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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 1,513 records · Page 84

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NASA NTRS1989

An experimental study of memory fault latency

The difficulty with the measurement of fault latency is due to the lack of observability of the fault occurrence and error generation instants in a production environment. The authors describe an experiment, using data from a VAX 11/780 under real workload, to study fault latency in the memory subsystem accurately. Fault latency distributions are generated for stuck-at-zero (s-a-0) and stuck-at-one (s-a-1) permanent fault models. The results show that the mean fault latency of an s-a-0 fault is nearly five times that of the s-a-1 fault. An analysis of variance is performed to quantify the relative influence of different workload measures on the evaluated latency.

Chillarege, Ram↗

NASA NTRS1990

Predictions Of Drag In Viscous Transonic Flow

NASA technical memorandum summarizes results of computations of viscous, transonic flow reported at Viscous Transonic Airfoil Workshop. Results reexamined and analyzed with special emphasis on drag. Compared with each other and with data from experiments. Test cases include attached and separated transonic flows about NACA 0012 airfoil.

Holst, Terry L.↗

NASA NTRS1989

A PBL-radiation model for application to regional numerical weather prediction

Often in the short-range limited-area numerical weather prediction (NWP) of extratropical weather systems the effects of planetary boundary layer (PBL) processes are considered secondarily important. However, it may not be the case for the regional NWP of mesoscale convective systems over the arid and semi-arid highlands of the southwestern and south-central United States in late spring and summer. Over these dry regions, the PBL can grow quite high up into the lower middle troposphere (600 mb) due to very effective solar heating and hence a vigorous air-land thermal interaction can occur. The interaction representing a major heat source for regional dynamical systems can not be ignored. A one-dimensional PBL-radiation model was developed. The model PBL consists of a constant-flux surface layer superposed with a well-mixed (Ekman) layer. The vertical eddy mixing coefficients for heat and momentum in the surface layer are determined according to the surface similarity theory, while their vertical profiles in the Ekman layer are specified with a cubic polynomial. Prognostic equations are used for predicting the height of the nonneutral PBL. The atmospheric radiation is parameterized to define the surface heat source/sink for the growth and decay of the PBL. A series of real-data numerical experiments has been carried out to obtain a physical understanding how the model performs under various atmospheric and surface conditions. This one-dimensional model will eventually be incorporated into a mesoscale prediction system. The ultimate goal of this research is to improve the NWP of mesoscale convective storms over land.

Chang, Chia-Bo↗

NASA NTRS1990

Cockpit Ocular Recording System (CORS)

The overall goal was the development of a Cockpit Ocular Recording System (CORS). Four tasks were used: (1) the development of the system; (2) the experimentation and improvement of the system; (3) demonstrations of the working system; and (4) system documentation. Overall, the prototype represents a workable and flexibly designed CORS system. For the most part, the hardware use for the prototype system is off-the-shelf. All of the following software was developed specifically: (1) setup software that the user specifies the cockpit configuration and identifies possible areas in which the pilot will look; (2) sensing software which integrates the 60 Hz data from the oculometer and heat orientation sensing unit; (3) processing software which applies a spatiotemporal filter to the lookpoint data to determine fixation/dwell positions; (4) data recording output routines; and (5) playback software which allows the user to retrieve and analyze the data. Several experiments were performed to verify the system accuracy and quantify system deficiencies. These tests resulted in recommendations for any future system that might be constructed.

Rothenheber, Edward↗

NASA NTRS1990

The radiation budget of stratocumulus clouds measured by tethered balloon instrumentation: Variability of flux measurements

Measurements of longwave and shortwave radiation were made using an instrument package on the NASA tethered balloon during the FIRE Marine Stratocumulus experiment. Radiation data from two pairs of pyranometers were used to obtain vertical profiles of the near-infrared and total solar fluxes through the boundary layer, while a pair of pyrgeometers supplied measurements of the longwave fluxes in the cloud layer. The radiation observations were analyzed to determine heating rates and to measure the radiative energy budget inside the stratocumulus clouds during several tethered balloon flights. The radiation fields in the cloud layer were also simulated by a two-stream radiative transfer model, which used cloud optical properties derived from microphysical measurements and Mie scattering theory.

Duda, David P.↗

NASA NTRS1989

Earth Radiation Budget Experiment (ERBE) archival and April 1985 results

This paper describes the Earth Radiation Budget Experiment (ERBE) data products being made available to the community. The Science Team used ten validation criteria to judge the acceptability of the data for archival. These criteria are listed, and uncertainty estimates based on them for four typical data products are presented. A brief description of the radiation budget for April 1985 from the combined data of ERBE and NOAA-9 concludes this paper.

