Hypergravity Conditions Research Articles

Experimental study on subcooled pool boiling heat transfer under hypergravity

The pool boiling heat transfer experiment was conducted with pure water under subcooled and saturation conditions, both in hypergravity (1–3 g) and normal gravity (1 g) at atmospheric pressure. A turntable was employed to simulate the hypergravity environment. Subcooling was varied at four different levels: 2 °C, 5 °C, 8 °C, and 10 °C, corresponding to gravity levels ranging from 1 g to 3 g. Heat transfer enhancement was observed in the fully developed region under saturation conditions, whereas it was less pronounced in the natural convection region. Specifically, increasing the subcooling degrees leads to an expansion of the natural convection region, where the effects of hypergravity become noticeable at higher heat flux levels. The effect of hypergravity diminishes as the bubble detachment diameter in the fully developed region decreases with increasing subcooling degree, implying that the main effect of hypergravity on heat transfer is due to its influence on the bubble behavior. Additionally, a detailed analysis is presented to further explain the effect of hypergravity on heat transfer, focusing on the bubble dynamical behavior and the impact of buoyancy under hypergravity conditions.

Under pressure—the influence of hypergravity on electrocortical activity and neurocognitive performance

The effects of hypergravity and the associated increased pressure on the human body have not yet been studied in detail, but are of great importance for the safety of astronauts on space missions and could have a long-term impact on rehabilitation strategies for neurological patients. Considering the plans of international space agencies with the exploration of Mars and Moon, it is important to explore the effects of both extremes, weightlessness and hypergravity. During parabolic flights, a flight manoeuvre that artificially creates weightlessness and hypergravity, electrocortical activity as well as behavioural parameters (error rate and reaction time) and neuronal parameters (event-related potentials P300 and N200) were examined with an electroencephalogram. Thirteen participants solved a neurocognitive task (mental arithmetic task as a primary task and oddball paradigm as a secondary task) within normal as well as hypergravity condition in fifteen consecutive parabolas for 22 s each. No changes between the different gravity levels could be observed for the behavioural parameters and cortical current density. A significantly lower P300 amplitude was observed in 1 G, triggered by the primary task and the target sound of the oddball paradigm. The N200, provoked by the sounds of the oddball paradigm, revealed a higher amplitude in 1.8 G. A model established by Kohn et al. (2018) describing changes in neural communication with decreasing gravity can be used here as an explanatory approach. The fluid shift increases the intracranial pressure, decreases membrane viscosity and influences the open state probability of ion channels. This leads to an increase in the resting membrane potential, and the threshold for triggering an action potential can be reached more easily. The question now arises whether the observed changes are linear or whether they depend on a specific threshold.

Layperson Physiological Tolerance and Operational Performance in Centrifuge-Simulated Spaceflight.

INTRODUCTION: Prior study has indicated that individuals of varied age, medical history, and limited-to-no experience tolerate spaceflight conditions. We sought to expand upon the understanding of layperson response to hypergravity conditions expected in commercial spaceflight by exposing subjects, following minimal training, to centrifuge-simulated, high-fidelity commercial spaceflight profiles. We further explored how these individuals perform in simulated operational activities during and following hypergravity.METHODS: Volunteer subjects participated in up to five centrifuge runs (maximum +4.0 Gz, +4.5 Gx, 6.1 G resultant; onset rate <0.5 Gz · s-1, ≤1 Gx · s-1). Profiles included two winged spacecraft simulations with sequential and combined +Gx/+Gz and two capsule simulations representing nominal +Gx launch and reentry. The final profile simulated a capsule launch abort, with a more dynamic cycling of +Gx exposures and oscillatory multi-axis exposures simulating parachutes and water motion. Touchscreen tablets were used to administer pattern-replication tasks during and after profiles.RESULTS: A total of 46 subjects participated, including 4 diabetics and 9 with cardiac disease. There was increased frequency of motion sickness, subjectively associated with capsule-type profiles, and increased termination of participation compared to prior studies. There was no association between medical history, age, sex, or motion sickness history and tolerance or noncompletion. Tablet test errors were common; accuracy and time to completion were associated with age. There was no association between any time metric or accuracy and sex.DISCUSSION: This study improves understanding of layperson tolerance in commercial spaceflight analog conditions, and the capsular profiles broaden the applicability of the findings. The frequency of task errors highlights the potential for mistakes in operational activities when performed by laypersons.Blue RS, Ong KM, Ray K, Menon A, Mateus J, Auñón-Chancellor S, Shah R, Powers W. Layperson physiological tolerance and operational performance in centrifuge-simulated spaceflight. Aerosp Med Hum Perform. 2023; 94(8):584-595.

