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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Crop and Substrate Tests with Single Use Rooting "Pillows" for the VEGGIE Plant Growth Hardware

VEGGIE is a small plant production chamber built by ORBITEC. This chamber can be collapsed for easy stowage and deployed in orbit. It is designed for gravity independent operation, and provides 0.17 square m of crop growth area with three primary subsystems: an LED light panel, extendable transparent Teflon bellows to enclose the plants, and a wicking reservoir. VEGGIE would provide the capability for astronauts to grow fresh foods for dietary supplementation. Initial planting concepts tested with the VEGGIE included direct seeding or plug placement on the reservoir surface. These options had issues of salt accumulation and eventual toxicity if the reservoir was filled with nutrient solution, and hardware reuse was limited due to sanitation. In response a rooting packet or "pillow" concept was developed: single-use bags of media containing time release fertilizer with a wicking surface contacting the VEGGIE reservoir. Pillows being tested are small electrostatic bags with a Nitex nylon mesh side, each holding 100 mL of dry media. Six pillows fit in one VEGGIE unit; however pillow size could vary depending on crop selected. Seeds can be planted directly in pillows and planted pillows can be hydrated in space as desired. Our goals were to define optimal media and crops for an ISS mission scenario. Plant tests in pillows were performed in a controlled environment chamber set to habitat-relevant conditions, and capillary reservoir analogs were utilized. Media tested within pillows included: a commercial peat-based potting mix, arcillite (calcined clay), perlite: vermiculite, and peat-based: arcillite blends. Testing included 15 types of leafy greens, snow pea, radish, and herbs. Media performance was crop dependent, but generally plants showed the greatest growth in the peat-based: arcillite mixes. Crops with the best performance in pillows were identified, and testing is underway with select leafy greens examining plant and microbial load response to repeated harvest. We plan to use findings from previous flight testing with media to evaluate the effects of capillary flow from the reservoir to pillows in microgravity.

Massa, Gioia↗
NASA NTRS1980

Stratospheric aerosol modification by supersonic transport and space shuttle operations - Climate implications

The potential effects on stratospheric aerosols of supersonic transport emissions of sulfur dioxide gas and submicron soot granules, and space shuttle rocket emissions of aluminum oxide particulates are estimated. An interactive particle-gas model of the stratospheric aerosol layer is used to calculate changes due to exhaust emissions, and an accurate radiation transport model is employed to compute the effect of aerosol changes on the earth's average surface temperature. It is concluded that the release of large numbers of small particles (soot or aluminum oxide) into the stratosphere should not lead to a corresponding significant increase in the concentration of large, optically active aerosols, but that the increase in large particles is severely limited by the total mass of sulfate available to make large particles in situ, and by the rapid loss of small seed particles via coagulation. We find that a fleet of several hundred advanced supersonic aircraft operating daily at 20 km, or the launch of one space shuttle rocket per week, could produce roughly a 20% increase in the large-particle concentration of the stratosphere. We find, in addition, that aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.

Turco, R. P.↗
NASA NTRSDate not supplied

Did an Ancient Habitable Venus Provide the Seeds for Life Today?

Recent possible detections of Phosphine in the Venusian atmosphere [1,2] have spurred interest in the potential for life in the clouds of Venus given the limited number of abiotic alternatives determined thus far [3]. A number of theories have been posited as to how life could have arisen in the cloud decks of Venus (e.g. [4] and references therein) and how it might thrive in a supposedly hostile environment [5]. Over the past few years we have used forward modeling to investigate the possibilities of a temperate Venusian climate in its deep past. This affords us the opportunity to discuss the possibility for an early habitable Venus and its implications for habitability in the cloud layers today.

