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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Homogeneous condensation - Freezing nucleation rate measurements for small water droplets in an expansion cloud chamber

Experimental data on ice nucleation, presented in an earlier paper, are analyzed to yield information about the homogeneous nucleation rate of ice from supercooled liquid and the heights of energy barriers to that nucleation. The experiment consisted of using an expansion cloud chamber to nucleate from the vapor a cloud of supercooled pure water drops and the observation of the fraction of drops which subsequently froze. The analysis employed standard classical homogeneous nucleation theory. The data are used to extract the first experimental measurement (albeit indirect) of the activation energy for the transfer of a water molecule across the liquid-ice interface at temperatures near -40 C. The results provide further evidence that the local liquid structure becomes more icelike as the temperature is lowered.

Hagen, D. E.↗
NASA NTRS1995

Observation and modeling of compressional Pi 3 magnetic pulsations

Compressional magnetic pulsations with irregular waveforms and periods longer than 150 s (here termed Pi 3) have been studied by using data from Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) and GOES 5 and 6 in the dayside magnetosphere and compared with signatures on the ground at low latitudes by using data from Kakioka station (L = 1.25). On the ground, the pulsations appear in the horizontal component. A study of 17 such concurrent events during a 2-month period in 1986 reveals the following pulsation characteristics. (1) The peak-to-peak amplitudes in space (delta B(sub T)) and on the ground (delta H) are comparable and are in the range of 0.5-7 nT. (2) On the ground the pulsations can be seen at all local times, even at midnight, while at geostationary orbit they are observed only on the dayside with a clear amplitude maximum at noon. (3) The pulsations on the ground lag those observed by CCE near local noon, and the lag increases as the local time separation between CCE and the ground station increases. The time lag is 1-2 min longer when the ground station is on the nightside than when it is on the dayside. (4) The time lag between pulsations observed at geostationary orbit and near noon by CCE varies systematically with local time and is about 2 min per 6 hours of local time separation. These observations indicate that some nightside pulsations in the Pi 3 band have dayside origins. The position dependence of the pulsation amplitude can be explained well by changes in the magnetopause current, which are in turn presumably caused by changes in the solar wind dynamic pressure. The time lags observed in space are consistent with signal propagation in the MHD fast mode, but the variation in space-ground time lags with ground station local time must be attributed to another mechanism.

Matsuoka, Hitoshi↗
NASA NTRSDate not supplied

Anticipating Hazard Impacts through Capacity Building and Co-development

Improving forecast accuracy, extending lead time, understanding hazard susceptibility, and integrating exposure and vulnerability data to generate impact-based forecasts are critical in mitigating disaster impacts. These efforts enable anticipatory action through enhancing the efficacy of early warning systems to assess potential multi-dimensional hazard impacts. In response to this need, SERVIR has co-developed a series of hazard services providing vital information from national to regional scales. This poster showcases examples of geospatial services co-developed with partners through a capacity building approach, supporting the establishment of hazard early warning / early action systems. These services integrate multidimensional vulnerability and exposure data to comprehensively assess impacts. Furthermore, these services demonstrate how co-development and capacity building can advance the development of impact-based forecasts and multi-hazards services. By prioritizing collaboration, human insights, local knowledge, capacity building, and employing applied science approaches in geospatial service development, this work has helped create inclusive and customized solutions. These solutions are tailored to meet the needs of local communities and are readily adaptable into decision-making processes.

weather↗
NASA NTRS2000

Significant Centers of Tectonic Activity as Identified by Wrinkle Ridges for the Western Hemisphere of Mars

The western hemisphere region of Mars has been the site of numerous scientific investigations regarding its tectonic evolution. For this region of Mars, the dominant tectonic region is the Tharsis province. Tharsis is characterized by an enormous system of radiating grabens and a circumferential system of wrinkle ridges. Past investigations of grabens associated with Tharsis have identified specific centers of tectonic activity. A recent structural analysis of the western hemisphere region of Mars which includes the Tharsis region, utilized 25,000 structures to determine the history of local and regional centers of tectonic activity based primarily on the spatial and temporal relationships of extensional features. This investigation revealed that Tharsis is more structurally complex (heterogeneous) than has been previously identified: it consists of numerous regional and local centers of tectonic activity (some are more dominant and/or more long lived than others). Here we use the same approach as Anderson et al. to determine whether the centers of tectonic activity that formed the extensional features also contributed to wrinkle ridge (compressional) formation.

Anderson, R.C.↗
NASA NTRS2005

Global Admittance Estimates of Elastic and Crustal Thickness of Venus: Results from Top, Hot Spot, and Bottom Loading Models

We have calculated admittance spectra using the spatio-spectral method [14] for Venus by moving the central location of the spectrum over a 1 grid, create 360x180 admittance spectra. We invert the observed admittance using top-loading (TL), hot spot (HS), and bottom loading (BL) models, resulting in elastic, crustal, and lithospheric thickness estimates (Te, Zc, and Zl) [0]. The result is a global map for interpreting subsurface structure. Estimated values of Te and Zc concur with previous TL local admittance results, but BL estimates indicate larger values than previously suspected.

