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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Noise measurement in wind tunnels, workshop summary

In reviewing the progress made in acoustic measurements in wind tunnels over the 5-yr span of the workshops, it is evident that a great deal of progress has occurred. Specialized facilities are now on line, special measurement techniques were developed, and corrections were devised and proven. This capability is in the process of creating a new and more correct data bank on acoustic phenomena, and represents a major step forward in acoustics technology. Additional work is still required, but now, rather than concentrating on facilities and techniques, researchers may more profitably concentrate on noise-source modeling, with the simulation of propulsor noise source (in flight) and of propulsor/airframe airflow characteristics. Promising developments in directional acoustic receivers and other discrimination/correlation techniques should now be regularly exploited, in part for model noise-source diagnosis, but also to expedite extraction of the lone source signal from any residual background noise and reverberation in the working chamber and from parasitic noise due to essential rigs or instrumentation inside the airstream.

Hickley, D. H.↗
NASA NTRS1981

Identification of new solar OH lines in the 10-12 micron region

High-resolution (0.02/cm) infrared solar spectra obtained with a balloon-borne interferometer reveal new solar absorption features, which appear as regularly spaced quartets, in the 825-960/cm region. The lines are interpreted as high N-double-prime (25-33) pure rotation lines of solar OH. An effective amount of approximately 8 x 10 to the 15th molecules/sq cm of OH is estimated from the spectra.

Goldman, A.↗
NASA NTRS1981

On the injection and scattering of protons in Jupiter's magnetosphere

The interaction, scattering, and acceleration of Jovian ions through magnetohydrodynamic waves are investigated. A model of the Alfven speed in the plasma sheet for both inbound and outbound legs of the Voyager 1 encounter is presented, and underlying assumptions are discussed. Theoretical ingredients of a rotationally driven Jovian substorm are defined, and the convective growth rate of the fast wave for both a warm and a cold beam is derived. The mean-free path for scattering based on in situ measurements of magnetic fluctuations in the plasma sheet is estimated, and the results indicate that scattering of super-Alfvenic ions occurs on a regular basis throughout the plasma sheet, and the observed level of magnetic fluctuations is sufficiently high to stop ionospheric protons.

Barbosa, D. D.↗
NASA NTRS1981

Giant glitches and pinned vorticity in the Vela and other pulsars

Previously unexamined regularities in the Vela pulsar timing data are noted, and explained by a theory of giant glitches in the Vela and other pulsars as the dynamic consequence of catastrophic unpinning events in the pinned crustal neutron superfluid. Postglitch behavior then results from the glitch-induced vortex creep. An implication of the theory is that the energy release in this glitch scenario need not appear instantaneously on the surface as heat.

Alpar, M. A.↗
NASA NTRS1981

Ellipsoidal corrections for geoid undulation computations using gravity anomalies in a cap

Ellipsoidal correction terms have been derived for geoid undulation computations when the Stokes equation using gravity anomalies in a cap is combined with potential coefficient information. The correction terms are long wavelength and depend on the cap size in which its gravity anomalies are given. Using the regular Stokes equation, the maximum correction for a cap size of 20 deg is -33 cm, which reduces to -27 cm when the Stokes function is modified by subtracting the value of the Stokes function at the cap radius. Ellipsoidal correction terms were also derived for the well-known Marsh/Chang geoids. When no gravity was used, the correction could reach 101 cm, while for a cap size of 20 deg the maximum correction was -45 cm. Global correction maps are given for a number of different cases. For work requiring accurate geoid computations these correction terms should be applied.

Rapp, R. H.↗
NASA NTRS1981

Coping with space motion sickness in Spacelab missions

Lessons learned from Skylab are applied to methods of dealing with space sickness among crewmembers in their first orbital flight. Early experiences on Skylab 3 led to regularly scheduled scopalamine/dexedrine tablets ingestion. Subsequent experiences on the next Skylab mission established a 75% incidence of the sickness among first-time-in-orbit crewmembers, notably in periods of inactivity rather than work periods. Intramuscular injections are recommended to treat acute space sickness. Preflight transdermal scopalamine plus three or four doses of 5 mg amphetamine are chosen preventive measures, giving 12 hours of efficacy.

Graybiel, A.↗
NASA NTRS1981

Enzymatic capacities of skeletal muscle - Effects of different types of training

Long-term adaptation mechanisms to maintain homeostasis at increased levels of exertion such as those caused by regular exercise are described. Mitochondrial changes have been found to be a result of endurance exercises, while mitochondrial responses to other types of exercise are small. Further discussion is devoted to long-term changes in glucose transport, hexokinase, phosphofructokinase, pyruvate kinase, and the increased sensitivity of an endurance trained muscle to insulin. Less lactate has been found to be produced by the skeletal muscles at the same work rate after adaptation to endurance exercise training, and the capacity for the flux of the two-carbon acetyl chain through the citric acid cycle increases in skeletal muscles in response to endurance training. Finally, endurance training is noted to result in glycogen sparing and an increase in the capacity to utilize fatty acids.

