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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Reduction of Cloud Water in Ship Tracks: Observations and Large-Eddy Simulations

Ship tracks represent a natural laboratory to study the effects of aerosols on clouds. A number of observations and simulations have shown that increased droplet concentrations in ship tracks increase their total cross-sectional area, thereby enhancing cloud albedo and providing a negative radiative forcing at the surface and the top of the atmosphere. In some cases, cloud water has been found to be enhanced in ship tracks, which has been attributed to suppression of drizzle and implies an enhanced susceptibility of cloud albedo to droplet concentrations. However, more recently compiled observations indicate that cloud water is instead reduced in daytime ship tracks on average. Such a response is consistent with cloud-burning due to solar absorption by soot (the semi-direct radiative forcing of aerosols), recently suggested to be suppressing trade cumulus cloud coverage over the Indian Ocean. We will summarize observational evidence and present large-eddy simulations that consider these competing mechanisms in the effects of aerosols on cloud albedo.

Ackerman, A. S.↗
NASA NTRS1974

Transportation vehicle energy intensities. A joint DOT/NASA reference paper

A compilation of data on the energy consumption of air and ground vehicles is presented. The ratio BTU/ASM, British Thermal Units/Available Seat Mile, is used to express vehicle energy intensiveness, and related to the energy consumed directly in producing seat-mile or ton-mile productivity. Data is presented on passenger and freight vehicles which are in current use or which are about to enter service, and advanced vehicles which may be operational in the 1980's and beyond. For the advanced vehicles, an estimate is given of the date of initial operational service, and the performance characteristics. Other key considerations in interpreting energy intensiveness for a given mode are discussed, such as: load factors, operations, overhead energy consumption, and energy investments in new structure and equipment.

Mascy, A. C.↗
NASA NTRS2010

Empirical Method to Estimate Hydrogen Embrittlement of Metals as a Function of Hydrogen Gas Pressure at Constant Temperature

High pressure Hydrogen (H) gas has been known to have a deleterious effect on the mechanical properties of certain metals, particularly, the notched tensile strength, fracture toughness and ductility. The ratio of these properties in Hydrogen as compared to Helium or Air is called the Hydrogen Environment Embrittlement (HEE) Index, which is a useful method to classify the severity of H embrittlement and to aid in the material screening and selection for safety usage H gas environment. A comprehensive world-wide database compilation, in the past 50 years, has shown that the HEE index is mostly collected at two conveniently high H pressure points of 5 ksi and 10 ksi near room temperature. Since H embrittlement is directly related to pressure, the lack of HEE index at other pressure points has posed a technical problem for the designers to select appropriate materials at a specific H pressure for various applications in aerospace, alternate and renewable energy sectors for an emerging hydrogen economy. Based on the Power-Law mathematical relationship, an empirical method to accurately predict the HEE index, as a function of H pressure at constant temperature, is presented with a brief review on Sievert's law for gas-metal absorption.

Lee, Jonathan A.↗
NASA NTRS1985

Proceedings of the First National Workshop on the Global Weather Experiment: Current Achievements and Future Directions, volume 2, part 2

An assessment of the status of research using Global Weather Experiment (GWE) data and of the progress in meeting the objectives of the GWE, i.e., better knowledge and understanding of the atmosphere in order to provide more useful weather prediction services. Volume Two consists of a compilation of the papers presented during the workshop. These cover studies that addressed GWE research objectives and utilized GWE information. The titles in Part 2 of this volume include General Circulation Planetary Waves, Interhemispheric, Cross-Equatorial Exchange, Global Aspects of Monsoons, Midlatitude-Tropical Interactions During Monsoons, Stratosphere, Southern Hemisphere, Parameterization, Design of Observations, Oceanography, Future Possibilities, Research Gaps, with an Appendix.

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NASA NTRS1962

Collected Papers on Instability of Shell Structures - 1962

Shell structures are important components of airplanes, missiles, and space vehicles, but present capabilities for predicting the local and general instability of many such structures are inadequate. A large effort continues to be devoted to the stability analysis of shell structures, and considerable progress has been made. Results are slowly disseminated, however, and many engaged in research are not fully cognizant of the problems and practices of the vehicle designers who utilize research results. Therefore, an NASA SYMPOSIUM ON INSTABILITY OF SKELL STRUCTURES was organized by the Langley Research Center with sessions held there on October 24 and 25, 1962. Participants were limited to persons contributing papers and to certain officials of the U.S. Government. This symposium was planned to provide those persons concerned with shell instability at research laboratories, at educational institutions, and in the aerospace industry with a comprehensive view of the present state of the art, including the voids in present knowledge, important current problems, and the most fruitful directions for future theoretical and experimental research on the instability of all types of shell structures. Individuals actively engaged in research on shell stability or design were invited to contribute written papers for inclusion in a compilation to be distributed to the participants prior to the symposium. A few papers were selected by a steering committee for oral presentation at the symposium. Provision was made, also, for a discussion of all papers.

