Microgravity Science and Technology最新文献

The results of an experimental study of the effect of hydrodynamic flow and injection of air bubbles on the spatial distribution and activity of cavitation events in a laboratory model of a flow sonochemical reactor are presented. The relevance of the work is due to the prospects of using acoustic cavitation by ultrasound in microgravity, where the absence of the buoyancy force fundamentally changes the behavior of multiphase media. The experiments were performed using the modified foil test method, which makes it possible to build maps of cavitation activity and monitor the dynamics of aluminum foil fracture that in the absence of a hydrodynamic flow, cavitation manifests itself in the form of horizontal zones spaced vertically, corresponding to the antinodes of a standing wave. A fluid flow leads to the formation of a single domed zone above the transducer and an increase in the fracture area. Aeration also forms a single zone, but sharper and elongated; the final area of destruction is comparable to the regime without aeration, but erosion occurs much earlier.

Our study employs a percolation approach to describe flame spread and group-combustion excitation in randomly distributed fuel-droplet clouds based on findings obtained from space-based microgravity experiments on the flame-spread limit around interactive droplets. We developed a percolation model in which the flame spreads to droplets existing within the flame-spread-limit distance, which varies depending on the relative positions of two or three flame-spreading droplets. Using 2D- and 3D-percolation models, we investigated the effects of two-droplet and/or three-droplet interaction on the flame spread of randomly distributed droplet clouds and group-combustion excitation. The results show that the critical mean droplet spacing, around which the occurrence probability of group combustion sharply decreases as mean droplet spacing increases, increases with two-droplet interaction both in the 2D- and 3D-percolation models. However, even when three-droplet interaction is taken into account in the 2D-percolation model, the critical mean droplet spacing does not increase to the same extent as it does under two-droplet interaction. The critical mean droplet spacing in the 3D-percolation model is larger than that in the 2D-percolation model. The proportion of droplets ignited solely by droplet interaction relative to the total number of droplets is higher in the 3D-percolation model than in the 2D-percolation model because the increase in dimensionality leads to an increase in the number of droplets ignited solely by droplet interaction.

The effect of the chemical potential difference on the development of diffusion processes in liquid systems with an interfacial boundary was studied experimentally. The study was conducted using the example of mass transfer of a surfactant between a droplet and the surrounding medium. Water and a mixture of benzene and chlorobenzene were selected as the contacting liquids. Acetic acid, which has significantly different solvation energies in water and in the coctacting mixture, was used as the diffusing surfactant. A Fizeau interferometer was used to visualize the flow patterns and concentration fields. It was shown that in liquid systems with an interfacial boundary, the direction and intensity of surfactant diffusion are determined by the difference in chemical potentials between the contacting solutions. A comparison was made of the structures of surfactant concentration fields arising as a result of its diffusion from a droplet or into a droplet, as well as their evolution. Particular attention was paid to the influence of Marangoni convection accompanying the surfactant diffusion process.

Suborbital spaceflight platforms are increasingly being considered as accessible environments for conducting life-science research under spaceflight conditions. Biological investigations during space missions play an important role in improving our understanding of the physiological, cellular, and molecular responses elicited by spaceflight-related stressors, thereby contributing to the scientific knowledge required to support astronaut health and the development of future space exploration programs. As access to suborbital platforms expands, appropriate laboratory facilities are needed to collect, preserve, and process biological samples within the constraints imposed by flight operations. This note describes the planning, deployment, and operations of a temporary biomedical laboratory established at Spaceport America in support of the Virtute-1 mission, conducted during Virgin Galactic’s Galactic-01 research flight. The laboratory was designed to support biomedical activities involving both human participants and cellular payloads, including pre- and post-flight biological sample collection, cell-culture management, cold-chain preservation, and logistics associated with the transport of biological materials and scientific equipment. The laboratory was integrated within the flight environment of the Gateway to Space facility and required coordination of aerospace, biomedical, clinical, regulatory, and logistical stakeholders from public and private institutions. Particular attention was dedicated to biosafety procedures, infrastructure adaptation, equipment deployment, transportation planning, and mission-driven workflow integration. This paper describes how these activities were organized and implemented during a commercial suborbital mission. The experience gained during Virtute-1 provides practical considerations for the deployment of biomedical laboratories at commercial spaceports and for future life-science investigations using suborbital platforms.

