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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 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Application of an efficient generator-coordinate subspace-selection algorithm to neutrinoless double- β decay

The generator coordinate method begins with the variational construction of a set of nonorthogonal mean-field states that span a subspace of the full many-body Hilbert space. These states are then often projected onto states with good quantum numbers to restore symmetries, leading to a set with members that can be similar to one another, and it is sometimes possible to reduce this set without greatly affecting results. Here, we propose a greedy algorithm that we call the energy-transition-orthogonality procedure (ENTROP) to select subsets of important states. As applied here, the approach selects on the basis of diagonal energy, orthogonality, and contribution to the matrix element that governs neutrinoless double-β decay. We present both shell-model and preliminary ab initio calculations of this matrix element for the decay of 76Ge, with quadrupole deformation parameters and the isoscalar pairing strength as generator coordinates. ENTROP converges quickly, reducing significantly the number of basis states needed for an accurate calculation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1977

In-flight gyro drift rate calibration on the Viking Orbiters

The drift rates of the attitude control gyros onboard the Viking Orbiters were calibrated several times during flight. The calibration was performed by engaging the gyro control of attitude for a six-hour period, recording the Viking Orbiter coordinates of the sun and the roll reference star as a function of time, and processing these data by a computer program. The computer program calculated drift rates for each data increment, and then smoothed the calculated rate versus the time function for all the data on the basis of a Gauss-Markov gyro-drift model. The effects of data noise were minimized by using a relatively long time constant in the Gauss-Markov model and by empirically determining a set of corrections for celestial inertial scale factor error differences. In this way the rms error of the data fit was lessened.

Breckenridge, W. G.↗
NASA NTRS1980

Regional analysis of earthquake occurrence and seismic energy release

The historic temporal variation in earthquake occurrence and seismic energy release on a regional basis throughtout the world were studied. The regionalization scheme employed divided the world into large areas based either on seismic and tectonic considerations (Flinn-Engdahl Scheme) or geographic (longitude and latitude) criteria. The data set is the wide earthquake catalog of the National Geophysical Solar-Terrestrial Data Center. An apparent relationship exists between the maximum energy released in a limited time within a seismic region and the average or background energy per year averaged over a long time period. In terms of average or peak energy release, the most seismic regions of the world during the 50 to 81 year period ending in 1977 were Japanese, Andean South American, and the Alaska-Aleutian Arc regions. The year to year fluctuations in regional seismic energy release are greater, by orders of magnitude, than the corresponding variations in the world-wide seismic energy release. The b values of seismic regions range from 0.7 to 1.4 where earthquake magnitude is in the range 6.0 to 7.5.

Cohen, S. C.↗
NASA NTRS1990

Robust eigensystem assignment for second-order estimators

An approach for the robust eigensystem assignment of flexible structures using full state or output feedback is developed. Using the second-order dynamic equations, the approach can assign the eigenvalues of the system via velocity and displacement feedbacks, or acceleration and velocity feedbacks. The eigenvalues and eigenvectors of the system are assigned, via the second-order eigenvalue problem for the structural system, in two steps. First, an orthonormal basis spanning the attainable closed-loop eigenvector space corresponding to each desired closed-loop eigenvalue is generated using the Singular Value or QR decompositions. Second, a sequential procedure is used to choose a set of closed-loop eigenvectors that are as close as possible to the column space of a well-conditioned target matrix. Among the possible choices of the target matrix, the closest unitary matrix to the open-loop eigenvector matrix appears to be a suitable choice. A numerical example is given to illustrate the proposed algorithm.

Juang, Jer-Nan↗
NASA NTRS1990

Robust eigensystem assignment for second-order dynamic systems

A novel approach for the robust eigensystem assignment of flexible structures using full state or output feedback is developed. Using the second-order dynamic equations, the approach can assign the eigenvalues of the system via velocity and displacement feedbacks, or acceleration and velocity feedbacks. The eigenvalues and eigenvectors of the system are assigned, via the second-order eigenvalue problem for the structural system, in two steps. First, an orthonormal basis spanning the attainable closed-loop eigenvector space corresponding to each desired closed-loop eigenvalue is generated using the Singular Value or QR decompositions. Second, a sequential procedure is used to choose a set of closed-loop eigenvectors that are as close as possible to the column space of a well-conditioned target matrix. Among the possible choices of the target matrix, the closest unitary matrix to the open-loop eigenvector matrix appears to be a suitable choice. A numerical example is given to illustrate the proposed algorithm.

