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NASA NTRS2002

Foam Optics and Mechanics

The Foam Optics and Mechanics (FOAM) project will exploit the microgravity environment to more accurately measure the rheological and optical characteristics of wet aqueous foams. Using both rheology and laser light scattering diagnostics, the goal is to quantify the unusual elastic character of foams in terms of their underlying microscopic structure and dynamics. Of particular interest is determining how the elastic character vanishes, i.e., how the foam 'melts' into a simple viscous liquid, as a function of both increasing liquid content and increasing shear strain rate. The unusual elastic character of foams will be quantified macroscopically by measurement of the shear stress as a function of shear strain rate and of time following a step strain. Such data will be analyzed in terms of a yield stress, shear moduli, and dynamical time scales. Microscopic information about bubble packing and rearrangement dynamics, from which the macroscopic non-Newtonian properties ultimately arise, will be obtained non-invasively by multiple-light scattering: diffuse transmission spectroscopy (DTS) and diffusing wave spectroscopy (DWS). Quantitative trends with materials parameters, most importantly average bubble size and liquid content, will be sought in order to elucidate the fundamental connection between the microscopic structure and dynamics and the macroscopic rheology.

Durian, Douglas J.↗

NASA NTRS2005

CRYSTAL-FACE Polarization Lidar Research

The University of Alaska Fairbanks (UAF) Polarization Diversity Lidar (PDL, Sassen 1994) participated in the July 2002 CRYSTAL-FACE field campaign, shortly after the PI moved from the University of Utah to UAF. The truck-mounted PDL is an advanced dual wavelength (1.06 and 0.532 micron), high resolution (0.1-s by 1.5-m), scanning lidar system designed as a testbed for evaluating laser backscatter depolarization techniques for the study of clouds and aerosols in the atmosphere. The main goals identified in our proposal for the CRYSTAL-FACE experiment were, i) the characterization of Florida thunderstorm anvil macrophysical and microphysical properties from lidar backscattering and depolarization, ii) the study of thin to subvisual tropopause-topped subtropical cirrus, iii) the search for indirect cloud effects of trans- Atlantic advected Saharan dust storm aerosols on clouds, and iv) the investigation of melting layer effects on lidar and multi-wavelength Doppler radar measurements in precipitation. Although we experienced adversity in the field during the campaign, sufficient data was collected to begin addressing these topics, and several conference presentations, three journal articles, and one book chapter have resulted from the data analysis effort supported by this grant. (PDL operations were delayed by FAA concerns over the initial sighting at the Kendall-Tamiami Airport, and a brief but major laser breakdown was experienced during the re- setup at the remote Ochopee Everglades site that also supported the N-POL radar.) All lidar data collected by the PDL system were processed and quality checked, and submitted to the CRYSTAL-FACE data archive in a timely manner.

Sassen, Kenneth↗

NASA NTRS1984

High-quality Silicon Films Prepared by Zone-melting Recrystallization

The graphite strip heater zone melting recrystallization (ZMR) technique is described. The material properties of the ZMR films, and SOI device results are reviewed. Although our ZMR work is primarily motivated by integrated circuit applications, this work evolved in part from earlier research on laser crystallization of thick amorphous GaAs and Si films, which was undertaken with the goal of producing low cost photovoltaic materials. The ZMR growth process and its effect on the properties of the recrystallized films may contribute some insight to a general understanding of the rapid recrystallization of Si for solar cells. Adaptation of ZMR for solar cell fabrication is considered.

