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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Stability and Control Analysis of the F-15B Quiet SpikeTM Aircraft

The primary purpose of the Quiet Spike(TradeMark) flight research program was to analyze the aerodynamic, structural, and mechanical proof-of-concept of a large multi-stage telescoping nose spike installed on the National Aeronautics and Space Administration Dryden Flight Research Center (Edwards, California) F-15B airplane. This report describes the preflight stability and control analysis performed to assess the effect of the spike on the stability, controllability, and handling qualities of the airplane; and to develop an envelope expansion approach to maintain safety of flight. The overall flight test objective was to collect flight data to validate the spike structural dynamics and loads model up to Mach 1.8. Other objectives included validating the mechanical feasibility of a morphing fuselage at operational conditions and determining the near-field shock wave characterization. The two main issues relevant to the stability and control objectives were the effects of the spike-influenced aerodynamics on the F-15B airplane flight dynamics, and the air data and angle-of-attack sensors. The analysis covered the sensitivity of the stability margins, and the handling qualities due to aerodynamic variation and the maneuvering limitations of the F-15B Quiet Spike configuration. The results of the analysis and the implications for the flight test program are also presented.

McWherter, Shaun C.↗
NASA NTRS2012

Flight Test Results on the Stability and Control of the F-15 Quiet Spike(TradeMark) Aircraft

The Quiet Spike F-15B flight research program investigated supersonic shock reduction using a 24-ft sub-scale telescoping nose boom on an F-15B airplane. The program primary flight test objective was to collect flight data for aerodynamic and structural models validation up to 1.8 Mach. Other objectives were to validate the mechanical feasibility of a morphing fuselage at the operational conditions and determine the near-field shock wave characterization. The stability and controls objectives were to assess the effect of the spike on the stability, controllability, and handling qualities of the aircraft and to ensure adequate stability margins across the entire research flight envelop. The two main stability and controls issues were the effects of the telescoping nose boom influenced aerodynamics on the F-15B aircraft flight dynamics and air data and angle of attack sensors. This paper reports on the stability and controls flight envelope clearance methods and flight test analysis of the F-15B Quiet Spike. Brief pilot commentary on typical piloting tasks, approach and landing, refueling task, and air data sensitivity to the flight control system are also discussed in this report.

Moua, Cheng M.↗
DOE OSTI2024

Fuel property evaluation of unique fatty acid methyl esters containing β-hydroxy esters from engineered microorganisms

Unique fatty acid methyl esters (FAME) containing ..beta..-hydroxy esters were produced using an engineered microorganism by glucose fermentation. This study investigated the properties of the unique FAME mixture both neat and in blends with conventional diesel, as well as properties of ..beta..-hydroxy esters. The unique FAME blend contained relatively shorter-chain FAME (average fatty acid chain carbon number 14.6) with 58 % monounsaturated fatty acids and 9 % saturated and monounsaturated ..beta..-hydroxy acid chains. The unique FAME had significantly lower distillation T90 (321 °C versus 352 °C) and higher cetane number (56.7 versus 52) compared to soy biodiesel. Cloud points were within method repeatability. Unexpectedly (because of the lack of methylene-interrupted double bonds), the unique FAME had low oxidation stability (1.5 h) as determined by Rancimat induction period. Stability could be improved through addition of commonly used antioxidants. We speculate that monounsaturated ..beta..-hydroxy FAME may be the source of this instability. Blends with conventional diesel up to 50 vol% showed similar kinematic viscosity (within method repeatability) as blends of conventional FAME. The unique FAME had no effect on distillation T90 even at the 80% blend level. A 30 vol% blend into conventional diesel had a Rancimat induction period of only 2 h, very nearly the same as the neat unique FAME sample. The addition of antioxidants produced blends of acceptable stability. Based on an assessment of the properties of individual ..beta..-hydroxy FAME molecules, they have higher boiling point, higher cloud point, lower cetane number, and potentially lower storage stability than analogous FAME not having the ..beta..-hydroxy group. Removing them from the fuel product in the production process may result in a biodiesel product with superior properties to what is on the market today.

