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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Mixing Process in Ejector Nozzles Studied at Lewis' Aero-Acoustic Propulsion Laboratory

The NASA Lewis Research Center has been studying mixing processes in ejector nozzles for its High Speed Research (HSR) Program. This work is directed at finding ways to minimize the noise of a future supersonic airliner. Much of the noise such an airplane would generate would come from the nozzle, where a hot, high-speed jet exits the engine. Several different nozzle configurations were used to produce nozzle systems with different acoustical and aerodynamic characteristics. The acoustical properties were measured by an array of microphones in an anechoic chamber, and the aerodynamics were measured by traditional pressure and temperature instruments as well as by Laser Doppler Velocimetry (LDV), a technique for visualizing the airflow pattern without disturbing it. These measurements were put together and compared for different configurations to examine the relationships between mixing and noise generation. The mixer-ejector nozzle with the installed flow-visualization windows (foreground), the optical equipment and the supporting structure for the Laser Doppler Velocimetry flow visualization (midfield), and the sound-absorbing wedges used to create an anechoic environment for acoustic testing (background) is shown. The High Speed Research Program is a NASA-funded effort, in cooperation with the U.S. aerospace industry, to develop enabling technologies for a future supersonic airliner. One of the technological barriers being addressed is noise generated during near-airport operation. The mixer-ejector nozzle concept is being examined as a way to reduce jet noise while maintaining thrust. Ambient air is mixed with the high-velocity engine exhaust to reduce the jet velocity and hence the noise generated by the jet. The model was designed and built by Pratt & Whitney under NASA contract. The test, completed in June 1995, was conducted in Lewis' Aero-Acoustic Propulsion Laboratory.

Source record↗
NASA NTRS2019

Numerical analysis of unsteady flow in a converging-diverging nozzle

This study investigates the physics of jet noise by the numerical solution of the three dimensional unsteady Navier-Stokes equations for a low-supersonic jet (Mach numbers on the order of 1.4) from a converging-diverging (C-D) nozzle and mixing with a subsonic surrounding flow. The numerical method used for the solution of these equations is the second order accurate MacCormack explicit predictor-corrector scheme. The numerical results are compared to the experimental results of Yamamoto for the same C-D nozzle geometry and similar operating conditions. The goal of the study is to use numerical simulation techniques to resolve accurately physical processes which contribute to jet noise, and to assess whether performing these simulations in a three dimensional geometry is worth the additional cost in computing resources as compared to a comparable simulation on a two dimensional planar or axisymmetric geometry. Scientific visualization is used to observe the spreading characteristics of the jet, as well as to examine the structure of the shocks within the jet core. The time average velocity and turbulence intensity level at various locations are computed and compared with experimental results. A two point space-time cross correlation is used to compute the mean convection speed through the shear layer, and these predictions are compared with results from theory.

James N Scott↗
NASA NTRS1972

Ultraviolet photometry of the moon with the celescope experiment on the OAO-2

Thirteen television frames of the moon taken in the wavelength regions of 1350-2150 A by filter U sub 3 and 1050-2150 A by filter U sub 4 in the celescope experiment are discussed. The data include phase angles from -81 deg to -26 deg. The brightness dependence on phase angle differs slightly from that of visual observations. The brightness dependence on selenographical longitude is compared with the theoretical photometric function derived by Hapke.

Ahmad, I. A.↗
NASA NTRS1972

Ultraviolet photometry of the moon with the celescope experiment on the OAO-II.

Thirteen television frames of the moon taken in the wavelength regions of 1350 to 2150 A by filter U3 and 1050 to 2150 A by filter U4 of the Smithsonian Astrophysical Observatory's Celescope experiment are discussed. The data include phase angles from -81 to -26 deg. The brightness dependence on phase angle differs slightly from that of visual observations. The brightness dependence on selenographical longitude is compared with the theoretical photometric function derived by Hapke.

Ahmad, I. A.↗
NASA NTRS1974

Study of the relation between Pc 3 micropulsations and magnetosheath fluctuations and for the multisatellite multimeasurement investigation of earths bow shock

Hourly averages of HEOS A interplanetary field and plasma parameters are compared with micropulsation spectrograms taken by auroral zone stations. Visual evaluation of tungsten induction coil records and a statistical summary indicate a class of pulsations sometimes in the Pc 3, sometimes in the Pc 4 range, whose appearance correlates with solar wind field flow alignment. It is concluded that there is a pulsation phenomenon of variable period strongly associated with certain interplanetary field directions.

