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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 523 records · Page 29
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NASA NTRS2000

Experimental and Analytical Determinations of Spiral Bevel Gear-Tooth Bending Stress Compared

Spiral bevel gears are currently used in all main-rotor drive systems for rotorcraft produced in the United States. Applications such as these need spiral bevel gears to turn the corner from the horizontal gas turbine engine to the vertical rotor shaft. These gears must typically operate at extremely high rotational speeds and carry high power levels. With these difficult operating conditions, an improved analytical capability is paramount to increasing aircraft safety and reliability. Also, literature on the analysis and testing of spiral bevel gears has been very sparse in comparison to that for parallel axis gears. This is due to the complex geometry of this type of gear and to the specialized test equipment necessary to test these components. To develop an analytical model of spiral bevel gears, researchers use differential geometry methods to model the manufacturing kinematics. A three-dimensional spiral bevel gear modeling method was developed that uses finite elements for the structural analysis. This method was used to analyze the three-dimensional contact pattern between the test pinion and gear used in the Spiral Bevel Gear Test Facility at the NASA Glenn Research Center at Lewis Field. Results of this analysis are illustrated in the preceding figure. The development of the analytical method was a joint endeavor between NASA Glenn, the U.S. Army Research Laboratory, and the University of North Dakota.

Handschuh, Robert F.↗
NASA NTRS2005

Tropospheric Airborne Meteorological Data and Reporting (TAMDAR) Icing Sensor Performance during the 2003/2004 Alliance Icing Research Study (AIRS II)

NASA Langley Research Center and its research partners from the University of North Dakota (UND) and the National Center for Atmospheric Research (NCAR) participated in the AIRS II campaign from November 17 to December 17, 2003. AIRS II provided the opportunity to compare TAMDAR in situ in-flight icing condition assessments with in situ data from the UND Citation II aircraft's Rosemont system. TAMDAR is designed to provide a general warning of ice accretion and to report it directly into the Meteorological Data Communications and Reporting System (MDCRS). In addition to evaluating TAMDAR with microphysical data obtained by the Citation II, this study also compares these data to the NWS operational in-flight icing Current Icing Potential (CIP) graphic product and with the NASA Advanced Satellite Aviation-weather Products (ASAP) Icing Severity product. The CIP and ASAP graphics are also examined in this study to provide a context for the Citation II's sorties in AIRS II.

Murray, John J.↗
NASA NTRS2005

Quickbird Geometry Report for Summer 2003

Digital Globe provides for general use 2.4 m multi-spectral and 0.7 m panchromatic imagery acquired by the Quickbird satellite. This geometrically corrected imagery was obtained as standard and orthorectified products; the difference between the two products is primarily in the degree of geometric accuracy that Digital Globe claims. For both products, every image pixel contains estimated sets of Northing/Easting and lat/long coordinates accessible through an image display application such as ENVI. Ground processing was performed by Digital Globe using the ADP 2.1 version of their system. Analysis conducted at South Dakota State University attempted to verify the geometric accuracy of standard and orthorectified Quickbird imagery to determine if specifications for the NASA Science Data Purchase (SDP) were met. These specifications are in Table 1 of Appendix 1. In this analysis, we had approximately 90 Ground Control Points (varies depending on scene size on each date), uniformly distributed over the Brookings, SD, area, from 4 Quickbird scenes acquired August 23, September 15, and October 21 of 2003.

Darbha, Ravikanth↗
NASA NTRS2006

NASA/SDSU Geopositional Characterization

The geolocational accuracy of products from the IKONOS, QuickBird, and OrbView-3 sensors was evaluated using two test sites: one developed in and around Brookings, SD, and one near Stennis Space Center, MS. Both of these relatively flat sites host over 100 ground control points surveyed to an accuracy of approximately 5 cm. They provide robust locations to test the basic geolocational accuracy of a variety of spaceborne and aircraft sensor systems. Imagery of both test sites was acquired by these three sensors in 2004 and in 2005; several products from each sensor, ranging from basic datasets through orthorectified imagery, were analyzed at Stennis Space Center and at South Dakota State University. While direct comparisons between sensors and products are difficult because of differing processing schemes, results indicate that these products tend to display stated levels of accuracy.

