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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Development of an unsteady aerodynamic analysis for finite-deflection subsonic cascades

An unsteady potential flow analysis, which accounts for the effects of blade geometry and steady turning, was developed to predict aerodynamic forces and moments associated with free vibration or flutter phenomena in the fan, compressor, or turbine stages of modern jet engines. Based on the assumption of small amplitude blade motions, the unsteady flow is governed by linear equations with variable coefficients which depend on the underlying steady low. These equations were approximated using difference expressions determined from an implicit least squares development and applicable on arbitrary grids. The resulting linear system of algebraic equations is block tridiagonal, which permits an efficient, direct (i.e., noniterative) solution. The solution procedure was extended to treat blades with rounded or blunt edges at incidence relative to the inlet flow.

Verdon, J. M.↗
NASA NTRS1980

Superthermal electrons and Bernstein waves in Jupiter's inner magnetosphere

A theoretical model for generation of banded electrostatic emissions by low density, superthermal electrons is developed for application to Jupiter's magnetosphere. The model employs a power law form for the energy dependence and a loss cone pitch angle distribution of the superthermals to drive convective instability of Bernstein modes. A direct correspondence between spectral features of the 3/2 band and resonant superthermal electrons is found. The concept of a critical flux of resonant electrons able to provide 10 e-foldings of electric field amplification yields an explicit relation in terms of the background thermal electron pressure. This result is used to construct a theoretical/empirical model of thermal electron density and temperature from 6-20 Jupiter radii in the Jovian magnetosphere which suggests that the electron temperature is less than the ion temperature which is approximately equal to 10 times the electron temperature in this region. Finally, wave ray paths are computed for propagation in the magnetic equator and in the magnetic meridional plane of a dipole magnetic field. These ray paths suggest that intense wave activity is tightly confined to a small latitudinal extent, less than + or - approximately 4 deg, about the magnetic equator.

Barbosa, D. D.↗
NASA NTRS1981

New technologies - How to assess environmental effects

A method is provided for assessing the environmental effects of a room-and-pillar mining system (RP) and a new hydraulic borehole mining system (HBM). Before environmental assessment can begin, each technology is defined in terms of its engineering characteristics at both the conceptual and preliminary design stages. The mining sites are also described in order to identify the significant advantages and constraints for each system. This can be a basic physical and biological survey of the region at the conceptual stage, but a more specific representation of site characteristics is required at the preliminary stage. Assessment of potential environmental effects of each system at the conceptual design is critical to its hardware development and application. A checklist can be used to compare and identify the negative impacts of each method, outlining the resource affected, the type of impact involved, and the exact activity causing that impact. At the preliminary design stage, these impacts should be evaluated as a result of either utilization or alteration. Underground coal mining systems have three major utilization impacts - the total area disturbed, the total water resources withdrawn from other uses, and the overall energy efficiency of the process - and one major alteration impact - the degradation of water quality by sedimentation and acid contamination. A comparison of the RP and HBM systems shows the HBM to be an environmentally less desirable system for the Central Appalachia region.

Sullivan, P. J.↗
NASA NTRS1981

Interplanetary trajectory optimization

A procedure for minimizing total impulsive Delta-V for constrained multiple-flyby trajectories, which was originally developed for application to satellite tours, has been modified for application to interplanetary trajectories. The modification includes adding to the cost function the Delta-V required to escape from a parking orbit about the launch planet and the Delta-V required for insertion into orbit about the arrival planet. The hyperbolic excess velocity vector with respect to the launch planet and the launch date have been added to the set of independent variables for the optimization. Each trajectory originates at departure from the parking orbit rather than at a fixed position in space, as is the case for the satellite tour application. The multi-conic trajectory propagation techniques and the Newton optimization algorithm of the original method have been retained. Examples of the application of this new method are given for several types of Galileo interplanetary trajectory options, including Mars powered flyby, broken plane, VEGA, and Delta VEGA trajectories.

Damario, L. A.↗
NASA NTRS1981

Antenna pattern modification for single reflector antennas

The problem of correcting the antenna temperatures observed with a single reflector is addressed from two viewpoints with emphasis on decreasing the level of the side lobes without greatly amplifying the noise. One viewpoint is that of matrix operations where the elements of the matrix are integrals of the antenna pattern. This formulation is directly applicable to developing algorithms. The other is that of an analysis of the problem by treating the antenna as a spatial filter and using Fourier transforms of the antenna pattern. This approach leads to an understanding of the problem, but is not suitable for performing calculations. The method developed can be used to correct data from mechanically-scanned microwave instruments that view Earth from space.

Milman, A. S.↗
NASA NTRS1981

A quasi-Newton procedure for identifying pilot-related parameters of the optimal control model

The development and application of a quasi-Newton gradient search procedure for identifying independent pilot related parameters of the optimal control model for pilot/vehicle systems is reported. A sensitivity analysis procedure which determines whether a given model parameter is required to match a specific experimental result, and which experimentally induced parameter changes are required to account for behavioral and performance differences, is described. Application of the identification scheme to training effects in a manual control task is described.

Levison, W. H.↗
NASA NTRS1981

Gallium phosphide high temperature diodes

High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics.

Chaffin, R. J.↗
NASA NTRS1981

Bootlace catenary concept for antenna shape control

A preliminary design of the microwave radiometer spacecraft (MRS) using the bootlace catenary shaping concept was developed. The application of this radically different design for shape control of the antenna membrane was assessed and possible sources of inaccuracies and errors were investigated.

