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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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The current state of knowledge of Saturn's rings is reviewed. A brief historical introduction is given, followed by a discussion of the radial profile of the rings, ring dynamics, features without azimuthal symmetry, ring particle size distribution, and the physical properties of ring particles. The direction for future analysis and observation is considered.
A numerical model for the three-dimensional thermal analysis of rocket thrust chambers and nozzles has been developed. The input to the model consists of the composition of the fuel/oxidant mixture and flow rates, chamber pressure, coolant entrance temperature and pressure, dimensions of the engine, materials and the number of nodes in different parts of the engine. The model allows for temperature variation in three dimensions: axial, radial and circumferential directions and by implementing an iterative scheme, it provides nodal temperature distribution, rates of heat transfer, hot gas and coolant thermal and transport properties.
A numerical model for the three dimensional thermal analysis of rocket thrust chambers and nozzles has been developed. The input to the model consists of the composition of the fuel/oxidant mixture and flow rates, chamber pressure, coolant entrance temperature and pressure, dimensions of the engine, materials and the number of nodes in different parts of the engine. The model allows for temperature variation in three dimensions: axial, radial and circumferential directions and by implementing an iterative scheme, it provides nodal temperature distribution, rates of heat transfer, hot gas and coolant thermal and transport properties.
We have recently reexamined more than 9000 United States previously unidentified seismic events catalogued during the Apollo landing missions and positively identified for the first time about 30 deep moonquake nests on the far side of the Moon. Although only a few of them are currently locatable, the relative arrival times among stations for the rest and presence or absence of seismic signals at particular stations suggest that either (a) the region within about $40\deg$ of the antipode is aseismic or (b) the deep interior of the Moon severely attenuates or deflects seismic waves. Aside from the obvious question of how to distinguish between such hypothetical models, this effort raised several more general questions concerning the use of deep moonquake signals to infer the structure and dynamics of the deep interior of the Moon. Among more important ones are: (1) How reliable are the seismic arrival picks from which to compute the seismic velocity variations in the Moon? (2) How do the possible lateral variations in seismic velocity affect the computed radial variation in seismic velocity at depth? (3) Can we tell more about the distribution and mechanism of deep moonquakes from the newly expanded database of identified deep moonquakes? Questions (1) and (2) are especially important because the inferred deep internal structure of the Moon depends critically on their answers. Answering these questions may demand additional data collected on future lunar missions, but some may be resolved with further examination of the existing data.
Two documents describe a prototype system of electrometers for measuring electrostatic fields and electrostatic responses of soils on Mars and the Moon. The electrodes of this electrometer are embedded in a wheel of an exploratory robotic vehicle, utilizing the wheel motion to bring the electrodes into proximity or contact with the soil. Each electrode resides in one of two types of sensor modules: electric-field (ELF) or triboelectric (TRIBO). In either type, what is measured is simply the electric charge induced on the electrode by exposure to the external distribution of electrostatic charge. In an ELF module, the electrode is bare and recessed radially from the wheel surface. The ELF sensor provides a measure of the charge on a small patch of undisturbed soil as the wheel rolls forward. In a TRIBO module, the electrode is only slightly recessed and covered with a polymeric insulator flush with the wheel surface. Through contact electrification, the insulator exchanges charge with the soil. There are five TRIBO sensors, each containing an insulator made of a different polymer. The charge data gathered by the five TRIBO sensors can be used to determine how the soil fits into a triboelectric series.
Model calculations are reported for the Iogenic plasma source created by atomic oxygen and sulfur above Io's exobase in the corona and extended clouds (Outer Region). On a circumplanetary scale, two-dimensional distributions produced by integrating the proper three dimensional rate information for electron impact and charge exchange processes along the magnetic field lines are presented for the pickup ion rates, the net-mass and total-mass loading rates, the mass per unit magnetic flux rate, the pickup conductivity, the radial pickup current, and the net-energy loading rate for the plasma torus. All of the two-dimensional distributions are highly peaked at Io's location and hence highly asymmetric about Jupiter. The Iogenic plasma source is also calculated on a much smaller near-Io scale to investigate the structure of the highly peak rates centered about lo's instantaneous location. The Iogenic plasma source for the Inner Region (pickup rates produced below Io's exobase) is, however, expected to be the dominant source near lo for the formation of the plasma torus ribbon and to be a comparable source, if not a larger contributor, to the energy budget of the plasma torus, so as to provide the necessary power to sustain the plasma torus radiative loss rate.
