Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “level set”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Simulation of Multistage Turbine Flows

The numerical simulation of turbine flows serves to enhance the understanding of the flow phenomena within multistage turbomachinery components. The direct benefit of this activity is improved modeling capability, which can be used to improve component efficiency and durability. A hierarchy of equations was formulated to assess the difficulty in analyzing the flow field within multistage turbomachinery components. The Navier-Stokes equations provides the most complete description. The simplest description is given by a set of equations that govern the quasi-one-dimensional flow. The number of unknowns to be solved for increases monotonically above the number of equations. The development of the additional set of equations needed to mathematically close the system of equations forms the closure problem associated with that level of description. For the Navier-Stokes equation there is no closure problem. For the quasi-one-dimensional equation set random flow fluctuations, unsteady fluctuations, nonaxisymmetric flow variations, and hub-to-shroud variations on the quasi-one-dimensional flow must be accounted for.

Celestina, M. L.↗
NASA NTRS2020

Lower Level Repair Can Easily Fail Due to High Complexity

The International Space Station (ISS) uses Orbital Replacement Units (ORU’s) to repair failures on orbit. Using ORU’s reduces the crew time required to repair failures, but several copies of each ORU must be stored on ISS to ensure system availability. A typical ORU contains many components and has significant mass, but each ORU can repair only a single component failure. A full set of the ORU internal components could repair many different failures. Lower level assembly or component repair should reduce total spares mass. Successful electronics repair experiments were conducted on ISS. However, implementing component level repair would require a significant effort. The systems must be designed so they can be repaired during a mission, considering component layout and accessibility. The repair procedures must be developed and repair facilities, tools, and diagnostic and test instruments provided. Tracing a fault to a component is much more difficult than isolating it to an ORU. Replacing a component is much more difficult than replacing an ORU. Some problems with lower level repair are discussed. The mass savings of lower level repair will not save as much launch cost as before since launch cost has recently been reduced by an order of magnitude. Most system failures are not component failures that can be fixed by replacing a component but are due to system level problems. Repair and maintenance should be planned as part of an overall maintainability design. The risk that a lower level repair will fail is considerably greater than when using ORUs. With modern high reliability packaged systems, failure diagnosis and repair has become a lost art. However, diagnosis and repair data from the 1960’s show that increasing complexity often causes much longer diagnosis and repair times and may prevent successful repair. Increasing complexity by using lower level repair directly increases system cost, failure rate, crew time for repair, and the risk of an unrepairable system failure.

Harry W Jones↗
NASA NTRS2013

Carbon Dioxide: Surprising Effects on Decision Making and Neurocognitive Performance

The occupants of modern submarines and the International Space Station (ISS) have much in common as far as their air quality is concerned. Air is polluted by materials offgassing, use of utility compounds, leaks of systems chemicals, and anthropogenic sources. The primary anthropogenic compound of concern to submariners and astronauts has been carbon dioxide (CO2). NASA and the US Navy rely on the National Research Council Committee on Toxicology (NRC-COT) to help formulate exposure levels to CO2 that are thought to be safe for exposures of 3-6 months. NASA calls its limits Spacecraft Maximum Allowable Concentrations (SMACs). Years of experience aboard the ISS and a recent publication on deficits in decision making in ground-based subjects exposed briefly to 0.25% CO2 suggest that exposure levels that have been presumed acceptable to preserve health and performance need to be reevaluated. The current CO2 exposure limits for 3-6 months set by NASA and the UK Navy are 0.7%, and the limit for US submariners is 0.5%, although the NRC-COT recommended a 90-day level of 0.8% as safe a few years ago. NASA has set a 1000-day SMAC at 0.5% for exploration-class missions. Anecdotal experience with ISS operations approaching the current 180-day SMAC of 0.7% suggest that this limit is too high. Temporarily, NASA has limited exposures to 0.5% until further peer-reviewed data become available. In the meantime, a study published last year in the journal Environmental Health Perspectives (Satish U, et al. 2012) demonstrated that complexdecision- making performance is somewhat affected at 0.1% CO2 and becomes "dysfunctional" for at least half of the 9 indices of performance at concentrations approaching 0.25% CO2. The investigators used the Strategic Management Simulation (SMS) method of testing for decisionmaking ability, and the results were so surprising to the investigators that they declared that their findings need to be independently confirmed. NASA has responded to the findings on decision making by developing a study to either confirm or refute the published results. In addition, other neurocognitive tests that have been and will be used aboard the ISS will be part of the ground-based study. Further evaluations during the exposures will include ocular and cardiovascular effects of CO2 exposure. In addition, the 1- carbon genetics of the test subjects will be evaluated to determine if any individual subjects are unusually susceptible to CO2 exposure because of genetic factors. Our plan is to extend the published study from Satish by employing a wider series of CO2 exposures to include concentrations of 0.06, 0.12, 0.25, and 0.50%. We believe that our findings will be of keen interest to submariners and to those designing "tight" buildings.

