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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Ammonium-Coordinated Exchanger (ACE) Sorbents for Aqueous Oxyanion Metal Recovery/Removal

Ammonium coordinated exchanger (ACE) sorbents recovery/remove anionic contaminant/critical metals from water. Heavy reliance of the U.S. on foreign critical mineral (CM) supplies presents national security and economics risks. This prompted government action. Domestically recovering CM from unconventional water sources, largely through adsorption processes, could alleviate this problem. Acid mine drainage and mineral leachates are viable sources

amines↗
NASA NTRS1974

Power processor design considerations for a solar electric propulsion spacecraft

Propulsion power processor design options are described. The propulsion power processor generated the regulated dc voltages and currents from a solar array source of a solar electric propelled spacecraft. The power processor consisted of 12 power supplies that provide the regulated voltages and currents necessary to power a 30-cm mercury ion thruster. The design options for processing unregulated solar array power and for generating the regulated power required by each supply are studied. The technical approaches utilized in the developed design and the technological limitation of the identified design options are discussed. Alternate approaches for delivering power to a number of mercury ion thrusters and methods of optimizing are described. It was concluded that this power processor design should be considered for application in solar electric propulsion missions of the future.

Costogue, E. N.↗
NASA NTRS1976

Characteristics and potential applications of orbiting ultrahigh vacuum facilities

The characteristics of an orbiting molecular shield ultrahigh vacuum facility are described and some examples of potential applications are discussed. Published results of a kinetic theory analysis are given. Densities within the shield of less than 1000 molecules/cu cm can be obtained allowing high purity materials processing experiments to be performed in orbit under the simultaneous conditions of ultrahigh vacuum and microgravity. Two specific experiments are discussed: the production of ultrapure materials by the electrotransport technique developed at ERDA's Ames Laboratory, Iowa State University, and the vapor deposition and space preparation of silicon solar cells.

Melfi, L. T., Jr.↗
NASA NTRS1980

A model for sunspot associated emission at 6 cm wavelength

Two-dimensional maps of total intensity and circular polarization of a sunspot region at 6 cm have been calculated using a simple model for the chromosphere-corona transition region and observations of the longitudinal component of the photospheric magnetic field. The calculations are in good agreement with the high resolution observations of the same sunspot region at 6 cm, obtained with the Westerbork Synthesis Radio Telescope. It is shown that the 6 cm radiation is predominantly due to gyroresonance absorption process at the second and third harmonics of the gyrofrequency (H = 900-600 G). Estimates of the conductive flux and the electron density in the transition region above the sunspot are also given.

Alissandrakis, C. E.↗
NASA NTRS1981

A Module Experimental Process System Development Unit (MEPSDU)

The technical readiness of a cost effective process sequence that has the potential for the production of flat plate photovoltaic modules which met the price goal in 1986 of $.70 or less per Watt peak was demonstrated. The proposed process sequence was reviewed and laboratory verification experiments were conducted. The preliminary process includes the following features: semicrystalline silicon (10 cm by 10 cm) as the silicon input material; spray on dopant diffusion source; Al paste BSF formation; spray on AR coating; electroless Ni plate solder dip metallization; laser scribe edges; K & S tabbing and stringing machine; and laminated EVA modules.

Source record↗
NASA NTRS1993

The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

A combination of porewater and solid phase analysis as well as a series of sediment incubations are used to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). Solid phase data are integrated with incubation results to define the zones of the various oxidation processes. At S(9), surface Mn enrichments of up to 3.5 wt pct were found, and with such a ready source of Mn, dissimilatory Mn reduction was the only significant anaerobic process of carbon oxidation in the surface 10 cm of the sediment. At S(4) and S(6), active Mn reduction occurred; however, most of the Mn reduction may have resulted from the oxidation of acid volatile sulfides and Fe(2+) rather than by a dissimilatory sulfate. Dissolved Mn(2+) was found to completely adsorb onto sediment containing fully oxidized Mn oxides.

