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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Tethers Open New Space Options

The fundamentals of tether action are discussed with focus on the forces acting on tethered masses and a tethered satellite system being developed for deployment from the space shuttle is examined. The static, dynamic, and electric properties of the tether can be exploited for use in the long term observation of phenomena of the lower troposphere; as a space based wind tunnel; to generate high electrodynamic power; to provide desirable gravity for the space station; to dock orbit transfer vehicles with the space station; and to form a constellation of space platforms tied to the space station. Italy is responsible for building and integrating the satellite. NASA is involved in building the deployer and integrating the tethered satellite system with the space shuttle.

Bekey, I.↗
NASA NTRS1984

An open-ended future: In defense of a new humanism

The edge between technology and humanism is discussed. Advances in biology, in medicine, energy technology, tools and weapons, communications, psychology, problem solving and information storage, transportation, and other fields are presented. Ecology in self-transcendence and space travel as a survival tool are considered.

Vonputtkamer, J.↗
NASA NTRS1985

Enhancement of the flexible spacecraft dynamics program for open spacecraft

The modifications and additions made to the Flexible Spacecraft Dynamics (FSD) Program are described. The principal addition to the program was the capability to simulate a single axis gimble platform nadir pointing despin control system. The formulation for the single axis gimble equations of motion is a modification of the formulation. The details of the modifications made to the FSD Program are presented. Modifications to existing subroutines are briefly described and a detailed description of new subroutines is given. In addition, e program variables in new labelled COMMON blocks are described in detail. A description of new input symbols for the FSD Program is given.

Source record↗
NASA NTRS1985

Effect of solar-cell junction geometry on open-circuit voltage

Simple analytical models have been found that adequately describe the voltage behavior of both the stripe junction and dot junction grating cells as a function of junction area. While the voltage in the former case is found to be insensitive to junction area reduction, significant voltage increases are shown to be possible for the dot junction cell. With regard to cells in which the junction area has been increased in a quest for better performance, it was found that (1) texturation does not affect the average saturation current density J0, indicating that the texturation process is equivalent to a simple extension of junction area by a factor of square root of 3 and (2) the vertical junction cell geometry produces a sizable decrease in J0 that, unfortunately, is more than offset by the effects of attendant areal increases.

Weizer, V. G.↗
NASA NTRS1984

The electromagnetic field for an open magnetosphere

The boundary-layer-dominated models of the earth EM field developed by Heikkila (1975, 1978, 1982, and 1983) and Heikkila et al. (1979) to account for deficiencies in the electric-field descriptions of quasi-steady-state magnetic-field-reconnection models (such as that of Cowley, 1980) are characterized, reviewing the arguments and indicating the most important implications. The mechanisms of boundary-layer formation and field direction reversal are explained and illustrated with diagrams, and it is inferred that boundary-layer phenomena rather than magnetic reconnection may be the cause of large-scale magnetospheric circulation, convection, plasma-sheet formation and sunward convection, and auroras, the boundary layer acting basically as a viscous process mediating solar-wind/magnetosphere interactions.

Heikkila, W. J.↗
NASA NTRS1985

Opening of the magnetic field lines in a fast rotating magnetosphere, with an application to Jupiter

A simple model of a magnetosphere rotating around a rotating Jupiter-like object with a spin-aligned dipolar moment mu is considered. A low-energy plasma is released by inner sources located beyond the corotation radius and is diffused outward through closed lines. The lines form a closed thin equatorial disk, maintaining a quasi-static balance between the centrifugal force and the magnetic tension. Solutions are obtained for the analytical equations characterizing the plasma in the closed region; the structure of the magnetic field outside the disk; and the self-consistent value of the critical radius r sub zero. The analytical solutions are compared to the observed properties of the Jovian magnetosphere, and the results are discussed in detail.

Aly, J. J.↗
NASA NTRS1985

Definition phase for thermal ion dynamics experiment for OPEN

The Thermal Ion Dynamics Experiment (TIDE) combines differential measurements of angle, energy, and mass to determine the detailed distribution function of low energy magnetospheric ions in the range of 0 to 100 eV. Goals included designing a 1 sq cm entrance aperture, minimizing trajectory divergence at exist aperture, and minimizing internal scattering. Design parameters were used to construct the test model.

