Microgravity Science Glovebox Research Articles

Enhanced heat transfer in microgravity from asymmetric sawtooth microstructure with engineered cavities

Nucleate pool boiling in microgravity is influenced by stagnant vapor bubble dynamics, leading to early dryout of the heated surface compared to terrestrial conditions. The Asymmetric Sawtooth and Cavity-Enhanced Nucleation-driven Transport (ASCENT) investigation studied an engineered microstructure in a nucleate pool boiling setup aboard the International Space Station (ISS) from November 2022-January 2023. The experiment was housed in the Microgravity Science Glovebox (MSG) and used degassed FC-72 as the test liquid. The engineered microstructure consisted of repeating mm-sized 60°-30° sawtooth structures located within a hermetically sealed square ampoule as the test chamber. Experimental investigations were conducted to explore a range of input heat fluxes, ranging from 0.5 to 2.3 W/cm². The resulting vapor dynamics and heat transfer were compared against a flat baseline surface. Both surfaces contained 250 µm square cavities spaced 1-mm apart. The constrained dimensions of the square chamber severely influenced vapor bubble dynamics across the heated surface. The presence of a liquid layer beneath vapor slugs on the microstructure was observed, in contrast to the baseline surface, where no liquid layer was visually detected. The transient heat transfer coefficient from the microstructure was higher than the baseline surface as the vapor bubbles grew larger at constant heat flux due to liquid film access provided by the asymmetric ridges on the microstructure. A significant increase in the heat transfer coefficient was observed at 1.8 W/cm2, potentially due to vigorous nucleation in the observed liquid pockets along the microstructure, increasing the heat transfer coefficient from 2900 to 6200 W/m2K. Nucleation was observed at heat fluxes as low as 0.5 W/cm2 from the engineered cavities, and a quasi-steady heat transfer coefficient of 2200 W/m2K was obtained at 2.3 W/cm2 from the microstructure surface. The quasi-steady analysis also indicated that both surfaces performed similarly in microgravity and terrestrial gravity in the same experimental setup. The results demonstrate that the liquid film dynamics underneath vapor slugs influence heat transfer to a large extent in microgravity conditions.

Implementation of an ultrasonic fluid manipulation experiment on the International Space Station

The International Space Station (ISS) provides a unique opportunity to investigate acoustic radiation force interactions with a minimal interference from gravity. There are many design considerations to make when creating an experiment that is suited for use on board the ISS. NASA’s primary concerns with all experiments implemented in the ISS are with the safety of the crew and the success of the mission. Acoustic experiments are surprisingly rare on the ISS and present additional unique design challenges. This is especially true for experiments operated under water. Our work implements a high-intensity acoustic vortex beam under water for single droplet tractoring and capture operated inside the Microgravity Science Glovebox (MSG) on the ISS. The experiment payload consists of a signal generator, an amplifier module, and a sealed water chamber. A secondary fluid immiscible with water is injected into the chamber for acoustic manipulation, and the results of the experiment are recorded as high-definition video.

On the Monitoring of the Vibratory Environment of DCMIX4 Campaign. Preliminary Results

This work presents the preliminary characterization of the vibrational environment of the DCMIX4 thermodiffusion experiment conducted onboard the ISS from December 2018 to March 2019. Given the long duration of each one of the 58 runs of the campaign and to ensure a correct interpretation of the results, an accurate analysis of acceleration levels all along the experiment is advisable. Digital signals coming from the nearest sensor, es09006, located in the Microgravity Science Glovebox (Destiny module) were downloaded from the PIMS NASA website. The techniques used to identify the main disturbances during the experiments were defined both in time and frequency domains. It is expected that the results obtained can help the experimentalist to have an overview of the possible sources of disturbances that may affect their experiments. To visualize the possible impact of the accelerometric environment on the experiment a numerical simulation has been performed. Four signals have been chosen, one considering the ideal case g = 0, one coming from the OSS raw sensor (outside the Microgravity Science Glovebox) and the other two, coming from the es09006 sensor that needed to be mathematical manipulated for considering only the low frequency range. Independent of the location of the sensor, numerical simulations do not detect, in any case, appreciable flow disturbances if quiescent periods are considered. Therefore, in case the reference sensor is not available one can use other sensors placed in the same module.