James, John T.↗
NASA NTRS1985

Profiles of temperature and density based on extremes at 5, 10, 20, 30 and 40 km

Information on the vertical distribution of expected extremes of temperature and density are required for the design and operation of systems traversing the atmosphere. Such data are particularly important at altitudes from the surface to approximately 80 km for developing all types of airborne vehicles ranging from helicopters and airplanes to sophisticated aerospace systems. Vertical profiles of temperature and density have been developed based on 1- and 10-percent hot and cold temperatures and 1- and 10- percent high and low densities occurring during the most severe month at the worst locations for which reliable upper-air data are available. The model profiles, from the surface to 80 km, are based on extremes that occur at 5, 10, 20, 30, and 40 km. There are 20 profiles for extreme temperatures (5 levels by 4 percentiles) that include associated densities, and 20 analogous profiles for extreme densities including associated temperatures. Consequently, a set of realistic profiles (rather than envelopes) of temperature and density, associated with extremes at each of 5 specified levels in the troposphere and stratosphere, are now available for altitudes up to 80 km.

Kantor, A. J.↗
NASA NTRS1990

Flight payloads environmental approach

The Earth Observing System (EOS) and Space Station (SS) attached payload instruments to be developed by JPL will have a consistent implied level of reliability confidence based on the application of product assurance requirements. An important subset of these requirements is a set of detailed environmental design and test requirements. These requirements have a sound technical defense, are unambiguous in their level of detail, provide rational risk management as a function of payload classification, and are rigorously enforced with a comprehensive waiver process imposed on planned deviations.

Schlue, John W.↗
NASA NTRS2007

Sensitivity Study for Sensor Optical and Electric Crosstalk Based on Spectral Measurements: An Application to Developmental Sensors Using Heritage Sensors Such As MODIS

The process of developing new sensors for space flight frequently builds upon the designs and experience of existing heritage space flight sensors. Frequently in the development and testing of new sensors, problems are encountered that pose the risk of serious impact on successful retrieval of geophysical products. This paper describes an approach to assess the importance of optical and electronic cross-talk on retrieval of geophysical products using new MODIS-like sensors through the use of MODIS data sets. These approaches may be extended to any sensor characteristic and any sensor where that characteristic may impact the Level 1 products so long as validated geophysical products are being developed from the heritage sensor. In this study, a set of electronic and/or optical cross-talk coefficients are postulated. These coefficients are sender-receiver influence coefficients and represent a sensor signal contamination on any detector on a focal plane when another band's detectors on that focal plane are stimulated with a monochromatic light. The approach involves using the postulated cross-talk coefficients on an actual set of MODIS data granules. The original MODIS data granules and the cross-talk impacted granules are used with validated geophysical algorithms to create the derived products. Comparison of the products produced with the original and cross-talk impacted granules indicates potential problems, if any, with the characteristics of the developmental sensor that are being studied.

Butler, James J.↗
NASA NTRS1983

Data management support for selected climate data sets using the climate data access system

The functional capabilities of the Goddard Space Flight Center (GSFC) Climate Data Access System (CDAS), an interactive data storage and retrieval system, and the archival data sets which this system manages are discussed. The CDAS manages several climate-related data sets, such as the First Global Atmospheric Research Program (GARP) Global Experiment (FGGE) Level 2-b and Level 3-a data tapes. CDAS data management support consists of three basic functions: (1) an inventory capability which allows users to search or update a disk-resident inventory describing the contents of each tape in a data set, (2) a capability to depict graphically the spatial coverage of a tape in a data set, and (3) a data set selection capability which allows users to extract portions of a data set using criteria such as time, location, and data source/parameter and output the data to tape, user terminal, or system printer. This report includes figures that illustrate menu displays and output listings for each CDAS function.

Reph, M. G.↗
NASA NTRS1987

Applications of classical and zero-total-pressure-loss sets of Euler equations to delta wings

Classical and zero-total pressure-loss sets of Euler equations were applied to sharp- and round-edge delta wings. The origin of the total pressure was explained in the classical set. For sharp-edged delta wings, all sets of Euler equations produce the same separated flow solutions. For round-edged delta wings and for coarse grids, the solution depends on the level of dissipation, the accuracy of the surface boundary condition, and the type of Euler equations set. For round-edged delta wings and for fine grids, attached flow solutions are obtained. Also presented were three dimensional flow solutions and asymmetric flow solutions including unsteady flow for sharp-edged delta wings. Euler equations should be restricted to sharp-edged wings for real flow solutions. For roung-edged wings, Navier-Stokes equations must be used.

