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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Building Safer Systems With SpecTRM

System safety, an integral component in software development, often poses a challenge to engineers designing computer-based systems. While the relaxed constraints on software design allow for increased power and flexibility, this flexibility introduces more possibilities for error. As a result, system engineers must identify the design constraints necessary to maintain safety and ensure that the system and software design enforces them. Safeware Engineering Corporation, of Seattle, Washington, provides the information, tools, and techniques to accomplish this task with its Specification Tools and Requirements Methodology (SpecTRM). NASA assisted in developing this engineering toolset by awarding the company several Small Business Innovation Research (SBIR) contracts with Ames Research Center and Langley Research Center. The technology benefits NASA through its applications for Space Station rendezvous and docking. SpecTRM aids system and software engineers in developing specifications for large, complex safety critical systems. The product enables engineers to find errors early in development so that they can be fixed with the lowest cost and impact on the system design. SpecTRM traces both the requirements and design rationale (including safety constraints) throughout the system design and documentation, allowing engineers to build required system properties into the design from the beginning, rather than emphasizing assessment at the end of the development process when changes are limited and costly.System safety, an integral component in software development, often poses a challenge to engineers designing computer-based systems. While the relaxed constraints on software design allow for increased power and flexibility, this flexibility introduces more possibilities for error. As a result, system engineers must identify the design constraints necessary to maintain safety and ensure that the system and software design enforces them. Safeware Engineering Corporation, of Seattle, Washington, provides the information, tools, and techniques to accomplish this task with its Specification Tools and Requirements Methodology (SpecTRM). NASA assisted in developing this engineering toolset by awarding the company several Small Business Innovation Research (SBIR) contracts with Ames Research Center and Langley Research Center. The technology benefits NASA through its applications for Space Station rendezvous and docking. SpecTRM aids system and software engineers in developing specifications for large, complex safety critical systems. The product enables engineers to find errors early in development so that they can be fixed with the lowest cost and impact on the system design. SpecTRM traces both the requirements and design rationale (including safety constraints) throughout the system design and documentation, allowing engineers to build required system properties into the design from the beginning, rather than emphasizing assessment at the end of the development process when changes are limited and costly.

Source record↗
NASA NTRS1986

Radiation View-Factor Program With Interactive Graphics

VIEW is six computer programs for determining view factors, graphically displaying surfaces, and evaluating solar irradiation of assemblage of surfaces. Programs offer thermal engineer powerful system for view-factor determination. Central program of system (VIEWC) computes longwave radiantenergy exchange factors between surfaces that make up enclosure. Other VIEW programs support user working with VIEWC.

Emery, A. F.↗
NASA NTRS1990

Predicting the audibility and annoyance of unducted fan engines

Predictions of the prevalence of annoyance associated with aircraft noise exposure are heavily influenced by field studies conducted in urban airport neighborhoods. Flyovers heard in such relatively high ambient noise environments are composed in large part of high absolute level, broadband noise. In contrast, noise exposure created en route by aircraft powered by unducted fan engines is expected to be relatively low in level, but to contain prominent low frequency tonal energy. These tones will be readily audible in rural and other low ambient noise environments. The annoyance of noise intrusions of low absolute level has been shown to be closely related to their audibility. Thus, one way to predict the annoyance of en route noise generated by unducted fan engines is to estimate its audibility relative to that of conventionally powered aircraft in different ambient noise environments. This may be accomplished by computing the audibility of spectra produced by an aircraft powered by unducted fan engines and comparing predicted probabilities of annoyance for them with those of conventionally powered transport aircraft.

