Flight Samples Research Articles

Polymerization under Microgravity: Results and Prospects

Frontal photopolymerization of polyacrylamide gel is theoretically and experimentally investigated under conditions of microgravity. With the help of optical methods, the conversion field of monomer is visualized in the course of the experiment, and the pattern of a reaction front motion is determined. The comparison of the properties of flight and laboratory samples of gel allows us to conclude that carrying out polymerization onboard an orbital station in order to obtain homogeneous polymeric materials is promising.

Characterization of zeolites A and X grown in low earth orbit

Crystallization of zeolites A and X carried out in microgravity (J. Warzywoda et al., J. Crystal Growth 220 (2000) 140) indicated that the microgravity-processed crystals had different nucleation and growth histories than their terrestrial controls. Powder and single-crystal X-ray diffraction showed these samples were highly crystalline. Typically, the flight-grown crystals had the higher Si/Al ratios than their terrestrial counterparts (X-ray photoelectron/Auger electron spectroscopy), and electron probe microanalysis showed that these observations continued throughout the crystals. All samples displayed Type I adsorption isotherms, characteristic of materials with a high level of microporosity (BET analysis). The flight samples had smaller surface areas, which is generally attributed to a higher degree of crystalline perfection. For the microgravity-grown crystals the symmetry of the spots by position and intensity around the center of the crystallographic projection, obtained by single-crystal X-ray diffraction, indicated uniform crystal growth. In contrast, their terrestrial counterparts (controls) were characterized by significant differences between the shapes and intensities of characteristic spots for specified families of planes and by variations of the angles ( h 1 k 1 l 1), ( h 2 k 2 l 2) around their literature values. SEM/AFM analysis indicated that the flight crystals had ideal morphologies, and fewer surface defects than their terrestrial controls.

Spaceflight effects on cultured embryonic chick bone cells.

A model calcifying system of primary osteoblast cell cultures derived from normal embryonic chicken calvaria has been flown aboard the shuttle, Endeavour, during the National Aeronautics and Space Administration (NASA) mission STS-59 (April 9-20, 1994) to characterize unloading and other spaceflight effects on the bone cells. Aliquots of cells (approximately 7 x 10(6)) grown in Dulbecco's modified Eagle's medium (DMEM) + 10% fetal bovine serum (FBS) were mixed with microcarrier beads, inoculated into cartridge culture units of artificial hollow fiber capillaries, and carried on the shuttle. To promote cell differentiation, cartridge media were supplemented with 12.5 microg/ml ascorbate and 10 mM beta-glycerophosphate for varying time periods before and during flight. Four cartridges contained cells from 17-day-old embryos grown for 5 days in the presence of ascorbate prior to launch (defined as flight cells committed to the osteoblastic lineage) and four cartridges supported cells from 14-day-old embryos grown for 10 days with ascorbate before launch (uncommitted flight cells). Eight cartridges prepared in the same manner were maintained under normal gravity throughout the flight (control cells) and four additional identical cartridges under normal gravity were terminated on the day of launch (basal cells). From shuttle launch to landing, all cartridges were contained in closed hardware units maintaining 5% CO2, 37 degrees C, and media delivery at a rate of approximately 1.5 ml/6 h. During day 3 and day 5 of flight, duplicate aliquots of conditioned media and accumulated cell products were collected in both the flight and the control hardware units. At the mission end, comparisons among flight, basal, and control samples were made in cell metabolism, gene expression for type I collagen and osteocalcin, and ultrastructure. Both committed and uncommitted flight cells were metabolically active, as measured by glucose uptake and lactate production, at approximately the same statistical levels as control counterparts. Flight cells elaborated a less extensive extracellular matrix, evidenced by a reduced collagen gene expression and collagen protein appearance compared with controls. Osteocalcin was expressed by all cells, a result indicating progressive differentiation of both flight and control osteoblasts, but its message levels also were reduced in flight cells compared with ground samples. This finding suggested that osteoblasts subjected to flight followed a slower progression toward a differentiated function. The summary of data indicates that spaceflight, including microgravity exposure, demonstrably affects bone cells by down-regulating type I collagen and osteocalcin gene expression and thereby inhibiting expression of the osteogenic phenotype notably by committed osteoblasts. The information is important for insight into the response of bone cells to changes of gravity and of force in general.

