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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The role of modern control theory in the design of controls for aircraft turbine engines

The development, applications, and current research in modern control theory (MCT) are reviewed, noting the importance for fuel-efficient operation of turbines with variable inlet guide vanes, compressor stators, and exhaust nozzle area. The evolution of multivariable propulsion control design is examined, noting a basis in a matrix formulation of the differential equations defining the process, leading to state space formulations. Reports and papers which appeared from 1970-1982 which dealt with problems in MCT applications to turbine engine control design are outlined, including works on linear quadratic regulator methods, frequency domain methods, identification, estimation, and model reduction, detection, isolation, and accommodation, and state space control, adaptive control, and optimization approaches. Finally, NASA programs in frequency domain design, sensor failure detection, computer-aided control design, and plant modeling are explored

Zeller, J.↗
NASA NTRS1982

Source abundances and propagation of relativistic cosmic rays up to Z equals 30 - HEAO 3 results

Results from the cosmic ray isotope experiment on board the HEAO 3 satellite are reviewed, noting their impact on astrophysics. The gamma ray telescope comprised 5 Cerenkov detectors and a flash tube hodoscope with 4 trays, and collected data on 7 million events in the energy range 0.7-20 GeV/nucleon during the 1.6 yr mission duration. Three ranges of momentum were detected, and it was found that the ratios of secondary to primary species decreased steeply with increasing energy. A progressive steepening of the energy dependence of abundance ratios from Al/Si and K/Fe was observed, which has been interpreted as a progressive decrease of the amount of primary component from Al to Na and K. The secondary to primary ratios are accounted for with an exponential pathlength distribution from Fe down to Na and N. Comparisons are made of elemental abundances in cosmic ray sources, the local galactic environment, and the solar energetic particle composition. The data is noted to be compatible with a model of an injection of cosmic ray particles by stellar flares in a two-stage acceleration process.

Koch-Miramond, L.↗
NASA NTRS1982

Effect of limb immobilization on skeletal muscle

Current knowledge and questions remaining concerning the effects of limb immobilization on skeletal muscle is reviewed. The most dramatic of these effects is muscle atrophy, which has been noted in cases of muscles fixed at or below their resting length. Immobilization is also accompanied by a substantial decrease in motoneuronal discharges, which results in the conversion of slow-twitch muscle to muscle with fast-twitch characteristics. Sarcolemma effects include no change or a decrease in resting membrane potential, the appearance of extrajunctional acetylcholine receptors, and no change in acetylcholinesterase activity. Evidence of changes in motoneuron after hyperpolarization characteristics suggests that the muscle inactivity is responsible for neuronal changes, rather than vice versa. The rate of protein loss from atrophying muscles is determined solely by the first-order rate constant for degradation. Various other biochemical and functional changes have been noted, including decreased insulin responsiveness and protein synthesis. The model of limb immobilization may also be useful for related studies of muscle adaptation.

Booth, F. W.↗
NASA NTRS1981

Winds in late-type stars - Mechanisms of mass outflow

The four basic mechanisms that have been proposed for explaining the acceleration of winds in late-type stars are thermal pressure gradients, radiation pressure on circumstellar dust grains, momentum addition by Alfven waves, and momentum addition by periodic shock waves. Recent work in applying these mechanisms to stars is reviewed, with consideration given to whether these mechanisms can work, even in principle, and whether they are consistent with recent ultraviolet and X-ray data from the IUE and Einstein spacecraft. It is noted that thermally driven winds are likely important for late-type dwarfs, where the mass loss rates are small, and perhaps also in G giants and supergiants, but they cannot operate alone in the K and M giants and supergiants. It is thought that radiatively driven winds are probably unimportant for all cool stars, even the M supergiants with dusty circumstellar envelopes. In principle, Alfven waves can accelerate winds to high speeds so long as the field lines are initially open or forced open by some mechanism, but detailed calculations are needed. It is noted that, for the Miras and semiregular variable supergiants, periodic shock waves provide a simple way of producing rapid mass loss.