Canfield, Donald E.↗
NASA NTRS1995

RISC Processors and High Performance Computing

In this tutorial, we will discuss top five current RISC microprocessors: The IBM Power2, which is used in the IBM RS6000/590 workstation and in the IBM SP2 parallel supercomputer, the DEC Alpha, which is in the DEC Alpha workstation and in the Cray T3D; the MIPS R8000, which is used in the SGI Power Challenge; the HP PA-RISC 7100, which is used in the HP 700 series workstations and in the Convex Exemplar; and the Cray proprietary processor, which is used in the new Cray J916. The architecture of these microprocessors will first be presented. The effective performance of these processors will then be compared, both by citing standard benchmarks and also in the context of implementing a real applications. In the process, different programming models such as data parallel (CM Fortran and HPF) and message passing (PVM and MPI) will be introduced and compared. The latest NAS Parallel Benchmark (NPB) absolute performance and performance per dollar figures will be presented. The next generation of the NP13 will also be described. The tutorial will conclude with a discussion of general trends in the field of high performance computing, including likely future developments in hardware and software technology, and the relative roles of vector supercomputers tightly coupled parallel computers, and clusters of workstations. This tutorial will provide a unique cross-machine comparison not available elsewhere.

Saini, Subhash↗
NASA NTRS2008

Mapping Snow Grain Size over Greenland from MODIS

This paper presents a new automatic algorithm to derive optical snow grain size (SGS) at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Differently from previous approaches, snow grains are not assumed to be spherical but a fractal approach is used to account for their irregular shape. The retrieval is conceptually based on an analytical asymptotic radiative transfer model which predicts spectral bidirectional snow reflectance as a function of the grain size and ice absorption. The analytical form of solution leads to an explicit and fast retrieval algorithm. The time series analysis of derived SGS shows a good sensitivity to snow metamorphism, including melting and snow precipitation events. Preprocessing is performed by a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, which includes gridding MODIS data to 1 km resolution, water vapor retrieval, cloud masking and an atmospheric correction. MAIAC cloud mask (CM) is a new algorithm based on a time series of gridded MODIS measurements and an image-based rather than pixel-based processing. Extensive processing of MODIS TERRA data over Greenland shows a robust performance of CM algorithm in discrimination of clouds over bright snow and ice. As part of the validation analysis, SGS derived from MODIS over selected sites in 2004 was compared to the microwave brightness temperature measurements of SSM\I radiometer, which is sensitive to the amount of liquid water in the snowpack. The comparison showed a good qualitative agreement, with both datasets detecting two main periods of snowmelt. Additionally, MODIS SGS was compared with predictions of the snow model CROCUS driven by measurements of the automatic whether stations of the Greenland Climate Network. We found that CROCUS grain size is on average a factor of two larger than MODIS-derived SGS. Overall, the agreement between CROCUS and MODIS results was satisfactory, in particular before and during the first melting period in mid-June. Following detailed time series analysis of SGS for four permanent sites, the paper presents SGS maps over the Greenland ice sheet for the March-September period of 2004.

Lyapustin, Alexei↗
NASA NTRS2011

Project Management Meets Change Management - A Success Story. Focus Area: Tech Perspectives TI012SN

Utilizing the concepts and terminology from Project Management, the process of planning and executing a Change Management (CM) Infrastructure improvement project is described. The primary audience for this presentation includes both experienced and relatively new CM administrators and their managers. It also includes anyone with an interest in the application of project management knowledge to CM administration. There are several benefits: the complexity of the CM tool technology is more manageable, CM administrators get to use project management knowledge to complete a project (not "firefighting"), improve relations with your customers (that means developers and managers), and get the opportunity to do it again.