Juang, Jer-Nan↗
NASA NTRS1991

Space radiation health program plan

The Space Radiation Health Program intends to establish the scientific basis for the radiation protection of humans engaged in the exploration of space, with particular emphasis on the establishment of a firm knowledge base to support cancer risk assessment for future planetary exploration. This document sets forth the technical and management components involved in the implementation of the Space Radiation Health Program, which is a major part of the Life Sciences Division (LSD) effort in the Office of Space Science and Applications (OSSA) at the National Aeronautics and Space Administration (NASA). For the purpose of implementing this program, the Life Sciences Division supports scientific research into the fundamental mechanisms of radiation effects on living systems and the interaction of radiation with cells, tissues, and organs, and the development of instruments and processes for measuring radiation and its effects. The Life Sciences Division supports researchers at universities, NASA field centers, non-profit research institutes and national laboratories; establishes interagency agreements for cooperative use and development of facilities; and conducts a space-based research program using available and future spaceflight vehicles.

Source record↗
NASA NTRS1994

Guidelines for lighting of plants in controlled environments

These guidelines for lighting of plants, established by the organizing committee, provided a focus for the discussions at the workshop. The guidelines served as a basis for discussion amongst the workshop attendees and led to a number of recommendations that were recorded by the session chairpersons. The organizing committee indicated they would incorporate the recommendations and suggestions into a revised set of guidelines for additional discussion. It was understood that these guidelines will not be standards and will require upgrading and modifications as lamps and equipment become available and as new insights are obtained on plants' response to light. Revised draft guidelines are included as Tables 1 and 2 that have been developed by the organizing committee following the suggestions obtained at the workshop. The guidelines for growth chambers are in Table 1 and guideines for greenhouses are given in Table 2. These have been distributed to the participants who indicated a willingness to review proposals that were developed. It is hoped that these proposals will lead to the development of guidelines that will have general acceptance by plant scientists.

Dietzer, Gerald↗
NASA NTRS2008

Scheme for Quantum Computing Immune to Decoherence

A constructive scheme has been devised to enable mapping of any quantum computation into a spintronic circuit in which the computation is encoded in a basis that is, in principle, immune to quantum decoherence. The scheme is implemented by an algorithm that utilizes multiple physical spins to encode each logical bit in such a way that collective errors affecting all the physical spins do not disturb the logical bit. The scheme is expected to be of use to experimenters working on spintronic implementations of quantum logic. Spintronic computing devices use quantum-mechanical spins (typically, electron spins) to encode logical bits. Bits thus encoded (denoted qubits) are potentially susceptible to errors caused by noise and decoherence. The traditional model of quantum computation is based partly on the assumption that each qubit is implemented by use of a single two-state quantum system, such as an electron or other spin-1.2 particle. It can be surprisingly difficult to achieve certain gate operations . most notably, those of arbitrary 1-qubit gates . in spintronic hardware according to this model. However, ironically, certain 2-qubit interactions (in particular, spin-spin exchange interactions) can be achieved relatively easily in spintronic hardware. Therefore, it would be fortunate if it were possible to implement any 1-qubit gate by use of a spin-spin exchange interaction. While such a direct representation is not possible, it is possible to achieve an arbitrary 1-qubit gate indirectly by means of a sequence of four spin-spin exchange interactions, which could be implemented by use of four exchange gates. Accordingly, the present scheme provides for mapping any 1-qubit gate in the logical basis into an equivalent sequence of at most four spin-spin exchange interactions in the physical (encoded) basis. The complexity of the mathematical derivation of the scheme from basic quantum principles precludes a description within this article; it must suffice to report that the derivation provides explicit constructions for finding the exchange couplings in the physical basis needed to implement any arbitrary 1-qubit gate. These constructions lead to spintronic encodings of quantum logic that are more efficient than those of a previously published scheme that utilizes a universal but fixed set of gates.

