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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

The Interaction of Positively-charged Ions with Nucleic Acid Systems

The successful development of extremely low background sample cells for x-ray scattering studies has enabled experiments designed to elucidate some of the fundamental physical interactions involved in macromolecular folding. Microfabrication techniques were used to fabricate low volume (50 micro-liter) sample cells with silicon nitride membranes (sub micron in thickness) as x-ray windows. Scientifically, these studies focus on the interaction of negatively charged nucleic acid systems, RNA and DNA, with their surrounding (positively charged) ion atmospheres. Understanding the structure of the ion atmosphere and its influence on the shape/conformation of the macromolecule will help reveal the underlying physical forces employed by nature in the self-assembly of these important molecules.

Pollack, Lois↗
NASA NTRSDate not supplied

Measuring the Wear and Abrasive Resistance of Air Plasma Sprayed Aluminum Oxide for Lunar Exploration

Lunar regolith, especially finer dust particles traveling at high velocities, can cause significant wear and abrasive damage to structural components that ensure a prolongated presence on the surface of the Moon. With the absence of an atmosphere and lower gravity than on Earth, regolith particles maintain high velocities at large distances from where they were generated, for example next to lunar landers. Wear-resistant ceramic and ceramic composite materials can improve the durability of spacecraft components during long missions on the Moon’s surface. Aluminum oxide coatings are lightweight, have multifunctional properties, and have high strength including high hardness and wear resistance. These properties can help improve the durability of structures used in space exploration. Air plasma sprayed (APS) aluminum oxide coatings have demonstrated the potential to protect critical structures. This study investigated the abrasive wear resistance of APS aluminum oxide coatings via Taber abrasion experiments. Taber abrasion offers the advantage of quantifying the abrasive wear behavior of particles with different shapes on a surface. In this work, an abrasive wheel made of silicon carbide was utilized to evaluate wear properties of specimens progressively over 5000 cycles. This experiment focused on testing two series of specimens to determine whether a bond coat composed of nickel, chromium, aluminum, and yttrium (NiCrAlY) improved the protective behavior of the APS aluminum oxide coating. The specimens varied in topcoat thickness and were made with and without an approximately 100 µm bond coat layer. The mass of the specimens was measured at 400 cycles, 800 cycles, 3800 cycles, and 5000 cycles. Increasing thickness was found to result in higher wear for samples with and without a bond coat. Increased mass loss in samples with a bond coat was observed indicating a need for further studies on the overall impact of the use of a bond coat on the protective behavior of the coatings. To continue designing wear resistant coatings for structural protection in space missions, the multifunctional properties of the APS aluminum oxide coating will be studied. Future experiments will determine whether the APS aluminum oxide coating can protect the structures from other aspects of the harsh space environment, such as extreme temperature variations and ionizing radiation.

aluminum oxide↗
NASA NTRS1995

A determination of the thick disk chemical abundance distribution: Implications for galaxy evolution

We present a determination of the thick disk iron abundance distribution obtained from an in situ sample of F/G stars. These stars are faint, 15 less than or approximately = V less than or approximately = 18, selected on the basis of color, being a subset of the larger survey of Gilmore and Wyse designed to determine the properties of the stellar populations several kiloparsecs from the Sun. The fields studied in the present paper probe the iron abundance distribution of the stellar populations of the galaxy at 500-3000 pc above the plane, at the solar Galactocentric distance. The derived chemical abundance distributions are consistent with no metallicity gradients in the thick disk over this range of vertical distance, and with an iron abundance distribution for the thick disk that has a peak at -0.7 dex. The lack of a vertical gradient argues against slow, dissipational settling as a mechanism for the formation of the thick disk. The photometric and metallicity data support a turn-off of the thick disk that is comparable in age to the metal-rich globular clusters, or greater than or approximately = 12 Gyr, and are consistent with a spread to older ages.

