« Go Back

Research Containing: Space Flight

Microgravity Phase Separation Near the Critical Point in Attractive Colloids

by on 9 June 2015in Physical Sciences No comment

We investigate the phase behavior of mixtures of colloids and polymers near their critical point in a microgravity environment. Astronauts onboard the International Space Station (ISS) are using photography to record the rate of phase separation of six samples near the liquid-gas critical point. These photographs are taken both by an automated photograpy system (based on EarthKAM hardware and software) and manually by the astronuats who have setup the experiment. We have obtained high-quality photographs of processes that are not observable on Earth, since both sedimentation and convection are negligible onboard the International Space Station. Interestingly, we observe that gravity does not affect the onset of phase separation in colloid-polymer mixtures near the liquid-gas critical point: samples which phase separate on earth also do so onboard the ISS. However, the rates at which this phase separation occurs is affected by several orders of magnitude by gravity, suggesting future avenues for exploration. The understanding of this system is important for both practical earth-bound applications, as well as the development of products and materials that are stable and function over long periods of time in a low-gravity environment. Thus, our results may assist the long-term spaceflight required for proposed exploration missions to the moon and to Mars.

Related URLs:
http://dx.doi.org/10.2514/6.2007-1152

Neutron dose study with bubble detectors aboard the International Space Station as part of the Matroshka-R experiment

by on 9 June 2015in Physical Sciences No comment

As part of the Matroshka-R experiments, a spherical phantom and space bubble detectors (SBDs) were used on board the International Space Station to characterise the neutron radiation field. Seven experimental sessions with SBDs were carried out during expeditions ISS-13, ISS-14 and ISS-15. The detectors were positioned at various places throughout the Space Station, in order to determine dose variations with location and on/in the phantom in order to establish the relationship between the neutron dose measured externally to the body and the dose received internally. Experimental data on/in the phantom and at different locations are presented.

Related URLs:
http://rpd.oxfordjournals.org/content/133/4/200.abstract
http://rpd.oxfordjournals.org/content/133/4/200

Variation of absorbed doses onboard of ISS Russian Service Module as measured with passive detectors

by on 9 June 2015in Physical Sciences No comment

Cosmic radiation represents possible risk for the astronauts. For estimation of the radiation onboard the spacecraft in space flights, it is necessary to obtain the data on dose distribution in real space flight conditions. This contribution deals with the study of absorbed dose and dose equivalent due to space radiation in different compartments of the International Space Station (ISS) using passive detectors. Luminescent detectors (LD) and CR-39 plastic nuclear track detectors (PNTD) were exposed onboard of Russian Service Module on ISS from August 2004 to October 2005 (425 days); they were placed at SPD boxes and positioned at 6 various locations inside the Russian Service Module. LD were used to measure absorbed doses, particularly from low-LET particles and photons, PNTDs were used to measure the spectra of linear energy transfer (LET), absorbed dose, and dose equivalents from particles with LET∞H2O >5 keV/μm. Results from both types of detectors (LD and PNTD) were then combined together to obtain total values of absorbed doses and dose equivalents. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of registered particle fluxes, are presented as the function of position of SPD boxes (shielding thickness). Also the influence of position of detectors inside the SPD boxes (top and bottom wall) will be discussed. The dose characteristics depend on the location inside the Service Module; their variation has been observed to be up to factor of almost 2.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S1350448709002510

Dose distribution in the depth of the tissue-equivalent ball phantom modeling location of human body critical organs inside the compartments of the International space station

by on 9 June 2015in Physical Sciences No comment

Goal of the investigation is to study and to analyze radiation dose distribution in cosmonaut's body during long-term mission aboard the International space station (ISS). The established patterns of dose distribution under different conditions of the experiment allow simplify evaluation of dose accumulation by spacecrew. Dose from ionizing space radiation was determined with the help of thermoluminescent dosimeters mounted in conditional depths of critical organs in human body modeled in a dosimetric device, i.e.–a ball-like tissue-equivalent phantom designed and manufactured in Russia for international space experiment Matreshka-R. The article reports experimental data disclosing the character and levels of exposure to ionizing radiation inside the Service module crew quarters during ISS missions 8 and 9 (425 days, 2004-2005) and the docking compartment (SO1) during ISS missions 15 and 16 (285 days, 2007-2008).