Microgravity Solidification of Al-In Alloys

Several aluminum-indium alloy samples were directionally solidified under microgravity conditions during the Life and Microgravity Spacelab Mission in 1996. These samples were processed as part of the Coupled Growth in Hypermonotectics flight experiment which is scheduled for completion aboard the International Space Station. The overall objective of this flight experiment is to obtain a fundamental understanding of the physics controlling solidification processes in immiscible alloy systems. Convective instability is anticipated in the Al-In alloys processed due to the low density solute depleted boundary layer that forms in advance of the solidification front. The three samples were processed using the Advanced Gradient Heating Facility and consisted of a 17.3 wt%In monotectic composition sample and two hypermonotectic composition samples, one containing 18.5 wt%In and the other 19.7 wt%In. Post flight analysis revealed the presence of small voids in two of the flight samples which may have had an impact on the ability to maintain steady state growth conditions. Precision density measurements revealed compositional variations along the length of ground processed samples which were representative of results anticipated due to convective mixing in the melt. Flight samples showed an initial compositional variation indicative of minimal mixing in the melt. Interface stability was obtained in one of the hypermonotectic flight samples over a region of the sample. Microstructural comparisons between flight samples indicate the increased volume fraction of the aligned rod-like phase in hypermonotectic samples is accommodated by an increased number of rods in the structure but a minimal change in rod diameter.

Cell growth and organ differentiation in cultured tobacco cells under spaceflight condition.

The responses of cultured tobacco cells to microgravity were examined. Cultured tobacco cells grew and regenerated shoots under microgravity conditions. However, such growth, especially of stems, was much more heterogeneous than that in the ground control, and the increase in fresh weight of the flight samples was less than that of ground control. In addition, multiple shoot formation was not observed in flight samples. Microscopic observation showed that the meristem of regenerating shoot under microgravity was smaller than that in the ground control. Electron microscopy showed that chloroplasts in the ground control were slightly more developed than those in flight samples and extensive arrays of microtubules were more evident in ground control than in flight samples. Analyses of enzymes involved in primary and secondary metabolism indicated that callus grown on shoot regeneration medium under microgravity conditions had a much lower activity of caffeic acid O-methyltransferase, which is involved in lignin biosynthesis, than those grown on Earth. In addition, two-dimensional polyacrylamide-gel electrophoresis analysis of 35S-labeled proteins suggested that gene expression in the flight samples may be similar to that in the ground control.

Diffusion-controlled crystallization apparatus for microgravity (DCAM): flight and ground-based applications

A versatile microdialysis counterdiffusion apparatus was developed in response to special exploratory opportunities for long-duration protein crystal growth experiments presented by the US and Russian Space Program. Challenged to reduce man-tended dependence during this phase, the hardware was designed to eliminate in-flight activation or deactivation. In addition, a disposable interface was incorporated in the design to allow for improved logistics and handling during the pre-flight loading and post-flight distribution of the flight samples for each experiment. The hardware is referred to as the diffusion-controlled crystallization apparatus for microgravity or DCAM (pronounced “dee-cam”) which utilizes the dialysis method and allows the equilibration rate of each individual experiment to be passively controlled from several days to several months. Precision control of the rate of approach to supersaturation has routinely produced macro (5 mm to 1.25 cm) crystals for a variety of proteins in this hardware. A description of the hardware and preliminary results from a series of US Shuttle/Mir flight experiments are presented.

The effects of space flight on the production of monorden by Humicola fuscoatra WC5157 in solid-state fermentation.

The effect of space flight on the production of the antibiotic monorden on two types of agar media, T8 and PG, by Humicola fuscoatra WC5157 was examined on board the US Space Shuttle mission STS-77 in May 1996. Paired space-flight and ground control samples were prepared using identical hardware, protocol, media, and inoculum. Inoculation occurred simultaneously for both groups 2.5 after launch. The flight and ground samples were allowed to grow for the entire 10-day mission in a dark, thermally controlled (22 degrees C) environment. Post-flight HPLC analysis of the flight and ground sample extracts indicated that the production of monorden by H. fuscoatra WC5157 in the flight samples was higher than in the ground samples in both agar media. In the T8 medium, the production of monorden in the flight and ground samples was 11.6 +/- 3.5 micrograms and 8.9 +/- 1.1 micrograms respectively (30% increase). In the PG medium, the production of monorden in the flight and ground samples was 23.8 +/- 3.3 micrograms and 8.2 +/- 2.2 micrograms respectively (190% increase). The production of monorden in the flight and ground control samples was confirmed by HPLC-MS analysis.

