Microgravity Science and Technology

Smirnov, Nickolay; Skryleva, Evgeniya; Paremskaya, Lusine; Paremski, Mikhail; Manakhova, Anastasia; Mikhalchenko, Elena; Wang, Fang

doi: 10.1007/s12217-026-10250-7pmid: N/A

The article considers an experimental and numerical study of multiphase flows in a Hele-Shaw cell. The horizontal Hele-Shaw cell makes it possible to simulate flows in porous media in microgravity. The results of numerical simulation of a three-phase flow are presented. The cases when the boundaries between the phases are stable and the cases when the Saffman-Taylor instability develops at the boundary are considered. The results of the numerical simulation are compared with the conducted experiments. The paper also examines the pressure distribution in the Hele-Shaw cell during a three-phase flow.

Nakajima, Shusaku; Genkawa, Takuma

doi: 10.1007/s12217-026-10259-ypmid: N/A

To examine growth patterns of a leafy vegetable under simulated microgravity, spinach seedlings were cultivated under clinorotation at 2 rpm in darkness for 5 d and compared with control seedlings grown under normal gravity. No significant differences were detected in root length and water content between the two growth conditions. However, interestingly, seedlings under clinorotation showed straight elongation, whereas curvature and waving appeared in control roots. Consequently, roots under clinorotation had significantly higher straightness, calculated as the straight line between the root base and tip divided by the actual root length. As the phytohormone auxin is involved in root bending, spinach seedlings were further cultivated in the presence of auxin inhibitors. Under inhibitor treatment, no significant difference in root straightness was observed between clinorotation and control, and the values were comparable to those of seedlings under clinorotation without an auxin inhibitor. These findings suggest that auxin contributes to the curvature of the control seedlings and clinorotation compensates for this. Therefore, spinach seedlings at the early developmental stage exhibited a unique growth pattern under clinorotation, unlike most other plant species.

Yokota, Chihiro; Kumano, Souta; Tsumura, Seiichi; Kameyama, Kanji; Maki, Syou; Tadokoro, Ryosuke; Yamamoto, Toshimasa

doi: 10.1007/s12217-026-10262-3pmid: N/A

We carried out an in situ observation of the feeding process of edible shrimp in a microgravity environment. To realize that condition, we developed a new type of clinostat with high-speed rotation, with a maximum rotation of 130 rpm. Under that rotation speed, aquatic organisms such as fish and crustaceans have a suppressed capability of recovering their proper swimming form, making it possible for them to be exposed to a pseudo-weightless condition. This method allowed us to successfully observe the feeding process of shrimp in that condition. As a supporting experiment, we conducted similar experiments using larval Artemia crustaceans, i.e. brine shrimp, and we confirmed that they, too, can exhibit feeding behavior under a weightless environment, even when exposed for the long period of four days. According to a gene ontology analysis of shrimp exposed to microgravity for 24 h, a significant difference was detected in the exposed shrimp as compared with control shrimp at 1 G. Those results suggested that exposure to weightlessness may have a biological impact on the shrimp, although the details are unknown yet. We believe that the high-speed clinostat will contribute greatly to the future progress of engineering applications in microgravity research.

Xiao, Tinglan; Yang, Qi; Li, Deyou; Fu, Xiaolong; Liu, Jintao

doi: 10.1007/s12217-026-10256-1pmid: N/A

With its core advantage of greatly improving the structural efficiency of propellant tanks, the common bulkhead structure has become a key development direction for high-performance satellite surface tension propellant tanks. However, previous studies on vane structural parameters have ignored the influence of microgravity acceleration magnitude on flow mechanism and parameter design, leading to a lack of targeted design criteria for surface tension tanks. This study employs numerical simulation methods and monitoring indicators, such as the leading-edge height and transferred volume of the propellant, to explore the effects of the vane thickness, gap distance, and propellant fill ratio on the gas–liquid management performance of common bulkhead tanks. This study reveals the transition of the dominant force balance of capillary-induced motion under microgravity: under 10− 3 g microgravity, the flow is co-dominated by surface tension, inertial force, viscous force and non-negligible acceleration force; under 10− 5 g microgravity, the flow is completely dominated by the balance between surface tension and viscous force. The results demonstrate that increasing the vane thickness significantly enhances management performance while the optimal gap distance is acceleration-dependent. This study offers guidance for designing new-generation common-bulkhead surface tension tanks.