Helder, Dennis↗
NASA NTRS2006

Radiometric Characterization Results for the IKONOS, Quickbird, and OrbView-3 Sensor

Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities better understand commercial imaging satellite properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other systems. To address this calibration need, the NASA Applied Sciences Directorate (ASD) at Stennis Space Center established a commercial satellite imaging radiometric calibration team consisting of three independent groups: NASA ASD, the University of Arizona Remote Sensing Group, and South Dakota State University. Each group independently determined the absolute radiometric calibration coefficients of available high-spatial-resolution commercial 4-band multispectral products, in the visible though near-infrared spectrum, from GeoEye(tradeMark) (formerly SpaceImaging(Registered TradeMark)) IKONOS, DigitalGlobe(Regitered TradeMark) QuickBird, and GeoEye (formerly ORBIMAGE(Registered TradeMark) OrbView. Each team member employed some variant of reflectance-based vicarious calibration approach, requiring ground-based measurements coincident with image acquisitions and radiative transfer calculations. Several study sites throughout the United States that covered a significant portion of the sensor's dynamic range were employed. Satellite at-sensor radiance values were compared to those estimated by each independent team member to evaluate the sensor's radiometric accuracy. The combined results of this evaluation provide the user community with an independent assessment of these sensors' absolute calibration values.

Holekamp, Kara↗
NASA NTRS2007

Radiometric Calibration of the AWiFS Using Vicarious Calibration Techniques

A radiometric calibration assessment of the AWiFS (Advanced Wide Field Sensor) on the Indian Remote Sensing Resourcesat-1 satellite was performed by the NASA Applied Research & Technology Project Office (formerly the Applied Sciences Directorate) at the John C. Stennis Space Center. A reflectance-based vicarious calibration approach, requiring ground-based measurements coincident with satellite acquisitions and radiative transfer calculations, was used to estimate at-sensor radiance. The AWiFS is a 4-band, multispectral, moderate-resolution (60 m) imaging sensor that operates in the visible through short-wave infrared spectrum and is currently being considered as a Landsat-like alternative. Several study sites near the Stennis Space Center that attempted to span the dynamic range of the sensor were employed. Satellite at-sensor radiance values were compared to those estimated to determine the sensor's radiometric accuracy. The results of this evaluation provide the user community with an independent assessment of the radiometric accuracy of AWiFS image products, which are commercially available through GeoEye. These results are an extension of an independent assessment made by the University of Arizona Remote Sensing Group, the South Dakota State University Satellite Calibration Group & Image Processing Lab, and the NASA Applied Sciences Directorate at the John C. Stennis Space Center the previous year.

Pagnutti, Mary↗
NASA NTRS2005

Evolution of a Florida Cirrus Anvil

This paper presents a detailed study of a single thunderstorm anvil cirrus cloud measured on 21 July 2002 near southern Florida during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers--Florida Area Cirrus Experiment (CRYSTAL-FACE). NASA WB-57F and University of North Dakota Citation aircraft tracked the microphysical and radiative development of the anvil for 3 h. Measurements showed that the cloud mass that was advected downwind from the thunderstorm was separated vertically into two layers: a cirrus anvil with cloud-top temperatures of -45?C lay below a second, thin tropopause cirrus (TTC) layer with the same horizontal dimensions as the anvil and temperatures near -70?C. In both cloud layers, ice crystals smaller than 50 ?m across dominated the size distributions and cloud radiative properties. In the anvil, ice crystals larger than 50 ?m aggregated and precipitated while small ice crystals increasingly dominated the size distributions; as a consequence, measured ice water contents and ice crystal effective radii decreased with time. Meanwhile, the anvil thinned vertically and maintained a stratification similar to its environment. Because effective radii were small, radiative heating and cooling were concentrated in layers approximately 100 m thick at the anvil top and base. A simple analysis suggests that the anvil cirrus spread laterally because mixing in these radiatively driven layers created horizontal pressure gradients between the cloud and its stratified environment. The TTC layer also spread but, unlike the anvil, did not dissipate--perhaps because the anvil shielded the TTC from terrestrial infrared heating. Calculations of top-of-troposphere radiative forcing above the anvil and TTC showed strong cooling that tapered as the anvil evolved.

Garrett, T. J.↗
NASA NTRS2007

Radiometric Characterization of the IKONOS, QuickBird, and OrbView-3 Sensors

The NASA team of University of Arizona, South Dakota State University, and NASA SSC produce consistent results. The OrbView calibration coefficients do not appear to agree well with the NASA team estimate (approx. 20% difference). Discussions with GeoEye (TradeMark) (formerly ORBIMAGE(Registered TradeMark)) personnel are ongoing to update the calibration coefficients. The NASA team will continue to assess OrbView radiometric accuracy.

