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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Studies of Planetary Ring Systems

We propose to extend our current cooperative agreement for another three years to continue this highly productive collaboration. The extension will provide ongoing full-time support for Stanford Research Associate Mark R. Showalter (henceforth MRS). His activities are divided into three separate but closely related activities. First, he will continue to pursue a variety of scientific problems related to the ring systems of Jupiter, Saturn, Uranus and Neptune. Second, he will continue to manage the activities of the Planetary Data System (PDS) Rings Node located at NASA Ames. Third, for at least one more year he will oversee a project to develop a software package for planetary image processing and analysis.

Showalter, Mark R.↗
NASA NTRS2000

Cover Drive and Lock Ring Mechanisms for Genesis

The Genesis payload canister will return solar wind samples to Earth. The canister contains four mechanism assemblies: the Cover Drive Mechanism, the Lock Ring Mechanism, the Array Deployment Mechanism, and the Array Latch Mechanism. The Cover Drive and Lock Ring Mechanisms are described in detail while the other two mechanisms are briefly summarized. The Engineering Model canister has been designed, built, tested, and delivered to the spacecraft. The Flight Model is currently being built with delivery to the spacecraft scheduled for mid July 2000. Launch is scheduled for January 2001

Jandura, Louise↗
NASA NTRS2000

BOREAS TE-5 Tree Ring and Carbon Isotope Ratio Data

The BOREAS TE-5 team collected several data sets to investigate the vegetation-atmosphere CO2 and H2O exchange processes. These data include tree ring widths and cellulose carbon isotope data from coniferous trees collected at the BOREAS NSA and SSA in 1993 and 1994 by the BOREAS TE-5 team. Ring width data are provided for both Picea mariana and Pinus banksiana. The carbon isotope data are provided only for Pinus banksiana. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G.↗
NASA NTRS2001

Saturn Ring Observer

Answering fundamental questions about ring particle characteristics, and individual and group behavior, appears to require close-proximity (a few km) observations. Saturn's magnificent example of a ring system offers a full range of particle sizes, densities, and behaviors for study, so it is a natural choice for such detailed investigation. Missions implementing these observations require post-approach Delta(V) of approximately 10 km/s or more, so past mission concepts called upon Nuclear Electric Propulsion. The concept described here reduces the propulsive Delta(V) requirement to as little as 3.5 km/s, difficult but not impossible for high-performance chemical propulsion systems. Additional information is contained in the original extended abstract.

Spilker, T. R.↗
NASA NTRS2001

Turbulent Flame Processes Via Diffusion Flame-Vortex Ring Interactions

Flame-vortex interactions are canonical configurations that can be used to study the underlying processes occurring in turbulent reacting flows. This configuration contains many of the fundamental aspects of the coupling between fluid dynamics and combustion that could be investigated with more controllable conditions than are possible under direct investigations of turbulent flames. Diffusion flame-vortex ring interaction contains many of the fundamental elements of flow, transport, combustion, and soot processes found in turbulent diffusion flames. Some of these elements include concentrated vorticity, entrainment and mixing, strain and nonequilibrium phenomena, diffusion and differential diffusion, partial premixing and diluent effects, soot formation and oxidation, and heat release effects. Such simplified flowfield allows the complex processes to be examined more closely and yet preserving the physical processes present in turbulent reacting flows. Furthermore, experimental results from the study of flame-vortex interactions are useful for the validation of numerical simulations and more importantly to deepen our understanding of the fundamental processes present in reacting flows. Experimental and numerical results obtained under microgravity conditions of the diffusion flame-vortex ring interaction are summarized in this paper. Results are obtained using techniques that include Flame Luminosity Imaging (FLI), Laser Soot-Mie Scattering (LSMS), Computational Fluid Dynamics and Combustion (CFDC), and Diode Laser Spectroscopy/Iterative Temperature with Assumed Chemistry (DLS/ITAC).