Thermodiffusion in Ternary Mixtures of Water/Ethanol/Triethylene Glycol: First Report on the DCMIX3-Experiments Performed on the International Space Station

We report on thermodiffusion experiments conducted on the International Space Station ISS during fall 2016. These experiments are part of the DCMIX (Diffusion and thermodiffusion Coefficients Measurements in ternary Mixtures) project, which aims at establishing a reliable data base of non-isothermal transport coefficients for selected ternary liquid mixtures. The third campaign, DCMIX3, focuses on aqueous systems with water/ethanol/triethylene glycol as an example, where sign changes of the Soret coefficient have already been reported for certain binary subsystems. Investigations have been carried out with the SODI (Selectable Optical Diagnostics Instrument) instrument, a Mach-Zehnder interferometer set up inside the Microgravity Science Glovebox in the Destiny Module of the ISS. Concentration changes within the liquids have been monitored in response to an external temperature gradient using phase-stepping interferometry. The complete data set has been made available in spring 2017. Due to additionally available measurement time, it was possible to collect a complete data set at 30∘C and an almost complete data set at 25∘C, which significantly exceeds the originally envisaged measurements at a single temperature only. All samples could be measured successfully. The SODI instrument and the DCMIX experiments have proven reliable and robust, allowing to extract meaningful data even in case of unforeseen laser instabilities. First assessments of the data quality have revealed six out of 31 runs with some problems in image contrast and/or phase step stability that will require more sophisticated algorithms. This publication documents all relevant parameters of the conducted experiments and also events that might have an influence on the final results. The compiled information is intended to serve as a starting point for all following data evaluations.

Onsite vibrational characterization of DCMIX2/3 experiments

The SODI-DCMIX thermodiffusion series experiments are part of the fluid research program carried out by the European Space Agency on board of the International Space Station (ISS). In particular, DCIMIX2/3 were conducted in the past inside the Microgravity Science Glovebox in the US Laboratory. Due to the physical nature of the processes implied, these kind of runs were very long and particularly delicate because the low vibratory limit requirements must be maintained for hours. This restrictive condition not always is achieved, therefore, an accurate surveillance of the acceleration levels along the different experiments is necessary, to ensure a correct interpretation of the experimental results.This work analyzes onsite vibrational environment of DCMIX2/3 covering the periods in which the experiments were going on. To do so, acceleration signals only coming from the es03 sensor, nearest to the experimental equipment and located in the Glovebox, were downloaded from the PIMS NASA website. To be as precise as possible the signals have always been treated minute by minute. To detect the transient disturbances along the experiments, several warnings were considered. First, 1 min RMS values, for the three acceleration components were evaluated, in time and in frequency domain. Additional information was obtained by plotting the power spectral densities of the signals, PSD, and their spectrogram with the aim of characterizing long periods of acceleration data. Due to great influence of low frequencies in this type of experiments, the Frequency Factor Index, FFI, was evaluated each minute. Complementary, the spectral entropy evolution was proposed as a fast new indicator of external perturbations. It has been found a good correlation between the spectrogram, temporal RMS and spectral entropy. Finally, a graphic representation of the points associated to the 1-min RMS values in one-third-octave frequency intervals which exceed the ISS limit curve requirements, was considered as a new and easy strategy for depicting the warnings that recognize the main disturbances along the experiment.

Microgravity flammability boundary for PMMA rods in axial stagnation flow: Experimental results and energy balance analyses