habitability↗
DOE OSTI2021

Colossal Grains for a New Structural Paradigm in Thin-Film Photovoltaics

II-VI based thin-film photovoltaics (PV) have experienced substantial commercial success on a foundation of fast large-scale deposition and processing. This type of processing, regardless of material type, nearly always results in small grain (nm to several um diameters) polycrystalline material that, if not for effective grain boundary (GB) and defect passivation, would severely limit PV performance. In the case of CdTe based PV technology, the nearly ubiquitous CdCl2 treatment is used, in part, to passivate the polycrystalline p-type absorber even though Cl is known to (and used to) compensate p-type II-VI materials. Given that VOC is still the most limited performance metric and it can only be improved through higher p-type absorber concentrations, CdCl2 treatments may be holding the technology back. In this talk, we will discuss results related to a process by which small grain CdSeTe material is rapidly transformed into very large grain material (100-1000um diameters, Fig. 1a). This explosive recrystallization, which we have termed colossal grain growth (CGG), occurs by a Cl free process with thin films (<10um) deposited using the same fast deposition techniques the industry has relied on for more than a decade. Our modeling suggests that GB recombination becomes significantly less important at these grain sizes and thus may eliminate the need for a CdCl2 treatment. This result is complimented by previous results of epitaxial growth at high rates on single crystal seed layers. Thin CdSeTe CGG seed layers can be used for rapid epitaxy of CdTe to complete a standard device stack (Fig.1b). This is an optimistic view and the current limitations and challenges related to this process and these materials will also be discussed, including alloy and substrate roughness sensitivity, intragrain material quality, and complex defect chemistry. These challenges are not insignificant but overcoming them may enable a new structural paradigm for thin-film PV.

CdTe↗
DOE OSTI2025

OzMALDI: A Gas-Phase, In-Source Ozonolysis Reaction for Efficient Double-Bond Assignment in Mass Spectrometry Imaging with Matrix-Assisted Laser Desorption/Ionization

Lipids make up an important class of biomolecules with diverse structures and varied chemical functions. This diversity is a major challenge in chemical analysis and limits our understanding of biological functions and regulation. A major way lipid isomers differ is by double-bond (db) position, and analyzing db-isomers is especially challenging for mass spectrometry imaging (MSI). Ozonolysis can be used to determine the dbposition and has been paired with MSI before. However, previous techniques require increased analysis time to allow for gas-phase reactions within an ion trap or ion mobility cell or additional sample preparation time to allow for offline ozonation. Here, we introduce a new ozonolysis method inside the matrix-assisted laser desorption-ionization (MALDI) source, termed OzMALDI, that simultaneously produces ozonides from all unsaturated lipids. This allows us to determine db-positions without adding additional reaction time while maintaining the high mass resolution provided by Orbitrap MS. This new technique is especially effective at determining multiple db-positions in lipids containing polyunsaturated fatty acids, which is a limitation of many previous techniques. OzMALDI-MSI was applied to the analysis of rat brain and genetically engineered Camelina and soybean seed samples, demonstrating the utility of this method and uncovering novel biological information.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Spatio-temporally shaped deep UV laser source for ultrabright photocathodes using novel upconversion techniques (Final Report)

The goal of this project was to take a VUV laser system designed by Kapteyn-Murnane Labs (KMLabs)—the Hyperion VUV, and increase its functionality, efficiency, and applicability by further probing the fundamental physics taking place in the system and optimizing the system performance. More specifically, DOE accelerator applications—particularly for XFELs that require low-emittance electron beams, require precisely controlled ultrashort pulses in the deep-UV at 250-260 nm to drive the photocathode electron source. This is conventionally done using an ultrafast infrared laser, with subsequent stages of nonlinear upconversion in solid-state nonlinear-optical crystal media (principally BBO, which is commonly used for UV upconversion). However, maintaining high spatial mode beam quality, as well as precisely controlled temporal profile, has proven a persistent challenge. As a possible alternative to this approach, KMLabs has demonstrated a system that generates vacuum ultraviolet light (VUV) by upconverting pulses from an infrared ultrafast laser in a gas-filled hollow waveguide, driving a process of highly cascaded harmonic generation (HCHG). Because HCHG upconversion is done in a gas, rather than a solid, at high intensity in a guided-wave geometry, it retains an excellent beam spatial profile as well as a large spectral bandwidth that allows for control over the temperal structure of the pulse. A challenge, however, is in energy scaling of this HCHG technique to the ~1-20 μJ pulses required for photocathode applications. To-date, the pulse energies used in published HCHG work are sub-10-nJ. This project proposed to explore ways to generate higher-energy pulses using HCHG, as well as to investigate spectral and temporal shaping of the deep UV pulses by pulse shaping the infrared laser used to seed the process. Although we showed that our approach works for generating light at 259 nm, the total pulse energy achieved seems limited to approximately the same value as past work. However, the techniques we investigated may well have benefits for extending this source to much shorter wavelength output.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Compressed Expanded Natural Graphite (CENG) Processing for PCM Composites

