« Go Back

Research Containing: MSG

Structural Transitions of MR Fluids in Microgravity

by on 9 June 2015in Physical Sciences No comment

We present studies of colloidal suspensions of magnetizable particles with the aim of understanding the kinetics and underlying microstructural evolution of the liquid-solid transitions these systems exhibit in external magnetic fields. Critically, such studies are limited on Earth due to catastrophic sedimentations of the suspensions. Structural changes are investigations under steady and intermittent (pulsed) magnetic fields. Here, we focus on image processing methods used to extract structural information from video microscopy data obtained from InSPACE experiments carried out in the Microgravity Science Glovebox on the International Space Station. These experiment provide important information for the development of magnetorheological (MR) fluids in technological application, such as actuators and sensors while also providing critical insight into the fundamental physics of liquid-solid transitions.

Related URLs:
http://dx.doi.org/10.2514/6.2008-815

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

by on 9 June 2015in Physical Sciences No comment

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 (89.5 mm dia.) 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.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0017931014011624

SUBSA and PFMI Transparent Furnace Systems Currently in use in the International Space Station Microgravity Science Glovebox

by on 9 June 2015in Physical Sciences No comment

The Solidification Using a Baffle in Sealed Ampoules (SUBSA) and Pore Formation and Mobility Investigation (PFMI) furnaces were developed for operation in the International Space Station (ISS) Microgravity Science Glovebox (MSG). Both furnaces were launched to the ISS on STS-111, June 4, 2002, and are currently in use on orbit. The SUBSA furnace provides a maximum temperature of 850 C and can accommodate a metal sample as large as 30 cm long and 12mm in diameter. SUBSA utilizes a gradient freeze process with a minimum cooldown rate of 0.5C per min, and a stability of +/- 0.15C. An 8 cm long transparent gradient zone coupled with a Cohu 3812 camera and quartz ampoule allows for observation and video recording of the solidification process. PFMI is a Bridgman type furnace that operates at a maximum temperature of 130C and can accommodate a sample 23cm long and 10mm in diameter. Two Cohu 3812 cameras mounted 90 deg apart move on a separate translation system which allows for viewing of the sample in the transparent hot zone and gradient zone independent of the furnace translation rate and direction. Translation rates for both the cameras and furnace can be specified from 0.5micrometers/sec to 100 micrometers/sec with a stability of +/-5%. The two furnaces share a Process Control Module (PCM) which controls the furnace hardware, a Data Acquisition Pad (DaqPad) which provides signal condition of thermal couple data, and two Cohu 3812 cameras. The hardware and software allow for real time monitoring and commanding of critical process control parameters. This paper will provide a detailed explanation of the SUBSA and PFMI systems along with performance data and some preliminary results from completed on-orbit processing runs.

Related URLs:
http://dx.doi.org/10.2514/6.2003-1362

Flammability Aspects of Fabric in Opposed and Concurrent Air Flow in Microgravity

by on 9 June 2015in Physical Sciences No comment

Microgravity combustion tests burning fabric samples were performed aboard the International Space Station. The cotton-fiberglass blend samples were mounted inside a small wind tunnel which could impose air flow speeds up to 40 cm/s. The wind tunnel was installed in the Microgravity Science Glovebox which supplied power, imaging, and a level of containment. The effects of air flow speed on flame appearance, flame growth, and spread rates were determined in both the opposed and concurrent-flow configuration. For the opposed flow configuration, the flame quickly reached steady spread for each flow speed, and the spread rate was fastest at an intermediate value of flow speed. These tests show the enhanced flammability in microgravity for this geometry, since, in normal gravity air, a flame self-extinguishes in the opposed flow geometry (downward flame spread). In the concurrent-flow configuration, flame size grew with time during the tests. A limiting length and steady spread rate were obtained only in low flow speeds (≤ 10 cm/s) for the short-length samples that fit in the small wind tunnel. For these conditions, flame spread rate increased linearly with increasing flow. This is the first time that detailed transient flame growth data was obtained in purely forced flows in microgravity. In addition, by decreasing flow speed to a very low value (around 1 cm/s), quenching extinction was observed. The valuable results from these long-duration experiments validate a number of theoretical predictions and also provide the data for a transient flame growth model under development.