Mousavi, Fateme

doi: 10.1007/s12217-026-10242-7pmid: N/A

The ability of plants to adapt and grow in extraterrestrial environments is a crucial prerequisite for human spatial colonization of extraterrestrial environments. Sounding rockets allow biological payloads to experience real microgravity conditions for several minutes before returning to Earth. The present systematic review sought to gain new insights to guide the design of plant experiments for sounding rocket platforms. Most of the plant studies using sounding rocket technology have been conducted by Germany (Ten out of twelve launches). In the launches conducted, the minimum apogee was 86 km, and the maximum was 800 km for the Virgin Galactic Unity 22 and MAXUS, respectively. The microgravity quality was in the range of 10− 4 g to 10− 6 g. The plant payloads selected for the launches ranged from plant cells to young seedlings. Four (4) out of 10 studies deploy hardware capable of automatically fixing the plant material in different gravitational phases. All ten studies included 1 g ground controls in parallel with the flown samples. Two of the ten studies utilized another real microgravity platform in addition to 1 g ground controls, conducted in parallel with the sounding rocket flight. The biological responses to sounding rocket flight have been investigated at cellular, molecular, histological, and physiological levels. Sounding rockets and suborbital spacecraft, even though they have some limitations, can still be good options for plant biology researchers. They offer a way to do repeated observations and experiments in real microgravity conditions.

Mahajan, Amit; Dagar, Sonali

doi: 10.1007/s12217-026-10252-5pmid: N/A

This study examines thermally induced convective flow in a fluid-saturated porous medium, where momentum transport follows extended Darcy’s law and thermal transport is governed by the Cattaneo–Christov–Jordan–Mariano (CCJM) model, allowing for variations in the gravitational field. The CCJM framework generalizes the classical Fourier heat conduction model to include thermal diffusion, finite thermal relaxation, and inertial effects, while the momentum equation accounts for the presence of a spatially varying gravitational field. Collectively, these effects provide a more physically consistent depiction of heat transport and convective behavior in porous media. The onset of convection is examined through a combined linear analysis, encompassing stationary and oscillatory modes, together with a nonlinear stability framework. Linear stability is evaluated using the normal-mode technique, while the nonlinear stability equations are obtained through the energy method. Numerical simulations are performed using MATLAB to determine the critical stability parameters, and the corresponding plots depict the resulting stability characteristics. The Galerkin single-term approach is used to measure the critical Rayleigh number and the corresponding wavenumber. Four distinct gravity-variation profiles are examined, revealing that the gravity-modulation parameter \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\gamma $$\end{document} may exert either a stabilizing or destabilizing influence depending on the specific profile considered. The numerical illustrations further highlight the roles of the parameters \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\zeta $$\end{document}, \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$Sg$$\end{document}, and \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$Va$$\end{document} in shaping the overall stability behavior of the system. Collectively, these results highlight the joint influence of gravity modulation and material parameters on the initiation of convection, offering enhanced insight into the thermal stability of viscoelastic porous media within the Cattaneo–Christov–Jordan–Mariano (CCJM) framework.

Nguyen, Vinh T.; Ho, Nang X.; Nguyen, Vinh D.; Nguyen, Kien T.; Vu, Truong V.

