Microgravity Science and Technology最新文献

Lithium-ion batteries are a feasible solution to store energy efficiently. However, in safety-critical environments such as the suborbital rockets, the introduced technologies do not may compromise safety. This research explores the possibility of replacing Ni-MH batteries with Li-ion batteries. However, before replacing technologies, the reliability of Li-ion cells needs to be evaluated, and the potential benefits must be considered against the risks to ensure the mission’s success. The main objective is to ensure the safety and integrity of suborbital missions during the technology transition. To assess the technology exchange, a method where the battery cell experiences a sequence of tests that cover aspects of safety encountered during the vehicle missions, such as vacuum, capacity, short circuit behavior, over-current discharge, behavior at higher environment temperature, and pulsed discharge behavior. To experience the proposed method, two Li-ion cells commercial off-the-shelf (COTS) from different manufacturers are evaluated. The results indicated that only one of the two cell models evaluated can substitute the Ni-MH. This research concludes that replacing Ni-MH cells with Li-ion cells is feasible, for such an application. The proposed acceptance flow design based on the test collectively validates the replacement, showing that the Li-ion cells can offer reliability, safety, and efficiency to suborbital vehicles to fulfill this mission profile.

Microgravity offers an enticing synthetic knob for materials scientists to explore—however, this environment creates major challenges in hardware development that can turn a simple 3-day experiment into a 3-year long nightmare. This paper provides an overview of engineering an autoclave, compatible with NASA’s Solidification Using a Baffle in Sealed Ampoules (SUBSA) furnace, to enable microgravity hydrothermal synthesis—an acceleration-sensitive technique that processes aqueous samples above the boiling point of water. Hydrothermal synthesis is a universal chemical transformation technique that is used to produce a range of advanced materials with applications in alternative energy, healthcare, and the food industry. In this work, we use the synthesis of graphene hydrogel as a case study to verify our hardware design on Earth before launching to the International Space Station for microgravity testing. The design addresses pertinent challenges which include enabling thermal expansion while preventing air bubble formation in solution and implementing a pressure fail-safe above the maximum operating temperature. Our goal in presenting this autoclave design is to provide a step forward towards commercial-of-the-shelf microgravity hardware.

This paper numerically analyzes the influence of Dufour/Soret and space-dependent internal heat source (exponential decaying form) on combined convection (entire regime) of non-Newtonian fluids (power-law model of Ostwald-de-Waele) flow past a vertical full cone in porous media with the boundary conditions of VHF/VMF case. The transformed governing equations (non-similar equations) are solved by Keller box method (KBM). Numerical data for the dimensionless temperature profile, the dimensionless concentration profile, the local Nusselt number and the local Sherwood number are graphically and tabularly presented for the nine parameters: the buoyancy ratio (N), the Lewis number (Le), the Dufour parameter (Df), the Soret parameter (Sr), the cone angle parameter (m), the mixed convection parameter (xi), the VHF/VMF exponent (lambda), the non-Newtonian fluid power-law index (n), the space-dependent internal heat source coefficient ({A}^{*}). The increase of the buoyancy ratio (N) and the VHF/VMF exponent (lambda) tends to increase both the local Nusselt number and the local Sherwood number. The Nusselt number enhances with increasing the Soret parameter (Sr). Increasing the Lewis number (Le), the Dufour parameter (Df), the space-dependent internal heat source coefficient ({A}^{*}) enhances the Sherwood number. When the power-law index (n) is decreased, the local Nusselt and Sherwood numbers are increased. The physical aspects of the problem are discussed in details.