Linsky, J. L.↗
NASA NTRS1982

A comparison between satellite-defined and parameterized land-water differences in emitted longwave radiation

An analysis is performed to qualitatively compare the seasonal variation in emitted longwave radiation over land and over water areas as determined from 12 months of Nimbus 6 satellite data with that defined from parameterizations of this radiation budget component. These variations are noted when land and water surface areas are mapped to corresponding areas at the 'top' of the atmosphere. Variations of a surface-temperature-dependent parameterization of emitted longwave radiation originally suggested by Budyko (1969) are considered. The longwave radiation parameterizations indicate small differences between land and water profiles of emitted longwave radiation at the top of an atmospheric column in low latitudes in comparison to large differences in this feature shown to exist in the satellite data. The small differences are noted in linear parameterizations of emitted flux when zonally-averaged satellite data are used to define equation coefficients.

Stephenson-Graves, D.↗
NASA NTRS1982

Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth

It is pointed out that numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242-300 nm. This coincides with the wavelength range used by orbiting spectrometers that observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations suggest that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Sigma) is sufficiently small. It is noted that this is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements have shown a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. Very small quenching rates, however, are adequate to reduce the dayglow emission to negligible levels. Noting that available laboratory data have not definitely established the quenching on the rate of O2(A3Sigma) as a function of vibration level, it is emphasized that such information is required before the Herzberg band contributions can be evaluated with confidence.

Frederick, J. E.↗
NASA NTRS1982

Earth-based radar studies of planetary surfaces and atmospheres

Remote sensing of solar system bodies using the JPL Goldstone facility and the radio telescope at Arecibo to characterize the surfaces of the objects is described in terms of present and planned studies. Moon observations proceed at wavelengths from 8.6 mm to 20 m, and are nominally in the centimeter range. Cross sections available from the radar data and apparatus are discussed, noting the practice of using backscattered signals to define the shape of terrain. A review is presented of polarization properties models of the moon's surface, and the design of an experiment using a spacecraft with bistatic radar to determine the dielectric constant of the moon's surface is outlined. Radar is noted to have been used to characterize the rotation period of Mercury, the absorption profile and the topography of Venus, and aided in choosing a landing site for the Viking spacecraft. The existence of higher-than-expected polarization near the Galilean satellites is mentioned as an unexplained phenomenon.

Jurgens, R. F.↗
NASA NTRS1983

Electron beam charging and arc discharging of spacecraft insulating materials

Samples of Mylar and Teflon film were exposed to combinations of monoenergetic electron and lithium ion fluxes in various ratios. The samples' discharge rates and strengths were found to diminish as the ion proportion increased. Various types of capacitors were exposed in air to beta irradiation from a 100 mCie Strontium-90 radioisotope source located at distances ranging from 2 cm to 5 cm from the capacitors. In these preliminary experiments, no evidence of spontaneous electrical breakdown was noted, nor was any change in RF impedance detectable using the available instrumentation. A decrease in DC resistance was noted, apparently due to radiation-induced conductivity. A cylindrical glass vacuum chamber is being assembled. Its inside dimensions are 44 cm diameter by 100 cm length. All necessary associated components and instruments have been acquired, including electron and ion guns, Trek surface potential probe and turbo-molecular pump. A mass-spectrometer detector for leaks and evolved gases will be ordered shortly.

Balmain, K. G.↗
NASA NTRS1983

Travelling wave effects in large space structures

Several aspects of travelling waves in Large Space Structures(LSS) are discussed. The dynamic similarity among LSS's, electric power systems, microwave circuits and communications network is noted. The existence of time lag between actuation and response is illuminated with the aid of simple examples, and their prediction is demonstrated. To prevent echoes, communications lines have matched terminations; this idea is applied to the design of dampers of one dimensional structures. Periodic structures act as mechanical band pass filters. Implications of this behavior are examined on a simple example. It is noted that the implication is twofold; continuum models of periodic lattice structures may err considerably; on the other hand, it is possible to design favorable transmission (and resonance) characteristics into the structure.