Chen, C. K.↗

NASA NTRS2011

In Situ Trace Element Measurements on Roda and the Origin of Diogenites

The origin of diogenites remains poorly understood. A recent model interprets many diogenites to have been formed from melts that were derived by remelting initial magma ocean cumulates, and these penultimate parent melts were then contaminated by melts derived from remelting of the basaltic (eucritic) crust to form the ultimate diogenite parent melts [1] (hereafter the remelting model). This is a very complicated petrogenesis that has profound implications for the geological evolution of 4 Vesta if correct. This model was developed based on trace element analyses of bulk rock samples that had been leached in acids to remove phosphates; the compositions of the residues were interpreted to be close to those of cumulus orthopyroxenes plagioclase, chromite and olivine [1]. In situ measurements of phases in diogenites can be used to test this model. We have begun a campaign of laser ablation ICP-MS of orthopyroxene grains in diogenites for this purpose. Here we report our first results on one diogenite, Roda. We have determined a suite of trace lithophile elements on nine, mm-sized pyroxene grains separated from Roda that have previously been studied [2, 3]. A key observation supporting the remelting model is the very low Eu/Eu* of leached residues; values too low to represent orthopyroxene that crystallized from melts with chondritic Sm/Eu and Gd/Eu [1]. (Eu* = Eu interpolated from REE diagrams.) Crustal remelts have low Sm/Eu and Gd/Eu, and orthopyroxenes that crystallized from parent melts contaminated by them would have very low Eu/Eu* [1]. Roda grains have Eu/Eu* of 0.243 to 0.026; the latter a value lower than any measured on bulk diogenite leached residues (0.041) [1]. There is a general negative correlation between Eu/Eu* and some incompatible elements (Zr, Nb, Hf), but not others (LREE). This appears inconsistent with the remelting model as it would suggest an evolving parent melt with La de-creasing as Zr increased and Eu/Eu* decreased. Grain R-15 includes trace-element-rich trapped melt phases [2, 3]. This grain has the highest Eu/Eu* and LREE contents, indicating that the trapped melt had a high Eu/Eu*. Thus, our first data on one diogenite do not provide support for the remelting model [1]. Roda is unusual in that its orthopyroxene grains show wide ranges in trace element contents [4]. Previous in situ REE analyses of grain R-15 did not reveal evidence for subsolidus equilibration with trace-element-rich trapped melt phases, and led to the suggestion that Roda may be polymict, with different grains representing different lithologies of diverse compositions [3]. Thus, based on our results on Roda, it is perhaps premature to abandon the remelting model. In situ measurements on a suite of diogenites is planned to further address this issue.

Mittlefehldt, David W.↗

NASA NTRS2001

Kinetics of Nucleation and Crystal Growth in Glass Forming Melts in Microgravity

This flight definition project has the specific objective of investigating the kinetics of nucleation and crystal growth in high temperature inorganic oxide, glass forming melts in microgravity. It is related to one of our previous NASA projects that was concerned with glass formation for high temperature containerless melts in microgravity. The previous work culminated in two experiments which were conducted aboard the space shuttle in 1983 and 1985 and which consisted of melting (at 1500 C) and cooling levitated 6 to 8 mm diameter spherical samples in a Single Axis Acoustic Levitator (SAAL) furnace. Compared to other types of materials, there have been relatively few experiments, 6 to 8, conducted on inorganic glasses in space. These experiments have been concerned with mass transport (alkali diffusion), containerless melting, critical cooling rate for glass formation, chemical homogeneity, fiber pulling, and crystallization of glass forming melts. One of the most important and consistent findings in all of these experiments has been that the glasses prepared in microgravity are more resistant to crystallization (better glass former) and more chemically homogeneous than equivalent glasses made on Earth (1 g). The chemical composition of the melt appears relatively unimportant since the same general results have been reported for oxide, fluoride and chalcogenide melts. These results for space-processed glasses have important implications, since glasses with a higher resistance to crystallization or higher chemical homogeneity than those attainable on Earth can significantly advance applications in areas such as fiber optics communications, high power laser glasses, and other photonic devices where glasses are the key functional materials.

Day, Delbert E.↗

NASA NTRS2018

Design and Characteristics of Hydroxyapatites: Effect of Radiation

Hydroxyapatites single crystals have been investigated their applications as the laser host material. Czochralksi and flux growth methods have been utilized to achieve single crystals. Because of their bioactivities with tissues these have attracted interest for bone applications. For low temperature processing we have used several techniques. We utilized some organic melt and oriented the grains by the directional solidification method. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano-engineered powders of the material system MgO-Na2O-K2O-CaO-SrO-SiO2 and also borates were processed by sintering and grain growth. Our results indicate that substitution of calcium and strontium with some other elements such as gallium and magnesium have great potential to improve the mechanical properties of bones.