This paper presents water content and particle measurements from the second Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The water content measurements came from the Science Engineering Associates Multi-Element Probe and the Isokinetic Probe whereas the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments measured the particle size distribution. Ice particle accretion due to the ingestion of ice-crystals is attributed to numerous jet engine powerloss events. The NASA PSL is an altitude jet-engine test facility which has recently added a capability to inject ice particles into the flow. This work focuses on characterizing the icing cloud by traversing the instruments across the test section at four different conditions where velocity and water content were varied. For this test, the nozzle patterns were selected to make a uniform cloud in the center 6-inch diameter of the test section. Radial trends for the ice and water content measurements are presented and the melt ratio is calculated at the measurement locations. Particle size distributions are also presented. The measured water content, melt ratio, and particle size decreased moving out radially. Measured water content trends show uniformity to within 19.2% for the center 6 inches of the cloud, as intended. In addition, the total water content increased at centerline with velocity, whereas the melt ratio decreased.
This paper presents water content and particle measurements from the second Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The water content measurements came from the Science Engineering Associates Multi-Element Probe and the Isokinetic Probe whereas the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments measured the particle size distribution. Ice particle accretion due to the ingestion of ice-crystals is attributed to numerous jet engine powerloss events. The NASA PSL is an altitude jet-engine test facility which has recently added a capability to inject ice particles into the flow. This work focuses on characterizing the icing cloud by traversing the instruments across the test section at four different conditions where velocity and water content were varied. For this test, the nozzle patterns were selected to make a uniform cloud in the center 6-inch diameter of the test section. Radial trends for the ice and water content measurements are presented and the melt ratio is calculated at the measurement locations. Particle size distributions are also presented. The measured water content, melt ratio, and particle size decreased moving out radially. Measured water content trends show uniformity to within 19.2% for the center 6 inches of the cloud, as intended. In addition, the total water content increased at centerline with velocity, whereas the melt ratio decreased.
Attention is given to a research project which has the goal to develop a two-stage slagging gasifier-combustor in the form of a high-intensity combustor, taking into account a suitable aerodynamic design of the second stage nozzle which will prevent the separation of the boundary layer as the flow turns from axial to radial direction. The specific objectives of the present investigation are to test the effect of various second-stage nozzle geometries, flow rates, swirl number, and distribution in the first and second stages upon the corresponding flowfield in the second stage. Special emphasis is given to the avoidance of boundary layer separation as the flow turns from axial to radial direction into the MHD disk generator.
A new half-range differential approximation for radiative transfer with spherical symmetry is presented. The development is motivated by the various failures of existing differential approximations in determining emissive-power distributions and heat transfer for concentric-spheres problems. The new approach represents a modification of the four-moment double spherical-harmonics method, to which it reduces in the planar limit. The difference is effected by relocating the discontinuity of the assumed directional distribution of radiation intensity. The shift takes the discontinuity from precisely on the division between radially inward and radially outward, to just within the radially-outward directional half range. The method is tested on a variety of concentric spheres problems with and without internal heat sources, reproducing all the important features of the exact results.
The paper investigates the influence of crater latitude, target material, and elevation on the morphology of the ejecta facies and crater interiors as a function of crater diameter. It is shown that only pancake craters exhibit latitudinal variation in their distribution. It is also shown that several crater types are associated with specific target materials: radial textured craters are found primarily on Tharsis and Elysium lavas, and pancake craters are found on fractured terrain, old lavas, and channel materials. Craters formed on recent lavas more frequently possess secondary craters, central peaks, and terraces than primary craters found on other geological units. The maximum radial extent of fluidized ejecta is demonstrated to be a function of crater altitude and latitude.