Lunar and mars gravity induce similar changes in spinal motor control as microgravity.

Introduction: Once more, plans are underway to send humans to the Moon or possibly even to Mars. It is therefore, important to know potential physiological effects of a prolonged stay in space and to minimize possible health risks to astronauts. It has been shown that spinal motor control strategies change during microgravity induced by parabolic flight. The way in which spinal motor control strategies change during partial microgravity, such as that encountered on the Moon and on Mars, is not known. Methods: Spinal motor control measurements were performed during Earth, lunar, Mars, and micro-gravity conditions and two hypergravity conditions of a parabola. Three proxy measures of spinal motor control were recorded: spinal stiffness of lumbar L3 vertebra using the impulse response, muscle activity of lumbar flexors and extensors using surface electromyography, and lumbar curvature using two curvature distance sensors placed at the upper and lower lumbar spine. The participants were six females and six males, with a mean age of 33years (standard deviation: 7years). Results: Gravity condition had a statistically significant (Friedmann tests) effect spinal stiffness (p < 0.001); on EMG measures (multifidus (p = 0.047), transversus abdominis (p < 0.001), and psoas (p < 0.001) muscles) and on upper lumbar curvature sensor (p < 0.001). No effect was found on the erector spinae muscle (p = 0.063) or lower curvature sensor (p = 0.170). Post hoc tests revealed a significant increase in stiffness under micro-, lunar-, and Martian gravity conditions (all p's < 0.034). Spinal stiffness decreased under both hypergravity conditions (all p's ≤ 0.012) and decreased during the second hypergravity compared to the first hypergravity condition (p = 0.012). Discussion: Micro-, lunar-, and Martian gravity conditions resulted in similar increases in spinal stiffness, a decrease in transversus abdominis muscle activity, with no change in psoas muscle activity and thus modulation of spinal motor stabilization strategy compared to those observed under Earth's gravity. These findings suggest that the spine is highly sensitive to gravity transitions but that Lunar and Martian gravity are below that required for normal modulation of spinal motor stabilization strategy and thus may be associated with LBP and/or IVD risk without the definition of countermeasures.

Operation of a programmable microfluidic organic analyzer under microgravity conditions simulating space flight environments

A programmable microfluidic organic analyzer was developed for detecting life signatures beyond Earth and clinical monitoring of astronaut health. Extensive environmental tests, including various gravitational environments, are required to confirm the functionality of this analyzer and advance its overall Technology Readiness Level. This work examines how the programmable microfluidic analyzer performed under simulated Lunar, Martian, zero, and hypergravity conditions during a parabolic flight. We confirmed that the functionality of the programmable microfluidic analyzer was minimally affected by the significant changes in the gravitational field, thus paving the way for its use in a variety of space mission opportunities.

Increase in steryl glycoside levels and stimulation of lipid raft formation in azuki bean epicotyls under hypergravity conditions

Sterols are the main components of the plasma membrane and are involved in various plant membrane functions. Azuki bean (Vigna angularis (Wild.) Ohwi et Ohashi) seedlings were cultivated under hypergravity conditions, and changes in the levels and composition of membrane sterols in their epicotyls were analyzed. Under hypergravity conditions at 300 g, the levels of steryl glycosides and acyl steryl glycosides per unit length and per gram fresh weight greatly increased, which accounted for an increase in the total sterol levels. Stigmasterol, β-sitosterol, and campesterol were the most abundant sterols. Hypergravity decreased the proportion of stigmasterol but increased that of β-sitosterol. The fatty chains of acyl steryl glycosides mainly consisted of palmitic acid (C16:0), stearic acid (C18:0), linoleic acid (C18:2), and α-linolenic acid (C18:3), and their proportions were not modified under hypergravity conditions. In addition, the density of membrane microdomains, visualized with anti-Flotillin 1 antibody per unit area, increased by hypergravity, suggesting that lipid raft formation was stimulated. These results support the hypothesis that lipid rafts are involved in plant response and resistance to gravity.