Graphical Abstract

Ground-based verification of space active vibration isolation systems faces fundamental challenges because traditional gravity compensation methods - such as quasi-zero stiffness mechanisms, suspension systems, and magnetic levitation - cannot simultaneously realize an ideal microgravity state across multiple degrees of freedom (DOFs) due to mechanical coupling. A horizontal air-bearing platform can provide near-frictionless motion in two horizontal translational DOFs and rotation about the vertical axis, thereby emulating three ground-accessible DOFs simultaneously. However, whether this environment provides an adequate equivalent for the translational vibration-isolation performance of a six-DOF space system, and whether sufficient long-term stability can be maintained, remain important questions. In this paper, we establish a six-DOF dynamic model of the air-bearing isolation system and derive the conditions under which three-DOF air-bearing tests can provide equivalent evaluation of the translational isolation performance of the full six-DOF system. We then design a verification environment comprising an air supply circuit, air-bearing structures, and a high-precision measurement and control system. Based on this platform, we conduct static control, wide-band excitation, and long-term stability tests on the active vibration isolation system, and evaluate the influence of the air-bearing environment on isolation performance. Both theoretical analysis and experimental results demonstrate that the air-bearing simulation method can effectively substitute for the space microgravity environment in verification, offering a viable technical pathway for performance testing of active vibration isolation systems.

Long-duration human missions to mars will expose astronauts to approximately six to eight months of microgravity, prolonged confinement, communication delay, and limited medical support, all of which may compromise physiological capacity and mission readiness. Major challenges include skeletal muscle atrophy, bone mineral loss, cardiovascular deconditioning, fluid redistribution, metabolic disturbance, and reduced functional work capacity. Because these adaptations affect multiple systems simultaneously, exercise remains the primary operational countermeasure for preserving musculoskeletal, cardiovascular, and metabolic function. However, Current exercise protocols derived from ISS operations provide the main operational evidence base, but they may not be fully optimized for exploration-class missions. Based on this evidence, we propose a phase-specific physical activity framework for mars transit. This review synthesizes current evidence on the physiological consequences of prolonged microgravity and evaluates exercise as a multisystem countermeasure for mars transit. We propose a phase-specific physical activity framework that includes low-intensity daily movement for circulatory support, immune regulation, and behavioral stability; moderate-intensity aerobic exercise for cardiovascular maintenance; and high-intensity interval and resistance training for preserving muscle mass, strength, neuromuscular performance, and bone integrity. Practical considerations, including equipment limitations, adherence, injury risk, and the interaction between exercise and energy balance, are also discussed. Overall, the evidence supports a targeted and integrated exercise prescription model in which exercise is framed not as general fitness practice, but as a mission-critical strategy for preserving astronaut health, functional independence, and operational capability during deep-space exploration.

Currently, 2 dimensional and 3-dimensional clinostats (2D and 3D Clinostats), random positioning machines (RPMs) and other ground-based simulation techniques are very important tools for space biology research. However, their performance and validity are almost always assessed by observations or isolated parameters that often inadequately explain the mechanical microenvironment experienced by biological samples like cells and tissues. This leads to lack of uniformity and reproducibility specially in the case of biological experiments. The cells might act differently within same conditions of simulated microgravity in different experiments due to lack of a standardised quantitative framework to asses every aspect of simulated microgravity beyond vector averaging. In this study we compute Biological Microgravity Evaluation Framework (BMEF), which is a comprehensive computational step by step method to evaluate mechanical stability, directional isotropy, vector orientation coverage and biologically relevant exposure generated during a simulated microgravity study. In this current study we have used a 3D clinostat with partial RPM features, where the inner frame changed its orientation randomly within a 10 s timeframe. Acceleration data through a 3-axis accelerometer, at 24 min, 48 min, 96 min and 120 min was obtained and gravity vector dynamics were characterised. This quantitative framework combines available physical parameters, resultant mechanical loading, Directional Bias Vector (DBV), Orientation Coverage Index (OCI), and Orientation Uniformity Index (OUI) with novel biologically relevant parameters, Mechanical Quality Score (MQS), Effective Isotropic Exposure Time (EIET) to generate a Biological Microgravity Quality Index (BMQI). We observed that orientation of sampling became denser with duration of experiments and EIET increased proportionally with exposure duration while BMQI converged rapidly in the initial phase of the study then remained stable thereafter. This framework is intended to provide a quantitative descriptor of mechanical exposure conditions for future biological experiments.

