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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 NTRS2017

Crater Morphometry and Crater Degradation on Mercury: Mercury Laser Altimeter (MLA) Measurements and Comparison to Stereo-DTM Derived Results

Two types of measurements of Mercury's surface topography were obtained by the MESSENGER (MErcury Surface Space ENvironment, GEochemisty and Ranging) spacecraft: laser ranging data from Mercury Laser Altimeter (MLA) [1], and stereo imagery from the Mercury Dual Imaging System (MDIS) camera [e.g., 2, 3]. MLA data provide precise and accurate elevation meaurements, but with sparse spatial sampling except at the highest northern latitudes. Digital terrain models (DTMs) from MDIS have superior resolution but with less vertical accuracy, limited approximately to the pixel resolution of the original images (in the case of [3], 15-75 m). Last year [4], we reported topographic measurements of craters in the D=2.5 to 5 km diameter range from stereo images and suggested that craters on Mercury degrade more quickly than on the Moon (by a factor of up to approximately 10×). However, we listed several alternative explanations for this finding, including the hypothesis that the lower depth/diameter ratios we observe might be a result of the resolution and accuracy of the stereo DTMs. Thus, additional measurements were undertaken using MLA data to examine the morphometry of craters in this diameter range and assess whether the faster crater degradation rates proposed to occur on Mercury is robust.

morphometry↗
NASA NTRS1991

Icing characteristics of a natural-laminar-flow, a medium-speed, and a swept, medium-speed airfoil

Tests were conducted in the Icing Research Tunnel at the NASA Lewis Research Center to determine the icing characteristics of three modern airfoils: a natural-laminar-flow, a medium-speed, and a swept medium-speed airfoil. The tests measured the impingement characteristics and drag degradation for angles-of-attack typifying cruise and climb for cloud conditions typifying the range that might be encountered in flight. The maximum degradation occurred at the cruise angle-of-attack for the long, glaze ice condition for all three airfoils with increases over baseline drag being 486 percent, 510 percent, and 465 percent for the natural-laminar-flow, the medium-speed, and the swept, medium-speed airfoils, respectively. For the climb angle-of-attack, the maximum drag degradation (and total extent of impingement) observed were also for the long, glaze ice condition and were 261 percent, 181 percent, and 331 percent, respectively. The minimum drag degradation (and extent of impingement) occurred for the cruise condition and for the short, rime spray with increases over baseline drag values being 47 percent, 28 percent, 46 percent, respectively.

Bidwell, Colin S.↗
NASA NTRS1991

RL-34 ring laser gyro laboratory evaluation for the Deep Space Network antenna application

The overall results of this laboratory evaluation are quite encouraging. The gyro data is in good agreement with the system's overall pointing performance, which is quite close to the technical objectives for the Deep Space Network (DSN) application. The system can be calibrated to the levels required for millidegree levels of pointing performance, and initialization performance is within the required 0.001 degree objective. The blind target acquisition performance is within a factor of two of the 0.0001 degree objective, limited only by a combination of the slow rate (0.5 deg/sec) and the existing production quantization logic (0.38 arc-sec/pulse). Logic circuitry exists to better this performance such that it will better the objective by 50 percent. Representative data with this circuitry has been provided for illustration. Target tracking performance is about twice the one millidegree objective, with several factors contributing. The first factor is the bias stability of the gyros, which is exceptional, but will limit performance to the 0.001 and 0.002 degree range for long tracking periods. The second contributing factor is the accelerometer contributions when the system is elevated. These degrade performance into the 0.003 to 0.004 degree range, which could be improved upon with some additional changes. Finally, we have provided a set of recommendations to improve performance closer to the technical objectives. These recommendations include gyro, electronics, and system configurational changes that form the basis for additional work to achieve the desired performance. In conclusion, we believe that the RL-34 ring laser gyro-based advanced navigation system demonstrated performance consistent with expectations and technical objectives, and it has the potential for even further enhancement for the DSN application.