Dahm, Werner J. A.↗
NASA NTRS2001

High Resolution Three-Color Imaging of Spirals With Nuclear Star-Forming Rings

Nuclear rings in barred spirals offer an opportunity to study starburst properties in order to develop an understanding of the evolution of star formation in galaxies. To achieve this understanding, a large scale imaging survey in the H alpha line and in the B and I broad bands has been performed. Analysis of all galaxies that reveal nuclear rings in the H alpha line will be compared to numerical models so that the relative ages between the starforming clumps can be estimated. The luminosity function of the starforming regions will be related to the measured properties of the associated star-cluster and the required ionizing flux. Also B - I color index images will be performed to indicate the location of the dust lanes.

Mazzuca, Lisa↗
NASA NTRS2001

ALEXIS Observations of the Monogem Ring Supernova Remnant

The subject grant is for the analysis of ALEXIS observations of the Monogem Ring supernova remnant using the diffuse all-sky maps produced from the ALEXIS all-sky survey. The work is to produce ratio maps of the three energy bands provided by ALEXIS, analyze the ratio data to constrain the intervening neutral hydrogen column density and the temperature and elemental abundances of the X-ray emitting gas, compare the structure to that observed in the ROSAT maps, and incorporate the results into current supenova remnant evolution models. The work outlined above has been significantly delayed since the ALEXIS diffuse all-sky maps took longer to produce than anticipated. Unfortunately, the ALEXIS satellite suffered a failure of the Pegasus launch vehicle which left the satellite in a partially functioning condition. The attitude control system of the spacecraft was unable to operate as planned and this has greatly increased the complexity of the aspect solution. Our colleagues at Los Alamos have made progress in producing these maps and are nearing completion of the final maps. However, the quality of the data have been significantly compromised by the overall lower exposure due to the spacecraft problems and the higher background of the micro-channel plate detectors. We have compared the ALEXIS and ROSAT maps of this region of the sky and there is no obvious signal in the ALEXIS maps of the Monogem Ring. We are now exploring correlation techniques to determine if there is indeed a faint signal in the ALEXIS maps. Although, the project has been a disappointment so far, the data may still provide a valuable lower limit on the neutral hydrogen column density. This is a far cry from our original intentions, but would still be valuable science. Given the large delays in producing the ALEXIS sky maps, this work will continue past the end of the grant period.

Plucinsky, Paul↗
NASA NTRS2002

Laser Pulse-Stretching Using Multiple Optical Ring-Cavities

We describe a simple and passive nanosecond-long (ns-long) laser 'pulse-stretcher' using multiple optical ring-cavities. We present a model of the pulse-stretching process for an arbitrary number of optical ring-cavities. Using the model, we optimize the design of a pulse-stretcher for use in a spontaneous Raman scattering excitation system that avoids laser-induced plasma spark problems. From the optimized design, we then experimentally demonstrate and verify the model with a 3-cavity pulse-stretcher system that converts a 1000 mJ, 8.4 ns-long input laser pulse into an approximately 75 ns-long (FWHM) output laser pulse with a peak power reduction of 0.10X, and an 83% efficiency.

Kojima, Jun↗
NASA NTRS1947

Flight Comparison of Performance and Cooling Characteristics of Exhaust-Ejector Installation with Exhaust-Collector-Ring Installation

Flight and ground investigations have been made to compare an exhaust-ejector installation with a standard exhaust-collector-ring installation on air-cooled aircraft engines in a twin-engine airplane. The ground investigation allowed that, whereas the standard engine would have overheated above 600 horsepower, the engine with exhaust ejectors cooled at take-off operating conditions at zero ram. The exhaust ejectors provided as much cooling with cowl flaps closed as the conventional cowl flaps induced when full open at low airspeeds. The propulsive thrust of the exhaust-ejector installation was calculated to be slightly less than the thrust of the collector-ring-installation.

Acker, Loren W.↗
NASA NTRS1961

Measured Two-Dimensional Damping Effectiveness of Fuel-Sloshing Baffles applied to Ring Baffles in Cylindrical Tanks

Measured two-dimensional damping forces of baffles with various shapes and perforations are presented for fluid conditions representative of those in liquid-fuel rocket vehicles. The effect of amplitude and frequency of fuel sloshing, and surface proximity on baffle damping are shown. Application of the result sin the prediction of damping effectiveness of ring baffles in cylindrical tanks is demonstrated. Finally, some measurements of damping in a free-free cylindrical tank are presented which verify the predictions based on two-dimensional results. Measurements of certain three-dimensional baffles show that they provide greater damping than ring baffles.