Fidell, Sanford↗
NASA NTRS2001

NASA's Information Power Grid: Large Scale Distributed Computing and Data Management

Large-scale science and engineering are done through the interaction of people, heterogeneous computing resources, information systems, and instruments, all of which are geographically and organizationally dispersed. The overall motivation for Grids is to facilitate the routine interactions of these resources in order to support large-scale science and engineering. Multi-disciplinary simulations provide a good example of a class of applications that are very likely to require aggregation of widely distributed computing, data, and intellectual resources. Such simulations - e.g. whole system aircraft simulation and whole system living cell simulation - require integrating applications and data that are developed by different teams of researchers frequently in different locations. The research team's are the only ones that have the expertise to maintain and improve the simulation code and/or the body of experimental data that drives the simulations. This results in an inherently distributed computing and data management environment.

Johnston, William E.↗
NASA NTRS1992

Phase change energy storage for solar dynamic power systems

This paper presents the results of a transient computer simulation that was developed to study phase change energy storage techniques for Space Station Freedom (SSF) solar dynamic (SD) power systems. Such SD systems may be used in future growth SSF configurations. Two solar dynamic options are considered in this paper: Brayton and Rankine. Model elements consist of a single node receiver and concentrator, and takes into account overall heat engine efficiency and power distribution characteristics. The simulation not only computes the energy stored in the receiver phase change material (PCM), but also the amount of the PCM required for various combinations of load demands and power system mission constraints. For a solar dynamic power system in low earth orbit, the amount of stored PCM energy is calculated by balancing the solar energy input and the energy consumed by the loads corrected by an overall system efficiency. The model assumes an average 75 kW SD power system load profile which is connected to user loads via dedicated power distribution channels. The model then calculates the stored energy in the receiver and subsequently estimates the quantity of PCM necessary to meet peaking and contingency requirements. The model can also be used to conduct trade studies on the performance of SD power systems using different storage materials.

Chiaramonte, F. P.↗
NASA NTRS1993

Nonlinear dynamic simulation of single- and multi-spool core engines

In this paper a new computational method for accurate simulation of the nonlinear dynamic behavior of single- and multi-spool core engines, turbofan engines, and power generation gas turbine engines is presented. In order to perform the simulation, a modularly structured computer code has been developed which includes individual mathematical modules representing various engine components. The generic structure of the code enables the dynamic simulation of arbitrary engine configurations ranging from single-spool thrust generation to multi-spool thrust/power generation engines under adverse dynamic operating conditions. For precise simulation of turbine and compressor components, row-by-row calculation procedures were implemented that account for the specific turbine and compressor cascade and blade geometry and characteristics. The dynamic behavior of the subject engine is calculated by solving a number of systems of partial differential equations, which describe the unsteady behavior of the individual components. In order to ensure the capability, accuracy, robustness, and reliability of the code, comprehensive critical performance assessment and validation tests were performed. As representatives, three different transient cases with single- and multi-spool thrust and power generation engines were simulated. The transient cases range from operating with a prescribed fuel schedule, to extreme load changes, to generator and turbine shut down.

Schobeiri, T.↗
NASA NTRS1984

Interactive graphics nonlinear constrained optimization

An interactive computer graphics environment was used for nonlinear constrained optimization analysis. It is found that by combining the power of a digital computer with the subtlety of engineering judgment during program execution, final results can be substantially better than the ones achieved by the numerical algorithm by itself.

Saouma, V. E.↗
NASA NTRS1990

Research and Technology 1990

A brief but comprehensive review is given of the technical accomplishments of the NASA Lewis Research Center during the past year. Topics covered include instrumentation and controls technology; internal fluid dynamics; aerospace materials, structures, propulsion, and electronics; space flight systems; cryogenic fluids; Space Station Freedom systems engineering, photovoltaic power module, electrical systems, and operations; and engineering and computational support.

