Microgravity Science and Technology最新文献

The temperature shock of solar panels causes a whole spectrum of disturbances. The most significant of them are indignation in the first seconds after a temperature impact. However, long-term thermal effects also induce disturbances. One such phenomenon is thermal deformation. Some studies indicate that thermal deformations in certain solar panel systems (for example, ROSA) can compromise the controllability of small spacecraft. However, modern literature lacks quantitative assessments of this impact. This work aims to quantify microaccelerations in spacecraft angular motion induced by thermal deformations of solar array panels. Such an assessment will establish management protocols to enhance the efficiency of executing target tasks for small spacecraft. Specifically, this involves gravitationally sensitive processes and high-precision remote Earth sensing from space.

The aim of this work was to study the influence of microgravity on the structural characteristics of the back musculoskeletal system. The studies were performed on 8 healthy volunteers before and after 3- and 5-days exposure to Dry Immersion (DI) using magnetic resonance imaging. The results of the studies showed that DI is accompanied by a decrease in the physiological curvature of the lumbar spine by an average of 3.51 ± 0.22° with a simultaneous increase in the intervertebral discs height: the most pronounced changes were registered between the lumbar vertebrae L2–L3, L3–L4 and L5–S1. Under immersion conditions, an increase in the height by an average of 1.89 ± 1.03 cm was also observed. According to the MRI studies, starting from the 3rd day of DI there were symptoms of muscles’ atrophy with a significant decrease in the cross-sectional areas of mm. quadratus lumborum, multifidus, erector spinae. During the first two days of DI, the volunteers experienced moderate back pain of 5.33 ± 2.76 points on a 10-point scale. At the same time, there was a high correlation between the severity of pain and a decrease in the cross-sectional areas of mm. quadratus lumborum and multifidus.

Changes in a cell phenotype occur under the influence of external and internal stimuli of a biochemical and/or physical nature, including gravity. This study is devoted to a comparative analysis of the characteristic reactions of breast cancer cells under different gravitational conditions using the statistical-thermodynamic model of their deformation caused by the orientation properties of the actin cytoskeleton of eukaryotic cells using the actin filament orientation parameter. The free energy form of the cell cytoskeleton is determined followed by a derivation of the evolution equation. The statistical-thermodynamic model describes the basic mechanical behavior of eukaryotic cells, including their viscoelasticity, power-law stress relaxation and fluidization under loading. Numerical modeling of cell cytoskeleton reactions to gravitational effects of different magnitudes, including values of 10^–6∙g and 1∙g, was performed. A comparative analysis of cytoskeleton deformation patterns was carried out based on which the peculiarities of the influence of gravity on the mechanical behavior of cells were established.

Natural convection inside a thin plate in a rectangular cabinet containing (Cu-Al_2 O_3) water hybrid nanofluids is carried out in the present study. The thin plate is positioned both vertically and horizontally at various locations within the cavity. An isothermal thermal boundary conditions was imposed to the plate. The upper and lower boundaries are maintained under adiabatic thermal boundary conditions, while the lateral boundaries are designated as an isothermal cold wall. Employing the FVM, the dimensionless governing equations alongside the corresponding boundary conditions are solved through numerical techniques. The power law scheme is implemented to address the convective terms effectively. The resultant system of linear equations is resolved utilizing the TDMA algorithm. The characteristics of flow and heat transfer are examined across various parameters, including Rayleigh number ((Ra = 10^6) and (10^7)), Hartmann number ((Ha = 0-100)), concentration of nanoparticles ((phi = 0.02-0.06)), and orientation of the magnetic field ((gamma =0^o - 135^o)). It is observed that the fluid flow pattern exhibits greater intensity at elevated Ra and diminished Ha. The rate of heat transfer (HT) is diminished with an increase in Ha. For both horizontal and vertical plates, the magnetic inclination angle (gamma = 90^o) usually produces the best HT improvement; however, extreme inclinations (gamma = 135^o) cause a number of intricate flow phenomena, which results in an insufficient HT rate. An escalation in the concentration of composite nanoparticles and Ra significantly enhances the Nusselt number. Composite nanofluid gives better HT performance than the single nanofluid. The average increase in Nu for (Cu-Al_2 O_3) water hybrid nanofluid is 5.63% when compared to the cavity filled with pure water.

As spacecraft continue to advance in scale, performance, and capabilities, their operational power requirements are projected to rise from kilowatts to megawatts or even gigawatts with voltages reaching the megavolt level. Under such conditions, traditional copper-based power transmission systems will incur substantial energy losses, resulting in an increase in both size and mass. Conversely, high-temperature superconducting (HTS) cables exhibit zero resistance and enable high-capacity transmission at liquid nitrogen temperatures, thereby facilitating lossless power and presenting significant potential for space application. The unique challenges presented by the space environment necessitate the development of specialized cryogenic thermal control systems (CTCSs) specifically designed for space-based HTS cables, underscoring the need for targeted research on CTCSs. This study presents a CTCS that employs pulse tube cryocoolers for cryocooling, cryogenic loop heat pipes for heat transfer, and cryogenic insulation technology to minimize parasitic heat leakage. A comprehensive examination of space cryogenic technologies, an analysis of existing problems, and a discourse on prospective research are presented.