Williams, Colin↗
NASA NTRS2012

Preliminary Aerodynamic Investigation of Fan Rotor Blade Morphing

Various new technologies currently under development may enable controlled blade shape variability, or so-called blade morphing, to be practically employed in aircraft engine fans and compressors in the foreseeable future. The current study is a relatively brief, preliminary computational fluid dynamics investigation aimed at partially demonstrating and quantifying the aerodynamic potential of fan rotor blade morphing. The investigation is intended to provide information useful for near-term planning, as well as aerodynamic solution data sets that can be subsequently analyzed using advanced acoustic diagnostic tools, for the purpose of making fan noise comparisons. Two existing fan system models serve as baselines for the investigation: the Advanced Ducted Propulsor fan with a design tip speed of 806 ft/sec and a pressure ratio of 1.294, and the Source Diagnostic Test fan with a design tip speed of 1215 ft/sec and a pressure ratio of 1.470. Both are 22-in. sub-scale, low-noise research fan/nacelle models that have undergone extensive experimental testing in the 9- by 15-foot Low Speed Wind Tunnel at the NASA Glenn Research Center. The study, restricted to fan rotor blade morphing only, involves a fairly simple blade morphing technique. Specifically, spanwise-linear variations in rotor blade-section setting angle are applied to alter the blade shape; that is, the blade is linearly retwisted from hub to tip. Aerodynamic performance comparisons are made between morphed-blade and corresponding baseline configurations on the basis of equal fan system thrust, where rotor rotational speed for the morphed-blade fan is varied to change the thrust level for that configuration. The results of the investigation confirm that rotor blade morphing could be a useful technology, with the potential to enable significant improvements in fan aerodynamic performance. Even though the study is very limited in scope and confined to simple geometric perturbations of two existing fan systems, the aerodynamic effectiveness of blade morphing is demonstrated by the configurations analyzed. In particular, for the Advanced Ducted Propulsor fan it is demonstrated that the performance levels of the original variable-pitch baseline design can be achieved using blade morphing instead of variable pitch, and for the Source Diagnostic Test fan the performance at important off-design operating points is substantially increased with blade morphing.

Tweedt, Daniel L.↗
NASA NTRS2013

Orion MPCV Touchdown Detection Threshold Development and Testing

A robust method of detecting Orion Multi ]Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post ]landing segment of the Flight Software (FSW). The vehicle crew is the prime input for touchdown detection, followed by an autonomous FSW algorithm, and finally a strictly time based backup timer. RCS thrusters must be inhibited before submersion in water to protect against possible damage due to firing these jets under water. In addition, neglecting to declare touchdown will not allow the vehicle to transition to post ]landing activities such as activating the Crew Module Up ]righting System (CMUS), resulting in possible loss of communication and difficult recovery. A previous AIAA paper gAssessment of an Automated Touchdown Detection Algorithm for the Orion Crew Module h concluded that a strictly Inertial Measurement Unit (IMU) based detection method using an acceleration spike algorithm had the highest safety margins and shortest detection times of other methods considered. That study utilized finite element simulations of vehicle splashdown, generated by LS ]DYNA, which were expanded to a larger set of results using a Kriging surface fit. The study also used the Decelerator Systems Simulation (DSS) to generate flight dynamics during vehicle descent under parachutes. Proto ]type IMU and FSW MATLAB models provided the basis for initial algorithm development and testing. This paper documents an in ]depth trade study, using the same dynamics data and MATLAB simulations as the earlier work, to further develop the acceleration detection method. By studying the combined effects of data rate, filtering on the rotational acceleration correction, data persistence limits and values of acceleration thresholds, an optimal configuration was determined. The lever arm calculation, which removes the centripetal acceleration caused by vehicle rotation, requires that the vehicle angular acceleration be derived from vehicle body rates, necessitating the addition of a 2nd order filter to smooth the data. It was determined that using 200 Hz data directly from the vehicle IMU outperforms the 40 Hz FSW data rate. Data persistence counter values and acceleration thresholds were balanced in order to meet desired safety and performance. The algorithm proved to exhibit ample safety margin against early detection while under parachutes, and adequate performance upon vehicle splashdown. Fall times from algorithm initiation were also studied, and a backup timer length was chosen to provide a large safety margin, yet still trigger detection before CMUS inflation. This timer serves as a backup to the primary acceleration detection method. Additionally, these parameters were tested for safety on actual flight test data, demonstrating expected safety margins.