Holekamp, Kara↗
NASA NTRS2007

AWiFS Radiometric Assessment

An assessment of the Advanced Wide Field Sensor (AWiFS) is presented. The contents include: 1) Overview of AWiFS sensor; 2) Description of University of Arizona approach; 3) Description of South Dakota State approach and results; 4) Description of Stennis Space Center approach and results; 5) Summary of results for all groups.

Thome, Kurt↗
NASA NTRS2006

QuickBird and OrbView-3 Geopositional Accuracy Assessment

Objective: Compare vendor-provided image coordinates with known references visible in the imagery. Approach: Use multiple, well-characterized sites with >40 ground control points (GCPs); sites that are a) Well distributed; b) Accurately surveyed; and c) Easily found in imagery. Perform independent assessments with independent teams. Each team has slightly different measurement techniques and data processing methods. NASA Stennis Space Center. South Dakota State University.

Helder, Dennis↗
NASA NTRS2010

Preliminary Testing of a Pressurized Space Suit and Candidate Fabrics Under Simulated Mars Dust Storm and Dust Devil Conditions

In August 2009 YAP Films (Toronto) received permission from all entities involved to create a documentary film illustrating what it might be like to be on the surface of Mars in a space suit during a dust storm or in a dust devil. The science consultants on this project utilized this opportunity to collect data which could be helpful to assess the durability of current space suit construction to the Martian environment. The NDX?1 prototype planetary space suit developed at the University of North Dakota was used in this study. The suit features a hard upper torso garment, and a soft lower torso and boots assembly. On top of that, a nylon-cotton outer layer is used to protect the suit from dust. Unmanned tests were carried out in the Martian Surface Wind Tunnel (MARSWIT) at the NASA Ames Research Center, with the suit pressurized to 10 kPa gauge. These tests blasted the space suit upper torso and helmet, and a collection of nine candidate outer layer fabrics, with wind-borne simulant for five different 10 minute tests under both terrestrial and Martian surface pressures. The infiltration of the dust through the outer fabric of the space suit was photographically documented. The nine fabric samples were analyzed under light and electron microscopes for abrasion damage. Manned tests were carried out at Showbiz Studios (Van Nuys, CA) with the pressure maintained at 20?2 kPa gauge. A large fan-created vortex lifted Martian dust simulant (Fullers Earth or JSC Mars?1) off of the floor, and one of the authors (Lee) wearing the NDX?1 space suit walked through it to judge both subjectively and objectively how the suit performed under these conditions. Both the procedures to scale the tests to Martian conditions and the results of the infiltration and abrasion studies will be discussed.

Gaier, James R.↗
NASA NTRS2010

Preliminary Testing of a Pressurized Space Suit and Candidate Fabrics Under Simulated Mars Dust Storm and Dust Devil Conditions

In August 2009 YAP Films (Toronto) received permission from all entities involved to create a documentary film illustrating what it might be like to be on the surface of Mars in a space suit during a dust storm or in a dust devil. The science consultants on this project utilized this opportunity to collect data which could be helpful to assess the durability of current space suit construction to the Martian environment. The NDX-1 prototype planetary space suit developed at the University of North Dakota was used in this study. The suit features a hard upper torso garment, and a soft lower torso and boots assembly. On top of that, a nylon-cotton outer layer is used to protect the suit from dust. Unmanned tests were carried out in the Martian Surface Wind Tunnel (MARSWIT) at the NASA Ames Research Center, with the suit pressurized to 10 kPa gauge. These tests blasted the space suit upper torso and helmet, and a collection of nine candidate outer layer fabrics, with wind-borne simulant for five different 10 min tests under both terrestrial and Martian surface pressures. The infiltration of the dust through the outer fabric of the space suit was photographically documented. The nine fabric samples were analyzed under light and electron microscopes for abrasion damage. Manned tests were carried out at Showbiz Studios (Van Nuys, California) with the pressure maintained at 20 2 kPa gauge. A large fan-created vortex lifted Martian dust simulant (Fullers Earth or JSC Mars-1) off of the floor, and one of the authors (Lee) wearing the NDX-1 space suit walked through it to judge both subjectively and objectively how the suit performed under these conditions. Both the procedures to scale the tests to Martian conditions and the results of the infiltration and abrasion studies will be discussed.

Gaier, James R.↗
NASA NTRS2010

Combining Hydrological Modeling and Remote Sensing Observations to Enable Data-Driven Decision Making for Devils Lake Flood Mitigation in a Changing Climate

This slide presentation reviews work to combine the hydrological models and remote sensing observations to monitor Devils Lake in North Dakota, to assist in flood damage mitigation. This reports on the use of a distributed rainfall-runoff model, HEC-HMS, to simulate the hydro-dynamics of the lake watershed, and used NASA's remote sensing data, including the TRMM Multi-Satellite Precipitation Analysis (TMPA) and AIRS surface air temperature, to drive the model.

