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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Flame characteristics of a NASA contra swirler module

The structure of unconfined flames stabilized on a NASA contra-swirl can has been examined. The structure depends on reference velocity and fuel-air ratio, and photographic illustrations of representative examples of each flame type are shown. A highly compact flame is obtained over a narrow band of fuel-air ratios, within the total range over which flames may be stabilized, at high reference velocity (27.8 m/s). The compact structure can only be obtained with careful fuel nozzle location. Chemical concentration profiles, temperature profiles and sodium chloride seeding experiments all confirm the visual impression of compactness. A flame with 50% greater fuel throughput has a much less compact structure, which is reflected in lower maximum temperature, much more complex chemical concentration distributions and a more diffuse recirculation boundary as observed by sodium chloride seeding than in the compact flame. Each of these flames has not only an evident axial recirculation core but also a toroidal recirculation region over the bluff region between the inner and outer swirlers. In contrast, laser Doppler velocimetry measurements carried out on a flame with lower reference velocity (5.65 m/s) do not indicate the presence of a secondary recirculation region in this flame.

Thompson, D.↗
NASA NTRS1975

Energy, frequency, and distance of moonquakes at the Apollo 17 site

'Thermal' moonquakes have been detected at the Apollo 17 site. A typical event releases about 1 to 10 million ergs of energy. The annual seismic energy release for the events observed in the Taurus-Littrow Valley is estimated at 100 billion ergs. Such small events would not cause impossibly rapid erosion on either the North Massif or within the craters of the Central Cluster. Seismic events become increasingly frequent after sunrise and reach a maximum at sunset. The largest events, however, occur most commonly near lunar noon. Rise times of the seismic signals, after being calibrated by the well-located Lunar Seismic Profiling Experiment (LSPE) seismic sources, were used to estimate distances to the seismic events. Most seismic events (about 90%) appear to occur within 2.5 km of the seismometer array.

Cooper, M. R.↗
NASA NTRS1978

The radio telescope RATAN 600

A six-meter radio antenna having 900 reflector elements arranged on a 579 -meter diameter circle and located in the northern part of the Caucasian Mountains is described. The elements are about 7.4 m by 2 m resulting in a total reflector surface of about 10,000 sq m. Individual elements can be adjusted by changing 260 screws and can be rotated both horizontally and vertically as well as being moved translationally in the radial direction. The circular area is equipped with a grid of tracks where four asymmetric cylindrical paraboloids serving as subreflectors are located. The directional profile or observational direction of the antenna is achieved by shifting the subreflectors and changing the position of the reflecting elements with respect to the subreflectors. Different radio sources can be observed at the same time by using different subreflectors and their associated reflector sectors. Each subreflector is connected to a receiving station. Capabilities for spectroscopic observation are discussed.

Schwartz, R.↗
NASA NTRS1980

The structure and evolution of X-ray clusters of galaxies

Einstein Observatory observations of the structures of nearby X-ray clusters of galaxies are discussed in relation to dynamic cluster evolution. Examples of Virgo-type clusters, in which cool and hot gas associated with cluster members are presented and variations in surface brightness profile and the location of the cluster center are used to classify the observed clusters. The types of clusters observed are interpreted in terms of dynamic cluster evolution, with Virgo-type clusters with broad, highly clumped emission and low velocity dispersion representing early evolutionary stages, clusters containing a cD galaxy formed as the cluster evolves, and clusters with dominant galaxies and Coma-type clusters representing an equilibrium stage. X-ray emission from poor clusters of galaxies is also considered, and similarities between the presumably collisionally formed cD galaxies in rich and poor clusters are noted. Finally, observations of distant clusters are discussed, and it is noted that their analysis will lead to a better determination of the evolutionary sequence.

Jones, C.↗
NASA NTRS1985

Bending waves and the structure of Saturn's rings

The surface mass density profiles at four locations within Saturn's rings are calculated using Voyager spacecraft images of spiral bending waves. The identification of a feature in Saturn's outer B ring as Mimas's 4:2 bending waves is confirmed, and these 4:2 waves are analyzed to determine the surface density in Saturn's B ring. A fourth set of bending waves, the Mimas 7:4, located in the inner A ring, is identified and analyzed. Mimas's 5:3 and 8:5 bending waves, observed in the middle and outer A ring respectively, are reanalyzed.