Barkstrom, B.↗

NASA NTRS1990

Estimation of multidimensional precipitation parameters by areal estimates of oceanic rainfall

The parameters of the multidimensional precipitation model proposed by Waymire et al. (1984) are estimated using the areal-averaged radar measurements of precipitation of the Global Atlantic Tropical Experiment (GATE) data set. The procedure followed was the fitting of the first- and second-order moments at different aggregation scales by nonlinear regression techniques. The numerical estimates of the parameters using different subsets of GATE information were reasonably stable, i.e., they were not affected by changes of the area-averaging size, temporal length of the records, and percentage of areal coverage of rainfall. This suggests that the estimation procedure is relatively robust and suitable to estimate the parameters of the multidimensional model in areas of sparse density of rain gages. The use of the space-time spectrum of rainfall to help in the determination of sampling errors due to intermittent visits of future space-borne low-altitude sensors of precipitation is also discussed.

Valdes, J. B.↗

NASA NTRS1990

Ultrahigh-pressure melting of lead - A multidisciplinary study

Measurements of the melting temperatures of lead, carried out to pressures of 1 megabar and temperatures near 4000 kelvin by means of a laser-heated diamond cell are in excellent agreement with the results of previous shock-wave experiments. The data are analyzed by means of first principles quantum mechanical calculations, and the agreement documents the reliability of current experimental and theoretical techniques for studies of melting at ultrahigh pressures. These studies have potentially wide-ranging applications from planetary science to condensed matter physics.

Godwal, B. K.↗

NASA NTRS1990

Comparison of cloud forcing derived from the Earth Radiation Budget Experiment with that simulated by the NCAR Community Climate Model

The cloud radiative forcing derived from the Earth Radiation Budget Experiment (ERBE) data was compared with cloud forcing simulated by a T42 version of the NCAR Community Climate Model (CCM). The comparison indicates a number of deficiencies in the CCM. Namely, it is shown that the model emits substantially more long-wave radiation than is observed by ERBE. This overestimation is attributed to two model characteristics: (1) the model is too dry and thus reduces the greenhouse longwave radiation effect of the atmosphere (permitting more longwave radiation to escape into space); and (2) the effective high cloud amount is quite small in the model.

Kiehl, J. T.↗

NASA NTRS1990

Extended time observations of California marine stratocumulus clouds from GOES for July 1983-1987

One of the goals of the First ISCCP Regional Experiment (FIRE) is to relate the relatively small scale (spatial and temporal) Intensive Field Observations (IFO) to larger time and space domains embodied in the Extended Time Observations (ETO) phase of the experiment. The data analyzed as part of the ETO are to be used to determine some climatological features of the limited area which encompasses the Marine Stratocumulus IFO which took place between 29 June and 19 July 1987 off the coast of southern California.

Minnis, Patrick↗

NASA NTRS1989

An inventory of four-dimensional data sets for the earth sciences

The wide variety of data available to the diligent researcher and the myriad paths to obtaining it are emphasized. This inventory is an attempt to make accessible much of the four-dimensional data available in the world. In this quick-look catalog are listed separate data sets (Data Sets sections), sources of data including centers and large data bases (Sources section), and some data expected to be available in the future (Future Data section). In the Data Sets section, individual data sets are arranged alphabetically by institution, with those archived in the U.S.A. listed first, followed by those found elsewhere. The Sources section includes large data bases, centers, and directories. Sources are arranged alphabetically by country. This section is followed by a Future Data section which is a collection of data sets, experiments, and other future developments of which we are cognizant. A collection of further information and order blanks provided by some of the archiving institutions are presented in the appendix.

Gregory, Terri↗

NASA NTRS1991

Mars manned fusion spaceship

Fusion Propulsion has an enormous potential for space exploration in the near future. In the twenty-first century, a usable and efficient fusion rocket will be developed and in use. Because of the great distance between other planets and Earth, efficient use of time, fuel, and payload is essential. A nuclear spaceship would provide greater fuel efficiency, less travel time, and a larger payload. Extended missions would give more time for research, experiments, and data acquisition. With the extended mission time, a need for an artificial environment exists. The topics of magnetic fusion propulsion, living modules, artificial gravity, mass distribution, space connection, and orbital transfer to Mars are discussed. The propulsion system is a magnetic fusion reactor based on a tandem mirror design. This allows a faster, shorter trip time and a large thrust to weight ratio. The fuel proposed is a mixture of deuterium and helium-3. Helium-3 can be obtained from lunar mining. There will be minimal external radiation from the reactor resulting in a safe, efficient propulsion system.