Source record↗
NASA NTRS2004

Nickel-Hydrogen and Lithium Ion Space Batteries

The tasks of the Electrochemistry Branch of NASA Glenn Research Center are to improve and develop high energy density and rechargeable, life-long batteries. It is with these batteries that people across the globe are able to power their cell phones, laptop computers, and cameras. Here, at NASA Glenn Research Center, the engineers and scientists of the Electrochemistry branch are leading the way in the development of more powerful, long life batteries that can be used to power space shuttles and satellites. As of now, the cutting edge research and development is being done on nickel-hydrogen batteries and lithium ion batteries. Presently, nickel-hydrogen batteries are common types of batteries that are used to power satellites, space stations, and space shuttles, while lithium batteries are mainly used to power smaller appliances such as portable computers and phones. However, the Electrochemistry Branch at NASA Glenn Research Center is focusing more on the development of lithium ion batteries for deep space use. Because of the limitless possibilities, lithium ion batteries can revolutionize the space industry for the better. When compared to nickel-hydrogen batteries, lithium ion batteries possess more advantages than its counterpart. Lithium ion batteries are much smaller than nickel-hydrogen batteries and also put out more power. They are more energy efficient and operate with much more power at a reduced weight than its counterpart. Lithium ion cells are also cheaper to make, possess flexibility that allow for different design modifications. With those statistics in hand, the Electrochemistry Branch of NASA Glenn has decided to shut down its Nickel-Hydrogen testing for lithium ion battery development. Also, the blackout in the summer of 2003 eliminated vital test data, which played a part in shutting down the program. from the nickel-hydrogen batteries and compare it to past data. My other responsibilities include superheating the electrolyte that is used in the nickel-hydrogen cell in a calorimeter to test its performance under various conditions. 1 used a program called Arbin to study my data. The Arbin allows me to look at different parameters such as pressure and time and how they affect the changing temperature of the electrolyte that is being tested. In addition, I had the responsibility of taking apart and modifying battery coolers that would be used. My mentors told me that the batteries kept shutting down, so it was my responsibility to remove excess fan grilles, rotate the fans, and then switch the aluminum standoffs with nylon ones so that the coolers could operate without problems. My last task is to collect all the battery test data and organize them into charts using Microsoft Excel, before the Branch is able to conduct its research on lithium ion batteries. Therefore, during my tenure, it is my responsibility to take down final test data

Reid, Robert O., II↗
NASA NTRS2005

Design and Off-design Performance of 100 Kwe-class Brayton Power Conversion Systems

The NASA Glenn Research Center in-house computer model Closed Cycle Engine Program (CCEP) was used to explore the design trade space and off-design performance characteristics of 100 kWe-class recuperated Closed Brayton Cycle (CBC) power conversion systems. Input variables for a potential design point included the number of operating units (1, 2, 4), cycle peak pressure (0.5, 1, 2 MPa), and turbo-alternator shaft speed (30, 45, 60 kRPM). The design point analysis assumed a fixed turbine inlet temperature (1150 K), compressor inlet temperature (400 K), working-fluid molecular weight (40 g/mol), compressor pressure ratio (2.0), recuperator effectiveness (0.95), and a Sodium-Potassium (NaK) pumped-loop radiator. The design point options were compared on the basis of thermal input power, radiator area, and mass. For a nominal design point with defined Brayton components and radiator area, off-design cases were examined by reducing turbine inlet temperature (as low as 900 K), reducing shaft speed (as low as 50% of nominal), and circulating a percentage (up to 20%) of the compressor exit flow back to the gas cooler. The off-design examination sought approaches to reduce thermal input power without freezing the radiator.

Johnson, Paul K.↗
NASA NTRS2005

Design and Off-Design Performance of 100 kWe-Class Brayton Power Conversion Systems

The NASA Glenn Research Center in-house computer model Closed Cycle Engine Program (CCEP) was used to explore the design trade space and off-design performance characteristics of 100 kWe-class recuperated Closed Brayton Cycle (CBC) power conversion systems. Input variables for a potential design point included the number of operating units (1, 2, 4), cycle peak pressure (0.5, 1, 2 MPa), and turbo-alternator shaft speed (30, 45, 60 kRPM). The design point analysis assumed a fixed turbine inlet temperature (1150 K), compressor inlet temperature (400 K), helium-xenon working-fluid molecular weight (40 g/mol), compressor pressure ratio (2.0), recuperator effectiveness (0.95), and a Sodium-Potassium (NaK) pumped-loop radiator. The design point options were compared on the basis of thermal input power, radiator area, and mass. For a nominal design point with defined Brayton components and radiator area, off-design cases were examined by reducing turbine inlet temperature (as low as 900 K), reducing shaft speed (as low as 50 percent of nominal), and circulating a percentage (up to 20 percent) of the compressor exit flow back to the gas cooler. The off-design examination sought approaches to reduce thermal input power without freezing the radiator.

