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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Light Propagation Considerations For Internally Clad Sapphire Optical Fiber Using the 6Li(n,)3H Reaction

Optical frequency domain reflectometry measurements in internally clad single crystal sapphire fiber have received attention in recent years due to their high temperature distributed sensing potential. As work with these fibers has proceeded, there have been some inconsistencies in the results. Deeper investigation and testing has identified two critical considerations for the proper functioning of these fibers. First, users must address the propagation of multimode light along the outer surface of the fiber. Here, by observing the far-field image of an internally clad sapphire fiber when adding index matching fluid to the outer fiber surface, we demonstrate the effects of removing the higher order modes from these fibers. The addition of index matching fluid resulted in nearly single mode performance where multimode performance was previously observed. Second, users must address the effect that coupling the fiber to the interrogator via silica based fiber has on the internally clad sapphire fibers performance. Direct fusion splicing of silica to sapphire, as has been used in the recent work with these fibers, has a mode filtering effect which can be beneficial towards the modal behavior of the fibers. However, in this paper we demonstrate that the splicing can cause a sensing failure due to little or no low order mode light, that is useful for sensing, returning to the detector. The positive results from recent years have demonstrated that optical frequency domain reflectometry sensing performance will be successful in clad sapphire fiber; but only when the considerations described herein are addressed properly.

47 OTHER INSTRUMENTATION↗
NASA NTRS1971

Application of Monte Carlo techniques to optimization of high-energy beam transport in a stochastic environment

An algorithm employing a modified sequential random perturbation, or creeping random search, was applied to the problem of optimizing the parameters of a high-energy beam transport system. The stochastic solution of the mathematical model for first-order magnetic-field expansion allows the inclusion of state-variable constraints, and the inclusion of parameter constraints allowed by the method of algorithm application eliminates the possibility of infeasible solutions. The mathematical model and the algorithm were programmed for a real-time simulation facility; thus, two important features are provided to the beam designer: (1) a strong degree of man-machine communication (even to the extent of bypassing the algorithm and applying analog-matching techniques), and (2) extensive graphics for displaying information concerning both algorithm operation and transport-system behavior. Chromatic aberration was also included in the mathematical model and in the optimization process. Results presented show this method as yielding better solutions (in terms of resolutions) to the particular problem than those of a standard analog program as well as demonstrating flexibility, in terms of elements, constraints, and chromatic aberration, allowed by user interaction with both the algorithm and the stochastic model. Example of slit usage and a limited comparison of predicted results and actual results obtained with a 600 MeV cyclotron are given.

Parrish, R. V.↗
NASA NTRS2003

An Impact Ejecta Behavior Model for Small, Irregular Bodies

In recent years, spacecraft observations of asteroids 951 Gaspra, 243 Ida, 253 Mathilde, and 433 Eros have shown the overriding dominance of impact processes with regard to the structure and surface morphology of these small, irregular bodies. In particular, impact ejecta play an important role in regolith formation, ranging from small particles to large blocks, as well as surface feature modification and obscuration. To investigate these processes, a numerical model has been developed based upon the impact ejecta scaling laws provided by Housen, Schmidt, and Holsapple, and modified to more properly simulate the late-stage ejection velocities and ejecta plume shape changes (ejection angle variations) shown in impact cratering experiments. A target strength parameter has also been added to allow the simulation of strength-dominated cratering events in addition to the more familiar gravity-dominated cratering events. The result is a dynamical simulation which models -- via tracer particles -- the ejecta plume behavior, ejecta blanket placement, and impact crater area resulting from a specified impact on an irregularly shaped target body, which is modeled in 3-dimensional polygon fashion. This target body can be placed in a simple rotation state about one of its principal axes, with the impact site and projectile/target parameters selected by the user. The gravitational force from the irregular target body (on each tracer particle) is determined using the polygonized surface (polyhedron) gravity technique developed by Werner.

