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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 595 records · Page 33
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NASA NTRS2000

Significant Findings: Seasonal Distributions of Global Ocean Chlorophyll and Nutrients With a Coupled Ocean General Circulation, Biogeochemical, and Radiative Model: Comparisons With Satellite and In Situ Data - 2

A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model were determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (>1000 km) model chlorophyll seasonal distributions were statistically positively correlated with CZCS chlorophyll in 10 of 12 major oceanographic regions, and with SeaWiFS in all 12. Notable disparities in magnitudes occurred, however, in the tropical Pacific, the spring/summer bloom in the Antarctic, autumn in the northern high latitudes, and during the southwest monsoon in the North Indian Ocean. Synoptic scale (100-1000 km) comparisons of satellite and in situ data exhibited broad agreement, although occasional departures were apparent. Model nitrate distributions agreed with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicated that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on basin and synoptic scales.

Gregg, Watson W.↗
NASA NTRS1999

The Future of Electronic Device Design: Device and Process Simulation Find Intelligence on the World Wide Web

We are on the path to meet the major challenges ahead for TCAD (technology computer aided design). The emerging computational grid will ultimately solve the challenge of limited computational power. The Modular TCAD Framework will solve the TCAD software challenge once TCAD software developers realize that there is no other way to meet industry's needs. The modular TCAD framework (MTF) also provides the ideal platform for solving the TCAD model challenge by rapid implementation of models in a partial differential solver.

Biegel, Bryan A.↗
NASA NTRS2000

X-33 LH2 Tank Failure Investigation Findings

This presentation focuses on the tank history, test objectives, failure description, investigation and conclusions. The test objectives include verify structural integrity at 105% expected flight load limit varying the following parameters: cryogenic temperature; internal pressure; and mechanical loading. The Failure description includes structural component of the aft body, quad-lobe design, and sandwich - honeycomb graphite epoxy construction.

Niedermeyer, Mindy↗
NASA NTRS2001

X-33 LH2 Tank Failure Investigation Findings

The X-33 liquid hydrogen tank failure investigation found the following: (1) The inner skin microcracked and hydrogen infiltrated into it; (2) The cracks grew larger under pressure; (3) When pressure was removed, the cracks closed slightly; (4) When the tank was drained and warmed, the cracks closed and blocked the leak path; (5) Foreign object debris (FOD) and debond areas provided an opportunity for a leak path; and (6) There is still hydrogen in the other three lobes today.

Niedermeyer, M.↗
NASA NTRS2001

Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances. More tests are needed of the consistency among different methods and of the effects of changing humidity on aerosol.

Russell, Philip B.↗
NASA NTRS1994

FRESIP: A Discovery Mission Concept To Find Earth-Sized Planets Around Solar Like Stars

The current nebular theory postulates that planets are. a consequence of the formation of stars from viscous accretion disks. Condensation from the accretion disk favors the formation of small rocky planets in the hot inner region, and the formation of gas giants in the cool outer region. Consequently, terrestrial-type planet in inner orbits should be commonplace. From geometrical considerations , Borucki and Summers have shown that 1% of planetary systems resembling our solar system should show transits for Earth-sized (or larger) planets. Thus a photometric satellite that uses a wide field of view telescope and a large detector array to simultaneously monitor 5000 target stars should detect 50 planetary systems. To differentiate regularly recurring transits from statistical fluctuations of the stellar flux, one must observe over several orbital periods so that the false positive rate can be reduced to one event or less. A one-meter aperture telescope placed in a halo orbit about either the L1 or L2 Lagrange points and viewing perpendicular to both the orbital and ecliptic planes can view continuously for the required period because neither the Sun, Earth, or Moon would enter the field of view. Model calculations show that the observations should provide statistically significant estimates of the distributions of planetary size, orbital radius, coplanarity, and the frequency of planetary systems that have Earth-sized planets in inner orbits. Because approximately one half of the star systems observed will be binary systems, the frequency of planetary systems orbiting either one or both of the stars can also be determined.

