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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 1,081 records · Page 60

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NASA NTRS2005

Cognitive Functioning in Space Exploration Missions: A Human Requirement

Solving cognitive issues in the exploration missions will require implementing results from both Human Behavior and Performance, and Space Human Factors Engineering. Operational and research cognitive requirements need to reflect a coordinated management approach with appropriate oversight and guidance from NASA headquarters. First, this paper will discuss one proposed management method that would combine the resources of Space Medicine and Space Human Factors Engineering at JSC, other NASA agencies, the National Space Biomedical Research Institute, Wyle Labs, and other academic or industrial partners. The proposed management is based on a Human Centered Design that advocates full acceptance of the human as a system equal to other systems. Like other systems, the human is a system with many subsystems, each of which has strengths and limitations. Second, this paper will suggest ways to inform exploration policy about what is needed for optimal cognitive functioning of the astronaut crew, as well as requirements to ensure necessary assessment and intervention strategies for the human system if human limitations are reached. Assessment strategies will include clinical evaluation and fitness-to-perform evaluations. Clinical intervention tools and procedures will be available to the astronaut and space flight physician. Cognitive performance will be supported through systematic function allocation, task design, training, and scheduling. Human factors requirements and guidelines will lead to well-designed information displays and retrieval systems that reduce crew time and errors. Means of capturing process, design, and operational requirements to ensure crew performance will be discussed. Third, this paper will describe the current plan of action, and future challenges to be resolved before a lunar or Mars expedition. The presentation will include a proposed management plan for research, involvement of various organizations, and a timetable of deliverables.

Fiedler, Edan↗

NASA NTRS2016

System-Level Prognostics for the National Airspace

In the National Airspace System (NAS), safety is assured through a set of rules, regulations, and procedures to respond to unsafe events. However, safety stands to benefit immensely from the introduction of tools and methodologies from Prognostics and Health Management (PHM). PHM will enable the NAS to stochastically predict unsafe states within the NAS, enabling a proactive preventative response strategy, as opposed to a reactive mitigative one. However, current PHM methods do not directly apply to the NAS for several reasons: they typically apply only at the component level, are implemented in a centralized manner, and are focused only on predicting remaining useful life. In this paper, we extend the model-based prognostics approach to PHM in order to provide a framework that can be applied to the NAS. We offer a system-level approach that supports a distributed implementation, and provide algorithms to predict the probability of an unsafe state, either at a specific time or within a time interval, and to predict the time of an unsafe state. Experimental results in simulation demonstrate the new approach.

prognostics↗

NASA NTRSDate not supplied

Simulated Evaluation of Strategic Conflict Management Capabilities for Urban Air Mobility Operations

Urban Air Mobility (UAM) is a new air transportation service concept to carry passengers or cargo in metropolitan areas, leveraged by innovative aircraft and automation technologies. NASA has conducted a series of simulations to evaluate the UAM concept of operations and inform the development of airspace procedures and services for UAM operations. The latest set of simulations called “X5” were conducted to test a Provider of Services for UAM (PSU) prototype that NASA developed for UAM flight planning, strategic conflict management support, and data exchange between UAM operators. In these simulations, two strategic conflict management capabilities, Demand-Capacity Balancing (DCB) and Sequencing and Scheduling (S&S), were further investigated. This paper describes the system architecture designed for the X5 simulation activities, the sequence diagram for strategic conflict management, and the simulation environment in the Dallas/Fort Worth urban area. The simulation results based on several system performance metrics for evaluation show that a sequential application of DCB and S&S effectively works to distribute traffic demand and meet sequencing and spacing criteria by assigning ground delays, compared to the DCB only and S&S only cases.

