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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Description of a 20 kilohertz power distribution system

A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution links multiphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

Hansen, I. G.↗
NASA NTRS1987

RE-1000 free-piston Stirling engine hydraulic output system description

The NASA Lewis Research Center was involved in free-piston Stirling engine research since 1976. Most of the work performed in-house was related to characterization of the RE-1000 engine. The data collected from the RE-1000 tests were intended to provide a data base for the validation of Stirling cycle simulations. The RE-1000 was originally build with a dashpot load system which did not convert the output of the engine into useful power, but was merely used as a load for the engine to work against during testing. As part of the interagency program between NASA Lewis and the Oak Ridge National Laboratory, (ORNL), the RE-1000 was converted into a configuration that produces useable hydraulic power. A goal of the hydraulic output conversion effort was to retain the same thermodynamic cycle that existed with the dashpot loaded engine. It was required that the design must provide a hermetic seal between the hydraulic fluid and the working gas of the engine. The design was completed and the hardware was fabricated. The RE-1000 was modified in 1985 to the hydraulic output configuration. The early part of the RE-1000 hydraulic output program consisted of modifying hardware and software to allow the engine to run at steady-state conditions. A complete description of the engine is presented in sufficient detail so that the device can be simulated on a computer. Tables are presented showing the masses of the oscillating components and key dimensions needed for modeling purposes. Graphs are used to indicate the spring rate of the diaphragms used to separate the helium of the working and bounce space from the hydraulic fluid.

Schreiber, Jeffrey G.↗
NASA NTRS1988

Description of data on the Nimbus 7 LIMS map archive tape: Water vapor and nitrogen dioxide

Described is the process by which the analysis of the Limb Infrared Monitor of the Stratosphere (LIMS) experiment data were used to produce estimates of synoptic maps of water vapor and nitrogen dioxide. In addition to a detailed description of the analysis procedure, also discussed are several interesting features in the data which are used to demonstrate how the analysis procedure produced the final maps and how one can estimate the uncertainties in the maps. In addition, features in the analysis are noted that would influence how one might use, or interpret, the results. These include subjects such as smoothing and the interpretation of wave components.

Haggard, Kenneth V.↗
NASA NTRS1988

Predictive wall adjustment strategy for two-dimensional flexible walled adaptive wind tunnel: A detailed description of the first one-step method

Following the realization that a simple iterative strategy for bringing the flexible walls of two-dimensional test sections to streamline contours was too slow for practical use, Judd proposed, developed, and placed into service what was the first Predictive Strategy. The Predictive Strategy reduced by 75 percent or more the number of iterations of wall shapes, and therefore the tunnel run-time overhead attributable to the streamlining process, required to reach satisfactory streamlines. The procedures of the Strategy are embodied in the FORTRAN subroutine WAS (standing for Wall Adjustment Strategy) which is written in general form. The essentials of the test section hardware, followed by the underlying aerodynamic theory which forms the basis of the Strategy, are briefly described. The subroutine is then presented as the Appendix, broken down into segments with descriptions of the numerical operations underway in each, with definitions of variables.

Wolf, Stephen W. D.↗
NASA NTRS1988

A description of an automated database comparison program

An interactive FORTRAN computer comparison program designed to automatically locate regions of incongruity between two databases is described. The software, guided by user input parameters, incrementally compares the databases and generates plots of these regions in the databases which do not compare within a specified tolerance. Additionally, tools are provided within the software which enable the user to statistically reduce the number of data points in the databases compared. To facilitate the description of these tools, the procedures used to compare two aerodynamic databases for an F-18A fighter aircraft are detailed.

Mcminn, John D.↗
NASA NTRS1988

A cyclic ground test of an ion auxiliary propulsion system: Description and operational considerations

The Ion Auxiliary Propulsion System (IAPS) experiment is designed for launch on an Air Force Space Test Program satellite (NASA-TM-78859; AIAA Paper No. 78-647). The primary objective of the experiment is to flight qualify the 8 cm mercury ion thruster system for stationkeeping applications. Secondary objectives are measuring the interactions between operating ion thruster systems and host spacecraft, and confirming the design performance of the thruster systems. Two complete 8 cm mercury ion thruster subsystems will be flown. One of these will be operated for 2557 on and off cycles and 7057 hours at full thrust. Tests are currently under way in support of the IAPS flight experiment. In this test an IAPS thruster is being operated through a series of startup/run/shut-down cycles which simulate thruster operation during the planned flight experiment. A test facility description and operational considerations of this testing using an engineering model 8 cm thruster (S/N 905) is the subject of this paper. Final results will be published at a later date when the ground test has been concluded.

Ling, Jerri S.↗
NASA NTRS1988

Appendices to the model description document for a computer program for the emulation/simulation of a space station environmental control and life support system

A Model Description Document for the Emulation Simulation Computer Model was already published. The model consisted of a detailed model (emulation) of a SAWD CO2 removal subsystem which operated with much less detailed (simulation) models of a cabin, crew, and condensing and sensible heat exchangers. The purpose was to explore the utility of such an emulation simulation combination in the design, development, and test of a piece of ARS hardware, SAWD. Extensions to this original effort are presented. The first extension is an update of the model to reflect changes in the SAWD control logic which resulted from test. Also, slight changes were also made to the SAWD model to permit restarting and to improve the iteration technique. The second extension is the development of simulation models for more pieces of air and water processing equipment. Models are presented for: EDC, Molecular Sieve, Bosch, Sabatier, a new condensing heat exchanger, SPE, SFWES, Catalytic Oxidizer, and multifiltration. The third extension is to create two system simulations using these models. The first system presented consists of one air and one water processing system. The second consists of a potential air revitalization system.