Hypergravity enhances RBM4 expression in human bone marrow-derived mesenchymal stem cells and accelerates their differentiation into neurons.

The regulation of stem cell differentiation is important in determining the quality of transplanted cells in regenerative medicine. Physical stimuli are involved in regulating stem cell differentiation, and in particular, research on the regulation of differentiation using gravity is an attractive choice. We have shown that microgravity is useful for maintaining undifferentiated mesenchymal stem cells (MSCs). However, the effects of hypergravity on the differentiation of MSCs, especially on neural differentiation related to neural regeneration, have not been elucidated. We induced neural differentiation of human bone marrow-derived MSCs (hbMSCs) for 10 days under normal gravity (1G) or hypergravity (3G) conditions using a gravity controller, Gravite®. HbMSCs were collected, and cell number and viability were measured 3 and 10 days after induction. RNA was also extracted from the collected hbMSCs, and the expression of neuron-associated genes and regulator markers of neural differentiation was analyzed using real-time polymerase chain reaction (PCR). Additionally, we evaluated the NF-M-positive cell rate 10 days after induction using immunofluorescent staining. Neural gene expression and the NF-M-positive cell rate were increased in hbMSCs under the 3G condition 10 days after induction. mRNA expression of RNA binding motif protein 4 (RBM4) and pyruvate kinase M 1 (PKM1) in the 3G condition was also higher than that in the 1G group. Hypergravity can enhance RBM4 and PKM1, promoting the neural differentiation of hbMSCs.

A Preliminary Investigation on the Geometrical Shape of Pulsating Heat Pipe under Hyper-Gravity Conditions

A Preliminary Investigation on the Geometrical Shape of Pulsating Heat Pipe under Hyper-Gravity Conditions

Hypergravity conditions inhibit elongation growth and polar auxin transport in epicotyls of etiolated pea seedlings

Hypergravity conditions inhibit elongation growth and polar auxin transport in epicotyls of etiolated pea seedlings

An Arabidopsis PTH2 Gene Is Responsible for Gravity Resistance Supporting Plant Growth under Different Gravity Conditions.

Terrestrial plants respond to and resist gravitational force. The response is termed “gravity resistance”, and centrifugal hypergravity conditions are efficient for investigating its nature and mechanism. A functional screening of Arabidopsis T-DNA insertion lines for the suppression rate of elongation growth of hypocotyls under hypergravity conditions was performed in this study to identify the genes required for gravity resistance. As a result, we identified PEPTIDYL-tRNA HYDROLASE II (PTH2). In the wild type, elongation growth was suppressed by hypergravity, but this did not happen in the pth2 mutant. Lateral growth, dynamics of cortical microtubules, mechanical properties of cell walls, or cell wall thickness were also not affected by hypergravity in the pth2 mutant. In other words, the pth2 mutant did not show any significant hypergravity responses. However, the gravitropic curvature of hypocotyls of the pth2 mutant was almost equal to that of the wild type, indicating that the PTH2 gene is not required for gravitropism. It is suggested by these results that PTH2 is responsible for the critical processes of gravity resistance in Arabidopsis hypocotyls.

Melting behavior and heat transfer performance in a modified PCM-filled enclosure with fins under hypergravity conditions

The latent heat energy storage (LHTES) system has been suggested for the thermal management of airborne equipment due to its superior thermal energy storage capability. The enthalpy-porosity method is used to investigate the melting heat transfer characteristics of phase change material (PCM) in embedded fin enclosures under hypergravity. The effects of different hypergravity values and directions on the melting process are analyzed. The results indicate that the melting is greatly accelerated by the fin due to its high thermal conductivity. Compared with the enclosure without fins, the addition of fins reduced the melting time by a maximum of 46.0%. Under the hypergravitational environment, natural convection is significantly enhanced, which leads to a more than 5 times increase in the maximum velocity of the liquid PCM as the gravity value increases from 1 g to 9 g. The direction of hypergravity also affects the heat transfer performance. Under hypergravity values of 5 g, the total melting time at θ = 0° is reduced by 60.24% compared to the case of θ = 90°. The findings of this study may contribute to the design of the LHTES system in aerospace applications.