Hedrick, James↗

NASA NTRS1991

Seasonal cloud-radiative forcing over land and ocean derived from ERBE satellites

Earth Radiation Budget Experiment (ERBE) data are analyzed to determine seasonal variations of radiative parameters. Particular attention is given to annual variations of the top-of-the atmosphere zonally averaged outgoing long-wave (LW) and absorbed short-wave (SW) flux, as well as the short- and long-wave components of cloud-radiative forcing. The ERBE results reveal significant seasonal variations in both outgoing LW and absorbed SW flux, and a pronounced difference between oceanic and continental surfaces.

Harrison, Edwin F.↗

NASA NTRS1990

Airborne gamma radiation soil moisture measurements over short flight lines

Results are presented on airborne gamma radiation measurements of soil moisture condition, carried out along short flight lines as part of the First International Satellite Land Surface Climatology Project Field Experiment (FIFE). Data were collected over an area in Kansas during the summers of 1987 and 1989. The airborne surveys, together with ground measurements, provide the most comprehensive set of airborne and ground truth data available in the U.S. for calibrating and evaluating airborne gamma flight lines. Analysis showed that, using standard National Weather Service weights for the K, Tl, and Gc radiation windows, the airborne soil moisture estimates for the FIFE lines had a root mean square error of no greater than 3.0 percent soil moisture. The soil moisture estimates for sections having acquisition time of at least 15 sec were found to be reliable.

Peck, Eugene L.↗

NASA NTRS1989

In flight demonstration of mass property identification and jet plume interaction on the AeroAssist Flight Experiment

Algorithms have been developed for in-flight demonstration of spacecraft mass, center of mass, and inertia matrix which autonomously measure mass properties as they change in-flight due to consumable expenditures, payload deployment/retrieval, and docking. The testing of these algorithms can be conducted by means of a mass-properties estimator, which is a second-order nonlinear filter resembling an extended Kalman filter. The AeroAssist Flight Experiment, which will demonstrate the use of the earth's atmosphere to assist orbital changes, will carry the Rarefied-flow Aerodynamic Measurement Experiment (RAME); data taken by RAME will be used by the mass-properties estimator to ascertain spacecraft mass properties, and estimates from this filter will be compared to predicted values of the mass properties to validate the estimator.

Bergmann, Edward V.↗

NASA NTRS1989

A mesoscale analysis of the pre-storm environment on the 17 June 1986 COHMEX day

The study presented utilized special mesoscale Cooperative Huntsville Meteorological Experiment (COHMEX) data to understand the evolution of the preconvective environment on June 17, 1986. Using the special mesoscale COHMEX data, several mechanisms for triggering the convection are investigated. Afternoon heating probably was a major factor as observed noontime temperatures were near the sounding-derived convection temperatures. The special surface network revealed a quasi-stationary area of convergence not aligned with the front that may be associated with the orography of the area. This study demonstrates that rapid, small scale atmospheric variations preceded convective development on June 17, 1986.

Fuelberg, Henry E.↗

NASA NTRS1991

Renormalization group analysis of anisotropic diffusion in turbulent shear flows

The renormalization group is applied to compute anisotropic corrections to the scalar eddy diffusivity representation of turbulent diffusion of a passive scalar. The corrections are linear in the mean velocity gradients. All model constants are computed theoretically. A form of the theory valid at arbitrary Reynolds number is derived. The theory applies only when convection of the velocity-scalar correlation can be neglected. A ratio of diffusivity components, found experimentally to have a nearly constant value in a variety of shear flows, is computed theoretically for flows in a certain state of equilibrium. The theoretical value is well within the fairly narrow range of experimentally observed values. Theoretical predictions of this diffusivity ratio are also compared with data from experiments and direct numerical simulations of homogeneous shear flows with constant velocity and scalar gradients.

Rubinstein, Robert↗

NASA NTRS1991

An ionospheric signature of possible enhanced magnetic field merging on the dayside magnetopause

The high temporal and spatial resolution of the Polar Anglo-American Conjugate Experiment radar data have permitted the evolution and formation of a transient plasma velocity signature in the cusp ionosphere to be studied. The signature satisfies a number of the predictions of theoretical models that require the formation of vortices. A much weaker enhancement in velocities is shown in the Northern Hemisphere, which is consistent with the vector superposition arguments presented by Crooker (1979) for the antiparallel merging model.

Pinnock, M.↗