MISSILE↗
NASA NTRS1973

The use of a digital computer for calculation of acoustic fields of complex vibrating structures by the reciprocity principle

A program was compiled for calculating acoustical pressure levels, which might be created by vibrations of complex structures (an assembly of shells and rods), under the influence of a given force, for cases when these fields cannot be measured directly. The acoustical field is determined according to transition frequency and pulse characteristics of the structure in the projection mode. Projection characteristics are equal to the reception characteristics, for vibrating systems in which the reciprocity principle holds true. Characteristics in the receiving mode are calculated on the basis of experimental data on a point pulse space velocity source (input signal) and vibration response of the structure (output signal). The space velocity of a pulse source, set at a point in space r, where it is necessary to calculate the sound field of the structure p(r,t), is determined by measurements of acoustic pressure, created by a point source at a distance R. The vibration response is measured at the point where the forces F and f exciting the system should act.

Rimskiy-Korsakov, A. V.↗
NASA NTRS1983

Modular photovoltaic stand-alone systems: Phase 1

A family of modular stand-alone power systems that covered the range in power level from 1 kw to 14 kw was developed. Products within this family were required to be easily adaptable to different environments and applications, and were to be both reliable and cost effective. Additionally, true commonality in hardware was to be exploited, and unnecessary recurrence of design and development costs were to be minimized; thus improving hardware availability. Assurance of compatibility with large production runs, was also an underlying program goal. A secondary objective was to compile, evaluate, and determine the economic and technical status of available, and potentially available, technology options associated with the balance of systems (BOS) for stand-along photovoltaic (PV) power systems. The secondary objective not only directly supported the primary but additionally contributed to the definition and implementation of the BOS cost reduction plan.

Naff, G. J.↗
NASA NTRS1988

Parafrase restructuring of FORTRAN code for parallel processing

Parafrase transforms a FORTRAN code, subroutine by subroutine, into a parallel code for a vector and/or shared-memory multiprocessor system. Parafrase is not a compiler; it transforms a code and provides information for a vector or concurrent process. Parafrase uses a data dependency to reveal parallelism among instructions. The data dependency test distinguishes between recurrences and statements that can be directly vectorized or parallelized. A number of transformations are required to build a data dependency graph.

Wadhwa, Atul↗
NASA NTRS2007

Navigating the Obstacles in Science Education for School Outreach

This paper gives an overview of the education outreach initiatives that the authors have personally been involved with, their successes and shortcomings are discussed with ways to overcome the difficulties encountered. Recommendations are given on how to navigate the obstacles. Industry professionals, college professors and even church groups participate in education outreach initiatives. For a successful experience, one has to navigate through various phases of the process. The strategy is to convince stakeholders that there is value in doing the outreach activity, form a partnership with the school, circumnavigate the security and administrative procedures, and finally deliver the material to the students. Successful education outreach programs have well-defined objectives, roles and expectations. Success depends on the level of commitment of all parties involved. Taking a look at individual programs, focusing on their shortcomings and best practices, this paper serves as a compilation of useful ideas for effective science and math education outreach. Navigation techniques mentioned in this paper systematically address each obstacle encountered, making solid recommendations for the future. One of the biggest challenges is showing the direct benefits of the outreach activity to stakeholders, so they can see how they profit from sacrificing their workers as outreach mentors.

Rincon, Diana↗
NASA NTRS2013

Systems Analysis of NASA Aviation Safety Program: Final Report

A three-month study (February to April 2010) of the NASA Aviation Safety (AvSafe) program was conducted. This study comprised three components: (1) a statistical analysis of currently available civilian subsonic aircraft data from the National Transportation Safety Board (NTSB), the Federal Aviation Administration (FAA), and the Aviation Safety Information Analysis and Sharing (ASIAS) system to identify any significant or overlooked aviation safety issues; (2) a high-level qualitative identification of future safety risks, with an assessment of the potential impact of the NASA AvSafe research on the National Airspace System (NAS) based on these risks; and (3) a detailed, top-down analysis of the NASA AvSafe program using an established and peer-reviewed systems analysis methodology. The statistical analysis identified the top aviation "tall poles" based on NTSB accident and FAA incident data from 1997 to 2006. A separate examination of medical helicopter accidents in the United States was also conducted. Multiple external sources were used to develop a compilation of ten "tall poles" in future safety issues/risks. The top-down analysis of the AvSafe was conducted by using a modification of the Gibson methodology. Of the 17 challenging safety issues that were identified, 11 were directly addressed by the AvSafe program research portfolio.

