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Based on a satellite constellation composed of two GRACE-type satellite formations with different inclinations (near polar orbit + low inclination) and the theory of repeat orbit cycle, we discuss the methods for selecting medium-low inclinations for global and local gravity fields. The effects of this constellation configuration on gravity field inversion are comparatively analyzed using a whole-course dynamics simulation. The results show that compared with the single GRACE-type satellite formation, the use of satellite constellations with different inclination configurations improves the gravity solution precision by 34%. The inclusion of multi-directional observations can improve the spatio-temporal resolution of the satellite missions, and yield gravity field solutions with higher isotropic sensitivity. Furthermore, it is necessary to select the optimal low inclination according to the study area, which will have a significant influence on the gravity field solution.

Gravity Recovery and Climate Experiment (GRACE) gravimeter satellites observed the Earth gravity field with unprecedented accuracy since 2002. After the termination of GRACE mission, GRACE Follow-on (GFO) satellites successively observe global gravity field, but there is missing period between GRACE and GFO about one year. Many previous studies estimated terrestrial water storage (TWS) changes using hydrological models, vertical displacements from global navigation satellite system observations, altimetry, and satellite laser ranging for a continuity of GRACE and GFO data. Recently, in order to predict TWS changes, various machine learning methods are developed such as artificial neural network and multi-linear regression. Previous studies used hydrological and climate data simultaneously as input data of the learning process. Further, they excluded linear trends in input data and GRACE/GFO data because the trend components obtained from GRACE/GFO data were assumed to be the same for other periods. However, hydrological models include high uncertainties, and observational period of GRACE/GFO is not long enough to estimate reliable TWS trends. In this study, we used convolutional neural networks (CNN) method incorporating only climate data set (temperature, evaporation, and precipitation) to predict TWS variations in the missing period of GRACE/GFO. We also make CNN model learn the linear trend of GRACE/GFO data. In most river basins considered in this study, our CNN model successfully predicts seasonal and long-term variations of TWS change.

Satellite missions providing data for a continuous monitoring of the Earth gravity field and its changes are fundamental to study climate changes, hydrology, sea level changes, and solid Earth phenomena. GRACE-FO (Gravity Recovery and Climate Experiment Follow-On) mission was launched in 2018 and NGGM (Next Generation Gravity Mission) studies are ongoing for the long-term monitoring of the time-variable gravity field. In recent years, an innovative mission concept for gravity measurements has also emerged, exploiting a spaceborne gravity gradio-meter based on cold atom interferometers. In particular, a team of researchers from Italian universities and research institutions has proposed a mission concept called MOCASS (Mass Observation with Cold Atom Sensors in Space) and conducted the study to investigate the performance of a cold atom gradiometer on board a low Earth orbiter and its impact on the modeling of different geophysical phenomena. This paper presents the analysis of the gravity gradient data attainable by such a mission. Firstly, the mathematical model for the MOCASS data processing will be described. Then numerical simulations will be presented, considering different satellite orbital altitudes, pointing modes and instrument configurations (single-arm and double-arm); overall, data were simulated for twenty different observation scenarios. Finally, the simulation results will be illustrated, showing the applicability of the proposed concept and the improvement in modeling the static gravity field with respect to GOCE (Gravity Field and Steady-State Ocean Circulation Explorer).

Discussing the problem of the external gravitational potential of the rotating Earth, we have to consider the fundamental postulate of the finite speed of the propagation of gravitation. This can be done using the expressions for the gravitational aberration compared to the Liénard–Wiechert solution of the retarded potentials. The term gravitational counter-aberration or co-aberration is introduced to describe the pattern of the propagation of the gravitational signal emitted by the rotating Earth. It is proved that in the first approximation, the classic theory of the aberration of light can be applied to calculate this effect. Some effects of the gravitational aberration on the external gravity field of the rotating Earth may influence the orbit determination of the Earth artificial satellites.

West Papua province has a geothermal resource that can be established as renewable electricity energy or tourism. One of the locations for geothermal prospects is in the Momiwaren district of South Manokwari regency. A preliminary study in form of a qualitative interpretation has been conducted through the analysis of high-resolution of earth gravity fields from the Global Gravity Map developed by Curtin University, Australia. This research was performed to increase the boundary of the geological structure which indicates the existence of a source of manifestation of hotsprings and the fault structures that control it. The study begins with the reduction of the gravity field data to obtain a complete Bouguer anomaly based on the SRTM2gravity terrain model correction. Furthermore, regional and residual gravity anomalies are separated, and vertical and horizontal gravitational gradient analysis using 2-D fast Fourier transform. Qualitative interpretation produces models and boundaries of the main structure and the corresponding Demini and Gaya Baru faults and the distribution of the geological rock formations in the study area. This interpretation provides useful information as a constraint for quantitative interpretation through subsurface inversion modeling to obtain detailed geothermal models in Momiwaren.

Solder joints formed in microgravity are inferior to joints formed in Earth gravity. They are mechanically weaker and less electrically conductive due to voids forming in the joints when soldering in microgravity. Surface tension and lack of gravitational buoyancy combine to prevent flux and water vapors from escaping the molten solder in absence of gravity, resulting in more porous solder joints. Additionally, corrosive flux vapor products remain trapped in the voids causing further deterioration. Parabolic aircraft flight microgravity soldering data are presented, to compare the joint porosities of conventional nonmagnetic solders and new magnetic solders, to determine if the magnetic solder, when soldered in the presence of a magnetic field, would reduce porosity of solder joints formed in microgravity. Soldering irons were used to hand-solder resistor leads into PC board though-holes, for nonmagnetic and magnetic solders. Addition of 4 wt% and 6 wt% of iron microparticles to the solder pastes resulted in 24% and 28% reductions in the solder joint average cross-sectional porosity, respectively, relative to average nonmagnetic solder joint porosity. Joint porosity distributions were log-normal, so the Wilcoxon Rank Sum test for statistical significance was used to show these porosity reductions are statistically significant at α = 0.05. A fully-developed wire magnetic solder could enable in-space repair of electronics at the component level, giving space mission planners additional flexibility to eliminate some or all spare board-level electronics, and plan instead to perform electronics repairs at the component level. This could then reduce or eliminate required mass of these spare electronics boards.