Hypergravity Attenuates Reactivity in Primary Murine Astrocytes.

Neuronal activity is the key modulator of nearly every aspect of behavior, affecting cognition, learning, and memory as well as motion. Hence, disturbances of the transmission of synaptic signals are the main cause of many neurological disorders. Lesions to nervous tissues are associated with phenotypic changes mediated by astrocytes becoming reactive. Reactive astrocytes form the basis of astrogliosis and glial scar formation. Astrocyte reactivity is often targeted to inhibit axon dystrophy and thus promote neuronal regeneration. Here, we aim to understand the impact of gravitational loading induced by hypergravity to potentially modify key features of astrocyte reactivity. We exposed primary murine astrocytes as a model system closely resembling the in vivo reactivity phenotype on custom-built centrifuges for cultivation as well as for live-cell imaging under hypergravity conditions in a physiological range (2g and 10g). We revealed spreading rates, migration velocities, and stellation to be diminished under 2g hypergravity. In contrast, proliferation and apoptosis rates were not affected. In particular, hypergravity attenuated reactivity induction. We observed cytoskeletal remodeling of actin filaments and microtubules under hypergravity. Hence, the reorganization of these key elements of cell structure demonstrates that fundamental mechanisms on shape and mobility of astrocytes are affected due to altered gravity conditions. In future experiments, potential target molecules for pharmacological interventions that attenuate astrocytic reactivity will be investigated. The ultimate goal is to enhance neuronal regeneration for novel therapeutic approaches.

Effect of Twelve Week Hypergravity Training on Sprinting Speed of the Cricketers

Background: Sprinting speed as a derivative of lower-body power is considered to be the most vital component of physical ability of the players. Traditional training methods fail to improve sprinting speed of the experienced players up to a certain limit that demands newer training means for further development of speed. Hypergravity Training (HT) has been identified as such a new type of training that was used by few researchers for the improvement of sprinting speed and power of the experienced rugby and soccer players. But it has still not been implemented on the cricketers for the development of sprinting speed. Objective: Therefore, the current randomized control trial was directed to assess the development of sprinting speed of the cricketers through the implementation of HT in comparison with the Normalgravity Training (NT) condition. Method: The present study was a quasi-experimental research work. One hundred and five (N=105) state cricketers were selected as subjects. The participants were split into three equal groups (n=35 each) viz. i) Normalgravity Training Group (NGTG), ii) Hypergravity Training Group (HGTG) iii) Control Group (CG). NGTG HGTG groups underwent the same exercise protocol for the periods of twelve weeks in normal hypergravity conditions respectively whereas CG was free from the training intervention. Sprinting speed of the cricketers was measured by a 30m run test. ANCOVA preceded by Tukey’s LSD test were performed for data analysis. Statistical significance was examined at p.05 level. Results: Significant F-value (F=61.122; p 0.001) was observed. Sprinting speed of both training groups (NGTG HGTG) improved significantly (Mean Diff=1.28 0.86; Critical Diff =0.41) in comparison to the CG. HGTG also differed significantly (Mean Diff =0.42; Critical Diff =0.41) when compared with NGTG in sprinting speed. Conclusions: The sprinting speed of HGTG improved better than NGTG. Therefore, HT is found as an effective training means for developing sprinting speed.

Unraveling the mechanisms of aluminum solidification under hyper-gravity condition from molecular dynamics simulations

Gradient materials show excellent performance in combining strength, ductility, and fatigue resistance. In the present work, we proposed a novel hyper-gravity loading method and applied it to the solidification of aluminum using molecular dynamics simulation. A gradient structure is obtained after solidification, which is consistent with the experimental studies. The hyper-gravity-induced gradient pressure is identified as the main factor making the melting point, nucleation, and grain growth unevenly in the model, which leads to the decreased grain size along the hyper-gravity direction. Three solidification behaviors are observed in one solidification, i.e., homogenous nucleation initiates first at the bottom of the model, where it undergoes the highest pressure; then heterogeneous solidification combined with homogenous solidification appears in the middle; finally, directional solidification dominates because the insufficient undercooling makes the nucleation difficult. Moreover, the gradient structure and grain refinement are further enhanced with increasing gravity intensity.