Zone Melting of Bi0,5Sb1,5Te3 Crystals under Microgravity

Two samples of the thermoelectrical material Bi0.5Sb1.5Te3 were grown by zone melting technique during a space flight of the russian space station “MIR” in 1994. By comparing the flight samples with the reference ground samples relevant conclusions regarding the influence of different mass transport situations in the melt on micro- and macrosegregation are possible. The samples were analyzed metallographically, by local resolved scanning of the SEEBECK-coefficient and by WDX measurements. Contrary to the ground samples the flight samples showed no convection-induced striations in the bulk. Consequently under microgravity unsteady flow in the melt has been avoided. The axial distribution of the Te component in the flight samples showed an unexpected Pfann-like behaviour, which points to a convection-controlled growth. Contrary to this the axial distribution of the metal components was diffusion-controlled. The axial macrosegregation of tellurium found in the flight samples can be explained by the high sensitivity of components with a low distribution coefficient to weakest convective flows. The radial distribution of the Te component in the flight samples is more homogeneous compared to the ground samples. The explanation of these differences succeeds only partly by the curvature of the interface and by the variation of the Te concentration boundary layer across the interface.

Microgravity Solidification of Immiscible Alloys

AbstractThis paper covers findings obtained from the microgravity directional solidification of immiscible aluminum-indium alloys during the Life and Microgravity Spacelab Mission in 1996. Three alloys, one of monotectic composition and two alloys containing an excess of indium above the monotectic (i.e., hypermonotectic compositions) were solidified using the Advanced Gradient Heating Facility (AGHF). Samples were processed in specialized ampoule assemblies containing pistons and a high temperature spring in a partially successful attempt to prevent void formation due to thermal contraction of the melt and solidification shrinkage. A comparison of compositional variations between microgravity processed and ground processed samples revealed compositional variations along the length of ground processed samples which were representative of results anticipated due to convective mixing in the melt. Flight samples showed an initial compositional variation indicative of minimal mixing in the melt. However, a discontinuity in the microstructure was observed which coincided with the presence of a void in the flight sample.

Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.

Microorganisms and plant of Autonomous Biological Systems (ABS) samples.

Distribution of microorganisms and cellular structure of an Autonomous Biological Systems (ABS) were studied with a special attention to the effect of space environments. Viable cell densities measured by the direct fluorescence microscopic method were in the order of 10(5) cells/ml for fractions 1 (upper suspension) and 2 (lower suspension), and 10(6) cells/ml for fraction 3 (sediments). These values were 10 to 100 times larger than the values obtained by the classical colony forming unit method. No difference between flight and ground samples was observed in the vertical distribution of viable microorganisms when fractionation and analysis were carried out after recovery. Intracellular distribution of chloroplasts in higher green plants, Ceratophyllum demersum, of flight samples was disturbed after 10 days of flight (24hrs/day light on). After 4 months of flight (Mir/STS-79/81) with 24 hrs light on, Ceratophyllum demersum was completely disintegrated. On the other hand, in the second 4-months-flight experiment with 16 hrs/day light on, Ceratophyllum demersum was only slightly deteriorated.

Characterization of Zn-alloyed CdTe compound semiconductors processed in microgravity on USML-1 and USML-2

Three of the four CdZnTe crystals grown on USML-1 and 2 have been analyzed with respect to hydrostatic and buoyant gravitational influences. Characterization was carried out using Synchrotron White Beam X-ray Topography, Fourier Transfer Infrared (FTIR) Spectroscopy and chemical etching. It was found that in the absence of hydrostatic pressure the liquid separated from the ampoule walls, depending on influences such as: volumetric fill-factor, level of constraint, residual g-vector, ampoule geometry and growth conditions. Regions solidified without wall contact were found to be virtually free from twinning, suggesting that these pervasive defects are surface nucleated. Further, these regions showed dramatic reductions in the density of dislocations, from 800,000 (l-g) to 800 (μ-g). This was attributed to thermo-mechanical stress reduction within the flight samples. Regions of partial wall contact showed defect gradients, high on the wall side and low on the free surface side. These results are consistent with our thermo and thermo-mechanical stress model.