The paper is devoted to numerical simulation of nonlinear regimes of a binary liquid mixture in rectangular cavities elongated in the horizontal direction. The boundaries of the cavity are considered to be rigid, impermeable to the substance. The vertical boundaries are thermally insulated; constant different temperatures corresponding to heating from below are maintained on the horizontal boundaries. The calculations are carried out in the framework of a non-stationary approach, using the Boussinesq approximation. An aqueous NaCl solution was chosen as the studied mixture. The calculations were carried out for cases of Earth and reduced gravity. The local and integral characteristics of nonlinear regimes are obtained, the structure of the arising flow and the concentration distribution are found. An analysis of the data shows that in the case of terrestrial gravity in a square cavity, the regime of stationary oscillations with the reconnection of vortices is realized. A multi-vortex flow occurs and its intensity oscillates in an irregular manner in a rectangular cavity under Earth gravity. A stationary flow is observed when gravity is reduced: a single-vortex and a multi-vortex occur for a square and a rectangular cavity, respectively. When an intensity of convective flow is low, a process of mixture separation close to purely diffusive is observed at the initial stage of convection development. It was found that a sharp increase in the intensity of motion at the initial stage of convection development affects the separation of the mixture, it becomes much stronger. The resulting flow mixes the mixture quite strongly: it remains homogeneous in the central part of the cavity, strong changes in concentration are observed near the boundaries. In the case of Earth gravity, the concentration gradients near the upper and lower boundaries are not equal; in the case of reduced gravity, they are the equal.

Recently developed granular scaling laws create new opportunities to evaluate particle dynamics between environment and wheel shapes. We investigate the performance of straight grousered (i.e. protrusions added to the wheel rim to better engage the soil) wheels and helical grousered wheels in both silica sand and crushed basalt lunar simulant. Mechanical power draw and velocity of the wheels are compared in both materials for performance assessment. The scaling laws are evaluated for Earth gravity experimentally and reduced gravity through coupled multi-body dynamic and discrete element method (MBD-DEM) simulations. Experimental results show general power prediction error between 20 and 35% for crushed basalt and 15–25% error for silica sand. Velocity prediction error showed high dependence on material, with silica sand error generally between 4 and 10% and crushed basalt varied between 0 and 27%. Simulation results match theoretical predictions more closely with power error under 8% and velocity error under 4% for most speeds. The experimental error was further investigated and shows a new scaling dependency on sinkage (depth which the wheel rim sinks below the terrain surface) thresholds.

The regions around the world need to perform their results based on the local geoid. However, each region has different ground topography based on the amount of gravity in this region. Nowadays, the recent global Earth's gravity model of 2008 is successfully used for different purposes in geosciences research. This research presents an overview of the preliminary evaluation results of the new Earth Gravitation Model (EGM08) in the middle of Iraq. For completeness, the evaluation tests were also performed for EGM96 by examining 31 stations distributed over four Iraqi provinces. The national orthometric heights were compared with the GPS /leveling data obtained from these stations. This study illustrated that the GPS /leveling based on EGM08 data was better than that based on EGM96 data in terms of reducing the root mean square error (RMSE) of the differences between the orthometric heights and GPS/leveling data. The standard deviation (SD) values for the national orthometric heights and GPS heights were about 4 and 26cm, respectively. The results also show that there is a small difference in hight ranged (0.0013 - 0.1333 m) in Karbala, (0.0023 – 0.0062 m), in Najaf and (0.0173 – 0.0703 m), in Babylon. Due to the flat area, better results were obtained in Karbala and Najaf than Babylon. The EGM08 geoid method has shown to yield very close results to reality for various projects, thus its accuracy is acceptable.

To address the accuracy requirements of initial alignment of high-precision inertial navigation systems (INSs), gravity disturbance compensation for INSs based on a spherical harmonic model is investigated herein. First, the horizontal component of gravity disturbance at an alignment point is calculated using the high-resolution Earth Gravity Model EIGEN-6C4 and then compensated to the initial alignment. Subsequently, the self-alignment algorithm of solidified coordinate frame is used to derive the misalignment angle equation of gravity disturbance affecting the initial alignment. Meanwhile, the coupling relationship between the measurement error of an inertial unit and the gravity disturbance is simulated and analyzed. Finally, a laser strapdown inertial navigation system experiment is performed. The simulation result shows that the pitch angle, roll angle, and heading angle errors reduced by $27.41^{\prime \prime }$ , $- 0.37^{\prime \prime }$ , and $6.72^{\prime \prime }$ , respectively, after the gravity disturbance compensation. Experiment result shows that the alignment performance after compensation has been improved and the heading angle error is reduced by $6.76^{\prime \prime }$ . The simulations and experiments results validate the theoretical analysis.

Accepted: 2019-10-05, 資料番号: SA1190180000

The stability of a conductive state of a system of two horizontal layers of immiscible fluids of close densities with a fixed heat flux at external boundaries is studied. The problem is solved in the framework of the generalized Boussinesq approximation, which correctly takes into account the deformations of the interface. The onset of convection at heating from above or below is investigated. Main attention is paid to the effect of layer thickness ratio and gravity level on instability. Two long-wave instability modes related the presence of a deformable interface and to a fixed heat flux at the external boundaries are found out. They are analyzed analytically. The behavior of the system with respect to monotonic and oscillatory perturbations of finite wavelength is studied numerically. The complete stability map is obtained. It is found that for very different layer thicknesses, as well as for single layers with fixed heat flux at the boundaries, a long-wavelength instability is observed. The presence of a long-wave instability domain at close thicknesses of layers is also found, which is associated with a strong stabilization of finite-wavelength instability in this parameter range. In the case of Earth gravity, the monotonic perturbations are most dangerous at any ratios of layer thicknesses, the oscillatory mode of instability is responsible for the onset of convection only in microgravity conditions.

In the paper, an attempt has been made to describe seismic processes by means of classical mechanics. Dynamic parameters such as energy, impulse, and forces that determine the movement of masses are estimated. An earthquake model is regarded with consideration of the Earth gravity field influence on distribution of masses composing the Earth crust. The Earth crust is considered as a complex of geological bodies which is ordered by the planets gravity field. Due to isostasy the difference in density of the equal matter volumes leads to formation of mountain structures specific for the surface. When a base of such structures collapses a rock block shifts down and acquires mechanical impulse. Authors assume that this acquired mechanical impulse determines the earthquake’s magnitude. Impulse propagates in medium as a seismic wave. Front of the wave generates pressure effected on an environment that is not active yet. It determines macro-processes of the earthquake measured as earthquake intensity. Authors consider mass (weight) of a rocks block, magnitude (mechanical impulse acquired during an impact), seismic emission, which is a distribution of a momentum and a pressure of wave front (product of impulse by time), as parameters of a seismic process. To estimate dynamic parameters of earthquake processes, such as shifted mass, mechanical impulse, pressure of wave front, a nomogram is presented. Magnitude of a seismic event has dimension of a mechanical impulse, seismic intensity (earthquake intensity) has a dimension of pressure. Nomogram consists of several parts. The first one, allows analyzing the source of the emission. It shows the relation between emitted momentum, mass of a shifted body and energy. The next part of the nomogram represents momentum density per unit of area of the wavefront, which decreases in proportion to the square of a distance from the source. It characterizes the spherical propagation of seismic radiation in an isotropic medium. The third part of the nomogram helps to estimate the value of an average seismic pressure of the wavefront. The last part of the nomogram allows rating the empirical characteristics of a seismic event. A relation between a scale of seismic pressure and standardized scale of seismic intensity MSK-64 is established. As an example a Spitaka earthquake, December 7 th , 1988, was analyzed.