09 BIOMASS FUELS↗
DOE OSTI2024

Porous Organic Cage Membranes for Molecular Gas Separations (Final Technical Report for DE-SC0021357)

This proposal aims at demonstrating the development of a novel family of membranes, composed of porous organic cages (POC) which offer the possibility of displaying high separation performance for challenging molecular gas separations relevant to natural gas purification, and olefin/paraffin separation. The proposed POCs synthesized in membrane form will display the most desirable properties of polymers (facile processability and flexibility) and inorganic materials (hierarchically ordered pores with molecular sieving properties) leading to highly selective and permeable membranes. POCs should display distinctive structural, compositional, adsorption and transport properties than those of conventional porous materials, opening the doors for a new research direction in membrane science, and gas separations. Our preliminary results demonstrate the feasibility of preparing POC crystals with controlled size, and continuous POC membranes with remarkable high permeances, and separation ability for CO 2 /CH 4 , N 2 /CH 4 and C 3 H 6 /C 3 H 8 separations serving as a solid foundation for our proposed work. Fundamentally, this proposal aims at elucidating separation mechanisms of different gas mixtures related to natural gas composition, and olefin/paraffin separation over porous organic cage membranes. The proposed research will result in fundamental understanding of adsorption and transport properties of industrially relevant gas molecules through novel microporous membranes, and may lead to the development of a cost effective membrane technology for natural gas purification, and olefin/paraffin separation surpassing the conventional benchmark technology distillation. Furthermore, we aim at demonstrating selective water transport through POC membranes, which can be positively impactful in numerous industrial applications in which water is present. The ability to fabricate thin, chemically and mechanically stable POC membranes for societal relevant gas separations constitute a new and distinctive direction in membrane science. Our proposed work aims at addressing some of the challenges recognized in the Research Agenda for Transforming Separation Science . Specifically: (a) advancing understanding of complex mixtures on separation performance; (b) exploring thermodynamic and kinetic mechanisms through the elucidation of separation mechanisms, and (c) study potential stability issues of the membranes to be assessed by evaluating the long term membrane stability and performance at various temperatures and pressures. The team is uniquely qualified to execute the proposed work. The PI has solid expertise in the rational molecular engineering design of porous crystalline membranes for molecular gas separations. The PNNL collaborator has extensive experience in the synthesis, characterization, and functional applications of microporous crystals, with particular emphasis on gas adsorption.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Dynamics and Adaptive Control for Stability Recovery of Damaged Aircraft

This paper presents a recent study of a damaged generic transport model as part of a NASA research project to investigate adaptive control methods for stability recovery of damaged aircraft operating in off-nominal flight conditions under damage and or failures. Aerodynamic modeling of damage effects is performed using an aerodynamic code to assess changes in the stability and control derivatives of a generic transport aircraft. Certain types of damage such as damage to one of the wings or horizontal stabilizers can cause the aircraft to become asymmetric, thus resulting in a coupling between the longitudinal and lateral motions. Flight dynamics for a general asymmetric aircraft is derived to account for changes in the center of gravity that can compromise the stability of the damaged aircraft. An iterative trim analysis for the translational motion is developed to refine the trim procedure by accounting for the effects of the control surface deflection. A hybrid direct-indirect neural network, adaptive flight control is proposed as an adaptive law for stabilizing the rotational motion of the damaged aircraft. The indirect adaptation is designed to estimate the plant dynamics of the damaged aircraft in conjunction with the direct adaptation that computes the control augmentation. Two approaches are presented 1) an adaptive law derived from the Lyapunov stability theory to ensure that the signals are bounded, and 2) a recursive least-square method for parameter identification. A hardware-in-the-loop simulation is conducted and demonstrates the effectiveness of the direct neural network adaptive flight control in the stability recovery of the damaged aircraft. A preliminary simulation of the hybrid adaptive flight control has been performed and initial data have shown the effectiveness of the proposed hybrid approach. Future work will include further investigations and high-fidelity simulations of the proposed hybrid adaptive Bight control approach.