Zhang, Xiaodong↗
NASA NTRS2011

Physical Validation of GPM Retrieval Algorithms Over Land: An Overview of the Mid-Latitude Continental Convective Clouds Experiment (MC3E)

The joint NASA Global Precipitation Measurement (GPM) -- DOE Atmospheric Radiation Measurement (ARM) Midlatitude Continental Convective Clouds Experiment (MC3E) was conducted from April 22-June 6, 2011, centered on the DOE-ARM Southern Great Plains Central Facility site in northern Oklahoma. GPM field campaign objectives focused on the collection of airborne and ground-based measurements of warm-season continental precipitation processes to support refinement of GPM retrieval algorithm physics over land, and to improve the fidelity of coupled cloud resolving and land-surface satellite simulator models. DOE ARM objectives were synergistically focused on relating observations of cloud microphysics and the surrounding environment to feedbacks on convective system dynamics, an effort driven by the need to better represent those interactions in numerical modeling frameworks. More specific topics addressed by MC3E include ice processes and ice characteristics as coupled to precipitation at the surface and radiometer signals measured in space, the correlation properties of rainfall and drop size distributions and impacts on dual-frequency radar retrieval algorithms, the transition of cloud water to rain water (e.g., autoconversion processes) and the vertical distribution of cloud water in precipitating clouds, and vertical draft structure statistics in cumulus convection. The MC3E observational strategy relied on NASA ER-2 high-altitude airborne multi-frequency radar (HIWRAP Ka-Ku band) and radiometer (AMPR, CoSMIR; 10-183 GHz) sampling (a GPM "proxy") over an atmospheric column being simultaneously profiled in situ by the University of North Dakota Citation microphysics aircraft, an array of ground-based multi-frequency scanning polarimetric radars (DOE Ka-W, X and C-band; NASA D3R Ka-Ku and NPOL S-bands) and wind-profilers (S/UHF bands), supported by a dense network of over 20 disdrometers and rain gauges, all nested in the coverage of a six-station mesoscale rawinsonde network. As an exploratory effort to examine land-surface emissivity impacts on retrieval algorithms, and to demonstrate airborne soil moisture retrieval capabilities, the University of Tennessee Space Institute Piper aircraft carrying the MAPIR L-band radiometer was also flown during the latter half of the experiment in coordination with the ER-2. The observational strategy provided a means to sample the atmospheric column in a redundant framework that enables inter-calibration and constraint of measured and retrieved precipitation characteristics such as particle size distributions, or water contents- all within the umbrella of "proxy" satellite measurements (i.e., the ER-2). Complimenting the precipitation sampling framework, frequent and coincident launches of atmospheric soundings (e.g., 4-8/day) then provided a much larger mesoscale view of the thermodynamic and winds environment, a data set useful for initializing cloud models. The datasets collected represent a variety cloud and precipitation types including isolated cumulus clouds, severe thunderstorms, mesoscale convective systems, and widespread regions of light to moderate stratiform precipitation. We will present the MC3E experiment design, an overview of operations, and a summary of preliminary results.

Petersen, Walter A.↗
NASA NTRS2012

The Next Landsat Satellite: The Landsat Data Continuity Mission

The Landsat program is one of the longest running satellite programs for Earth observations from space. The program was initiated by the launch of Landsat 1 in 1972. Since then a series of six more Landsat satellites were launched and at least one of those satellites has been in operations at all times to continuously collect images of the global land surface. The Department of Interior (DOI) U.S. Geological Survey (USGS) preserves data collected by all of the Landsat satellites at their Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota. This 40-year data archive provides an unmatched record of the Earth's land surface that has undergone dramatic changes in recent decades due to the increasing pressure of a growing population and advancing technologies. EROS provides the ability for anyone to search the archive and order digital Landsat images over the internet for free. The Landsat data are a public resource for observing, characterizing, monitoring, trending, and predicting land use change over time providing an invaluable tool for those addressing the profound consequences of those changes to society. The most recent launch of a Landsat satellite occurred in 1999 when Landsat 7 was placed in orbit. While Landsat 7 remains in operation, the National Aeronautics and Space Administration (NASA) and the DOI/ USGS are building its successor satellite system currently called the Landsat Data Continuity Mission (LDCM). NASA has the lead for building and launching the satellite that will carry two Earth-viewing instruments, the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). The OLI will take images that measure the amount of sunlight reflected by the land surface at nine wavelengths of light with three of those wavelengths beyond the range of human vision. T1RS will collect coincident images that measure light emitted by the land surface as a function of surface temperature at two longer wavelengths well beyond the range of human vision. The DOI/USGS is developing the ground system that will command and control the LDCM satellite in orbit and manage the OLI and TIRS data transmitted by the satellite. DOI/USGS will thus operate the satellite and collect, archive, and distribute the image data as part of the EROS archive. DOI/USGS has committed to renaming LDCM as Landsat 8 following launch. By either name the satellite and its sensors will extend the 40-year archive with images sufficiently consistent with data from earlier Landsat satellites to allow multi-decadal, broad-area studies of our dynamic landscapes. The next Landsat satellite and ground system are on schedule for a January, 2013 launch.

