Spatiotemporal dynamics of oscillatory cellular patterns in three-dimensional directional solidification

by on 22 August 2016in Biology & Biotechnology, Physical Sciences No comment

We report results of directional solidification experiments conducted on board the International Space Station and quantitative phase-field modeling of those experiments. The experiments image for the first time in situ the spatially extended dynamics of three-dimensional cellular array patterns formed under microgravity conditions where fluid flow is suppressed. Experiments and phase-field simulations reveal the existence of oscillatory breathing modes with time periods of several 10’s of minutes. Oscillating cells are usually noncoherent due to array disorder, with the exception of small areas where the array structure is regular and stable.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/23767735

Opposed-flow flame spread: A comparison of microgravity and normal gravity experiments to establish the thermal regime

by on 22 August 2016in Physical Sciences No comment

The thermal regime of flame spread over solid fuels constitutes the reference condition for all other flame spread research. Although the theory of flame spread in the thermal regime is well understood, the well- known closed-form formulas for flame spread do not compare well with available experimental data. The comparison is further complicated by the fact that establishing a thermal regime in a normal-gravity environment is difficult because of the buoyancy induced flow which may usher in finite-rate kinetics effect. As a result, even the transition thickness, when a fuel can be considered a thermally thick fuel, still lacks a widely accepted formula.;In this work we present opposed-flow flame spread data over varying thicknesses of poly-methyl methacrylate (PMMA) obtained in the International Space Station where the opposing flow velocity can be reduced arbitrarily without any interference from the gravity induced flow. We also present a larger set of spread rate data for the downward spreading configuration at normal gravity. A comparison be- tween the two data set allows us to establish the thermal limit for thin fuel for which the spread rate is independent of the opposing flow velocity. The classical thin-fuel spread rate formula is shown to fit well with the experimental results provided the adiabatic flame temperature is used in the flame coefficient that appears in the formula. The experimentally determined flame coefficient along with downward flame spread data for thick fuels are used to develop a closed-form expression for the transition thickness between thermally thin and thick fuels for downward spread in the thermal regime.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0379711215300424

The microgravity DSC-DCMIX1 mission onboard ISS: Experiment description and results on the measurement of the Soret coefficients for isobutylbenzene, dodecane, tetralin ternary hydrocarbons mixtures

by on 22 August 2016in Physical Sciences No comment

In the energy sector, in particular for hydrocarbon reservoirs, accurate simulation of the various forms of mass flux is important in oil exploration and optimal oil recovery. Since the diffusion and thermodiffusion coefficients of binary hydrocarbon mixtures have been measured and analyzed in detail elsewhere (Urteaga et al., 2012; Jaber et al., 2009; Kianian et al., 2012), here we experimentally analyzed and reported the separation in a ternary hydrocarbon mixture of tetrahydronaphthalene, isobutylbenzene, and dodecane due to thermal gradients, and we determined the Soret coefficients of this mixture for four different compositions. The thermodiffusion experiment was conducted by means of a Mach–Zehnder Interferometer (MZI) using two wavelengths and in a low gravity environment on board the International Space Station (ISS). Thus, we report the chemical concentration variations of the various cases obtained by the recently developed processing technique. In addition we investigated the reliability and the repeatability of the MZI experiment to study thermodiffusion for ternary mixtures. Finally, according to the transient behavior of the separation of the components, the Soret diffusion coefficients for various compositions of this mixture were measured and then compared.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0894177715003891

Microgravity Science Glovebox (MSG)

by on 2 October 2015in Life Sciences, Physical Sciences

Specifications:

Work Volume (WV)

  • Dimensions
    • W=906 mm x H=637 mm high x D 500 mm (floor), D385 mm (top)
    • 255 liters
    • 406 mm (16”) Diameter Loading Port
  • Four 6” Glove Ports
  • Mounting Mechanisms/Locations
    • Bolt Hole Patterns for M6 threaded fastenener
      • Floor – 70 mm grid
      • Back Wall – 70 mm grid
      • Ceiling – 70 mm grid
      • Loading Port, Inside Edges
    • Set of Threaded Fasteners: 5 each of 5 lengths
    • Velcro Strips: 2 each of 2 lengths
    • Velcro Tabs: 2 each
    • Velcro Cable Ties
    • Bungees