Yanosy, James L.↗
NASA NTRS1988

The CSM testbed matrix processors internal logic and dataflow descriptions

This report constitutes the final report for subtask 1 of Task 5 of NASA Contract NAS1-18444, Computational Structural Mechanics (CSM) Research. This report contains a detailed description of the coded workings of selected CSM Testbed matrix processors (i.e., TOPO, K, INV, SSOL) and of the arithmetic utility processor AUS. These processors and the current sparse matrix data structures are studied and documented. Items examined include: details of the data structures, interdependence of data structures, data-blocking logic in the data structures, processor data flow and architecture, and processor algorithmic logic flow.

Regelbrugge, Marc E.↗
NASA NTRS1988

Toward a descriptive model of solar particles in the heliosphere

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made.

Shea, M. A.↗
NASA NTRS1989

An optical model description of momentum transfer in heavy ion collisions

An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is identified as the longitudinal momentum downshift of the projectile. Predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is discussed.

Khan, F.↗
NASA NTRS1988

Nonadiabatic, momentum-dependent, and energy-dependent corrections in the effective-potential description for low-energy scattering of spinless systems - Their relations and validity

In the effective-potential description for low-energy scattering involving a spinless complex (a body with internal structure), the nonadiabatic corrections are sometimes disguised in momentum-dependent terms. These are distinct from energy-dependent corrections. A general procedure is given here by which all the momentum-dependent corrections can be converted into nonadiabatic corrections in truly local form. Circumstances under which an expansion of the effective potential, in terms of the adiabatic term plus nonadiabatic and energy-dependent corrections is allowed and forbidden, are discussed. An example for the latter is in the case of near degeneracy in the spectrum of the complex or in the extrapolation of the effective potential to short-distance behavior. This indicates that certain claims of 'saturation effect' at short distances in low-energy electron-atom scattering are invalid.

Au, C. K.↗
NASA NTRS1988

Description of substorms in the tail incorporating boundary layer and neutral line effects

A description of the substorm expansion phase that includes the formation of a neutral line in the relatively near-earth portion of the tail plasma sheet and phenomena observed in the plasma sheet boundary layer (PSBL) is proposed. Specifically, it is proposed that substorm onset results from the formation of a neutral line within the preexisting source region for the PSBL. The source region is presumably the tail current sheet, which is suggested to extend well earthward of 80 earth radii. Both before and after the neutral line forms, auroral field-aligned currents and large ion flows remain confined to the PSBL earthward of the source region.

Lyons, L. R.↗
NASA NTRS1989

An asymptotic description of transient settling and ultrafiltration of colloidal dispersions

The present model for the sedimentation of colloidal systems includes a diffusion term in the governing equation which, in the regions above the sediment, acts as small perturbation to the Kynch (1952) theory. Within the sediment, diffusion is comparable to convection due to the the high solid volume fraction. An application of the method of matched asymptotic expansions to the conservation equation allows a complete description of the settling process to be formulated, with specific attention to volume-fraction evolution in the sediment.

Davis, K. E.↗
NASA NTRS1989

Product specification documentation standard and Data Item Descriptions (DID). Volume of the information system life-cycle and documentation standards, volume 3

This is the third of five volumes on Information System Life-Cycle and Documentation Standards which present a well organized, easily used standard for providing technical information needed for developing information systems, components, and related processes. This volume states the Software Management and Assurance Program documentation standard for a product specification document and for data item descriptions. The framework can be applied to any NASA information system, software, hardware, operational procedures components, and related processes.

Callender, E. David↗
NASA NTRS1990

PROTEUS two-dimensional Navier-Stokes computer code, version 1.0. Volume 1: Analysis description

A new computer code was developed to solve the two-dimensional or axisymmetric, Reynolds averaged, unsteady compressible Navier-Stokes equations in strong conservation law form. The thin-layer or Euler equations may also be solved. Turbulence is modeled using an algebraic eddy viscosity model. The objective was to develop a code for aerospace applications that is easy to use and easy to modify. Code readability, modularity, and documentation were emphasized. The equations are written in nonorthogonal body-fitted coordinates, and solved by marching in time using a fully-coupled alternating direction-implicit procedure with generalized first- or second-order time differencing. All terms are linearized using second-order Taylor series. The boundary conditions are treated implicitly, and may be steady, unsteady, or spatially periodic. Simple Cartesian or polar grids may be generated internally by the program. More complex geometries require an externally generated computational coordinate system. The documentation is divided into three volumes. Volume 1 is the Analysis Description, and describes in detail the governing equations, the turbulence model, the linearization of the equations and boundary conditions, the time and space differencing formulas, the ADI solution procedure, and the artificial viscosity models.

Towne, Charles E.↗
NASA NTRS1990

A functional description of the advanced receiver

The breadboard Advanced Receiver 2 (ARX 2) that is currently being built for future use in NASA's Deep Space Network (DSN) is described. The hybrid analog/digital receiver performs multiple functions including carrier, subcarrier, and symbol synchronization. Tracking can be achieved for residual, suppressed, or hybrid carriers and for both sinusoidal and square-wave subcarriers. Other functions such as time-tagged Doppler extraction and monitor/control are also discussed, including acquisition algorithms and lock-detection schemes. System requirements are specified and a functional description of the ARX 2 is presented. The various digital signal-processing algorithms used are also discussed and illustrated with block diagrams.

Hinedi, S.↗
NASA NTRS1990

Mark 4-A DSCC (Magellan-era) telemetry system description

An update to the description of the Deep Space Communications Complex portion of the Mark 4-A Telemetry system is given. This system is currently implemented at all signal processing centers. The upgrade of the telemetry system was undertaken primarily in support of the Voyager-Neptune Encounter and the Magellan mission. The Mark 3 Telemetry System is the predecessor of the Mark 4-A system.

Ross, D. L.↗