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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Exploration of Impinging Water Spray Heat Transfer at System Pressures Near the Triple Point

The heat transfer of a water spray impinging upon a surface in a very low pressure environment is of interest to cooling of space vehicles during launch and re-entry, and to industrial processes where flash evaporation occurs. At very low pressure, the process occurs near the triple point of water, and there exists a transient multiphase transport problem of ice, water and water vapor. At the impingement location, there are three heat transfer mechanisms: evaporation, freezing and sublimation. A preliminary heat transfer model was developed to explore the interaction of these mechanisms at the surface and within the spray.

Heat Transfer↗
NASA NTRS1971

Laboratory evaluation of Fecker and Loral optical IR PWI systems

A previous flight test of two electro-optical pilot warning indicators, using a flashing xenon strobe and silicon detectors as cooperative elements, pointed out several design deficiencies. The present laboratory evaluation program corrected these faults and calibrated the sensitivity of both systems in azimuth elevation and range. The laboratory tests were performed on an optical bench and consisted of three basic components: (1) a xenon strobe lamp whose output is monitored at the indicator detector to give pulse to pulse information on energy content at the receiver; (2) a strobe light attenuating optical system which is calibrated photometrically to provide simulated range; and (3) a positioning table on which the indicator system under study is mounted and which provides spatial location coordinates for all data points. The test results for both systems are tabulated.

Gorstein, M.↗
NASA NTRS1981

Design of a laser system for instantaneous location of a longwall shearer

Calculations and measurements for the design of a laser system for instantaneous location of a longwall shearer were made. The designs determine shearer location to approximately one foot. The roll, pitch, and yaw angles of the shearer track are determined to approximately two degrees. The first technique uses the water target system. A single silicon sensor system and three gallium arsenide laser beams are used in this technique. The second technique is based on an arrangement similar to that employed in aircraft omnidirectional position finding. The angle between two points is determined by combining information in an onmidirectional flash with a scanned, narrow beam beacon. It is concluded that this approach maximizes the signal levels.

Stein, R.↗
NASA NTRS1992

Venus lightning - An update

The evidence for Venus lightning comes from three distinct sources: the Venera 11-14 landers, the Venera 9 orbiter and the Pioneer Venus orbiter. The largest data set and the one being analyzed most thoroughly at present comes the VLF electric field experiment on PVO spacecraft. Recent results show that the Poynting flux out of the atmosphere is consistent with that expected from a terrestrial sized source of lightning or possibly one much greater. Estimates of the flash rate from the statistics of impulsive signals also points to a source that is stronger than the terrestrial source. Ongoing studies of the polarization of the signals and their properties relative to their direction of propagation as well as a recalibration of the Pioneer Venus star sensor promise to provide continuing information on this phenomenon.

Russell, C. T.↗
NASA NTRS1994

Experimental space weathering of regolith material

Significant advances in the understanding of space weathering processes were recently reported. Submicroscopic iron blebs were produced in lunar simulant glass and natural terrestrial minerals by high-temperature reduction in controlled atmosphere furnaces. These experiments altered the samples' optical properties and microtextures so that they resembled those of extremely mature lunar soil. The results contributed to a revised model for natural reduction in the regolith. Subsequently, supporting results were obtained by reduction of lunar samples. Research to date has focused on reduction of three lunar surface components: basalt, pyroclastic glass, and mare soil. An extensive set of H reduction experiments with simulants has led to a detailed understanding of reaction mechanisms and kinetics. Reduction experiments using lunar basalt were recently conducted by Carbotek. Reduced samples from these test were analyzed. Reduction experiments on lunar glass 74220 were run at temperatures of 900-1100 C. Reduction efficiency of volcanic glass proved to be a function of the sample's FeO abundance and reaction temperature. We also reduced mare soil 75061 at temperatures of 900-1050 C. Partial reduction of FeO in olivine and pyroxene occurred, but was slower and less complete than reduction of ilmenite. Our experiments on simulants and lunar samples have indicated that the most readily reduced phases in the regolith are ilmenite and glass. Based on initial tests with simulants we proposed refinements to the accepted model for space weathering of the regolith. The impact of a micrometeoroid flash heats and melts and ejects from the impact point a small volume of soil that contains trapped solar wind H and C. Reduction occurs rapidly, while the melt volume is still in motion. When a droplet encounters unmelted soil, it envelopes cold mineral grains. The melt is chilled rapidly. Our analyses of experimentally reduced lunar basalt, glass, and mare soil support the proposed model for space weathering.

