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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Measurements of energy exchange between acoustic fields and non-uniform steady flow fields

Data were obtained for a resonance tube having a vent at the center in the lateral boundary, an average flow being introduced at the ends. Experiments were done for both circular and slot vents, over ranges of both frequency and Mach number. It was demonstrated that a subsonic exhaust vent in the lateral boundary of a cold flow resonance tube provides a gain of acoustic energy for the fundamental mode within the resonance tube. The gain of acoustic energy increases approximately linearly with the Mach number, as predicted by the one-dimensional analysis. The one-dimensional result gives the values for the slope representing the variation of the attenuation coefficient of the exhaust vent with respect to the average Mach number of the flow within roughly 30% of those measured. It has been verified that the subsonic vent produces a gain proportional to the average Mach number, proportional to the frequency, and independent of the shape. The results may be applicable to the study of vibration phenomena in solid propellant rocket engines.

Magiawala, K. R.↗
NASA NTRS1987

Cratering history of Miranda

The surface of the southern hemisphere of Miranda imaged by Voyager 2 is divisible into two general types of terrain: cratered terrain, characterized by numerous craters and undulating intercrater plains; and basins, circular to rectangular areas of complex morphology having large-scale albedo markings. To determine the relative ages of the terrains and the length of geological activity, crater-frequency data were compiled for various parts of the cratered terrain and basins. Crater-frequency data indicate that the cratered terrain is the oldest terrain on Miranda and that it was locally resurfaced.

Plescia, J. B.↗
NASA NTRS1989

An analytic development of orbit determination for a distant, planetary orbiter

With the advent of the Mariner '71 Mission, NASA has been sending spacecraft to orbit various distant bodies within the solar system. At present, there is still no adequate theory describing the inherent state estimation accuracy, based on two-way, coherent range-rate data. It is the purpose of this article to lay the groundwork for a general elliptic theory, and in addition to provide an analytic solution for the special case of circular orbits. It is shown that circular orbits about distant planets may suffer singularities in over-all position error estimation. These singularities are due to orbit inclination, placement of the line-of-nodes, and insignificant cross-velocity at the start and end of retrograde motion when orbiting a superior planet. Even though these conclusions appear to yield poor state estimation, one should not be unduly alarmed inasmuch as the stated conditions for singularity are not maintained for extended periods during typical mission scenarios. However, mission analysts should be aware of these potential pitfalls and realize that spuriously large results for circular orbiters can be obtained and are not the result of incorrect assumptions or faulty software. The general elliptic problem appears so involved that analytic inversion at this time is just not feasible, and in any case the resulting expression for the position error would likely be so lengthy that any understanding would be lost in the maze.

Russell, R. K.↗
NASA NTRS1990

Comparison of water production rates from UV spectroscopy and visual magnitudes for some recent comets

IUE data on the UV and visible coma emissions of the comets Bradfield, P/Tempel 2, Wilson, and P/Halley, are presently compared with the visual lightcurves from magnitudes reported in the IAU circulars to consider the temporal evolution of these comets. While the water-production rates obtainable from visual magnitudes on the basis of Newburn's (1984) method are consistent with OH-derived rates to first order, they are sometimes either displaced or unable to exhibit the same pre/postperihelion asymmetry. The best agreement is obtained for the relatively dust-free Comet P/Tempel 2. IUE Fine Error Sensor lightcurves are generally in agreement with curves based on total visual magnitude.

Roettger, E. E.↗
NASA NTRS1993

A high resolution gravity model for Venus - GVM-1

A spherical harmonic model of the gravitational field of Venus complete to degree and order 50 has been developed using the S-band Doppler tracking data of the Pioneer Venus Orbiter (PVO) collected between 1979 and 1982. The short wavelengths of this model could only be resolved near the PVO periapse location (about 14 deg N latitude), therefore a priori constraints were applied to the model to bias poorly observed coefficients towards zero. The resulting model has a half-wavelength resolution of 400 km near the PVO periapse location, but the resolution degrades to greater than 1000 km near the poles. This gravity model correlates well with a degree 50 spherical harmonic expansion of the Venus topography derived from a combination of Magellan and PVO data. New tracking data from Magellan's gravity mission should provide some improvement to this model, although a complete model of the Venusian gravity field will depend on tracking of Magellan after the circularization of its orbit using aerobraking.