doi: 10.1007/s12217-026-10260-5pmid: N/A

While the thermocapillary migration of single and compound droplets has been extensively studied in unbounded media, the synchronized transport and interaction dynamics of multiple compound droplets within confined geometries remain poorly understood. This study addresses this gap by numerically investigating the thermocapillary migration of two axially aligned compound droplets inside a microchannel featuring a localized geometric constriction. Using the front-tracking method, we aim to delineate the transition between interacting and non-interacting regimes, a distinction critical for the precise control of multi-phase flows in microfluidic systems. The coupled thermal and hydrodynamic behaviors are systematically analyzed as a function of the Marangoni number (Ma), the axial positioning of the leading droplet, the inner-to-outer droplet size ratio (Rio), and the relative constriction depth (d/Rc). Our results reveal that inter-droplet interaction is primarily triggered when the trailing droplet catches up to the leading one near the constriction, where local velocity reaches its minimum. We identify Ma as a dominant control parameter; higher Ma values intensify thermal convection, which disrupts the local temperature field and delays the onset of interaction by reducing the trailing droplet’s velocity. Crucially, we find that geometric and internal configurations dictate the interaction mode: shallow constrictions (d/Rc < 0.58) or larger inner cores (Rio ≥ 0.7) promote independent passage by enabling droplet elongation or rapid escape. In contrast, deeper constrictions and smaller inner cores reduce interfacial deformation, thereby facilitating closer proximity and significant multi-body interaction. The study culminates in the establishment of a comprehensive phase diagram based on H0L/Ro, Rio, and Ma. This diagram serves as a predictive tool to define the boundaries between interacting (ID* = 0) and non-interacting (ID* > 0) regimes. By providing a mechanistic understanding of how geometry and thermal forces can be leveraged to synchronize or separate double emulsions, this work offers a framework for the optimized design of microfluidic devices for targeted drug delivery and advanced material synthesis.

K. Alhamli, Mohammad; Alhendal, Yousuf; Al-Sairfi, Hussain

doi: 10.1007/s12217-026-10253-4pmid: N/A

We numerically investigate the motion of a Fluorinert FC-75 droplet suspended in silicone oil in a cylindrical container under a vertical temperature difference. The top and bottom walls are maintained at 343 and 283 K, the sidewall is adiabatic, and the droplet is initially placed at mid-height. Ansys Fluent with the Volume of Fluid method is used to solve the coupled momentum and energy equations. Container heights from 2.5 to 60 mm are examined, with droplet diameter scaled with container size, under zero gravity, normal gravity, and combined thermocapillary-buoyancy forcing. In zero gravity, the droplet migrates toward the hot upper wall, but its mean migration speed decreases as container height increases because the axial temperature gradient weakens and confinement distorts the isotherms. Under normal gravity, the denser FC-75 droplet settles toward the cold wall. Under combined forcing, containers with heights of 3 mm or less exhibit near cancellation between buoyancy and thermocapillary, whereas for heights of 15 mm or more the motion approaches the gravity dominated limit. At a fixed height of 2.75 mm, varying droplet diameter reverses the net drift. This transition is captured by a Marangoni-buoyancy balance criterion, which predicts a critical diameter of about 0.203 mm for quasi-equilibrium. Three-dimensional simulations show deformation only in the buoyancy dominated regime. These results identify confined configurations that approximate microgravity behavior and provide a practical criterion for droplet positioning and transport.

Rachitha, C. S.; Nanjundappa, C. E.; Shivakumara, I. S.

doi: 10.1007/s12217-026-10255-2pmid: N/A

Bolshova, Tatyana; Shvartsberg, Vladimir

doi: 10.1007/s12217-026-10258-zpmid: N/A

Present work involves numerical CFD study of the flame structure of PMMA sphere at different velocities of the incident oxidizer flow under zero-gravity conditions. The performed modeling allowed us to establish the chemical processes to change significantly with a variation of velocity of the oxidizer flow. It was shown that both the thermal and chemical structure of the flame change, as well as the temperature gradient and the mechanism of heat release in the gas phase. It has been established that with an increase in the flow velocity, the combustion completeness decreases that is explained by an increase in the flame strain rate and, consequently, a decrease in the residence time in the chemical reaction zone. Calculation of the heat release rates in individual reactions at various oxidizer flow velocities allowed us to identify four key reactions determining the overall heat release rate. At average flow velocity values, the main contribution to the heat release is made by the HO2 + OH = H2O +O2 step, which is explained by a high concentration of HO2 in the flame. The remaining key steps in decreasing order of their contribution to the heat release are T-C3H5 + O2 = CH3 + CO + CH2O, HCO + O2 = CO + HO2 and CH3 + O = H + H2 + CO.