Sharp, W. E.↗
NASA NTRS1986

Shuttle Continuous Open Wind Tunnel (SCOWT)

The aerodynamic and heat transfer coefficients are studied within the range of thermo-fluid-dynamic conditions experienced by a satellite during Tethered Satellite System (TSS) atmospheric flights. The gasdynamic processes occuring downstream of the bow wave standing in front of the satellite are also studied. The knowledge of the chemistry and physics of the upper atmosphere related to satellite aerothermodynamics is furthered. The existence of an overshooting of the air drag coefficient of the sphere in the transition regime is validated. A complete set of measurements is performed in order to provide the data base to develop and validate theoretical models of free molecule transition flow fields.

Carlomagno, G. M.↗
NASA NTRS1986

Open system magnetic evolution of the taos plateau volcanic field, Northern New Mexico. I - The petrology and geochemistry of the servilleta basalt

MULTIFIT, an embodiment of the conceptual structure needed in modeling multisource and multiprocess magmatic systems, is described. This program, which uses familiar materials balance methodology and the equilibrium form of the Rayleigh equations, links evolutionary arrays, which is turn collectively relate the starting and final compositions of a given magmatic system. Moreover, MULTIFIT incorporates variations within major element data arrays; the linkage between them can be tested using an extension of the least squares algorithm, which selects the best branch point according to the minimum-sum-of-squared-residuals criterion. Advantages and disadvantages of the materials balance approach used in this program are discussed, an example is provided, and equations utilized by MULTIFIT are summarized. While MULTIFIT may not be the best approach for poorly constrained models involving partial melting for complex mixing, it may ultimately prove useful for ascertaining trace element partition coefficients in magnetic systems.

Dungan, M. A.↗
NASA NTRS1986

Modal characteristics of a stiffened composite cylinder with open and closed end conditions

The structural and acoustic modal frequencies and the loss factors of a composite fuselage model under free-free end and support-end conditions are evaluated. The fuselage model is a composite filament wound, cylindrical structure composed of carbon fibers embedded in an epoxy resin and has a ply orientation of +,-45, +,-32, 0, -,+32, and -,+45. A computer aided test system was utilized to obtain resonance frequencies, modal damping, and mode shape coefficients. Sound pressure and phase survey data are utilized to estimate acoustic modal freuencies and reverberation time was measured to calculate the acoustic loss factors. The derived structural and acoustic modal parameters are compared to analytical data from a computer prediction model. The data reveal that the acoustic modal frequencies and mode shape correlate well with predicted data, and there is fair agreement between structural modal frequencies and mode shape for the two data sets.

Grosveld, F. W.↗
NASA NTRS1986

The extinction law in the open cluster NGC 457 and the intrinsic energy distribution of Phi Cassiopeiae (F0 Ia)

Five early B-type stars near the main-sequence turnoff in NGC 457 have been observed at low dispersion with the short-wavelength prime and the long-wavelength redundant cameras of the IUE satellite. The equivalent widths of spectral features that are particularly strong and sensitive to temperature and luminosity were computed in the cluster stars and in 20 lightly reddened stars of types O9-B3 and luminosity classes III-V. The comparison of the equivalent widths provides a reliable method for finding matching pairs. Having identified the best comparison star for each program star, binned fluxes were used to determine the mean extinction curve. In order to cover the visible region, monochromatic fluxes of Phi Cas were derived from observations with the intensified Reticon scanner mounted on the No. 2 0.9 m telescope of KPNO, and they were dereddened with the mean extinction curve of Savage and Mathis. Thus, the intrinsic energy distribution of Phi Cas were determined from 1500 to 5800 A for use in a detailed model-atmosphere analysis.

Rosenzweig, P.↗
NASA NTRS1987

Opening up to the future in space with nuclear power

The relationship between the exploration of space and the availability of abundant power supplies is discussed. It is proposed that nuclear power will be needed to satisfy the power demands of manufacturing facilities in LEO, and power demands for the year 2000 are projected to be 300 KW(e). The capabilities and development of the Space Station are described; the use of nuclear power for the Station and various reactor location configurations are studied. The power requirements that will be necessary for the development of lunar resource bases and the exploration of Mars and other planets are considered; the advantages of nuclear power are examined.