Nguyen, Nhan↗
NASA NTRS2022

An Assessment of SNPP and NOAA20 VIIRS RSB Calibration Performance in NASA SIPS Reprocessed Collection-2 L1B Data Products

Two VIIRS sensors onboard the SNPP and NOAA20 satellites have been successfully operating for over 10 and 4 years, respectively, providing the worldwide user community with high-quality imagery and radiometric measurements of the land, atmosphere, cryosphere, and oceans. This study provides a temporal radiometric stability and calibration consistency assessment of the SNPP and NOAA20 VIIRS reflective solar bands using the latest NASA SIPS C2 L1B products. Several independent vicarious approaches are used to examine the stability of SNPP VIIRS and consistency of the at-sensor reflectance between the two VIIRS instruments. These approaches include observations from simultaneous nadir overpasses, the Libya-4 desert and Dome C snow/ice sites, and deep convective clouds. The impact of existing band spectral differences on the reflectance measurements is accounted for utilizing scene-specific hyperspectral observations provided by the SCIAMACHY sensor onboard the ENVISAT platform. Results indicate that both SNPP and NOAA20 VIIRS reflectances are stable within 1% over their mission periods for all bands, except for a few bands in the visible range from SNPP VIIRS that show more upward drifts at high radiances. NOAA20 VIIRS reflectances are systematically lower than SNPP by 2 to 4% for most bands, with the exception of few short wavelength bands where it is seen to be up to 7%.

VIIRS↗
DOE OSTI2025

Navigating thermal stability intricacies of high-nickel cathodes for high-energy lithium batteries

High-nickel oxide cathodes, LiNi x M 1−x O 2 (x ≥ 0.8), are preferred in automotive lithium batteries, but they face thermal instability challenges. Inconsistent literature reports and unstandardized testing protocols further complicate quantitative assessments of the thermal stability of these cathodes. Here, we present here a statistical thermal analysis based on the differential scanning calorimetry measurements of 15 representative cathode materials with different compositions, morphologies and states of charge. The findings reveal that each cathode has a critical state of charge that defines its safe operating limit, which is affected by the metal–oxygen bond strength and surface reactivity. The thermal runaway temperature is dictated by the layered Li 1−x NiO 2 to LiNi 2 O 4 spinel-like phase transition, which is thermodynamically determined by the metal–oxygen bond covalency and kinetically influenced by the cation mixing and particle size. Raman spectroscopy is used to predict the thermal runaway temperature on the basis of the linear relationship between them. Finally, we propose a thermal stability index to quantify cathode thermal stability as a guide for developing safer high-nickel cathodes.

batteries↗
DOE OSTI2022

Community stability is related to animal diversity change

Abstract Understanding the drivers of community stability in times of increasing anthropogenic pressure is an urgent issue. Biodiversity is known to promote community stability, but studies of the biodiversity–stability relationship rarely consider the full complexity of biodiversity change. Furthermore, finding generalities that hold across taxonomic groups and spatial and temporal scales remains challenging because most investigations have narrow taxonomic, spatial, and temporal scopes. We used organismal data collected through the National Ecological Observatory Network (NEON) at sites across the contiguous United States to evaluate linkages between community stability and biodiversity change for four taxonomic groups: small mammals, ground beetles, fish, and freshwater macroinvertebrates. We defined community stability as constancy of aggregate species' abundance. We quantified change in biodiversity as (1) dissimilarity in community taxonomic and functional composition and species replacement and richness change components of that dissimilarity and (2) change in species' abundance distributions as captured by change in species rank, richness, and evenness. We found that community stability increased with species replacement and with contribution of species replacement to overall dissimilarity for all taxonomic groups, but declined with increasing change in species richness and evenness. This is consistent with the notion that temporal fluctuations in species abundance can help stabilize community properties. We also found that community stability was highest when change in community functional composition was either lower or higher than expected given reshuffling of each community's taxonomic composition. This suggests that long‐term community stability can result from fluctuations of functionally similar species in assemblages with high taxonomic reshuffling. On the contrary, the functional uniqueness of fluctuating species compensates for lower taxonomic reshuffling to drive stabilization of community properties. Our study provides an initial assessment of the relationship between community stability and biodiversity change and illustrates the utility of fine temporal resolution data collected across ecosystems and biomes to understand the general mechanisms underlying biodiversity–stability relationships.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1978