Gilmore, Gerard↗
NASA NTRS2017

Metabolomic and Genomic Markers of Atherosclerosis as Related to Oxidative Stress, Inflammation, and Vascular Function in Twin Astronauts

BACKGROUND: Future human space travel will consist primarily of long-duration missions onboard the International Space Station (ISS) or exploration-class missions to Mars, its moons, or nearby asteroids. Astronauts participating in long-duration missions may be at an increased risk of oxidative stress and inflammatory damage due to radiation, psychological stress, altered physical activity, nutritional insufficiency, and hyperoxia during extravehicular activity. By studying one identical twin during his 1-year ISS mission and his ground-based twin, this work extends a current NASA-funded investigation to determine whether these spaceflight factors contribute to an accelerated progression of atherosclerosis. This study of twins affords a unique opportunity to examine spaceflight-related atherosclerosis risk that is independent of the confounding factors associated with different genotypes. PURPOSE: The purpose of this investigation was to determine whether biomarkers of oxidative and inflammatory stress are elevated during and after long-duration spaceflight and determine if a relation exists between levels of these biomarkers and structural and functional indices of atherosclerotic risk measured in the carotid and brachial arteries. These physiological and biochemical data will be extended by using an exploratory approach to investigate the relationship between intermediate phenotypes and risk factors for atherosclerosis and the metabolomic signature from plasma and urine samples. Since metabolites are often the indirect products of gene expression, we simultaneously assessed gene expression and DNA methylation in leukocytes. HYPOTHESIS: We predict that, compared to the ground-based twin, the space-flown twin will experience elevated biomarkers of oxidative stress and inflammatory damage, altered arterial structure and function, accelerated telomere shortening, dysregulation of genes associated with oxidative stress and inflammation, and a metabolic profile shift that is associated with elevated atherosclerosis risk factors. METHODS: In the space-flown twin, a panel of biomarkers of oxidative and inflammatory stress were measured in venous blood samples and in 24-h (in-flight) and 48-h (pre- and post-flight) urine pools collected twice before flight, six times during the mission (~FD15, 75, 180, 240, 300, 335), and early in the post-flight recovery phase (3-5 days after landing). We also measured metabolomic (targeted and untargeted approaches) and genomic markers (DNA methylation, mRNA gene expression, telomere length) in these samples. Arterial structure, assessed from measures of intima-media thickness, also were measured using standard clinical ultrasound at the same time points. Arterial function was assessed using brachial flow-mediated dilation, a well-validated measure used to assess endothelium-dependent vasodilation and a sensitive predictor of atherosclerotic risk, only before and after spaceflight. All of the same measures were obtained in the ground-based twin, but less frequently. DISCUSSION: All data collection has been completed for both the space-flown twin and the ground-based twin. Vascular structure and function measures have been analyzed, blood and urine samples have been batch-processed. Results from these individuals will be compared to each other, to data from other Twin Study investigations, and to the larger complement of subjects participating in the companion study currently ongoing in ISS astronauts.

Lee, Stuart M. C.↗
NASA NTRS2018

Developing a Novel Platform for Characterizing Thermoelectric Materials for Uncooled Detectors for Land Imaging Applications

Thermal land imaging (imaging at ~8-14 micron optical wavelength) is an essential tool for understanding and managing terrestrial freshwater resources. Current thermal imaging instruments employ low temperature detectors, which require cryocoolers. Consequently, cost-saving reductions in size, weight, and power can be achieved by employing uncooled detectors. One uncooled detector concept, which NASA is pursuing, is a thermopile detector with sub-micron thick doped-Si thermoelectric materials. In order to characterize the thermoelectric properties of the doped silicon, we designed and optimized a novel apparatus. This simple apparatus measures the Seebeck coefficient with thermally isolated stages and LABVIEW automation. We optimized thermal stability using PID tuning and optimized the thermal contact between the thin film samples and stages using electrically conductive springs. Utilizing our apparatus, we measured the Seebeck coefficient of 0.45 micron thick phosphorus-doped single crystal Si samples bonded to alumina substrates. Using these Seebeck coefficient measurements and four-wire electrical resistivity measurements, we determined the relationship between the thermoelectric figure of merit and dopant concentration. These characterization results for doped-Si will guide our thermopile detector design to provide an optimal and competitive detector alternative for future thermal imaging instruments.