Buden, David↗
NASA NTRS1986

A review of modelling techniques for the open and closed-loop dynamics of large space systems

This paper reviews the steps in the development of mathematical models that can be used to simulate the in-orbit dynamic behavior of large flexible systems. A general continuum formulation is compared with the hybrid coordinate formulation and also a finite element representation of the total system. A review of structural analysis routines emphasizes the use of computer generated graphics to help understand the different modal elastic shape functions of complex systems. Numerical techniques employed to synthesize shape and attitude control laws are summarized. Finally, the modeling of environmental disturbance torques due to the interaction of solar radiation pressure on vibrating and thermally deflected systems is discussed.

Bainum, Peter M.↗
NASA NTRS1987

Rays versus modes - Pictorial display of energy flow in an open-ended waveguide

The problem of a plane wave impinging on a semiinfinite parallel-plate waveguide is investigated. It is demonstrated that, for waveguide separation large compared to the wavelength, the fields inside the waveguide obey a single ray optics description. The beam behavior persists for more than 1000 lambda into a 50 lambda waveguide. For a small 3 lambda waveguide, the beam picture begins to blur approximately 5 lambda into the guide.

Ling, Hao↗
NASA NTRS1987

The acceleration of winds by MHD waves in open magnetic structures

It has become increasingly clear in recent years that the available models describing the acceleration of high speed streams in solar coronal holes are inadequate. Thermal models do not result in winds with the proper thermal speed and density. In addition models which assume acceleration by Alfven waves, though promising, are not self-consistent when applied low in coronal holes where the acceleration of the wind takes place. An Alfven wave in the corona with a period of a few hundred seconds will have a wavelength of the order of 10 cm. This is of the order of the diameter of a coronal hole in the low corona, and therefore it is expected that the MHD waves are guided in some sense by the coronal hole in which they propagate. This basic idea led to the development of a leaky waveguide theory to describe MHD wave propagation in coronal holes. Recent efforts were concentrated in two areas: the development of numerical codes to properly describe the hydrodynamics of the flow, and more realistic models of the coronal hole properties such as density gradients and spherical divergence of the flux tube. Some of the important aspects of the theory are discussed, including the effect of density inhomogeneities and smooth transverse density gradients. In addition it is hoped that some early results from the numerical models will be presented. The acceleration of cool winds is a problem of interest in cool supergiants also. Some work was done on the development of wind models for these stars as well.

Davila, Joseph M.↗
NASA NTRS1988

Recursive mass matrix factorization and inversion: An operator approach to open- and closed-chain multibody dynamics

This report advances a linear operator approach for analyzing the dynamics of systems of joint-connected rigid bodies.It is established that the mass matrix M for such a system can be factored as M=(I+H phi L)D(I+H phi L) sup T. This yields an immediate inversion M sup -1=(I-H psi L) sup T D sup -1 (I-H psi L), where H and phi are given by known link geometric parameters, and L, psi and D are obtained recursively by a spatial discrete-step Kalman filter and by the corresponding Riccati equation associated with this filter. The factors (I+H phi L) and (I-H psi L) are lower triangular matrices which are inverses of each other, and D is a diagonal matrix. This factorization and inversion of the mass matrix leads to recursive algortihms for forward dynamics based on spatially recursive filtering and smoothing. The primary motivation for advancing the operator approach is to provide a better means to formulate, analyze and understand spatial recursions in multibody dynamics. This is achieved because the linear operator notation allows manipulation of the equations of motion using a very high-level analytical framework (a spatial operator algebra) that is easy to understand and use. Detailed lower-level recursive algorithms can readily be obtained for inspection from the expressions involving spatial operators. The report consists of two main sections. In Part 1, the problem of serial chain manipulators is analyzed and solved. Extensions to a closed-chain system formed by multiple manipulators moving a common task object are contained in Part 2. To retain ease of exposition in the report, only these two types of multibody systems are considered. However, the same methods can be easily applied to arbitrary multibody systems formed by a collection of joint-connected regid bodies.

Rodriguez, G.↗
NASA NTRS1987

Lunar base objectives and open questions

The basic characteristics of the NASA program for establishing a lunar base are described and examined. The scientific objectives of the program are the planetological investigation of the moon and the use of the moon as a base for astronomical observations. It is argued that the development of a lunar base will assist in the advancement of science, the development of lunar resources to support space activities, and the development of a permanently, self-supported human colony away from the earth. The technological and operational capabilities needed in order to establish a lunar base are discussed.

Duke, Michael B.↗