Quantification of Early Worcester Porcelain Recipes and the Distinction between Dr Wall- and Flight-period Wares

Compared with Flight period (1783–1793) Worcester porcelain, early (pre-1760) and middle (1760–1774) Dr Wall specimens are depleted in Al2O3, K2O, and enriched in MgO, CaO, Na2O, and, to a lesser extent, PbO. These compositional contrasts reflect secular variations in Worcester recipes, and are manifested, at least in part, by the presence of a potassic phase, apparently a high-temperature alkali feldspar (disordered sanidine) in the Flight samples. Both types of ware contain high- and low-temperature silica polymorphs, and a variably Pb-, Mg-, and Al-bearing, glassy matrix interpreted as fused flint glass frit containing enstatite (±corundum?) crystallites. Even when corrected for enstatite components (and alumina), however, the glassy matrix is not as Pb-rich (i.e. is anomalously silicious) as minimum melt compositions predicted by phase diagrams. This is attributed to the vapourization of lead components during firing or the incomplete separation of silica polymorphs during cooling, but it also may signal the role of dehydration melting reactions (involving talc and/or kaolinite) as well as fusion of the frit in producing the glassy matrix in these wares.Dr Wall recipes contained a higher proportion of talc (∼36–43wt%) and lower proportion of kaolinitic clay (7–10%) than Flight recipes (talc ∼24%; clay ∼17%). Calculated proportions of frit and quartz vary according to the assumed PbO content of the frit used in the recipe, but the amount of lead-rich frit used at Worcester decreased with time. Sagging and crazing was not a problem with Dr Wall wares, so secular recipe changes are likely to have been motivated by aesthetic rather than technical concerns.Insofar as the excavated sherds are representative of Worcester's output, the aluminous and potassic composition of Flight wares, and apparent presence of sanidine, serve to distinguish these wares from Dr Wall porcelains. Analytical data of the type reported here could be used to clarify the relationship between Bristol wares and the earliest products of the Worcester manufactory.

The sea urchin larva, a suitable model for biomineralisation studies in space (IML-2 ESA Biorack experiment ‘24-F urchin’)

By the ESA Biorack T-24 urchin' experiment of the IML-2 mission, for the first time the biomineralisation process in developing sea urchin larvae could be studied under real microgravity conditions. The main objectives were to determine whether in microgravity the process of skeleton formation does occur correctly compared to normal gravity conditions and whether larvae with differentiated skeletons do ‘de-mineralise’. These objectives have been essentially achieved. Postflight studies on the recovered ‘sub-normal’ skeletons focused on qualitative, statistical and quantitative aspects. Clear evidence is obtained that the basic biomineralisation process does actually occur normally in microgravity. No significant differences are observed between flight and ground samples. The sub-normal skeleton architectures indicate, however, that the process of positioning of the skeletogenic cells (determining primarily shape and size of the skeleton) is particularly sensitive to modifications of environmental factors, potentially including gravity. The anatomical heterogenity of the recovered skeletons, interpreted as long term effect of an accidental thermal shock during artificial egg fertilisation (break of climatisation at LSSF), masks possible effects of microgravity. No pronounced demineralisation appears to occur in microgravity; the magnesium component of the skeleton seems yet less stable than the calcium. On the basis of these results, a continuation of biomineralisation studies in space, with the sea urchin larva as model system, appears well justified and desirable.

Effects of Microgravity on Osteoblast Growth Activation

Space flight is an environmental condition where astronauts can lose up to 19% of weight-bearing bone during long duration missions. We used the MC3T3-E1 osteoblast to investigate bone cell growth in microgravity (10−6to 10−9g). Osteoblasts were launched on the STS-56 shuttle flight in a quiescent state with 0.5% fetal calf serum (FCS) medium and growth activation was initiated by adding fresh medium with 10% FCS during microgravity exposure. Four days after serum activation, the cells were fixed before return to normal Earth gravity. Ground controls were treated in parallel with the flight samples in identical equipment. On landing, cell number, cell cytoskeleton, glucose utilization, and prostaglandin synthesis in flight (n= 4) and ground controls (n= 4) were examined. The flown osteoblasts grew slowly in microgravity with total cell number significantly reduced (55 ± 6 vs 141 ± 8 cells per microscopic field). The cytoskeleton of the flight osteoblasts had a reduced number of stress fibers and a unique abnormal morphology. Nuclei in the ground controls were large and round with punctate Hoechst staining of the DNA nucleosomes. The flight nuclei were 30% smaller than the controls (P< 0.0001) and oblong in shape, with fewer punctate areas. Due to their reduced numbers, the cells activated in microgravity used significantly less glucose than ground controls (80.2 ± 0.7 vs 50.3 ± 3.7 mg of glucose/dl remaining in the medium) and had reduced prostaglandin E2(PGE2) synthesis when compared to controls (57.3 ± 17 vs 138.3 ± 41 pmol/ml). Cell viability was normal since, on a per-cell basis, glucose use and prostaglandin synthesis were comparable for flight and ground samples. Taken together, these data suggest that growth activation in microgravity results in reduced growth, causing reduced glucose utilization and reduced prostaglandin synthesis, with significantly altered actin cytoskeleton in osteoblasts.