Hall, Wayne↗
NASA NTRS2011

"Solar-Wind-Rich" Howardite: True Regolith vs. CM-Implanted Components

Howardite, eucrite and diogenite meteorites (collectively HED) likely originate from asteroid 4-Vesta [1], one of two asteroids targeted by NASA s Dawn mission. Many howardites (polymict breccias of E and D material) contain "regolithic" features, including impact-melt clasts, fragmental breccia clasts, and carbonaceous chondrite fragments. True regolithic nature can be determined through noble gas analysis, as Solar Wind (SW) is implanted into the upper-most surfaces of solar system bodies. Whilst previous work [2] suggested that high siderophile element contents (e.g. Ni of 300-1200 g/g) were regolith indicators, we found no obvious correlation between SW and these indicators in our initial howardite noble gas analyses [3]. We observed CM-like fragments in a number of our howardites, whose textures suggest late addition to the breccia assemblage [4]. As typical CMs contain mixtures of SW (in matrix) and planetary (in clasts) components [5], we investigate the dominance of such components in SW-rich howardites. This will help deter-mine the extent of implanted SW in HED grains vs. SW and planetary gases from CM fragments, and allow better understanding of regolith processes

Cartwright, Julia A.↗
NASA NTRS2013

Forward-Looking IED Detector Ground Penetrating Radar

There have been many developments of mine or metal detectors based on ground penetrating radar techniques, usually in hand-held or rover-mounted devices. In most mine or metal detector applications, conditions are in a stationary mode and detection speed is not an important factor. A novel, forward-looking, stepped-frequency ground penetrating radar (GPR) has been developed with a capability to detect improvised explosive devices (IEDs) at vehicular speeds of 15 to 20 mph (24 to 32 km/h), 10 to 20 m ahead of the vehicle, to ensure adequate time for response. The GPR system employs two horn antennas (1.7 to 2.6 GHz, 20 dBi) as transmit and receive. The detector system features a user-friendly instantaneous display on a laptop PC and is a low-power-consumption (3 W) compact system with minimal impact on vehicle operations. In practice, the whole GPR system and a laptop PC can be powered by plugging into a cigarette lighter of a vehicle. The stepped-frequency continuous-wave (CW) radar scans frequency from 1.7 to 2.6 GHz in 1,000 steps of 0.9 MHz, with the full frequency scan in 60 ms. The GPR uses a bi-static configuration with one horn antenna used as a transmitter and the other used as a receiver so that isolation between transmitter and receiver is improved. Since the horn antennas (20 dBi) are mounted on the roof of a vehicle at a shallow inclination angle (15 to 25 with respect to horizontal), there is a first-order reduction in ground reflection so that a significant amount of the total reflected power received by the GPR comes from the scattering of RF energy off of buried objects. The stepped-frequency technique works by transmitting a tone at a particular frequency, while the received signal is mixed with the transmitted tone. As a result, the output of the mixer produces a signal that indicates the strength of the received signal and the extent to which it is in phase or out of phase with the transmitted tone. By taking measurements of the phase relationship between the transmitted and received signals over a wide frequency range, an interference pattern is produced showing all target reflections. When a Fourier transform is performed on this pattern, the result is a time-domain representation of targets. Among the advantages of this technique over impulse radar is the ability to transmit and receive much more total energy, and to use non-damped, highly focused horn antennas. The novelty of the IED detector GPR has been achieved by miniaturization of GPR electronics (single electronics board, 10x5x2 cm), low power consumption (3 W), faster signal processing capability, and minimal impact on vehicle operations.

Kim, Soon Sam↗
NASA NTRS1988

Directional measurement of short ocean waves with stereophotography

Stereophotographs of the sea surface, acquired during the Tower Ocean Wave and Radar Dependence experiment are analyzed to yield directional wave height spectra of short surface waves in the 6-80-cm range. The omnidirectional wave height spectra are found to deviate from the k exp -4 distribution, where k is the wave number. The stereo data processing errors are found to be within + or - 5 percent. The omnidirectional spectra yield 514 deg of freedom for 30-cm-long waves. The directional distribution of short waves is processed with a directional resolution of 30 deg, so as to yield 72 deg of freedom for 30-cm-long waves. The directional distributions show peaks that are aligned with the wind and swell directions. It is found that dynamically relevant measurements can be obtained with stereophotography, after removal of the mean surface associated with long waves.