Lissauer, J. J.↗
NASA NTRS1986

Strain accumulation and surface deformation along the San Andreas, California

Stressing and rupture of a locked zone adjacent to a creeping fault segment was studied with special reference to strength heterogeneity depthwise and along-strike. The resulting precursory temporal and spatial variations of surface strain rate profiles were compared to geodetic measurements on the San Andreas fault in central California. Crustal deformation in great California earthquake cycles was also studied with special reference to the temporal decay of strain rate observed since the 1957 and 1906 great earthquakes, and comtemporary surface strain rate and velocity profiles at several locations along the San Andreas. The effect of viscoelastic response in the deep aseismic shear zone on the surface deformation behavior was examined. Work was begun on a fundamental reformulation of the crustal deformation problem focusing on the crustal deformation process affected by deep aseismic slip as the slip zone progresses toward an instability and as deep seismic slip continues postseismically, the 3-D nature of the problem due to geometry and material heterogeneity, and the time-dependent source coming from the lithosphere/astenospheric coupling process.

Li, Victor C.↗
NASA NTRS1988

Solar response of the BATSE instrument on the gamma-ray observatory

The Burst and Transient Source Experiment (BATSE) on board the gamma ray observatory (GRO) aims at comprehensive observations of time profiles, spectra, and locations of high-energy transient sources. The mysterious cosmic gamma ray bursts provided the main motivation for the observations, but BATSE will make excellent observations of many classes of sources, and in particular solar flares. The solar response of BATSE, as inferred from its design parameters, is analyzed for two purposes: the optimization of the solar observations themselves, and the characterization of the solar effects on ordinary nonsolar observations.

Fishman, G. J.↗
NASA NTRS1991

Oscillating airfoil velocity field during large amplitude dynamic stall

The leading edge flowfield of an airfoil executing a sinusoidal oscillatory motion and experiencing dynamic stall under compressibility conditions has been studied using a two component LDV system. Phase averaged mean velocity measurements and some flow quantities derived from it are presented and discussed. The results indicate extremely large accelerations of the flow are present around the leading edge with mean velocity values 60 percent higher than and instantaneous velocities as large as 1.75 times the free stream velocity. The velocity profiles at certain locations over the airfoil resemble that of a wake.

Chandrasekhara, M. S.↗
NASA NTRS1998

Comparison of Spacecraft Contamination Models with Well-Defined Flight Experiment

The report presents analyzed surface areas on particular experiment trays from the Long Duration Exposure Facility (LDEF) for silicone-based molecular contamination. The trays for examination were part of the Ultra-Heavy Cosmic Ray Experiment (UHCRE). These particular trays were chosen because each tray was identical to the others in construction, and the materials on each tray were well known, documented, and characterized. In particular, a known specific source of silicone contamination was present on each tray. Only the exposure conditions varied from tray to tray. The results of post-flight analyses of surfaces of three trays were compared with the predictions of the three different spacecraft molecular contamination models. Phase one tasks included: 1) documenting the detailed geometry of the hardware; 2) determining essential properties of the anodized aluminum, Velcro(Tm), silverized Teflon(Tm), silicone gaskets, and DC6-1104(Tm) silicone adhesive materials used to make the trays, tray covers, and thermal control blankets; 3) selecting and removing areas from each tray; and 4) beginning surface analysis of the selected tray walls. Phase two tasks included: 1) completion of surface analysis measurements of the selected tray surface, 2) obtaining auger depth profiles at selected locations, and 3) running versions of the ISEM, MOFLUX, and PLIMP (Plume Impingement) contamination prediction models and making comparisons with experimental results.

Pippin, G. H.↗
NASA NTRS1998

Airborne Laser Altimetric Monitoring of the Rapid Evolution of Topography in the Long Valley, CA, Caldera

A consortium of investigators from several universities and Government agencies have conducted a series of aircraft topographic surveys over the Long Valley caldera, California. The region has a geologic history of extensive volcanism, and its central dome has recently been undergoing resurgent uplift episodes of up to 4 cm per year, a deformation rate that is still continuing. These surveys were conducted from the NASA WFF T39 jet aircraft, outfitted with a nadir-profiling altimetric laser (ATLAS), a GPS guidance system for in-flight precision navigation, two P-code GPS receivers, a Litton LTN92 inertial unit for attitude determination, and both video and still-frame aerial cameras. In addition, two base-station GPS receivers were deployed for post-flight differential navigation, complementing the permanent GPS station operated on the resurgent dome by JPL, and a kinematic automobile survey of roads crossing the area was conducted, thereby complementing the JPL kinematic GPS surveys of some of the same roads. Precision flying yielded multiple profiles along nearly identical paths, including crossing profiles over selected locations within the caidera and calibration flights over Mono Lake, and Lake Crowley. Data from the most recent survey in 1995 are at this time still being reduced, but the standard error of the mean is very low (< 3 mm), due to the high number of crossover points. We thus intend to evaluate the technique for measuring systematic changes in the dome height over time.