Borucki, William↗
NASA NTRS2001

Multi-Sensor Characterization of the Boreal Forest: Initial Findings

Results are presented in an initial apriori knowledge approach toward using complementary multi-sensor multi-temporal imagery in characterizing vegetated landscapes over a site in the Boreal Ecosystem-Atmosphere Study (BOREAS). Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Airborne Synthetic Aperture Radar (AIRSAR) data were segmented using multiple endmember spectral mixture analysis and binary decision tree approaches. Individual date/sensor land cover maps had overall accuracies between 55.0% - 69.8%. The best eight land cover layers from all dates and sensors correctly characterized 79.3% of the cover types. An overlay approach was used to create a final land cover map. An overall accuracy of 71.3% was achieved in this multi-sensor approach, a 1.5% improvement over our most accurate single scene technique, but 8% less than the original input. Black spruce was evaluated to be particularly undermapped in the final map possibly because it was also contained within jack pine and muskeg land coverages.

Reith, Ernest↗
NASA NTRS2001

Findings from the X-33 Hydrogen Tank Failure Investigation

The X-33 Hydrogen tank failed during test in November of 1999 at MSFC. The tank completed the structural loading phase of the test successfully and was drained of hydrogen prior to the failure. The failure initiated in the acreage of Lobe 1 and was instantaneous, peeling the outer skin and core away from the inner skin. It was determined there were several factors that provided the opportunity for the tank to fail in this way. The factor giving life to these opportunistic circumstances was hydrogen infiltration into the core of the tank. The mechanism for this phenomenon will be discussed in this presentation.

Niedermeyer, Melinda↗
NASA NTRS2002

Biomimetics for NASA Langley Research Center: Year 2000 Report of Findings From a Six-Month Survey

This report represents an attempt to see if some of the techniques biological systems use to maximize their efficiency can be applied to the problems NASA faces in aeronautics and space exploration. It includes an internal survey of resources available at NASA Langley Research Center for biomimetics research efforts, an external survey of state of the art in biomimetics covering the Materials, Structures, Aerodynamics, Guidance and Controls areas. The Biomimetics Planning team also included ideas for potential research areas, as well as recommendations on how to implement this new program. This six-month survey was conducted in the second half of 1999.

Siochi, Emilie J.↗
NASA NTRS1996

Finding New Math Identities by Computer

Recently a number of interesting new mathematical identities have been discovered by means of numerical searches on high performance computers, using some newly discovered algorithms. These include the following: pi = ((sup oo)(sub k=0))(Sigma) (1 / 16) (sup k) ((4 / 8k+1) - (2 / 8k+4) - (1 / 8k+5) - (1 / 8k+6)) and ((17 pi(exp 4)) / 360) = ((sup oo)(sub k=1))(Sigma) (1 + (1/2) + (1/3) + ... + (1/k))(exp 2) k(exp -2), zeta(3, 1, 3, 1, ..., 3, 1) = (2 pi(exp 4m) / (4m+2)! where m = number of (3,1) pairs. and where zeta(n1,n2,...,nr) = (sub k1 (is greater than) k2 (is greater than) ... (is greater than) kr)(Sigma) (1 / (k1 (sup n1) k2 (sup n2) ... kr (sup nr). The first identity is remarkable in that it permits one to compute the n-th binary or hexadecimal digit of pu directly, without computing any of the previous digits, and without using multiple precision arithmetic. Recently the ten billionth hexadecimal digit of pi was computed using this formula. The third identity has connections to quantum field theory. (The first and second of these been formally established; the third is affirmed by numerical evidence only.) The background and results of this work will be described, including an overview of the algorithms and computer techniques used in these studies.