Shemdin, Omar H.↗
DOE OSTI2023

The kinetics of the PuO 2 to Pu 2 O 3 conversion

Here in an oxidizing environment, the oxide formed on plutonium (Pu) metal is composed of a plutonium dioxide (PuO 2 ) top layer and a thin cubic plutonium sesquioxide (Pu 2 O 3 ) middle layer. In a reducing environment, the PuO 2 layer auto-reduces to cubic Pu 2 O 3 . The speed and extent of this conversion depend on the combination of temperature and time. While PuO 2 provides a strong diffusion barrier against unwanted Pu corrosion by gaseous species (like hydrogen), Pu 2 O 3 does not, since its crystal structure has chains of oxygen vacancies. The kinetics of the PuO 2 reduction are, therefore, of fundamental interest and enable researchers to better protect Pu from corrosion. In this report, the oxygen-diffusion-limited kinetics of the dioxide to sesquioxide conversion were obtained by dynamically heating a PuO 2 -covered Pu sample from 294 to 418 K in a high-vacuum vessel equipped with an in situ spectroscopic ellipsometer. The physical/chemical constraints in the conversion process were combined with the ellipsometry method of multi-sample analysis to track the percentage of PuO 2 and to compute the extent of Pu 2 O 3 formation. The resulting diffusion coefficients were compared against and then combined with complementary literature data to produce a comprehensive set of kinetic parameters for reliably modeling oxide conversion over a larger temperature range than spanned by prior studies. The extracted thermal activation energy barrier (43.7 kJ/mol) and pre-exponential factor (5.0 × 10 -10 cm 2 /s) for the oxygen-diffusion-limited process can be used to accurately model the PuO 2 to Pu 2 O 3 transformation in vacuum and/or inert gas applications.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Recycle Requirements for NASA's 30 cm Xenon Ion Thruster

Electrical breakdowns have been observed during ion thruster operation. These breakdowns, or arcs, can be caused by several conditions. In flight systems, the power processing unit must be designed to handle these faults autonomously. This has a strong impact on power processor requirements and must be understood fully for the power processing unit being designed for the NASA Solar Electric Propulsion Technology Application Readiness program. In this study, fault conditions were investigated using a NASA 30 cm ion thruster and a power console. Power processing unit output specifications were defined based on the breakdown phenomena identified and characterized.

Pinero, Luis R.↗
DOE OSTI2024

Excitons in Hematite Fe 2 O 3 : Short-Time Dynamics from TD-DFT and Non-Adiabatic Dynamics Theories

We present a first-principles study of the short-time dynamics of excitons in hematite Fe 2 O 3 . We used time-dependent density functional theory (TD-DFT) with an underlying DFT+U treatment of electron interactions to characterize the electronic structure of excitons and nonadiabatic molecular dynamics theory (NA-MD) to determine their recombination (electronic ground-state recovery) and relaxation dynamics. Decoherence-corrected trajectory surface hopping approaches in NA-MD simulations yielded recovery times of ~1.1 to 1.8 ns and “higher-lying” exciton relaxation times of ~60 to 70 fs, in accord with experimentally derived lifetimes. With hematite phonons in the range of ~100 to 700 cm –1 , higher-lying excitons relax within one or two oscillations of the phonons before getting trapped into an electron–hole pair Exc-3 structure on the first excited state potential energy surface. This structure resembles already a pair of polarons (electron polaron plus hole polaron) with associated lattice distortions three (3) basal planes away. On longer time scales, the electron–hole bipolaronic pair hops to structures Exc-5, then Exc-7, then Exc-9, ... with the electron polaron and hole polaron separated by 5, 7, 9, ... basal planes in a process of charge separation. The largest frequency phonon ~672 cm –1 for the Exc-3 exciton structure is associated with the electron polaron moiety of the exciton. This phonon is a good candidate for giving rise to the recently observed and reported postexcitation transient IR absorption peak.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Pioneer-Venus radio occultation (ORO) data reduction: Profiles of 13 cm absorptivity