Cole, Henry A., Jr.↗
NASA NTRS2004

Magnetosphere-Ionosphere Coupling and Associated Ring Current Energization Processes

Adiabatic processes in the ring current are examined. In particular, an analysis of the factors that parameterize the net adiabatic energy gain in the inner magnetosphere during magnetic storms is presented. A single storm was considered, that of April 17, 2002. Three simulations were conducted with similar boundary conditions but with different electric field descriptions. It is concluded that the best parameter for quantifying the net adiabatic energy gain in the inner magnetosphere during storms is the instantaneous value of the product of the maximum westward electric field at the outer simulation boundary with the nightside plasma sheet density. However, all of the instantaneous magnetospheric quantities considered in this study produced large correlation coefficients. Therefore, they all could be considered useful predictors of the net adiabatic energy gain of the ring current. Long integration times over the parameters lessen the significance of the correlation. Finally, some significant differences exist in the correlation coefficients depending on the electric field description.

Liemohn, M. W.↗
NASA NTRS2006

Self-Consistent Ring Current Modeling with Propagating Electromagnetic Ion Cyclotron Waves in the Presence of Heavy Ions

The self-consistent treatment of the RC ion dynamics and EMIC waves, which are thought to exert important influences on the ion dynamical evolution, is an important missing element in our understanding of the storm-and recovery-time ring current evolution. Under certain conditions, relativistic electrons, with energies 21 MeV, can be removed from the outer radiation belt by EMIC wave scattering during a magnetic storm. That is why the modeling of EMIC waves is critical and timely issue in magnetospheric physics. To describe the RC evolution itself this study uses the ring current-atmosphere interaction model (RAM). RAM solves the gyration and bounce-averaged Boltzmann-Landau equation inside of geosynchronous orbit. Originally developed at the University of Michigan, there are now several branches of this model currently in use as describe by Liemohn namely those at NASA Goddard Space Flight Center This study will generalize the self-consistent theoretical description of RC ions and EMIC waves that has been developed by Khazanov and include the heavy ions and propagation effects of EMIC waves in the global dynamic of self-consistent RC - EMIC waves coupling. The results of our newly developed model that will be presented at GEM meeting, focusing mainly on the dynamic of EMIC waves and comparison of these results with the previous global RC modeling studies devoted to EMIC waves formation. We also discuss RC ion precipitations and wave induced thermal electron fluxes into the ionosphere.

Khazanov, George V.↗
NASA NTRS1980

Ring connection for porous combustor wall panels

A gas turbine engine combustor assembly of unique configuration has an outer wall made up of a plurality of axially extending multi-layered porous metal panels joined together at butt joints therebetween by a reinforcing and heat dissipation ring and a unique weld configuration to prevent thermal erosion of the ends of the porous metal panels at the butt joints; the combustor further including a unique inner wall made up of a plurality of like axially extending multi-layered porous metal panels joined at butt joints by a reinforcing and heat dissipation ring on the inner surface of the inner wall panels and an improved butt weld joint that prevents thermal erosion of the ends of the porous metal inner wall panels.

Verdouw, Albert J.↗
NASA NTRS2008

Ring Bus Architecture for a Solid-State Recorder

A document concisely describes a ring bus architecture for a proposed solid-state recorder (SSR) that would serve as buffer of data to be transmitted from a spacecraft to Earth. This architecture would afford fault tolerance needed for reliable operation in an anticipated high-radiation environment in which traditional SSRs cannot operate reliably. Features of the architecture include one or more controller boards and multiple memory boards interconnected in a ringlike topology. The interconnections would be high-speed serial links complying with the Institute of Electrical and Electronics Engineers (IEEE) standard 1393 (which pertains to a spaceborne fiber-optic data bus). Accordingly, each controller and memory board would be equipped with an IEEE-1393-compliant ring-bus-interface unit. The ringlike topology and the multiplicity of memory boards (and, optionally, of controller boards) would afford the redundancy needed for fault tolerance. Each board would be a fault-containment region. The IEEE 1393 links could be routed so that the SSR would continue to function even in the event of multiple failures. This architecture would also support scalability over a wide range. In a fully redundant configuration, it could accommodate between 1 and 125 memory boards.