Johnson, Paul K.↗
NASA NTRS1984

The application of LQR synthesis techniques to the turboshaft engine control problem

A power turbine governor was designed for a recent-technology turboshaft engine coupled to a modern, articulated rotor system using Linear Quadratic Regulator (LQR) and Kalman Filter (KF) techniques. A linear, state-space model of the engine and rotor system was derived for six engine power settings from flight idle to maximum continuous. An integrator was appended to the fuel flow input to reduce the steady-state governor error to zero. Feedback gains were calculated for the system states at each power setting using the LQR technique. The main rotor tip speed state is not measurable, so a Kalman Filter of the rotor was used to estimate this state. The crossover of the system was increased to 10 rad/s compared to 2 rad/sec for a current governor. Initial computer simulations with a nonlinear engine model indicate a significant decrease in power turbine speed variation with the LQR governor compared to a conventional governor.

Pfeil, W. H.↗
NASA NTRS1985

The application of LQR synthesis techniques to the turboshaft engine control problem

A power turbine governor was designed for a recent-technology turboshaft engine coupled to a modern, articulated rotor system using Linear Quadratic Regulator (LQR) and Kalman Filter (KF) techniques. A linear, state-space model of the engine and rotor system was derived for six engine power settings from flight idle to maximum continuous. An integrator was appended to the fuel flow input to reduce the steady-state governor error to zero. Feedback gains were calculated for the system states at each power setting using the LQR technique. The main rotor tip speed state is not measurable, so a Kalman Filter of the rotor was used to estimate this state. The crossover of the system was increased to 10 rad/s compared to 2 rad/sec for a current governor. Initial computer simulations with a nonlinear engine model indicate a significant decrease in power turbine speed variation with the LQR governor compared to a conventional governor.

Pfeil, W. H.↗
NASA NTRS1974

Applications of aerospace technology in the electric power industry

Existing applications of NASA contributions to disciplines such as combustion engineering, mechanical engineering, materials science, quality assurance and computer control are outlined to illustrate how space technology is used in the electric power industry. Corporate strategies to acquire relevant space technology are described.

Johnson, F. D.↗
NASA NTRS2007

Multiphysics Computational Analysis of a Solid-Core Nuclear Thermal Engine Thrust Chamber

The objective of this effort is to develop an efficient and accurate computational heat transfer methodology to predict thermal, fluid, and hydrogen environments for a hypothetical solid-core, nuclear thermal engine - the Small Engine. In addition, the effects of power profile and hydrogen conversion on heat transfer efficiency and thrust performance were also investigated. The computational methodology is based on an unstructured-grid, pressure-based, all speeds, chemically reacting, computational fluid dynamics platform, while formulations of conjugate heat transfer were implemented to describe the heat transfer from solid to hydrogen inside the solid-core reactor. The computational domain covers the entire thrust chamber so that the afore-mentioned heat transfer effects impact the thrust performance directly. The result shows that the computed core-exit gas temperature, specific impulse, and core pressure drop agree well with those of design data for the Small Engine. Finite-rate chemistry is very important in predicting the proper energy balance as naturally occurring hydrogen decomposition is endothermic. Locally strong hydrogen conversion associated with centralized power profile gives poor heat transfer efficiency and lower thrust performance. On the other hand, uniform hydrogen conversion associated with a more uniform radial power profile achieves higher heat transfer efficiency, and higher thrust performance.

