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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Training Data Optimized and Conditioned to Learn Characteristic Patterns of Vibrating Blisks and Fan Blades

At the NASA Glenn Research Center, we have been training artificial neural networks to interpret the characteristic patterns (see the leftmost image) generated from electronic holograms of vibrating structures. These patterns not only visualize the vibration properties of structures, but small changes in the patterns can indicate structural changes, cracking, or damage. Neural networks detect these small changes well. Our objective has been to adapt the neural-network, electronic-holography combination for inspecting components in Glenn's Spin Rig.

Decker, Arthur J.↗
NASA NTRS1991

Three-Dimensional Analysis and Modeling of a Wankel Engine

A new computer code, AGNI-3D, has been developed for the modeling of combustion, spray, and flow properties in a stratified-charge rotary engine (SCRE). The mathematical and numerical details of the new code are described by the first author in a separate NASA publication. The solution procedure is based on an Eulerian-Lagrangian approach where the unsteady, three-dimensional Navier-Stokes equations for a perfect gas-mixture with variable properties are solved in generalized, Eulerian coordinates on a moving grid by making use of an implicit finite-volume, Steger-Warming flux vector splitting scheme. The liquid-phase equations are solved in Lagrangian coordinates. The engine configuration studied was similar to existing rotary engine flow-visualization and hot-firing test rigs. The results of limited test cases indicate a good degree of qualitative agreement between the predicted and measured pressures. It is conjectured that the impulsive nature of the torque generated by the observed pressure nonuniformity may be one of the mechanisms responsible for the excessive wear of the timing gears observed during the early stages of the rotary combustion engine (RCE) development. It was identified that the turbulence intensities near top-dead-center were dominated by the compression process and only slightly influenced by the intake and exhaust processes. Slow mixing resulting from small turbulence intensities within the rotor pocket and also from a lack of formation of any significant recirculation regions within the rotor pocket were identified as the major factors leading to incomplete combustion. Detailed flowfield results during exhaust and intake, fuel injection, fuel vaporization, combustion, mixing and expansion processes are also presented. The numerical procedure is very efficient as it takes 7 to 10 CPU hours on a CRAY Y-MP for one entire engine cycle when the computations are performed over a 31 x16 x 20 grid.

Raju, M. S.↗
NASA NTRSDate not supplied

A Virtual Reality Planning Environment for High-Risk, High-Latency Teleoperation

Teleoperation of robots in space is challenging due to high latency and limited workspace visibility. Previously, the Interactive Planning and Supervised Execution (IPSE) and Augmented Virtuality systems were developed to reduce failure risk. These tools were visualized on a 3D da Vinci surgical console and operated using the da Vinci manipulators or visualized on conventional monitors and operated with a keyboard and mouse. Experimental studies indicated operator preference for the latter. In this work, we develop a 3D virtual reality (VR) interface for IPSE, implemented on a Meta Quest 2 head-mounted display (HMD), and evaluate it against the prior 2D, keyboard-and-mouse-based interface. The results demonstrate improved operator load with the 3D VR interface, with no decrease in task performance, while also providing cost and portability benefits compared to the conventional 2D interface.

Will Pryor↗
NASA NTRS1996

Macular Preprocessing of Linear Acceleratory Stimuli: Implications for the Clinic

Three-dimensional reconstructions of innervation patterns in rat maculae were carried out using serial section images sent to a Silicon Graphics workstation from a transmission electron microscope. Contours were extracted from mosaicked sections, then registered and visualized using Biocomputation Center software. Purposes were to determine innervation patterns of type II cells and areas encompassed by vestibular afferent receptive fields. Terminals on type II cells typically are elongated and compartmentalized into parts varying in vesicular content; reciprocal and serial synapses are common. The terminals originate as processes of nearby calyces or from nerve fibers passing to calyces outside the immediate vicinity. Thus, receptive fields of the afferents overlap in unique ways. Multiple processes are frequent; from 4 to 6 afferents supply 12-16 terminals on a type II cell. Processes commonly communicate with two type II cells. The morphology indicates that extensive preprocessing of linear acceleratory stimuli occurs peripherally, as is true also of visual and olfactory systems. Clinically, this means that loss of individual nerve fibers may not be noticed behaviorally, due to redundancy (receptive field overlap). However, peripheral processing implies the presence of neuroactive agents whose loss can acutely or chronically alter normal peripheral function and cause balance disorders. (Platform presentation preferred - Theme 11)