The error sensitivity of orbit calculations in support of the NASA Ocean Surface Topography Mapping Experiment (TOPEX), which require an accuracy on the order of 5 cm, is investigated. The contributions of errors in the gravitational, atmospheric drag and solar radiation pressure models to the computed orbit are analyzed for the cases of an ideal data distribution and realistic laser ranging data coverage. It is found that the major contributor to radial orbital error is the error in the geopotential model, accounting for orbital errors of 30 to 70 cm, with the effects of solar radiation pressure, drag modeling, tracking station coordinate errors making lesser contributions. It is concluded that TOPEX accuracy goals cannot be met using ground-based laser ranging data without improving the geopotential model.
Such nonthermal features as temperature anisotropies, heat fluxes, and proton double streams have been observed by a Helios solar probe survey of solar wind three-dimensional proton velocity distributions between 0.3 and 1 AU. It is found that a strong anisotropy in the core of proton distributions, with a temperature that is larger perpendicular rather than parallel to the magnetic field, is a persistent feature of high-speed streams, becoming most pronounced in the perihelion, or about 0.3 AU. Isotropic distributions have been detected only close to, and at, magnetic sector boundaries, and the flattest radial temperature profiles are found in high-speed streams. These observations indicate that local heating or proton heat conduction occurs in the solar wind.
The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.
Four separate but related studies of coronal magnetostatic equilibria under a variety of boundary conditions and distributions of coronal current are reviewed. Physically, all four studies assume an axisymmetric corona whose radial magnetic field at the coronal base is dipolar. Electric currents in the model coronas are assumed to flow in the azimuthal direction, giving rise to Lorentz forces that must be balanced by pressure gradients and gravity. Mathematically, such coronas are described by the equation of magnetostatic force balance and Ampere's law. Although highly idealized, the axisymmetric magnetostatic models described provide insights into the behavior of a variety of coronal structures. The models show how more realistic current sheet boundary conditions and coronal density variations may be modeled.
The relative roles of star formation and viscously-induced radial flows in galactic disks are discussed. It is shown that the present-day distributions of stars, gas, and metals in galactic spirals need not reflect initial conditions but may instead indicate a cooperation between star forming and viscous processes over the disk lifetime.
The present study investigates the effects of compressibility on free (unsteady) viscous heat-conducting vortices. Analytical solutions are found in the limit of large but finite Reynolds number and small but finite Mach number. It is shown that the spreading of the vortex causes a radial flow. This flow is given by the solution of an ordinary differential equation, which gives the dependence of the radial velocity on the tangential velocity, density, and temperature profiles of the vortex. Estimates of the radial velocity found by solving this equation are found to be in good agreement with numerical solutions of the full equations. The equations for the viscous evolution are expanded in powers of Mach number to obtain detailed analytical solutions. It is shown that swirling axisymmetric compressible flows generate negative radial velocities far from the vortex core owing to viscous effects, regardless of the initial distributions of vorticity, density, and entropy.
In order to permit quantitative studies of the diffuse cosmic X-ray background and of extended X-ray sources, the particle induced background of the Roentgen Satellite, Rosat, Position Sensitive Proportional Counter (PSPC) is parameterized. Data collected during 210,000 s of PSPC operation have been analyzed and the temporal, spectral, and spatial distributions investigated. About 77 percent of the residual events originate within the detector while the remainder enter through the counter window. During typical conditions, the count rate of the residual events is well correlated with the Master Veto (MV) count rate. The spectrum of these events is well described by a flat component plus a soft power law and an Al K-alpha line at 1.5 keV. Also during typical conditions, the ratio between the power law and flat components remains constant to +/- 4 while the relative Al K-alpha contribution increases with increasing MV count rate. The distribution of the counts over the field of view is uniform except for a slight radial dependence and shadowing caused by blockage of the externally produced component by the window support structure.