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), launched May 22, 2018 and collecting science data since June 2018, is extending the 15-year data record of Earth mass change established by its predecessor GRACE mission (2002-2017). The GRACE-FO satellites carry onboard a novel technology demonstration instrument for intersatellite ranging, the Laser Ranging Interferometer (LRI), in addition to the microwave interferometer (MWI) carried on GRACE. The LRI has out-performed its in-orbit performance requirements both in terms of accuracy as well as the duration of tracking. Here, we compare and validate LRI-based gravity solutions for January 2019 to September 2020 against the MWI solutions. The comparison between the two sets of gravity solutions shows great similarities in general and nearly perfect consistency at a large hydrologic basin spatial scale (100,000 km

The problem of particle motion around a particle in a shear flow is considered by numerically for conditions of weightlessness and normal earth gravity. n. The minimum distance between liquid small drops and a streamlined drop is shown.

7 p.-1 fig., Plants are a necessary component of any system of bioregenerative life-support for human space exploration. For this purpose, plants must be capable of surviving and adapting to gravity levels different from the Earth gravity, namely microgravity, as it exists on board of spacecrafts orbiting the Earth, and partial-g, as it exists on the surface of the Moon or Mars. Gravity is a fundamental environmental factor for driving plant growth and development through gravitropism. Exposure to real or simulated microgravity produces a stress response in plants, which show cellular alterations and gene expression reprogramming. Partial-g studies have been performed in the ISS using centrifuges and in ground based facilities, by implementing adaptations in them. Seedlings and cell cultures were used in these studies. The Mars gravity level is capable of stimulating the gravitropic response of the roots and preserving the auxin polar transport. Furthermore, whereas Moon gravity produces alterations comparable, or even stronger than microgravity, the intensity of the alterations found at Mars gravity was milder. An adaptive response has been found in these experiments, showing upregulation of WRKY transcription factors involved in acclimation. This knowledge must be improved by incorporating plants to the coming projects of Moon exploration., Work performed in the authors’ laboratory was supported by different grants of the Spanish National Agency for Research of the Spanish Government, e.g., Grants #ESP2015-64323-R and #RTI2018-099309-B-I00 (co-funded by EU-ERDF).

We present a construction of the optical whispering gallery mode (WGM) resonator gravimeter. The sensitive element of the device is a resonator, placed on a cantilever, which moves with the change of gravity, variating the distance with coupling element. The gravity acceleration is measured by the change of the resonator eigenmode parameters.

—The empirical results on estimating the resolution and high-frequency noise in the Earth’s gravity models are presented. The Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences participated in a marine gravity survey in the Indian Ocean. Based on the survey data, gravity maps were constructed for ten regions with a total of 611 986 gravimetric points. The root mean square measurement error is at most 0.27 mGal. The differences between measured gravity and predictions by the EGM2008 gravity model are calculated. The statistical processing of the differences shows that they vary from –25 to 44 mGal on the shelf and from –7.4 to 6.2 mGal on the abyssal plain with a root mean square value of 1.33 mGal. The results of the survey indicate that the anomalies in the ultra-high-degree model can only be used for constructing gravity maps on the scale of 1 : 500 000 or smaller.

Both GRACE and GOCE have proven to be very successful missions, providing a wealth of data which are exploited for geophysical studies such as climate changes, hydrology, sea level changes, solid Earth phenomena, with benefits for society and the whole world population. It is indispensable to continue monitoring gravity and its changes from space, so much so that a GRACE follow-on mission has been launched in 2018. In this paper, a new satellite mission concept named MOCASS is presented, which can be considered as a GOCE follow-on, based on an innovative gradiometer exploiting ultra-cold atom technology and aimed at monitoring Earth mass distribution and its variations in time. The technical aspects regarding the payload will be described, illustrating the measurement principle and the technological characteristics of a cold atom interferometer that can measure gravity gradients. The results of numerical simulations will be presented for a one-arm and a two-arm gradiometer and for different orbit configurations, showing that an improvement with respect to GOCE could be obtained in the estimate of the static gravity field over all the harmonic spectrum (with an expected error of the order of 1 mGal at degree 300 for a 5-year mission) and that estimates are promising also for the time-variable gravity field (although GRACE is still performing better at very low degrees). Finally, the progress achievable by exploiting MOCASS observations for the detection and monitoring of geophysical phenomena will be discussed: the results of simulations of key geophysical themes (such as mass changes due to hydrology, glaciers and tectonic effects) with expected gravity change-rates, time constants and corresponding wavelengths, show that an improvement is attainable and that signals invisible to past satellites could be detected by exploiting the cold atom technology.

Growing plants under microgravity conditions in a space ship is essential for future long-term missions to supply needs for food and oxygen. Although plant growth modules for microgravity have been developed and tested for more than 40 years, creating optimal saturation conditions for plant growth in the absence of gravity still remains a challenge. In this study, we present results from a series of spontaneous imbibition experiments designed to approximate microgravity conditions by using density-matched fluid pairs. Porous media with patterned wettability characteristics are used to manipulate macroscopic fluid saturation and microscopic fluid interfacial configurations. These are compared to an additional experiment under Earth gravity, wherein we observe spontaneous imbibition of water into common potting soil. Patterning grains of different wettabilities under microgravity conditions proves to be an effective method to manipulate spatial distributions and saturations of fluids. These wettability patterns can be optimised to fine-tune residual fluid characteristics, e.g. non-wetting phase saturation, connectivity and interfacial area. Furthermore, we present tomographic evidence supporting previous work which was suggesting enhanced snap-off and disconnection of the gas phase in porous media under microgravity.

CHF is an important design parameter in two-phase thermal management systems utilizing flow boiling schemes. In this study, a new theoretical model for predicting the trigger mechanism for flow boiling CHF is presented. Flow visualization shows that flow boiling on a heated wall is sustained mostly by the region containing discrete vapor bubbles called the wetting front because it allows the heated wall continuous access to the bulk liquid. CHF is triggered when intense evaporation of the liquid in the wetting front causes combined effects of parallel-to-flow direction interfacial stability and perpendicular-to-wall direction Helmholtz instability generating a continuous vapor patch on the wetting front. The new mechanistic CHF model incorporates three sub-models: a separated flow model to calculate two-phase flow parameters, an interfacial instability model to calculate the critical wavelength of parallel-to-flow vapor wave, and a Helmholtz instability model to calculate the critical wavelength of perpendicular-to-wall liquid-vapor interface. The CHF model is used to predict experimental data for a rectangular channel with single-sided heating in Earth gravity and microgravity for a variety of operating conditions. The model predictions show good agreement with experimental data, evidenced by an MAE of 15.36%.