Ross, M. D.↗
NASA NTRS2016

The Mass Index and Total Mass of the Geminid Meteoroid Stream as Found with Radar, Optical, and Lunar Impact Data

The Geminid meteor shower was observed in 2015 using the Western Meteor Physics Group’s Canadian Meteor Orbit Radar (CMOR), Marshall Space Flight Center’s (MSFC) eight wide-field optical cameras, and MSFC’s lunar impact monitoring. These observations allowed Geminid fluxes to be calculated in three unique mass-ranges, from 1.8 (exponent -4) grams to 30 grams. From these fluxes, a mass index of 1.68 plus or minus 0.04 is found, which is in excellent agreement with past Geminid mass indices such as 1.69 found by Blaauw et al using only radar data and 1.7 found by Arlt and Rendtel using visual data. This mass index, however, is found over five orders of magnitude of mass, which allows a higher level of confidence that this mass index holds over a large portion of the stream. Mass indices are an important quantity to be accurately measured for a shower, indicating the distribution of mass in a well-studied stream in which we know the parent body (3200 Phaethon), improving forecasts of the shower activity, and allow fluxes to be scaled to high and low masses. The quantities derived here, along with a profile of the Geminid meteor shower activity in 2015 from CMOR, permit the total Geminid mass the Earth encountered in 2015 to be found, along with a minimum total mass of the Geminid meteoroid stream. Attempts have been made in the past to measure the mass of meteoroid streams using Zenithal Hourly Rate (ZHR) profiles, but here this new and improved treatment uses empirically derived fluxes and measured mass indices for the 2015 encounter with the meteoroid stream. This is to be compared with other meteoroid stream mass estimates including that of the Perseids, caused by comet Swift Tuttle.

Blaauw, R.↗
NASA NTRS1999

Effects of body orientation and rotation axis on pitch visual-vestibular interaction

Spatial transformations of the vestibular-optokinetic system must account for changes in head position with respect to gravity in order to produce compensatory oculomotor responses. The purpose of this experiment was to study the influence of gravity on the vestibulo-ocular reflex (VOR) in darkness and on visual-vestibular interaction in the pitch plane in human subjects using two different comparisons: (1) Earth-horizontal axis (EHA) rotation about an upright versus a supine body orientation, and (2) Earth-horizontal versus Earth-vertical (EVA) rotation axes. Visual-vestibular responses (VVR) were evaluated by measuring the slow phase velocity of nystagmus induced during sinusoidal motion of the body in the pitch plane (at 0.2 Hz and 0.8 Hz) combined with a constant-velocity vertical optokinetic stimulation (at +/- 36 degrees/s). The results showed no significant effect on the gain or phase of the VOR in darkness or on the VVR responses at 0.8 Hz between EHA upright and EHA supine body orientations. However, there was a downward shift in the VOR bias in darkness in the supine orientation. There were systematic changes in VOR and VVR between EHA and EVA for 0.2 Hz, including a reduced modulation gain, increased phase lead, and decreased bias during EVA rotation. The same trend was also observed at 0.8 Hz, but at a lesser extent, presumably due to the effects of eccentric rotation in our EVA condition and/or to the different canal input across frequencies. The change in the bias at 0.2 Hz between rotation in darkness and rotation with an optokinetic stimulus was greater than the optokinetic responses without rotation. During EHA, changes in head position relative to gravity preserve graviceptor input to the VVR regardless of body orientation. However, the modifications in VVR gain and phase when the rotation axis is aligned with gravity indicate that this graviceptive information is important for providing compensatory eye movements during visual-vestibular interaction in the pitch plane.