Kandil, Osama A.↗
NASA NTRS1999

Generation of Level 3 SMMR and SSM/I Brightness Temperatures for the Period 1978-1999

The NOAA/NASA Pathfinder Program was initially designed to assure that certain key remote sensing data sets of particular significance to global change research were scientifically validated, consistently processed and made readily available to the research community at minimal cost. Through this Program the National Snow and Ice Data Center (NSIDC), University of Colorado has successfully processed, archived and distributed the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) Level 3 (EASE-Grid format) Pathfinder data sets for the period 1978 to 1999. These data are routinely distributed to approximately 150 researchers through various media including CD-ROM, 8 mm tape, ftp and the EOS Information Management System (IMS). At NSIDC these data are currently being applied in the development and validation of algorithms to derive snow water equivalent (NASA NAG5-6636), the mapping of frozen ground and the detection of the onset of melt over ice sheets, sea ice and snow cover. The EASE-Grid format, developed at NSIDC in conjunction with the SMMR-SSM/I Pathfinder project has also been applied to Advanced Very High Resolution Radiometer (AVHRR) and TOVS Pathfinder data, as well as ancillary data such as digital elevation, land cover classification and several in situ data sets. EASE-Grid will also be used for all land products derived from the NASA EOS AMSR-E instrument.

Partington, Kim↗
NASA NTRS2000

On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Experimental Study - Part 1

An extensive study to improve flow uniformity and periodicity in the NASA Transonic Flutter Cascade is presented here. The results are reported in two independent parts dealing with the experimental approach and the analytical approach. The first part, the Experimental Study, focuses first on the data sets acquired in this facility in the past and explains several discrepancies, particularly the questions of actual flow incidence and cascade back pressure levels. Next, available means for control and modifications of the cascade flowfield, boundary layer bleed and tailboard settings are presented in detail. This is followed by experimental data sets acquired in modified test facility configurations that were based on analytical predictions of the cascade flowfield. Finally, several important conclusions about improving the cascade flowfield uniformity and blade load periodicity are summarized. The important conclusions are: (1) boundary layer bleed does not improve the cascade flow periodicity; (2) tunnel wall contours must be carefully matched to the expected shape of cascade streamlines; (3) actual flow incidence for each cascade configuration rather must be measured instead of relying on the tunnel geometry; and (4) the current cascade configuration exhibits a very high blade load uniformity over six blades from blade #2 to blade #7, and the facility is now ready for unsteady pressure data acquisition.

Lepicovsky, J.↗
NASA NTRS1977

The use of parametric cost estimating relationships for transport aircraft systems in establishing initial Design to Cost Targets

This paper provides a brief overview of Design to Cost (DTC). Problems inherent in attempting to estimate costs are discussed, along with techniques and types of models that have been developed to estimate aircraft costs. A set of cost estimating relationships that estimate the total production cost of commercial and military transport aircraft at the systems level is presented and the manner in which these equations might be used effectively in developing initial DTC targets is indicated. The principal point made in this paper is that, by using a disagregated set of equations to estimate transport aircraft costs at the systems level, reasonably accurate preliminary cost estimates may be achieved. These estimates may serve directly as initial DTC targets, or adjustments may be made to the estimates obtained for some of the systems to estimate the production cost impact of alternative designs or manufacturing technologies. The relative ease by which estimates may be made with this model, the flexibility it provides by being disaggregated, and the accuracy of the estimates it provides make it a unique and useful tool in establishing initial DTC targets.

Beltramo, M. N.↗
NASA NTRS2016

Three-Dimensional Modeling of Aircraft High-Lift Components with Vehicle Sketch Pad

Vehicle Sketch Pad (OpenVSP) is a parametric geometry modeler that has been used extensively for conceptual design studies of aircraft, including studies using higher-order analysis. OpenVSP can model flap and slat surfaces using simple shearing of the airfoil coordinates, which is an appropriate level of complexity for lower-order aerodynamic analysis methods. For three-dimensional analysis, however, there is not a built-in method for defining the high-lift components in OpenVSP in a realistic manner, or for controlling their complex motions in a parametric manner that is intuitive to the designer. This paper seeks instead to utilize OpenVSP's existing capabilities, and establish a set of best practices for modeling high-lift components at a level of complexity suitable for higher-order analysis methods. Techniques are described for modeling the flap and slat components as separate three-dimensional surfaces, and for controlling their motion using simple parameters defined in the local hinge-axis frame of reference. To demonstrate the methodology, an OpenVSP model for the Energy-Efficient Transport (EET) AR12 wind-tunnel model has been created, taking advantage of OpenVSP's Advanced Parameter Linking capability to translate the motions of the high-lift components from the hinge-axis coordinate system to a set of transformations in OpenVSP's frame of reference.

