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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Altitude test of several afterburner configurations on a turbofan engine with a hydrogen heater to simulate an elevated turbine discharge temperature

A performance test of several experimental afterburner configurations was conducted with a mixed-flow turbofan engine in an altitude facility. The simulated flight conditions were for Mach 1.4 at two altitudes, 12,190 and 14,630 meters. Turbine discharge temperatures of 889 and 1056 K were used. A production afterburner was tested for comparison. The research afterburners included partial forced mixers with V-gutter flameholders, a carburetted V-gutter flameholder, and a triple ring V-gutter flameholder with four swirl-can fuel mixers. Fuel injection variations were included. Performance data shown include augmented thrust ratio, thrust specific fuel consumption, combustion efficiency, and total pressure drop across the afterburner.

Johnsen, R. L.↗
NASA NTRS1978

Results of the measurement of atmospheric ozone and hydrocarbons in Baden-Wurttemburg

Data are presented on the diurnal variations of the levels of ozone, ethylene, ethane, and acetylene. The measurement procedures used are described. Variations in monthly ozone levels are given, and measurements from different stations are compared. Data on the total monthly concentrations of NO and NO2 are compared with similar data for ozone. Problems in determining interrelationships among the concentrations of the various substances are discussed.

Blander, W.↗
NASA NTRS1978

The X-ray emitting galaxy Centaurus A

OSO-8 X-ray observations of Cen A in 1975 and 1976 are reported. The source spectrum can be well fitted in both years by a power law of number index 1.66 and absorption due to 1.3 by 10 to the 23rd power atoms/sq cm. The total flux varied by a factor of 2 between 1975 and 1976. In 1976 there were flux variations of approximately 40% on a time scale of days. Measurements of the 6.4-keV Fe fluorescent line and the 7.1-keV absorption edge imply Fe/H of approximately 0.000016. Simultaneous radio measurements show variation in phase with X-ray variability. Consideration of radio, millimeter, infrared, and X-ray data shows that all the data can be accounted for by a model in which the X-rays are due to a synchrotron self-Compton source embedded in a cold H2 cloud.

Mushotzky, R. F.↗
NASA NTRS1981

SAR calibration technology review

Synthetic Aperture Radar (SAR) calibration technology including a general description of the primary calibration techniques and some of the factors which affect the performance of calibrated SAR systems are reviewed. The use of reference reflectors for measurement of the total system transfer function along with an on-board calibration signal generator for monitoring the temporal variations of the receiver to processor output is a practical approach for SAR calibration. However, preliminary error analysis and previous experimental measurements indicate that reflectivity measurement accuracies of better than 3 dB will be difficult to achieve. This is not adequate for many applications and, therefore, improved end-to-end SAR calibration techniques are required.

Walker, J. L.↗
NASA NTRS1982

Absorptivity of water vapor for 10.6 micron radiation

Attention is called to recent measurements of the absorptivity of water vapor to 10.6-micron laser radiation made using shock-heated H2O/H2 and H2O/Ar mixtures and a probe CO2 laser. It is noted that these measurements give values about a factor of 2 lower than Ludwig's (1971) low resolution values. It is also argued that Fowler's (1981) high values are not likely to be caused by excited water molecules. It is shown that very intense laser radiation would be required to obtain any appreciable vibrational nonequilibrium. Within the narrow spectral range of 944-948/cm, no significant variation in absorption coefficient (suitably normalized) is observed as a function of laser line, water vapor concentration, total pressure, or diluent gas.

Pugh, E. R.↗
NASA NTRS1982

Analytical and experimental investigation of stator endwall contouring in a small axial-flow turbine. 1: Stator performance

Three stator configurations were studied to determine the effect of stator outer endwall contouring on stator performance. One configuration was a cylindrical stator design. One contoured stator configuration had an S-shaped outer endwall, the other had a conical-convergent outer endwall. The experimental investigation consisted of annular surveys of stator exit total pressure and flow angle for each stator configuration over a range of stator pressure ratio. Radial variations in stator loss and aftermixed flow conditions were obtained when these data were compared with the analytical results to assess the validity of the analysis, good agreement was found.

Haas, J. E.↗
NASA NTRS1982

Periodic and aperiodic ozone variations in the middle and upper stratosphere

Umkehr, ozonesonde and satellite observations are used to determine the height/latitude distribution of the amplitude and phase of the periodic components of the variation in the ozone mixing ratio in the middle and upper stratosphere. The amplitude of the first (annual) harmonic is found to be small in the subtropics and to increase to a maximum at polar latitudes. In addition, it increases with height in the mid and upper stratosphere to an apparent maximum just below the stratosphere. The second (semi-annual) harmonic possesses an amplitude that is largest in tropical regions and in subpolar regions at a level of about 40 km. Very little ozone variation is seen above 30 km with dominant periods close to the quasi-biennial period of total ozone observed in the tropics. The percentage of the total variance of the ozone mixing ratio accounted for by the first harmonic is found to be larger than 60 percent at all heights from 20 deg to 60 deg latitude in both hemispheres (except near 40 km in the Northern Hemisphere).