Greenstadt, E. W.↗
NASA NTRS1978

The ratio of carbon monoxide to molecular hydrogen in interstellar dark clouds

LTE (C-13)O column densities are compared with the corresponding values of beam-convolved visual extinction at more than 100 locations within 38 different interstellar dark clouds. A roughly linear correlation is found to exist between these two quantities for visual extinctions in the range from about 1.5 to 5 mag. It is argued that this correlation can be extended up to about 10 mag and that the standard gas-to-extinction ratio can be expected to remain valid in the sources studied. The correlation of LTE (C-13)O column density with visual extinction is used to obtain an equation for the H2 column density associated with a given (C-13)O column density. It is shown that if the clouds studied are assumed to be chemically homogeneous, the equation obtained implies that at least 12% of all gas-phase carbon is in the form of CO. Comparison of the observational data with various theories proposed for molecule formation in dark clouds indicates that Langer's (1977) ion-molecule scheme accounts well for the observations when the fractionation channel of Watson et al. (1976) is included.

Dickman, R. L.↗
NASA NTRS1987

Free-wake analysis of a rotor in hover

A numerical method based on the axisymmetric, incompressible Navier-Stokes equations is combined with a lifting surface code to predict the vortex wake of hovering rotors. The lifting surface code, AMI Hover, is used to obtain the circulation distribution on the blade. This circulation distribution is fed into the Navier-Stokes code to compute the vortex wake under this specified circulation distribution. An iteration approach is used between these two codes to converge the circulation distribution and the shape of the vortex wake. A relaxation scheme is developed to resolve the instability encountered among the tip vortices. A reconcentration scheme is used to solve the diffusion problem due to the strong artificial viscosity. The results from the present method are compared with experimental data obtained by smoke-flow visualization and hot-wire measurements for several rotor blade configurations. The comparisons show that the present method is able to predict the complex wake system shed by a hovering rotor.

Chen, C. S.↗
NASA NTRS1993

Investigation of a strut/endwall interaction in supersonic annular flow

A combined experimental and numerical investigation of strut/endwall interactions within an annular duct having a supersonic core flow has been conducted. Four diamond-shaped struts with a 7 deg half angle were positioned circumferentially equidistant within an annular duct having a gap height of 0.7 strut chords, and an inner-to-outer wall radius ratio of 0.7. Turbulent boundary layers exist on both inner and outer walls of the duct, but have not merged. The core flow upstream of the struts is uniform at a nominal Mach number of 3.0 and a Reynolds number of 3 x 10 exp 5 based on the strut chord length. Experimental results, which include Pitot pressure distributions within the flow field, static pressure distributions on the inner and outer walls of the duct, and oil flow visualization on the centerbody and strut, are presented and compared with CFD predictions. Secondary flows associated with the interactions are examined including the trajectories of the horseshoe vortices formed at the leading and trailing edges of the strut and the trajectories of the vortices formed in the corner of the strut/endwall intersection.

Williams, K. E.↗
NASA NTRS1997

Annual Sea Level Variability Induced by Changes in Sea Ice Extent and Accumulation on Ice Sheets: An Assessment Based on Remotely Sensed Data

Changes of mean annual net accumulation at the surface on the grounded ice sheets of East Antarctica, West Antarctica, and Greenland in response to variations in sea ice extent are estimated using grid-point values 100 km apart. The data bases are assembled principally by bilinear interpolation of remotely sensed brightness temperature (Nimbus-5 ESMR, Nimbus-7 SMMR), surface temperature (Nimbus-7 THIR), and surface elevation (ERS-1 radar altimeter). These data, complemented by field data where remotely sensed data are not available, are used in multivariate analyses in which mean annual accumulation (derived from firn emissivity) is the dependent variable; the independent variables are latitude, surface elevation, mean annual surface temperature, and mean annual distance to open ocean (as a source of energy and moisture). The last is the shortest distance measured between a grid point and the mean annual position of the 10% sea ice concentration boundary, and is used as an index of changes in sea ice extent as well as of mean concentration. Stepwise correlation analyses indicate that variations in sea ice extent of +/-50 km would lead to changes in accumulation inversely of +/-4% on East Antarctica, +/- 10% on West Antarctica, and +4% on Greenland. These results are compared with those obtained in a previous study using visually interpolated values from contoured compilations of field data; they substantiate the findings for the Antarctic ice sheets (+/-4% on East Antarctica, +/-9% in West Antarctica), and suggest a reduction by one half of the probable change of accumulation on Greenland (from +/-8%). The results also suggest a reduction of the combined contribution to sea level variability to +/- 0.19 mm/a (from +/- 0.22 mm/a).