Wang, Ten-See↗
NASA NTRS1998

Design and Operating Characteristics of High-Speed, Small-Bore, Angular-Contact Ball Bearings

The computer program SHABERTH was used to analyze 35-mm-bore, angular-contact ball bearings designed and manufactured for high-speed turbomachinery applications. Parametric tests of the bearings were conducted on a high-speed, high-temperature bearing tester and were compared with the computer predictions. Four bearing and cage designs were studied. The bearings were lubricated either by jet lubrication or through the split inner ring with and without outer-ring cooling. The predicted bearing life decreased with increasing speed because of increased operating contact stresses caused by changes in contact angle and centrifugal load. For thrust loads only, the difference in calculated life for the 24 deg. and 30 deg. contact-angle bearings was insignificant. However, for combined loading, the 24 deg. contact-angle bearing gave longer life. For split-inner-ring bearings, optimal operating conditions were obtained with a 24 deg. contact angle and an inner-ring, land-guided cage, using outer-ring cooling in conjunction with low lubricant flow rates. Lower temperature and power losses were obtained with a single-outer-ring, land-guided cage for the 24 deg. contact-angle bearing having a relieved inner ring and partially relieved outer ring. Inner-ring temperatures were independent of lubrication mode and cage design. In comparison with measured values, reasonably good engineering correlation was obtained using the computer program SHABERTH for predicted bearing power loss and for inner- and outer-ring temperatures. The Parker formula for XCAV (used in SHABERTH, a measure of oil volume in the bearing cavity) may need to be refined to reflect bearing lubrication mode, cage design, and location of cage-controlling land.

Pinel, Stanley I.↗
NASA NTRS1990

X-wing fly-by-wire vehicle management system

A complete, computer based, vehicle management system (VMS) for X-Wing aircraft using digital fly-by-wire technology controlling many subsystems and providing functions beyond the classical aircraft flight control system. The vehicle management system receives input signals from a multiplicity of sensors and provides commands to a large number of actuators controlling many subsystems. The VMS includes--segregating flight critical and mission critical factors and providing a greater level of back-up or redundancy for the former; centralizing the computation of functions utilized by several subsystems (e.g. air data, rotor speed, etc.); integrating the control of the flight control functions, the compressor control, the rotor conversion control, vibration alleviation by higher harmonic control, engine power anticipation and self-test, all in the same flight control computer (FCC) hardware units. The VMS uses equivalent redundancy techniques to attain quadruple equivalency levels; includes alternate modes of operation and recovery means to back-up any functions which fail; and uses back-up control software for software redundancy.

Fischer, Jr., William C.↗
NASA NTRS2016

Development of a High-Order Space-Time Matrix-Free Adjoint Solver

The growth in computational power and algorithm development in the past few decades has granted the science and engineering community the ability to simulate flows over complex geometries, thus making Computational Fluid Dynamics (CFD) tools indispensable in analysis and design. Currently, one of the pacing items limiting the utility of CFD for general problems is the prediction of unsteady turbulent ows.1{3 Reynolds-averaged Navier-Stokes (RANS) methods, which predict a time-invariant mean flowfield, struggle to provide consistent predictions when encountering even mild separation, such as the side-of-body separation at a wing-body junction. NASA's Transformative Tools and Technologies project is developing both numerical methods and physical modeling approaches to improve the prediction of separated flows. A major focus of this e ort is efficient methods for resolving the unsteady fluctuations occurring in these flows to provide valuable engineering data of the time-accurate flow field for buffet analysis, vortex shedding, etc. This approach encompasses unsteady RANS (URANS), large-eddy simulations (LES), and hybrid LES-RANS approaches such as Detached Eddy Simulations (DES). These unsteady approaches are inherently more expensive than traditional engineering RANS approaches, hence every e ort to mitigate this cost must be leveraged. Arguably, the most cost-effective approach to improve the efficiency of unsteady methods is the optimal placement of the spatial and temporal degrees of freedom (DOF) using solution-adaptive methods.

Adjoint↗