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/20120916

Droplet Combustion Experiments Aboard the International Space Station

by on 9 June 2015in Physical Sciences No comment

This paper summarizes the first results from isolated droplet combustion experiments performed on the International Space Station (ISS). The long durations of microgravity provided in the ISS enable the measurement of droplet and flame histories over an unprecedented range of conditions. The first experiments were with heptane and methanol as fuels, initial droplet droplet diameters between 1.5 and 5.0 m m, ambient oxygen mole fractions between 0.1 and 0.4, ambient pressures between 0.7 and 3.0 a t m and ambient environments containing oxygen and nitrogen diluted with both carbon dioxide and helium. The experiments show both radiative and diffusive extinction. For both fuels, the flames exhibited pre-extinction flame oscillations during radiative extinction with a frequency of approximately 1 H z. The results revealed that as the ambient oxygen mole fraction was reduced, the diffusive-extinction droplet diameter increased and the radiative-extinction droplet diameter decreased. In between these two limiting extinction conditions, quasi-steady combustion was observed. Another important measurement that is related to spacecraft fire safety is the limiting oxygen index (LOI), the oxygen concentration below which quasi-steady combustion cannot be supported. This is also the ambient oxygen mole fraction for which the radiative and diffusive extinction diameters become equal. For oxygen/nitrogen mixtures, the LOI is 0.12 and 0.15 for methanol and heptane, respectively. The LOI increases to approximately 0.14 (0.14 O 2/0.56 N 2/0.30 C O 2) and 0.17 (0.17 O 2/0.63 N 2/0.20 C O 2) for methanol and heptane, respectively, for ambient environments that simulated dispersing an inert-gas suppressant (carbon dioxide) into a nominally air (1.0 a t m) ambient environment. The LOI is approximately 0.14 and 0.15 for methanol and heptane, respectively, when helium is dispersed into air at 1 atm. The experiments also showed unique burning behavior for large heptane droplets. After the visible hot flame radiatively extinguished around a large heptane droplet, the droplet continued to burn with a cool flame. This phenomena was observed repeatably over a wide range of ambient conditions. These cool flames were invisible to the experiment imaging system but their behavior was inferred by the sustained quasi-steady burning after visible flame extinction. Verification of this new burning regime was established by both theoretical and numerical analysis of the experimental results. These innovative experiments have provided a wealth of new data for improving the understanding of droplet combustion and related aspects of fire safety, as well as offering important measurements that can be used to test sophisticated evolving computational models and theories of droplet combustion.

Related URLs:
http://dx.doi.org/10.1007/s12217-014-9372-2

Fluid Merging Viscosity Measurement (FMVM) Experiment on the International Space Station

by on 9 June 2015in Physical Sciences No comment

The concept of using low gravity experimental data together with fluid dynamical numerical simulations for measuring the viscosity of highly viscous liquids was recently validated on the International Space Station (ISS). After testing the proof of concept for this method with parabolic flight experiments, an ISS experiment was proposed and later conducted onboard the ISS in July, 2004 and subsequently in May of 2005. In that experiment a series of two liquid drops were brought manually together until they touched and then were allowed to merge under the action of capillary forces alone. The merging process was recorded visually in order to measure the contact radius speed as the merging proceeded. Several liquids were tested and for each liquid several drop diameters were used. It has been shown that when the coefficient of surface tension for the liquid is known, the contact radius speed can then determine the coefficient of viscosity for that liquid. The viscosity is determined by fitting the experimental speed to theoretically calculated contact radius speed for the same experimental parameters. Experimental and numerical results will be presented in which the viscosity of different highly viscous liquids were determined, to a high degree of accuracy, using this technique.