Zwally, H. J.↗
NASA NTRS2000

Volatile Removal Assembly Flight Experiment and KC-135 Packed Bed Experiment: Results and Lessons Learned

The Volatile Removal Assembly (VRA) is a high temperature catalytic oxidation process that will be used as the final treatment for recycled water aboard the International Space Station (ISS). The multiphase nature of the process had raised concerns as to the performance of the VRA in a microgravity environment. To address these concerns, two experiments were designed. The VRA Flight Experiment (VRAFE) was designed to test a full size VRA under controlled conditions in microgravity aboard the SPACEHAB module and in a 1 -g environment and compare the performance results. The second experiment relied on visualization of two-phase flow through small column packed beds and was designed to fly aboard NASA's microgravity test bed plane (KC-135). The objective of the KC-135 experiment was to understand the two-phase fluid flow distribution in a packed bed in microgravity. On Space Transportation System (STS) flight 96 (May 1999), the VRA FE was successfully operated and in June 1999 the KC-135 packed bed testing was completed. This paper provides an overview of the experiments and a summary of the results and findings.

Holder, Donald W.↗
NASA NTRS2009

Influence of Combined Whole-Body Vibration Plus G-Loading on Visual Performance

Recent engineering analyses of the integrated Ares-Orion stack show that vibration levels for Orion crews have the potential to be much higher than those experienced in Gemini, Apollo, and Shuttle vehicles. Of particular concern to the Constellation Program (CxP) is the 12 Hz thrust oscillation (TO) that the Ares-I rocket develops during the final ~20 seconds preceding first-stage separation, at maximum G-loading. While the structural-dynamic mitigations being considered can assure that vibration due to TO is reduced to below the CxP crew health limit, it remains to be determined how far below this limit vibration must be reduced to enable effective crew performance during launch. Moreover, this "performance" vibration limit will inform the operations concepts (and crew-system interface designs) for this critical phase of flight. While Gemini and Apollo studies provide preliminary guidance, the data supporting the historical limits were obtained using less advanced interface technologies and very different operations concepts. In this study, supported by the Exploration Systems Mission Directorate (ESMD) Human Research Program, we investigated display readability-a fundamental prerequisite for any interaction with electronic crew-vehicle interfaces-while observers were subjected to 12 Hz vibration superimposed on the 3.8 G loading expected for the TO period of ascent. Two age-matched groups of participants (16 general population and 13 Crew Office) performed a numerical display reading task while undergoing sustained 3.8 G loading and whole-body vibration at 0, 0.15, 0.3, 0.5, and 0.7 g in the eyeballs in/out (x-axis) direction. The time-constrained reading task used an Orion-like display with 10- and 14-pt non-proportional sans-serif fonts, and was designed to emulate the visual acquisition and processing essential for crew system monitoring. Compared to the no-vibration baseline, we found no significant effect of vibration at 0.15 and 0.3 g on task error rates (ER) or response times (RT). Significant degradations in both ER and RT, however, were observed at 0.5 and 0.7 g for 10-pt, and at 0.7 g for 14-pt font displays. These objective performance measures were mirrored by participants' subjective ratings. Interestingly, we found that the impact of vibration on ER increased with distance from the center of the display, but only for vertical displacements. Furthermore, no significant ER or RT aftereffects were detected immediately following vibration, regardless of amplitude. Lastly, given that our reading task required no specialized spaceflight expertise, our finding that effects were not statistically distinct between our two groups is not surprising. The results from this empirical study provide initial guidance for evaluating the display readability trade-space between text-font size and vibration amplitude. However, the outcome of this work should be considered preliminary in nature for a number of reasons: 1. The single 12 Hz x-axis vibration employed was based on earlier load-cycle models of the induced TO environment at the end of Ares-I first stage flight. Recent analyses of TO mitigation designs suggest that significant concurrent off-axis vibration may also occur. 2. The shirtsleeve environment in which we tested fails to capture the full kinematic and dynamic complexity of the physical interface between crewmember and the still-to-bematured helmet-suit-seat designs, and the impact these will have for vibration transmission and consequent performance. 3. By examining performance in this reading and number processing task, we are only assessing readability, a first and necessary step that in itself does not directly address the performance of more sophisticated operational tasks such as vehicle-health monitoring or manual control of the vehicle.