Booth, F. W.↗
NASA NTRS1981

Transversely accelerated ions in auroral arcs

Ionospheric ions apparently accelerated transversely to the geomagnetic field in the topside ionosphere are regularly detected by the soft particle spectrometers on the ISIS satellites. Such gyro-accelerated ions are observed in association with precipitating auroral electrons. A detailed study of their relationship with such electrons and with field-aligned currents, together with simultaneous measurements of the local plasma composition and density, reveals the specific conditions present in the topside ionosphere during the generation of such transversely accelerated ions (TAI). A proposed mechanism for generation of TAI involving acceleration by electrostatic ion cyclotron waves is consistent with the present observations.

Klumpar, D. M.↗
NASA NTRS1981

Integration of energy management concepts into the flight deck

The rapid rise of fuel costs has become a major concern of the commercial aviation industry, and it has become mandatory to seek means by which to conserve fuel. A research program was initiated in 1979 to investigate the integration of fuel-conservative energy/flight management computations and information into today's and tomorrow's flight deck. One completed effort within this program has been the development and flight testing of a fuel-efficient, time-based metering descent algorithm in a research cockpit environment. Research flights have demonstrated that time guidance and control in the cockpit was acceptable to both pilots and ATC controllers. Proper descent planning and energy management can save fuel for the individual aircraft as well as the fleet by helping to maintain a regularized flow into the terminal area.

Morello, S. A.↗
NASA NTRS1982

Scale-free models of galaxies. II - A complete survey of orbits

A complete set of orbits starting at over 400 distinct points spread out in the phase space of an oblate scale-free potential is investigated. Each orbit is followed for a time that corresponds to a Hubble time in a realistic galaxy potential suitable for an E5 or E6 galaxy. It is noted that none of the orbits in the survey is ergodic. All of the survey orbits are regular, visiting a region at least one dimension smaller than expected from the classical integrals of motion. Thus, for all practical purposes, they have an extra nonclassical isolating integral. Approximately 95% of the survey orbits are box orbits, the rest being pipes (formerly tubes). The survey exposes an ambiguity in the original classification scheme for orbits, which, it is noted, can be resolved on the basis of the topology of an orbit's surface of section. Nevertheless, the distinction between high order very convoluted pipes and boxes is probably artificial for practical purposes.

Richstone, D. O.↗
NASA NTRS1982

Photoelectric observations of propagating sunspot oscillations

Repeated intensity and velocity images of a large, isolated sunspot in both the chromospheric Ca II 8542 A and photospheric Fe I 5576 line were performed. It is shown by means of a movie of the digital data for the chromospheric line that a relationship exists between the propagating umbral disturbances and the running penumbral waves. Power spectra of the oscillations show a sharp peak at a period of about 170 sec in both the velocity and intensity signals, and the oscillations at any point in the sunspot are found to be very regular. The phase relationship between the velocity and the intensity of the chromospheric oscillations contrasts with that for the quiet sun. The mechanical energy flux carried by the observed umbral disturbances does not appear to be a significant contributor to the overall energy budget of the sunspot or the surrounding active region.

Lites, B. W.↗
NASA NTRS1982

Harmonic structure of Pc 3-4 pulsations

Power spectra of magnetic pulsations observed at synchronous orbit by the ATS 6 satellite often show several spectral peaks simultaneously. Such pulsations, called harmonic events because of the nearly constant separation between successive peaks, are continuously observed in the dayside in the Pc 3-4 frequency range (6.6-100 mHz). The harmonic events are seen clearly only in the east-west magnetic field component. The spectral peaks are regularly spaced with a typical minimum separation of 14 mHz in the morning gradually decreasing to 10 mHz in the afternoon. In the dynamic spectra of harmonic events, the fundamental mode is usually absent. In addition, the relative amplitudes of the higher harmonics depend on the magnetic latitude. These observed features can be explained by a standing Alfven wave consisting of many discrete harmonic frequencies. A statistical analysis of power spectra demonstrates that at least 10-30% of Pc 3 pulsations can be classified as harmonic events. For a selected event on August 7, 1975, the plasma mass density at the synchronous orbit is estimated to be 3-8 hydrogen mass/cu cm.