Related URLs:

Observation of an Aligned Gas – Solid Eutectic during Controlled Directional Solidification aboard the International Space Station – Comparison with Ground-based Studies

by on 9 June 2015in Physical Sciences No comment

Direct observation of the controlled melting and solidification of succinonitrile was conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) in an atmosphere of nitrogen at 450 millibar pressure for eventual processing in the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) on board the ISS. Real time visualization during controlled directional melt back of the sample showed nitrogen bubbles emerging from the interface and moving through the liquid up the imposed temperature gradient. Over a period of time these bubbles disappear by dissolving into the melt. Translation is stopped after melting back of about 9 cm of the sample, with an equilibrium solid-liquid interface established. During controlled re-solidification, aligned tubes of gas were seen growing perpendicular to the planar solid/liquid interface, inferring that the nitrogen previously dissolved into the liquid SCN was now coming out at the solid/liquid interface and forming the little studied liquid = solid + gas eutectic-type reaction. The observed structure is evaluated in terms of spacing dimensions, interface undercooling, and mechanisms for spacing adjustments. Finally, the significance of processing in a microgravity environment is ascertained in view of ground-based results.

Related URLs:

Pyrolysis Smoke Generated Under Low-Gravity Conditions

by on 9 June 2015in Physical Sciences No comment

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 samples returned to earth, it was found that the smoke can form an agglomerate shape as well as a spherical shape, which had previously been the assumed shape. A possible explanation for the shape of the smoke generated by each material is presented.Copyright 2015 American Association for Aerosol Research

Related URLs:
http://dx.doi.org/10.1080/02786826.2015.1025125

Preliminary Findings from the SHERE ISS Experiment

by on 9 June 2015in Physical Sciences No comment

The Shear History Extensional Rheology Experiment (SHERE) is an International Space Station (ISS) glovebox experiment designed to study the effect of preshear on the transient evolution of the microstructure and viscoelastic tensile stresses for monodisperse dilute polymer solution. The SHERE experiment hardware was launched on Shuttle Mission STS-120 (ISS Flight 10A) on October 22, 2007, and 20 fluid samples were launched on Shuttle Mission STS-123 (ISS Flight 1J/A) on March 11, 2008. Astronaut Gregory Chamitoff performed experiments during Increment 17 on the ISS between June and September 2008. A summary of the ten year history of the hardware development, the experiment’s science objectives, and Increment 17’s flight operations are discussed in the paper. A brief summary of the preliminary science results is also discussed.

Related URLs:
http://dx.doi.org/10.2514/6.2009-618

Morphological Evolution of Directional Solidification Interfaces in Microgravity: An Analysis of Model Experiments Performed on the International Space Station

by on 9 June 2015in Physical Sciences No comment

A series of experiment performed using the Pore Formation and Mobility Investigation (PMFI) apparatus within the Microgravity Science Glovebox (MSG) facility on board the International Space Station (ISS( has provided video images of the morphological evolution of a three-dimensional interface in a diffusion controlled regime. The experiment samples, 1 cm inner diameter and approximately 30 cm in length, are filled with alloys of succinonitrile (SCN) and water. The compositions of the samples processed and analyzed are 0.25, 0.5 and 1.0 wt% water. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and controlled from the ground Telescience Center (TSC) at the Marshall Space Flight Center. Images obtained from the on-orbit experiments have been received and are being analyzed. A ground-based thin-sample directional solidification system for correlation to flight experiments is described. Using this ground-based system, a series of experiments has been performed for direct comparison with the flight data. The initial results of these comparisons as well as implications to future microgravity experiments are presented and discussed.

Related URLs:
http://dx.doi.org/10.2514/6.2005-917

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

by on 9 June 2015in Physical Sciences No comment

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.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S1540748914000674

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

by on 9 June 2015in Physical Sciences No comment

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.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0094576508000465