Non-NASA Center↗
NASA NTRS1978

The verification of LANDSAT data in the geographical analysis of wetlands in west Tennessee

The reliability of LANDSAT imagery as a medium for identifying, delimiting, monitoring, measuring, and mapping wetlands in west Tennessee was assessed to verify LANDSAT as an accurate, efficient cartographic tool that could be employed by a wide range of users to study wetland dynamics. The verification procedure was based on the visual interpretation and measurement of multispectral imagery. The accuracy testing procedure was predicated on surrogate ground truth data gleaned from medium altitude imagery of the wetlands. Fourteen sites or case study areas were selected from individual 9 x 9 inch photo frames on the aerial photography. These sites were then used as data control calibration parameters for assessing the cartography accuracy of the LANDSAT imagery. An analysis of results obtained from the verification tests indicated that 1:250,000 scale LANDSAT data were the most reliable scale of imagery for visually mapping and measuring wetlands using the area grid technique. The mean areal percentage of accuracy was 93.54 percent (real) and 96.93 percent (absolute). As a test of accuracy, the LANDSAT 1:250,000 scale overall wetland measurements were compared with an area cell mensuration of the swamplands from 1:130,000 scale color infrared U-2 aircraft imagery. The comparative totals substantiated the results from the LANDSAT verification procedure.

Rehder, J.↗
NASA NTRS1996

Perceived visual speed constrained by image segmentation

Little is known about how or where the visual system parses the visual scene into objects or surfaces. However, it is generally assumed that the segmentation and grouping of pieces of the image into discrete entities is due to 'later' processing stages, after the 'early' processing of the visual image by local mechanisms selective for attributes such as colour, orientation, depth, and motion. Speed perception is also thought to be mediated by early mechanisms tuned for speed. Here we show that manipulating the way in which an image is parsed changes the way in which local speed information is processed. Manipulations that cause multiple stimuli to appear as parts of a single patch degrade speed discrimination, whereas manipulations that perceptually divide a single large stimulus into parts improve discrimination. These results indicate that processes as early as speed perception may be constrained by the parsing of the visual image into discrete entities.

NASA Discipline Neuroscience↗
NASA NTRS2006

Bragg Curve, Biological Bragg Curve and Biological Issues in Space Radiation Protection with Shielding

The space environment consists of a varying field of radiation particles including high-energy ions, with spacecraft shielding material providing the major protection to astronauts from harmful exposure. Unlike low-LET gamma or X-rays, the presence of shielding does not always reduce the radiation risks for energetic charged particle exposure. Since the dose delivered by the charged particle increases sharply as the particle approaches the end of its range, a position known as the Bragg peak, the Bragg curve does not necessarily represent the biological damage along the particle traversal since biological effects are influenced by the track structure of both primary and secondary particles. Therefore, the biological Bragg curve is dependent on the energy and the type of the primary particle, and may vary for different biological endpoints. To achieve a Bragg curve distribution, we exposed cells to energetic heavy ions with the beam geometry parallel to a monolayer of fibroblasts. Qualitative analyses of gamma-H2AX fluorescence, a known marker of DSBs, indicated increased clustering of DNA damage before the Bragg peak, enhanced homogenous distribution at the peak, and provided visual evidence of high linear energy transfer (LET) particle traversal of cells beyond the Bragg peak. A quantitative biological response curve generated for micronuclei (MN) induction across the Bragg curve did not reveal an increased yield of MN at the location of the Bragg peak. However, the ratio of mono-to bi-nucleated cells, which indicates inhibition in cell progression, increased at the Bragg peak location. These results, along with other biological concerns, show that space radiation protection with shielding can be a complicated issue.