In order to characterize possible variations in the abundance and distribution of subcloud sulfuric acid vapor, 13 cm radio occultation signals from 23 orbits that occurred in late 1986 and 1987 (Season 10) and 7 orbits that occurred in 1979 (Season 1) were processed. The data were inverted via inverse Abel transform to produce 13 cm absorptivity profiles. Pressure and temperature profiles obtained with the Pioneer-Venus night probe and the northern probe were used along with the absorptivity profiles to infer upper limits for vertical profiles of the abundance of gaseous H2SO4. In addition to inverting the data, error bars were placed on the absorptivity profiles and H2SO4 abundance profiles using the standard propagation of errors. These error bars were developed by considering the effects of statistical errors only. The profiles show a distinct pattern with regard to latitude which is consistent with latitude variations observed in data obtained during the occultation seasons nos. 1 and 2. However, when compared with the earlier data, the recent occultation studies suggest that the amount of sulfuric acid vapor occurring at and below the main cloud layer may have decreased between early 1979 and late 1986.

Steffes, Paul G.↗
DOE OSTI2024

Storage and persistence of organic carbon in the upper three meters of soil under arable and native prairie land use

Aims: Land use change from native grasslands to arable lands globally impacts soil ecosystem functions, including the storage of soil organic carbon (SOC). Understanding the factors affecting SOC changes in topsoil and subsoil due to land use is crucial for effective mitigation strategies. We determined SOC storage and persistence as affected by land use change from native prairies to arable lands. Methods: Here we examined SOC stocks, soil δ 13 C and Δ 14 C signatures, microbial communities (bacteria and fungi), and soil mineral characteristics under native prairies and long-term arable lands (i.e., > 40 years) down to 3 m in the U.S. Midwest. Results: Native prairie soils had higher SOC stocks in the A horizon and 0–50 cm depth increment than arable soils. For both land use types, the δ 13 C and Δ 14 C values significantly decreased with depth, with the latter pointing towards highly stabilized SOC, especially in the B- and C-horizons. Analysis of the microbial communities indicated that the diversity of bacteria and fungi decreased with increasing soil depth. The content of oxalate soluble Al appeared to be the single most important predictor of SOC across horizons and land use types. Conclusion: Our data suggest that most SOC gains and losses and transformation and translocation processes seem to be restricted to the uppermost 50 cm. Increasing SOC retention in the A and B horizons within the 0–50 cm depth would enhance organic material serving as substrate and nutrients for microbes and plants (A horizon) and facilitate long-term SOC storage in the subsoil (B horizon).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Large area, low cost space solar cells with optional wraparound contacts

Design parameters for two large area, low cost solar cells are presented, and electron irradiation testing, thermal alpha testing, and cell processing are discussed. The devices are a 2 ohm-cm base resistivity silicon cell with an evaporated aluminum reflector produced in a dielectric wraparound cell, and a 10 ohm-cm silicon cell with the BSF/BSR combination and a conventional contact system. Both cells are 5.9 x 5.9 cm and require 200 micron thick silicon material due to mission weight constraints. Normalized values for open circuit voltage, short circuit current, and maximum power calculations derived from electron radiation testing are given. In addition, thermal alpha testing values of absorptivity and emittance are included. A pilot cell processing run produced cells averaging 14.4% efficiencies at AMO 28 C. Manufacturing for such cells will be on a mechanized process line, and the area of coverslide application technology must be considered in order to achieve cost effective production.

Michaels, D.↗