The Origins, Spectral Interpretation, Resource Identification, and Security Regolith Explorer(OSIRISREx) mission observed the The Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer (OSIRIS‐REx) mission observed the Moon during the spacecraft's Earth gravity assist in 2017. From the spacecraft view, the lunar phase was 42°, and the in‐view hemisphere was dominated by anorthositic highlands terrain. Lunar spectra obtained by the OSIRIS‐REx Visible and InfraRed Spectrometer show evidence of several candidate absorption features. We observe the 2.8‐μm hydration band, confirming the spectral results from other missions, but detected in full‐disk spectra. We also tentatively identify weak spectral features near 0.9 and 1.3 μm, consistent with lunar regolith containing a mixture of plagioclase and orthopyroxene minerals, as expected for highlands terrain.

Based on a modified force balance model, new correlations were proposed for the prediction of vapor bubble departure radius in saturated and subcooled pool boiling under atmospheric pressure. To predict the departure radius, the wall temperature and contact angle are two important input parameters. Instead of the static contact angle, the present correlations use the dynamic advancing contact angle at root of the bubble base at the moment before bubble detachment (i.e., the maximum dynamic advancing contact angle) to calculate the bubble departure radius. The results show that for the bubble departure radius obtained in this study, the developed correlation can predict all the data points within a maximum error of 3.8% in both normal earth gravity and 0.01ge reduced gravity. Moreover, for data sets in the literature including 1g saturated boiling, 1g subcooled boiling, saturated boiling in reduced gravity, and subcooled boiling in reduced gravity, it is also demonstrated that compared with the thirteen existing correlations, the proposed correlations exhibit a big improvement in predicting bubble departure radius.

In the attitude and heading reference system (AHRS), the output noise of MEMS gyroscope is too large, zero drift can not be eliminated completely, and the output of angular rate is easy to be interfered, which leads to low accuracy and large accumulated error of attitude quaternion and so on. In this paper, an adaptive extended Kalman filter algorithm is proposed based on the information of geophysical field (earth gravity field and geomagnetic field) to continuously and adaptively correct the accumulated error of MEMS gyroscope in attitude calculation. The experimental results via ROS robot platform show that the proposed algorithm can effectively solve the problem of large accumulated error in the process of attitude quaternion solution, and improve the accuracy of attitude calculation, thus the effectiveness of the proposed algorithm is verified.

This is an experimental study on highly subcooled flow boiling of water for assessing the effect of gravitational acceleration on flow boiling heat transfer. The experiments are conducted in a macro-channel 3 mm high, 40 mm wide and 120 mm long at water mass fluxes of 330, 630 and 830 kg/m2 s and heat fluxes in the range 200–900 kW/m2. Increased gravitational accelerations, from 1.8 to 9 times the Earth-gravity are achieved with the use of a ∼3 m radius centrifuge (Large Diameter Centrifuge, ESTEC/European Space Agency). Two distinct channel inclinations are examined; horizontal, where the gravitational acceleration is normal to the boiling surface, and vertical, where the gravitational acceleration is parallel to the boiling surface and opposite to flow direction. Experiments at hyper-gravity conditions show that for the horizontal channel inclination, flow boiling heat transfer coefficient increases, whereas for the vertical channel inclination it decreases. The observed deviations lie approximately between +15% and −40% from the Earth-g value. An interpretation of the present results is attempted based on the effect of liquid-phase natural and forced convection combined with the effect of buoyancy at vapor bubbles. The tendency of the heat transfer coefficient experimental data with respect to changes in gravitational acceleration allows the development of a gravity-modified version of the well-known two phase model of Liu-Winterton, by incorporating a linearly dependent gravity multiplier.

A method by which to incorporate the Electric Delta-V Earth Gravity Assist (EDVEGA) scheme into a patched three-body approach to design an interplanetary transfer trajectory is presented in this paper. The EDVEGA scheme is a promising technique to reduce fuel consumption using Earth gravity assist and electric propulsion. In a patched three-body approach, the dimension of the problem that connects some trajectories is reduced by the use of special attainable sets. However, because of the singularity associated with Earth's center, it is difficult to connect an EDVEGA trajectory with a trajectory designed in the three-body problem. Therefore, this paper proposes a design method for an Earth–Mars transfer trajectory that combines the EDVEGA scheme with a patched three-body approach using Levi-Civita regularization and a special contour plot. Through comparison with conventional invariant manifold techniques, we demonstrate that fuel consumption is reduced by the proposed method.

Global monitoring of time-variable Earth gravity field from space – at first, observation of secular changes in the Earth flattening by SLR satellites and in recent years especially the regional hydrology variations revealed by the GRACE mission – has revolutionized the exploration of the Earth in many fields. To be able to obtain this rather weak part of the measured signal, it is necessary to measure/model and to subtract all other gravitational and nongravitational forces whose magnitude is not negligible compared to that of the time-variable gravity. In our paper, we analyze the influence of the perturbations arising from the general theory of relativity. Using the modelled data over one year of three example satellites at altitudes 250 km (GOCE), 450 km (Swarm A) and 5900 km (LAGEOS-1), we characterized the magnitude and frequency of occurrence of the three main general relativistic perturbing terms and compared their action to other relevant accelerations. Namely, for GOCE and Swarm A the accelerations due to time-varying gravity reach 10−9 − 10−8 m s−2, for LAGEOS-1 10−11 − 10−10 m s−2; relative to the preceding, the dominant relativistic term is greater by one order of magnitude in the radial direction, the relativistic precession terms happen to be comparable in the cross-track direction. Therefore, for a proper extraction of the time-varying part of the gravity signal, all three relativistic terms have to be taken into account. This conclusion is validated by the real monthly gravity fields obtained through the inversion of GPS orbits of the Swarm A satellite.

The geodetic and geophysical applications of Earth Gravity Field parameters computed from Global Geopotential Models (GGMs) are quite on the increase despite the inherent commission and omission errors of these models. In view of this, this study focuses on refining and quantifying terrain-induced effects on Bouguer gravity anomalies computed directly from a total of seven recent GGMs. In the study, the Residual Terrain Model (RTM) technique was used to estimate the residual terrain effects that were added to the GGM-computed Bouguer gravity anomalies at the sixty test points in Enugu State, Nigeria. The computed residual terrain effects range from -24.6 to 37.5 mgal while the percentage of the omission errors of the GGMs based on their Root-Mean-Square (RMS) differences ranges from 7.8% to 44.7%. It can be concluded that GGM-refined Bouguer gravity anomalies are better in accuracy than the unrefined GGM-computed Bouguer gravity anomalies and hence there is need for accurate height information in the development of GGMs. We, therefore, recommend that refined Bouguer gravity anomalies obtained from HUST-Grace2016s, EIGEN-6C4 and GECO that gave best improvement amongst the seven GGMs under consideration should be used to supplement the available terrestrial Bouguer anomalies for geodetic and geophysical applications within the study area.

