Microgravity Science and Technology最新文献

Previous investigations have demonstrated that gravity has a significant impact on laminar jet flames. While significant progress has been made, the effects of the magnitude and direction of gravity on laminar jet diffusion flames remain poorly understood. To this end, a series of laminar non-premixed methane/air jet flame simulations is conducted in this work, considering zero gravity, normal gravity, and supergravity in both positive and negative directions relative to the direction of the fuel jet inlet. The results indicate that both flame height and flame width decrease as the magnitude of gravity increases. Analysis of heat release rate and elemental reactions reveals that supergravity can enhance local reaction rates and heat release. The influence of gravity on the flames is further examined in the mixture fraction space. It is found that increasing the magnitude of gravity decreases the mixing time scale, resulting in some oxygen penetrating through the flame front into the interior of the flame. Furthermore, the results show that gravity primarily affects the radial (axial) direction of the jet flame under normal (negative) gravity conditions.

Reduced-gravity flight is a critical enabler for microgravity research, technology demonstration, and human spaceflight preparation. Among available platforms, aircraft performing parabolic maneuvers provide a practical and repeatable means of generating short-duration reduced-gravity environments. Achieving precise and sustained g-level profiles during these maneuvers, however, poses significant challenges due to nonlinear aircraft dynamics and environmental disturbances. This paper presents a comprehensive survey of control methodologies for reduced-gravity flight, covering manned aircraft, fixed-wing UAVs, and multirotor systems. The review traces the evolution from early nonlinear and gain-scheduled approaches to advanced acceleration-feedback architectures designed for improved robustness and disturbance rejection. Each method is examined in terms of control structure, implementation complexity, and performance metrics, including residual acceleration and maneuver duration. Validation strategies, ranging from high-fidelity simulation and hardware-in-the-loop testing to real-flight demonstrations, are compared to assess technological maturity. Key gaps are identified, including the absence of full-scale autonomous parabolic flights, and future research priorities are outlined in adaptive and fault-tolerant control, trajectory optimization, and airframe design innovations to enable reliable, autonomous reduced-gravity operations. Beyond surveying methods, this review codifies application requirements, distills recurring control challenges into design patterns, and offers concise practitioner guidance that links controller choices to reported residual-g performance across platforms.

This study presents a comprehensive theoretical investigation of nonlinear dust-acoustic (DA) wave dynamics in a nonthermal complex plasma environment, with a particular focus on the effects of gravity and microgravity. By employing Sagdeev pseudo-potential analysis and considering both constant and variable dust charge scenarios, we demonstrate the fundamental role of external fields and suprathermal electron populations in modulating wave structures. Under microgravity, the plasma supports the coexistence of both compressive and rarefactive DA solitons due to a symmetric double-well potential profile, with charge variability significantly enhancing soliton amplitude, especially for rarefactive modes. In contrast, gravity breaks this symmetry, suppresses compressive solitons, and induces spatial asymmetry and oscillatory electric field structures due to gravito-electrostatic coupling and dust stratification. Furthermore, we establish a physical equivalence between increasing nonthermal electron effects (via the non-thermal parameter (alpha)) and reducing dust grain mass, both of which enhance the charge-to-mass ratio and deepen electrostatic confinement. This equivalence, however, is shown to hold only under microgravity. Analytical scaling relations and numerical simulations reveal that microgravity enables a charge-driven regime, while gravity imposes density-dominated dynamics. These findings provide new insights into the behavior of nonlinear structures in dusty plasmas and offer relevant interpretations for plasma conditions in both space and laboratory settings such in parabolic flight experiments.

In a low-gravity (g/6) environment, the high flow rate is maintained while buoyant convection is somewhat suppressed compared to conditions in terrestrial gravity (1g) and microgravity (10⁻⁴g), potentially promoting crystal growth via the melt method. To investigate the heat transfer mechanisms and the crystal growth/solidification process of CdTe crystals grown using the Vertical Bridgman (VB) method in g/6 conditions, two-dimensional axisymmetric numerical simulations were performed based on COMSOL simulation software. Comparison of the simulation results for temperature and flow fields in 1g, g/6, and 10⁻⁴g environments reveals that, the melt flow penetrates a low-temperature melt layer at g/6, resulting in a density-layer penetration effect that mitigates heat accumulation and reduces the streamline bending observed in 1g conditions. However, at g/6, a relative flow also forms above the solid–liquid interface, leading to the greatest interface bending and the steepest temperature gradient among the three gravitational conditions. This phenomenon may promote the accumulation of impurities and defects while simultaneously stabilizing the solid–liquid interface. Finally, a dimensionless parameter is introduced to elucidate the simulation phenomena and confirm the accuracy of the simulations.