For the first time, a series of concurrent-flow rod flammability tests were conducted in microgravity aboard the International Space Station. A small flow duct was used to create 0 to 55cm/s flows past three sizes of clear and black PMMA rods. The ambient oxygen concentration in the Microgravity Science Glovebox was varied from 13.6% to 22.2%. Oxygen, carbon dioxide, and carbon monoxide gas sensors provide initial and final readings for each test and indicate that the flames are globally stoichiometric at higher oxygen concentrations, but become more globally fuel rich as the minimum oxygen concentration is approached due to excess pyrolyzate leakage out of the open tail of the hemispherical flames. Quenching extinction occurs at very low forced flows, where the flame shrinks to a hemispherical blue flame and oscillates with increasing amplitude just before going out. Blowoff extinction is initiated by the formation of a hole in the flame sheet in the stagnation region of the flame. A critical Damkohler number formulation is applied across the flammability boundary, and the critical flame temperatures are derived. These critical flame temperatures are then used in a Nusselt number correlation to estimate the convective heat flux to the stagnation region of the rod. A model of surface energy balance is formulated that uses the critical flame temperature and convective heat flux to derive the mass burning rate along the boundary. The rod regression rates calculated from this model compare favorably with the experimental measurements. The surface energy balance reveals that along the blowoff branch, heat losses are negligible whereas in the quenching region, surface radiative loss dominates. At the bottom of the flammability map, the transition from blowoff to quenching occurs when the convective flows become the same order of magnitude as diffusive flows, shifting the critical Damkohler number from residence time limitations to diffusive time limitations.

Concurrent flame growth, spread, and quenching over composite fabric samples in low speed purely forced flow in microgravity

Flame growth, spread, and quenching extinction over a thin composite cotton-fiberglass fabric blend (referred to as the SIBAL fabric) were studied in low-speed concurrent purely forced flows aboard the International Space Station. The tests were conducted in a small flow duct within the Microgravity Science Glovebox. The fuel samples measured 1.2 and 2.2 cm wide and 10 cm long. Ambient oxygen was varied from 21% down to 16% molar concentration and flow speed from 55 cm/s down to 1 cm/s. A slow purely forced flow resulted in a small flame, enabling us to observe the entire history of flame development including ignition, flame growth, steady spread (in some cases), and decay at the end of the sample. In addition, by decreasing flow velocity during some of the tests, low-speed flame quenching extinction limits were determined as a function of oxygen percentage. The quenching speeds were found to be between 1 and 5 cm/s with higher extinction speeds in lower oxygen atmospheres. The shape of the quenching boundary supports the prediction by earlier theoretical models. These long duration microgravity experiments provide a rare opportunity for solid fuel combustion since microgravity time in ground-based facilities is generally not sufficient. This is the first time that a low-speed quenching boundary in concurrent spread is mapped in a clean and unambiguous manner. A previously developed three-dimensional transient model is modified to compare with the experiment. The modification includes the use of two-step SIBAL fabric pyrolysis kinetics where the rate constants are determined using Thermo-Gravimetric Analysis data. The model yields good quantitative comparison on the quenching boundary, the flame transient development, and the steady flame spread rates.

Pyrolysis Smoke Generated Under Low-Gravity Conditions

A series of smoke experiments were carried out in the Microgravity Science Glovebox on the International Space Station (ISS) Facility to assess the impact of low-gravity conditions on the properties of the smoke aerosol. The smokes were generated by heating five different materials commonly used in space vehicles. This study focuses on the effects of flow and heating temperature for low-gravity conditions on the pyrolysis rate, the smoke plume structure, the smoke yield, the average particle size, and particle structure. Low-gravity conditions allowed a unique opportunity to study the smoke plume for zero external flow without the complication of buoyancy. The diameter of average mass increased on average by a factor of 1.9 and the morphology of the smoke changed from agglomerate with flow to spherical at no flow for one material. The no flow case is an important scenario in spacecraft where smoke could be generated by the overheating of electronic components in confined spaces. From electron microcopy of...

Nucleate Pool Boiling eXperiment (NPBX) in microgravity: International Space Station