A numerical modelling of electrophoresis of dielectric particle is proposed under low and moderate homogeneous electric fields. As surface charge at the surface of the particle increases, nonlinear effects associated with surface conduction become more prominent. Current analytical methodologies addressing this issue employ asymptotic techniques, necessitating the establishment of effective boundary conditions. Consequently, solutions within the thin boundary layer, which substantially contribute to the emergence of nonlinear phenomena, are overlooked. While the asymptotic approach is capable of capturing principal effects, it falls short in providing a comprehensive understanding of the complete picture with non-linear effects. Our numerical modelling, incorporating a full formulation, is designed to bridge this knowledge gap. The numerical algorithm is tested in this work for the case of dielectric particle and can be readily extended to other particle types by altering the boundary conditions. The proposed method can be effortlessly generalized for various particle categories, such as ion-selective, flexible, biological, Janus particles, and those with hydrophobic surfaces. It operates without constraints concerning Debye, Dukhin, and Péclet numbers, which are associated with the emergence of nonlinear effects. The numerical algorithm was validated using an analytical solution for a weak electric field and experimental results for moderate and high electric fields. It was found that the electric field intensity and the surface charge density on the particle have the most significant impact on the emergence of non-linear effects. When there is a high degree of non-linearity, a structure of thin boundary layers nested within one another forms around the particle’s surface. In particular, the formation of a space charge region (SCR) around a non-conducting surface was discovered. It was previously believed that SCR only forms around surfaces with ion-exchange properties.

Opposed-flow flame spread over solid materials has been investigated in the past few decades owing to its importance in fundamental understanding of fires. These studies provided insights on the behavior of opposed-flow flames in different environmental conditions (e.g., flow speed, oxygen concentration). However, the effect of confinement on opposed-flow flames remains under-explored. It is known that confinement plays a critical role in concurrent-flow flame spread in normal and microgravity conditions. Hence, for a complete understanding it becomes important to understand the effects of confinement for opposed-flow flames. In this study, microgravity experiments are conducted aboard the International Space Station (ISS) to investigate opposed-flow flame spread in different confined conditions. Two materials, cotton-fiberglass blended textile fabric (SIBAL) and 1 mm thick polymethyl methacrylate (PMMA) slab are burned between a pair of parallel flow baffles in a small flow duct. By varying the sample-baffle distance, various levels of confinement are achieved (H = 1–2 cm). Three types of baffles, transparent, black, and reflective, are used to create different radiative boundary conditions. The purely forced flow speed is also varied (between 2.6 and 10.5 cm/s) to investigate its interplay with the confinement level. For both sample materials, it is observed that the flame spread rate decreases when the confinement level increases (i.e., when H decreases). In addition, flame spread rate is shown to have a positive correlation with flow speed, up to an optimal value. The results also indicate that the optimal flow speed for flame spread can decrease in highly confined conditions. Surface radiation on the confinement boundary is shown to play a key role. For SIBAL fabric, stronger flames are observed when using black baffles compared to transparent. For PMMA, reflective baffles yield stronger flames compared to black baffles. When comparing the results to the concurrent-flow case, it is also noticed that opposed-flow flames spread slower and blow off at larger flow speeds but are not as sensitive to the flow speed. This work provides unique long-duration microgravity experimental data that can inform the design of future opposed-flow experiments in microgravity and the development of theory and numerical models.

Short-radius centrifugation (SRC) is a promising and economically feasible countermeasure in space flight and applies to gravity therapy in terrestrial medicine. The potential occurrence of undesirable orthostatic and vestibular reactions limits the use of this method. One way to minimize these risks is the ability of a human to adapt to the effects of overload. It is known that artificial gravity training may improve orthostatic tolerance. New data demonstrated that cardio-postural interactions and muscle-pump baroreflex activation are present during short-arm centrifugation. Based on previous studies, we hypothesized that repeated SRC in the interval training mode with angular velocities from 22 to 28 rpm may also improve postural tolerance. Six healthy male volunteers were observed before and immediately after five consecutive SRC sessions. The rest between SRC was at least three days. The SRC mode was an interval and included five 300-second platforms with 1.27 g at the feet and four 300-second platforms with 2.06 g at the feet. We registered the main postural characteristics and ground reaction forces data when the participant kept the center of pressure at a given point in a standing position with biofeedback and without this. After the first SRC session, there was a significant posture decondition. The SRC training effect was already noticeable after the second SRC session and was stable until the end of the experiment. The results demonstrate the development of postural tolerance to artificial gravity exposure in this mode and expand the understanding of sensorimotor adaptation capabilities.