Honglu, Wu↗
NASA NTRS2000

Experimental Study of the Structure of a Wingtip Vortex

A complete look at the near-field development and subsequent role-up of a wingtip vortex from a NACA 0015 wing section is investigated. Two separate but equally important surveys of the vortex structure in the region adjacent to the wingtip and approximately one chord length downstream of the trailing edge are performed. The two surveys provide qualitative flow-visualization an quantitative velocity measurement data. The near-field development and subsequent role-up of the vortex structures is strongly influenced by the angle-of-attack and the end-cap treatment of the wing section. The velocity field near the wingtip of the NACA 0015 wing section was measured with a triple-sensor hot wire probe and compared to flow visualization images produced with titanium tetrachloride smoke injection and laser illumination. The flat end-cap results indicate the formation of multiple, relatively strong vortex structures as opposed to the formation of a single vortex produced with the round end-cap. The multiple vortices generated by the flat end-cap are seen to rotate around a common ce te in a helical pattern until they eventually merge into a single vortex. Compared to a non-dimensional loading parameter, the results of the velocity and flow visualization data shows a "jetlike" axial velocity profile for loading parameter values on the order of 0.1 and a "wakelike" profile for much lower loading parameter values.

Anderson, Elgin A.↗
NASA NTRS1975

Gypsy moth defoliation assessment: Forest defoliation in detectable from satellite imagery

The author has identified the following significant results. ERTS-1 imagery obtained over eastern Pennsylvania during July 1973, indicates that forest defoliation is detectable from satellite imagery and correlates well with aerial visual survey data. It now appears that two damage classes (heavy and moderate-light) and areas of no visible defoliation can be detected and mapped from properly prepared false composite imagery. In areas where maple is the dominant species or in areas of small woodlots interspersed with agricultural areas, detection and subsequent mapping is more difficult.

Moore, H. J.↗
NASA NTRS1976

LANDSAT observations of ocean dump plume movement and dispersion

The author has identified the following significant results. Eighteen LANDSAT images were analyzed to study the dispersion and movement of ocean dump plumes thirty-eight miles southeast of Cape Henlopen, Delaware, at the disposal site for waste discharged from a plant producing titanium dioxide. Long visual persistence was explained by the formation of a suspended ferric floc. Spectrometric measurements indicate that upon combining with sea water the acid waste develops a strong reflectance peak in the band 0.55 to 0.60 micron region, resulting in a stronger contrast in the MSS band 4 than the other bands. Predominant direction of movement of the waste plumes was to the southeast. Average drift velocity for surface drogues and the waste plumes was about 0.5 knots. The water at the test site was highly stratified and stable in the summer and nearly homogenous in the winter.

Klemas, V.↗
NASA NTRS1977

Radii and albedos of four Trojan asteroids and Jovian satellites 6 and 7

Results are reported for radiometric measurements of broadband 20-micron fluxes from the Trojan asteroids 617 Patroclus, 624 Hektor (for which the broadband 10-micron flux was also measured), 1172 Aeneas, and 1173 Anchises as well as from the outer Jovian satellites Himalia (J6) and Elara (J7). Geometric albedos and radii for the six objects are derived from the corrected monochromatic fluxes and visual magnitudes. It is found that all the objects have exceedingly low geometric albedos, indicating that the Trojans and possibly the outer Jovian satellites constitute a distinct class of small solar-system bodies. The composition of the Trojan asteroids is considered on the basis of available sizes, albedos, and shapes. Revised tables of the albedos and radii of all the Jovian satellites are presented. It is concluded that the Trojans are not composed primarily of ice and that an asteroidal origin for the comets of the Jupiter group is unlikely.

Cruikshank, D. P.↗
NASA NTRS1979

The orbital period of Algol - 1964 to 1978

A photoelectric observation of minimum light for Algol is reported: JD 2443565.5785 (visual) and JD 2443565.5802 (blue). The times of minima obtained between 1964 and 1978 indicate that a period decrease may have occurred about 1975. It is suggested that this period change, as well as the radio and X-ray activity and spectroscopic anomalies observed during 1975, may have been due to a mass-transfer event that occurred around that time.