Bailey, David H.↗
NASA NTRS2000

Finding Diamonds in the Rough

HighTower Software, Inc. has developed a commercial software application originally designed at JPL that helps users identify deviations from norms out of massive quantities of data. The commercial product is known as CyberGrid and the same software is still supporting NASA's Voyager, Galileo and Cassini missions. CyberGrid generates 3-D graphs of data and has been used in AIDS research as well as e-commerce applications.

Source record↗
NASA NTRS2002

Finding Feasible Abstract Counter-Examples

A strength of model checking is its ability to automate the detection of subtle system errors and produce traces that exhibit those errors. Given the high computational cost of model checking most researchers advocate the use of aggressive property-preserving abstractions. Unfortunately, the more aggressively a system is abstracted the more infeasible behavior it will have. Thus, while abstraction enables efficient model checking it also threatens the usefulness of model checking as a defect detection tool, since it may be difficult to determine whether a counter-example is feasible and hence worth developer time to analyze. We have explored several strategies for addressing this problem by extending an explicit-state model checker, Java PathFinder (JPF), to search for and analyze counter-examples in the presence of abstractions. We demonstrate that these techniques effectively preserve the defect detection ability of model checking in the presence of aggressive abstraction by applying them to check properties of several abstracted multi-threaded Java programs. These new capabilities are not specific to JPF and can be easily adapted to other model checking frameworks; we describe how this was done for the Bandera toolset.

Pasareanu, Corina S.↗
NASA NTRS1993

Finding the Lost City

Nicholas Clapp, a filmmaker and archeology enthusiast, had accumulated extensive information concerning Ubar, the fabled lost city of ancient Arabia. When he was unable to identify its exact location, however, he turned to the Jet Propulsion Laboratory (JPL) for assistance in applying orbital remote sensing techniques. JPL scientists searched NASA's shuttle imaging radar, as well as Landsat and SPOT images and discovered ancient caravan tracks. This enabled them to prepare a map of the trails, which converged at a place known as Ash Shisr. An expedition was formed, which found structures and artifacts from a city that predates previous area civilization by a thousand years. Although it will take time to validate the city as Ubar, the discovery is a monumental archeological triumph.

Source record↗
NASA NTRS2003

Kepler Mission: A Mission to Find Earth-size Planets in the Habitable Zone

The Kepler Mission is a Discovery-class mission designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. It is a wide field of view photometer Schmidt-type telescope with an array of 42 CCDs. It has a 0.95 m aperture and 1.4 m primary and is designed to attain a photometric precision of 2 parts in 10(exp 5) for 12th magnitude solar-like stars for a 6 hr transit duration. It will continuously observe 100,000 main-sequence stars from 9th to 14th magnitude in the Cygnus constellation for a period of four years with a cadence of 4/hour. An additional 250 stars can be monitored at a cadence of l/minute to do astro-seismology of stars brighter than 11.5 mv. The photometer is scheduled to be launched into heliocentric orbit in 2007. When combined with ground-based spectrometric observations of these stars, the positions of the planets relative to the habitable zone can be found. The spectra of the stars are also used to determine the relationships between the characteristics of terrestrial planets and the characteristics of the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. Based on the results of the current Doppler-velocity discoveries, over a thousand giant planets will also be found. Information on the albedos and densities of those giants showing transits will be obtained. At the end of the four year mission, hundreds of Earth-size planets should be discovered in and near the HZ of their stars if such planets are common. A null result would imply that terrestrial planets in the HZ are very rare and that life might also be quite rare.

Borucki, W. J.↗
NASA NTRS2003

Finding the Cold Needle in a Warm Haystack: Infrared Imaging Applied to Locating Cryo-cooled Crystals in Loops

Thermally imaging the cryocooling processes of crystals has been demonstrated showing the progression of a cold wave through a crystal from the face closest to the origin of the coldstream ending at the point furthest away. During these studies large volume crystals were clearly distinguished from the loop holding them. Large volume crystals, used for neutron studies, were chosen deliberately to enhance the imaging. The different infrared transmission and reflectance properties of the crystal in comparison to the cryo-protectant are thought to be the parameter that produces the contrast making the crystal visible. As an application of the technology to locating crystals, more small crystals of lysozyme and a bFGF/dna complex were cryo-protected and imaged in large loops. The crystals were clearly distinguished from the vitrified solution. In the case of the bFGF/dna complex the illumination had to be carefully manipulated to enable the crystal to be seen in the visible spectrum. These preliminary results will be presented along with advantages and disadvantages of the technique and a discussion of how it might be applied.