Smrekar, S. E.↗
NASA NTRS1975

Application of satellite remote-sensing data to land selection and management

A pilot project conducted to demonstrate the utility and economy of satellite data in preparing thematic maps of a wilderness area emphasizing those resources of greatest interest to the potential owner is described. Vegetation maps delineating potential commercial timber and maps of suggested mineral prospecting areas of seven scattered regions were prepared by interpretation of LANDSAT images, coupled with a limited amount of ground truth. Images acquired both in winter and summer seasons were registered to township maps and used in making interpretations of the areal extent of commercial timber potentials. The amount of snow cover visible through the forest canopies was found to be a useful indicator of timber potentials. Identification was made of characteristic topographic features which are typical of flood plain deposits or of the well developed trellis drainage patterns which can indicate the strike of structural grain of underlying Cretaceous sedimentary rocks. The presence of igneous and mixed igneous and metamorphic rocks were indicated by combinations of spectral differences and anomalous interruptions of local radial drainage patterns.

Stringer, W. J.↗
NASA NTRS1979

Copernicus observations of neutral hydrogen and deuterium in the direction of HR 1099

High-resolution Copernicus U1 scans were obtained of the bright RS CVn binary HR 1099 (d = 33 pc, galactic longitude = 185 deg, galactic latitude = -41 deg) in October 1977. Strong emission at L-alpha was detected. The interstellar L-alpha absorption features of H I and D I were also observed. Analyses of these interstellar lines are reported in this paper. The average density of neutral H in the direction of this system is found to be 0.006-0.012 per cu cm, which, because the local density is higher, requires a marked inhomogeneity along this line of sight. This result, when combined with other recent studies of the local interstellar medium, suggests the sun is located within a moderate-density H I region.

Anderson, R. C.↗
NASA NTRS1985

Inference of equatorial field-line-integrated electron density values using whistlers

The nighttime electron density integrated along a magnetic field line at very small L-values (about 1.06) is inferred by comparing whistler dispersions, measured from a sounding rocket, with model ionospheric calculations. At a local time of 0500 LT, the electron density in the F-layer valley was found to be about 1000 per cu cm. It is suggested that this technique can be applied to earlier times in the local evening to determine ionospheric conditions which benefit the growth of low-latitude plasma instabilities.

Anderson, D. N.↗
NASA NTRS1991

The role of the ionosphere in coupling upstream ULF wave power into the dayside magnetosphere

A series of recent studies of Pc 3 magnetic pulsations in the dayside outer magnetosphere has given new insights into the possible mechanisms of entry of ULF wave power into the magnetosphere from a bow shock-related upstream source. A comparison is made of data from two 10-hour intervals on successive days in April 1986 and then a possible model for transmission of pulsation signals from the magnetosheath into the dayside magnetosphere is presented. Clear interplanetary magnetic field magnitude control of dayside resonant harmonic pulsations and band-limited very high latitude pulsations, as well as pulsation-modulated precipitation of what appear to be magnetosheath/boundary layer electrons are shown. It is believed that this modulated precipitation may be responsible for the propagation of upstream wave power in the Pc 3 frequency band into the high-latitude ionosphere, from whence it may be transported throughout the dayside outer magnetosphere by means of an 'ionospheric transistor'. In this model, modulations in ionospheric conductivity caused by cusp/cleft precipitation cause varying ionospheric currents with frequency spectra determined by the upstream waves; these modulations will be superimposed on the Birkeland currents, which close via these ionospheric currents. Modulated region 2 Birkeland currents will in turn provide a narrow-band source of wave energy to a wide range of dayside local times in the outer magnetosphere.

Engebretson, M. J.↗
NASA NTRS1993

Electron generation of electrostatic waves in the plasma sheet boundary layer

Broadband electrostatic noise (BEN) has been shown to occur in conjunction with ion beams; extensive investigations of possible ion beam-related instabilities that could generate the observed wave spectra have been conducted. It has also been demonstrated that unstable electron distribution functions are sometimes measured in the plasma sheet boundary layer. We present simultaneous observations of ion and electron distribution functions and electric field wave spectra measured by ISEE 1 and ISEE 2 in the Earth's magnetotail. As the spacecraft moved from the tail lobe toward the plasma sheet, the fast indication of boundary layer plasma was seen in the electron distributions, followed some minutes later by the detection of boundary layer ions. The onset of large-amplitude electrostatic waves at frequencies up to the electron plasma frequency was coincident with the onset of the boundary layer electrons, suggesting that broadband electrostatic waves may often be generated by unstable electron distributions in the plasma sheet boundary layer, particularly the higher frequency portion of the wave spectrum. The observed changes in the electron distribution functions indicate that the plasma was not heated locally by the waves.

Onsager, T. G.↗
NASA NTRS2000

Preliminary Admittance Estimates for the Valles Marineris, Mars

We use the gravity and topography fields derived from Mars Global Surveyor in conjunction with a multi-resolution localization admittance technique to constrain lithospheric structure for the trough system of Valles Marineris on Mars.