The behavior of a system composed of two superposed thin liquid films on a solid substrate under modulated heating is investigated theoretically. The linear stability of the examined system is studied by applying a longwave lubrication approximation, and the resulting equations are analyzed. The system’s stability maps were plotted based on different parameter sets. The numerical analysis reveals oscillatory and monotonic modes of instability existing in the absence of heat modulation, as well as subharmonic and higher resonant modes. Such parametric instability modes can often become the most unstable for moderate modulation. At the same time, for modes that exist without heat modulation, in particular, monotonic ones, the intense heat modulation is shown to have a stabilizing role in many cases.

Free and forced oscillations of a hemispherical gas bubble on a rigid parallel plate surrounded by an incompressible liquid layer with a free surface in a uniform pulsating pressure field are considered. A model is proposed for describing the substrate surface heterogeneity through the wetting parameter (Hocking parameter), which is a proportionality coefficient between the contact line velocity and the contact angle deviation. The surface heterogeneity is important only near the contact line due to small-amplitude oscillations, which allows considering the form of surface heterogeneity as a function of one spatial variable. An external action excites only axisymmetric oscillations, shape oscillations arise due to the contact line movement along the substrate surface, but azimuthal modes are also excited by heterogeneity and their spectrum depends on the plate heterogeneity. In addition, the frequency of volume oscillations depends on the gas pressure in the bubble, so that this frequency can be equal to the frequency of bubble shape oscillations of any mode. The problem is solved using a Fourier series expansion in basis functions. The resulting system of amplitude equations is solved numerically due to its cumbersome nature.

Aboard the variable-gravity research rack (VGR) of the Chinese Space Station, scientists can conduct experiments under reduced gravities in a centrifuge. This study analyzes the spatial distribution effects of centrifugal gravitational fields and Coriolis force effects in the granular collapse experiments conducted in the centrifuge. Under the ground-based 1 g and space equivalent 1 g conditions, we have investigated the influences of centrifugal equivalent gravitational fields on the granular collapsed deposition shape. The granular column collapse has formed a complex deposition shape with the middle section slope angle close to the angle of repulse of the granular material. Both the horizontal centrifuge acceleration component and the Coriolis force in the space centrifuge has significantly changed the deposition height and upper-section slope angles compared to the benchmark experiment conducted on the ground. Numerical simulations were further performed for equivalent gravity levels of 1/6 g and 1/3 g, revealing that under the prediction of the rate-independent constitutive model used, the final collapse morphologies are independent of gravity levels, and the influence of the centrifuge gravity field is also unrelated to the gravity level magnitude.

Exposure to high-altitude conditions during flight or other similar activities has a wide-ranging impact on visual function, which is crucial not just for flight safety but for any altitude-related activity. We aimed to look at the impact of high altitude on the intraocular pressure (IOP) of helicopter pilots. The flight took off from the airstrip at 5,525 feet and flew for an hour every day for 10 days at 8,000 feet. above mean sea level. Flights were undertaken at an altitude of 12,000 feet above mean sea level over the next 10 days. During these days, pilots had no other flights. Each pilot’s one eye was measured with a Tonopen (Reichert Tono-Pen AVIA) after five topical anesthetic drops prior to flight. The arithmetic mean of five measurements was determined and recorded as a value. The pre- and post-flight data for each subgroup were analyzed using the paired sample T-test in SPSS version 20 software. For the flights at an altitude of 8,000 feet, no group showed a significant change in IOP. For the flights at an altitude of 12,000 feet, both groups showed statistically significant changes in IOP. IOP decrease may contribute to an increased risk of safety events following prolonged flights at high altitudes in helicopter pilots.

Fluidic shaping of optical polymer liquids represents an innovative fabrication methodology for optical lens production, enabling rapid in-situ manufacturing of large-aperture space telescope primary mirrors. Ground-based simulation of microgravity conditions for this process can be achieved through density-matching immersion liquids. Current terrestrial fluidic shaping experiments confront significant challenges stemming from density variations during optical polymer material curing. Our study introduces a novel surface profile control technique for optical lens fabrication during density-matched fluidic solidification processes. Through precise regulation of pressure differentials across optical polymer liquid interfaces, the research resolves variable density-matching challenges inherent in polymeric optical materials and achieves convective fluid surface morphology control. A theoretical analysis model correlating surface deformation with applied pressure gradients was established, with experimental validation through comprehensive testing and computational simulations.