Rundle, John↗
NASA NTRS2002

Convective Bursts and Hot Towers Observed During CAMEX-3 and CAMEX-4

The role of convective bursts in the inner core regions of tropical storms has been if interest for many years with respect to their role in intensification. The structure of these convective bursts is best observed in satellite observations, but their structure has also been observed in some of the airborne radar studies over the past decade. Recently, a convective burst was documented during Hurricane Bonnie during NASA's Convection and Moisure Experiment-3 (CAMEX-3, 1998) conducted jointly with NOAA's Hurricane Field Program (Heymsfield et al., 2001). CAMEX-3 involved the NASA ER-2 high-altitude and DC-8 medium altitude aircraft instrumented with a variety of remote sensing instruments. The Bonnie convective burst was suggested to contribute intensification if ots warm core vased on radar measurements provided by the ER-2 Doppler Radar (EDOP). During the 2001 hurricane season, data sets form additional storms were collected during CAMEX-4. This paper documents the internal structure of convective bursts observed by EDOP and supporting measurements during foour storms (Bonnie, 1998; Georges, 1998; Chantal, 2001; Humberto, 2001) with respect to draft intensities, height profiles of reflectivity, location with respect to the storm center, occurence relative to the sotrm evolutjion, and upper level outlflows associated with the burst. These cases will be presented in the poster and will be compared with Bonnie's convective burst whic was associated with a strong subsiding current which appeared to contribute to the storm intensification. For one of the sotrms (Chantal), a very intense convective burst was nearly 100 km east of the low level circulation center and thus was infavorably located for intensifying the storm.

Heymsfield, Gerald↗
NASA NTRS2017

Modeling Solar Energetic Particle Events Using ENLIL Heliosphere Simulations

Solar energetic particle (SEP) event modeling (SEPMOD) has gained renewed attention in part because of the availability of a decade of multipoint measurements from STEREO (Solar TErrestrial RElations Observatory) and L1 (Lagrangian point 1) spacecraft at 1 AU (Astronomical Unit). These observations are coupled with improving simulations of the geometry and strength of heliospheric shocks obtained by using coronagraph images to send erupted material into realistic solar wind backgrounds. The STEREO and ACE (Aerosol, Cloud systems, ocean Ecosystems) measurements in particular have highlighted the sometimes surprisingly widespread nature of SEP events. It is thus an opportune time for testing SEP models, which typically focus on protons approximately 1-100 megaelectronvolts, toward both physical insight to these observations and potentially useful space radiation environment forecasting tools. Some approaches emphasize the concept of particle acceleration and propagation from close to the Sun, while others emphasize the local field line connection to a traveling, evolving shock source. Among the latter is the previously introduced SEPMOD treatment, based on the widely accessible and well-exercised WSA-ENLIL (Wang-Sheeley-Arge-ENLIL)-cone model. SEPMOD produces SEP proton time profiles at any location within the ENLIL domain. Here we demonstrate a SEPMOD version that accommodates multiple, concurrent shock sources occurring over periods of several weeks. The results illustrate the importance of considering longer-duration time periods and multiple CME (Coronal Mass Ejection) contributions in analyzing, modeling, and forecasting SEP events.

Luhmann, J. G.↗
NASA NTRS2018

TPSAS-NF1676L-30290-DND

The Summer 2017 Ozone Water Land Environmental Transition Study (OWLETS) mission set out to compare the differences in ozone concentrations between inland measurements of air quality, specifically at Langley Research Center (LaRC), and measurements taken over water, specifically on the Chesapeake Bay Bridge Tunnel (CBBT), as well as the vertical profiles above each location. Current weather models often predict a gradient in ozone concentration between land and ocean and this campaign attempted to capture this difference using hand-held Personal Ozone Monitors (POMs) in correspondence to ozonesondes and LIDAR measurements. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) is the first geostationary satellite that will take hourly measurements to monitor air pollutants across North America using solar backscatter. The small footprint allows for higher spatial resolution readings of many parameters including O3, NO2 , and aerosol. TEMPO’s higher resolution readings would benefit from validation techniques on the ground. Validation methods usually include comparison to air quality monitoring stations, but they could also incorporate other forms of validation such as comparison to small sensors. In cooperation with TEMPO, OWLETS aims to provide the user community high resolution temporal and spatial, both horizontal and vertical, variability of O3 simultaneously over the land and water during various air quality events to improve forecast models and air quality satellite retrievals. Together, these missions will improve spatial resolution and capture temporal variability of air quality over North America.

