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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Parametric Weight Comparison of Current and Proposed Thermal Protection System (TPS) Concepts

A parametric weight assessment of advanced metallic panel, ceramic blanket, and ceramic tile thermal protection systems (TPS) was conducted using an implicit, one-dimensional (1 -D) thermal finite element sizing code. This sizing code contained models to ac- count for coatings, fasteners, adhesives, and strain isolation pads. Atmospheric entry heating profiles for two vehicles, the Access to Space (ATS) rocket-powered single-stage-to-orbit (SSTO) vehicle and a proposed Reusable Launch Vehicle (RLV), were used to ensure that the trends were not unique to a particular trajectory. Eight TPS concepts were compared for a range of applied heat loads and substructural heat capacities to identify general trends. This study found the blanket TPS concepts have the lightest weights over the majority of their applicable ranges, and current technology ceramic tiles and metallic TPS concepts have similar weights. A proposed, state-of-the-art metallic system which uses a higher temperature alloy and efficient multilayer insulation was predicted to be significantly lighter than the ceramic tile systems and approaches blanket TPS weights for higher integrated heat loads.

Myers, David E.↗
NASA NTRS2019

Evaluation Studies of a 800W Solid Oxide-Based Fuel Cells Stack for Electrical Power in Aviation

As both NASA and the aeronautics industry recognize the need for higher fuel efficiency and lower carbon emissions in both commercial airline and private aviation applications, development of all-electric or hybrid electric aircraft have garnered renewed interest in the aviation community. For the particular example of the hybrid-electric option, the solid oxide fuel cell (SOFC) is an attractive option for the power source, due to its potential to utilize aviation fuels thereby having minimal impact to aviation infrastructure. SOFC stack performance depends upon many factors, one of the most important is the way the oxidant and fuel gases are delivered to the fuel cells. System modeling of various aircraft configurations for FUELEAP (Fostering Ultra-Efficient, Low-Emitting Aviation Power) point to the need to operate SOFC stacks at high current densities. This creates challenges in the thermal profile of the stacks with potential to create large thermal gradients and hot spots. This study investigates two types of commercial solid oxide fuel cell stacks, the cross flow and co-flow gas designs, both convectively cooled with cathode air. High fuel utilization factors were also employed under varying electrical loads expected from the demands of flight. In addition, performance, range of operation and endurance were investigated under conditions of high current loads and thermal cycling. Evaluations include the study of gas kinetic using electrochemical spectroscopy. Testing took place at the facilities of NASA Glenn using a commercial test system (FuelCon AG, Magdeburg Germany). These studies are crucial to the Glenn Research Center's ability to conduct research, evaluation and development of the next-generation SOFC based stacks for cutting-edge energy technologies for aerospace applications. This study supports NASA's Convergent Aeronautics Solutions' (CAS) FUELEAP project.

Goldsby, Jon C.↗
DOE OSTI2015

WRF-Chem model predictions of the regional impacts of N 2 O 5 heterogeneous processes on night-time chemistry over north-western Europe

Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N 2 O 5 ) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem) model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonably accurate (correlations with measurements of 0.7–0.9 for NO 2 and O 3 ). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6). Sulfate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg −1 air , compared with measurements of 1.0–1.5 μg kg −1 air ). Two flights from the campaign were used as test cases – one with low relative humidity (RH) (60–70%), the other with high RH (80–90%). N 2 O 5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO 3 and N 2 O 5 . When the model failed to capture atmospheric RH correctly, the modelled NO 3 and N 2 O 5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO 3 oxidation of VOCs across the whole region was found to be 100–300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80) and comparable for dimethylsulfide (DMS). However the suppression of NO 3 mixing ratios across the domain by N 2 O 5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N 2 O 5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM 10 nitrate mass loadings remains around 5.6 μg kg −1 air , but the night-time minimum increases from 3.5 to 4.6 μg kg −1 air . The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles and will negatively impact on regional air quality, requiring this process to be included in regional models.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1985

End-wall and profile losses in a low-speed axial flow compressor rotor

The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor, is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

Lakshminarayana, B.↗
DOE OSTI2019

Magnetic and Thermal Design of HTS Quadrupole Magnet for Newly Developed Superconducting Proton Cyclotron Beam Line

A magnetic and thermal design of high-temperature superconducting (HTS) quadrupole magnet for newly developed superconducting proton cyclotron was presented in this research. With superconducting technology, the design can reduce the magnet size and remove the heat loads more efficiently. Calculations are conducted with finite element method (FEM) to study the quadrupole magnet’s magnetic and thermal properties. For the magnet cold-mass and cryostat system, the heat load is mainly generated by conduction and radiation. Multilayer thermal insulation and G10 supports are used to restrict them. The magnetic field distribution in the HTS coils is calculated to consider the critical current degradation of the YBCO tapes. The effects on the field gradient quality in relation to the pole tip profile and end chamfer are analyzed. The sixth multipole component in the integral field can be improved with end chamfer. Finally, a 20 T/m HTS quadrupole magnet with integral field uniformity less than 0.05% out to 75% of the inscribed radius is proposed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Shadow masks predictions in SPARC tokamak plasma-facing components using HEAT code and machine learning methods