Takahashi, K.↗
NASA NTRS1982

On the geometric form of volcanoes - Comment

The model of Lacey et al. (1981) accounting for the geometric regularity and approximate cone shape of volcanoes is discussed. It is pointed out that, contrary to the model, volcano eruptions do not occur randomly in elevation and azimuth, but are commonly restricted to summit vents and a few well defined flank zones, so that the form of a volcano is determined by its vent locations and styles of eruption. Other false predictions of the model include the constancy of lava volumes at all vent elevations, the increase in volcano radius as the square root of time, a critical height for volcano growth, the influence of planetary gravity on volcano height and the negligible influence of ash falls and flows and erosional deposition. It is noted that the model of Shteynberg and Solov'yev, in which cone shape is related to stresses due to increasing cone height, may provide a better understanding of volcano morphology.

Wood, C. A.↗
NASA NTRS1982

Induced venous pooling and cardiorespiratory responses to exercise after bed rest

Venous pooling induced by a specially constructed garment is investigated as a possible means for reversing the reduction in maximal oxygen uptake regularly observed following bed rest. Experiments involved a 15-day period of bed rest during which four healthy male subjects, while remaining recumbent in bed, received daily 210-min venous pooling treatments from a reverse gradient garment supplying counterpressure to the torso. Results of exercise testing indicate that while maximal oxygen uptake endurance time and plasma volume were reduced and maximal heart rate increased after bed rest in the control group, those parameters remained essentially unchanged for the group undergoing venous pooling treatment. Results demonstrate the importance of fluid shifts and venous pooling within the cardiovascular system in addition to physical activity to the maintenance of cardiovascular conditioning.

Convertino, V. A.↗
NASA NTRS1982

The spectrum of the Jovian Aurora 1150-1700 A

A series of observations of the northern hemisphere of Jupiter was made in January 1981 using the International Ultraviolet Explorer short-wavelength spectrograph. Exposures of 15 minutes each were made at regular intervals of about 45 minutes around the time when Jupiter's north magnetic pole was tilted toward the earth. The auroral emissions of H Lyman-alpha, and the H2 Lyman- and Werner-bands are seen to emanate from a localized region near the north pole. Their intensity increases and decreases in a periodic way as the planet rotates with the maximum occurring at lambda sub III approximately equal to 185 deg. Using the three observations nearest the observed maximum, a composite spectrum of the aurora is obtained with about 8 A resolution and high signal-to-noise ratio, and many of the H2 Lyman- and Werner-bands in this spectral region (1150-1700 A) are identified. This spectrum is compared with a laboratory H2 spectrum and with photoabsorption cross sections for CH4 and C2H6. An upper limit to the slant column density of these hydrocarbons above the auroral emissions is found to be approximately 2 x 10 to the 17th/sq cm.

Durrance, S. T.↗
NASA NTRS1982

Surface morphology of erbium silicide

The surface of rare-earth silicides (Er, Tb, etc.), formed by the reaction of thin-film metal layers with a silicon substrate, is typically dominated by deep penetrating, regularly shaped pits. These pits may have a detrimental effect on the electronic performance of low Schottky barrier height diodes utilizing such silicides on n-type Si. This study suggests that contamination at the metal-Si or silicide-Si interface is the primary cause of surface pitting. Surface pits may be reduced in density or eliminated entirely through either the use of Si substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition and silicide formation or by means of ion irradiation techniques. Silicide layers formed by these techniques possess an almost planar morphology.

Lau, S. S.↗
NASA NTRS1982

ORACLS - A linear-quadratic-Gaussian computer-aided design package

ORACLS, an acronym denoting Optimal Regular Algorithms for the Control of Linear Systems, is a collection of FORTRAN coded subroutines dedicated to the formulation and solution of the Linear-Quadratic-Gaussian (LQG) design problem modeled in both continuous and discrete form. The ORACLS system is under continuous development at the NASA Langley Research Center, Hampton, Virginia, and is widely used by universities and industry within the U.S.A. The current (operational) ORACLS version as well as new software under development is described.

Armstrong, E. S.↗
NASA NTRS1982

The effect of brokenness on cloud-climate sensitivity

A study has been made of the effect of brokenness on the infrared and albedo feedback of clouds in climate models using a simplified treatment of broken cloudiness. It is shown that the individual feedback terms computed using the plane-parallel assumption differ markedly from the computations performed for a regular array of cuboidal clouds. If the cloudiness changes such that clear areas become cloudy but the nature of the broken cloud field remains unchanged, then both the feedbacks are magnified, the infrared more so than the albedo. However, if individual elements in the cloud field are increased horizontally in a constrained area, the feedbacks can be enhanced or diminished depending on the cloud fraction and aspect ratio of the elements. It is also shown that, in the global average, the ratio of the change in outgoing infrared flux to global albedo, as deduced from satellite measurements, will be larger than model simulations using planiform clouds.

Harshvardhan, MR.↗