The Microstructural Evolution of Nickel Single Crystal under Cyclic Deformation and Hyper-Gravity Conditions: A Molecular Dynamics Study

Turbine blades are subjected to cyclic deformation and intensive hyper-gravity force during high-speed rotation. Therefore, understanding the dynamic mechanical behavior is important to improve the performance of the blade. In this work, [001](010), [110](−110), and [11−2](111) pre-existing crack models of nickel single crystals under increasing cyclic tensile deformations were studied by using molecular dynamics simulations. In addition, a novel hyper-gravity loading method is proposed to simulate the rotation of the blade. Four hyper-gravity intensities, i.e., 1 × 1012 g, 3 × 1012 g, 6 × 1012 g, and 8 × 1012 g, and different temperatures were applied during the cyclic deformation. The fatigue life decreased rapidly with the elevated hyper-gravity strength, although the plastic mechanism is consistent with the zero-gravity condition. The stress intensity factor for the first dislocation nucleation indicates that the critical stress strongly depends on the temperatures and hyper-gravity intensities. Moreover, the crack length in relation to hyper-gravity intensity is discussed and shows anisotropy along the direction of hyper-gravity. A temperature-induced brittle-to-ductile transition is observed in the [001](010) crack model. The present work enhances our understanding of the fatigue mechanism under hyper-gravity conditions from an atomistic viewpoint.

Molecular dynamics study of fatigue behavior of nickel single-crystal under cyclic shear deformation and hyper-gravity condition

Dynamic mechanical properties play an essential role in governing the intrinsic fatigue behavior of superalloys. In this work, [001](010), [110](−110), and [101](010) pre-existing center cracks model of nickel single crystals under increasing cyclic shear deformations were studied by molecular dynamics simulations. More importantly, we introduced three hyper-gravity forces, i.e. 3 × 1012 g, 4 × 1012 g, and 5 × 1012 g, during the fatigue deformation to simulate the high-speed rotation of the blade. The stress intensity factor for the first dislocation nucleation indicates that the critical stress is strongly dependent on the hyper-gravity intensities and temperatures. The fatigue life decreased rapidly with the elevated hyper-gravity strength. Moreover, the [001](010) crack propagation shows a brittle-to-ductile transition at temperatures below 300 K and is suppressed at high temperatures. The crack length in the relation to hyper-gravity intensities is discussed and shows anisotropy along the direction of hyper-gravity. No crack propagation is observed in [110](−110) and [101](010) central crack models.

Numerical investigation on melting behaviour of phase change materials/metal foam composites under hypergravity conditions

The integration of electronic devices in aerospace vehicles leads to a significant increase in the heat dissipation, which makes thermal management a severe challenge. Due to the high thermal energy storage capacity and the excellent thermal diffusivity, phase change materials (PCM)/metal foam composite is a potential thermal management material. In order to deepen the understanding of melting behaviour of PCM/metal foam under hypergravity, the numerical model considering natural convection, flow resistance of metal foam, and non-equilibrium heat transfer is proposed, and the effects of inclination angle, hypergravity value, metal foam porosity, and pore density on the melting are analyzed. It shows that the inclination angle has a great influence on the morphology of the melting interface, while has limited influence on the variation of PCM liquid fraction. As the inclination angle changes from 0° to 180°, the heated wall temperature first decreases, and then increases after reaching the lowest value at 45°, which is the optimal inclination angle. With the rise of hypergravity value, natural convection is enhanced, the heated wall temperature is reduced, while the hypergravity value has limited effect on the PCM liquid fraction. Furthermore, with the increase of metal foam porosity, natural convection is enhanced, while the heated wall temperature and the melting time become larger. When the porosity is larger than 0.95, the effect of metal foam on natural convection suppression is greater than that of heat conductivity enhancement, leading to that the performance of PCM/metal foam is worse than that of the pure PCM. Besides, with the decrease of pore density, natural convection is enhanced, the heated wall temperature becomes lower. Therefore, metal foam with lower pore density is preferred. This paper provides guidance to the optimal design of PCM-based heat sink for aerospace applications.