A series of nucleate pool boiling experiments were conducted in the Boiling Experimental Facility (BXF) located in the Microgravity Science Glovebox (MSG) on board the International Space Station (ISS) during the period March–May, 2011. Nucleate Pool Boiling eXperiment (NPBX) was one of the two experiments housed in the BXF. Results of experiments on natural convection, nucleate pool boiling heat transfer and critical heat flux are described. Perfluoro-n-hexane was used as the test liquid. The test liquid contained dissolved gas. The test surface was a polished aluminum disc (89.5mmdia.) heated from below with strain gage heaters. Five cylindrical cavities were formed on the surface with four cavities located at the corners of a square and one in the middle, to study bubble dynamics and initiate nucleate boiling. During experiments the magnitude of mean gravity level normal to the heater surface varied from 1.7×10−7ge to 6×10−7ge.The results of the experiments show that at low superheats, bubbles generated on the heater surface slide and merge to yield a large bubble located in the middle of the heater. At high superheats, the large bubble may lift off from the heater but continue to hover near the surface. In both these scenarios, the large bubble serves as a vapor sink. Natural convection heat transfer in microgravity was found to be consistent with that predicted by available correlations. Steady state nucleate boiling and maximum heat fluxes are found to be lower than those obtained under earth normal gravity conditions. The heat transfer coefficients for nucleate pool boiling are found to be weakly dependent on the level of gravity (h/hge∝(g/ge)1/8). Maximum heat flux also shows a weaker dependence on gravity than that given by the hydrodynamic theory of boiling. The data are useful for calibration of results of numerical simulations. Any correlations that are developed for nucleate boiling heat transfer under microgravity condition must account for the existence of vapor escape path (large vapor bubble acting as a sink) from the heater, relative size of the large bubble and heater, and the size and geometry of the chamber used.

An experimental and computational study of soot formation in a coflow jet flame under microgravity and normal gravity

Upon the completion of the Structure and Liftoff in Combustion Experiment (SLICE) in March 2012, a comprehensive and unique set of microgravity coflow diffusion flame data was obtained. This data covers a range of conditions from weak flames near extinction to strong, highly sooting flames, and enabled the study of gravitational effects on phenomena such as liftoff, blowout and soot formation. The microgravity experiment was carried out in the Microgravity Science Glovebox (MSG) on board the International Space Station (ISS), while the normal gravity experiment was performed at Yale utilizing a copy of the flight hardware. Computational simulations of microgravity and normal gravity flames were also carried out to facilitate understanding of the experimental observations. This paper focuses on the different sooting behaviors of CH4 coflow jet flames in microgravity and normal gravity. The unique set of data serves as an excellent test case for developing more accurate computational models. Experimentally, the flame shape and size, lift-off height, and soot temperature were determined from line-of-sight flame emission images taken with a color digital camera. Soot volume fraction was determined by performing an absolute light calibration using the incandescence from a flame-heated thermocouple. Computationally, the MC-Smooth vorticity–velocity formulation was employed to describe the chemically reacting flow, and the soot evolution was modeled by the sectional aerosol equations. The governing equations and boundary conditions were discretized on an axisymmetric computational domain by finite differences, and the resulting system of fully coupled, highly nonlinear equations was solved by a damped, modified Newton’s method. The microgravity sooting flames were found to have lower soot temperatures and higher volume fraction than their normal gravity counterparts. The soot distribution tends to shift from the centerline of the flame to the wings from normal gravity to microgravity.

Nucleate Pool Boiling Experiments (NPBX) on the International Space Station

During the period of March–May 2011, a series of boiling experiments was carried out in the Boiling Experimental Facility (BXF) located in the Microgravity Science Glovebox (MSG) of the International Space Station (ISS). The BXF Facility was carried to ISS on Space Shuttle Mission STS–133 on February 24, 2011. Nucleate Pool Boiling Experiment (NPBX) was one of the two experiments housed in the BXF. Results of experiments on single bubble dynamics (e.g., inception and growth), multiple bubble dynamics (lateral merger and departure, if any), nucleate pool boiling heat transfer, and critical heat flux are described. In the experiments Perfluoro-n-hexane was used as the test liquid. The system pressure was varied from 51 to 243 kPa, pool temperature was varied from 30° to 59°C, and test surface temperature was varied from 40° to 80°C. The test surface was a polished aluminum disc (1 mm thick, 89.5 mm in diameter) heated from below with strain gage heaters. Five cylindrical cavities were formed on the surface with four cavities located at the corners of a square and one in the middle. During experiments the magnitude of mean gravity level normal to the heater surface varied from 1.2 × 10 − 7ge to 6 × 10 − 7ge. The results of the experiments show that a single bubble continues to grow to occupy the size of the chamber without departing from the heater surface. During lateral merger of bubbles, at high superheats a large bubble may lift off from the surface but continues to hover near the surface. Neighboring bubbles are continuously pulled into the large bubble. At low superheats bubbles at neighboring sites simply merge to yield a larger bubble. The larger bubble mostly locates in the middle of the heated surface and serves as a vapor sink. The latter mode continues to persist when boiling is occurring all over the heater surface. Heat fluxes for steady state nucleate boiling and critical heat fluxes are found to be much lower than those obtained under earth normal gravity conditions. The data are useful for calibration of results of numerical simulations. Any correlations that are developed for nucleate boiling heat transfer under microgravity condition must account for the existence of vapor escape path (sink) from the heater, size of the heater, and the size and geometry of the chamber.