Source record↗
DOE OSTI2023

Photocatalytic degradation of orange II dye via high pore volume polymorph zirconium-doped titania under visible light irradiation

A series of mixed-phase Zr-doped TiO 2 was utilized for the photocatalytic degradation of orange II dye. These materials were synthesized through a sol–gel technique by varying the amounts of zirconium in the photocatalysts. These materials were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), Raman spectroscopy, thermogravimetry analysis (TGA), and X-ray photoelectron spectroscopy (XPS) among others. XRF and XPS data showed that the elemental composition of the photocatalysts consists of zirconium, titanium, and oxygen. In addition, XRD and Raman spectroscopy confirmed the existence of anatase and rutile phases of TiO 2 . The TGA analyses showed that the undoped TiO 2 was the most stable, with no significant weight loss during the heating range. Furthermore, the materials can effectively degrade orange II dye solution up to 7 cycles through asymmetric cleavage of the azo bond.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Acoustic Codes in 2D Spherical Coordinate

Finite-difference methods are widely used to simulate infrasound propagation in the atmosphere. Flexibility of finite-difference scheme allows implementation of highly heterogeneous media for sound propagation as well as complex source models for sound generation. While full 3-D finite-difference methods have been utilized for local infrasound propagation with pronounced topography, 2-D modeling approach has been preferred for regional and global propagation as full 3-D methods generally require enormous computational resources. Infrasound propagation is often simulated with a second-order finite difference scheme. This lowest-order finite-difference scheme is robust and straightforward to implement complex boundary conditions, but the solution includes large error with numerical dispersion and dissipation. This large numerical error may make the second-order finite-difference not optimal for long range infrasound propagation modeling as the numerical dispersion degrades the accuracy of the solution unacceptably. Here, we developed a high-order finite-difference solver for long-range infrasound simulation. The high-order scheme is particularly popular for linear wave modeling in aeroacoustics owing to its low-dispersive and low-dissipative behavior. We develop and evaluate a high-order finite difference scheme in 2-D axisymmetric coordinates. The axisymmetry allows to approximate 3-D spherical sound propagation and amplitude attenuation by a 2-D method. AC2Dr is developed to simulate infrasound propagation in realistic atmosphere, but can be used for linear acoustic waves in general materials with background flow. AC2Dr in an axisymmetric coordinates allows for spherical radiation of acoustic waves from compact sources.

Sjogreen, Bjorn↗
DOE OSTI2026

UV-Induced Degradation and Associated Metastability in TOPCon Photovoltaic Modules: Understanding Kinetics and Cell Variance

Tunnel oxide passivated contact (TOPCon) silicon photovoltaic (PV) modules are dominating the PV market, but they may be susceptible to degradation under ultraviolet (UV)-containing light. Quantifying the impacts of UV-induced degradation (UVID) is complicated by an associated metastability causing further degradation under dark storage and rapid recovery under sunlight. Here, we study modules that have -2.3% to -3.2% nonrecoverable UVID loss after 60 kWh/m2 dose of 340 nm light and additional recoverable loss under dark storage. We use in situ electroluminescence (EL) imaging to characterize the post-UVID metastability at the module level. The cell-by-cell dark degradation and recovery kinetics span a wide range from +6% to -70% changes in EL intensity after 520 h of dark storage, which returns to +- 4% of the initial post-UVID EL intensity after illumination. The kinetics follow double exponential rates with dark storage degradation time constants of 345 and 45 h, and UV light recovery time constants of 5 min and 36 s. We propose that this is consistent with prior reports of kinetics for light-soaking metastability in Al2O3 passivation. Finally, we further show that cells having high UVID also have injection-dependent effective carrier lifetimes and significant intra-cell variance, suggesting possible origins of processing inconsistency.

14 SOLAR ENERGY↗
NASA NTRS1993

Characterization of atrial natriuretic peptide degradation by cell-surface peptidase activity on endothelial cells

Atrial natriuretic peptide (ANP) is a fluid-regulating peptide hormone that promotes vasorelaxation, natriuresis, and diuresis. The mechanisms for the release of ANP and for its clearance from the circulation play important roles in modulating its biological effects. Recently, we have reported that the cell surface of an endothelial cell line, CPA47, could degrade 125I-ANP in the presence of EDTA. In this study, we have characterized this degradation of 125I-ANP. The kinetics of ANP degradation by the surface of CPA47 cells were first order, with a Km of 320 +/- 60 nM and Vmax of 35 +/- 14 pmol of ANP degraded/10 min/10(5) cells at pH 7.4. ANP is degraded by the surface of CPA47 cells over a broad pH range from 7.0-8.5. Potato carboxypeptidase inhibitor and bestatin inhibited 125I-ANP degradation, suggesting that this degradative activity on the surface of CPA47 cells has exopeptidase characteristics. The selectivity of CPA47 cell-surface degradation of ANP was demonstrated when 125I-ANP degradation was inhibited in the presence of neuropeptide Y and angiotensin I and II but not bradykinin, bombesin, endothelin-1, or substance P. The C-terminal amino acids phe26 and tyr28 were deduced to be important for ANP interaction with the cell-surface peptidase(s) based on comparison of the IC50 of various ANP analogues and other natriuretic peptides for the inhibition of ANP degradation. These data suggest that a newly characterized divalent cation-independent exopeptidase(s) that selectively recognizes ANP and some other vasoactive peptides exists on the surface of endothelial cells.