Bhavsar, Jayati↗

NASA NTRS2017

Experimental Hypervelocity Dust Impact in Olivine: FIB/TEM Characterization of Micron-Scale Craters with Comparison to Natural and Laser-Simulated Small-Scale Impact Effects

The space weathering of regoliths on airless bodies and the formation of their exospheres is driven to a large extent by hypervelocity impacts from the high relative flux of micron to sub-micron meteoroids that comprise approximately 90 percent of the solar system meteoroid population. Laboratory hypervelocity impact experiments are crucial for quantifying how these small impact events drive space weathering through target shock, melting and vaporization. Simulating these small scale impacts experimentally is challenging because the natural impactors are both very small and many have velocities above the approximately 8 kilometers-per-second limit attainable by conventional chemical/light gas accelerator technology. Electrostatic "dust" accelerators, such as the one recently developed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS), allow the experimental velocity regime to be extended up to tens of kilometers-per-second. Even at these velocities the region of latent target damage created by each impact, in the form of microcraters or pits, is still only about 0.1 to 10 micrometers in size. Both field-emission analytical scanning electron microscopy (FE-SEM) and advanced field-emission scanning transmission electron microscopy (FE-STEM) are uniquely suited for characterizing the individual dust impact sites in these experiments. In this study, we have used both techniques, along with focused ion beam (FIB) sample preparation, to characterize the micrometer to nanometer scale effects created by accelerated dust impacts into olivine single crystals. To our knowledge this work presents the first TEM-scale characterization of dust impacts into a key solar system silicate mineral using the CCLDAS facility. Our overarching goal for this work is to establish a basis to compare with our previous results on natural dust-impacted lunar olivine and laser-irradiated olivine.

Christoffersen, R.↗

NASA NTRS1988

Laser-heated rotating specimen autoignition test

Specimens of 440 C steel were rotated in a chamber pressurized with oxygen gas and heated with a 5-kW CO2 laser to determine the temperature required for autoignition to occur. Tests included exposures of static and rotating (25,000 rpm) specimens in oxygen pressurized to 5.51 MPa, and with focused laser fluences of more than 3.5 billion W/sq m. Specimen surface temperatures were monitored with a scanning infrared camera. Temperature measurement difficulties were experienced due to a problem with internal reflection inside the test chamber; however, posttest specimen examinations confirmed that surface melt (1371 C) was achieved in several tests. No sustained combustion was initiated in any rotating specimen. One static specimen was ignited. Results indicated that conditions necessary for autoignition of 440 C steel are more dependent on specimen geometry and available heat removal mechanisms. Sustained combustion occurred in the ignited static specimen with an estimated 130 C/sec cooling rate due to conduction. The rotating specimens could not sustain combustion due to a greater conductive/convective cooling rate of about 4000 C/sec and ejection of molten material. These results were applied to the Space Shuttle Main Engine (SSME) oxygen turbopump bearings to conclude that the LOX-cooled 440 C steel bearings cannot sustain combustion initiated by skidding friction.

Au, A. C.↗

NASA NTRS1986

Physics of Fusion Welding

Applicabilities and limitations of three techniques analyzed. NASA technical memorandum discusses physics of electron-beam, gas/ tungsten-arc, and laser-beam welding. From comparison of capabilities and limitations of each technique with regard to various welding conditions and materials, possible to develop criteria for selecting best welding technique in specific application. All three techniques classified as fusion welding; small volume of workpiece melted by intense heat source. Heat source moved along seam, leaving in wake solid metal that joins seam edges together.

Nunes, A. C., Jr.↗

NASA NTRS1982

Electro Processing Research

Electroprocessing which is concerned with fluid dynamics of the electroreduction process to determine how it may be modified to improve the quality of the deposit was studied. Experimental techniques are used in this research. These techniques include laser Schlieren photography, laser Doppler velocimetry, and frequency spectrum analysis. Projects involve fluid flow studies of zinc plating in aqueous and molten salt electrolytes, study of cell design for magnesium chlorides electrolysis, digital signal analysis of manganese electrodeposition in molten chlorides, and electroplating of molybdenum from low melting salts. It is anticipated that the use of refractory metals as constructed materials in engineering will increase. Their electrodeposition from molten salt electrolytes is important in the extraction metallurgy of refractory metals.

Source record↗

NASA NTRS1990

The NASA high temperature superconductivity program

It has been recognized from the onset that high temperature superconductivity held great promise for major advances across a broad range of NASA interests. The current effort is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAIO produced far superior RF characteristics when compared to metallic films on the same substrate. This achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high Q filters. Melt texturing and melt quenched techniques are being used to produce bulk materials with optimized magnetic properties. These yttrium enriched materials possess enhanced flux pinning characteristics and will lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies are being conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magneto-plasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar and Mars mission applications. The project direction and level of effort of the program are also described.