readability↗
NASA NTRS2022

Reservoir Assessment Tool 2.0: Stakeholder driven improvements to satellite remote sensing based reservoir monitoring

In light of the rapidly increasing regulation of rivers due to planned and constructed reservoirs, monitoring reservoir operations has become very crucial. The Reservoir Assessment Tool (RAT) framework was developed to monitor reservoir operations globally, using hydrological modeling and satellite observations. With feedback from stakeholders, improvements in the RAT framework are demonstrated in this study using the Mekong River Basin as an example. A novel multi-sensor reservoir area mapping technique was developed using complementary strengths of optical and SAR sensors at a 1-5 day temporal resolution, allowing the quantification of sub-weekly reservoir operations. Additionally, the skill of radar altimeters in the RAT framework was tested using the Jason-3 altimeter. Using in-situ data from three Thai reservoirs in the Mekong Basin, consistent improvements were observed as compared to the original RAT framework. A functionality for visualizing forecasted outflow was also added using historically inferred reservoir operations or stakeholder-driven target storage expectations.

Reservoirs↗
NASA NTRS2022

Performance Analysis of Terrain Relative Navigation Using Blue Origin New Shepard Suborbital Flight Telemetry

As part of a NASA Tipping Point Partnership with Blue Origin to mature precision lunar landing technologies, two test flights of the Blue Origin New Shepard vehicle carrying a NASA-developed sensor suite were conducted on 10/13/2020 and 08/26/2021 at the West Texas Launch Site (LS-1). Part of the acquired datasets, comprising data from an inertial measurement unit and a downward facing camera, was postprocessed through a JPL-developed prototype Visual Odometry and Map Relative Localization software (TRNVOSIM), and compared against ground truth acquired by the host vehicle navigation system. In this paper, we provide a description of the algorithms, the test setup, and the processed results.

Pedrotty, Samuel M.↗
NASA NTRS2019

Supporting automation in spacecraft activity planning with simulation and visualization

Automation is gaining momentum in spacecraft operations, however, at a much slower pace than comparable application domains. The reasons behind slow adoption is (1) the need for high reliability and (2) the limited interaction between human operators and the automated systems. For automated systems to be adopted and trusted by humans, humans need to gain intuition about the decision making process of the automated system and trust in its execution [1]. In this paper, we present how simulation and visualization can enhance adoption of an automated on-board activity scheduling system, specifically in the context of Mars2020 rover mission[2]. The visualization aims to communicate to the users degree of variance and uncertainty in possible schedule execution. Our preliminary validation results suggest that the proposed visualization increases operators’ confidence in—and likelihood of adopting—the automated scheduling system.

Chien, Steve↗
NASA NTRS1996

Covisualization by computational optical-sectioning microscopy of integrin and associated proteins at the cell membrane of living onion protoplasts

Using higher-resolution wide-field computational optical-sectioning fluorescence microscopy, the distribution of antigens recognized by antibodies against animal beta 1 integrin, fibronectin, and vitronectin has been visualized at the outer surface of enzymatically protoplasted onion epidermis cells and in depectinated cell wall fragments. On the protoplast all three antigens are colocalized in an array of small spots, as seen in raw images, in Gaussian filtered images, and in images restored by two different algorithms. Fibronectin and vitronectin but not beta 1 integrin antigenicities colocalize as puncta in comparably prepared and processed images of the wall fragments. Several control visualizations suggest considerable specifity of antibody recognition. Affinity purification of onion cell extract with the same anti-integrin used for visualization has yielded protein that separates in SDS-PAGE into two bands of about 105-110 and 115-125 kDa. These bands are again recognized by the visualization antibody, which was raised against the extracellular domain of chicken beta 1 integrin, and are also recognized by an antibody against the intracellular domain of chicken beta 1 integrin. Because beta 1 integrin is a key protein in numerous animal adhesion sites, it appears that the punctate distribution of this protein in the cell membranes of onion epidermis represents the adhesion sites long known to occur in cells of this tissue. Because vitronectin and fibronection are matrix proteins that bind to integrin in animals, the punctate occurrence of antigenically similar proteins both in the wall (matrix) and on enzymatically prepared protoplasts reinforces the concept that onion cells have adhesion sites with some similarity to certain kinds of adhesion sites in animals.