Gravity variation effects on plants provide definite changes. Normal Earth gravity (1G) and microgravity (µg) are possible variations for experimental purposes. On-board spaceflight microgravity experiments are rare and expensive, as the microgravity environment is an outstanding platform for research, application and education. A Clinostat was used for ground-based experiments to investigate the shoot morphology of maize plants at the Space Agency of Nigeria—National Space Research and Development Agency (NASRDA). A Clinostat device uses rotation to negate gravitational pull effects on plant growth and development. Maize was selected for this experiment because of its nutritional and economic importance, and its usability on the Clinostat. Plant shoot morphology is important for gravi-responses. Shoot curvature and shoot growth rate analyses were conducted on the shoots of a provitamin variety of maize. The seeds were planted into three Petri dishes (in parallel) in a wet chamber using a plant substrate—agar-agar. The experimental conditions were subject to relative humidity, temperature and light conditions. After 3 days of germination under 1G, two of the Petri dishes were left under 1G, serving as controls for shoot curvature and shoot growth rate analyses. The clinorotated sample was mounted on the Clinostat under: a fast rotation speed of 80 rpm, a horizontal rotation position and a clockwise rotation direction. The images of the samples were taken at a 30 min interval for 4 h. After observations, the shoot morphology of the seedlings was studied using ImageJ software. The grand average shoot angles and shoot lengths of all the seedlings were calculated following the experimental period to provide the shoot curvatures and shoot growth rates, respectively. The results show that the clinorotated sample had a reduced response to gravity, with 50.77°/h for the shoot curvature, while the 90°-turned sample had 55.49°/h. The shoot growth rate for the 1G sample was 1.25 cm/h, while that for the clinorotated sample was 1.26 cm/h. The clinorotated sample had an increased growth rate per hour compared to the counterpart 1G sample. These analytical results serve as preparation for future real-space experiments on maize and could be beneficial to the agriculture sector.

In the ongoing MOCAST+ study (funded by the Italian Space Agency), the use of an enhanced cold atom interferometer is proposed for a satellite gravity mission. The instrument consists of an interferometric gravitational gradiometer with Strontium atoms, on which an optical frequency measurement is implemented by means of an ultra-stable laser, in order to also provide time measurements. The study is investigating whether this combination can give the possibility of improving the estimation of gravity models even at low harmonic degrees with inherent advantages in the modeling of mass transport and its global variations: this would represent fundamental information, e.g. in the study of variations in the hydrological cycle and relative mass exchange between atmosphere, oceans, cryosphere and solid Earth.The main lines of the MOCAST+ proposal are: two satellites on a polar orbit (reference altitude 342 km) at a distance of about 100 km with atomic samples on board interrogated by the same clock laser (noise of the local oscillator in common). The atom interferometer should allow to collect observations of differences of the gravitational potential (which will contribute to the estimate of the low frequencies of the Earth gravity field model) and of second derivatives of the gravitational potential along one or more orthogonal directions, which will be not necessarily the same for the two satellitesIn this presentation, the mathematical model for the application of the space-wise approach to the simulated data will be described, consisting in a filter - gridding - harmonic analysis scheme that is to be repeated for several Monte Carlo samples extracted for the same simulated scenario, in order to produce a sample estimate of the error covariance matrix of the harmonic coefficients.The data analysis based on the formulated mathematical model will be applied to both static and time-variable gravity field, performing simulations over a limited time span and extending the resulting accuracy to a longer period by covariance propagation, assuming to have other independent solutions with the same accuracy. In particular, the time-variable analysis will be mainly dedicated to assessing the accuracy in estimating the rate of change in geodynamic processes for which a linear variation in time can be reasonably assumed.

In this paper, we present a conceptional design framework for jumping robots for lunar exploration. A method is developed for spring placement and sizing that maximises the onboard elastic potential energy storage, which is essential for space missions. In the class of rhomboidal linkage robots, the analysis shows that torsion springs placed at the knee joints store more energy than the commonly used extension or linear compression springs for a given charging-actuator force; torsion springs store around 80% of the idealized maximum attainable elastic energy storage, compared to only 60% for an extension spring. A physical demonstrator is developed using torsion springs, and exhibits repeatable jumps with an average jump height of 1.1m under earth gravity, equivalent to 6.7m under lunar gravity. However, preliminary trials show the choice of substrate is shown to influence the jump height. This effect is predicted to be pronounced when jumping from lunar regolith.

The main purpose of this study is to compare the static and dynamic behavior of a historical single-span masonry arch bridge under different near-fault earthquakes. The historical Tokatlı Bridge, built in Karabük, is chosen for this study. To investigate the behavior of near-fault earthquakes on the historical masonry bridge, first, a finite element model is built and analyzed under various near-fault earthquakes by using ANSYS and SAP2000. To build a finite element model, 162920 nodes and 47818 elements are used in ANSYS. First, finite element analysis results are compared to each other under Earth gravity. Then, ground motions near the fault are chosen to be used in this study. These earthquakes can be listed as follows: Cape Mend (1992), Kobe (1995), Superstition Hills (1987), Northridge (1994), Imperial Valley (1979), and Chi-Chi (1999). The behavior of the single-span historical bridge is obtained under these ground motions, and the results are compared with each other using contour diagrams using ANSYS. Furthermore, at the end of these analyses, it is observed that the tensile stresses have reached the permissible masonry tensile strength, especially on the upper side of the large belt, on the upper side of the belt, and on the side of the belt, and pose a risk for damage.

In a 2-alternative forced-choice protocol, observers judged the duration of ball motions shown on an immersive virtual-reality display as approaching in the sagittal plane along parabolic trajectories compatible with Earth gravity effects. In different trials, the ball shifted along the parabolas with one of three different laws of motion: constant tangential velocity, constant vertical velocity, or gravitational acceleration. Only the latter motion was fully consistent with Newton’s laws in the Earth gravitational field, whereas the motions with constant velocity profiles obeyed the spatio-temporal constraint of parabolic paths dictated by gravity but violated the kinematic constraints. We found that the discrimination of duration was accurate and precise for all types of motions, but the discrimination for the trajectories at constant tangential velocity was slightly but significantly more precise than that for the trajectories at gravitational acceleration or constant vertical velocity. The results are compatible with a heuristic internal representation of gravity effects that can be engaged when viewing projectiles shifting along parabolic paths compatible with Earth gravity, irrespective of the specific kinematics. Opportunistic use of a moving frame attached to the target may favour visual tracking of targets with constant tangential velocity, accounting for the slightly superior duration discrimination.