Richardson, J. E.↗
DOE OSTI2020

Sierra/SolidMechanics 4.56 User's Guide

Siera/SolidMechanics (Sierra / SM) is a Lagrangian, three-dimensional code for finite element analysis of solids and structures. It provides capabilities for explicit dynamic, implicit quasistatic and dynamic analyses. The explicit dynamics capabilities allow for the efficient and robust solution of models with extensive contact subjected to large, suddenly applied loads. For implicit problems, Sierra / SM uses a multi-level iterative solver, which enables it to effectively solve problems with large deformations, nonlinear material behavior, and contact. Sierra / SM has a versatile library of continuum and structural elements, and a large library of material models. The code is written for parallel computing environments enabling scalable solutions of extremely large problems for both implicit and explicit analyses. It is built on the SIERRA Framework, which facilitates coupling with other SIERRA mechanics codes . This document describes the functionality and input syntax for Sierra/SM.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2006

Generalized Orbital Projections of a Sublimating Ice Particle

The issue of orbital debris resulting from human activities in space is a growing concern for the space users' community. Waste generated in Low Earth Orbit (LEO) can stay in orbit for a long time, creating significant hazards for other spacecraft flying at lower intercepting orbits. Many spacecraft, especially crewed vehicles, are required to vent fluids into space. These fluids include propellant, wastewater, excess condensate, and others. It is important to analyze the behavior of particles that result from these activities, since each individual particle is capable of damaging or destroying a spacecraft in a lower, crossing orbit, and such particles are invisible to tracking radar systems on the ground. The deorbit trajectory of an ice particle is complex. It depends on factors including attitude of the vehicle during vent, initial velocities of particles, altitude at which the vent occurred, and numerous evaporation and sublimation factors. These include contamination within the vented water, evolution of bubbles within the clear water, and sun flux factors such as time of the year and current beta angle. The purpose of this study is to examine the influences of these factors on the trajectories of ice particles resulting from condensate water dumps, and to bound the safe trajectories of spacecraft that lie below the venting spacecraft.

Menkin, Evgeny↗
NASA NTRS2010

Applying Monte Carlo Simulation to Launch Vehicle Design and Requirements Verification

This paper is focused on applying Monte Carlo simulation to probabilistic launch vehicle design and requirements verification. The approaches developed in this paper can be applied to other complex design efforts as well. Typically the verification must show that requirement "x" is met for at least "y" % of cases, with, say, 10% consumer risk or 90% confidence. Two particular aspects of making these runs for requirements verification will be explored in this paper. First, there are several types of uncertainties that should be handled in different ways, depending on when they become known (or not). The paper describes how to handle different types of uncertainties and how to develop vehicle models that can be used to examine their characteristics. This includes items that are not known exactly during the design phase but that will be known for each assembled vehicle (can be used to determine the payload capability and overall behavior of that vehicle), other items that become known before or on flight day (can be used for flight day trajectory design and go/no go decision), and items that remain unknown on flight day. Second, this paper explains a method (order statistics) for determining whether certain probabilistic requirements are met or not and enables the user to determine how many Monte Carlo samples are required. Order statistics is not new, but may not be known in general to the GN&C community. The methods also apply to determining the design values of parameters of interest in driving the vehicle design. The paper briefly discusses when it is desirable to fit a distribution to the experimental Monte Carlo results rather than using order statistics.

Hanson, John M.↗
NASA NTRS2000

The Life Cycle Application of Intelligent Software Modeling for the First Materials Science Research Rack