Reid, Riley A.↗
NASA NTRS1993

Magneto-optic superlattice thin films: Fabrication, structural and magnetic characterization

During this quarter studies were extended to determine the electronic contribution to the perpendicular interface anisotropy in Co-based multilayers. Using in situ Kerr effect measurements, the influences of different transition metals (TM = Ag, Au, Cu, and Pd) on the magnetic properties of single-crystal Co films grown on Pd (111) and Au (111) surfaces are investigated. Last quarter the discovery of a large peak in the perpendicular anisotropy when approximately one monolayer of Cu or Ag is deposited on the Co surface was reported. We now have added a computer-controlled stepper-motor drive to our MBE sample transfer mechanism. The motor allows us to move the sample at a constant velocity from behind a shutter during deposition. The film, therefore, is deposited as a wedge with a linear variation of thickness across the substrate. In this way, a continuous range of coverage on a single sample is studied. The stepper motor also provides the necessary control for precisely positioning the sample in the laser beam for Kerr effect measurements at the different coverages.

Falco, C. M.↗
NASA NTRS2003

Radiation Transport Properties of Polyethylene-Fiber Composites

Composite materials that can both serve as effective shielding materials against cosmic-ray and energetic solar particles in deep space as well as structural materials for habitat and spacecraft remain a critical and mission enabling piece in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density coupled with high hydrogen content. Polyethylene fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of Polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at NASA's Marshall Space Flight Center and tested against 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Kaul, Raj K.↗
NASA NTRSDate not supplied

Preliminary Results from the Saffire VI Experiment

Preliminary results are presented for one test of the last flight of the Spacecraft Fire Experiment (Saffire VI) which was conducted on an orbiting Cygnus spacecraft. These experiments directly address the risks associated with our understanding of spacecraft fire behavior at practical length scales and geometries. The lack of this experimental data has forced spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, flame self-extinguishment, fire detection, and suppression. The Saffire experiment was developed by an international team of investigators with the goal of addressing open issues in spacecraft fire safety. NASA’s Spacecraft Fire Safety Demonstration Project was formulated with the goal of conducting a series of large-scale experiments in spacecraft environments that represent practical spacecraft fires. These tests spanned 1.5 to 3.2 kW with free air volumes of 17 to 19 cubic meters. The final flight in the series of six experiments examined concurrent spread over large samples (all 41 cm wide) including a thin sheet of flammable fuel (cotton/fiberglass 50 cm long); 2-sided spread over 1 cm thick polymethyl methacrylate (PMMA) (18 cm long); 1-sided spread over 0.5 cm thick (18 cm long); and Nomex fabric (7 cm long). Results are presented for the PMMA samples, the SIBAL sample, and the thin cotton samples from Saffire IV and V. The flame heat release is determined and compared to the overall temperature rise in the spacecraft and the change in the concentration of carbon dioxide and carbon monoxide in the spacecraft. Overall, the temperature and pressure rise in the spacecraft were found to be less significant than the increase in carbon dioxide and carbon monoxide.

fire↗
NASA NTRS2004

Space radiation transport properties of polyethylene-based composites

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Polyethylene/chemistry↗
NASA NTRS1991

The effect of anisotropic emission from thick accretion disks on the luminosity functions of active galactic nuclei

High-luminosity active galactic nuclei (AGNs) powered by accretion onto a massive black hole (or other compact object) may have bolometric luminosities dominated by thermal emission from a geometrically thick accretion disk. Radiation from these disks is strongly anisotropic, which has important consequences for the observed luminosity distribution, and therefore for systematic biases in flux-limited samples. The effect of anisotropic emission from an ensemble of AGNs with random oriented thick disks radiating at or near the Eddington limit is calculated. Because of their higher luminosities, it is predicted face-on disks should constitute an increasing fraction of observed high-redshift, high-luminosity AGNs. Comparison of the results with observed quasar luminosity functions suggests a narrow mass distribution with an upper limit of about a billion solar masses for high-redshift quasars.

Urry, C. M.↗
NASA NTRS1985

Effect of conductivity and concentration on the sample stream in the transverse axis of a continuous flow electrophoresis chamber

The resolution of continuous flow electrophoresis systems is generally measured by the spread of the sample bands in the direction of the electrophoretic migration. This paper evaluates the cross section of the sample bands in the plane perpendicular to the flow and shows that the spread in the direction perpendicular to the migration increased significantly with the applied electric field. Concentrated samples of monodisperse latex particles and vinyltoluene T-butylstyrene particles in sample buffers of different electrical conductivities were used to map the shape of the sample bands relative to the zero electric field case. As the electric field was applied, the sample band spread from an initial diameter of only one-third the chamber thickness until it approached the chamber walls where electroosmosis significantly reduced the resolution of separation. It can be shown, however, that it is possible to minimize these distortions by careful sample preparation and experiment design.