Nerem, R. S.↗
NASA NTRS1993

P/Halley - Effects of time-dependent production rates on spatial emission profiles

Spatial profiles of C2, CN, NH2, and O(D-1) in Comet P/Halley taken on 1986 March 1.54 and 2.55 and April 14.32 and 15.30 clearly show the effect of the 7 day periodic variation seen in photometric observations. With a time-dependent model based upon the light curve and employing standard scale lengths for each species reduced to the appropriate heliocentric distance, we are able to reproduce the highly variable profiles for all species. We computed the phase lag and amplitude correction between the actual gas production at the nucleus and the temporal/spatial filter imposed by the finite aperture photometry. For early March we find a phase lag and amplitude correction of 12 hr and -9 percent, respectively, whereas in mid-April the values are 6 hr and -27 percent. The same phase lag and amplitude correction work equally well for all four species despite their wide variation in photochemical lifetimes for production and decay. The same model integrated over circular apertures is able to reproduce the entire published March and April photometric light curves for C2. Our results require the use of the 7.60 day period for the March data as opposed to the 7.37 day period that is relevant for the April data, in agreement with the published analysis of the photometric data. Our results will help to reconcile the placement of active areas on the surface of Halley's comet with various remote observations and spacecraft images of the nucleus.

Combi, Michael R.↗
NASA NTRS1993

Flow and Heat Transfer in 180-Degree Turn Square Ducts: Effects of Turning Configuration and System Rotation

Forced flow through channels connected by sharp bends is frequently encountered in various rocket and gas turbine engines. For example, the transfer ducts, the coolant channels surround the combustion chamber, the internal cooling passage in a blade or vane, the flow path in the fuel element of a nuclear rocket engine, the flow around a pressure relieve valve piston, and the recirculated base flow of multiple engine clustered nozzles. Transport phenomena involved in such a flow passage are complex and considered to be very different from those of conventional turning flow with relatively mild radii of curvature. While previous research pertaining to this subject has been focused primarily on the experimental heat transfer, very little analytical work is directed to understanding the flowfield and energy transport in the passage. Therefore, the primary goal of this paper is to benchmark the predicted wall heat fluxes using a state-of-the-art computational fluid dynamics (CFD) formulation against those of measurement for a rectangular turn duct. Other secondary goals include studying the effects of turning configurations, e.g., the semi-circular turn, and the rounded-corner turn, and the effect of system rotation. The computed heat fluxes for the rectangular turn duct compared favorably with those of the experimental data. The results show that the flow pattern, pressure drop, and heat transfer characteristics are different among the three turning configurations, and are substantially different with system rotation. Also demonstrated in this work is that the present computational approach is quite effective and efficient and will be suitable for flow and thermal modeling in rocket and turbine engine applications.

Wang, Ten-See↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 18

Topics discussed include: PoDS: A Powder Delivery System for Mars In-Situ Organic, Mineralogic and Isotopic Analysis Instruments Planetary Differentiation of Accreting Planetesimals with 26Al and 60Fe as the Heat Sources Ground-based Observation of Lunar Surface by Lunar VIS/NIR Spectral Imager Mt. Oikeyama Structure: First Impact Structure in Japan? Central Mounds in Martian Impact Craters: Assessment as Possible Perennial Permafrost Mounds (Pingos) A Further Analysis of Potential Photosynthetic Life on Mars New Insight into Valleys-Ocean Boundary on Mars Using 128 Pixels per Degree MOLA Data: Implication for Martian Ocean and Global Climate Change; Recursive Topography Based Surface Age Computations for Mars: New Insight into Surficial Processes That Influenced Craters Distribution as a Step Toward the Formal Proof of Martian Ocean Recession, Timing and Probability; Laser-induced Breakdown Spectroscopy: A New Method for Stand-Off Quantitative Analysis of Samples on Mars; Milk Spring Channels Provide Further Evidence of Oceanic, >1.7-km-Deep Late Devonian Alamo Crater, Southern Nevada; Exploration of Martian Polar Residual Caps from HEND/ODYSSEY Data; Outflow Channels Influencing Martian Climate: Global Circulation Model Simulations with Emplaced Water; Presence of Nonmethane Hydrocarbons on Pluto; Difference in Degree of Space Weathering on the Newborn Asteroid Karin; Circular Collapsed Features Related to the Chaotic Terrain Formation on Mars; A Search for Live (sup 244)Pu in Deep-Sea Sediments: Preliminary Results of Method Development; Some Peculiarities of Quartz, Biotite and Garnet Transformation in Conditions of Step-like Shock Compression of Crystal Slate; Error Analysis of Remotely-Acquired Mossbauer Spectra; Cloud Activity on Titan During the Cassini Mission; Solar Radiation Pressure and Transient Flows on Asteroid Surfaces; Landing Site Characteristics for Europa 1: Topography; and The Crop Circles of Europa.