Here, this work uses machine learning (ML) to complement HEAT (Heat flux Engineering Analysis Toolkit) by developing 3-D footprint surrogate models for fast and accurate heat load calculations in the divertor of the SPARC tokamak. The focus is on shadowed regions, or magnetic shadows, caused by the 3-D geometry of plasma-facing components (PFCs). ML classifiers are employed to create a surrogate model for HEAT generated shadow masks, predicting these shadow masks and divertor heat flux profiles based on a diverse range of equilibria and only the plasma current, safety factor(q95) at the edge, and magnetic flux angles as input parameters. The ultimate goal is to integrate the model for real-time control and future operational decisions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

High resolution transmission electron microscopic in-situ observations of plastic deformation of compressed nanocrystalline gold

Nanocrystalline (nc) metals possess extremely high strength, while their capability to deform plastically has been debated for decades. Low ductility has hitherto been considered an intrinsic behavior for most nc metals, due to the lack of five independent slip systems actively operating during deformation in each nanograin. Here we report in situ high resolution transmission electron microscopic (HRTEM) observations of deformation process of nc gold under compression, showing the excellent ductility of individual and aggregate nanograins. Compression causes permanent change in the profile of individual nanograins, which is mediated by dislocation slip and grain rotation. The high rate of grain boundary sliding and large extent of widely exited grain rotation may meet the boundary compatibility requirements during plastic deformation. The in situ HRTEM observations suggest that nc gold is not intrinsically brittle under compressive loading.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Pool-Based Tow System for Testing Tethered Hydrokinetic Devices Being Developed to Harvest Energy From Ocean Currents

Abstract The immense potential for ocean current energy harvesting is being actively explored as the push for renewable energy becomes more urgent. This paper demonstrates a tow testing platform built to examine and validate mathematical models related to the performance of tethered, underwater, hydrokinetic devices in development to harvest energy from ocean currents, and presents experimental results illustrating how such a system can be used. The platform has been modularly designed to allow for the testing of various tethered, underwater energy-generation systems, including kite-based systems, coaxial turbines, and duct sails. Previous research on tethered energy-generating systems has primarily been focused on airborne systems. Additionally, the limited experimental research on tethered, underwater energy-generation systems has relied on a rigid rod for mechanical and electrical connections between the test articles and instrumentation. The tow testing platform presented in this paper accomplishes the mechanical and electrical connection through a dual-function tether, featuring internal conductors and an external sheath to support towing loads. The goal of this platform was to enable the emulation of ocean currents, which are largely unidirectional, and to retrofit a regular pool into a cost-effective, adaptable, small-scale tow tank test bed. The capabilities of the system include two-way communication with tethered devices, multiple towing profiles in order to emulate different flow regimes, real-time control, and differential velocities via dual winch operation.

Engineering↗
NASA NTRS1977

Engineering analysis division internal note. OFT-1 margin assessment

The results are documented of an analysis conducted to determine space shuttle vehicle (SSV) subsystem margins for the reference flight profile for the first orbital flight test (OFT-1). In general, the results show increased margins for the OFT-1 indicators when compared to Mission 3A resutls. The inclusion of element and wing aerodynamic variations on OFT-1, in combination with winds and systems dispersions, resulted in the forward Z (FTO1) attach load indicator exceeding specified limits. The inboard and outboard elevon hinge moment margins (9 percent and 3 percent, respectively) on OFT-1 reflect values consistent with the load relief requirements dictated by elevon hinge moment variations. All other structural load indicators for OFT-1 had margins in excess of 10 percent. The SSV first stage stagnation heating indicators for OFT-1 were about 45 percent less than for Mission 3A. The hydraulic systems demands for both missions were essentially the same. The results also show OFT-1 performance requirements from the consideration of winds and dispersions to be approximately 3,300 lbs greater than Mission 3A.

Austin, L. D., Jr.↗
NASA NTRS1987

Design of the low-speed NLF(1)-0414F and the high-speed HSNLF(1)-0213 airfoils with high-lift systems

The design and testing of Natural Laminar Flow (NLF) airfoils is examined. The NLF airfoil was designed for low speed, having a low profile drag at high chord Reynolds numbers. The success of the low speed NLF airfoil sparked interest in a high speed NLF airfoil applied to a single engine business jet with an unswept wing. Work was also conducted on the two dimensional flap design. The airfoil was decambered by removing the aft loading, however, high design Mach numbers are possible by increasing the aft loading and reducing the camber overall on the airfoil. This approach would also allow for flatter acceleration regions which are more stabilizing for cross flow disturbances. Sweep could then be used to increase the design Mach number to a higher value also. There would be some degradation of high lift by decambering the airfoil overall, and this aspect would have to be considered in a final design.