Related URLs:
http://dx.doi.org/10.2514/6.2007-1151

Austrian dose measurements onboard space station MIR and the International Space Station – overview and comparison

by on 9 June 2015in Physical Sciences No comment

The Atominstitute of the Austrian Universities has conducted various space research missions in the last 12 years in cooperation with the Institute for Biomedical Problems in Moscow. They dealt with the exact determination of the radiation hazards for cosmonauts and the development of precise measurement devices. Special emphasis will be laid on the last experiment on space station MIR the goal of which was the determination of the depth distribution of absorbed dose and dose equivalent in a water filled Phantom. The first results from dose measurements onboard the International Space Station (ISS) will also be discussed. The spherical Phantom with a diameter of 35 cm was developed at the Institute for Biomedical Problems and had 4 channels where dosemeters can be exposed in different depths. The exposure period covered the timeframe from May 1997 to February 1999. Thermoluminescent dosemeters (TLDs) were exposed inside the Phantom, either parallel or perpendicular to the hull of the spacecraft. For the evaluation of the linear energy transfer (LET), the high temperature ratio (HTR) method was applied. Based on this method a mean quality factor and, subsequently, the dose equivalent is calculated according to the Q(LET∞) relationship proposed in ICRP 26. An increased contribution of neutrons could be detected inside the Phantom. However the total dose equivalent did not increase over the depth of the Phantom. As the first Austrian measurements on the ISS dosemeter packages were exposed for 248 days, starting in February 2001 at six different locations onboard the ISS. The Austrian dosemeter sets for this first exposure on the ISS contained five different kinds of passive thermoluminescent dosemeters. First results showed a position dependent absorbed dose rate at the ISS.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0273117704003278

The Constrained Vapor Bubble (CVB) Experiment in the Microgravity Environment of the International Space Station

by on 9 June 2015in Physical Sciences No comment

The Constrained Vapor Bubble (CVB) experiment was run in the microgravity environment of the International Space Station as part of the Increment 23-24 which ended in September 2010. Here we present preliminary results which indicate significant differences in the operation of the CVB heat pipe in the micro-gravity environment as compared to the Earth's gravity. The temperature profile data along the heat pipe indicate that the heat pipe behavior is affected favorably by increased capillary flow and adversely by the absence of convective heat transfer as a heat loss mechanism. Image data of the liquid profile in the grooves of the heat pipe indicate that the curvature gradient is considerably different from that on Earth. An initial discussion of the data collected is presented.

Related URLs:

Radiation measurements on the International Space Station

by on 9 June 2015in Physical Sciences No comment

The International Space Station (ISS) is becoming a reality with the docking of the Russian Service module (Zarya) with the Unity module (Zaveda). ISS will be in a nominal 51.65-degree inclination by 400 km orbit. This paper reviews the currently planned radiation measurements, which are in many instances, based on experiments previously flown on the Space Shuttle. Results to be expected based on Shuttle measurements are presented.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/11780621

Survival of plant seeds, their UV screens, and nptII DNA for 18 months outside the International Space Station

by on 9 June 2015in Education No comment

The plausibility that life was imported to Earth from elsewhere can be tested by subjecting life-forms to space travel. Ultraviolet light is the major liability in short-term exposures (Horneck et al., 2001 ), and plant seeds, tardigrades, and lichens-but not microorganisms and their spores-are candidates for long-term survival (Anikeeva et al., 1990 ; Sancho et al., 2007 ; Jonsson et al., 2008 ; de la Torre et al., 2010 ). In the present study, plant seeds germinated after 1.5 years of exposure to solar UV, solar and galactic cosmic radiation, temperature fluctuations, and space vacuum outside the International Space Station. Of the 2100 exposed wild-type Arabidopsis thaliana and Nicotiana tabacum (tobacco) seeds, 23% produced viable plants after return to Earth. Survival was lower in the Arabidopsis Wassilewskija ecotype and in mutants (tt4-8 and fah1-2) lacking UV screens. The highest survival occurred in tobacco (44%). Germination was delayed in seeds shielded from solar light, yet full survival was attained, which indicates that longer space travel would be possible for seeds embedded in an opaque matrix. We conclude that a naked, seed-like entity could have survived exposure to solar UV radiation during a hypothetical transfer from Mars to Earth. Chemical samples of seed flavonoid UV screens were degraded by UV, but their overall capacity to absorb UV was retained. Naked DNA encoding the nptII gene (kanamycin resistance) was also degraded by UV. A fragment, however, was detected by the polymerase chain reaction, and the gene survived in space when protected from UV. Even if seeds do not survive, components (e.g., their DNA) might survive transfer over cosmic distances.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/22680697