Mckay, D. S.↗
NASA NTRS1972

Lightning criteria relative to space shuttles: Currents and electric field intensity in Florida lightning

The measured electric field intensities of 161 lightning strokes in 39 flashes which occurred between 1 and 35 km from an observation point at Kennedy Space Center, Florida during June and July of 1971 have been analyzed to determine the lightning channel currents which produced the fields. In addition, typical channel currents are derived and from these typical electric fields at distances between 0.5 and 100 km are computed and presented. On the basis of the results recommendations are made for changes in the specification of lightning properties relative to space vehicle design as given in NASA TMX-64589 (Daniels, 1971). The small sample of lightning analyzed yielded several peak currents in the 100 kA range. Several current rise-times from zero to peak of 0.5 microsec or faster were found; and the fastest observed current rate-of-rise was near 200 kA/microsec. The various sources of error are discussed.

Uman, M. A.↗
NASA NTRS2000

Geometrical Effects on the Electromagnetic Radiation from Lightning Return Strokes

The Los Alamos National Laboratory (LANL) Sferic Array has recorded electric-field-change waveforms simultaneously at several stations surrounding the ground-strike points of numerous return strokes in cloud-to-ground lightning flashes. Such data are available from the five-station sub-networks in both Florida and New Mexico. With these data it has been possible for the first time to compare the waveforms radiated in different directions by a given stroke. Such comparisons are of interest to assess both the effects of channel geometry on the fine structure of subsequent-stroke radiation fields and the role of branches in the more jagged appearance of first-stroke waveforms. This paper presents multiple-station, time-domain waveforms with a 200 Hz to 500 kHz pass-band from both first and subsequent return strokes at ranges generally between 100 and 200 km. The differences among waveforms of the same stroke received at stations in different directions from the lightning channel are often obvious. These differences are illustrated and interpreted in the context of channel tortuosity and branches.

Willett, John C.↗
NASA NTRS2003

Mathematical Inversion of Lightning Data: Techniques and Applications

A survey of some interesting mathematical inversion studies dealing with radio, optical, and electrostatic measurements of lightning are presented. A discussion of why NASA is interested in lightning, what specific physical properties of lightning are retrieved, and what mathematical techniques are used to perform the retrievals are discussed. In particular, a relatively new multi-station VHF time-of-arrival (TOA) antenna network is now on-line in Northern Alabama and will be discussed. The network, called the Lightning Mapping Array (LMA), employs GPS timing and detects VHF radiation from discrete segments (effectively point emitters) that comprise the channel of lightning strokes within cloud and ground flashes. The LMA supports on-going ground-validation activities of the low Earth orbiting Lightning Imaging Sensor (LIS) satellite developed at NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama. The LMA also provides detailed studies of the distribution and evolution of thunderstorms and lightning in the Tennessee Valley, and offers interesting comparisons with other meteorological/geophysical datasets. In order to take full advantage of these benefits, it is essential that the LMA channel mapping accuracy (in both space and time) be fully characterized and optimized. A new channel mapping retrieval algorithm is introduced for this purpose. To characterize the spatial distribution of retrieval errors, the algorithm has been applied to analyze literally tens of millions of computer-simulated lightning VHF point sources that have been placed at various ranges, azimuths, and altitudes relative to the LMA network. Statistical results are conveniently summarized in high-resolution, color-coded, error maps.