Sokoloski, Martin M.↗

NASA NTRS2010

In Situ Determination of Siderophile Trace Elements in Metals and Sulfides in Enstatite Achondrites

Enstatite meteorites are identified by their extremely reduced mineralogy (1) and similar oxygen isotope composition (2). The enstatite meteorite clan incorporates both EH and EL chondrites, as well as a wide variety of enstatite achondrites, such as aubrites or anomalous enstatite meteorites (e.g. Mt. Egerton, Shallowater, Zaklodzie, NWA 2526). The role of nebular versus planetary processes in the formation of enstatite meteorites is still under debate (e.g. 3-5). Past studies showed a significant influence of metal segregation in the formation of enstatite achondrites. Casanova et al. (6) suggested incomplete metal-silicate segregation during core formation and attributed the unfractionated siderophile element patterns in aubrites metals to a lack of fractional crystallization in a planetary core. Recent studies suggest a significant role of impact melting in the formation of primitive enstatite chondrites (7) and identified NWA 2526 as a partial melt residue of an enstatite chondrite (8). To understand the nature of siderophile element-bearing phases in enstatite achondrites, establish links between enstatite achondrites and enstatite chondrites (9), and constrain planetary differentiation on their respective parent bodies and their petrogenetic histories, we present laser ablation ICP-MS measurements of metal and sulfide phases in Shallowater, Mt. Egerton, and the aubrites Aubres, Cumberland Falls, and Mayo Belwa.

vanAcken, D.↗

NASA NTRS2014

In Situ Trace Element Analysis of an Allende Type B1 CAI: EK-459-5-1

Variations in refractory major and trace element composition of calcium, aluminum-rich inclusions (CAIs) provide constraints on physical and chemical conditions and processes in the earliest stages of the Solar System. Previous work indicates that CAIs have experienced complex histories involving, in many cases, multiple episodes of condensation, evaporation, and partial melting. We have analyzed major and trace element abundances in two core to rim transects of the melilite mantle as well as interior major phases of a Type B1 CAI (EK-459-5-1) from Allende by electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate the behavior of key trace elements with a primary focus on the REEs Tm and Yb.

Jeffcoat, C. R.↗

NASA NTRS1991

Prospects and progress of high Tc superconductivity for space applications

Current research in the area of high temperature superconductivity is organized around four key areas: communications and data, sensors and cryogenics, propulsion and power, and space materials technology. Recently, laser ablated YBa2Cu3O(7-x) films on LaAlO3 produced far superior RF characteristics when compared to metallic films on the same substrate. The achievement has enabled a number of unique microwave device applications, such as low insertion loss phase shifters and high-Q filters. Melt texturing and melt-quenched techniques are being used to produce bulk material with optimized magnetic properties. These yttrium-enriched materials possess enhanced flux pinning characteristics and could lead to prototype cryocooler bearings. Significant progress has also occurred in bolometer and current lead technology. Studies were conducted to evaluate the effect of high temperature superconducting materials on the performance and life of high power magnetoplasma-dynamic thrusters. Extended studies were also performed to evaluate the benefit of superconducting magnetic energy storage for LEO space station, lunar, and Mars mission applications.

Romanofsky, Robert R.↗

NASA NTRS1993

Preliminary Ar-40/Ar-39 age spectrum and laser probe dating of the M1 core of the Manson Impact Structure, Iowa: A K-T boundary crater candidate

Preliminary Ar-40/Ar-39 age spectrum and laser probe dating results from new drill core from the 35-km-diameter Manson Impact Structure (MIS), Iowa indicates a reasonable possibility that the MIS is a Cretaceous-Tertiary (K-T) boundary impact event. Several different types of samples from a melt-matrix breccia, a unit of apparent crater fill intersected by the M1 core, were analyzed. Ar-40/Ar-39 results from these samples indicate a maximum age for the MIS of about 65.4 plus or minus 0.4(2 sigma) Ma. Petrographic analyses of the samples indicate a high probability that all the dated samples from the melt-matrix breccia contain relict grains that were not entirely melted or degassed at the time of impact, suggesting that the actual age of the MIS could be somewhat younger than our preliminary results indicate. The results are consistent with a previously published age estimate of shocked microcline from the MIS central uplift of 65.7 plus or minus 1.0 Ma.