The use of phase change materials (PCMs) in thermal energy storage applications has received considerable attention in recent decades. Organic PCMs are popular due to their high latent heat of fusion, noncorrosive properties, and relative stability over many charge and discharge cycles. A primary limitation of these materials is their low thermal conductivity. This has led researchers to develop various methods to increase thermal conductivity by seeding PCM with or impregnating them into more conductive materials. One method is to impregnate PCMs into compressed expanded natural graphite (CENG) matrices, which can improve thermal conductivity by a factor of 100. CENG matrices have received particular interest due to their low cost, high porosity, small (nano/micro) pore size, high pore density, high thermal conductivity, and ability to be compressed into many geometries. PCM/CENG matrix composites have been extensively studied; however, the effect that CENG processing has on PCM saturation and the overall matrix thermal conductivity has not been well investigated. This processing includes four major steps including graphite intercalation, thermal shock, compression, and PCM saturation. Intercalation involves soaking graphite flakes in sulfuric and/or nitric acid to intercalate the acids between the graphene layers. The graphite flakes are then subjected to a high-temperature thermal shock, during which the intercalated acid is gasified rapidly, pushing the graphene layers apart, resulting in accordion-shaped graphite "worms". The "worms" are then compacted to a desired bulk density and then soaked with molten PCM until fully saturated. The properties of the produced CENG matrix, and its ability to allow PCM permeation, are sensitive to the processing parameters, namely, the thermal shock temperature and exposure time, as well as the matrix apparent density or porosity. Here, we study the effect of the thermal shock conditions necessary to expand intercalated graphite flakes on PCM saturation and the expanded graphite's thermal conductivity and morphology. We found that the thermal shock temperature exhibits the greatest influence. At greater shock temperatures, SEM images showed that expanded graphite worms exhibited greater density of pores, thus increasing total surface area within the matrices. Increasing thermal shock temperature yielded greater overall PCM saturation, as well as an increased rate of saturation. Improvements in PCM saturation rate and overall saturation are obtained as the shock temperature is increased. Longer exposure to thermal shock also improves initial saturation rates and is beneficial if a shortened impregnation time is needed. Thermal shock conditions did not impact thermal conductivity; however, conductivity was largely affected by matrix porosity. A local maximum in axial thermal conductivity was observed at around 83% porosity, which is similar to that observed in previous studies.

compressed expanded natural graphite↗
NASA NTRS2010

315mJ, 2-micrometers Double-Pulsed Coherent Differential Absorption Lidar Transmitter for Atmospheric CO2 Sensing

The design of a double pulsed, injection seeded, 2-micrometer compact coherent Differential absorption Lidar (DIAL) transmitter for CO2 sensing is presented. This system is hardened for ground and airborne applications. The design architecture includes three continuous wave lasers which provide controlled on and off line seeding, injection seeded power oscillator and a single amplifier operating in double pass configuration. As the derivative a coherent Doppler wind lidar, this instrument has the added benefit of providing wind information. The active laser material used for this application is a Ho: Tm:YLF crystal operates at the eye-safe wavelength. The 3-meter long folded ring resonator produces energy of 130-mJ (90/40) with a temporal pulse length around 220 nanoseconds and 530 nanosecond pulses for on and off lines respectively. The separation between the two pulses is on the order of 200 microseconds. The line width is in the order of 2.5MHz and the beam quality has an M(sup 2) of 1.1 times diffraction limited beam. A final output energy for a pair of both on and off pulses as high as 315 mJ (190/125) at a repetition rate of 10 Hz is achieved. The operating temperature is set around 20 C for the pump diode lasers and 10 C for the rod. Since the laser design has to meet high-energy as well as high beam quality requirements, close attention is paid to the laser head design to avoid thermal distortion in the rod. A side-pumped configuration is used and heat is removed uniformly by passing coolant through a tube slightly larger than the rod to reduce thermal gradient. This paper also discusses the advantage of using a long upper laser level life time laser crystal for DIAL application. In addition issues related to injection seeding with two different frequencies to achieve a transform limited line width will be presented.

