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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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FORTRAN 4 program for calculating dynamic Kirchhoff deformation of structural rings subjected to fragment impact
Ionospheric research covering electron and ion distributions, ion chemistry, neutral atmosphere interactions, thermal structure, electrodynamics, etc
The problem of representing groups of loosely connected processes is investigated, and a model for process representation useful for synthesizing complex patterns of process behavior is developed. There are three parts, the first part isolates the concepts which form the basis for the process representation model by focusing on questions such as: What is a process; What is an event; Should one process be able to restrict the capabilities of another? The second part develops a model for process representation which captures the concepts and intuitions developed in the first part. The model presented is able to describe both the internal structure of individual processes and the interface structure between interacting processes. Much of the model's descriptive power derives from its use of the notion of process state as a vehicle for relating the internal and external aspects of process behavior. The third part demonstrates by example that the model for process representation is a useful one for synthesizing process behavior patterns. In it the model is used to define a variety of interesting process behavior patterns. The dissertation closes by suggesting how the model could be used as a semantic base for a very potent language extension facility.
Theoretical and experimental research on structural-acoustic interaction is reviewed. The emphasis is upon the radiation from and acoustic loading of baffled rectangular plates and membranes. The topics discussed include a criterion for strong radiation loading, the mass law for a finite panel, numerical calculation of the radiation impedance of a finite panel in the presence of a parallel mean flow, and experimental determination of the effect of vibration amplitude and Mach number upon panel radiation efficiency.
A number of models which would explain ocean wave imagery taken with a synthetic aperture imaging radar are analyzed analytically and numerically. Actual radar imagery is used to support some conclusions. The models considered correspond to three sources of radar backscatter cross section modulation: tilt modulation, roughness variation, and the wave orbital velocity. The effect of the temporal changes of the surface structure, parametric interactions, and the resulting distortions are discussed.
For abstract, see N78-25123.
A method of measuring the atmospheric conduction current above the ground has been employed to obtain data for 12 weeks during the first half of 1974. The instrument consists of a split aluminum sphere suspended by insulated wires to a wooden frame. The measuring electronics and the transmitter are enclosed within the spherical structure. The interaction of the instrument with its atmospheric electrical environment is analyzed, and it is shown that in steady state conditions, predictable differences in the instrumentally measured currents and the atmospheric conduction current will be less than 5% and in the nonsteady state situations the difference is less than 20%. Diurnal variations, a probable winter-summer variation, sunrise, and fog effects were observed for the data obtained during fair-weather conditions. Disturbed weather data are interpreted for the effects of low clouds on the atmospheric current. The charge concentrations within overcast clouds sufficient to produce the observed reversed atmospheric currents are estimated to be small in relation to values in thunderclouds.
Additions made to the original version of the DISCOS computer programs are presented. They include demonstrations of problems and improved capabilities. Remarks are made pertaining new subroutines.
Reference lists of approximately 900 published Langley Research Center reports in various areas of acoustics and noise control for the period 1940-1979 are presented. Specific topic areas covered include: duct acoustics; propagation and operations; rotating blade noise; jet noise; sonic boom; flow surface interaction noise; structural response/interior noise; human response; and noise prediction.
The requirements for the design of a large space structure which will be deployed, erected, assembled or fabricated in space are delineated in terms of operational loads, stiffness requirements, structure-control interaction, deformations, precision requirements and member slenderness. Design examples for a truss antenna reflector, interorbit propulsion loads and free-flying solar reflectors are given. It is concluded that the demand for dimensional accuracy and stability form the primary requirements.
It is suggested that a comparison of the periodicities inferred from spectroscopic and photometric observations of SS433 may help clarify its structure. The interaction between the orbital and beam motions may produce sideband periods in the photometry. It is found that Lense-Thirring and slaved disk models make differing predictions.