London, J.↗
NASA NTRS1987

Solar variability and oscillations

Within this decade, observations of total solar irradiance have become good enough to make it possible to study directly the solar luminosity variations on a wide range of time scales, up to several years. At the same time, there has been considerable improvement in understanding the classical indicators of solar activity, such as UV and visible chromospheric lines, soft X-rays, and radio fluxes. The observed variations include the effects of sunspots and plage solar-cycle effects, and signatures of global oscillations and convection. In addition, new characteristic time-scales (154 days and possibly 320 days) have been discovered. This review covers these developments and comments briefly on the subject of helioseismology.

Hudson, Hugh S.↗
NASA NTRS1988

Measurement of the Solar Constant (SOLCON)

Measurement of the Solar Constant (SOLCON) is a solar physics experiment of the Atmospheric Laboratory for Applications and Science (ATLAS 1) NASA mission scheduled for late 1990. The objectives of this investigation are: (1) to measure the absolute value of the solar constant with improved accuracy, and (2) to detect and measure long-term variations that may exist in the absolute value of the solar constant. The solar constant is the total irradiance of the sun at a distance of one astronomical unit. This will be measured directly in space by an absolute self-calibrating radiometer with an absolute accuracy estimated to be of the order of + or - 0.1 percent and a sensitivity better than 0.05 percent. Features of this radiometer are given.

Crommelynck, D.↗
NASA NTRS1989

The sensitivity of synthetic aperture radiometers for remote sensing applications from space

Aperture synthesis offers a means of realizing the full potential of microwave remote sensing from space by helping to overcome the limitations set by antenna size. The result is a potentially lighter, more adaptable structure for applications in space. However, because the physical collecting area is reduced, the signal-to-noise ratio is reduced and may adversely affect the radiometric sensitivity. Sensitivity is an especially critical issue for measurements to be made from low earth orbit because the motion of the platform limits the integration time available for forming an image. The purpose is to develop expression for the sensitivity of remote sensing systems which use aperture synthesis. The objective is to develop basic equations general enough to be used to obtain the sensitivity of the several variations of aperture synthesis which were proposed for sensors in space. The conventional microwave imager (a scanning total power radiometer) is treated as a special case and a comparison of three synthetic aperture configurations with the conventional imager is presented.

Levine, D. M.↗
NASA NTRS1929

Drag of C-Class Airship Hulls of Various Fineness Ratios

This report presents the results of wind-tunnel tests on eight C-class airship hulls with various fineness ratios, conducted in the Navy Aerodynamic Laboratory, Washington. The purpose of the tests was to determine the variation of resistance with fineness ratio, and also to find the pressure and friction elements of the total drag for the model having the least shape coefficient. Seven C-class airship hulls with fineness ratios of 1.0, 1.5, 2.0, 3.0, 6.0, 8.0, and 10.0 were made and verified. These models and also the previously constructed original C-class hull, whose fineness ratio is 4.62, were then tested in the 8 by 8 foot tunnel for drag of 0 degree pitch and yaw, at various wind speeds. The original hull, which was found to have the least shape coefficient, was then tested for pressure distribution over the surface at various wind speeds. (author)

Zahm, A F↗
NASA NTRS1947

Performance Charts for a Turbojet System

Convenient charts are presented for computing the thrust, fuel consumption, and other performance values of a turbojet system. These charts take into account the effects of ram pressure, compressor pressure ratio, ratio of combustion-chamber-outlet temperature to atmospheric temperature, compressor efficiency, turbine efficiency, combustion efficiency, discharge-nozzle coefficient, losses in total pressure in the inlet to the jet-propulsion unit and in the combustion chamber, and variation in specific heats with temperature. The principal performance charts show clearly the effects of the primary variables and correction charts provide the effects of the secondary variables. The performance of illustrative cases of turbojet systems is given. It is shown that maximum thrust per unit mass rate of air flow occurs at a lower compressor pressure ratio than minimum specific fuel consumption. The thrust per unit mass rate of air flow increases as the combustion-chamber discharge temperature increases. For minimum specific fuel consumption, however, an optimum combustion-chamber discharge temperature exists, which in some cases may be less than the limiting temperature imposed by the strength temperature characteristics of present materials.

CHARTS-PERFORMANCE-ENGINES, TURBOJET↗
NASA NTRS1998

GPS, Earthquakes, the Ionosphere, and the Space Shuttle

Sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce infrasonic pressure waves in the atmosphere. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these acoustic waves induce variations of the ionospheric electron density. The Global Positioning System provides a way of directly measuring the Total Electron Content in the ionosphere and, therefore. of detecting such perturbations in the upper atmosphere. In this work, we demonstrate the capabilities of the GPS technique to detect ionospheric perturbations caused by the January 17. 1994, M (sub w) =6.7, Northridge earthquake and the STS-58 Space Shuttle ascent. In both cases, we observe a perturbation of the ionospheric electron density lasting for about 30 m, with periods less than 10 m. The perturbation is complex and shows two sub-events separated by about 15 m. The phase velocities and waveform characteristics of the two sub-events lead us to interpret the first arrival as the direct propagation of 2 free wave, followed by oscillatory guided waves propagating along horizontal atmospheric interfaces at 120 km altitude and below.