Marshall Space Flight Center (MSFC) has been funding development of intelligent software models to benefit payload ground operations for nearly a decade. Experience gained from simulator development and real-time monitoring and control is being applied to engineering design, testing, and operation of the First Material Science Research Rack (MSRR-1). MSRR-1 is the first rack in a suite of three racks comprising the Materials Science Research Facility (MSRF) which will operate on the International Space Station (ISS). The MSRF will accommodate advanced microgravity investigations in areas such as the fields of solidification of metals and alloys, thermo-physical properties of polymers, crystal growth studies of semiconductor materials, and research in ceramics and glasses. The MSRR-1 is a joint venture between NASA and the European Space Agency (ESA) to study the behavior of different materials during high temperature processing in a low gravity environment. The planned MSRR-1 mission duration is five (5) years on-orbit and the total design life is ten (IO) years. The MSRR-1 launch is scheduled on the third Utilization Flight (UF-3) to ISS, currently in February of 2003). The objective of MSRR-1 is to provide an early capability on the ISS to conduct material science, materials technology, and space product research investigations in microgravity. It will provide a modular, multi-user facility for microgravity research in materials crystal growth and solidification. An intelligent software model of MSRR-1 is under development and will serve multiple purposes to support the engineering analysis, testing, training, and operational phases of the MSRR-1 life cycle development. The G2 real-time expert system software environment developed by Gensym Corporation was selected as the intelligent system shell for this development work based on past experience gained and the effectiveness of the programming environment. Our approach of multi- uses of the simulation model and its intuitive graphics capabilities is providing a concurrent engineering environment for rapid prototyping and development. Operational schematics of the MSRR-1 electrical, thermal control, vacuum access, and gas supply systems, and furnace inserts are represented graphically in the environment. Logic to represent first order engineering calculations is coded into the knowledge base to simulate the operational behavior of the MSRR-1 systems. An example of engineering data provided includes electrical currents, voltages, operational power, temperatures, thermal fluid flow rates. pressures, and component status indications. These type of data are calculated and displayed at appropriate instrumentation points, and the schematics are animated to reflect the simulated operational status of the MSRR-1. The software control functions are also simulated to represent appropriate operational behavior based on automated control and response to commands received by the crew or ground controllers. The first benefit of this simulation environment is being realized in the high fidelity engineering analysis results from the electrical power system G2 model. Secondly, the MSRR-1 simulation model will be embedded with a hardware mock-up of the MSRR-1 to provide crew training on MSRR-1 integrated payload operations. G2 gateway code will output the simulated instrumentation values, termed as telemetry, in a flight-like data stream so that the crew has realistic and accurate simulated MSRR-1 data on the flight displays which will be designed for crew use. The simulation will also respond appropriately to crew or ground initiated commands, which will be part of normal facility operations. A third use of the G2 model is being planned; the MSRR-1 simulation will be integrated with additional software code as part of the test configuration of the primary onboard computer, or Master Controller, for MSRR-1. We will take advantage of the G2 capability to simulate the flight like data stream to test flight software responses and behavior. A fourth use of the G2 model will be to train the Ground Support Personnel that will monitor the MSRR-1 systems and payloads while they are operating aboard the ISS. The intuitive, schematic based environment will provide an excellent foundation for personnel to understand the integrated configuration and operation of the MSRR-1, and the anticipated telemetry feedback based on operational modes of the equipment. Expert monitoring features will be enhanced to provide a smart monitoring environment for the operators. These features include: (1) Animated, intuitive schematic-based displays which reflect telemetry values, (1) Real-time plotting of simulated or incoming sensor values, (3) High/Low exception monitoring for analog data, (4) Expected state monitoring for discrete data, (5) Data trending, (6) Automated malfunction procedure execution to diagnose problems, (7) Look ahead capability to planned MSRR-1 activities in the onboard timeline. And finally, the logic to calculate telemetry values will be deactivated, and the same environment will interface to the incoming data for the real-time telemetry stream to schematically represent the onboard hardware configuration. G2 will be the foundation for the real-time monitoring and control environment. In summary, our MSRR-1 simulation model spans many elements of the life cycle development of this project: Engineering Analysis, Test and Checkout, Training of Crew and Ground Personnel, and Real-time monitoring and control. By utilizing the unique features afforded by an expert system development environment, we have been able to synergize a powerful tool capable of addressing our project needs at every phase of project development.

Rice, Amanda↗
DOE OSTI2021

Commercial Vehicle Driver Behaviors and Decision Making: Lessons Learned from Urban Ridealongs

As e-commerce and urban deliveries spike, cities grapple with managing urban freight more actively. In order to effectively manage urban deliveries, city planners and policy makers need to better understand driver behaviors and the challenges they experience in performing deliveries. In this study, we collected data on commercial vehicle (CV) driver behaviors by performing ridealongs with various logistics carriers. Ridealongs were performed in Seattle, Washington, covering a range of vehicles (cars, vans, and trucks), goods (parcels, mail, beverages, and printed materials), and customer types (residential, office, large and small retail). Observers collected qualitative observations and quantitative data on trip and dwell times, while also tracking vehicles through GPS devices. The results showed that, on average, urban CVs spent 80 percent of their daily operating time parked. The study also found that, unlike the common belief, drivers (especially those operating heavier vehicles) parked in authorized parking locations, with only less than 5 percent of stops occurring in the travel lane. Dwell times associated with authorized parking locations were significantly longer than those of other parking locations, and mail and heavy goods deliveries generally had longer dwell times. We also identified three main criteria CV drivers used for choosing a parking location: avoiding unsafe maneuvers, minimizing conflicts with other users of the road, and coopetition with other commercial drivers. Here, the results provide estimates for trip times, dwell times, and parking choice types, as well as insights into why those decisions are made and the factors affecting driver choices.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Sierra/SolidMechanics 4.58 User's Guide