Blade row dynamic digital compression program. Volume 2: J85 circumferential distortion redistribution model, effect of Stator characteristics, and stage characteristics sensitivity study

The results of dynamic digital blade row compressor model studies of a J85-13 engine are reported. The initial portion of the study was concerned with the calculation of the circumferential redistribution effects in the blade-free volumes forward and aft of the compression component. Although blade-free redistribution effects were estimated, no significant improvement over the parallel-compressor type solution in the prediction of total-pressure inlet distortion stability limit was obtained for the J85-13 engine. Further analysis was directed to identifying the rotor dynamic response to spatial circumferential distortions. Inclusion of the rotor dynamic response led to a considerable gain in the ability of the model to match the test data. The impact of variable stator loss on the prediction of the stability limit was evaluated. An assessment of measurement error on the derivation of the stage characteristics and predicted stability limit of the compressor was also performed.

Tesch, W. A.↗
DOE OSTI2020

Generation of localized lower-hybrid current drive by temperature perturbations

Despite high demonstrated efficiency, lower-hybrid current drive (LHCD) has not been considered localized enough for neoclassical tearing mode (NTM) stabilization in tokamaks. This assessment must be reconsidered in view of the radiofrequency current condensation effect. Here we show that an island with a central hot spot induces significant localization of LHCD. Furthermore, in steady state tokamaks where a significant amount of current is provided by LHCD, passive stabilization of NTMs may occur automatically, particularly as islands become large, without requiring precise aiming of the wave power.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1988

Radio reference frame stability from VLBI data

Intercontinental radio interferometric measurements between NASA's Deep Space Network stations yield a catalog of positions of 106 extragalactic radio sources, uniformly distributed between -45 and +85 deg declination. Almost all of the source positions have formal uncertainties between 0.5 and 3 milliarcseconds. Estimates of three independent sets of 32 source coordinates at average epochs 1980.0, 1983.2, and 1984.5 assess the level of stability of the reference frame over a five-year period. Comparisons of the three sets of source coordinates show a number of cases of greater than 2 sigma differences, particularly between the 1984-85 and 1981-83 periods. No sources, however, show 2 sigma shifts among both pairs of epochs. Upper limits of the order of 1 mas/yr can be placed on the time rates of change of the 32 source coordinates.

Sovers, O. J.↗
NASA NTRS1984

Flight investigation of various control inputs intended for parameter estimation

NASA's F-8 digital fly-by-wire aircraft has been subjected to stability and control derivative assessments, leading to the proposal of improved control inputs for more efficient control derivative estimation. This will reduce program costs by reducing flight test and data analysis requirements. Inputs were divided into sinusoidal types and cornered types. Those with corners produced the best set of stability and control derivatives for the unaugmented flight control system mode. Small inputs are noted to have provided worse derivatives than larger ones.

Shafer, M. F.↗
DOE OSTI2022

Determining the Role of Synthesis and Reaction Conditions on the Exposed Surface and Shape of ..beta..-Mo2C Catalysts

