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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 1,729 records · Page 96
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Lightning Mapping and the Nowcasting of Severe Storms

This paper describes a successful research and operational collaboration between NASA scientists and NWS forecasters to improve severe stor m warnings using real-time data from a regional VHF total lightning mapping array (LMA). Key objectives of our research using LMA data ar e: a) Identification of intensifying and weakening storms using the time rate-of-change of total flash rate; b) Improved severe storm poten tial situational awareness; c) Evaluation of the potential of total f lash rate trend to improve severe storm probability of detection (POD ) and lead time; and d) Validation of mesoscale model forecasts of th understorm initiation. The LMA data are distributed for ingest and di splay in the WFO AWIPS decision support system, and archived at each WFO for case studies, event playbacks, and assessments using the NWS Warning Event Simulator. The Huntsville WFO has upgraded severe thund erstorm warnings to verified tornado warnings and avoided a false ala rm on a severe storm through the added information on storm growth, intensification, and decay that can be deduced from the magnitude and temporal trend of total flash rates. We present detailed case studies of the observed relationships between lightning activity and tornadi c storm development as determined by radar reflectivity and velocity fields, and thunderstorms forecast by the Weather Research and Foreca st (WRF) model. From these collaborative studies, forecasters can eva luate the added value of total lightning data within the forecast and warning decision-making process (http://weather.msfc.nasa.gov/sport) .

Goodman, S.↗
NASA NTRS2000

Flame Design: A Novel Approach Developed to Produce Clean, Efficient Diffusion Flames

Soot formation and flame extinction are vital concerns in the combustion of fossil fuels. In particular, soot is responsible for pollutant emissions, and extinction can cause inefficient or unstable burning. Normal-gravity experiments have demonstrated that flames can be designed to improve both characteristics by redirecting some or all of the nitrogen from the oxidizer into the fuel. Such nitrogen exchange can produce permanently blue flames, which are soot free under all possible flame conditions. Furthermore, this approach can lead to stronger, extinction-resistant flames. Past investigations of nitrogen exchange were unable to identify the physical mechanisms responsible for its benefits because these mechanisms cannot be isolated when normal-gravity flames are studied. In contrast, the Diffusion Flame Extinction and Soot Inception (DESI) experiment considers spherical flames, where nearly perfect spherical symmetry affords new levels of control. Because of buoyancy, spherical flames cannot be created in Earth s gravity. DESI was conceived by principal investigator Professor R.L. Axelbaum of Washington University in St. Louis. Tests to date have utilized the 2.2-Second Drop Tower at the NASA Glenn Research Center at Lewis Field. The experiment is slated for testing aboard the International Space Station in a few years. Two mechanisms have been proposed to explain the connection between nitrogen exchange and permanently blue flames. These are the structure (chemical effects) and hydrodynamics (flow direction and speed). In normal-gravity flames, the structure and hydrodynamics are coupled, since nitrogen exchange simultaneously modifies both. Spherical microgravity flames, on the other hand, allow independent control of these factors. Specifically, structure can be modified via nitrogen exchange, and flow direction can be reversed by swapping the ambient and burner-feed gases. In DESI, these variations can be accomplished without changing the theoretical flame temperature.

Axelbaum, Richard L.↗
NASA NTRS2005

Combined Silicon and Gallium Arsenide Solar Cell UV Testing

The near and long-term effect of UV on silicon solar cells is relatively understood. In an effort to learn more about the effects of UV radiation on the performance of GaAs/Ge solar cells, silicon and gallium arsenide on germanium (GaAs/Ge) solar cells were placed in a vacuum chamber and irradiated with ultraviolet light by a Spectrolab XT 10 solar simulator. Seventeen GaAs/Ge and 8 silicon solar cells were mounted on an 8 inch copper block. By having all the cells on the same test plate we were able to do direct comparison of silicon and GaAs/Ge solar cell degradation. The test article was attached to a cold plate in the vacuum chamber to maintain the cells at 25 degrees Celsius. A silicon solar cell standard was used to measure beam uniformity and any degradation of the ST-10 beam. The solar cell coverings tested included cells with AR-0213 coverglass, fused silica coverglass, BRR-0213 coverglass and cells without coverglass. Of interest in the test is the BRR-0213 coverglass material manufactured by OCLI. It has an added Infrared rejection coating to help reduce the solar cell operating temperature. This coverglass is relatively new and of interest to several current and future programs at Marshall. Due to moves of the laboratory equipment and location only 350 hours of UV degradation have been completed. During this testing a significant leveling off in the rate of degradation was reached. Data from the test and comparisons of the UV effect of the bare cells and cells with coverglass material will be presented.