Electrophoresis, a crucial technique in medical diagnostics, enables the control of individual particles, molecules, viruses, and bacteria during single-cell analysis. Ion-selective outer layers are often present in many viruses and bacteria. Theoretical and experimental studies on ion-selective granule electrophoresis reveal the existence of various nonlinear modes influenced by the strength of the electric field. Concentration polarization near such granules can lead to instability and chaotic behavior in sufficiently strong electric fields. While most research focuses on electrophoresis in Newtonian fluids, it is well-known that biological fluids exhibit non-Newtonian properties due to the presence of polymer molecules. This paper presents numerical simulations of electrophoresis in viscoelastic electrolytes modeled as Oldroyd-B and FENE-CR fluids. Microscale statement is considered, so gravitational and other inertial effects are neglected. For the electrophoresis of the first kind, we obtained the dependence of the granule’s electrophoretic velocity on polymer concentration and relaxation time. For the electrophoresis of the second kind, we found that the velocity can either increase or decrease with increasing polymer concentration, depending on the Weissenberg number. The presence of polymers led to the emergence of unsteady electrophoresis regimes caused by electrokinetic instability and concentration trace instability. The critical electric field strength values, indicating the onset of non-stationary electrophoresis modes when exceeded, were obtained.

The Random Positioning Machine (RPM) is a widely used method to alter the impact of gravity on biological systems by means of averaging the gravitational vector through random rotation. The aim of this work is to analyze the real motion of an RPM by qualitatively and quantitatively evaluating the resulting acceleration with regard to its averaging and uniform distribution. A scalable measuring device was developed that allows long-term measurements at several measuring points simultaneously. Acceleration averaging over time is depicted more generally for RPM motion using moving averages. The density representation on a sphere and the statistics according to Giné enable an evaluation of the distribution of gravity. The investigated metrics do not yet allow a direct statement about the suitability of simulated microgravity for biological experiments, but can serve as a basis for improvements to the RPM movement.

Screen channel liquid acquisition devices (LADs) are used to separate gas and liquid phases within a propellant tank in microgravity so that single-phase liquid can be extracted to the transfer line. Screen channel LADs rely on porous mesh screens and surface tension forces to allow liquid to flow while blocking vapor penetration. During the transient startup of propellant transfer, the liquid must be accelerated from rest to the steady flow demand velocity, which causes the screen to deform or comply. Compliance depends on multiple parameters, most notably the mesh type and open area. Recent testing has shown that the screen pretension level is also a variable that must be controlled and quantified. This paper presents new screen compliance design, testing, and experimental results to determine the effect of pretension. Testing is conducted on six screen meshes, two metal types, three open area aspect ratios, two orientations, and three tension levels. Results show that the screen compliance rate increases with increasing pretension in both linear and nonlinear regimes and that mesh type, metal type, open area, and orientation all affect compliance.

This study presents a comprehensive exploration of a theoretical model designed to measure the surface energy of solids under microgravity conditions. While numerous studies have investigated various techniques for determining the surface energy of solids through the use of pairs of liquids based on Young’s equation of contact angle, these methods often lack accuracy and are impractical in space-like environments due to safety concerns. In this investigation, we critically examine and validate the sessile drop accelerometry model, specifically developed for measuring the surface free energy of solids in microgravity conditions through the deposition of a single water droplet. This model encompasses a set of governing equations that enable the determination of interfacial energies as a function of changes in the droplet’s shape resulting from the release of gravitational energy. To validate and analyze the theoretical model, a sophisticated experimental payload was developed, and a series of rigorous experiments were conducted under both reduced gravity and hypergravity conditions, simulated using parabolic flight. The measured surface free energy values were compared against traditional polar-nonpolar-based surface energy measurement techniques, demonstrating strong agreement and highlighting the robustness of the SDAcc model. Through rigorous theoretical and experimental analyses, this study establishes a fundamental understanding of the influence of gravity on metastable droplet morphology and its implications for accurate surface energy determination. These findings will contribute to the advancement of interfacial science in reduced gravity environments and open new avenues for surface characterization techniques in space applications.

Access to reduced-gravity environments is a cornerstone of space research, enabling scientific experiments in space-like conditions. While parabolic flights have long served as an accessible platform for microgravity studies, their reliance on manual piloting limits precision and repeatability. This paper introduces an autonomous flight control framework designed to execute reduced-gravity maneuvers in large fixed-wing aircraft. The proposed system regulates all four phases of the maneuver by commanding a reference acceleration profile. This approach enables precise control over the aircraft’s acceleration, ensuring consistent reduced gravity conditions critical for experimental applications. The control architecture comprises three specialized controllers: one each for tangential and normal acceleration regulation and another for minimizing angle-of-attack variations to dampen pitch oscillations. The proposed framework is evaluated on a nonlinear Boeing 747 model implemented in MATLAB Simulink. Simulation results show that the controller maintains residual accelerations within (pm 0.02,g) for zero-, lunar-, and Martian-gravity manoeuvres, matching the error margins reported in published flight data. Key challenges are addressed, such as non-minimum phase dynamics, altitude-dependent air density variations, and pitch oscillations at the center of gravity. These findings contribute to the advancement of autonomous flight control for more reliable and precise reduced-gravity research.