Urban Air Mobility, Strategic Conflict Management,↗

NASA NTRSDate not supplied

Simulated Evaluation of Strategic Conflict Management Capabilities for Urban Air Mobility Operations

Simulation↗

DOE OSTI2022

Brownian bridge-based speed imputation technique for truck energy consumption and emissions estimation

The available truck Global Positioning System (GPS) data, typically collected with large time gaps, rely on imputation techniques to obtain second-by-second data that are required in models for estimating truck energy consumption and emissions. However, existing speed imputation techniques either require a large amount of high-resolution data for model training or rely on special movement assumptions. Here, to fill the gap and effectively apply the low-resolution truck GPS datasets, this paper proposes a simple imputation technique that adopts the Brownian bridge structure to impute missing speed data. The proposed technique introduces a feasible imputation region and a combined drift into the imputation procedure to capture vehicle acceleration constraint, travel distance constraint, and speed volatility. The calibrated model is applied to a set of low-resolution truck GPS data. The results demonstrate the robustness of the proposed technique in enhancing estimation accuracy when using low-resolution GPS data to estimate fuel consumption and emissions.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2020

Shield to Pin Coupling of Lightning-Like Transients on Payload Umbilical Cables on a Launch Pad

In this paper we describe in-situ testing of a long payload umbilical, on a launch site, injected with “lightning- like” transients and describe resulting pin-to-pin voltages. Injections and voltage measurements near the ground support equipment room, as well as at a location near the payload junction box, are made. The umbilical cables tested include an outer over-braid and the inner conductor coupling is examined for open circuit, short-circuit and various loads representative of spacecraft input impedances. This testing is important because the Kennedy Space Center (KSC) where the lightning occurrence is the highest in the United States, is the primary launch site for Launch Services Program spacecraft customers. Lightning planning is essential but developing a lightning plan is often overlooked or not adequately analyzed leaving the spacecraft vulnerable to time delays or even damage when lightning occurs. At other popular launch sites like Vandenberg Air Force Base (VAFB) where lightning occurs less often, although at the same or greater intensity when it does occur, lightning planning is often completely ignored by the spacecraft. The two major questions to be addressed in the lightning plan are what retesting should be done to establish a “goodness” level and what is the trigger criteria for this testing? The spacecraft will typically use a standard spacecraft check-out procedure to address the necessary retesting, but determining the trigger criteria is often an issue. For instance, a spacecraft needs to understand what their immunity is to a certain lightning magnitude and location. Determining the amount of current that can be coupled onto a spacecraft umbilical can be calculated by using worst case assumptions or measured with current probes and current measurement devices. Spacecraft can also determine what pin-to-pin voltages they are sensitive to, however pin-to-pin voltage measurements are not typically taken during the strike due to the invasive nature of this measurement. In this paper, we present detailed data on the shield to pin voltage transfer functions to provide insight to the spacecraft developers for lightning retest criteria planning. The results from this unique testing opportunity provide essential details on specific coupling mechanisms affecting spacecraft hardware that interfaces with the ground support equipment. This missing link between cable shield currents and payload susceptibility voltages has been methodically tested and representative data presented.

Trout, Dawn↗

DOE OSTI2014

Construction of energy-stable projection-based reduced order models

Our paper aims to unify and extend several approaches for building stable projection-based reduced order models (ROMs) using the energy method and the concept of “energy-stability”. Attention is focused on linear time-invariant (LTI) systems. First, an approach for building energy stable Galerkin ROMs for linear hyperbolic or incompletely parabolic systems of partial differential equations (PDEs) using continuous projection is proposed. The key idea is to apply to the system a transformation induced by the Lyapunov function for the system, and to build the ROM in the transformed variables. The result of this procedure will be a ROM that is energy-stable for any choice of reduced basis. It is shown that, for many PDE systems, the desired transformation is induced by a special inner product, termed the “symmetry inner product”. Next, attention is turned to building energy-stable ROMs via discrete projection. A discrete counterpart of the continuous symmetry inner product, termed the “Lyapunov inner product”, is derived. Moreover, it is shown that the Lyapunov inner product can be computed in a black-box fashion for a stable LTI system ari sing from the discretization of a system of PDEs in space. Projection in this inner product guarantees a ROM that is energy-stable, again for any choice of reduced basis. Connections between the Lyapunov inner product and the inner product induced by the balanced truncation algorithm are made. We also made comparisons between the symmetry inner product and the Lyapunov inner product. Performance of ROMs constructed using these inner products is evaluated on several benchmark test cases.