Daum, Jared↗
NASA NTRS2015

SimSup's Loop: A Control Theory Approach to Spacecraft Operator Training

Immersive simulation is a staple of training for many complex system operators, including astronauts and ground operators of spacecraft. However, while much has been written about simulators, simulation facilities, and operator certification programs, the topic of how one develops simulation scenarios to train a spacecraft operator is relatively understated in the literature. In this paper, an approach is presented for using control theory as the basis for developing the immersive simulation scenarios for a spacecraft operator training program. The operator is effectively modeled as a high level controller of lower level hardware and software control loops that affect a select set of system state variables. Simulation scenarios are derived from a STAMP-based hazard analysis of the operator's high and low level control loops. The immersive simulation aspect of the overall training program is characterized by selecting a set of scenarios that expose the operator to the various inadequate control actions that stem from control flaws and inadequate control executions in the different sections of the typical control loop. Results from the application of this approach to the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission are provided through an analysis of the simulation scenarios used for operator training and the actual anomalies that occurred during the mission. The simulation scenarios and inflight anomalies are mapped to specific control flaws and inadequate control executions in the different sections of the typical control loop to illustrate the characteristics of anomalies arising from the different sections of the typical control loop (and why it is important for operators to have exposure to these characteristics). Additionally, similarities between the simulation scenarios and inflight anomalies are highlighted to make the case that the simulation scenarios prepared the operators for the mission.

LADEE↗
DOE OSTI2023

Summary Analysis of Different Offshore Wind Capacity Density Drivers in Proposed U.S. Projects and Impacts on Progress Towards State and Federal Deployment Targets

Understanding the density of offshore wind development - or the "capacity density" - is important for state and federal offshore wind planning efforts and to track progress towards policy goals. NREL has traditionally assumed a capacity density of 3 megawatts per square kilometer (MW/km2) when estimating the U.S. project pipeline (Musial et al. 2022), but capacity densities for existing European offshore wind farms ranged from 2-19 MW/km2 (Borrmann et al. 2018). We track the expected capacity densities of the proposed U.S. projects in the East Coast and make an analysis by state and by developer to identify what are the capacity density norms in the industry and whether the state in which the development efforts are taking place has some impact on capacity density. We also analyze the effects of the area occupied by station keeping systems on capacity density for lease areas dedicated to floating projects and provide a list of main capacity density drivers. This summary analysis sets a baseline to study how different capacity density drivers could impact the progress towards state and federal deployment targets. Given the currently delineated Renewable Energy Areas in the Outer Continental Shelf (OCS) and the basis from the summary analysis, we estimate the expected offshore wind deployment over time federally and by state and compare it to the state and federal deployment targets. The proposed analysis helps identify gaps and needs to meet state and federal targets, which provides sufficient information to propose strategic supply chain and policy planning with the objective of meeting deployment goals.

capacity density↗
NASA NTRS1990

The Chemical Basis for the Origin of the Genetic Code and the Process of Protein Synthesis

A model for the origin of protein synthesis. The essential features of the model are that 5'-AMP and perhaps other monoribonucleotides can serve as catalysts for the selective synthesis of L-based peptides. A unique set of characteristics of 5'-AMP is responsible for the selective catalysts and these characteristics are described in detail. The model involves the formation of diesters as intermediates and selectivity for use of the L-isomer occurs principally at the step of forming the diester. However, in the formation of acetyl phenylalanine-AMP monoester there is a selectivity for esterification by the D-isomer. Data showing this selectivity is presented. This selectivity for D-isomer disappears after the first step. The identity was confirmed of all four of possible diesters of acetyl-D- and -L phenylaline with 5'-AMP by nuclear magnetic resonance (NMR). The data using flourescence and NMR show the Trp ring can associate with the adenine ring more strongly when the D-isomer is in the 2' position than it can when in the 3' position. These same data also suggest a molecular mechanisim for the faster esterificaton of 5'-AMP by acetyl-D-phenylaline. Some new data is also presented on the possible structure of the 2' isomer of acetyl-D-tryptophan-AMP monoester. The HPLC elution times of all four possible acetyl diphenylalanine esters of 5'-AMP were studied, these peptidyl esters will be products in the studies of peptide formation on the ribose of 5'-AMP. Other studies were on the rate of synthesis and the identity of the product when producing 3'Ac-Phe-2'tBOC-Phe-AMP diester. HPLC purification and identification of this product were accomplished.