Yu, Jirong↗
DOE OSTI2025

Soft x-ray high-harmonic generation in an anti-resonant hollow core fiber driven by a 3 μ m ultrafast laser

High-harmonic upconversion driven by a mid-infrared femtosecond laser can generate coherent soft x-ray beams in a tabletop-scale setup. Here, we report on a compact ytterbium-pumped optical parametric chirped pulse amplifier (OPCPA) laser system seeded by an all-fiber front-end and employing periodically poled lithium niobate (PPLN) nonlinear media operated near the pulse fluence limits of current commercially available PPLN crystals. The OPCPA delivers 3 µm wavelength pulses with 775 µJ energy at 1 kHz repetition rate, with transform-limited 120 fs pulse duration, diffraction-limited beam quality, and ultrahigh 0.33% rms energy stability over >18 h. Using this laser, we generate soft x-ray high harmonics (HHG) in argon gas by focusing into a low-loss, high-pressure gas-filled anti-resonant hollow core fiber (ARHCF), generating coherent light at photon energies up to the argon L-edge (250 eV) and carbon K-edge (284 eV), with high beam quality and ∼1% rms energy stability. This work demonstrates soft x-ray HHG in a high-efficiency guided-wave phase matched geometry, overcoming the high losses inherent to mid-IR propagation in unstructured waveguides, or the short interaction lengths of gas cells or jets. The ARHCF can operate in the long term without damage and with the repetition rate, stability, and robustness required for demanding applications in spectromicroscopy and imaging. Finally, we discuss routes for further optimizing the soft x-ray HHG flux by driving He at higher laser intensities using either the signal (1.5 μm) or idler wavelengths (3 μm).

Femtosecond lasers↗
NASA NTRS1972

Hall current effects in the Lewis magnetohydrodynamic generator

Data obtained in a magnetohydrodynamic generator are compared with theoretical values calculated by using the Dzung theory. The generator was operated with cesium-seeded argon as the working fluid. The gas temperature varied from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from 0.3 to 0.5, and the magnetic field strength from 0.2 to 1.6 T. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) limit generator performance.

Nichols, L. D.↗
NASA NTRS1984

An atomic oxygen facility for studying polymer materials for spacecraft applications

A nozzle beam facility utilizing microwave discharge on a helium carrier gas seeded with oxygen to produce atomic oxygen fluxes of the order of 10 to the 15th power atoms/cu cm/sec is described. In addition, limited test results obtained from exposing a graphite/epoxy composite and Kapton (H) film are presented in terms of mass loss measurements and changes in surface morphology.

Tennyson, R. C.↗
NASA NTRSDate not supplied

Neurovascular Outcomes of Ionizing Radiation in Human Blood-Brain Barrier Models

One of the main health risks in human deep space exploration is central nervous system (CNS) damage by ionizing radiation due to exposure to galactic cosmic rays (GCRs). In animal models, irradiation with simulated GCRs or their components has been shown to cause neurodegeneration and neuroinflammation associated with cognitive and behavioral dysfunction. The extent of CNS damage is partially mediated by the blood-brain barrier (BBB), which regulates the interaction between CNS and systemic responses to stressors in the rest of the body. The main cellular regulators of BBB permeability are astrocytes, which also modulate neuronal death, neuroinflammation and oxidative stress. However, studies on BBB and astrocyte functions in regulating CNS responses to ionizing radiation have been limited, especially in human tissue/organ analogs. Therefore, we developed a high throughput 3D human neurovascular system model, based on commercially available Mimetas OrganoPlates seeded by primary human cells, to investigate the neurovascular responses to simulated deep space radiation. Using this system, we have demonstrated that 600MeV/n 56Fe irradiation leads to cellular damage and increased blood-brain barrier permeability via dysfunction of brain cells called astrocytes, which appear to be the weakest link and therefore a highly suitable countermeasure target to reduce the impact of space radiation on the blood-brain barrier. We anticipate that our results form merely the first step in ongoing development of organ models, including their adaptation for personalized risk assessment, high throughput approaches to countermeasure screening and validation, and eventual payload adaptation.

organ-on-a-chip↗
DOE OSTI2021

Redundant roles of four ZIP family members in zinc homeostasis and seed development in Arabidopsis thaliana