97 MATHEMATICS AND COMPUTING↗

NASA NTRS1978

Ride quality criteria of multifactor environments

The paper describes a comprehensive ride quality model that accounts for the effects of multifrequency and multitaxis vibration inputs as well as the interactive effects of noise and vibration upon passenger discomfort. The model is based on extensive experimental studies involving a realistic multi-degree-of-freedom laboratory simulator, and data relating to human discomfort response to vertical, lateral, and roll vibrations are presented. Results of studies involving vibration stimuli are expressed by sets of equal discomfort curves for each of three axes of vibration. A set of noise-vibration curves are obtained by an additive procedure, shown to be valid in the range under consideration, which combines the discomfort components due to noise and vibration. Other results from the study of human response to combined noise and vibration stimuli are reported.

Leatherwood, J. D.↗

NASA NTRS1982

Photo-orthotropic elasticity - A new technique for stress analysis of composites

This paper deals with the application of photoelastic methods to glass fiber reinforced plastics. The basic principles governing the photoelastic response in birefringent orthotropic composites are briefly reviewed. Then, three important aspects of photo-orthotropic elasticity, namely, photoelastic calibration, separation of principal stresses, and application to problems of engineering importance, are considered in detail. A new calibration specimen is proposed for determining the three independent photoelastic constants: an orthotropic half-plane subjected to a concentrated edge load. From the isochromatic response, the three stress-fringe values can be obtained by a least-squares procedure based on the theoretical stress distribution. Next, four methods of separating the principal stresses in birefringent composite models are proposed: the method of drilling small holes at the points of interest, the method of oblique incidence, the method of combining the transmitted photoelastic response with the reflected photoelastic response, and the method of birefringence dispersion.

Prabhakaran, R.↗

NASA NTRS1990

Lidar measurements of stratospheric ozone and intercomparisons and validation

A ground-based, high power differential absorption lidar (DIAL) system has been implemented to make long term, precise measurements or stratospheric ozone concentration profiles from about 20- to 50-km altitude. This lidar is located at an elevation of 2300 m in the San Gabriel Mountains, Southern California, and has been in operation since January 1988. Evaluation of the results obtained from this system has been provided through an intercomparison campaign, carried out during October/November 1988, and through long term comparison with SAGE II satellite measurements. This paper describes the implementation of the system and its operation, including the procedures for data analysis. Examples of ozone profiles measured, and intercomparisons with measurements made by other instruments, are presented; they show that the lidar is capable of producing high quality ozone measurements up to at least 45-km altitude.

Mcdermid, I. Stuart↗

NASA NTRS1995

Alternative Approach to Vehicle Element Processing

The National Space Transportation Policy (NSTP), describes the challenge facing today's aerospace industry. 'Assuring reliable and affordable access to space through U.S. space transportation capabilities is a fundamental goal of the U.S. space program'. Experience from the Space Shuttle Program (SSP) tells us that launch and mission operations are responsible for approximately 45 % of the cost of each shuttle mission. Reducing these costs is critical to NSTP goals in the next generation launch vehicle. Based on this, an innovative alternative approach to vehicle element processing was developed with an emphasis on reduced launch costs. State-of-the-art upgrades to the launch processing system (LPS) will enhance vehicle ground operations. To carry this one step further, these upgrade could be implemented at various vehicle element manufacturing sites to ensure system compatibility between the manufacturing facility and the launch site. Design center vehicle stand alone testing will ensure system integrity resulting in minimized checkout and testing at the launch site. This paper will addresses vehicle test requirements, timelines and ground checkout procedures which enable concept implementation.