A new mission called GRACE Follow-On is now flying to continue the measurements started by the GRACE mission, and to test a laser interferometry system for making more accurate measurements of the ...

High-accuracy and homogeneously distributed dense terrestrial gravity observations are essential data for detailed analysis of the Earth gravity field as well as for precise modeling of the geoid, which is a natural datum for point heights in geodetic and surveying applications. Precise modeling of the regional geoid and the related quality assessments of the terrestrial data are still substantial issues in many countries. The terrestrial gravity measurements in Turkey have been carried out by different institutions; therefore, the collected data have different qualities and standards. For this reason, detailed analysis of the archival data quality and datum consistency is required for regional geoid modeling using these data. In this article, the accuracy of a gridded gravity anomaly dataset was validated using pointwise gravity values with known accuracy in a limited area in northwest Turkey. Hence, this study aimed to test the contribution of the regridded gravity anomalies in combination with two different gravity datasets to determine a precise geoid model for the region. The assessments showed that the accuracy of the grid gravity anomaly dataset was approximately 5.0 mGal in the study area. Although the pointwise data used as control data in this study have high accuracy (similar to 3.0 mGal), they exhibit nonhomogeneous and striped distribution in the area, which is not appropriate for geoid modeling purposes. The calculations using regridded data with a combination of the two datasets resulted in a geoid model accuracy of 9.4 cm. The calculated accuracy was compared with the official Turkey Geoid model (TG) and Earth Gravitational Model 2008 (EGM2008) in its full spectrum, and the improvements were reported.

Microorganisms perform countless tasks on Earth and they are expected to be essential for human space exploration. Despite the interest in the responses of bacteria to space conditions, the findings on the effects of microgravity have been contradictory, while the effects of Martian gravity are nearly unknown. We performed the ESA BioRock experiment on the International Space Station to study microbe-mineral interactions in microgravity, simulated Mars gravity and simulated Earth gravity, as well as in ground gravity controls, with three bacterial species: Sphingomonas desiccabilis, Bacillus subtilis, and Cupriavidus metallidurans. To our knowledge, this was the first experiment to study simulated Martian gravity on bacteria using a space platform. Here, we tested the hypothesis that different gravity regimens can influence the final cell concentrations achieved after a multi-week period in space. Despite the different sedimentation rates predicted, we found no significant differences in final cell counts and optical densities between the three gravity regimens on the ISS. This suggests that possible gravity-related effects on bacterial growth were overcome by the end of the experiment. The results indicate that microbial-supported bioproduction and life support systems can be effectively performed in space (e.g., Mars), as on Earth.

We quantify GIA prediction uncertainties of 250 1D and 3D glacial isostatic adjustment (GIA) models through comparisons with deglacial relative sea‐level (RSL) data from North America and rate of vertical land motion ( urn:x-wiley:00948276:media:grl60497:grl60497-math-0001) and gravity rate of change ( urn:x-wiley:00948276:media:grl60497:grl60497-math-0002) from GNSS and GRACE data, respectively. Spatially, the size of the RSL uncertainties varies across North America with the largest from Hudson Bay and near previous ice margins along the northern Atlantic and Pacific coasts, which suggests 3D viscosity structure in the lower mantle and laterally varying lithospheric thickness. Temporally, RSL uncertainties decrease from the Last Glacial Maximum to present except for west of Hudson Bay and the northeastern Pacific coast. The uncertainties of both these regions increase from 30 to 45 m between 15 and 11 ka BP, which may be due to the rapid decrease of surface loading at that time. Present‐day urn:x-wiley:00948276:media:grl60497:grl60497-math-0003 and urn:x-wiley:00948276:media:grl60497:grl60497-math-0004 uncertainties are largest in southwestern Hudson Bay with magnitudes of 2.4 mm/year and 0.4 μGal/year, mainly due to the 3D viscosity structure in the lower mantle. Ministry of Education (MOE) National Research Foundation (NRF) Published version We thank Donald Argus and an anonymous reviewer for their very constructive comments, which have helped to improve the manuscript. Patrick Wu received GRF grant 17315316 from the Hong Kong Research Grants Council. Tanghua Li and Benjamin P. Horton are supported by the Singapore Ministry of Education Academic Research Fund MOE2019‐T3‐1‐004 and MOE2018‐T2‐1‐030, the National Research Foundation Singapore, and the Singapore Ministry of Education, under the Research Centers of Excellence initiative. Hansheng Wang is funded by the National Key R & D Program of China (2017YFA0603103) and National Natural Science Foundation of China (41431070 and 41974009). The research of W.R. Peltier at Toronto is supported by NSERC discovery grant A9627. The FE calculation was performed with the ABAQUS package from Hibbitt, Karlsson, and Sorensen Inc. This research is conducted in part using the research computing facilities and/or advisory services offered by Information Technology Services, the University of Hong Kong. This article is a contribution to PALSEA (Palaeo‐Constraints on Sea‐Level Rise), HOLSEA, and International Geoscience Program (IGCP) Project 639, “Sea‐Level Changes from Minutes to Millennia”. This work is Earth Observatory of Singapore contribution 293. The mean GIA signals of RSL, urn:x-wiley:00948276:media:grl60497:grl60497-math-0076, and urn:x-wiley:00948276:media:grl60497:grl60497-math-0077 with 1σ, 2σ, and 3σ uncertainties are provided for downloading in DR‐NTU (Data) with open access (https://doi.org/10.21979/N9/26AY8H). The deglacial RSL data, observed GNSS data used in this study are from the supplementary information of the corresponding references (with link) that are listed in the References List: Engelhart & Horton, 2012; Engelhart et al., 2015; Hawkes et al., 2016; Khan et al., 2017; Love et al., 2016; Peltier et al., 2015; Vacchi et al., 2018.