Vonflotow, A.↗
NASA NTRS1982

Gamma-ray burst observations by the HEAO-3 high-resolution gamma-ray spectrometer

Special attention is given to two bursts occurring on November 16, 1979. Because of the close temporal coincidence of the two events, the possibility that both originated from a single celestial source is considered, as is the possibility that the scanning motion of HEAO-3 (nominal spin period, 20 min) was such as to exclude the first from the (approximately 30 deg FWHM) field of view of the germanium detectors and include the second. Directional data from the relative response of the shield pieces and earth occultation constraint are found to be consistent with this interpretation, and high-resolution spectral data from the second burst are discussed in this light. It is noted that recent unpublished analyses of long-baseline timing data from interplanetary spacecraft reveal that the response in the HEAO high-resolution detectors is probably earth albedo scattering. This, it is noted, can be an important systematic effect in low-earth orbit.

Wheaton, W. A.↗
NASA NTRS1983

Bending waves in Saturn's rings

Saturn A ring brightness variations are investigated and noted to be caused by vertical corrugations of the local ring plane due to a spiral bending wave, resonantly excited by Mimas, which propagates inwardly by way of the ring particle collective gravity. Some aspects of the presently developed theory of forced bending waves have been previously treated in the galactic context. It is noted that the theory is generally in good agreement with observations, and in particular may resolve the conflict between ground-based estimates of 1-2 km for the global ring thickness and Voyager stellar occultation measurements of less than 200 m for the local ring thickness.

Shu, F. H.↗
NASA NTRS1983

Variability in the power spectrum of solar five-minute oscillations

It is noted that two-dimensional power spectra of solar five-minute oscillations exhibit prominent ridge structures in (k, omega) space, k being the horizontal wavenumber and omega the temporal frequency. The positions of these ridges in k and omega can be used in probing temperature and velocity structures in the subphotosphere. The progress made in a program to establish whether power spectra taken on separate days show shifts in ridge locations is surveyed, noting that these may arise from different velocity and temperature patterns having been brought into the sampling region by solar rotation. Power spectra are obtained for six days of observations of Doppler velocities using the Mg I 5173 A and Fe I 5434 A spectral lines. Each data set encompasses 8 to 11 hr in time and samples a region 256 x 1024 arcsec in spatial extent, with a spatial resolution of 2 arcsec and temporal sampling of 65 s. Statistically significant shifts are detected in ridge locations between certain data sets. When analyzed in terms of eastward and westward propagating waves, the character of these displacements is seen as implying that changes have occurred in both temperature and horizontal velocity fields underlying the observing window. The velocity changes are estimated to be of the order of 100 m/s.

Hill, F.↗
NASA NTRS1982

Advanced pointing systems for space astronomy

It is noted that the requirements on image stability are increasing, often at the same time that instrument external disturbances are increasing. A prime example of this is the pointing of large diameter optics from the Shuttle bay. To achieve cost-effective advanced pointing systems in the face of these problems, a system approach must be followed, one that encompasses a realistic assessment of requirements, the best possible detector technology, and a broad look at space vehicles and pointing systems that are available. By way of example, a rocket instrument for making measurements of the interstellar gas that uses a standard pointing system to achieve a spectral resolution of 2 x 10 to the 5th is described. It is noted that the use of a free-flying instrument avoids the high-frequency components that degrade the instrument resolution.

Delamere, W. A.↗
NASA NTRS1983

Space Shuttle solid rocket booster initial water impact loads and dynamics - Analysis, tests, and flight experience

A series of scale model tests, finite element dynamic response analyses and full scale segment tests have been performed for purposes of developing design criteria for the initial water impact loading conditions applied to the internal stiffener rings located in the aft skirt portion of the Space Shuttle Solid Rocket Booster (SRB). In addition, flight experience has yielded information relative to structural reinforcement requirements. This paper discusses the test and analysis methods and summarizes significant results. It is noted that, although scale model test data are valuable for identifying trends, they have shortcomings concerning definition of full scale design loads criteria. Also, the frequently used static equivalent loads definition approach is not applicable for this type impact loading condition applied to an aft skirt type structure. Various types of ring structural fixes, including the addition of selected types of foam, are presented as well as associated full scale segment test results. Depending on the type and contour shape of the foam, reductions on applied pressures and peak measured strains over 50 percent are noted.