Huether, Jacob E.↗

DOE OSTI2017

Improved Modelling for the Assembly Discontinuity Factors in the APEC Method

Modern reactor analysis of light water reactor depends largely on a two-step procedure based on the simplified equivalence theory (SET). Consequently, the resulting homogenized two-group cross-section (XS) and associated discontinuity factor (DF) are subject to noticeable, intrinsic uncertainties. In our previous study, we introduced the albedo-corrected parameterized equivalence constants (APEC) method, which is a new leakage correction method applicable to the fuel assembly homogenized two-group XS of the standard two-step procedure. In the APEC method, fuel assembly two-group XS is expressed as a simple polynomial function of assembly-wise current-to-flux ratio (CFR), and it was demonstrated that two-group XSs can be well corrected during a nodal calculation and the nodal accuracy is improved a lot. However, since the conventional assembly discontinuity factor (ADF) is still used in the current APEC method, a small but non-negligible error is unavoidable. Therefore, it is necessary to include improved DF model in the APEC method for a higher accuracy. The functionalized discontinuity factor (FDF) using the definition of CFR was investigated by authors before the development of the APEC method, where it was motivated by the boundary perturbation theory by F. Rahnema. However, in our previous study on FDF, lattice calculations were performed only with one-dimensional two-group diffusion equation and could not be applied to actual core analysis. In this paper, feasibility study of DF functionalization is performed based on a 2-D method of characteristics (MOC) lattice code, DeCART2D.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

Construction of Boron- and Nitrogen-Enriched Nanoporous π-Conjugated Networks Towards Enhanced Hydrogen Activation

Boron-enriched scaffolds have demonstrated unique features and promising performance in the field of catalysis towards the activation of small gas molecules. However, there is still a lack of facile approaches capable of achieving high B doping and abundant porous channels in the targeted catalysts. Here, in this paper, construction of boron- and nitrogen-enriched nanoporous π-conjugated networks (BN-NCNs) was achieved via a facile ionothermal polymerization procedure with hexaazatriphenylenehexacarbonitrile [HAT(CN) 6 ] sodium borohydride as the starting materials. The as-produced BN-NCN scaffolds were featured by high heteroatoms doping (B up to 23 wt. % and N: up to 17 wt. %) and permanent porosity (surface area up to 759 m 2 g -1 mainly contributed by micropores). With the unsaturated bonded B species acting as the active Lewis acid sites and defected N species acting as the active Lewis base sites, those BN-NCNs delivered attractive catalytic performance towards H 2 activation/dissociation in both gaseous and liquid phase, acting as efficient metal-free heterogeneous frustrated Lewis pairs (FLPs) catalysts in hydrogenation procedures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Fiber Optic Distributed Sensors for High-resolution Temperature Field Mapping

The reliability of computational fluid dynamics (CFD) codes is checked by comparing simulations with experimental data. A typical data set consists chiefly of velocity and temperature readings, both ideally having high spatial and temporal resolution to facilitate rigorous code validation. While high resolution velocity data is readily obtained through optical measurement techniques such as particle image velocimetry, it has proven difficult to obtain temperature data with similar resolution. Traditional sensors such as thermocouples cannot fill this role, but the recent development of distributed sensing based on Rayleigh scattering and swept-wave interferometry offers resolution suitable for CFD code validation work. Thousands of temperature measurements can be generated along a single thin optical fiber at hundreds of Hertz. Sensors function over large temperature ranges and within opaque fluids where optical techniques are unsuitable. But this type of sensor is sensitive to strain and humidity as well as temperature and so accuracy is affected by handling, vibration, and shifts in relative humidity. Such behavior is quite unlike traditional sensors and so unconventional installation and operating procedures are necessary to ensure accurate measurements. This paper demonstrates implementation of a Rayleigh scattering-type distributed temperature sensor in a thermal mixing experiment involving two air jets at 25 and 45 °C. We present criteria to guide selection of optical fiber for the sensor and describe installation setup for a jet mixing experiment. We illustrate sensor baselining, which links readings to an absolute temperature standard, and discuss practical issues such as errors due to flow-induced vibration. This material can aid those interested in temperature measurements having high data density and bandwidth for fluid dynamics experiments and similar applications. We highlight pitfalls specific to these sensors for consideration in experiment design and operation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1992

Statistical characterization of life drivers for a probabilistic design analysis

This paper discusses the issue of statistical characterization of life drivers for a probabilistic design analysis (PDA) approach to support the conventional deterministic structural design methods that are currently used. The probabilistic approach takes into consideration the modeling inadequacies and uncertainties in many design variables such as loads, environments, and material properties. The importance of the distributional assumption is motivated by illustrating an example where the results differ substantially due to the distribution selected. Different types of distributions are discussed and techniques for estimating the parameters are given. Given this information, procedures are outlined for selecting the appropriate distribution based on the particular type of variable (i.e., dimensional, performance) as well as the information that is available (i.e., test data, engineering analysis). Finally, techniques are given for generating random numbers from these selected distributions within the PDA process.