The production of drop-in quality biofuels typically can be achieved through catalytic fast pyrolysis (CFP) of biomass, followed by hydrodeoxygenation (HDO) of the vapor-phase product to reduce the oxygen content and stabilize the bio-oil product. To favor selectivity toward desired deoxygenation products, bifunctional catalysts with both acidic and hydrogenation sites are often employed. Due to both its oxophilicity and its ability to promote hydrogenation reactions, molybdenum carbide catalysts have shown promise for promoting the HDO of CFP vapors. However, the surface structure and composition of carbide catalyst particles are not well understood, precluding the establishment of fundamental structure-function relationships needed for the rational development of molybdedum carbide for HDO, as well as other reactions. For orthorhombic ..beta..-Mo2C, the (100) facet is largely studied for computational surface-reaction analyses, possibly due to its similarities with the close-packed (111) facet of noble-metal catalysts. However, it has previously been postulated through ab initio thermodynamic studies that the (111), (110), and (011) facets are most stable, though there is no consensus. Furthermore, while a majority of previous surface stability analyses of ..beta..-Mo2C focus on bulk terminations, the highly carburizing synthesis conditions and the use of ..beta..-Mo2C in carbon-containing reaction applications could introduce non-stoichiometric coverages of surface carbon. As such, this study uses ab initio thermodynamics calculations to assess the relative surface stability of the low-index facets of ..beta..-Mo2C, including consideration of varying the coverage of surface carbon. From this information, Wulff constructions are utilized to predict the synthesis and reaction condition-dependent shape and surface carbon composition of ..beta..-Mo2C catalyst particles.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗
NASA NTRS1993

On the stability of nongyrotropic ion populations - A first (analytic and simulation) assessment

The wave and dispersion equations for perturbations propagating parallel to an ambient magnetic field in magnetoplasmas with nongyrotropic ion populations show, in general, the occurrence of coupling between the parallel (left- and right-hand circularly polarized electromagnetic and longitudinal electrostatic) eigenmodes of the associated gyrotropic medium. These interactions provide a means to driving linearly one mode with free-energy sources of other modes in homogeneous media. Different types of nongyrotropy bring about distinct classes of coupling. The stability of a hydrogen magnetoplasma with anisotropic, nongyrotropic protons that only couple the electromagnetic modes to each other is investigated analytically (via solution of the derived dispersion equation) and numerically (via simulation with a hybrid code). Nongyrotropy enhances growth and enlarges the unstable spectral range relative to the corresponding gyrotropic situation. The relevance of the properties of nongyrotropic populations to space plasma environments is also discussed.

Brinca, A. L.↗
DOE OSTI2021

Materials design of sodium chloride solid electrolytes Na3MCl6 for all-solid-state sodium-ion batteries

All-solid-state sodium-ion batteries have attracted increasing attention owing to the low cost of sodium and the enhanced safety compared to conventional Li-ion batteries. Recently, halides have been considered as promising solid electrolytes (SEs) due to their favorable combination of high ionic conductivity and chemical stability against high-voltage cathode materials. Although a wide variety of lithium chloride SEs, Li 3 MCl 6 , have been developed for high-voltage all-solid-state batteries, only a limited number of sodium chloride SEs have been reported. This study aims to offer a material design insight for the development of sodium chloride SEs through systematic assessment of the phase stability, electrochemical stability, and transport properties of novel Na 3 MCl 6 SEs. Structural calculations indicate that Na 3 MCl 6 exhibits trigonal $P\bar{3}$1c, monoclinic P2 1 /n, and trigonal $R\bar{3}$ phases, and the stable phase of Na 3 MCl 6 is dependent on the type and ionic radius of M. Na 3 MCl 6 typically exhibits a high oxidation potential, demonstrating good electrochemical stability against cathodes. The bond-valence site energy and ab initio molecular dynamics calculations revealed that Na 3 MCl 6 with P2 1 /n and $R\bar{3}$ phases showed low ionic conductivity, while the $P\bar{3}$1c phase slightly improved the ionic conductivity of Na 3 MCl 6 . The formation of Na vacancies by aliovalent substitution considerably increased the ionic conductivity up to four orders of magnitude for pristine Na 3 MCl 6 , exhibiting ~10 –5 S cm –1 for trigonal $P\bar{3}$1c and $R\bar{3}$ phases. The formation of defects could further enhance the ionic conductivity of Na 3 MCl 6 , and the optimization of defect type and ratio can be helpful in developing superionic Na chloride SEs. The material design of Na 3 MCl 6 in this study will provide fundamental guidelines for the development of novel sodium halide SEs for all-solid-state sodium-ion batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2014

The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems

Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.