Koshak, William↗
NASA NTRS1986

The charges that are deposited by cloud-to-ground lightning in Florida

Field changes that were produced by cloud-to-ground flashes from seven storms during 1976, 1977, and 1978 in various sites in Florida are analyzed using the least square optimization method of Jacobson and Krider (1976). The performance of the computer algorithm in determining the field change values is evaluated; the algorithm reproduces total field changes to an accuracy of about 5 percent. Lightning events with field change values of 1 kV/m or greater at three or more sites are studied using a point-charge model. Variations in the altitudes and magnitudes of events which occur from flash to flash, throughout the development of a storm, and from storm to storm are examined and compared.

Maier, Launa M.↗
NASA NTRS2013

Method for Enhancing a Three Dimensional Image from a Plurality of Frames of Flash LIDAR Data

A method for enhancing a three dimensional image from frames of flash LIDAR data includes generating a first distance R(sub i) from a first detector i to a first point on a surface S(sub i). After defining a map with a mesh theta having cells k, a first array S(k), a second array M(k), and a third array D(k) are initialized. The first array corresponds to the surface, the second array corresponds to the elevation map, and the third array D(k) receives an output for the DEM. The surface is projected onto the mesh theta, so that a second distance R(sub k) from a second point on the mesh theta to the detector can be found. From this, a height may be calculated, which permits the generation of a digital elevation map. Also, using sequential frames of flash LIDAR data, vehicle control is possible using an offset between successive frames.

Vanek, Michael D.↗
NASA NTRS2014

Methods of Real Time Image Enhancement of Flash LIDAR Data and Navigating a Vehicle Using Flash LIDAR Data

A method for creating a digital elevation map ("DEM") from frames of flash LIDAR data includes generating a first distance R(sub i) from a first detector i to a first point on a surface S(sub i). After defining a map with a mesh THETA having cells k, a first array S(k), a second array M(k), and a third array D(k) are initialized. The first array corresponds to the surface, the second array corresponds to the elevation map, and the third array D(k) receives an output for the DEM. The surface is projected onto the mesh THETA, so that a second distance R(sub k) from a second point on the mesh THETA to the detector can be found. From this, a height may be calculated, which permits the generation of a digital elevation map. Also, using sequential frames of flash LIDAR data, vehicle control is possible using an offset between successive frames.

Vanek, Michael D.↗
NASA NTRS2006

Single Event Effects Test Results for the Actel ProASIC Plus and Altera Stratix-II Field Programmable Gate Arrays

This work describes radiation testing of Actel's ProASIC Plus and Altera's Stratix-II FPGAs. The Actel Device Under Test (DUT) was a ProASIC Plus APA300-PQ208 nonvolatile, field reprogrammable device which is based on a 0.22micron flash-based LVCMOS technology. Limited investigation has taken place into flash based FPGA technologies, therefore this test served as a preliminary reference point for various SEE behaviors. The Altera DUT was a Stratix-II EP2S60F1020C4. Single Event Upset (SEU) and Single Event Latchup (SEL) were the focus of these studies. For the Actel, a latchup test was done at an effective LET of 75.0 MeV-sq cm/mg at room temperature, and no latchup was detected when irradiated to a total fluence of 1 x 10(exp 7) particles/sq cm. The Altera part was shown to latchup at room temperature.

heavy ions↗
NASA NTRS2012

Evaluation of NASA SPoRT's Pseudo-Geostationary Lightning Mapper Products in the 2011 Spring Program

