impact of electric fields on flow boiling bubble dynamics through the pseudo-potential lattice Boltzmann method (LBM). The interplay between the externally imposed electric field incoming velocity in different gravity conditions examined. These factors can regulate flow boiling heat transfer in horizontal channel. The results demonstrate a competitive relationship between electric field and gravity and between incoming velocity and gravity. Therefore, under higher gravity condition, an electric field is less effective to enhance flow boiling heat transfer than in low gravity condition and vice versa. Additionally, there exists a synergistic relationship between incoming velocity and the electric field that mitigates their competition. Moreover, when considering multipoint nucleation processes, applying an electric field can attenuates bubble–bubble interactions and inhibit large bubble formation so as to accelerates bubble condensation in supercooled flows and enhance boiling heat transfer. This work provides comprehensive physical insights into the mechanism of electric field to enhance the heat transfer in flow boiling, which is instructive for the development of electrohydrodynamic technique in flow boiling enhancement.

Two-phase flow instabilities during microgravity flow boiling onboard the International Space Station

This study is an elaboration on flow instabilities observed during flow boiling experiments conducted onboard the International Space Station (ISS) as part of the Flow Boiling and Condensation Experiment (FBCE). During highly subcooled flow boiling, liquid backflow into the channel that rapidly condenses vapor within the channel was observed. Experiments were conducted with an enhanced sampling frequency of 30 Hz and an extended image sequence recording duration of at least 4 seconds at 500 frames per second to further investigate the instability. Identical experiments were performed both in microgravity onboard the International Space Station (ISS) and in Earth gravity during vertical upflow. Instabilities in microgravity are more severe than those in Earth gravity and, at their most severe, propagate to the channel's upstream region. Instabilities are observed within the channel when the intensity, I, which is dependent on inlet pressure fluctuations and mass velocity, exceeds 1.8 × 105 W/m2. Parametric trends of the frequency and amplitude of inlet pressure fluctuations during instability are examined, which reveal instabilities are most severe at low flow rates, high inlet subcoolings, and high heat fluxes. Various stability maps proposed in the literature are evaluated against the present database, and instabilities only manifest for subcooling numbers greater than 14. A subset of the database containing the Onset of Flow Instability (OFI) point is extracted to first evaluate correlations available in the literature and then develop a new correlation. The new correlation is applicable in both microgravity and Earth gravity conditions and predicts the database with a Mean Absolute Error (MAE) of 1.3%.

Probing the melting dynamics in a phase change Rayleigh–Bénard system under low gravity conditions

The present work aims to investigate dynamic characteristics of Rayleigh–Bénard convection during the solid–liquid phase change process under the influence of variable low-gravity conditions. Low-gravity conditions are crucial to gain physical insights into the complex convection dynamics relevant in terrestrial and space environments that feature diverse gravitational fields. The melting dynamics of a paraffin-based phase change material with Prandtl number Pr ≈ 71 in a square rigid walled enclosure is analyzed by subjecting it to a fixed temperature difference resulting in a Stefan number Ste ≈ 0.33. The enthalpy porosity method is employed to simulate the solid-liquid phase change process in Rayleigh number range 105<Ra <107 to take wide range of gravitational acceleration (0.0g, 0.1g, 0.2g, 0.4g, 0.6g, 0.8g, and g) into account. The simulation results allow detailed insights on the buoyancy-driven convective flow phenomena in a phase-change Rayleigh–Bénard system. Various characteristic flow regimes, the criteria for the onset of convective instabilities, and scaling analysis are presented under varied gravitational acceleration. The findings reveal that the critical Rayleigh number (Racr) for the onset of convection is found to vary between 1351.5 and 1810.5 under the gravity range investigated in contrast to the Racr ≈ 1707.7 for classical Rayleigh-Bénard system under the standard gravity. Furthermore, the scale analysis based on the numerical results shows that the relationship between effective Nusselt number (Nue) and effective Rayleigh number (Rae) follows a power law behavior Nue = 0.27Rae0.25 under each gravity condition, similar to the classical Rayleigh–Bénard system.