Mallama, A. D.↗
NASA NTRS1982

Chromospheres and coronae in the T Tauri stars

The Tauri stars exhibit strong far ultraviolet emission lines of C II, III, IV; OI; Si II, III; IV; and sometimes N V and He II. Surface fluxes of the lines for several T Tauri stars were computed, drawing upon both International Ultraviolet Explorer observations and published spectra. The surface fluxes are quite high. The FUV lines together account for 0.1% of the stellar luminosity. These results indicate the presence of active relatively dense chromospheres. The Tauri stars showing very strong visual emission spectra exhibit weakened high temperature FUV lines of C IV and N V, as well as He II which may be produced by X-rays. In the same stars, no X-ray emission was detected with Einstein. Among all the T Tauri stars the X-ray luminosities are deficient by factors of 100 to 1000 compared to the FUV lines. It is argued that the X-ray flux has not been heavily absorbed by circumstellar gas, as has been previously suggested, but that the X-rays are truly underluminous, perhaps due to the stellar wind. It is suggested that the birth and development of the chromosphere and corona may be occurring during the T Tauri stage of protostellar evolution.

Imhoff, C. L.↗
NASA NTRS1991

Some preliminary results of brush seal/rotor interference effects on leakage at zero and low RPM using a tapered-plug rotor

Some preliminary brush seal leakage results for ambient temperature air are presented. Data for four nominal brush rotor radial clearances of -0.09, -0.048, -0.008, and 0.035 mm were taken by using a tapered plug rotor at 0 and 400 rpm with rotor runout of 0.127 mm peak to peak. The brush seal nominal bore diameter was 38 mm with 0.05 mm bristles at 200 bristles/mm of circumference and a 0.61 mm fence height. Leakages were greater than predicted, but agreement was reasonable. Leakage rates were not significantly altered by hysteresis or inlet flow variations. Visualization studies showed that the bristles followed the 400 rpm excitation, and loading studies indicated that bristles slid relative to one another.

Hendricks, R. C.↗
NASA NTRS1987

Comparison of smooth pursuit and combined eye-head tracking in human subjects with deficient labyrinthine function

The effects of deficient labyrinthine function on smooth visual tracking with the eyes and head were investigated, using ten patients with bilateral peripheral vestibular disease and ten normal controls. Active, combined eye-head tracking (EHT) was significantly better in patients than smooth pursuit with the eyes alone, whereas normal subjects pursued equally well in both cases. Compensatory eye movements during active head rotation in darkness were always less in patients than in normal subjects. These data were used to examine current hypotheses that postulate central cancellation of the vestibulo-ocular reflex (VOR) during EHT. A model that proposes summation of an integral smooth pursuit command and VOR/compensatory eye movements is consistent with the findings. Observation of passive EHT (visual fixation of a head-fixed target during en bloc rotation) appears to indicate that in this mode parametric gain changes contribute to modulation of the VOR.

Leigh, R. J.↗
NASA NTRS1991

Some preliminary results of brush seal/rotor interference effects on leakage at zero and low rpm using a tapered-plug rotor

Some preliminary brush seal leakage results for ambient-temperature air are presented. Data for four nominal brush-rotor radial clearances of -0.09, -0.048, -0.008, and 0.035 mm were taken by using a tapered plug rotor at 0 and 400 rpm with rotor runout of 0.127 mm peak to peak. The brush seal nominal bore diameter was 38 mm with 0.05-mm bristles at 200 bristles/mm of circumference and a 0.61-mm fence height. Leakages were greater than predicted, but agreement was reasonable. Leakage rates were not significantly altered by hysteresis or inlet flow variations. Visualization studies showed that the bristles followed the 400-rpm excitation, and loading studies indicated that bristles slid relative to one another.

Hendricks, R. C.↗