Snell, Edward↗
NASA NTRS2003

X-33 LH2 Tank Failure Investigation Findings

This viewgraph presentation provides information on the composite sandwich-honeycomb structure of the liquid hydrogen tank of the X-33 reusable launch vehicle, and describes why the the first pressure test to determine the tank's structural integrity failed. The presentation includes images of the tank before and after the failed test, including photomicrographs. It then reaches conclusions on the nature of the microcracks which caused the liquid hydrogen leakage.

Niedermeyer, Melinda↗
NASA NTRS2003

Rethinking Human-Centered Computing: Finding the Customer and Negotiated Interactions at the Airport

The breakdown in the air transportation system over the past several years raises an interesting question for researchers: How can we help improve the reliability of airline operations? In offering some answers to this question, we make a statement about Huuman-Centered Computing (HCC). First we offer the definition that HCC is a multi-disciplinary research and design methodology focused on supporting humans as they use technology by including cognitive and social systems, computational tools and the physical environment in the analysis of organizational systems. We suggest that a key element in understanding organizational systems is that there are external cognitive and social systems (customers) as well as internal cognitive and social systems (employees) and that they interact dynamically to impact the organization and its work. The design of human-centered intelligent systems must take this outside-inside dynamic into account. In the past, the design of intelligent systems has focused on supporting the work and improvisation requirements of employees but has often assumed that customer requirements are implicitly satisfied by employee requirements. Taking a customer-centric perspective provides a different lens for understanding this outside-inside dynamic, the work of the organization and the requirements of both customers and employees In this article we will: 1) Demonstrate how the use of ethnographic methods revealed the important outside-inside dynamic in an airline, specifically the consequential relationship between external customer requirements and perspectives and internal organizational processes and perspectives as they came together in a changing environment; 2) Describe how taking a customer centric perspective identifies places where the impact of the outside-inside dynamic is most critical and requires technology that can be adaptive; 3) Define and discuss the place of negotiated interactions in airline operations, identifying how these interactions between customers and airline employees provided new insights into design problems in the airline system; 4) Show how taking a customer-centric perspective influences the HCC design of an airline system and make recommendations for new architectures and intelligent devices that will enable airline systems to adapt flexibly to delay situations, supporting both customers and airline employees.

Wales, Roxana↗
NASA NTRS2003

Laminar Soot Processes (LSP) Experiment: Findings From Space Flight Measurements

The present experimental study of soot processes in hydrocarbon-fueled laminar nonbuoyant and nonpremixed (diffusion) flames at microgravity within a spacecraft was motivated by the relevance of soot to the performance of power and propulsion systems, to the hazards of unwanted fires, and to the emission of combustion-generated pollutants. Soot processes in turbulent flames are of greatest practical interest, however, direct study of turbulent flames is not tractable because the unsteadiness and distortion of turbulent flames limit available residence times and spatial resolution within regions where soot processes are important. Thus, laminar diffusion flames are generally used to provide more tractable model flame systems to study processes relevant to turbulent diffusion flames, justified by the known similarities of gas-phase processes in laminar and turbulent diffusion flames, based on the widely-accepted laminar flamelet concept of turbulent flames. Unfortunately, laminar diffusion flames at normal gravity are affected by buoyancy due to their relatively small flow velocities and, as discussed next, they do not have the same utility for simulating the soot processes as they do for simulating the gas phase processes of turbulent flames.

Sunderland, P. B.↗