Olson, Erik D.↗
NASA NTRS1979

Determination of station coordinates from Lageos

Laser tracking of Lageos by the NASA and SAO laser tracking systems from its launch in May 1976 until December 1976 has been used to derive the coordinates of the tracking stations. The NASA tracking data from four systems in the United States had a precision of 10 to 15 cm and the SAO stations in North America, South America and Australia had precisions between 0.8 meters and 1.3 meters. Nearly 90,000 observations of Lageos were used in this analysis. Thirty-one orbital arcs, each five days in length, were derived which had orbital fits of 25 cm for the NASA data and at about 1 meter level for the SAO data. The coordinates of all eight stations were derived from this data set and the preliminary estimate of the overall accuracy of 50 cm in each coordinate. These results are in general agreement at about the 30 cm level with other results obtained from laser tracking of Beacon Explorer C.

Smith, D. E.↗
NASA NTRS1997

Forearm Muscle Oxygenation Decreases During Low Levels of Brief, Isometric Contraction

Regional muscle pain syndromes can be caused by repeated and sustained exertion of a specific muscle. Such exertion may elevate local tissue fluid pressure, reduce blood flow and tissue oxygenation (TO2), and cause fatigue, pain and functional deficits of the Involved muscle. Low levels (less than 20% maximum voluntary contraction (MVC)) of prolonged static contraction of the upper extremity are common In many occupational settings and May cause fatigue. The purpose of our Investigation was to determine whether TO2 decreases significantly at low levels of static contraction of the extensor carpi radialis brevis (ECRB).

Murthy Gita↗
NASA NTRS2000

BOREAS RSS-14 Level-2 GOES-7 Shortwave and Longwave Radiation Images

The BOREAS RSS-14 team collected and processed several GOES-7 and GOES-8 image data sets that covered the BOREAS study region. This data set contains images of shortwave and longwave radiation at the surface and top of the atmosphere derived from collected GOES-7 data. The data cover the time period of 05-Feb-1994 to 20-Sep-1994. The images missing from the temporal series were zero-filled to create a consistent sequence of files. The data are stored in binary image format files. Due to the large size of the images, the level-1a GOES-7 data are not contained on the BOREAS CD-ROM set. An inventory listing file is supplied on the CD-ROM to inform users of what data were collected. The level-1a GOES-7 image data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). See sections 15 and 16 for more information. The data files are available on a CD-ROM (see document number 20010000884).

Hall, Forrest G.↗
NASA NTRS1967

A power-spectral-density computer program

Computer program simplifies and clarifies random noise vibration test results. It also varies PSD test specifications, sets up automatic equalization equipment, and calculates an exact accleration level for the random noise prior to the test.

Chapman, C. P.↗
NASA NTRS1978

A distributed microcomputer telemetry system for spacecraft applications

Distributed microcomputer telemetry system design difficulties are examined and solutions to these difficulties are discussed. In the telemetry system being considered, the data gathering is actually distributed among a number of computers, each with its own commutation cycle, data storage buffers, and specified set of measurements to be sampled. A computer based high level module controls the formation of the final telemetry stream by accessing individual computer's data storage buffers at the appropriate time and inserting them into the telemetry stream. Attention is given to the precise time tagging of data samples, the interconnection of several computers, the autonomous operation of science instruments, and reliability considerations.

Lord, D. D.↗
NASA NTRS1980

The energy dependence of the ratios of secondary to primary elements in the cosmic radiation

The secondary to primary ratios B/C, N/O and (Sc-Mn)/Fe in the galactic cosmic rays have been measured in the overall energy interval 30-180 MeV/n with the University of Chicago cosmic ray telescope on board the satellite IMP-8 during the period 1974-1978. These results, together with the values of the same ratios measured at higher energies, have been compared to the results of cosmic ray propagation calculations using different pathlength distributions (PLD) and different levels of solar modulation, in order to select a single set of parameters consistent with all the measured ratios.

Garcia-Munoz, M.↗