Sierra / SolidMechanics (Sierra / SM) is a Lagrangian, three-dimensional code for finite element analysis of solids and structures. It provides capabilities for explicit dynamic, implicit quasistatic and dynamic analyses. The explicit dynamics capabilities allow for the efficient and robust solution of models with extensive contact subjected to large, suddenly applied loads. For implicit problems, Sierra / SM uses a multi-level iterative solver, which enables it to effectively solve problems with large deformations, nonlinear material behavior, and contact. Sierra / SM has a versatile library of continuum and structural elements, an d a large library of material models. The code is written for parallel computing environments enabling scalable solutions of extremely large problems for both implicit and explicit analyses. It is built on the SIERRA Framework, which facilitates coupling with other SIERRA mechanics codes . This document describes the functionality and input syntax for Sierra / SM.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Evaluation of Multi-cell Failure Propagation

Failure propagation testing is of increasing interest to the designers and end users of battery systems. One of the chief difficulties, however, is choosing an appropriate initiation method to perform the test. Single cell abuse testing is typically used to initiate thermal runaway but this can involve a large amount of additional energy injected into the system. It is assumed that this will have some impact on the behavior of a propagating thermal runaway event, but there is little data available as to how significant this would be. Further, it is ultimately difficult to develop viable propagation tests for compliance and public safety activities without better knowledge of how test methods will impact the results. This work looks at propagating battery failure with a variety of chemistries, formats, configurations and initiation methods to determine the level of significance of the chosen initiation method on the test results. We have ultimately found while there is some impact on the detailed results of propagation testing, in most cases other factors, particularly the energy density of the system play a much greater role in the likelihood of a propagation event consuming an entire battery. We have also provided some guidelines for test design to support best practices in testing.

25 ENERGY STORAGE↗
NASA NTRS1993

A battery power model for the EUVE spacecraft

This paper describes a battery power model that has been developed to simulate and predict the behavior of the 50 ampere-hour nickel-cadmium battery that supports the Extreme Ultraviolet Explorer (EUVE) spacecraft in its low Earth orbit. First, for given orbit, attitude, solar array panel and spacecraft load data, the model calculates minute-by-minute values for the net power available for charging the battery for a user-specified time period (usually about two weeks). Next, the model is used to calculate minute-by-minute values for the battery voltage, current and state-of-charge for the time period. The model's calculations are explained for its three phases: sunrise charging phase, constant voltage phase, and discharge phase. A comparison of predicted model values for voltage, current and state-of-charge with telemetry data for a complete charge-discharge cycle shows good correlation. This C-based computer model will be used by the EUVE Flight Operations Team for various 'what-if' scheduling analyses.

Yen, Wen L.↗
NASA NTRS2017

Computational and Experimental Fluid-Structure Interaction Analysis of a High-Lift Wing with a Slat-Cove Filler for Noise Reduction

Airframe noise is a significant component of overall noise produced by transport aircraft during landing and approach (low speed maneuvers). A significant source for this noise is the cove of the leading-edge slat. The slat-cove filler (SCF) has been shown to be effective at mitigating slat noise. The objective of this work is to understand the fluid-structure interaction (FSI) behavior of a superelastic shape memory alloy (SMA) SCF in flow using both computational and physical models of a high-lift wing. Initial understanding of flow around the SCF and wing is obtained using computational fluid dynamics (CFD) analysis at various angles of attack. A framework compatible with an SMA constitutive model (implemented as a user material subroutine) is used to perform FSI analysis for multiple flow and configuration cases. A scaled physical model of the high-lift wing is constructed and tested in the Texas A&M 3 ft-by-4-foot wind tunnel. Initial validation of both CFD and FSI analysis is conducted by comparing lift, drag and pressure distributions with experimental results.

Scholten, William D.↗
NASA NTRSDate not supplied

Lessons Learned on the Use of Data Surfaces for Ffowcs Williams-Hawkings Calculations: Airframe Noise Applications

The use of integral solutions to the acoustic analogy-based Ffowcs Williams-Hawkings (FW-H) formulation is the defacto industrial and academic approach for assessing far-field acoustic behavior from airframe noise simulations. The methodology utilizes time-accurate flow variables obtained at arbitrary data surfaces to determine far-field spectra. The solid surface approach, where the time history of pressure is recorded on the surface of the aircraft, is generally preferred. Permeable surfaces, where pressure and velocity are recorded on a user-defined surface enclosing the aircraft, are also used. This paper seeks to share some of the valuable lessons we learned over the past several years on the limitations of the FW-H formulation and best practices for its successful application. We show results for various configurations comprising isolated landing gears, a business jet, a large commercial transport, and a generic low boom supersonic prototype, all at landing conditions. We demonstrate that the solid FW-H approach has significant accuracy limitations for most realistic cases and that the permeable FW-H approach may also fail in specific scenarios, requiring additional costly steps to extract the correct far-field noise spectra. Suggested guidelines for proper FW-H calculations are also given.

