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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The French method (of representing noise annoyance)

The psophic index used in France for noise exposure from aircraft globally represents the annoyance with the following hypotheses: (1) the global annoyance is a function of the number of aircraft overflights of each type but does not depend on the overflight time; (2) an aircraft flying at night is considered to be just as annoying as 10 aircraft of the same type passing overhead during the day; and (3) and annoyance is only a function of the peak noise levels. Overall, the psophic index appears statistically as good a representation of the average annoyance as methods used in other countries; however, it does seem to reflect poorly the annoyance caused by light aircraft. Noise maps produced for Orly, Roissy, and the area around Paris are described. The range of applications and limitations of the psophic index are discussed.

Collet, F.↗
NASA NTRS1980

Taxonomic classification of world map units in crop producing areas of Argentina and Brazil with representative US soil series and major land resource areas in which they occur

The most probable current U.S. taxonomic classification of the soils estimated to dominate world soil map units (WSM)) in selected crop producing states of Argentina and Brazil are presented. Representative U.S. soil series the units are given. The map units occurring in each state are listed with areal extent and major U.S. land resource areas in which similar soils most probably occur. Soil series sampled in LARS Technical Report 111579 and major land resource areas in which they occur with corresponding similar WSM units at the taxonomic subgroup levels are given.

Huckle, H. F.↗
NASA NTRS1984

Simplified analytical procedures for representing material cyclic response

Requirements for increased durability of gas turbine hot section structural components have made it necessary to place greater emphasis on accurate structural analysis and life prediction. Linear finite-element analysis is generally sufficient for structural analysis applications. However, for structures in the hot part of the engine, nonlinear structural analysis may be required under certain conditions for the accurate prediction of the local stress-strain response. Nonlinear finite element analysis represents a costly effort which is generally incompatible with the iterative nature of the design process. The present investigation is, therefore, concerned with two simplified procedures for estimating the local hysteretic response produced by cyclic thermal loading. These procedures reduce the need for nonlinear finite-element analysis.

Moreno, V.↗
NASA NTRS1983

A sampling procedure to guide the collection of narrow-band, high-resolution spatially and spectrally representative reflectance data

A multistage sampling procedure using image processing, geographical information systems, and analytical photogrammetry is presented which can be used to guide the collection of representative, high-resolution spectra and discrete reflectance targets for future satellite sensors. The procedure is general and can be adapted to characterize areas as small as minor watersheds and as large as multistate regions. Beginning with a user-determined study area, successive reductions in size and spectral variation are performed using image analysis techniques on data from the Multispectral Scanner, orbital and simulated Thematic Mapper, low altitude photography synchronized with the simulator, and associated digital data. An integrated image-based geographical information system supports processing requirements.

Brand, R. R.↗
NASA NTRS1984

Representing Multidimensional Systems Using Visual Displays

Techniques employed to represent multiattribute information in an integrated, object display are reviewed and discussed. A study is proposed to investigate the effects of system parameters such as intervariable correlation on the choice of an optimal display format. The results of a psychophysical scaling study of five different displays are presented.

Casey, E. J.↗
NASA NTRS1986

Are the Viking Lander sites representative of the surface of Mars?

Global remote sensing data of the Martian surface, collected by earth- and satellite-based instruments, are compared with data from the two Viking Landers to determine if the Lander data are representative of the Martian surface. The landing sites are boulder-strewn and feature abundant fine material and evidence of strong eolian forces. One site (VL-1) is in a plains-covered basin which is associated with volcanic activity; the VL-2 site is in the northern plains. Thermal IR, broadband albedo, color imaging and radar remote sensing has been carried out of the global Martian surface. The VL-1 data do not fit a general correlation observed between increases in 70-cm radar cross-sections and thermal inertia. A better fit is found with 12.5-cm cross sections, implying the presence of a thinner or discontinuous duricrust at the VL-1 site, compared to other higher-inertia regions. A thin dust layer is also present at the VL-2 site, based on the Lander reflectance data. The Lander sites are concluded to be among the three observed regions of anomalous reflectivity, which can be expected in low regions selected for the landings. Recommendations are furnished for landing sites of future surface probes in order to choose sites more typical of the global Martian surface.