Enhanced proliferation and differentiation of human mesenchymal stem cells in the gravity-controlled environment.

Human bone marrow mesenchymal stem cells (hMSCs) present a promising cell source with the potential to be used for curing various intractable diseases, and it is expected that the development of regenerative medicine employing cell-based therapy would be significantly accelerated when such methods are established. For that, powerful methods for selective growth and differentiation of hMSCs should be developed. We developed an efficient method for hMSC proliferation and differentiation into osteoblasts and adipocytes using gravity-controlled environments. The results indicate that the average doubling time of hMSCs cultured in a regular maintenance medium under microgravity conditions (0.001 G) was 1.5 times shorter than that of cells cultured under natural gravity conditions (1.0G). Furthermore, 99.2% of cells grown in the microgravity environment showed the expression of hMSC markers, as indicated by flow cytometry analysis. Osteogenic and adipogenic differentiation of hMSCs expanded in the microgravity environment was enhanced under microgravity and hypergravity conditions, respectively, as evidenced by the downregulation of hMSC markers and upregulation of osteoblast and adipocyte markers, respectively. Most cells differentiated into osteoblasts in the microgravity environment after 14 days (~80%) and adipocytes in the hypergravity environment after 12 days (~90%). Our results indicate that hMSC proliferation and selective differentiation into specific cell lineages could be promoted under microgravity or hypergravity conditions, suggesting that cell culture in the gravity-controlled environment is a useful method to obtain cell preparations for potential clinical applications.

Effect of mushy zone constant on the melting of a solid-liquid PCM under hyper-gravity conditions

Mushy zone constant is an important parameter of the enthalpy-porosity method which defines how the flow evolves within the cavity. The present numerical study investigates the effect of mushy zone constant (C = 1 × 104, 1 × 106 & 1 × 108 kg m−3 s−1) on the melting phenomena of a phase change material (PCM) under hyper-gravity conditions (2g, 5g, 10g and 20g). Value of ‘C’ influences the fluid velocity within the liquid region of PCM and its mobility during phase change process. The melting rate is enhanced by 32% as value of ‘C’ is reduced from 1 × 108 to 1 × 104 at normal gravitational conditions while heat transfer rate at hot wall improves as value of ‘C’ is decreased from 1 × 108 to 1 × 104 with maximum discrepancy being 83%. Under the combined effect of value of ‘C’ and hyper-gravity, the movement of liquid region within the cavity becomes distinct in comparison to the normal gravity condition. The melting rate is enhanced by 74% at ‘C’ = 1 × 104 & by 54% at ‘C’ = 1 × 104 as the convection within the liquid region also enhances.

Stability Studies of UV Laser Irradiated Promethazine and Thioridazine after Exposure to Hypergravity Conditions.

Pharmaceuticals carried into space are subjected to different gravitational conditions. Hypergravity is encountered in the first stage, during spacecraft launching. The stability of medicines represents a critical element of space missions, especially long-duration ones. Therefore, stability studies should be envisaged before the implementation of drugs for future deep space travel, where the available pharmaceuticals would be limited and restocking from Earth would be impossible. Multipurpose drugs should be proposed for this reason, such as phenothiazine derivatives that can be transformed by optical methods into antimicrobial agents. Within this preliminary study, promethazine and thioridazine aqueous solutions were exposed to UV laser radiation that modified their structures and generated a mixture of photoproducts efficient against particular bacteria. Subsequently, they were subjected to 20 g in the European Space Agency’s Large Diameter Centrifuge. The aim was to evaluate the impact of hypergravity on the physico-chemical and spectral properties of unirradiated and laser-irradiated medicine solutions through pH assay, UV-Vis/FTIR absorption spectroscopy, and thin-layer chromatography. The results revealed no substantial alterations in centrifuged samples when compared to uncentrifuged ones. Due to their stability after high-g episodes, laser-exposed phenothiazines could be considered for future space missions.