Kunk, M. J.↗

NASA NTRS2018

Effect of Radiation on Biologically Active Glasses

Multifunctional hydroxyapatites single crystals have been studied for their applications as the laser host material since past several decades. It is only recently their potential has been evaluated for bioactive materials. In the past researches, Czochralski and flux growth methods have been utilized to achieve single crystals. We have used low temperature processing techniques for synthesis. Organic melt was used to achieve oriented fibers by the directional solidification method. This organic treated material has different characteristics than coarsened oxide materials. Our approach involved low temperature processing using nano engineered powders of the material system Na2O-K2O-CaO- MgO-SrO-SiO2. Also, borates were processed by sintering and grain growth. Effect of -ray was studied by measuring the electrical characteristics of radiated samples. Our experiments to further improve mechanical characteristics indicate that substitution of calcium with some other elements such as gallium have great potential to improve the radiation hardening and mechanical properties of bones.

Tufail, Areeba↗

NASA NTRS2010

Changes in the Mass Balance of the Greenland Ice Sheet in a Warming Climate During 2003-2009

Mass changes of the Greenland ice sheet (GIS) derived from ICESat and GRACE data both show that the net mass loss from GIS during 2003-2009 is about 175 Gt/year, which contributes 0.5mm/yr global sea-level rise. The rate of mass loss has increased significantly since the 1990's when the GIS was close to mass balance. Even though the GIS was close to mass balance during the 1990's, it was already showing characteristics of responding to8 warmer climate, specifically thinning at the margins and thickening inland at higher elevations. During 2003-2009, increased ice thinning due to increases in melting and acceleration of outlet glaciers began to strongly exceed the inland thickening from increases in accumulation. Over the entire GIS, the mass loss between the two periods, from increased melting and ice dynamics, increased by about 190 Gt/year while the mass gain, from increased precipitation and accumulation, increased by only about 15Gt/year. These ice changes occurred during a time when the temperature on GIS changed at rate of about 2K/decade. The distribution of elevation and mass changes derived from ICESat have high spatial resolution showing details over outlet glaciers, by drainage systems, and by elevation. However, information on the seasonal cycle of changes from ICESat data is limited, because the ICESat lasers were only operated during two to three campaigns per year of about 35 days duration each. In contrast, the temporal resolution of GRACE data, provided by the continuous data collection, is much better showing details of the seasonal cycle and the inter-annual variability. The differing sensitivity of the ICESat altimetry and the GRACE gravity methods to motion of the underlying bedrock from glacial isostatic adjustment (GIA) is used to evaluate the GIA corrections provided by models. The two data types are also combined to make estimates of the partitioning of the mass gains and losses among accumulation, melting, and ice discharge from outlet glaciers.

Zwally, H. Jay↗

NASA NTRS1999

Radar Interferometry Studies of the Mass Balance of Polar Ice Sheets

The objectives of this work are to determine the current state of mass balance of the Greenland and Antarctic Ice Sheets. Our approach combines different techniques, which include satellite synthetic-aperture radar interferometry (InSAR), radar and laser altimetry, radar ice sounding, and finite-element modeling. In Greenland, we found that 3.5 times more ice flows out of the northern part of the Greenland Ice Sheet than previously accounted for. The discrepancy between current and past estimates is explained by extensive basal melting of the glacier floating sections in the proximity of the grounding line where the glacier detaches from its bed and becomes afloat in the ocean. The inferred basal melt rates are very large, which means that the glaciers are very sensitive to changes in ocean conditions. Currently, it appears that the northern Greenland glaciers discharge more ice than is being accumulated in the deep interior, and hence are thinning. Studies of temporal changes in grounding line position using InSAR confirm the state of retreat of northern glaciers and suggest that thinning is concentrated at the lower elevations. Ongoing work along the coast of East Greenland reveals an even larger mass deficit for eastern Greenland glaciers, with thinning affecting the deep interior of the ice sheet. In Antarctica, we found that glaciers flowing into a large ice shelf system, such as the Ronne Ice Shelf in the Weddell Sea, exhibit an ice discharge in remarkable agreement with mass accumulation in the interior, and the glacier grounding line positions do not migrate with time. Glaciers flowing rapidly into the Amudsen Sea, unrestrained by a major ice shelf, are in contrast discharging more ice than required to maintain a state of mass balance and are thinning quite rapidly near the coast. The grounding line of Pine Island glacier (see diagram) retreated 5 km in 4 years, which corresponds to a glacier thinning rate of 3.5 m/yr. Mass imbalance is even more negative on Thwaites Glacier. This sector of West Antarctica probably initiated its collapse decades or centuries ago, once the embaying ice shelves in front of them started to melt because of enhanced basal melting from warmer ocean waters. Additional information is contained in the original.

Rignot, Eric↗