Source record↗
NASA NTRS2005

Magnetoresistive flux focusing eddy current flaw detection

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Wincheski, Russell A.↗
NASA NTRS2006

Identification of a Debris Cloud from the Nuclear Powered SNAPSHOT Satellite with Haystack Radar Measurements

Data from the MIT Lincoln Laboratory (MIT/LL) Long Range Imaging Radar (known as the Haystack radar) have been used in the past to examine families of objects from individual satellite breakups or families of orbiting objects that can be isolated in altitude and inclination. This is possible because for some time after a breakup, the debris cloud of particles can remain grouped together in similar orbit planes. This cloud will be visible to the radar, in fixed staring mode, for a short time twice each day, as the orbit plane moves through the field of view. There should be a unique three-dimensional pattern in observation time, range, and range rate which can identify the cloud. Eventually, through slightly differing precession rates of the right ascension of ascending node of the debris cloud, the observation time becomes distributed so that event identification becomes much more difficult. Analyses of the patterns in observation time, range, and range rate have identified good debris candidates released from the polar orbiting SNAPSHOT satellite (International Identifier: 1965-027A). For orbits near 90o inclination, there is essentially no precession of the orbit plane. The SNAPSHOT satellite is a well known nuclear powered satellite launched in 1965 to a near circular 1300 km orbit with an inclination of 90.3o. This satellite began releasing debris in 1979 with new pieces being discovered and cataloged over the years. 51 objects are still being tracked by the United States Space Surveillance Network. An analysis of the Haystack data has identified at least 60 pieces of debris separate from the 51 known tracked debris pieces, where all but 2 of the 60 pieces have a size less than 10cm. The altitude and inclination (derived from range-rate with a circular orbit assumption) are consistent with the SNAPSHOT satellite and its tracked debris cloud.

Stokely, C.↗
NASA NTRS1973

Lunar thermal measurements in conjunction with Project Apollo

Problems related to the feasibility of measuring lunar heat flow at the lunar surface are analyzed, and the findings which required that a drill be developed for lunar use are discussed. Numerical simulations were made of the in situ measurement of lunar thermal conductivity using a circular ring source of heat. The results of these simulations formed the basis for the criteria used in designing a subsurface thermal probe for ALSEP. Preliminary analyses are presented on the data obtained from the Apollo 15 and 17 missions.

Clark, S. P., Jr.↗
NASA NTRS1976

Multiplexor and sensor system tradeoff study

The influence of certain sensor parameters on the accuracy of information extracted from satellite image data is studied, using a digital processing flow to simulate the effects of the sensor parameters. The method employed was to select representative images; scan and digitize them; process the digital data to simulate the effects of presampling filters, instantaneous field of view (IFOV) size and shape, sampling rates, noise, and word length; record the processed data on film; evaluate the film images; and draw conclusions from the evaluations. The study showed that presampling filters are not required to suppress aliasing, that the choice of square and circular IFOV shapes is not important, and that increased horizontal and vertical sampling rates produce an increase in apparent resolution. Work with low-contrast targets revealed a definite maximum in the tradeoff between IFOV size and SNR.