NASA Discipline Regulatory Physiology↗
DOE OSTI2024

One hundred priority questions for advancing seagrass conservation in Europe

Societal Impact Statement Seagrass ecosystems are of fundamental importance to our planet and wellbeing. Seagrasses are marine flowering plants, which engineer ecosystems that provide a multitude of ecosystem services, for example, blue foods and carbon sequestration. Seagrass ecosystems have largely been degraded across much of their global range. There is now increasing interest in the conservation and restoration of these systems, particularly in the context of the climate emergency and the biodiversity crisis. The collation of 100 questions from experts across Europe could, if answered, improve our ability to conserve and restore these systems by facilitating a fundamental shift in the success of such work. Summary Seagrass meadows provide numerous ecosystem services including biodiversity, coastal protection, and carbon sequestration. In Europe, seagrasses can be found in shallow sheltered waters along coastlines, in estuaries & lagoons, and around islands, but their distribution has declined. Factors such as poor water quality, coastal modification, mechanical damage, overfishing, land‐sea interactions, climate change and disease have reduced the coverage of Europe’s seagrasses necessitating their recovery. Research, monitoring and conservation efforts on seagrass ecosystems in Europe are mostly uncoordinated and biased towards certain species and regions, resulting in inadequate delivery of critical information for their management. Here, we aim to identify the 100 priority questions, that if addressed would strongly advance seagrass monitoring, research and conservation in Europe. Using a Delphi method, researchers, practitioners, and policymakers with seagrass experience from across Europe and with diverse seagrass expertise participated in the process that involved the formulation of research questions, a voting process and an online workshop to identify the final list of the 100 questions. The final list of questions covers areas across nine themes: Biodiversity & Ecology; Ecosystem services; Blue carbon; Fishery support; Drivers, Threats, Resilience & Response; Monitoring & Assessment; Conservation & Restoration; Governance, Policy & Management; and Communication. Answering these questions will fill current knowledge gaps and place European seagrass onto a positive trajectory of recovery.

Nordlund, Lina Mtwana↗
DOE OSTI2025

Low two-level-system noise in hydrogenated amorphous silicon

At sub-Kelvin temperatures, two-level systems (TLSs) present in amorphous dielectrics source a permittivity noise, degrading the performance of a wide range of devices using superconductive resonators such as qubits or kinetic inductance detectors. We report here on measurements of TLS noise in hydrogenated amorphous silicon (a-Si:H) films deposited by plasma-enhanced chemical vapor deposition in superconductive lumped element resonators using parallel-plate capacitors. In conclusion, the TLS noise results presented in this article for two recipes of a-Si:H improve on the best results achieved in the literature by a factor >5 for a-Si:H and other amorphous dielectrics and are comparable to those observed for resonators deposited on crystalline dielectrics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Effect of Low Temperature Nitrogen Baking on Superconducting Radio Frequency Cavities With Different Frequency

We report the rf performance of several single-cell superconducting radiofrequency cavities frequency ranging from 1.3-3.0 GHz after low temperature baking in nitrogen environment The cavities are treated at different temperature in the range of (120-160oC) for extended period of time (~24-48 hours) with nitrogen gas injection in the furnace. The improvement in Q0 with Q-rise in some case was observed when nitrogen gas was injected at elevated temperature (~250-290 oC) and held at the temperature range 120-200 oC without any degradation in accelerating gradient over the baseline performance. The temperature and time of baking play significant role in dependence of quality factor on accelerating gradient.

Khanal, B.↗
DOE OSTI2021

Forged Ingot Niobium Technology for Accelerator Applications and Scientific Frontiers

We report the rf performance of several single-cell superconducting radiofrequency cavities frequency ranging from 1.3-3.0 GHz after low temperature baking in nitrogen environment The cavities are treated at different temperature in the range of (120-160oC) for extended period of time (~24-48 hours) with nitrogen gas injection in the furnace. The improvement in Q0 with Q-rise in some case was observed when nitrogen gas was injected at elevated temperature (~250-290 oC) and held at the temperature range 120-200 oC without any degradation in accelerating gradient over the baseline performance. The temperature and time of baking play significant role in dependence of quality factor on accelerating gradient.