Miller, Teresa Y.↗
NASA NTRSDate not supplied

Titan Sample Return Mission using V-Infinity Leveraging

The unique environment of the Saturnian moon Titan provides a particular incentive for a sample return mission in the mid twenty-first century. The thick atmosphere and low gravity provide both useful benefits and harrowing challenges that make optimizing the return trajectory, whether for time of flight or ΔV, especially important for such a long-term mission in order to maximize return. V-infinity leveraging provides a unique capability for finding epoch independent, reduced ΔV return trajectories which can be reliably converged from theoretical results. This paper will demonstrate the ability to use this technique to enable Titan sample missions and examine it relative to other options.

Titan↗
NASA NTRSDate not supplied

Titan Sample Return Mission Using V-Infinity Leveraging

The unique environment of the Saturnian moon Titan provides a particular incentive for a sample return mission in the mid twenty-first century. The thick atmosphere and low gravity provide both useful benefits and harrowing challenges that make optimizing the return trajectory, whether for time of flight or ΔV, especially important for such a long-term mission in order to maximize return. V-infinity leveraging provides a unique capability for finding epoch independent, reduced ΔV return trajectories which can be reliably converged from theoretical results. This paper will demonstrate the ability to use this technique to enable Titan sample missions and examine it relative to other options.

Titan↗
NASA NTRS1995

Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

Sali, Robert↗
NASA NTRS1974

Auger measurements on T-027 samples exposed during the Skylab 2 mission

Auger electron spectroscopy measurements performed on Skylab 2 indicate a low rate of deposition of permanent, continuous film contamination on nickel and gold surfaces positioned on the antisolar side of the spacecraft. These measurements and supportive evidence indicate that for the particular locations and orientations of these samples permanent films of less than 3 nm (30 A) thickness were deposited during an exposure of 40 hours at a temperature of approximately -32 C.

Peters, P. N.↗
NASA NTRS1976

Magellan - A balloon-borne collection technique for large cosmic dust particles

The paper describes a balloon-borne system for collecting large (50 to a few hundred micrometers in the major dimension) solid particles falling through the atmosphere at an altitude of about 30 km which are postulated to be fragments of larger cosmic particles or bodies which disintegrate on entering the atmosphere. The major component of the system is the collection surface - a funnel, 7.2 m in diameter, fabricated from mylar, 12 microns thick, and lightly coated with aluminum. Also described is the sample collector, which collects the particles gathered in the apex of the cone. Two successful flights of short duration using zero-pressure balloons have been achieved. Some examples of particles collected are shown. Mg, Al, Si, S, K, Ca, Ti, and Fe have been detected in these particles by energy dispersive X-ray analysis.

Wlochowicz, R.↗
NASA NTRS1977

A numerical method for the exact calculation of airloads associated with impulsively started wings

A numerical method is developed to calculate three-dimensional potential flows due to the steady and impulsive motion of isolated wing and wing-wing interaction problems. The velocity potential is represented by a discrete set of constant-doublet quadrilaterals on wing and wake surfaces. The exact surface boundary condition is enforced, and the solution is obtained in a step-by-step fashion, configurations being impulsively started from rest. Free-wake geometries are generated for each time step with Rankine or Lamb viscous vortex segments used in wake-velocity calculations. Sample results include calculated performance to steady state for a thick wing and indicial lift of a wing-wing interaction problem.

Summa, J. M.↗
NASA NTRS1980

Intensity analysis of XPS spectra to determine oxide uniformity - Application to SiO2/Si interfaces

A simple method of determining oxide uniformity is derived which requires no knowlege of film thickness, escape depth, or film composition. The method involves only the measurement of oxide and substrate intensities and is illustrated by analysis of XPS spectral data for thin SiO2 films grown both thermally and by low-temperature chemical vapor deposition on monocrystalline Si. A region 20-30 A thick is found near the SiO2/Si interface on thermally oxidized samples which has an inelastic mean free path 35% less than that found in the bulk oxide. This is interpreted as being due to lattice mismatch resulting in a strained region which is structurally, but not stoichiometrically, distinct from the bulk oxide.

Vasquez, R. P.↗