Nonlinear regimes of thermocapillary convection in a thin liquid film with a free surface resting on a rigid substrate subjected to vertical vibrations and imposed vertical temperature gradient are investigated. From the standpoint of interfacial stability, the system is governed by several competing mechanisms, namely gravitational, capillary, and vibrational forces, together with thermocapillary effects. The linear stability analysis demonstrates that gravity and capillary forces exert a stabilizing influence, whereas thermocapillary mechanism destabilizes the system. Within the adopted long-wave approximation, the vibrational mechanism is also found to have a stabilizing effect. A weakly nonlinear analysis is performed to characterize the system behavior in the vicinity of the instability threshold. It is shown that weak external vibrations increase the instability threshold, while sufficiently strong vibrations reduce it. The full averaged nonlinear system of governing equations is solved numerically using the Radau IIA integration scheme. The results reveal a pronounced sensitivity of the system to the amplitude of the initial perturbations. Increasing the perturbation amplitude is shown to promote destabilization, whereas larger perturbation wavenumbers enhance the stability of the system. Stability map is constructed for different values of the imposed temperature gradient. In addition, stability maps are obtained for various gravitational conditions, including microgravity and zero-gravity environments. It is demonstrated that vibrational forcing can stabilize the system even in the absence of gravity. The results of the nonlinear analysis of the averaged governing equations are consistent with the predictions of the previously obtained linear stability analysis while providing additional insight into the system dynamics beyond the linear instability threshold.

Understanding the onset of nucleate boiling (ONB) in different gravitational environments is crucial for industrial and space applications of flow boiling systems. This study presents a comparative analysis of ONB behavior in microgravity (µg) and Earth gravity (1g) environments to identify key differences. Boiling experiments were conducted using NASA’s experimental facility Flow Boiling and Condensation Experiment (FBCE) in microgravity aboard the International Space Station (ISS), and under Earth gravity conditions on a brassboard facility at NASA Glenn Research Center. Experiments were performed in a narrow rectangular channel using n-perfluorohexane (nPFH) as the working fluid, with inlet subcooling ranging from 6 to 24 °C and mass fluxes between 200 and 3000 kg/m²s under single-side heating. Wall temperatures were measured using embedded thermocouples, and flow visualization was obtained using a high-speed camera. Analysis of transient wall temperature profiles revealed distinct ONB behaviors in µg and 1g. In µg, multiple ONB-like events characterized by wall temperature drops occurred, whereas ONB was observed only once in 1g. Bubble nucleation at ONB was distributed along the entire channel length in µg but was confined to the downstream region in 1g. The ONB temperature drop profile was flatter in microgravity, indicating more spatially distributed nucleation compared to the localized behavior in 1g. Additionally, the transient behavior of bulk fluid temperature, inlet and outlet pressure, and mass flux during ONB was analyzed. Finally, two non-dimensional correlations were developed to predict ONB heat flux and superheat for µg and 1g conditions within the investigated operating ranges, showing reasonable agreement with experimental data.

Biological experiments under altered gravity conditions as encountered on sounding rockets often require automated in-flight chemical fixation under the challenging environmental and operational constraints, as accompanying any spaceflight mission. Enabling in-flight fixation while maintaining laboratory-equivalent cultivation conditions from ground handling to recovery poses significant challenges for reliability and reproducibility of experiment scenarios. A common flight-qualified architecture can address these constraints by enforcing controlled environmental and operational execution while decoupling sample-dependent fixation configurations through modular payload integration. This work describes a reusable, automated and standardized fixation payload platform designed to host interchangeable, pre-qualified chemical fixation payloads for biological experiments on a variety of platforms to achieve altered gravity. The module provides a standardized mechanical, thermal and electrical architecture for the integration and operation of experiments employing either adherent or suspension-based cells within a single flight-qualified unit, independent of the specific fixation configuration required. Hardware and operational performance were qualified within the German Aerospace Center’s (DLR) Materialphysikalische Experimente unter Schwerelosigkeit (MAPHEUS®) sounding rocket program. Laminar In-flight Fixation Technology (LIFT) was successfully flown across several missions and payload configurations, in-flight data demonstrate reliable execution of fixation procedures, stable thermal regulation, a pressure-stabilized internal environment and automated housekeeping data acquisition. The presented work establishes LIFT as a versatile, spaceflight-proven module to carry out a wide variety of cell culture experiments, allowing customizable in-flight fixation of samples as well as their monitoring within a common architecture.