Zinc (Zn) is essential for normal plant growth and development. The Zn-regulated transporter, iron-regulated transporter (IRT)-like protein (ZIP) family members are involved in Zn transport and cellular Zn homeostasis throughout the domains of life. In this study, we have characterized four ZIP transporters from Arabidopsis thaliana (IRT3, ZIP4, ZIP6, and ZIP9) to better understand their functional roles. The four ZIP proteins can restore the growth defect of a yeast Zn uptake mutant and are upregulated under Zn deficiency. Single and double mutants show no phenotypes under Zn-sufficient or Zn-limited growth conditions. In contrast, triple and quadruple mutants show impaired growth irrespective of external Zn supply due to reduced Zn translocation from root to shoot. All four ZIP genes are highly expressed during seed development, and siliques from all single and higher-order mutants exhibited an increased number of abnormal seeds and decreased Zn levels in mature seeds relative to wild type. The seed phenotypes could be reversed by supplementing the soil with Zn. Finally, our data demonstrate that IRT3, ZIP4, ZIP6, and ZIP9 function redundantly in maintaining Zn homeostasis and seed development in A. thaliana.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Novel fabrication tools for dynamic compression targets with engineered voids using photolithography methods

Mesoscale imperfections, such as pores and voids, can strongly modify the properties and the mechanical response of materials under extreme conditions. Tracking the material response and microstructure evolution during void collapse is crucial for understanding its performance. In particular, imperfections in the ablator materials, such as voids, can limit the efficiency of the fusion reaction and ultimately hinder ignition. To characterize how voids influence the response of materials during dynamic loading and seed hydrodynamic instabilities, we, in this paper, have developed a tailored fabrication procedure for designer targets with voids at specific locations. Our procedure uses SU-8 as a proxy for the ablator materials and hollow silica microspheres as a proxy for voids and pores. By using photolithography to design the targets’ geometry, we demonstrate precise and highly reproducible placement of a single void within the sample, which is key for a detailed understanding of its behavior under shock compression. This fabrication technique will benefit high-repetition rate experiments at x-ray and laser facilities. Insight from shock compression experiments will provide benchmarks for the next generation of microphysics modeling.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

The Effect of Supernova Convection On Neutron Star and Black Hole Masses

Abstract Our understanding of the convective-engine paradigm driving core-collapse supernovae has been used for two decades to predict the remnant mass distribution from stellar collapse. These predictions improve as our understanding of this engine increases. In this paper, we review our current understanding of convection (in particular, the growth rate of convection) in stellar collapse and study its effect on the remnant mass distribution. We show how the depth of the mass gap between neutron stars and black holes can help probe this convective growth. We include a study of the effects of stochasticity in both the stellar structure and the convective seeds caused by stellar burning. We study the role of rotation and its effect on the pair-instability mass gap. Under the paradigm limiting stellar rotation to those stars in tight binaries, we determine the effect of rotation on the remnant mass distribution.

Fryer, Chris L. (ORCID:0000000326240056)↗
NASA NTRS1972

Hall current effects in the Lewis magnetohydrodynamic generator.

Data obtained in the Lewis MHD generator are compared with theoretical values calculated using the Dzung (1966) theory. The generator is operated with cesium seeded argon as the working fluid. The gas temperature varies from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from .3 to .5, and the magnetic field strength from .2 to 1.6 tesla. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) are limiting generator performance.

Nichols, L. D.↗
NASA NTRS1987

Nondestructive evaluation of structural ceramics

A review is presented on research and development of techniques for nondestructive evaluation and characterization of advanced ceramics for heat engine applications. Highlighted in this review are Lewis Research Center efforts in microfocus radiography, scanning laser acoustic microscopy (SLAM), scanning acoustic microscopy (SAM), scanning electron acoustic microscopy (SEAM), and photoacoustic microscopy (PAM). The techniques were evaluated by applying them to research samples of green and sintered silicon nitride and silicon carbide in the form of modulus-of-rupture bars containing seeded voids. Probabilities of detection of voids were determined for diameters as small as 20 microns for microfucus radiography, SLAM, and SAM. Strengths and limitations of the techniques for ceramic applications are identified. Application of ultrasonics for characterizing ceramic microstructures is also discussed.

Klima, Stanley J.↗
NASA NTRS1997

Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow

Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity. Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics. In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from this study was that ultraviolet Rayleigh scattering is preferable in confined flow situations because of the increase in the ratio of Rayleigh scattering signal to stray laser light. On the other hand, in open flows, such as free jets and larger wind tunnels where stray laser light can be controlled, visible Rayleigh scattering is preferable.

Seasholtz, Richard G.↗