Jakosky, B. M.↗
NASA NTRS1987

Performance evaluation of fault tolerant systems represented by Markov models

A method to evaluate the performance of fault tolerant systems whose configuration can be represented by time-invariant, discrete-time, discrete-state Markov models is introduced. Each state is assumed to be associated with a constant qualitative measure of the system's performance. The method first computes the moments of the performance probability mass function (PMF) and then finds an approximating function that has the same moments. The form of this function is a maximum entropy solution of the moment matching problem. A simple algorithm for calculating the necessary moments is derived and a method for finding the approximate performance PMF is suggested. After some modification, the method is applied to an example, the Inertial Upper Stage navigation system.

Missana, Jean-Olivier A. A.↗
NASA NTRS1988

System for detecting objects that represent a threat

A description is given of a panoramic receiver. It is used as a sensor containing several detectors that respond to various types of signal and sound. The system described can be used for detecting objects that represent a threat, by using a sensor and a system for discriminating characteristic signals.

Riedl, Guenther↗
NASA NTRS1989

Life science research objectives and representative experiments for the space station

A workshop was convened to develop hypothetical experiments to be used as a baseline for space station designer and equipment specifiers to ensure responsiveness to the users, the life science community. Sixty-five intra- and extramural scientists were asked to describe scientific rationales, science objectives, and give brief representative experiment descriptions compatible with expected space station accommodations, capabilities, and performance envelopes. Experiment descriptions include hypothesis, subject types, approach, equipment requirements, and space station support requirements. The 171 experiments are divided into 14 disciplines.

Johnson, Catherine C.↗
NASA NTRS1990

Gas dynamics, accretion, and evolution of Algols: Initial results for three representative systems

IUE (International Ultraviolet Explorer) observations were made around the orbits of three Algol-type binaries: R Arae, U Cephei and Algol. These stars were selected to represent, respectively, the rapid, moderate and slow phases of mass transfer and mass loss in Algols. The data was obtained to derive maps of gas flow and mass loss, to study accretion processes and kinetic heating, and to investigate the importance of magnetic fields in these systems. Continuous observations were made from GSFC and VILSPA over 4 1/3 consecutive days during 10 to 14 Sep. 1989. A total of 100 spectra are obtained. This is the first time that Algol systems are observed continuously over their orbits with IUE. Initial results from this program are discussed.

Gimenez, A.↗
NASA NTRS1992

Sampling and Representativeness for a Spaceborne Wind Lidar

The capability of an Earth-orbiting lidar to produce a reliable windfield sampling with an error of 1-3 ms(exp -1) and that is relevant to numerical forecasting and climate studies is discussed. The spatial and temporal resolutions range from 100 km to 1000 km and 3 hr to 1 month respectively. In this respect cloud obstruction is of great concern, as it can prevent the lidar probing whole parts of the atmosphere, for both short and long periods of time. A worldwide analysis of cloudiness from either visual observations made from the ground or else from the Stratospheric Aerosol and Gas Experiment (SAGE) instrument, has shown that the average cloud cover is 60 percent. This analysis is only valid at large scales (time and space) compatible with the currently operating satellites. However, a lidar footprint is only about a hundred meters or less, and it was observed from ground based lidars that, even when the cloudiness is 100 percent, some lidar shots get through. A complete analysis of the probability of probing through clouds by a spaceborne lidar is presently beyond our capacities. Hence, no small scale cloudiness data set is yet available representing all kinds of meteorological situations at all latitudes.

Lieutaud, F.↗
NASA NTRS1990

Expendable launch vehicles technology: A report to the US Senate and the US House of Representatives

As directed in Public Law 100-657, Commercial Space Launch Act Amendments of 1988, and consistent with National Space Policy, NASA has prepared a report on a potential program of research on technologies to reduce the initial and recurring costs, increase reliability, and improve performance of expendable launch vehicles for the launch of commercial and government spacecraft into orbit. The report was developed in consultation with industry and in recognition of relevant ongoing and planned NASA and DoD technology programs which will provide much of the required launch systems technology for U.S. Government needs. Additional efforts which could be undertaken to strengthen the technology base are identified. To this end, focus is on needs for launch vehicle technology development and, in selected areas, includes verification to permit private-sector new technology application at reduced risk. If such a program were to be implemented, it would entail both government and private-sector effort and resources. The additional efforts identified would augment the existing launch vehicle technology programs. The additional efforts identified have not been funded, based upon agency assessments of relative priority vis-a-vis the existing programs. Throughout the consultation and review process, the industry representatives stressed the overriding importance of continuing the DoD/NASA Advanced Launch Development activity and other government technology programs as a primary source of essential launch vehicle technology.