Willowby, Douglas↗
NASA NTRS2005

High Performance Immobilized Liquid Membrane for Carbon Dioxide Separations

An immobilized liquid membrane has a substrate. A plurality of capsules is disposed on the substrate. Each of the capsules is permeable to a first gas of a mixture of gases comprising the st gas and a second gas. Each of the capsules is substantially impermeable to the second gas. A liquid is disposed in each of the capsules that is permeable to the first gas and substantially impermeable to the second gas.

Parrish, Clyde F.↗
NASA NTRS2006

Dynamic Snap-Through of Thin-Walled Structures by a Reduced Order Method

The goal of this investigation is to further develop nonlinear modal numerical simulation methods for application to geometrically nonlinear response of structures exposed to combined high intensity random pressure fluctuations and thermal loadings. The study is conducted on a flat aluminum beam, which permits a comparison of results obtained by a reduced-order analysis with those obtained from a numerically intensive simulation in physical degrees-of-freedom. A uniformly distributed thermal loading is first applied to investigate the dynamic instability associated with thermal buckling. A uniformly distributed random loading is added to investigate the combined thermal-acoustic response. In the latter case, three types of response characteristics are considered, namely: (i) small amplitude vibration around one of the two stable buckling equilibrium positions, (ii) intermittent snap-through response between the two equilibrium positions, and (iii) persistent snap-through response between the two equilibrium positions. For the reduced order analysis, four categories of modal basis functions are identified including those having symmetric transverse (ST), anti-symmetric transverse (AT), symmetric in-plane (SI), and anti-symmetric in-plane (AI) displacements. The effect of basis selection on the quality of results is investigated for the dynamic thermal buckling and combined thermal-acoustic response. It is found that despite symmetric geometry, loading, and boundary conditions, the AT and SI modes must be included in the basis as they participate in the snap-through behavior.

Przekop, Adam↗
NASA NTRS2005

About an Element of Human Greatness

One of the things Dr. von Braun instinctively knew was that it was as nearly important to explain why we should go into space as to build the machines to take us there. He wrote books and magazine articles, spoke to everyone he could formally and informally, and spent his life to his dying day seeking to educate everyone on the importance of and need for spaceflight. Why should we go? I think there are actually two principle reasons: 1) Because the solar system is filled with cheap, clean energy, and we need to go get it, and, 2) this one may well be even more important, because we need a purpose for ourselves and our country. I think we need an eternal frontier to push up against, our purpose to conquer and settle it. The nice thing about doing that is the solar system is a very rich place, filled with not only mineral wealth but energy, a nearly inexhaustible supply. And if there s one thing this country and this planet desperately needs and is willing to pay for now and forever is energy. The solar system is where it is. We've got to go after it. I believe, then, that Americans have both a self-interest and a patriotic duty to convince ourselves it is time to take another giant step into space. The way to do that is to do what Dr. von Braun did, cut metal and start flying. Success engenders success. Dr. von Braun s grand dream need never die. NASA can spark a twenty-first-century revolution in transportation and energy that could fundamentally change the way we fly through space, power the world, even care for the sick if we do it right. All those things require cheap and clean energy. It exists in the solar system in a variety of forms. Solar energy is the most obvious form, but there are others, including helium-3, which may be the perfect fuel for fusion reactors, and also just happens to cover the Moon. I believe we must go after it. We just need to believe in ourselves and our purpose. I call on all of you here today to join together, get things moving again, and get serious about conquering space. If we do, we'll assure the country s prosperity, and the world s survival, too, for centuries. Along the way, maybe we ll finally understand why my old preacher thought St. Peter s comment about looking for new heavens was so important. According to His promise, it s a big challenge, a huge responsibility, to try to fulfill such a promise and prophecy.

Hickam, Homer↗
NASA NTRS2006

Two Point Space-Time Correlation of Density Fluctuations Measured in High Velocity Free Jets

Two-point space-time correlations of air density fluctuations in unheated, fully-expanded free jets at Mach numbers M(sub j) = 0.95, 1.4, and 1.8 were measured using a Rayleigh scattering based diagnostic technique. The molecular scattered light from two small probe volumes of 1.03 mm length was measured for a completely non-intrusive means of determining the turbulent density fluctuations. The time series of density fluctuations were analyzed to estimate the integral length scale L in a moving frame of reference and the convective Mach number M(sub c) at different narrow Strouhal frequency (St) bands. It was observed that M(sub c) and the normalized moving frame length scale L*St/D, where D is the jet diameter, increased with Strouhal frequency before leveling off at the highest resolved frequency. Significant differences were observed between data obtained from the lip shear layer and the centerline of the jet. The wave number frequency transform of the correlation data demonstrated progressive increase in the radiative part of turbulence fluctuations with increasing jet Mach number.