Brazil has a Microgravity Program mainly based mainly on sounding rockets experiments. The Santa Branca Mission, aimed to qualify the Brazilian Suborbital Microgravity Platform (MQ-MSP). The group of the Coordination of Applied Research and Technological Development (COPDT) of the Brazilian Space Research Institute (INPE) participated with an experiment in a fast solidification furnace, capable of producing temperatures up to 900 °C, which was tested with semiconductor and metal alloys. This paper describes the construction and performance of this furnace during the last suborbital flight, the Santa Branca Mission, which took place in 2022. The solidification furnace is now qualified and ready to be used by other institutions for sounding rocket flights.

For small droplets undergoing phase change, gravity is generally considered negligible. In the case of binary droplets evaporation, convective flows can be induced due to various mechanisms, such as continuity, buoyancy and/or selective evaporation of one of the components. Convection can also be induced by surface tension gradients resulting from concentration variations along the interface. This study presents experimental results of evaporation for binary mixture droplets. We concurrently investigate sessile and pendant droplets to assess gravity’s impact on binary droplet evaporation. We examine compositions including, pure butanol, pure methanol, pure water, and 50% per volume mixtures of water-butanol and water-methanol, evaporating in a controlled atmosphere. In the case of water-butanol mixtures, the drops contact line ‘depins’ during the evaporation process whereas the case of water-methanol mixture, the contact line of the drops remains pinned most of the lifetimes. The analysis of the evaporation dynamics reveals differences in the evaporation of these two mixtures and the effect of orientation (gravity). For water-butanol mixtures the evaporation occurs in four stages linked to preferential evaporation of the more volatile component and the ensuing surface tension gradients. In the case of water-methanol mixtures, contact lines tend to be pinned during most of the lifetimes of drops. The evaporation rate of the mixture is found to be between the ones of the pure components, i.e. water and methanol. The case of sessile drops exhibits a slight enhancement in evaporation rate in the case of the sessile configuration compared to the pendant one for pure water and mixture cases, which is explained by density differences and buoyancy driven flows. Solutal Marangoni flows in the case of water-methanol mixtures are deemed weaker compared to water-butanol ones. The use of the two mixtures allowed to have a good comparison between two cases where solutal-Marangoni effect can be strong (water-butanol) and weak (water- methanol) influence. The densities of the two organic liquids also highlighted gravitational effect due to the large difference in vapor densities.

Three-dimensional (3D) particle tracking is a challenging task in dense granular systems. Magnetic particle tracking has been developed in recent years to reconstruct a tracer’s trajectory in granular systems. The method can be low-cost, compact, and flexible. In this work we applied a Hall sensor array method to track the trajectories of a magnetic intruder particle in a 3D granular bed in the centrifuge of the Chinese Space Station (CSS). We present a developed algorithm. By placing sensors in an array in a same plane, our algorithm can exclude the interference of varying external field. The method’s static accuracy can reach 0.02 cm, and the maximum deviation of our measurement from a known path is also checked to be 0.02 cm. On CSS, two independent sensor arrays are used to cross-check the accuracy of the method. The two measured trajectories are well overlapped. This confirms the method’s reliability and robustness of tracking an intruder in a dense granular bed.

The stability of thermocapillary flow in a liquid bridge under a transverse rotating magnetic field (RMF) was numerically investigated by the linear stability analysis using the spectral element method. Three commonly used RMF models, namely, the infinite model, the simplified finite model and the Φ₁-Φ₂ model, are employed to describe the RMF and their results are compared. Additionally, for the Φ₁-Φ₂ model, the uniform and non-uniform RMF were also compared. The numerical results show that with the increase of magnetic Taylor number Ta, the critical Marangoni number (Ma_c) for the three RMF models increases firstly, then decreases sharply to a minimum, finally increases again when the RMF is strong enough to suppress the radial and axial convection induced by thermocapillary force. Two transitions between the wavenumber k=1 and k=2 mode are observed with increasing Ta. The results obtained by the simplified finite model are in good agreement with those of the Φ₁-Φ₂ model, however, the infinite model has a significant deviation compared to the Φ₁-Φ₂ model. Besides, the results indicate that the non-uniform RMF has a relatively weak action compared with the uniform RMF.