A porous plate burner system for studying the structure and interaction of diffusion flames from adjacent unlike sources of oxidizer to simulate the behavior of solid propellant flames is presented. The passage of oxidizer gases through ports of determined diameters represents decomposing oxidizer crystals, and are adjustable for various oxidizer/fuel ratio experiments. Tests with air, ethane, oxygen, and oxygen-air mixtures are described, with parameters of flow rate, oxygen/fuel ratio, and pressure. Coarse ports are found to be oxidizer rich, while fine ports are stoichiometric. More heat feedback is found with fine ports, indicating that fine particle propellant systems burn faster unless fuel allocation is such that the reduced temperature overcomes the reduced diffusion length. Further observations on the interactions of flames are reported.
In order to effectively incorporate MINIVER into the AVID system, several changes to MINIVER were made. The thermal conduction options in MINIVER were removed and a new Explicit Interactive Thermal Structures (EXITS) code was developed. Many upgrades to the MINIVER code were made and a new Langley version of MINIVER called LANMIN was created. A user input guide for LANMIN is provided.
Slips and casting are considered in terms of physical and colloidal chemistry. Casting slips are polydisperse suspensions of lyophobic particles in water, whose degree of coagulation is controlled by interaction of flocculating and deflocculating agents. Slip casting rate and viscosity are functions of temperature. Slip rheology and response to deflocculating agents varies significantly as the kinds and amounts of colloid modifiers change. Water is considered as a raw material. Various concepts of water/clay interactions and structures are discussed. Casting is a de-watering operation in which water moves from slip to cast to mold in response to a potential energy termed moisture stress. Drying is an evaporative process from a free water surface.
NASA large space structures efforts to date aimed towards large, flexible antenna-like structures (30-100M) with relatively long wavelengths (1-30cm) and moderate disturbances leading to some structure-control interaction. Potential missions in the OPTICS regime require small reflectors/mirrors, short wavelengths (visible to 100 microns), very tight tolerances in surface, alignment, pointing stability, as well as the potential of considerable on-board disturbances. For optics systems: figure/surface control can be quasi-static, active/passive isolation schemes are possible, vibration control is necessary, and the attitude control system can be low BW - Ground testing of reflectors and mirrors is more feasible than with antennas.
The capability of a unique Airborne Doppler Lidar System to measure the horizontal winds in the vicinity of severe storm activity is demonstrated. The Airborne Doppler Lidar System (ADLS), developed at NASA/MSFC, was flown on a CV990 research aircraft during the CCOPE (Cooperative Convective Precipitation Experiments, Montana, Summer 1981). Flown between 400 and 600 m AGL, the lidar probed the subcloud regions of several deep convection storms. ADLS data collected near storms on 21 and 23 July 1981 are presented along with satellite imagery, radar echo maps and surface station measurements. These case studies are evidence of the successful performance of an airborne remote wind sensing system and the advantages of two dimension flow visualization of storm outflow structures and interactions.
Voyager photographic data are used for microscopic and macroscopic analyses of the dynamics of the Saturn rings. Attention is given to particle collisions, local velocity dispersion, the particle size distribution, mechanisms governing the ring structure and interactive effects with Saturn satellite orbits. The mechanical properties and collision dynamics of the particles are discussed, along with models for perturbed and unperturbed disks. The forces involved and true scale of particle erosion are considered, as are instabilities in the rings, satellite torques, resonances, and the time scale for the evolution of the satellite orbits. Finally, the possibility that angular momentum exchanges are occurring between individual rings and satellite orbits is examined.
A hybrid numerical scheme, combined with a scalar convection scheme, is used to compute turbulent mixing layers. The hybrid scheme is used to solve the vorticity equation by dividing the domain into two regions, applying a Lagrangian method in one region and an Eulerian method in the other. The scalar convection scheme is used to track an interface which separates a dyed fluid from a dye-free fluid, thereby distinguishing the fluid that starts on the high speed side from the fluid that starts on the low speed side. A two-dimensional mixing layer has been simulated using this new method; the roll up of a vortex sheet into structures that interact and pair is observed. The growth of the momentum thickness and the development of the mean turbulence statistics are found to be consistent with experimental observations. Forcing of the layer at moderate and low frequencies shows a dramatic effect on the growth of the momentum thickness and the entrainment ratio. Low frequency forcing enhances the growth of the layer; moderate frequency forcing inhibits the growth.