NASA's Short-term Prediction Research and Transition (SPoRT) program is a contributing partner with the GOES-R Proving Ground (PG) preparing forecasters to understand and utilize the unique products that will be available in the GOES-R era. This presentation emphasizes SPoRT s actions to prepare the end user community for the Geostationary Lightning Mapper (GLM). This preparation is a collaborative effort with SPoRT's National Weather Service partners, the National Severe Storms Laboratory (NSSL), and the Hazardous Weather Testbed s Spring Program. SPoRT continues to use its effective paradigm of matching capabilities to forecast problems through collaborations with our end users and working with the developers at NSSL to create effective evaluations and visualizations. Furthermore, SPoRT continues to develop software plug-ins so that these products will be available to forecasters in their own decision support system, AWIPS and eventually AWIPS II. In 2009, the SPoRT program developed the original pseudo geostationary lightning mapper (PGLM) flash extent product to demonstrate what forecasters may see with GLM. The PGLM replaced the previous GLM product and serves as a stepping-stone until the AWG s official GLM proxy is ready. The PGLM algorithm is simple and can be applied to any ground-based total lightning network. For 2011, the PGLM used observations from four ground-based networks (North Alabama, Kennedy Space Center, Oklahoma, and Washington D.C.). While the PGLM is not a true proxy product, it is intended as a tool to train forecasters about total lightning as well as foster discussions on product visualizations and incorporating GLM-resolution data into forecast operations. The PGLM has been used in 2010 and 2011 and is likely to remain the primary lightning training tool for the GOES-R program for the near future. This presentation will emphasize the feedback received during the 2011 Spring Program. This will discuss several topics. Based on feedback from the 2010 Spring Program, SPoRT created two variant PGLM products, which NSSL produced locally and provided in real-time within AWIPS for 2011. The first is the flash initiation density (FID) product, which creates a gridded display showing the number of flashes that originated in each 8 8 km grid box. The second product is the maximum flash density (MFD). This shows the highest PGLM value for each grid point over a specific period of time, ranging from 30 to 120 minutes. In addition to the evaluation of these two new products, the evaluation of the PGLM itself will be covered. The presentation will conclude with forecaster feedback for additional improvements requested for future evaluations, such as within the 2012 Spring Program.

Stano, Geoffrey T.↗
NASA NTRS1996

Full Mesh Audio Conferencing Using the Point-to-Multipoint On-Board Switching Capability of ACTS

The purpose of this paper is to describe an implementation of audio conferencing using the ACTS T1-VSAT network. In particular, this implementation evaluates the use of the on-board switching capability of the satellite as a viable alternative for providing the multipoint connectivity normally provided by terrestrial audio bridge equipment The system that was implemented provides full mesh, full-duplex audio conferencing, with end-to-end voice paths between all participants requiring only a single hop (i.e. 250 msec. delay). Moreover, it addresses the lack of spontaneity in current systems by allowing a user to easily start a conference from any standard telephone handset connected to an ACTS earth station, and quickly add new members to the conference at any time using the 'hook flash' capability. No prior scheduling of resources is required and there is no central point of control, thereby providing the user with the spontaneity desired in audio conference control.

Rivett, Mary L.↗
NASA NTRS1998

A System Concept for the Advanced Post-TRMM Rainfall Profiling Radars

Atmospheric latent heating field is fundamental to all modes of atmospheric circulation and upper mixed layer circulations of the ocean. The key to understanding the atmospheric heating process is understanding how and where precipitation occurs. The principal atmospheric processes which link precipitation to atmospheric circulation include: (1) convective mass fluxes in the form of updrafts and downdrafts; (2) microphysical. nucleation and growth of hydrometeors; and (3) latent heating through dynamical controls on the gravitation-driven vertical mass flux of precipitation. It is well-known that surface and near-surface rainfall are two of the key forcing functions on a number of geophysical parameters at the surface-air interface. Over ocean, rainfall variation contributes to the redistribution of water salinity, sea surface temperature, fresh water supply, and marine biology and eco-system. Over land, rainfall plays a significant role in rainforest ecology and chemistry, land hydrology and surface runoff. Precipitation has also been closely linked to a number of atmospheric anomalies and natural hazards that occur at various time scales, including hurricanes, cyclones, tropical depressions, flash floods, droughts, and most noticeable of all, the El Ninos. From this point of view, the significance of global atmospheric precipitation has gone far beyond the science arena - it has a far-reaching impact on human's socio-economic well-being and sustenance. These and many other science applications require the knowledge of, in a global basis, the vertical rain structures, including vertical motion, rain intensity, differentiation of the precipitating hydrometeors' phase state, and the classification of mesoscale physical structure of the rain systems. The only direct means to obtain such information is the use of a spaceborne profiling radar. It is important to mention that the Tropical Rainfall Measuring Mission (TRMM) have made a great stride forward towards this ultimate goal. The Precipitation Radar (PR) aboard the TRMM satellite is the first ever spaceborne radar dedicated to three-dimensional, global precipitation measurements over the tropics and the subtropics, as well as the detailed synopsis of a wide range of tropical rain storm systems. In only twelve months since launch, the PR, together with other science instruments abroad the satellite have already provided unprecedented insights into the rainfall systems. It is anticipated the a lot more exciting and important rain observations would be made by TRMM throughout its mission duration. While TRMM has provided invaluable data to the user community, it is only the first step towards advancing our knowledge on rain processes and its contributions to climate variability. It is envisioned that a TRMM follow-on mission is needed in such a way to capitalize on the pioneering information provided by TRMM, and its instrument capability must be extended beyond TRMM in such a way to fully address the key science questions from microphysical to climatic time scale. In fact, a number of new and innovative mission concepts have recently put forth for this purpose. Almost all of these new concepts have suggested the utility of a more advanced, high-resolution, Doppler-enabled, vertical profiling radar that can provide multi-parameter observations of precipitation. In this paper, a system concept for a second- gene ration precipitation radar (PR-2) which addresses the above requirements will be described.