Peptidase-1 expression in some organs of the salamander Pleurodeles waltl submitted to a 12-day space flight

In Pleurodeles, the peptidase-1 is a sex-linked enzyme encoded by two codominant genes (Pep-1A and Pep-1B) located on the Z and W sex chromosomes. The sexual genotype can be determined by the electrophoretic pattern of the peptidase from erythrocytes. Z AW B genotypic females characterized by 3 electrophoretic bands AA, AB and BB were embarked on Cosmos 2229. The pattern in ovary, muscles and gut issued from the embarked or synchrone females displayed the 3 characteristic bands. In heart and kidney, the bands AA and BB were revealed, while the band BB appeared very fainly. The specific enzymatic activity in the same organs was compared. Except for the kidney, no statistical significant difference was observed between flight and synchrone samples. This enzyme can be efficiently used as sexual genotypic marker of Pleurodeles experimentally submitted to the effects of space environment.

Mini ecosystem in space--preliminary experiment on board STS-77.

An enclosed ecosystem which is stable on Earth will behave differently when brought into space. Micro-gravity and radiation will affect the dynamics of material circulation or the activities of small creatures of the ecosystem. One series of space experiments aiming to address such issues was planned in the United States (It is termed as ABS--Autonomous Biological System) and Japanese group has been involved with cooperating with the analysis of the flight samples. Before the ecosystem will be on board Russian Space Station "Mir" later 1996 for 3 months, a preliminary flight was carried out in May 1996 on Space Shuttle (STS-77) for 10 days flight. It was the first of such experiments to fly one whole ecosystem in space.

Thermal-vacuum response of polymer matrix composites in space

This report describes a thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites. Experimental results derived from 'control' samples are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples. Coefficient of thermal expansion (CTE) data are also presented. In addition, an example is given illustrating the dimensional change of a 'zero' CTE laminate due to moisture outgassing.

Influence of a long duration exposure, 69 months, to the space flight factors in Artemia cysts, tobacco and rice seeds

Three french laboratories have participated in the Free Flyer Biostack experiment. Artemia cysts, tobacco seeds and rice caryopsis and embryos were used. Biological objects in monolayers were dead. In opposite, a large fraction of samples used in bulk survived. A stimulatory effect occurred in the first steps of development in Artemia cysts. In fact, the larval survival was unchanged or slightly reduced. In tobacco a drastic decrease in germination and survival rate was observed. Space flight did not induce genetic changes. In rice, results depend on the variety which was investigated; the growth rate stimulation in flight samples is discussed with respect to controls.

Radiation effects in nematodes: Results from IML-1 experiments

The nematode Caenorhabditis elegans was exposed to natural space radiation using the ESA Biorack facility aboard Spacelab on International Microgravity Laboratory 1, STS-42. For the major experimental objective dormant animals were suspended in buffer or on agar or immobilized next to CR-39 plastic nuclear track detectors to correlate fluence of HZE particles with genetic events. This configuration was used to isolate mutations in a set of 350 essential genes as well as in the unc-22 structural gene. From flight samples 13 mutants in the unc-22 gene were isolated along with 53 lethal mutations from autosomal regions balanced by a translocation eT1 (III;V). Preliminary analysis suggests that mutants from worms correlated with specific cosmic ray tracks may have a higher proportion of rearrangements than those isolated from tube cultures on a randomly sampled basis. Flight sample mutation rate was approximately 8-fold higher than ground controls which exhibited laboratory spontaneous frequencies.