Emily Gargulinski↗
NASA NTRS2022

Celestial Mapping System Video Demonstration Part 4

The current presentation focuses on the work performed by the authors, to consume a unique dataset of super-enhanced images of the permanently shadowed regions (PSRs) at the lunar south pole which were produced by the Hyper-effective nOise Removal U-net Software (HORUS) tool. This tool was developed in direct support of NASA's VIPER and Artemis programs to enhance the extremely low-light images of the interior of PSRs and provide the first-time ability to see within these regions at 3m scale visibility. We focused on the region near Nobili crater, selected site for VIPER mission and stitched several images to create a high-resolution map of B01 crater, that included the visualization of PSRs. We have developed an in-built line of sight analysis tool in CMS, that analyzes the terrain profile and obstructions and provides the visibility of a given terrain for a remote observer. This tool was utilized to perform viewshed analysis to investigate the area inside the PSR B01, a remote observer such as a rover could see without actually crossing the region. This analysis was extended further to set different heights for various observers and then perform the viewshed analysis. The combined visibility profile at different locations could subsequently lead to traverse planning.

Mapping↗
NASA NTRSDate not supplied

Evaluation of Wall-Modeled Les for Flow Over A Multi-Element Airfoil

We perform wall-modeled large-eddy simulations (WMLES) of turbulent flow over a 30P30N multielement airfoil at various angles of attack to assess its ability to accurately predict lift using an unstructured node-based finite-volume methodology. The flow conditions are based on the experiments reported in Klausmeyer & Lin [NASA /TM-112858]. The oncoming flow Mach number is 0.2, and the stowed chord-based Reynolds number (𝑅𝑒𝑐) is 9 million. The angle of attack (𝛼) is varied between 8◦ and 23◦ with the expected stall angle of around 21◦. The simulated geometry is periodic in the span, thus any three-dimensional effects present in the experiment are ignored. We first analyze the predictions with baseline isotropic and anisotropic grids containing over 16 grid points per boundary-layer thickness. The near-wall streamwise/nominal spacing ratio is 0.4 at the leading/trailing edges of the slat, main element and flap, and 1 elsewhere, and the first wall-normal/nominal spacing ratio is 0.375 over most of the airfoil for the anisotropic grid, while these are unity for the isotropic grid. It is found that the predicted lift and wall pressures, near-wall velocity profiles, and the location of onset of resolved turbulence are sensitive to the near-wall grid anisotropy. Further sensitivities were explored at lower angles of attack by independently varying the streamwise and wall-normal grid anisotropies. The effects of both off-wall and near-wall grid refinement were also quantified. For the grid resolutions used here, our results suggest that the first wall-normal spacing, which coincides with the WMLES exchange location, has a dominant effect on the predictions for this flow configuration.

Computational Fluid Dynamics↗
NASA NTRS1995

Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog

Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with gaseous oxygen (GOX) under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from plus or minus 20% of the localized mean pressure to an acceptable range of plus or minus 1.5%. Embedded fine--wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or surface temperatures in comparison to the translucent fuel slabs.

Chiaverini, Martin J.↗
NASA NTRS2018

Homogenizing and Estimating the Uncertainty in NOAA's Long-Term Vertical Ozone Profile Records Measured with the Electrochemical Concentration Cell Ozonesonde

NOAA's program of long-term monitoring of the vertical distribution of ozone with electrochemical concentration cell (ECC) ozonesondes has undergone a number of changes over the 50-year record. In order to produce a homogenous data set, these changes must be documented and, where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA's ozonesonde data records that corrects for these changes using the rawest form of the data (cell current and pump temperature) in native resolution as well as a point-by-point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA's network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of +/- 4-6% in the stratosphere and +/- 5-20% in the troposphere. A comparison of the integrated column ozone from the ozonesonde profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within +/- 5% for >70% of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet (SBUV) instruments.

ozonesonde↗
NASA NTRS2007

DIAL Measurements of Free-Tropospheric Ozone Profiles in Huntsville, AL

A tropospheric ozone Differential Absorption Lidar (DIAL) system, developed jointly by NASA and the University of Alabama at Huntsville (UAH), measures free-tropospheric ozone profiles between 4-10 km. Located at 192 meters altitude in the Regional Atmospheric Profiling Laboratory for Discovery (RAPCD) on the UAH campus in Huntsville, AL, USA, this tropospheric ozone lidar operates under both daytime and nighttime conditions. Frequent coincident ozonesonde flights and theoretical calculations provide evidence to indicate the retrieval accuracy ranges from better than 8% at 4km to 40%-60% at 10 kin with 750-m vertical resolution and 30-minute integration. With anticipated improvements to allow retrievals at both higher and lower altitudes, this ozone lidar, along with co-located aerosol and Doppler Wind Lidars, will provide a unique 18 dataset for investigations of PBL and free-tropospheric chemical and dynamic processes.

Kuang, Shi↗