Khanal, B.↗
NASA NTRS1978

Power density in direct nuclear-pumped He-3 lasers

The interaction of neutron beams with He-3 gas is of interest for nuclear pumped lasers. The effects of spectral dependence of the neutron beam, neutron attenuation in the gas-filled laser tube, and transport of the charged-particle He-3(n, p)He-3 reaction products are treated in detail. An expression for the energy density as a function of position within the tube, tube radius, operating pressure, and neutron fluence is given. The maximum energy density within the optical cavity is achieved when the tube radius is 3.26/P where P (atm) is the operating pressure. The variation of radius by 50% above and below optimum will change the energy density at most by 10%, although performance degrades quickly for radii outside this range. If the optimum tube radius is used for each operating pressure, then the power density on the centerline (kW/cu cm) is given as 9.3 x 10 to the -18th power times the operating pressure times flux in a thermal neutron environment of flux (n/sq cm sec).

Wilson, J. W.↗
NASA NTRS1980

Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

Chiang, K. T.↗
NASA NTRS1990

Selecting Modulation Indices For Telemetry And Ranging

Report describes algorithm for selection of optimum modulation indices in system for communication between ground station and spacecraft, in which ranging channel operated simultaneously with data (command and telemetry) channel. Provides for optimum division of power among data, ranging, and carrier channels and reduces degradation of performance by undesired interferences among signals.

Nguyen, Tien M.↗
NASA NTRS2011

Evaluating Suit Fit Using Performance Degradation

The Mark III suit has multiple sizes of suit components (arm, leg, and gloves) as well as sizing inserts to tailor the fit of the suit to an individual. This study sought to determine a way to identify the point an ideal suit fit transforms into a bad fit and how to quantify this breakdown using mobility-based physical performance data. This study examined the changes in human physical performance via degradation of the elbow and wrist range of motion of the planetary suit prototype (Mark III) with respect to changes in sizing and as well as how to apply that knowledge to suit sizing options and improvements in suit fit. The methods implemented in this study focused on changes in elbow and wrist mobility due to incremental suit sizing modifications. This incremental sizing was within a range that included both optimum and poor fit. Suited range of motion data was collected using a motion analysis system for nine isolated and functional tasks encompassing the elbow and wrist joints. A total of four subjects were tested with motions involving both arms simultaneously as well as the right arm only. The results were then compared across sizing configurations. The results of this study indicate that range of motion may be used as a viable parameter to quantify at what stage suit sizing causes a detriment in performance; however the human performance decrement appeared to be based on the interaction of multiple joints along a limb, not a single joint angle. The study was able to identify a preliminary method to quantify the impact of size on performance and to develop a means to gauge tolerances around optimal size. More work is needed to improve the assessment of optimal fit and to compensate for multiple joint interactions.

Margerum, Sarah E.↗
NASA NTRS2013

The Role of Model and Initial Condition Error in Numerical Weather Forecasting Investigated with an Observing System Simulation Experiment

A series of experiments that explore the roles of model and initial condition error in numerical weather prediction are performed using an observing system simulation experiment (OSSE) framework developed at the National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO). The use of an OSSE allows the analysis and forecast errors to be explicitly calculated, and different hypothetical observing networks can be tested with ease. In these experiments, both a full global OSSE framework and an 'identical twin' OSSE setup are utilized to compare the behavior of the data assimilation system and evolution of forecast skill with and without model error. The initial condition error is manipulated by varying the distribution and quality of the observing network and the magnitude of observation errors. The results show that model error has a strong impact on both the quality of the analysis field and the evolution of forecast skill, including both systematic and unsystematic model error components. With a realistic observing network, the analysis state retains a significant quantity of error due to systematic model error. If errors of the analysis state are minimized, model error acts to rapidly degrade forecast skill during the first 24-48 hours of forward integration. In the presence of model error, the impact of observation errors on forecast skill is small, but in the absence of model error, observation errors cause a substantial degradation of the skill of medium range forecasts.

Model Error↗
DOE OSTI2021

RGB wavefront sensor for turbulence mitigation

A compact adaptive optics system for long-range horizontal paths imaging that improves degraded images. The system uses a filter that corresponds to the three colors in a typical color detector element, one or more optic elements, a deformable mirror, and a detector. Focus errors, due to turbulence, in the image recorded by the detector element show up as image shifts in the three distinct color images. The shifts and statistics of these shifts between these simultaneous images are used to create control signals for the deformable mirror resulting in a compact adaptive optic system for horizontal paths without need for a point source located at the distance scene being imaged. Analysis of the relative pixel shifts in various regions of the image provides third order statistics revealing tip/tilt and additional Zernikes modes that are used to control a deformable mirror without the need for a guide star/point-source.

O'Neill, Mary Dominique↗