Structural

  • WV provides for the attachment of hardware either by M6 inserts or bungee cords
  • Cold Plate: 24 M6 inserts in a 70 X 70 mm pattern
  • Airlock Top Lid: 18 M6 inserts in a 70 X 70 mm pattern
  • Rear Wall: 20 M6 inserts in a 70 X 70 mm pattern
  • Access Ports: 27 (each) M6 inserts at 10° pitch
  • Ceiling: Two locations containing 8 M6 inserts in a 70 X 70 mm pattern

Airlock

  • 26 liter volume allows access to the WV during operation without compromising
  • Transfer capability while maintaining two levels of containment
  • Max dimensions single piece of equipment: 254 mm X 343 mm X 299 mm
  • Removable Airlock Tray with bungees
  • Single 4” glove port

Air Circulation

  • Max airflow rate of 1200 l/min and a max velocity of 0.044 m/s at the centerline of the work volume
  • Airflow can be varied between 15% and 100% depending on fan speed settings
  • Negative pressures of 1.3 mB to at least 7 mB based on facility settings

Air Filtering

  • Front Filters: 12 in WV, 1 in AL
    • HEPA, Charcoal, Catalyst
    • Liquid Volume Absorption of 50 cc max
  • Particle filtration down to 0.3 micron size
  • Filter Caps
  • Rear Filters
    • Charcoal, Catalyst
  • Life Science Filters

Physical Barrier

  • Gloverings assemblies in sizes 7, 9, & 10 for WV and AL
  • Glove Port Plugs and Glove Blanks for WV and AL
  • LSAH Gloves
  • Feed Through Assemblies

Thermal

  • Total of 1000 W can be dissipated from the WV
  • Allowable heat dissipation to the Cold Plate = 800 W
  • Allowable heat dissipation to the Air = 200 W

Power

  • 120 VDC – 8.3 amps
  • 28 VDC – 7 amps
  • ± 12 VDC – 2 amps for +, 2 amps for –
  • 5 VDC – 4 amps

Vacuum

  • Two vacuum interfaces are provided in the WV
  • Vacuum resource/venting is provided via a 1/2″ quick disconnect
  • Vacuum exhaust/waste is provided via a 1/2″ quick disconnect

GN2

  • One GN2 interface is provided in the WV via 1/4″ quick disconnect

Illumination

  • WV Illumination Units: 1,000 lux @ 200 mm above the WV floor
  • AL Illumination Unit: 323 Lux general lighting
  • Spotlight and Gooseneck
  • Stray Light Covers

Sensors

  • Temperature Sensors
    • Work Volume air temperature
    • Moderate Temperature Loop coolant Cold Plate inlet and outlet temperatures
    • Air Lock air temperature
    • Ambient cabin air temperature
  • Differential Air Pressure Sensors
    • Work Volume Delta P – differential pressure between work volume and cabin
    • Filter Bank Delta P – differential pressure across filter banks, 3 front, 3 rear
    • Air Lock Filter Delta P – differential pressure between air lock and cabin
  • Humidity Sensor
    • One located in each of three filter banks, one in Work Volume, one in Air Lock
  • Gas Sensors detect carbon monoxide
    • One located in each of three filter banks and one located in cabin
  • SAMS-TSH available for setup in Work Volume
    • Vibrational microgravity measurements

Data

  • Two RS-422 connections to MSG Standard Payload Computer for data and commanding
  • Ethernet connections to LAN1 and LAN2 at UIP
  • RS-232 and RS-422 connections to Laptop for data and commanding
  • Laptop provides connectivity to Medium Rate Down Link
  • Experiment Control Board provides analog inputs and digital I/O to SPLC

Video

  • Computer-based digital video system accepts up to four input
  • Four HD-SDI inputs
  • Four GigE inputs
  • Two High Definition video cameras
  • Two GigE video camera
  • User-provided cameras can connect via GigE inputs
  • On-Orbit crew control via ISS laptop
  • Ground command via RS-422
  • Digital video files can be downlinked via ISS Medium Rate Data Link
  • Annotation capability for time, date, text, data
  • Retain capability to downlink via ISS Video

Life Science Ancillary Hardware (LSAH)