Ferneyhough, D. G., Jr.↗
NASA NTRS1985

Near field pressure fluctuations of a circular jet

The relationship between the evolution of vortices in a circular jet and the generation of fluctuating pressure was studied, using an apparatus consisting of a jet nozzle connected to a stagnation chamber with a fifth-order polynomial contraction. The data were digitized and computer-processed. The constant pressure contours near the jet shoow that the evolution of coherent structures is the source of pressure perturbations. The data obtained in the vicinity of the jet indicate that two length scales govern the decay of the fluctuating pressure. A thin hydrodynamic near-field extends about 1 instability wavelength from the jet edge, and pressure decays exponentially. A thick acoustic near-field takes about ten acoustic wavelengths to reach the far field. The pressure disturbances decay algebraically in this region.

Lafouasse, B.↗
NASA NTRS1987

Investigation of generic hub fairing and pylon shapes to reduce hub drag

Reported are investigations of fairing configurations pointed toward substantially reducing hub drag. Experimental investigations have shown the importance of hub-fairing camber, lower-surface curvature, and relative size of the drag. The significance of pylon and hub fairings in combination have also been shown. Model test data presented here documented these findings, and also showed the effect of gaps and hub-fairing inclination angle on drag. From a drag standpoint, the best hub fairing had a circular arc, upper-surface curvature, a flat bottom surface, and 8.75% camber.

Stroub, Robert H.↗
NASA NTRS1986

Coherent shedding from a circular cylinder at critical, supercritical, and transcritical Reynolds numbers

Results are summarized from NASA-Langley studies of the mean drag and unsteady flow parameters of the flow around a circular cylinder at critical, supercritical and transcritical Re. Flow velocities of Mach 0.05-0.40 in the Low Turbulence Pressure Tunnel were used in conjunction with Re from 250,000-6.2 million. Data were collected in the wake and along the walls using pressure transducers. Corrections which were devised to calculate the Strouhal numbers in the presence of broadband signatures in the supercritical regime are described. The tests revealed, as found in previous tests, a discontinuity in the Strouhal number (from 0.2-0.43) in the supercritical regime.

Horvath, Thomas J.↗
NASA NTRS1987

1E 1048.5 + 5421 - A new 114 minute AM Herculis binary

The discovery of a new AM Herculis binary system, found as a serendipitous Einstein X-ray source, is described. Like the previously discovered mass-transfer binaries involving synchronously rotating magnetic white-dwarf primaries, the system exhibits strong circular polarization, X-ray and optical continuum variations, and optical emission lines, all of which seem to be modulated with these binary periods of 114.5 + or - 0.2 minutes. Although all data are not concurrent, the new system appears to possess the highest ratio of F(x)/F(opt) yet found for an AM Her system. The surprising accumulation of AM Her variables with periods near 114 minute is commented on.

Morris, Simon L.↗
NASA NTRS1988

The UCR gamma ray telescope data acquisition system

A description is given of an electronics system based on the DEC Falcon SBC-11/23+, which has been designed and built to support a balloon-borne double Compton gamma-ray telescope. The system provides support for commands, data acquisition, data routing and compression, and photomultiplier tube gain control. The software consists of a number of interrupt-driven routines of differing priorities to handle each system task. This includes two circular buffers for onboard processing and bit encoding before transmission of the information to the ground computer. Acquisition of gamma-ray events at rates above the 200-Hz telemetry constraint is easily achieved.

O'Neill, T. J.↗
NASA NTRS1987

Investigation of generic hub fairing and pylon shapes to reduce hub drag

This paper reports investigations of fairing configurations pointed toward substantially reducing hub drag. Experimental investigations have shown the importance of hub-fairing camber,lower-surface curvature, and relative size on the drag. The significance of pylon and hub fairings in combination have also been shown. Model test data presented here documented these findings, and also showed the effect of gaps and hub-fairing inclination angle on drag. From a drag standpoint, the best hub fairing had a circular arc, upper-surface curvature, a flat bottom surface, and 8.75 percent camber.

Stroub, Robert H.↗