Fox, Eric P.↗

NASA NTRS2003

A Computational Study of the Abrupt Wing Stall (AWS) Characteristics for Various Fighter Jets: F/A-18E and F-16C - Part 1

Steady state Computational Fluid Dynamic (CFD) simulations are used to gain an understanding of the physics behind the Abrupt Wing Stall (AWS) phenomenon and to arrive at static Figures of Merit (FOMs). Navier-Stokes simulations are conducted using the NASA Langley developed TetrUSS simulation suite which is based on tetrahedral, unstructured grids. The physics of the AWS phenomenon is understood by comparing CFD simulation results on two aircraft; a pre-production F/A-18E configuration which exhibits AWS phenomenon under certain geometric and flow conditions, and an F-16C aircraft configuration that does not. The CFD code is first validated against two sets of experimental data to build confidence in its use for the problem of AWS. An attempt is then made to understand the possible causes of AWS by analyzing and comparing the detailed flow fields between the two configurations under a variety of flow conditions. Based on this approach, a number of static Figures of Merit are developed to predict the potential existence of AWS. The FOMs include the break in the lift and wing root bending moment versus angle-of-attack (AoA) curves and the rate of change of sectional lift with respect to AoA. A companion paper, in Part II, describes a similar CFD study on two other aircraft, the AV-8B Harrier and F/A-18C. Results from both these studies, as well as other CFD studies conducted as part of the AWS program are used to recommend a CFD procedure for predicting the existence of AWS in future aerospace designs.

Parikh, Paresh↗

NASA NTRS2003

Sensitivity and Calibration of Non-Destructive Evaluation Method That Uses Neural-Net Processing of Characteristic Fringe Patterns

This paper answers some performance and calibration questions about a non-destructive-evaluation (NDE) procedure that uses artificial neural networks to detect structural damage or other changes from sub-sampled characteristic patterns. The method shows increasing sensitivity as the number of sub-samples increases from 108 to 6912. The sensitivity of this robust NDE method is not affected by noisy excitations of the first vibration mode. A calibration procedure is proposed and demonstrated where the output of a trained net can be correlated with the outputs of the point sensors used for vibration testing. The calibration procedure is based on controlled changes of fastener torques. A heterodyne interferometer is used as a displacement sensor for a demonstration of the challenges to be handled in using standard point sensors for calibration.

Decker, Arthur J.↗

NASA NTRS2004

Role of Turbulent Prandtl Number on Heat Flux at Hypersonic Mach Number

Present simulation of turbulent flows involving shock wave/boundary layer interaction invariably overestimates heat flux by almost a factor of two. One possible reason for such a performance is a result of the fact that the turbulence models employed make use of Morkovin's hypothesis. This hypothesis is valid for non-hypersonic Mach numbers and moderate rates of heat transfer. At hypersonic Mach numbers, high rates of heat transfer exist in regions where shock wave/boundary layer interactions are important. As a result, one should not expect traditional turbulence models to yield accurate results. The goal of this investigation is to explore the role of a variable Prandtl number formulation in predicting heat flux in flows dominated by strong shock wave/boundary layer interactions. The intended applications involve external flows in the absence of combustion such as those encountered in supersonic inlets. This can be achieved by adding equations for the temperature variance and its dissipation rate. Such equations can be derived from the exact Navier-Stokes equations. Traditionally, modeled equations are based on the low speed energy equation where the pressure gradient term and the term responsible for energy dissipation are ignored. It is clear that such assumptions are not valid for hypersonic flows. The approach used here is based on the procedure used in deriving the k-zeta model, in which the exact equations that governed k, the variance of velocity, and zeta, the variance of vorticity, were derived and modeled. For the variable turbulent Prandtl number, the exact equations that govern the temperature variance and its dissipation rate are derived and modeled term by term. The resulting set of equations are free of damping and wall functions and are coordinate-system independent. Moreover, modeled correlations are tensorially consistent and invariant under Galilean transformation. The final set of equations will be given in the paper.

Xiao, X.↗