  • Filtration System: a capability to scrub typical life science biological and chemical contaminants from the MSG Work Volume air.
  • Exchangeable Glove System: a capability to provide gloves that are suited for various life science activities.
  • Decontamination System: a capability to reduce released biological contaminants (Bio Safety Levels (BSL) 1 and 2) to levels safe for crew exposure and a cleanup capability to remove released contaminants from surfaces within the Work Volume and Air Lock.
  • Rodent Research Support Equipment: a capability to restrain research subjects on an adjustable table and a capability to provide more surface area for temporary storage

Clean Up

  • Dry Wipes
  • Ziplock Bags
  • Filter Cap with adapter hose
  • Particle Catchers (dry particulates)
  • Filter Cartridges (liquids) used with cartridge adapter
  • LSAH Decontamination System
  • LSAH Wipes
  • LSAH Clean Up Kits

Japanese Space Materials Exposure Experiment Utilizing International Space Station

by on 9 June 2015in Physical Sciences No comment

Space environment effects on materials are very severe and complex. It depends on the orbit in which the spacecraft is placed. Especially, in the orbit in which International Space Station (ISS) is operated, the interaction with not only space high energy particle but also the neutral gas, which is the atomic oxygen is dominant, become a problem in its performance. In addition, the surface degradation which is associated with contamination is one of the concerns for optics performance. So, space environment and its effect data is very important for spacecraft design. Space materials exposure experiment is that space materials is exposed in space, retrieved on the ground and analyzed. We can understand the real space environment effects on materials from this experimentsamples. NASA's Long Duration Exposure Facility (LDEF) during its 5 years and 9 months in LEO revealed the micrometeoroid or orbital debris environment from the impacts on its samples. NASDA, the forerunner of JAXA, has implemented the space materials exposure experiment on the space shuttle and ISS. Micro-Particles Capturer (MPAC) and Space Environment Exposure Device (SEED) are the Japanese space materials exposure experiment on ISS. The MPAC is a micrometeoroid capture experiment. The SEED is a passive experiment designed to exposure materials. The SM/MPAC&SEED experiment is one of the first Japanese experiments on the Russian Service Module (SM) of ISS. This experiment had been implemented with cooperation between Russia and Japan. In October 2005, all this samples were retrieved on the ground from ISS by Soyuz-10S and transferred to Japan. I will report the status of the experiment and the preliminary report the retrieved samples. And future experimental plan will be reported.

Related URLs:

Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio

by on 9 June 2015in Physical Sciences No comment

This paper reports the experimental results on the instability and associated roll structures (RSs) of Marangoni convection in liquid bridges formed under the microgravity environment on the International Space Station. The geometry of interest is high aspect ratio (AR = height/diameter ≥ 1.0) liquid bridges of high Prandtl number fluids (Pr = 67 and 207) suspended between coaxial disks heated differentially. The unsteady flow field and associated RSs were revealed with the three-dimensional particle tracking velocimetry. It is found that the flow field after the onset of instability exhibits oscillations with azimuthal mode number m = 1 and associated RSs traveling in the axial direction. The RSs travel in the same direction as the surface flow (co-flow direction) for 1.00 ≤ AR ≤ 1.25 while they travel in the opposite direction (counter-flow direction) for AR ≥ 1.50, thus showing the change of traveling directions with AR. This traveling direction for AR ≥ 1.50 is reversed to the co-flow direction when the temperature difference between the disks is increased to the condition far beyond the critical one. This change of traveling directions is accompanied by the increase of the oscillation frequency. The characteristics of the RSs for AR ≥ 1.50, such as the azimuthal mode of oscillation, the dimensionless oscillation frequency, and the traveling direction, are in reasonable agreement with those of the previous sounding rocket experiment for AR = 2.50 and those of the linear stability analysis of an infinite liquid bridge.

Related URLs:
http://scitation.aip.org/content/aip/journal/pof2/27/2/10.1063/1.4908042

Space experiment on the instability of Marangoni convection in large liquid bridge – MEIS-4: effect of Prandtl number

by on 9 June 2015in Physical Sciences No comment

Microgravity experiments on the thermocapillary convection in liquid bridge, called Marangoni Experiment in Space (MEIS), are carried out in "KIBO" of ISS. Three series of experiments, MEIS-1, 2, and 4, have been conducted so far. This paper reports the results obtained from MEIS-4, in which 20cSt silicone oil ( Pr = 207) is used to generate large liquid bridges. They are suspended between coaxial disks that are 50mm in diameter, with their maximum length equal to 62.5mm. MEIS-4 aims at (1) determining the critical temperature difference for the onset of oscillatory flow; (2) realizing high Marangoni number conditions for high Pr fluid; (3) clarifying the effects of volume ratio, heating rate, hysteresis, and cooled disk temperature; and (4) observing whether the hydrothermal wave with azimuthal mode number m = 0 appears or not. The main results are presented and compared with those obtained in MEIS-1 and 2, which utilized liquid bridges of 5cSt silicone oil ( Pr = 67).