Viken, Jeffrey K.↗
NASA NTRS1995

Formulation of an improved smeared stiffener theory for buckling analysis of grid-stiffened composite panels

A smeared stiffener theory for stiffened panels is presented that includes skin-stiffener interaction effects. The neutral surface profile of the skin-stiffener combination is developed analytically using the minimum potential energy principle and statics conditions. The skin-stiffener interaction is accounted for by computing the stiffness due to the stiffener and the skin in the skin-stiffener region about the neutral axis at the stiffener. Buckling load results for axially stiffened, orthogrid, and general grid-stiffened panels are obtained using the smeared stiffness combined with a Rayleigh-Ritz method and are compared with results from detailed finite element analyses.

Jaunky, Navin↗
NASA NTRS1996

Space Shuttle Hypergol Load Determination Using Nonintrusive Ultrasonic Flowmeters

Space Shuttle preflight hypergol oxidizer and fuel loading were monitored using a nonintrusive flow measurement system (NFMS) during preflight operation. A pair of 4-megahertz ultrasonic transducers measured the flow rate using a transit-time flow measurement technique. Using wireless cellular phone technology, flow-rate data was monitored and recorded. Excellent correlation was observed between the flow profiles measured using the proposed nonintrusive ultrasonic flowmeters (UFM's) and those made from conventional intrusive turbine meters (TFM). Based on the preliminary tests, it is concluded that the nonintrusive method of flow measurement has the same or higher accuracy, is simpler, and costs less than the existing TFM. Benefits of UFM's include a highly flexible, cost-effective, reliable, hazard free, and streamlined hypergol operation. Redundant installation of ultrasonic flowmeters was recommended for a few more launches prior to the replacement of the existing TFM.

Werlink, Rudolph↗
NASA NTRS2011

Active-Controlled Fluid Film Based on Wave-Bearing Technology

It has been known since 1967 that the steady-state and dynamic performance, including the stability of a wave bearing, are highly dependent on the wave amplitude. A wave-bearing profile can be readily obtained by elastically distorting the stationary bearing sleeve surface. The force that distorts the elastic sleeve surface could be an applied force or pressure. The magnitude and response of the distorting force would be defined by the relation between the bearing surface stiffness and the bearing pressure, or load, in a feedback loop controller. Using such devices as piezoelectric or other electromechanical elements, one could step control or fully control the bearing. The selection between these systems depends on the manner in which the distortion forces are applied, the running speed, and the reaction time of the feedback loop. With these techniques, both liquid- (oil-) or gas- (air-) lubricated wave bearings could be controlled. This report gives some examples of the dependency of the bearing's performance on the wave amplitude. The analysis also was proven experimentally.

Dimofte, Florin↗
NASA NTRS2018

A Common Probe Design for Multiple Planetary Destinations

Atmospheric probes have been successfully flown to planets and moons in the solar system to conduct in-situ measurements. They include the Pioneer Venus multi-probes, the Galileo Jupiter probe, and Huygens probe. Probe mission concepts to five destinations, including Venus, Jupiter, Saturn, Uranus, and Neptune, have all utilized similar-shaped aeroshells and concept of operations, namely a 45 deg sphere cone shape with high density heatshield material and parachute system for extracting the descent vehicle from the aeroshell. Each concept designed its probe to meet specific mission requirements and to optimize mass, volume, and cost. At the 2017 IPPW, NASA Headquarters postulated that a common aero-shell design could be used successfully for multiple destinations and missions. This "common probe" design could even be assembled with multiple copies, properly stored, and made available for future NASA missions, potentially realizing savings in cost and schedule and reducing the risk of losing technologies and skills difficult to sustain over decades. Thus the NASA Planetary Science Division funded a study to investigate whether a common probe design could meet most, if not all, mission needs to the five planetary destinations with extreme entry environments. The Common Probe study involved four NASA Centers and addressed these issues, including constraints and inefficiencies that occur in specifying a common design.Study methodology: First, a notional payload of instruments for each destination was defined based on priority measurements from the Planetary Science Decadal Survey. Steep and shallow entry flight path angles (EFPA) were defined for each planet based on qualification and operational g-load limits for current, state-of-the-art instruments. Interplanetary trajectories were then identified for a bounding range of EFPA. Next, 3-DoF simulations for entry trajectories were run using the entry state vectors from the interplanetary trajectories. Aeroheating correlations were used to generate stagnation point convective and radiative heat flux profiles for several aeroshell shapes and entry masses. High fidelity thermal response models for various TPS materials were used to size stagnation point thicknesses, with margins based on previous studies. Backshell TPS masses were assumed based on scaled heat fluxes from the heatshield and also from previous mission concepts.