Ceramic Matrix Composites↗
NASA NTRS2005

DEVELOPMENT OF AN INFLIGHT COUNTERMEASURE TO MITIGATE POSTFLIGHT GAIT DYSFUNCTION

Following spaceflight crewmembers experience gait and postural instabilities due to inflight adaptive alterations in sensorimotor function. These changes can pose a risk to crew safety if nominal or emergency vehicle egress is required immediately following long-duration spaceflight. At present, no operational countermeasure is available to mitigate postflight locomotor disturbances. Therefore, the goal of this study is to develop an inflight training regimen that facilitates the recovery of locomotor function after long-duration spaceflight. The countermeasure we are developing is based on the concept of variable practice. During this type of training the subject gains experience producing the appropriate adaptive motor behavior under a variety of sensory conditions and response constraints. This countermeasure is built around current ISS treadmill exercise activities. Crewmembers will conduct their nominal inflight treadmill exercise while being exposed to variations in visual flow patterns. These variations will challenge the postural and locomotor systems repeatedly, thereby promoting adaptive reorganization in locomotor behavior. As a result of this training a subject learns to solve a class of motor problems, rather than a specific motor solution to one problem, Le., the subject learns response generalizability or the ability to "learn to learn" under a variety of environmental constraints. We anticipate that this training will accelerate recovery of postural and locomotor function during readaptation to gravitational environments following spaceflight facilitating neural adaptation to unit (Earth) and partial (Mars) gravity after long-duration spaceflight. The study calls for one group of subjects to perform the inflight treadmill training regimen while a control group of subjects performs only the nominal exercise procedures. Locomotor function in both groups is assessed before and after spaceflight using two tests of gait function: The Integrated Treadmill Locomotion Test (ITLT) and the Functional Mobility Test (FMT). The ITLT characterizes alterations in the integrated function of multiple sensorimotor subsystems responsible for the control of locomotion. This test calls for subjects to walk on a motorized treadmill while we assess changes in dynamic postural stability, head-trunk coordination, short-latency head stabilization responses, dynamic visual acuity, lower limb coordination strategies and gait cycle timing. To make these assessments we measure the following parameters while subjects walk on the treadmill: 1) full body 3-dimensional kinematics using a motion capture system (Motion Analysis Corp., Santa Rosa, CA); 2) the shock-wave transmitted from heel-strike to the head using triaxial accelerometers placed on the tibia and head (Entran, Fairfield, NJ); 3) vertical forces using an instrumented treadmill (Kistler Instrument Corp., Amherst, NY); 4) Dynamic visual acuity using Landolt Cs presented on a laptop computer located 4m from the eyes and 5) Gait cycle timing using foot-switches (Motion Lab Systems, Inc., Baton Rouge, LA) attached to the plantar surface of each shoe at the heel and toe. The FMT evaluates a subject's ability to perform challenging locomotor maneuvers similar to those encountered during an egress from a space vehicle. Subjects step over and duck under obstacles along with negotiating a series of pylons set up on a base of 10 cm thick medium density foam. The dependent measures for the FMT are time to complete the course and the number of obstacles touched. To date, we have collected pre and postflight locomotion data from Expeditions 5-9 who will serve as part of the control group for this study. Preliminary results comparing the recovery rates in gait control sub-systems obtained from the ITLT and FMT performance showed two recovery patterns: 1) a concordant recovery trend between gait control parameters and FMT performance indicating a restitution pattern of recovery and 2) gait controecovery that lagged recovery in FMT performance suggesting that improvement in locomotor function was attained through a pattern of substitution. These data suggest that recovery of postflight locomotor function may occur through adaptive mechanisms that lead to either restitution or substitution of function. Understanding the modes of postflight readaptation has implications for countermeasure development and testing and in astronaut postflight rehabilitation.

Bloomberg, J. J.↗