Calais, Eric↗
NASA NTRS2004

Combined In-Plane and Through-the-Thickness Analysis for Failure Prediction of Bolted Composite Joints

Although two-dimensional methods provide accurate predictions of contact stresses and bolt load distribution in bolted composite joints with multiple bolts, they fail to capture the effect of thickness on the strength prediction. Typically, the plies close to the interface of laminates are expected to be the most highly loaded, due to bolt deformation, and they are usually the first to fail. This study presents an analysis method to account for the variation of stresses in the thickness direction by augmenting a two-dimensional analysis with a one-dimensional through the thickness analysis. The two-dimensional in-plane solution method based on the combined complex potential and variational formulation satisfies the equilibrium equations exactly, and satisfies the boundary conditions and constraints by minimizing the total potential. Under general loading conditions, this method addresses multiple bolt configurations without requiring symmetry conditions while accounting for the contact phenomenon and the interaction among the bolts explicitly. The through-the-thickness analysis is based on the model utilizing a beam on an elastic foundation. The bolt, represented as a short beam while accounting for bending and shear deformations, rests on springs, where the spring coefficients represent the resistance of the composite laminate to bolt deformation. The combined in-plane and through-the-thickness analysis produces the bolt/hole displacement in the thickness direction, as well as the stress state in each ply. The initial ply failure predicted by applying the average stress criterion is followed by a simple progressive failure. Application of the model is demonstrated by considering single- and double-lap joints of metal plates bolted to composite laminates.

Kradinov, V.↗
NASA NTRS1995

Spatial and Temporal Distribution of Ion Engine Accelerator Grid Erosion

Structural failure of the accelerator grid in two-grid ion optics due to charge exchange ion erosion is considered one of the dominant failure modes for ion engines. A detailed examination of three accelerator grids used in long duration tests of inert gas ion thrusters was undertaken to characterize the radial mass loss distribution, the local distribution of mass loss in the erosion pattern and how it varies as the pattern evolves. The results show significant broadening of the radial profile compared to what is expected in space with significant variations from grid to grid. The local distribution of mass loss and how it varies with increasing total mass loss in the erosion pattern was also found to differ considerably among the three grids. The results indicate that the details of the erosion geometry cannot be ignored when generalizing test results or modeling grid failure to calculate useful engine service life.

Ion Engine↗
NASA NTRS2009

Orion Crew Injury Prediction: Landing Conditions and Vehicle Interface Elements

This presentation reviews the work being done to research the possibility of injuries from landing the Orion Crew Exploration Vehicle in either water or land contingencies This was done using the Total Human Model for Safety (THUMS) finite element model. The purpose of the simulations was to compare variations of a Vehicle Interface Element (VIE) and to evaluate the potential for injury. The presentation is accompanied by several animations from the model runs, showing the projected motion, with and without the various suggested types of VIEs. There are charts showing the injury metrics with the various types of VIEs. The ultimate use of this analysis was to assist in a selection of possible VIE designs

Danelson, Kerry↗
NASA NTRS2016

Uncertainty Analysis of the NASA Glenn 8x6 Supersonic Wind Tunnel

This paper presents methods and results of a detailed measurement uncertainty analysis that was performed for the 8- by 6-foot Supersonic Wind Tunnel located at the NASA Glenn Research Center. The statistical methods and engineering judgments used to estimate elemental uncertainties are described. The Monte Carlo method of propagating uncertainty was selected to determine the uncertainty of calculated variables of interest. A detailed description of the Monte Carlo method as applied for this analysis is provided. Detailed uncertainty results for the uncertainty in average free stream Mach number as well as other variables of interest are provided. All results are presented as random (variation in observed values about a true value), systematic (potential offset between observed and true value), and total (random and systematic combined) uncertainty. The largest sources contributing to uncertainty are determined and potential improvement opportunities for the facility are investigated.

Error↗
NASA NTRS2022

Extreme Poleward Expanding Super Plasma Bubbles Over Asia-Pacific Region Triggered By Tonga Volcano Eruption During the Recovery-Phase of Geomagnetic Storm

The Tonga volcano eruption of 15 January 2022 unleashed a variety of atmospheric perturbations, coinciding with the recovery-phase of a geomagnetic storm. The ensuing thermospheric variations created rare display of extreme poleward-expanding conjugate plasma bubbles seen in the rate of total electron content index over 100–150°E, reaching ∼40°N geographic latitude. This is associated with fluctuations in FORMOSAT-7/COSMIC-2 (F7/C2) ion-density measurements and spread-F in ionograms. Preceding to this, an unusually strong pre-reversal enhancement (PRE) occurred in the global ionospheric specification (GIS) electron density profiles derived from F7/C2 observations. The GIS also revealed a decrease of equatorial ionization anomaly (EIA) crest density due to the storm impact. Reduced E-region conductivity by volcano-induced waves and enhanced F-region wind, further accelerated by reduced ion-drag over the EIA, apparently intensified the PRE. Accompanied with the strong PRE, volcano-induced seed perturbations triggered the super plasma bubble activity.

P. K. Rajesh↗