Jones, Sharon M.↗
NASA NTRS1962

Compilation of Papers Presented to Meeting on Space Vehicle Landing and Recovery Research and Technology

A meeting on Space Vehicle Landing and Recovery was held on July 10-11, 1962 at NASA Headquarters. The Centers were asked to participate in this meeting in accordance with their interest, activities, and requirements in the subject area. Primary emphasis was directed toward parachutes, parachute-rocket systems, paragliders, and lifting rotor concepts applicable to bothe booster and spacecraft landing and recovery.

Source record↗
NASA NTRS1975

CARETS: A prototype regional environmental information system. Volume 5: Interpretation, compilation and field verification procedures in the CARETS project

The production of the CARETS map data base involved the development of a series of procedures for interpreting, compiling, and verifying data obtained from remote sensor sources. Level II land use mapping from high-altitude aircraft photography at a scale of 1:100,000 required production of a photomosaic mapping base for each of the 48, 50 x 50 km sheets, and the interpretation and coding of land use polygons on drafting film overlays. CARETS researchers also produced a series of 1970 to 1972 land use change overlays, using the 1970 land use maps and 1972 high-altitude aircraft photography. To enhance the value of the land use sheets, researchers compiled series of overlays showing i cultural features, county boundaries and census tracts, surface geology, and drainage basins. In producing Level I land use maps from Landsat imagery, at a scale I of 1:250,000, interpreters overlaid drafting film directly on Landsat color composite transparencies and interpreted on the film. They found that such interpretation involves pattern and spectral signature recognition. In studies using Landsat imagery, interpreters identified numerous areas of change but also identified extensive areas of "false change," where Landsat spectral signatures but not land use had changed.

Field verification procedures↗
NASA NTRS1983

Space station needs, attributes and architectural options study. Volume 3: Requirements

A typical system specification format is presented and requirements are compiled. A Program Specification Tree is shown showing a high inclination space station and a low inclination space station with their typical element breakdown, also represented along the top blocks are the interfaces with other systems. The specification format is directed at the Low Inclination space station.

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NASA NTRS2000

Pilot Comments for High Speed Research Cycle 3 Simulations Study (LaRC.1)

This is a compilation of pilot comments from the Boeing High Speed Research Aircraft, Cycle 3 Simulation Study (LaRC.1) conducted from January to March 1997 at NASA Langley Research Center. This simulation study was conducted using the Visual Motion Simulator. The comments are direct tape transcriptions and have been edited for spelling only.

Bailey, Melvin L.↗
NASA NTRS2001

Efficient Cache use for Stencil Operations on Structured Discretization Grids

We derive tight bounds on the cache misses for evaluation of explicit stencil operators on structured grids. Our lower bound is based on the isoperimetrical property of the discrete octahedron. Our upper bound is based on a good surface to volume ratio of a parallelepiped spanned by a reduced basis of the interference lattice of a grid. Measurements show that our algorithm typically reduces the number of cache misses by a factor of three, relative to a compiler optimized code. We show that stencil calculations on grids whose interference lattice have a short vector feature abnormally high numbers of cache misses. We call such grids unfavorable and suggest to avoid these in computations by appropriate padding. By direct measurements on a MIPS R10000 processor we show a good correlation between abnormally high numbers of cache misses and unfavorable three-dimensional grids.

Frumkin, Michael↗
NASA NTRS2011

Modeling the Quiet Time Outflow Solution in the Polar Cap

We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum, The PWOM solves the gyrotropic transport equations for O(+), H(+), and He(+) along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. [2011] of electron density, which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites (Kitamura et al. [2011]). The data and model agree reasonably well. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide validation of the PWOM's ability to model the quiet time ((background" solution.

Glocer, Alex↗
NASA NTRS2012

Modeling Solar Zenith Angle Effects on the Polar Wind

We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum. The PWOM solves the gyrotropic transport equations for O+, H+, and He+ along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. (2011) of electron density which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites. The data and model agree reasonably well, albeit with some differences. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results of electron density, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide an initial validation of the PWOM s ability to model the quiet time "background" solution.

Glocer, A↗