We are just beginning to understand how spaceflight may impact brain function. As NASA proceeds with plans to send astronauts to the Moon and commercial space travel interest increases, it is critical to understand how the human brain and peripheral nervous system respond to zero gravity. Here, we developed and refined head-worn transcranial magnetic stimulation (TMS) systems capable of reliably and quickly determining the amount of electromagnetism each individual needs to detect electromyographic (EMG) threshold levels in the thumb (called the resting motor threshold (rMT)). We then collected rMTs in 10 healthy adult participants in the laboratory at baseline, and subsequently at three time points onboard an airplane: (T1) pre-flight at Earth gravity, (T2) during zero gravity periods induced by parabolic flight and (T3) post-flight at Earth gravity. Overall, the subjects required 12.6% less electromagnetism applied to the brain to cause thumb muscle activation during weightlessness compared to Earth gravity, suggesting neurophysiological changes occur during brief periods of zero gravity. We discuss several candidate explanations for this finding, including upward shift of the brain within the skull, acute increases in cortical excitability, changes in intracranial pressure, and diffuse spinal or neuromuscular system effects. All of these possible explanations warrant further study. In summary, we documented neurophysiological changes during brief episodes of zero gravity and thus highlighting the need for further studies of human brain function in altered gravity conditions to optimally prepare for prolonged microgravity exposure during spaceflight.

Objective: The creation of artificial gravity on board a space station is one of the promising methods for preventing health problems during space missions; a short-radius centrifuge (SRC) is the model of such a method on Earth. Our goal was to evaluate the sensitivity of bioimpedance polysegmental measurements for monitoring of the body regions' blood-filling redistribution and to analyze the dynamics of blood-filling redistribution during rotation in three SRC rotation modes. Approach: Nine healthy male volunteers have been observed under three SRC rotation modes with a maximum acceleration of 2.05 standard Earth gravity (g), 2.47 g, 2.98 g along the body vertical axis towards the legs with a rotation radius of 235 cm. The 5 kHz electrical resistance was evaluated using a bioimpedance analyzer in a polysegmental mode. Main results: Twenty-five correct records were made, of which four records were incomplete since the tests had to be stopped because the subjects were not feeling well. There was a blood-filling decrease in the head region; resistance increased to +15.4% ± 4.1% in the first SRC rotation mode. The electrical resistance of the leg regions decreased to −16.5% ± 2.3%. Slowdown of the SRC led to the reverse changes in resistance. The blood redistribution in the head and leg regions was independent of the mode of SRC rotation during the first 30 min, and varied on average by +10% and −15% respectively. Significance: Bioimpedance monitoring is promising for detection and prediction of blood circulation changes during rotation on the SRC.

A new method to detect paleolakes via their gravity signal is presented (here with implications for geoscience and archaeology). The gravity aspects or descriptors (gravity anomalies/disturbances, second radial derivatives, strike angles and virtual deformations) were computed from the global static combined gravity field model EIGEN 6C4 for an application in archaeology and geoscience in Egypt and surrounding countries. The model consists of the best now available satellite and terrestrial data, including gradiometry from the GOCE mission. EIGEN 6C4 has the ground resolution ~10 km. From archaeological literarure we took the positions of archaeological sites of the Holocene occupations between 8500 and 5300 BC (8.5-5.3 ky BC) in the Eastern Sahara, Western Desert, Egypt. We correlated the features found from the gravity data with the locations; the correlation is good, assuming that the sites were mostly at paleolake boarders or at rivers. We suggest position, extent and shape of a paleolake. Then, we have estimated a possible location, extent and shape of the putative paleolake(s). We also reconsider the origin of Libyan Desert glass (LDG) in the Great Sand Sea (GSS) and support a hypothesis about an older impact structure created in GSS, repeatedly filled by water, which might be a part of some of the possible paleolake(s).

Since launch, radio science has been a key component of the Juno mission to Jupiter. The prime objective of the radio science investigation is to estimate the gravitational field of Jupiter from the Doppler shift on the radio link between the spacecraft and the Earth-based observing antennas of NASA's Deep Space Network (DSN). In addition to estimation of the gravitational field, radio science has provided critical engineering support to the Juno mission. Utilizing high-sensitivity open-loop receivers and real-time signal processing, radio science is able to detect the ‘heartbeat’ of the Juno spacecraft and determine the current state of the spacecraft. The Juno spacecraft utilizes two frequencies for communication with Earth: the telecommunications system X-band link and the radio science Ka-band link. Radio science has provided communications monitoring support for the spacecraft launch in 2011, spacecraft main engine firings (including Deep Space Maneuvers in 2012 and Jupiter Orbit Insertion in 2016), the Earth gravity assist flyby in 2013, and times when the spacecraft was off-Earth point during Jupiter closest approach with a weak signal level. By measuring the signal-to-noise ratio, received carrier frequency, and subcarrier frequency of the X-band downlink signal in real-time, radio science is able to determine the state of the spacecraft in scenarios where the link margin is not sufficient to support telemetry. An off-nominal spacecraft state will change the signal-to-noise level, subcarrier frequency, and spin modulation of the carrier frequency which are detectable in the open-loop receiver of the DSN. With the addition of multiple frequency shift keying (MFSK) ‘tones’ encoding, the subcarrier frequency can be changed onboard the spacecraft for determination of selected events by the flight team. Tones were utilized during main engine firings on Juno, including Jupiter Orbit Insertion (JOI). Tones are decoded in near real-time by the Entry, Descent, and Landing (EDL) Data Analysis (EDA) system downstream of the DSN open-loop receivers. Robust implementation of hardware, software, and operations planning has ensured successful data collection and real-time status reporting of spacecraft state to the Juno mission. Lessons learned from communicating with Juno in this way while in the harsh environment of Jupiter are documented and discussed in the context of upcoming missions to Jupiter.

Humans expect downwards moving objects to accelerate and upwards moving objects to decelerate. These results have been interpreted as humans maintaining an internal model of gravity. We have previously suggested an interpretation of these results within a Bayesian framework of perception: earth gravity could be represented as a Strong Prior that overrules noisy sensory information (Likelihood) and therefore attracts the final percept (Posterior) very strongly. Based on this framework, we use published data from a timing task involving gravitational motion to determine the mean and the standard deviation of the Strong Earth Gravity Prior. To get its mean, we refine a model of mean timing errors we proposed in a previous paper (Björn Jörges & López-Moliner, 2019), while expands the range of conditions under which it yields adequate predictions of performance. This underscores our previous conclusion that the gravity prior is likely to be very close to 9.81 m/s². To obtain the standard deviation, we identify different sources of sensory and motor variability reflected in timing errors. We then model timing responses based on quantitative assumptions about these sensory and motor errors for a range of standard deviations of the earth gravity prior, and find that a standard deviation of around 2 m/s² makes for the best fit. This value is likely to represent an upper bound, as there are strong theoretical reasons along with support empirical evidence for the standard deviation of the earth gravity being lower than this value.