Kross, D. A.↗
NASA NTRS1983

The interiors of the giant planets - 1983

It is noted the even though the current model of Jupiter is still based on certain somewhat vexatious approximations, it appears to satisfy the main observational constraints. Saturn's interior is much better understood today than heretofore, although the quantitative aspects of the role of the miscibility gap in the hydrogen-helium system have not yet been entirely resolved. Considerable attention has been given to the interiors of Uranus and Neptune, and the outstanding question appears to be the location and amount of ice and methane present in their outer layers. It is noted that both the two- and three-layer models are moderately successful. Serious difficulties follow from the considerable uncertainties concerning the rotational periods of both planets. In addition, the estimates of the internal heat fluxes and of the magnetic fields of both planets are not sufficiently certain.

Smoluchowski, R.↗
NASA NTRS1983

Composite engine duct fabrication

The trimonomer polyimide resin reinforced with graphite fibers, PMR15, is lower in weight (by 20 percent) and less expensive than titanium. The duct walls are of solid laminate and are made of woven T300 graphite cloth. The original concept for the duct involved a solid shell of T300/PMR15 made up of seven plies of cloth tapered to eleven plies at each end. The bosses and built-up areas around the cutouts are also of T300/PMR15. The end flages riveted to the shell, however, are of titanium. A buckling test demonstrated the ability of the composite analytical design techniques employed to predict the buckling strength of the composite shell. Engines tests are described, noting that the successful repair of a hole demonstrated an important advantage over titanium. The development work now being done to eliminate the titanium end flanges is described, noting that an all-composite duct is in prospect. The savings estimated with a titanium-flanged composite duct are $16,891,000 (1982 dollars) and $35,504,000 (then-year dollars); the savings possible with an all-composite duct are put at $27,025,000 (1982 dollars) and $56,806,000 (then-year dollars).

Pratt, R. D.↗
NASA NTRS1983

The propagation of torsion along flux tubes subject to dynamical nonequilibrium

It is noted that the dynamical nonequilibrium of close-packed flux tubes is driven by the torsion in the individual tubes. Because of this, whenever tubes with the same sense of twisting come into contact, there is reconnection of their azimuthal field components. The reconnection consumes the local torsion, and this causes the propagation of torsional Alfven waves into the region from elsewhere along the tubes. The formal problem of the propagation of the torsion along twisted flux tubes is presented, along with some of the basic physical properties worked out in the limit of small torsion. It is noted that in tubes with finite twisting the propagation of torsional Alfven waves can be a more complicated phenomenon. Application to the sun suggests that the propagation of torsion from below the visible surface up into the corona is an important energy supply to the corona for a period of perhaps 10-20 hours after the emergence of the flux tubes through the surface of the sun, bringing up torsion from depths of 10,000 km or more. Torsion is of course continually furnished by the manipulation and shuffling of the field by the convection.

Parker, E. N.↗
NASA NTRS1983

Petrology of ALHA 81005, the first lunar meteorite

The meteorite thought to be best described as a lunar highland regolith breccia from a non-KREEPy region. The controversy that remains as to the most likely source region is discussed. It is noted that several large lunar nearside craters have been proposed (Ostertag and Ryder, 1983). After finding a very-low-titanium (VLT) mare basalt clast in a thin section of ALHA 81005, Treiman and Drake (1983) have suggested that this constrains the source to being near a region with VLT basalt. It is pointed out, however, that the unexplored far side of the moon cannot be ruled out. Most of the lithic clasts that are abundant in the meteorite are members of the anorthosite-norite-troctolite highland suite. It is noted that plagioclase compositions in lithic clasts and single grains are calcic (An94-98).

Simon, S. B.↗