Walker, W. John↗
NASA NTRS2007

Short-Term Forecasting of Radiation Belt and Ring Current

A computer program implements a mathematical model of the radiation-belt and ring-current plasmas resulting from interactions between the solar wind and the Earth s magnetic field, for the purpose of predicting fluxes of energetic electrons (10 keV to 5 MeV) and protons (10 keV to 1 MeV), which are hazardous to humans and spacecraft. Given solar-wind and interplanetary-magnetic-field data as inputs, the program solves the convection-diffusion equations of plasma distribution functions in the range of 2 to 10 Earth radii. Phenomena represented in the model include particle drifts resulting from the gradient and curvature of the magnetic field; electric fields associated with the rotation of the Earth, convection, and temporal variation of the magnetic field; and losses along particle-drift paths. The model can readily accommodate new magnetic- and electric-field submodels and new information regarding physical processes that drive the radiation-belt and ring-current plasmas. Despite the complexity of the model, the program can be run in real time on ordinary computers. At present, the program can calculate present electron and proton fluxes; after further development, it should be able to predict the fluxes 24 hours in advance

Fok, Mei-Ching↗
NASA NTRS2007

Ring-Resonator/Sol-Gel Interferometric Immunosensor

A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

Bearman, Gregory↗
NASA NTRS2010

Discontinuous Inter-Granular Separations (DIGS) in the Gas Nitride Layer of ISS Race Rings

The starboard solar alpha rotary joint (SARJ) race ring on the International space station (ISS) failed due to severe spalling of the outer diameter, 45 degree (outer canted) nitrided surface. Subsequent analysis at NASA-KSC revealed that almost all of the debris generated due to the failure was nitrided 15-5 stainless steel. Subsequent analysis of the nitride control coupons (NCC) at NASA-JSC revealed the presence of discontinuous inter-granular separations (DIGS) in the gas nitride layer. These DIGS were present in the inter-granular networking located in the top 2 mils of the nitride layer. The manufacturer's specification requires the maximum white structure to be 0.0003 inches and intergranular networking below the allowable white structure depth to be cause for rejection; a requirement that the NCCs did not meet. Subsequent testing and analysis revealed that lower DIGS content significantly lowered the probability of nitride spalling in simulated, dry condition runs. One batch of nitride samples with DIGS content similar to the port SARJ (did not fail on orbit) which exhibited almost no nitride spalling after being run on one test rig. Another batch of nitride samples with DIGS content levels similar to the starboard SARJ exhibited significant nitride spalling on the same test rig with the same load under dry conditions. Although DIGS were not the root cause of starboard race ring failure, testing indicates that increased DIGS reduced the robustness of the gas nitride layer under dry operating conditions.

Figert, John↗
NASA NTRS2006

Protein Sensors Based on Optical Ring Resonators

Prototype transducers based on integrated optical ring resonators have been demonstrated to be useful for detecting the protein avidin in extremely dilute solutions. In an experiment, one of the transducers proved to be capable of indicating the presence of avidin at a concentration of as little as 300 pM in a buffer solution a detection sensitivity comparable to that achievable by previously reported protein-detection techniques. These transducers are serving as models for the further development of integrated-optics sensors for detecting small quantities of other proteins and protein-like substances. The basic principle of these transducers was described in Chemical Sensors Based on Optical Ring Resonators (NPO-40601), NASA Tech Briefs, Vol. 29, No. 10 (October 2005), page 32. The differences between the present transducers and the ones described in the cited prior article lie in details of implementation of the basic principle. As before, the resonator in a transducer of the present type is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, consists of a layer comprising sublayers having indices of refraction lower than that of the waveguide core. The outermost sublayer absorbs the chemical of interest (in this case, avidin). The index of refraction of the outermost sublayer changes with the concentration of absorbed avidin. The resonator is designed to operate with relatively strong evanescent-wave coupling between the outer sublayer and the electromagnetic field propagating along the waveguide core. By virtue of this coupling, the chemically induced change in the index of refraction of the outermost sublayer causes a measurable change in the spectrum of the resonator output.

Lin, Ying↗