Virtual reality is used to manipulate sensorimotor interactions in a controlled manner. A critical issue is represented by the extent to which virtual scenarios must conform to physical realism to allow ecological human–machine interactions. Among the physical constraints, Earth gravity is one of the most pervasive and significant for sensorimotor coordination. However, it is still unclear whether visual perception is sensitive to the level of gravity acting on target motion displayed in virtual reality, given the poor visual discrimination of accelerations. To test gravity sensitivity, we asked participants to hit a virtual ball rolling down an incline and falling in air, and to report whether ball motion was perceived as natural or unnatural. We manipulated the gravity level independently for the motion on the incline and for the motion in air. The ball was always visible during rolling, whereas it was visible or occluded during falling before interception. The scene included several cues allowing metric calibration of visual space and motion. We found that the perception rate of natural motion was significantly higher and less variable when ball kinematics was congruent with Earth gravity during both rolling and falling. Moreover, the timing of target interception was accurate only in this condition. Neither naturalness perception nor interception timing depended significantly on whether the target was visible during free-fall. Even when occluded, free-fall under natural gravity was correctly extrapolated from the preceding, visible phase of rolling motion. Naturalness perception depended on motor performance, in addition to the gravity level. In sum, both motor and perceptual responses were guided by an internal model of Earth gravity effects. We suggest that, in order to enhance perceptual sensitivity to physical realism, virtual reality should involve visual backgrounds with metric cues and closed-loop sensorimotor interactions. This suggestion might be especially relevant for the design of rehabilitation protocols.

The launch of dedicated satellite missions at the beginning of the 2000s led to significant improvement in the determination of Earth gravity field models. As a consequence of this progress, both the accuracies and the spatial resolutions of the global geopotential models increased. However, the spectral behaviors and the accuracies of the released models vary mainly depending on their computation strategies. These strategies are briefly explained in this article. Comprehensive quality assessment of the gravity field models by means of spectral and statistical analyses provides a comparison of the gravity field mapping accuracies of these models, as well as providing an understanding of their progress. The practical benefit of these assessments by means of choosing an optimal model with the highest accuracy and best resolution for a specific application is obvious for a broad range of geoscience applications, including geodesy and geophysics, that employ Earth gravity field parameters in their studies. From this perspective, this study aims to evaluate the GOCE High-Level Processing Facility geopotential models including recently published sixth releases using different validation methods recommended in the literature, and investigate their performances comparatively and in addition to some other models, such as GOCO05S, GOGRA04S and EGM2008. In addition to the validation statistics from various countries, the study specifically emphasizes the numerical test results in Turkey. It is concluded that the performance improves from the first generation RL01 models toward the final RL05 models, which were based on the entire mission data. This outcome was confirmed when the releases of different computation approaches were considered. The accuracies of the RL05 models were found to be similar to GOCO05S, GOGRA04S and even to RL06 versions but better than EGM2008, in their maximum expansion degrees. Regarding the results obtained from these tests using the GPS/leveling observations in Turkey, the contribution of the GOCE data to the models was significant, especially between the expansion degrees of 100 and 250. In the study, the tested geopotential models were also considered for detailed geoid modeling using the remove-compute-restore method. It was found that the best-fitting geopotential model with its optimal expansion degree (please see the definition of optimal degree in the article) improved the high-frequency regional geoid model accuracy by almost 15%.

This study investigates critical heat flux (CHF) for subcooled flow boiling of n-Perfluorohexane based on results of pre-launch Earth-gravity Mission Sequence Tests (MSTs) of the Flow Boiling and Condensation Experiment (FBCE), which was launched to the International Space Station (ISS) in August 2021. CHF measurements were made in a rectangular channel having a 2.5 mm by 5 mm cross-section and a 114.6-mm long heated segment. Both single-sided and double-sided heating were tested in vertical upflow in Earth gravity for a variety of inlet conditions. The inlet subcooling was varied in the range of 0.4 – 32.0°C and encompassed both near-saturated and highly subcooled conditions. Experimental trends and high-speed video records were investigated to better understand the mechanism of CHF. Overall trends show CHF increases as flow rate and/or inlet subcooling are increased. Flow features from the events around CHF justify the applicability of the Interfacial Lift-off Model and the determination of limiting criteria for its application. The present experimental data are combined with prior databases for various flow orientations with respect to Earth gravity and microgravity data collected on parabolic flights. Predictions are made using the Interfacial Lift-off Model for this consolidated subcooled-inlet FBCE-CHF database. A heat utility ratio was included in the model to capture the effects of subcooling and corresponding thermodynamic non-equilibrium. An overall mean absolute error of 19.04% indicates good predictive capability of the model for both heating configurations, different gravity environments, and a wide range of inlet subcooling.

The understanding of melting characteristics and mechanism of high temperature encapsulated phase change material (EPCM) is important for its application in heat storage systems. In this study, a two-dimensional axisymmetric numerical model is established to simulate the melting of spherical EPCMs with air void on the top. Besides buoyancy driven natural convection, Marangoni convection due to the thermocapillary force at the air-molten PCM interface is considered for the first time in this topic. To estimate thermocapillary force more accurately, the air-PCM interface is tracked by the coupled level-set and VOF method. The numerical simulations are conducted for EPCMs with Al2O3 shell and NaNO3 core with the different EPCM diameters and under the different gravity levels. It is found that Marangoni convection mainly affects the early and middle stages of PCM melting process, and its importance relative to buoyancy driven natural convection increases as the diameter of EPCM and gravity level decreases. For the EPCMs with diameter greater than 24 mm under the earth gravity, Marangoni convection has negligible effect, while for 12 mm diameter EPCM under the moon gravity, the complete melting time could be 19% shorter under the additional role of Marangoni convection. The solid PCM profile, fluid flow structure, melting ratio and heat transfer rate during the melting of EPCM under the effects of natural convection and Marangoni convection are also analyzed in detail.

A water droplet can exhibit a high apparent contact angle on a hydrophobic fibrous surface. However, a high contact angle does not guarantee droplet mobility on the surface. The reasons behind droplet adhesion to a hydrophobic fibrous surface has not yet been analyzed or formulated. In this work, the force required to detach a droplet from a hydrophobic fibrous surface is investigated experimentally and computationally. Electrospun Polystyrene mats are considered for this study as they exhibit high contact angles coupled with poor droplet mobility. To better isolate the effects of microstructural properties of the mats and study their effects on droplet detachment, randomness of the fiber orientation is minimized by producing highly oriented fibers in orthogonal layers. As the earth gravity is not strong enough to detach small droplets from such surfaces, aqueous ferrofluid droplets are used in a controllable magnetic field to enhance the effect of gravity. The detachment process is recorded via a high-speed camera and the images are used to detect the moment of detachment and to analyze droplet shape before and during detachment. Numerical simulations are also conducted to provide additional insight into the physics of droplet detachment, and more importantly, to develop an equation for estimating droplet detachment force from a fibrous surface. In this paper, we discuss the effects of fiber properties, e.g., Young-Laplace contact angle or fiber spacing, on the force needed to detach a droplet from a fibrous surface.