Related URLs:
http://stacks.iop.org/1742-6596/327/i=1/a=012029

3-D PTV measurement of Marangoni convection in liquid bridge in space experiment

by on 9 June 2015in Physical Sciences No comment

Microgravity experiments have been conducted on the International Space Station in order to clarify the transition processes of the Marangoni convection in liquid bridges of high Prandtl number fluid. The use of microgravity allows us to generate large liquid bridges, 30 mm in diameter and up to 60 mm in length. Three-dimensional particle tracking velocimetry (3-D PTV) is used to reveal complex flow patterns that appear after the transition of the flow field to oscillatory states. It is found that a standing-wave oscillation having an azimuthal mode number equal to one appears in the long liquid bridges. For the liquid bridge 45 mm in length, the oscillation of the flow field is observed in a meridional plane of the liquid bridge, and the flow field exhibits the presence of multiple vortical structures traveling from the heated disk toward the cooled disk. Such flow behaviors are shown to be associated with the propagation of surface temperature fluctuations visualized with an IR camera. These results indicate that the oscillation of the flow and temperature field is due to the propagation of the hydrothermal waves. Their characteristics are discussed in comparison with some previous results with long liquid bridges. It is shown that the axial wavelength of the hydrothermal wave observed presently is comparable to the length of the liquid bridge and that this result disagrees with the previous linear stability analysis for an infinitely long liquid bridge.

Related URLs:
http://dx.doi.org/10.1007/s00348-011-1136-9

Growth of an ice disk: dependence of critical thickness for disk instability on supercooling of water

by on 9 June 2015in Physical Sciences No comment

The appearance of an asymmetrical pattern that occurs when a disk crystal of ice grows from supercooled water was studied by using an analysis of growth rates for radius and thickness. The growth of the radius is controlled by transport of latent heat and is calculated by solving the diffusion equation for the temperature field surrounding the disk. The growth of the thickness is governed by the generation and lateral motion of steps and is expressed as a power function of the supercooling at the center of a basal face. Symmetry breaking with respect to the basal face of an ice disk crystal is observed when the thickness reaches a critical value; then one basal face becomes larger than the other and the disk loses its cylindrical shape. Subsequently, morphological instability occurs at the edge of the larger basal face of the asymmetrical shape (Shimada, W.; Furukawa, Y. J. Phys. Chem. 1997, B101, 6171-6173). We show that the critical thickness is related to the critical condition for the stable growth of a basal face. A difference of growth rates between two basal faces is a possible mechanism for the appearance of the asymmetrical shape.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/19275135

Measurements of growth rates of an ice crystal from supercooled heavy water under microgravity conditions: basal face growth rate and tip velocity of a dendrite

by on 9 June 2015in Physical Sciences No comment

The growth of single ice crystals from supercooled heavy water was studied under microgravity conditions in the Japanese Experiment Module ''KIBO'' of the International Space Station (ISS). The velocities of dendrite tips parallel to the a axis and the growth rates of basal faces parallel to the c axis were both analyzed under supercooling ranging from 0.03 to 2.0 K. The velocities of dendrite tips agree with the theory for larger amounts of supercooling when the growth on the basal faces are not zero. At very low supercooling there is no growth on the basal faces. With increasing supercooling the basal faces start to grow, the growth rate changing as a function of supercooling with a power law with an exponent of about 2, with the exponent approaching 1 as supercooling increases further. We interpret the growth on the basal faces as being controlled by two-dimensional nucleation under low supercooling, with a change in the growth kinetics to spiral growth with the aid of screw dislocations with increasing supercooling then to a linear growth law. We discuss the combined effect of tip velocity and basal face kinetics on pattern formation during the growth of ice.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/21631108