Lacey, James C., Jr.↗
DOE OSTI2020

Nuclear Canister Corrosion Detection

The software titled "nccd" is used for running residual neural networks (ResNets) on images of nuclear canisters. The software provides only the code for the implementation (based on the fastai library), but it does not share the image data. The compute code allows the use of residual nets (and more generally of other deep learning models) for classifying images from nuclear canisters as corroded. or intact. An image is considered to be corroded if it contains pitting or stress corrosion cracks. The code trains ResNets on image tiles extracted from original images from nuclear canisters, and then implements a classification rule, which can be applied to a validation set to decide if each original image is corroded or intact. The software automates the process of using images taken from nuclear canisters to detect corrosion. It provides also scope for future research directions on the basis of the existing research and code.

Papamarkou, Theodore↗
NASA NTRS1976

Application of LANDSAT system for improving methodology for inventory and classification of wetlands

The author has identified the following significant results. A newly developed software system for generating statistics on surface water features was tested using LANDSAT data acquired previous to 1975. This software test provided a satisfactory evaluation of the system and also allowed expansion of data base on prairie water features. The software system recognizes water on the basis of a classification algorithm. This classification is accomplished by level thresholding a single near infrared data channel. After each pixel is classified as water or nonwater, the software system then recognizes ponds or lakes as sets of contiguous pixels or as single isolated pixels in the case of very small ponds. Pixels are considered to be contiguous if they are adjacent between successive scan lines. After delineating each water feature, the software system then assigns the feature a position based upon a geographic grid system and calculates the feature's planimetric area, its perimeter, and a parameter known as the shape factor.

Gilmer, D. S.↗
NASA NTRS1980

On the origin of multiply-impulsive emission from solar flares

A set of solar hard X-ray bursts observed with the hard X-ray burst spectrometer on board the OSO-5 satellite was analyzed. The multiply-impulsive two stage events were selected on the basis of both morphological characteristics and association with appropriate phenomena at other wavelengths. Coincident radio, soft X-ray, H-alpha interplanetary particle, and magnetographic data were obtained from several observatories, to aid in developing a comprehensive picture of the physical processes underlying these complex bursts. Two classes of multiply impulsive bursts were identified: events whose components spikes apparently originate in one location, and events in which groups of spikes appear to come from separate regions which flare sequentially. The origin of multiplicity in the case of a single source region remains unidentified. Purely impulsive emissions show no sign of betatron acceleration, thus eliminating this mechanisn as a candidate for inducing multiply spiked structure. The majority of the two stage bursts, however, exhibited spectral behavior consistent with the betatron model, for the first few minutes of the second stage. Betatron acceleration thus has been identified as a common second stage phenomenon.

Karpen, J. T.↗
NASA NTRS1983

Synthesized airfoil data method for prediction of dynamic stall and unsteady airloads

A detailed analysis of dynamic stall experiments has led to a set of relatively compact analytical expressions, called synthesized unsteady airfoil data, which accurately describe in the time-domain the unsteady aerodynamic characteristics of stalled airfoils. An analytical research program was conducted to expand and improve this synthesized unsteady airfoil data method using additional available sets of unsteady airfoil data. The primary objectives were to reduce these data to synthesized form for use in rotor airload prediction analyses and to generalize the results. Unsteady drag data were synthesized which provided the basis for successful expansion of the formulation to include computation of the unsteady pressure drag of airfoils and rotor blades. Also, an improved prediction model for airfoil flow reattachment was incorporated in the method. Application of this improved unsteady aerodynamics model has resulted in an improved correlation between analytic predictions and measured full scale helicopter blade loads and stress data.

Gangwani, S. T.↗
NASA NTRS1985

A gravity model for crustal dynamics (GEM-L2)

The Laser Geodynamics Satellite (Lageos) was the first NASA satellite which was placed into orbit exclusively for laser ranging applications. Lageos was designed to permit extremely accurate measurements of the earth's rotation and the movement of the tectonic plates. The Goddard earth model, GEM-L2, was derived mainly on the basis of the precise laser ranging data taken on many satellites. Douglas et al. (1984) have demonstrated the utility of GEM-L2 in detecting the broadest ocean circulations. As Lageos data constitute the most extensive set of satellite laser observations ever collected, the incorporation of 2-1/2 years of these data into the Goddard earth models (GEM) has substantially advanced the geodynamical objectives. The present paper discusses the products of the GEM-L2 solution.

Lerch, F. J.↗