Acoustic propagation, Ffowcs Williams-Hawkings Cal↗
NASA NTRS1992

User's guide to the Reliability Estimation System Testbed (REST)

The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors.

Nicol, David M.↗
NASA NTRS1992

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution DC test bed

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF Program design and development phases, a system Power Management and Distribution (PMAD) DC test bed was assembled. Some of the objectives of this test bed facility are the evaluation of, system efficiency, power quality, system stability, and system protection and reconfiguration schemes. In order to provide a realistic operating scenario, dc Load Converter Units are used in the PMAD dc test bed to characterize the user interface with the power system. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. This final regulation is required on the actual space station because the majority of user loads will require voltage levels different from the secondary bus voltage. This paper describes the testing of load converters in an end to end system environment (from solar array to loads) where their interactions and compatibility with other system components are considered. Some of the system effects of interest that are presented include load converters transient behavior interactions with protective current limiting switchgear, load converters ripple effects, and the effects of load converter constant power behavior with protective features such as foldback.

Lebron, Ramon C.↗
NASA NTRS1992

Load converter interactions with the secondary system in the Space Station Freedom power management and distribution dc test bed

The NASA LeRC in Cleveland, Ohio, is responsible for the design, development, and assembly of the Space Station Freedom (SSF) Electrical Power System (EPS). In order to identify and understand system level issues during the SSF program design and development phases, a system Power Management and Distribution (PMAD) dc test bed was assembled. Some of the objectives of this test bed facility are the evaluation of, system efficiency, power quality, system stability, and system protection and reconfiguration schemes. In order to provide a realistic operating scenario, dc Load Converter Units are used in the PMAD dc test bed to characterize the user interface with the power system. These units are dc to dc converters that provide the final system regulation before power is delivered to the load. This final regulation is required on the actual space station because the majority of user loads will require voltage levels different from the secondary bus voltage. This paper describes the testing of load converters in an end to end system environment (from solar array to loads) where their interactions and compatibility with other system components are considered. Some of the system effects of interest that are presented include load converters transient behavior interactions with protective current limiting switchgear, load converters ripple effects, and the effects of load converter constant power behavior with protective features such as foldback.

Lebron, Ramon C.↗
NASA NTRS2002

Tools and Techniques for Evaluating the Effects of Maintenance Resource Management (MRM) in Air Safety

This research project was designed as part of a larger effort to help Human Factors (HF) implementers, and others in the aviation maintenance community, understand, evaluate, and validate the impact of Maintenance Resource Management (MRM) training programs, and other MRM interventions; on participant attitudes, opinions, behaviors, and ultimately on enhanced safety performance. It includes research and development of evaluation methodology as well as examination of psychological constructs and correlates of maintainer performance. In particular, during 2001, three issues were addressed. First a prototype process for measuring performance was developed and used. Second an automated calculator was developed to aid the HF implementer user in analyzing and evaluating local survey data. These results include being automatically compared with the experience from all MRM programs studied since 1991. Third the core survey (the Maintenance Resource Management Technical Operations Questionnaire, or 'MRM/TOQ') was further developed and tested to include topics of added relevance to the industry.

Taylor, James C.↗
NASA NTRS2003

Extended Statistical Short-Range Guidance for Peak Wind Speed Analyses at the Shuttle Landing Facility: Phase II Results

This report describes the results from Phase II of the AMU's Short-Range Statistical Forecasting task for peak winds at the Shuttle Landing Facility (SLF). The peak wind speeds are an important forecast element for the Space Shuttle and Expendable Launch Vehicle programs. The 45th Weather Squadron and the Spaceflight Meteorology Group indicate that peak winds are challenging to forecast. The Applied Meteorology Unit was tasked to develop tools that aid in short-range forecasts of peak winds at tower sites of operational interest. A seven year record of wind tower data was used in the analysis. Hourly and directional climatologies by tower and month were developed to determine the seasonal behavior of the average and peak winds. Probability density functions (PDF) of peak wind speed were calculated to determine the distribution of peak speed with average speed. These provide forecasters with a means of determining the probability of meeting or exceeding a certain peak wind given an observed or forecast average speed. A PC-based Graphical User Interface (GUI) tool was created to display the data quickly.

Lambert, Winifred C.↗