Panda, Jayanta↗
NASA NTRS1996

Solar Electric Propulsion

The National Aeronautics and Space Administration's New Millennium Program (NMP) is a space flight technology demonstration program that will validate the technologies needed to carry out the Earth and space science missions NASA envisions for the 21(sup st) century. The program is employing an innovative decision-making process to select the specific technologies that will be flight validated. First, NMP has articulated NASA's vision of science exploration for the next century, then it has defined the capabilities needed to execute that vision, and finally it will select and demonstrate the revolutionary technologies that provide those capabilities, thus enabling the science vision.

New Millennium New Millennium Program NMP space fl↗
NASA NTRS2002

JPL micro-thrust propulsion activities

Formation flying and microspacecraft constellation missions pose new propulsion requirements. Formationflying spacecraft, due to the tight positioning and pointing control requirements, may need thrust control within 1- 20 uN to an accuracy of 0.1 uN for LISA and ST-7, for example. Future missions may have extended thrust ranges into the sub - mN range. However, all do require high specific impulses (>500 sec) due to long required thruster firings.

micro-thrust propulsion micropropulsion formation ↗
NASA NTRS1994

Evidence of Seasonally Dependent Stratosphere-Troposphere Exchange and Purging of Lower Stratospheric Aeroso from a Multi-Year Lidar Dataset

Tropospheric and lower stratospheric aerosol backscatter data obtained from a calibrated backscatter lidar at Pasadena, California (34 deg N latitude)over the 1984-1993 period clearly indicate tightly coupled aerosol optical properties in the upper troposphere and lower stratosphere in the winter and early spring, due to the active mid-latitude stratospheric-tropospheric (ST) exchange processes occurring at this time of year.

upper tropospheric aerosols↗
NASA NTRS2006

Performance of the FOS and GHRS Pt/(Cr)-Ne Hollow-cathode Lamps after their Return from Space and Comparison with Archival Data

The Space Telescope European Coordinating Facility (ST-ECF) and National Institute of Standards and Technology (NIST) are collaborating to study hollow cathode calibration lamps as used onboard the Hubble Space Telescope (HST). As part of the STIS Calibration Enhancement (STIS-CE) Project we are trying to improve our understanding of the performance of hollow cathode lamps and the physical processes involved in their long term operation. The original flight lamps from the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) are the only lamps that have ever been returned to Earth after extended operation in space. We have taken spectra of all four lamps using NIST s 10.7-m normal-incidence spectrograph and Fourier transform spectrometer (FTS) optimized for use in the ultraviolet (UV). These spectra, together with spectra archived from six years of on-orbit operations and pre-launch spectra, provide a unique data set - covering a period of about 20 years - for studying aging effects in these lamps. Our findings represent important lessons for the choice and design of calibration sources and their operation in future UV and optical spectrographs in space.

Kerber, Florian↗
NASA NTRS2006

RTF+SpeX Near-IR Images and Spectra of the Moon Pre-impact and at Impact of SMART-1

We present SpeX 0.8-2.5 micron spectra and Br-gamma or J H or K-band images of the Moon on 2006 July 10 UT, 2006 Sep 1 UT, and 2006 Sep 3 UT. The first two dates are data taken in preparation (near Full Moon and 1 st quarter Moon) for observing the impact of ESA's SMART-1 Lunar satellite on 2006 Sep 3 UT. We hope to be presenting images (about 1 arc minute by 1 arc minute), and low resolution (Prism mode) spectra of the SMART-1 impact to be taken with the 60 arc second long slit.

Wooden, Diane H.↗
NASA NTRS2006

Two Serial Data to Pulse Code Modulation System Interfaces

Two pulse code modulation (PCM) system interfaces for asynchronous serial data are described. One interface is for global positioning system (GPS) data on the NASA Dryden Flight Research Center (DFRC) F-15B (McDonnell Douglas Corporation, St. Louis, Missouri) airplane, tail number 836 (F-15B/836). The other is for flight control computer data on the duPont Aerospace (La Jolla, California) DP-1, a 53-percent scale model of the duPont Aerospace DP-2.