Rons, James R.↗
NASA NTRS2013

Geometric Effects on the Amplification of First Mode Instability Waves

The effects of geometric changes on the amplification of first mode instability waves in an external supersonic boundary layer were investigated using numerical techniques. Boundary layer stability was analyzed at Mach 6 conditions similar to freestream conditions obtained in quiet ground test facilities so that results obtained in this study may be applied to future test article design to measure first mode instability waves. The DAKOTA optimization software package was used to optimize an axisymmetric geometry to maximize the amplification of the waves at first mode frequencies as computed by the 2D STABL hypersonic boundary layer stability analysis tool. First, geometric parameters such as nose radius, cone half angle, vehicle length, and surface curvature were examined separately to determine the individual effects on the first mode amplification. Finally, all geometric parameters were allowed to vary to produce a shape optimized to maximize the amplification of first mode instability waves while minimizing the amplification of second mode instability waves. Since first mode waves are known to be most unstable in the form of oblique wave, the geometries were optimized using a broad range of wave frequencies as well as a wide range of oblique wave angles to determine the geometry that most amplifies the first mode waves. Since first mode waves are seen most often in flows with low Mach numbers at the edge of the boundary layer, the edge Mach number for each geometry was recorded to determine any relationship between edge Mach number and the stability of first mode waves. Results indicate that an axisymmetric cone with a sharp nose and a slight flare at the aft end under the Mach 6 freestream conditions used here will lower the Mach number at the edge of the boundary layer to less than 4, and the corresponding stability analysis showed maximum first mode N factors of 3.

Kirk, Lindsay C.↗
NASA NTRS2013

ISSM: Ice Sheet System Model

In order to have the capability to use satellite data from its own missions to inform future sea-level rise projections, JPL needed a full-fledged ice-sheet/iceshelf flow model, capable of modeling the mass balance of Antarctica and Greenland into the near future. ISSM was developed with such a goal in mind, as a massively parallelized, multi-purpose finite-element framework dedicated to ice-sheet modeling. ISSM features unstructured meshes (Tria in 2D, and Penta in 3D) along with corresponding finite elements for both types of meshes. Each finite element can carry out diagnostic, prognostic, transient, thermal 3D, surface, and bed slope simulations. Anisotropic meshing enables adaptation of meshes to a certain metric, and the 2D Shelfy-Stream, 3D Blatter/Pattyn, and 3D Full-Stokes formulations capture the bulk of the ice-flow physics. These elements can be coupled together, based on the Arlequin method, so that on a large scale model such as Antarctica, each type of finite element is used in the most efficient manner. For each finite element referenced above, ISSM implements an adjoint. This adjoint can be used to carry out model inversions of unknown model parameters, typically ice rheology and basal drag at the ice/bedrock interface, using a metric such as the observed InSAR surface velocity. This data assimilation capability is crucial to allow spinning up of ice flow models using available satellite data. ISSM relies on the PETSc library for its vectors, matrices, and solvers. This allows ISSM to run efficiently on any parallel platform, whether shared or distrib- ISSM: Ice Sheet System Model NASA's Jet Propulsion Laboratory, Pasadena, California uted. It can run on the largest clusters, and is fully scalable. This allows ISSM to tackle models the size of continents. ISSM is embedded into MATLAB and Python, both open scientific platforms. This improves its outreach within the science community. It is entirely written in C/C++, which gives it flexibility in its design, and the power/speed that C/C++ allows. ISSM is svn (subversion) hosted, on a JPL repository, to facilitate its development and maintenance. ISSM can also model propagation of rifts using contact mechanics and mesh splitting, and can interface to the Dakota software. To carry out sensitivity analysis, mesh partitioning algorithms are available, based on the Scotch, Chaco, and Metis partitioners that ensure equal area mesh partitions can be done, which are then usable for sampling and local reliability methods.

Larour, Eric↗