Ramsey, J. H.↗
NASA NTRS1982

Survey of multi-function display and control technology

The NASA orbiter spacecraft incorporates a complex array of systems, displays and controls. The incorporation of discrete dedicated controls into a multi-function display and control system (MFDCS) offers the potential for savings in weight, power, panel space and crew training time. The technology applicable to the development of a MFDCS for orbiter application is surveyed. Technology thought to be applicable presently or in the next five years is highlighted. Areas discussed include display media, data handling and processing, controls and operator interactions and the human factors considerations which are involved in a MFDCS design. Several examples of applicable MFDCS technology are described.

Spiger, R. J.↗
NASA NTRS1982

Environmental control systems

Materials illustrating a presentation on environmental control systems for electric flight systems are presented. The major technology issues, major development and application steps, the role of NASA, and required flight testing are outlined.

Hrach, F.↗
NASA NTRS1982

Multiplexed extrinsic silicon detector array

Multiplexed extrinsic silicon detector arrays for infrared applications were developed and tested. Cryogenic electronics are discussed. Ambient temperature electronics are also discussed.

Yee, J. F.↗
NASA NTRS1982

Applying modeling Results in designing a global tropospheric experiment

A set of field experiments and advanced modeling studies which provide a strategy for a program of global tropospheric experiments was identified. An expanded effort to develop space applications for trospheric air quality monitoring and studies was recommended. The tropospheric ozone, carbon, nitrogen, and sulfur cycles are addressed. Stratospheric-tropospheric exchange is discussed. Fast photochemical processes in the free troposphere are considered.

Source record↗
NASA NTRS1982

Flow Visualization and Laser Velocimetry for Wind Tunnels

The need for flow visualization and laser velocimetry were discussed. The purpose was threefold: (1) provide a state-of-the-art overview; (2) provide a forum for industry, universities, and government agencies to address problems in developing useful and productive flow visualization and laser velocimetry measurement techniques; and (3) provide discussion of recent developments and applications of flow visualization and laser velocimetry measurement techniques and instrumentation systems for wind tunnels including the 0.3-Meter Transonic Cryogenic Tunnel.

Hunter, W. W., Jr.↗
NASA NTRS1982

An exact zooming method for finite element analyses

An exact zooming technique which employs static condensation and exact structural reanalysis methods was developed. Successive application of static condensation reduces the system to one that is only associated with the degrees of freedom (dof) of the original model. Application of an exact static reanalysis technique permits the displacements at the dof of the original model that are contained in the zoomed portion of the structure to be obtained first. The response external to the zoom, as well as the response of additional dof within various levels of zooming, is computed. With the triangular factor of the stiffness matrix of the original system available, this approach involves only the solution of a system of equations of small order.

Hirai, I.↗
NASA NTRS1981

An experimental study of SO3 dissociation as a mechanism for converting and transporting solar energy

The high temperature catalytic dissocation of SO3 is an important chemical process being considered in the development and application of solar-thermal energy conversion, transport, and storage systems. A facility for evaluating chemical converter-heat exchangers at temperatures to 1000 C with high flow rates of gaseous SO3 feedstock has been assembled and operated on the NMSU campus. Several quartz and metal reactors containing different catalyst configurations have been tested. Descriptions of the test facility and of the reactors are given along with a presentation and discussion of experimental results.

Mccrary, J. H.↗
NASA NTRS1981

A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading

The present paper is concerned with the development and application of an analytical model of cyclic crack growth that includes the effects of crack closure. The model was based on a concept like the Dugdale model, but was modified to leave plastically deformed material in the wake of the advancing crack tip. The model was used to correlate crack growth rates under constant-amplitude loading and to predict crack growth under aircraft spectrum loading on 2219-T851 aluminum alloy plate material. The predicted crack growth lives agreed well with experimental data. The ratio of predicted-to-experimental lives ranged from 0.66 to 1.48.

Newman, J. C., Jr.↗
NASA NTRS1982

Velocity and attenuation of sound in arterial tissues

The velocity of sound in excised human and canine arterial tissues is measured in order to serve as a basis for the development and application of ultrasonic techniques for the diagnosis of atherosclerotic lesions. Measurements of sound velocity at different regions of 11 human and six canine aortas were made by a time delay spectrometer technique at frequencies from 2 to 10 MHz, and compared with ultrasonic attenuation parameters and the results of biochemical assays. Sound velocity is found to increase with increasing attenuation at all frequencies, and with increasing collagen content. A strong dependence of sound velocity on cholesterol content or low calcium contents is not observed, although velocities of up to 2000 m/sec are observed in highly organized calcified lesions. A decrease in velocity with decreasing temperature is also noted. It is thus concluded that it is principally the differences in tissue collagen levels that contribute to image formation according to sound velocity.

Rooney, J. A.↗
NASA NTRS1982

Multifuel evaluation of rich/quench/lean combustor

The fuel flexible combustor technology was developed for application to the Model 570-K industrial gas turbine engine. The technology, to achieve emission goals, emphasizes dry NOx reduction methods. Due to the high levels of fuel-bound nitrogen (FBN), control of NOx can be effected through a staged combustor with a rich initial combustion zone. A rich/quench/lean variable geometry combustor utilizes the technology presented to achieve low NOx from alternate fuels containing FBN. The results focus on emissions and durability for multifuel operation.

Notardonato, J. J.↗