NASA Discipline Plant Biology↗
NASA NTRS1999

Integrated Computational System for Aerodynamic Steering and Visualization

In February of 1994, an effort from the Fluid Dynamics and Information Sciences Divisions at NASA Ames Research Center with McDonnel Douglas Aerospace Company and Stanford University was initiated to develop, demonstrate, validate and disseminate automated software for numerical aerodynamic simulation. The goal of the initiative was to develop a tri-discipline approach encompassing CFD, Intelligent Systems, and Automated Flow Feature Recognition to improve the utility of CFD in the design cycle. This approach would then be represented through an intelligent computational system which could accept an engineer's definition of a problem and construct an optimal and reliable CFD solution. Stanford University's role focused on developing technologies that advance visualization capabilities for analysis of CFD data, extract specific flow features useful for the design process, and compare CFD data with experimental data. During the years 1995-1997, Stanford University focused on developing techniques in the area of tensor visualization and flow feature extraction. Software libraries were created enabling feature extraction and exploration of tensor fields. As a proof of concept, a prototype system called the Integrated Computational System (ICS) was developed to demonstrate CFD design cycle. The current research effort focuses on finding a quantitative comparison of general vector fields based on topological features. Since the method relies on topological information, grid matching and vector alignment is not needed in the comparison. This is often a problem with many data comparison techniques. In addition, since only topology based information is stored and compared for each field, there is a significant compression of information that enables large databases to be quickly searched. This report will (1) briefly review the technologies developed during 1995-1997 (2) describe current technologies in the area of comparison techniques, (4) describe the theory of our new method researched during the grant year (5) summarize a few of the results and finally (6) discuss work within the last 6 months that are direct extensions from the grant.

Hesselink, Lambertus↗
NASA NTRS1990

Computational flow simulation of liquid oxygen in a SSME preburner injector element LOX post

Liquid oxygen (LOX) is simulated as an incompressible flow through a Space Shuttle main engine fuel preburner injector element LOX post for the full range of operating conditions. Axial profiles of axial velocity and static pressure are presented. For each operating condition analyzed, the minimum pressure downstream of the orifice is compared to the vapor pressure to determine if cavitation could occur. Flow visualization is provided by velocity vectors and stream function contours. The results indicate that the minimum pressure is too high for cavitation to occur. To establish confidence in the CFD analysis, the simulation is repeated with water flow through a superscaled LOX post and compared with experimental results. The agreement between calculated and experimental results is very good.

Rocker, Marvin↗
NASA NTRS2024

Lunar Terrain Mapping Using 3D Software and Modeling Techniques for the Glenn Research Center Communication Analysis Suite

As NASA prepares to return humans to the Moon as part of upcoming Artemis missions, engineers must examine the surface features and safety of lunar terrain at various locations. The Glenn Research Center Communication Analysis Suite (GCAS) includes visualization tools developed to aid scientists in this quest to comprehend lunar terrain data, as well as spatial communication information. Visual information and understanding will be highly useful to engineers as they use the GCAS to compare the topography of regions of interest for the Artemis III and future space travel missions. Not only can three-dimensional (3D) visualization display the intricacies of the lunar terrain, but it can also demonstrate relationships such as the presence or absence of communication links between Earth ground stations, lunar crew members, and rovers, and the presence of shadows on the lunar surface. In the future, the GCAS has the potential to support the planning of other space exploration missions as well. The emerging possibility of incorporating more planetary bodies becomes especially important as NASA plans not only to return to the Moon but to press onward to Mars.

Visualization↗