Hwang, Helen H.↗
DOE OSTI2019

Prediction of Performance of a Pilot Scale Dual Fluidized Bed System for Chemical Looping with Oxygen Uncoupling

Chemical looping with oxygen uncoupling (CLOU) is a variant of chemical looping combustion that involves spontaneous release of gaseous oxygen in the fuel reactor, which enables efficient combustion of solid fuel char. The University of Utah has constructed a pilot-scale dual fluidized bed chemical looping process development unit (PDU) with a nominal thermal input of 200 kW. The CLOU oxygen carrier uses copper as the active metal, cycling between cupric (CuO) and cuprous (Cu2O) oxides. As an aid for design, troubleshooting and evaluation of the pilot system, a CFD model has been developed using CPFD Software’s Barracuda VR software. The 3D model includes both reactors, as well as loop seals and cyclone separators. Mechanisms describing CLOU reaction kinetics for cuprous oxide oxidation in the air reactor and cupric oxide reduction in the fuel reactor were adapted from previously done experimental work. Coal char kinetics were based on the carbon-hydrogen-nitrogen-oxygen-sulfur, CHNOS, method. Submodels for devolatilization, gasification, and homogenous gas-phase reactions used preexisting relationships in the literature. Results predict temperature profiles, concentration profiles, product gas composition, and CO¬2 capture efficiency. This paper presents results of a parametric study in which key operational variables were adjusted to determine the influence on simulated performance of the PDU. The adjusted variables include fuel feed rate, fuel particle size, total oxygen carrier inventory, oxygen carrier copper oxide loading, and oxygen carrier particle physical properties.

Reinking, Zachary↗
DOE OSTI2023

Characterizing Density and Spatial Distribution of Trap States in Ta 3 N 5 Thin Films for Rational Defect Passivation

Tantalum nitride (Ta 3 N 5 ) has gained significant attention as a potential photoanode material, yet it has been challenged by material quality issues. Defect-induced trap states are detrimental to the performance of any semiconductor material. Beyond influencing the performance of Ta 3 N 5 films, defects can also accelerate the degradation in water during desired electrochemical applications. Defect passivation has provided an enormous boost to the development of many semiconductor materials but is currently in its infancy for Ta 3 N 5 . This is in part due to a lack of experimental understanding regarding the spatial and energetic distribution of trap states throughout Ta 3 N 5 thin films. Here, we employ drive-level capacitance profiling (DLCP) to experimentally resolve the spatial and energetic distribution of trap states throughout Ta 3 N 5 thin films. The density of deeper energetic traps is found to reach ∼2.5 to 6 × 10 22 cm –3 at the interfaces of neat Ta 3 N 5 thin films, over an order of magnitude greater than the bulk. In addition to the spatial profile of deep trap states, we report neat Ta 3 N 5 thin films to be highly n-type in nature, owning a free carrier density of ∼9.74 × 10 17 cm –3 . This information, coupled with the present understanding of native oxide layers on Ta 3 N 5 , has facilitated the rational design of a targeted passivation strategy that simultaneously provides a means for catalyst immobilization. Loading catalyst via silatrane moieties suppresses the density of defects at the surface of Ta 3 N 5 thin films by two orders of magnitude, while also reducing the free carrier density of films by over one order of magnitude, effectively dedoping the films to ∼2.40 × 10 16 cm –3 . The surface passivation of Ta 3 N 5 films translates to suppressed defect-induced trapping and recombination of photoexcited carriers, as determined through absorption, photoluminescence, and transient photovoltage. Here, this illustrates how developing a deeper understanding of the distribution and influence of defects in Ta 3 N 5 thin films has the potential to guide future works and ultimately accelerate the integration and development of high-performance Ta 3 N 5 thin film devices.

defect passivation↗
NASA NTRS1944

Effect of Helicopter Performance of Modifications in Profile-Drag Characteristics of Rotor-Blade Airfoil Sections

Rough conventional, smooth conventional, and laminar-flow or low-drag sections were tested. The items covered are rotor thrust for fixed power in hovering, range and endurance at cruising speed, and power required at high-forward speed. Calculations indicated that a smooth conventional section gives marked performance gains. Smaller gains are obtainable by using a low-drag section. At high speeds or loads the low-drag section is inferior to the smooth conventional section.

Gustafson, F.B.↗
NASA NTRS2005

Lead free 0201 assembly and thermal cycle/aging reliability

The many challenges with 0201 passive component assembly can be attributed to the solder paste volume, pad design, aperture design, board finish, type of solder paste, pick-and-place, and reflow profile. A Design-of-Experiment (DOE) study was carried out to investigate the effects of these parameters on assembly defects and reliability.

isothermal aging↗