Measurement of Smoke Particle Size under Low-Gravity Conditions

Smoke detection experiments were conducted in the Microgravity Science Glovebox (MSG) on the International Space Station (ISS) during Expedition 15 in an experiment entitled Smoke Aerosol Measurement Experiment (SAME). The preliminary results from these experiments are presented. In order to simulate detection of a prefire overheated-material event, samples of five different materials were heated to temperatures below the ignition point. The smoke generation conditions were controlled to provide repeatable sample surface temperatures and air flow conditions. The smoke properties were measured using particulate aerosol diagnostics that measure different moments of the size distribution. These statistics were combined to determine the count mean diameter which can be used to describe the overall smoke distribution.

Materials research conducted aboard the International Space Station: Facilities overview, operational procedures, and experimental outcomes

The Microgravity Science Glovebox (MSG) and Maintenance Work Area (MWA) are facilities aboard the International Space Station (ISS) have been successfully used to conduct experiments in support of, respectively, the Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI). The capabilities of these facilities are briefly discussed and then demonstrated by presenting “real-time” and subsequently down linked video-taped examples from the abovementioned experiments. Data interpretation, ISS telescience, some lessons learned, and the need of such facilities for conducting work in support of understanding materials’ behavior, particularly fluid processing and transport scenarios, in low-gravity environments, is discussed.

Reproducible Te-doped InSb experiments in Microgravity Science Glovebox at the International Space Station

Four Te-doped InSb crystals were directionally solidified under microgravity conditions at the International Space Station (ISS). Three Te-doped InSb crystals were grown at R=5 mm/h. One crystal was grown at R=3.33 mm/h. The distribution of Te was measured using secondary ion mass spectroscopy (SIMS). The initial transients in Te concentration were found to be consistent, yielding a diffusivity of Te in InSb melts of D=1×10 −5 cm 2/s. One experiment revealed a diffusion controlled final transient. In all experiments, the charge was pressurized by a piston and spring device, to prevent de-wetting.

Self-propagating combustion synthesis of intermetallic matrix composites in the ISS

Combustion Synthesis experiments have been performed on the ISS (International Space Station) during the Belgian taxi-flight mission ODISSEA in November 2002, in the framework of the ESA-coordinated project COSMIC (Combustion Synthesis under Microgravity Conditions). The main objective of the experiments was to investigate the general physico-chemical mechanisms of combustion synthesis processes and the formation of products microstructure. Within the combustion zone, a number of gravity-dependent phenomena occur, while other phenomena are masked by gravity. Under certain conditions, gravity-dependent secondary processes may also occur in the heat-affected zone after combustion. To study the influence of gravity, a specially dedicated reactor ensemble was designed and used in the Microgravity Science Glovebox (MSG) onboard the ISS. In this work, the experiment design is first discussed in terms of the experimental functionality and reactor ensemble integration in the MSG. To investigate microstructure formation, a sample constituted by a cylindrical portion followed by a conical one, the latter being inserted inside a massive copper block, is used. The experiment focused on the synthesis of intermetallic matrix composites (IMCs) based on the Al-Ti-B system. Depending on the composition, different intermetallic compounds (TiAl and TiAl3) can be formed as matrix phase while TiB2 represents the reinforcing particulate phase. During the ISS mission, six samples with a relatively high green density of 65%TD have successfully been processed. The influence of the composition on the combustion process will be examined.