Im, Eastwood↗
NASA NTRS2002

A Lightning Channel Retrieval Algorithm for the North Alabama Lightning Mapping Array (LMA)

A new multi-station VHF time-of-arrival (TOA) antenna network is, at the time of this writing, coming on-line in Northern Alabama. The network, called the Lightning Mapping Array (LMA), employs GPS timing and detects VHF radiation from discrete segments (effectively point emitters) that comprise the channel of lightning strokes within cloud and ground flashes. The network will support on-going ground validation activities of the low Earth orbiting Lightning Imaging Sensor (LIS) satellite developed at NASA Marshall Space Flight Center (MSFC) in Huntsville, Alabama. It will also provide for many interesting and detailed studies of the distribution and evolution of thunderstorms and lightning in the Tennessee Valley, and will offer many interesting comparisons with other meteorological/geophysical wets associated with lightning and thunderstorms. In order to take full advantage of these benefits, it is essential that the LMA channel mapping accuracy (in both space and time) be fully characterized and optimized. In this study, a new revised channel mapping retrieval algorithm is introduced. The algorithm is an extension of earlier work provided in Koshak and Solakiewicz (1996) in the analysis of the NASA Kennedy Space Center (KSC) Lightning Detection and Ranging (LDAR) system. As in the 1996 study, direct algebraic solutions are obtained by inverting a simple linear system of equations, thereby making computer searches through a multi-dimensional parameter domain of a Chi-Squared function unnecessary. However, the new algorithm is developed completely in spherical Earth-centered coordinates (longitude, latitude, altitude), rather than in the (x, y, z) cartesian coordinates employed in the 1996 study. Hence, no mathematical transformations from (x, y, z) into spherical coordinates are required (such transformations involve more numerical error propagation, more computer program coding, and slightly more CPU computing time). The new algorithm also has a more realistic definition of source altitude that accounts for Earth oblateness (this can become important for sources that are hundreds of kilometers away from the network). In addition, the new algorithm is being applied to analyze computer simulated LMA datasets in order to obtain detailed location/time retrieval error maps for sources in and around the LMA network. These maps will provide a more comprehensive analysis of retrieval errors for LMA than the 1996 study did of LDAR retrieval errors. Finally, we note that the new algorithm can be applied to LDAR, and essentially any other multi-station TWA network that depends on direct line-of-site antenna excitation.

Koshak, William↗
NASA NTRS2019

A TID and SEE Characterization of Multi-Terabit COTS 3D NAND Flash

Single-event effects and total ionizing dose testing are described for a 32-layer NAND flash memory, in both SLC and MLC configurations, with special considerations for unique three-dimensional test results. Extraction of three-dimensional heavy-ion test data presents a unique visualization of angular effects in NAND flash. Pattern dependence differences between SLC and MLC mode are noted, along with slightly non-uniform angular cross-section results due to the complex volume. Finally, TID data under different operating and bias conditions shows that the failure point remains the higher-voltage erasure circuitry.

Flash Memory↗