Hamory, Phil↗
NASA NTRS2004

REACT Real-Time Emergency Action Coordination Tool

Recently the Emergency Management Operations Center (EMOC) of St. Tammany Parish turned to the Technology Development and Transfer Office (TDTO) of NASA's Stennis Space Center (SSC) for help in combating the problems associated with water inundation. Working through a Dual-Use Development Agreement the Technology Development and Transfer Office, EMOC and a small geospatial applications company named Nvision provided the parish with a new front-line defense. REACT, Real-time Emergency Action coordination Tool is a decision support system that integrates disparate information to enable more efficient decision making by emergency management personnel.

Source record↗
NASA NTRS2007

Mineralogical In-situ Investigation of Acid-Sulfate Samples from the Rio Tinto River, Spain, with a Portable XRD/XRF Instrument

A field campaign was organized in September 2006 by Centro de Astobiologica (Spain) and Washington University (St Louis, USA) for the geological study of the Rio Tinto river bed sediments using a suite of in-situ instruments comprising an ASD reflectance spectrometer, an emission spectrometer, panoramic and close-up color imaging cameras, a life detection system and NASA's CheMin 4 XRD/XRF prototype. The primary objectives of the field campaign were to study the geology of the site and test the potential of the instrument suite in an astrobiological investigation context for future Mars surface robotic missions. The results of the overall campaign will be presented elsewhere. This paper focuses on the results of the XRD/XRF instrument deployment. The specific objectives of the CheMin 4 prototype in Rio Tinto were to 1) characterize the mineralogy of efflorescent salts in their native environments; 2) analyze the mineralogy of salts and oxides from the modern environment to terraces formed earlier as part of the Rio Tinto evaporative system; and 3) map the transition from hematite-dominated terraces to the mixed goethite/salt-bearing terraces where biosignatures are best preserved.

Sarrazin, P.↗
NASA NTRS2006

Aircraft Measurements of Heat Fluxes Over Wind-Driven Coastal Polynyas in the Bering Sea

The first estimates of the average bulk heat transfer coefficient for Arctic sea ice are presented as a function of mean ice thickness. Turbulent heat flux measurements made by the NASA P-3 over the St. Lawrence Island polynya (SLIP) and Kuskokwim Bay in the Bering Sea during AMSR-Ice03 were used to estimate the values of the heat transfer coefficient CH. Estimates of ice thickness were made from the algorithm of Perovich et al. using broadband albedos obtained from Moderate Resolution Imaging Spectroradiometer data. Plots of CH as a function of ice thickness showed a nearly linear relationship for ice thicknesses in the range of 0-14 cm in the polynyas. Previous estimates of CH for different cases over the SLIP were 1.2 x 10(exp -3), but no estimates of ice thickness were available. These results will allow more accurate estimates of heat fluxes from the thin-ice areas of polynyas using satellite retrievals.

Walter, Bernard↗
NASA NTRS2007

[Space Weather Impact on the Electricity Market]

Forbes & St. Cyr (2004, hereafter "FISC") have provided evidence that the electricity market can be impacted by space weather. Our analysis indicated that the estimated market impact for PJM was 3.7 % or approximately $500 million dollars over the 19 month sample period. Kappenman has taken exception to this estimate and contends that we have exaggerated the magnitude of the problem that space weather poses to PJM. There are four specific issues: (1) he claims that we have ignored relevant literature; (2) he asserts that Dst is not an appropriate proxy for GICs in PJM; (3) he charges that our findings are inconsistent with the impact of the 17 September 2000 storm; and (4) he alleges that our discussion of October 2003 storms is misleading. In our article, we have explained our methodology, multivariate regression analysis, with a particular focus on how it compares to correlation analysis. We have also explained the limitations of our analysis. We noted that "...While the Dstlprice relationship was found to be robust, the precise estimate should be treated with a relatively high degree of caution given that econometric modeling is not an exact science as well as the fact that the measure of space weather may be a poor proxy for GICs" (paragraph 96). We have also noted that additional research using local magnetometer data are needed (paragraph 97). We did not claim that that our findings for PJM are representative of the impact of space weather on other power grids. On the contrary, we noted that ... "Only analysis of other power grids will tell. " (paragraph 97). Kappenman inaccurately asserts that we have indicated that our findings . . . "imply much higher total costs are likely across the US and elsewhere in the world." He also inaccurately asserts that we have claimed that " . . . Dst is the most suited proxy for GIC in the PJM grid.. ." Moreover, he inaccurately refers to our analysis as a correlation study that uses Dst as quasi-binary indicator.

SaintCyr, O. Chris↗