Anderson, F. Scott↗
NASA NTRS2012

Team LunaCY Outreach Paper

Iowa State University's Lunabotics Club, Team LunaCY, has worked hard to generate enthusiasm for robotics, engineering, and lunar activities. Team LunaCY participated in a variety of different outreach events making a strong impression on Iowa youth. These events led the chair of the mechanical engineering department, Dr. Ted Heindel, to refer to the club's outreach program as "the model that all other engineering clubs should follow." Team LunaCY's outreach activities totaled over 200 hours and captivated over 3000 students and adults throughout the course of this acaden1ic year, reaching out to people all over Iowa and to several special guests. These guests included Vice-President Joe Biden, during a visit to Iowa State University in March 2012, and astronaut Clayton Anderson, during a visit to Iowa State's campus in the fall 2011. Team LunaCY's outreach events created hands on learning opportunities for local youth ranging in age from elementary school children to high school students. The team strove to make a positive impression on Iowa youth and to encourage interest and involvement in scientific fields. The full list of events is shown in Table 1. Three of the major outreach events the team participated in were the FIRST LEGO League, Science Bound, and iExplore STEM Festival.

Heise, James↗
NASA NTRS1981

Observations of the interaction of ozone and dynamics

Data on the global distribution of temperature and ozone obtained with the Limb Radiance Inversion Radiometer which flew on the Nimbus 6 spacecraft are analyzed within the conceptual framework of Hartmann and Garcia (1979). The analysis supports the conclusion that ozone perturbations are dynamically controlled when the photochemical time constant is much greater than the dynamical time constant; when the photochemical constant is much less than the dynamical constant, ozone perturbations are photochemically controlled. It is also shown that the transports of planetary waves, or eddy transports, appear to be strongly localized in the region between the regimes in which dynamical and photochemical controls operate.

Gille, J. C.↗
NASA NTRS1980

Grid evolution in time asymptotic problems

A technique for generating systems of coordinates for solving time asymptotic problems is described which provides a simple way of moving the mesh points in physical space and reduces the error in the solution relative to that obtained using a fixed mesh. First order partial differential equations are formulated for the grid point velocity in transient problems. Local flow information and boundary motion are used to determine the interior grid point motion.

Rai, M. M.↗
NASA NTRS1989

IR emission and UV extinction in two open clusters

Recent models of interstellar extinction have shown the importance of understanding both the UV and IR properties of interstellar dust grains. IRAS data have shown variations in 60 and 100 micron emissions presumably due to the presence of IR cirrus, while recent observations in the UV by Fitzpatrick and Massa have identified components in the UV extinction curve which vary in different star regions. A Draine and Anderson model connects these results by proposing that different size variations in interstellar grains would cause distinct changes in both the IR emission and the UV extinction. In order to test this model it is necessary to make observations in well defined locations away from peculiar extinction regions. In the infrared this means looking away from the galactic plane so as to limit non-local sources of IR radiation. Two open clusters that are out of the galactic plane and which contain a number of late B and early A stars suitable for UV extinction studies, and whose IRAS data show variations in the 60/100 micron ratio were studied. Based on the Drain and Anderson model, variations were expected in their UV extinction curves that correlate with the IR cirrus emission.

Hackwell, James A.↗
NASA NTRS1974

Multidisciplinary applications of ERTS and Skylab data in Ohio

Experimental studies of ERTS-1 and Skylab earth resources data, in combination with correlative aircraft and on-site data, for environmental quality, land use, and resource management applications in Ohio show several areas of operational promise. Prime data use candidates demonstrated to date include definition and enforcement of surface mining (all minerals) legislation; Lake Erie modeling/management; land use classification and mapping studies at state, regional, and localized levels; and resources' inventories particularly of forested areas on both regional (multicounty) and localized scales.

Sweet, D. C.↗
NASA NTRS1977

Explorer 45 wave observations during the large magnetic storm of August 4-5, 1972

The magnetospheric compression associated with the very large magnetic storm of August 4-5, 1972, provided an opportunity for Explorer 45 to observe plasma waves in the magnetosphere and the magnetosheath during extremely disturbed conditions. Electrostatic noise bursts were observed near the plasmapause in electric-field channels from 35 Hz to 5.62 kHz. In the outer magnetosphere, electric-field noise bands apparently harmonically related to the electron gyrofrequency with components as low as 3 kHz and as high as 50 kHz were observed. The electric field of the fundamental was perpendicular to the magnetic-field vector. A mechanism including the electron cyclotron instability may generate the noise band. Hiss of 100-1000 Hz was observed in the outer magnetosphere. The electromagnetic hiss was generally weak and was observed in the magnetic wide-band data only when it was strong. In the magnetosheath broad band, incoherent noise (hiss) was observed from 1 Hz to 100 kHz. This magnetosheath hiss was the strongest phenomenon observed by the plasma-wave detectors during the lifetime of Explorer 45. The highest intensities of magnetosheath hiss occurred at the magnetopause. Its broad-band nature suggests that magnetosheath hiss was generated locally. Broad-band noise bursts and short bursts of chorus were also observed in the magnetosheath.

Taylor, W. W. L.↗