Source record↗
NASA NTRS1985

Current issues concerning the representativeness and utility of cloud drift winds in mesoscale meteorology

High-resolution cloud motion wind (CMW) data sets obtained from geostationary satellites for approximately the past decade have been used for the purpose of estimating mesoscale wind fields in various research studies. Yet there remains much controversy surrounding the proper interpretation and use of the resultant wind vector and kinematic fields. This paper is concerned with: (1) how representative are cloud draft winds of actual ambient air motions; and (2) what is the degree of practical usefulness of CMW fields for both mesoscale analysis and as input to numerical weather prediction models.

Koch, Steven E.↗
NASA NTRS1955

Investigations at Supersonic Speeds of 22 Triangular Wings Representing Two Airfoil Sections for Each of 11 Apex Angles

The results of tests of 22 triangular wings, representing two leading-edge shapes for each of 11 apex angles, at Mach numbers 1.62, 1.92, and 1.40 are presented and compared with theory. All wings have a common thickness ratio of 8 percent and a common maximum-thickness point at 18 percent chord. Lift, drag, and pitching moment are given for all wings at each Mach number. The relation of transition in the boundary layer, shocks on the wing surfaces, and characteristics of the pressure distributions is discussed for several wings.

Love, Eugene S↗
NASA NTRS1943

Representative operating charts of propellers tested in the NACA 20-foot propeller-research tunnel

Report presents the results of tests of full-scale propellers made in the 20-foot propeller-research tunnel (PRT) at the Langley Memorial Aeronautical Laboratory. The power coefficients of all dual-rotating propellers in the report represent the sum of the power coefficients of the front and rear propellers and are for the test conditions in which blade angles of the front and rear propellers were set to absorb approximately equal power at peak efficiency only.

Gray, W H↗
NASA NTRS1945

A Systematic Investigation of Pressure Distributions at High Speeds over Five Representative NACA Low-Drag and Conventional Airfoil Sections

Pressure distributions determined from high-speed wind-tunnel tests are presented for five NACA airfoil sections representative of both low-drag and conventional types. Section characteristics of lift, drag, and quarter-chord pitching moment are presented along with the measured pressure distributions for the NACA 65sub2-215 (a=0.5), 66sub2-215 (a=0.6), 0015, 23015, and 4415 airfoils for Mach numbers up to approximately 0.85. A critical study is made of the airfoil pressure distributions in an attempt to formulate a set of general criteria for defining the character of high speed flows over typical airfoil shapes. Comparisons are made of the relative characteristics of the low-drag and conventional airfoils investigated insofar as they would influence the high-speed performance and the high-speed stability and control characteristics of airplanes employing these wing sections.

Graham, Donald J↗
NASA NTRS1958

Incompressible flutter characteristics of representative aircraft wings

This report gives the results of a detailed study of the flutter characteristics of four representative aircraft wings. This study was made using the electric-analog computer at the California Institute of Technology. During the course of this investigation eight important parameters of each wing were varied and, in addition, the effects of mass, inertia, pitching spring, and location of a concentrated mass were investigated for all four wings and at several sweepback angles.

Wilts, C H↗
NASA NTRS1993

Control of nonlinear systems represented in quasilinear form

Methods to synthesize controllers for nonlinear systems are developed by exploiting the fact that under mild differentiability conditions, systems of the form: x-dot = f(x) + G(x)u can be represented in quasilinear form, viz: x-dot = A(x)x + B(x)u. Two classes of control methods are investigated. The first is zero-look-ahead control, where the control input depends only on the current values of A(x) and B(x). For this case the control input is computed by continuously solving a matrix Riccati equation as the system progresses along a trajectory. The second is controllers with look-ahead, where the control input depends on the future behavior of A(x) and B(x). These controllers use the similarity between quasilinear systems and linear time varying systems to find approximate solutions to optimal control type problems. The methods that are developed are not guaranteed to be globally stable. However in simulation studies they were found to be useful alternatives for synthesizing control laws for a general class of nonlinear systems.

Coetsee, Josef A.↗