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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 631 records · Page 35
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NASA NTRS1981

The possible effect of 11 year solar cycle on the thermal structure of the stratosphere and ozone distribution investigated in a 2-D model

A two-dimensional time dependent radiative-photochemical-dynamical model of the stratosphere which takes into account the feedback effect of temperature on ozone concentration is used to investigate the possible changes in the seasonal and latitudinal variations of temperature, ozone, and other minor constituents associated with the UV flux variations from the solar minimum to the solar maximum. The transport model determines the zonal wind, non-zonal eddy transports, and eddy momentum fluxes, while the photochemical system includes the important reactions affecting the concentrations of ozone and other relevant trace constituents in the stratosphere. Experiments are carried out by changing the position of the sun every day and evaluating the daily average photodissociation integrals for the relevant minor constituents and ozone heating. Values are found for the ambient stratosphere and a stratosphere perturbed by solar cycle variations, and a rough comparison is made with observed ozone and temperature trends.

Vupputuri, R. K. R.↗
NASA NTRS1973

Interplanetary gas. XVIII - Models and the mean free path of protons at 1 astronomical unit.

Velocity distribution functions of solar-wind protons obtained by the Vela 3 satellites have been analyzed to obtain a microscopic determination of the momentum flux along magnetic field lines with respect to a reference frame moving at the bulk speed. The determination from macroscopic parameters allows the calculation of an effective mean free path for protons at 1 AU which averages 0.06 AU and is relatively independent of solar-wind velocity w. For quiet times when w is from 300 to 400 km/sec, the experimental mean free path is 2 to 3 times smaller than the value from plasma theory. For w greater than 400 km/sec, the experimental value is 10 to 100 times smaller than the theoretical value.

Brandt, J. C.↗
NASA NTRS1973

Opportunities for space surveys of moisture anomalies

Review of a combination of infrared scanning, unsupervised spectroscopic classification, change detection, and perturbation spectroscopy for monitoring anomalous moisture exchange from space. Infrared sensors have been developed which can monitor the solar reflectance from droplet distributions in vegetation and clouds, the absorption of thermal radiation by water vapor, and the microwave attenuation by atmospheric water. Unsupervised spectroscopic classification techniques are emerging which have the potential to subdivide strip maps from infrared scanners into different moisture targets. Intersecting and parallel spacecraft orbits provide opportunities to study the change of recognized targets between two scans and to recognize anomalous moisture exchange from those changes which significantly exceed the statistical uncertainty of the spectroscopic target signature. The new concept of perturbation spectroscopy shows a potential to quantitatively determine the change of integrated water vapor pressure with a minimum of 'atmospheric truth' and with low spectroscopic resolution that is typical of simple interference filters.

Krause, F. R.↗
NASA NTRS1974

Homeostatic tendencies of the earth's atmosphere

The concept is developed that the atmosphere of the earth flows in a closed system controlled by and for the biosphere. The environmental factors delimiting the biosphere are examined. It is found that neither oxygen nor pressure per se limit the distribution of life as a whole. Rather the major physical variables determining the distribution of organisms are solar radiation, temperature, water abundance, and the concentrations of hydrogen and other ions and elements. An attempt is made to model temperature and atmospheric composition of a lifeless earth.

Lovelock, J. E.↗
NASA NTRS1974

Rigid and differential rotation driven by oscillations within the sun

Long-period oscillations involving the entire mass of the sun rotate like rigid bodies, and their oscillatory power is distributed nonuniformly across the solar surface. A mostly qualitative theory is constructed showing how the oscillations drive convective flows of global scale, which then organize photospheric and coronal magnetic fields into patterns which rotate rigidly. The convection rises along long graceful curves, creating the magnetic-arcade structures in the corona and unipolar photospheric regions on each side by dynamo action. These are thought to be the origin of the sector structure in the solar wind. The rigid patterns of convective upwelling also force nonrigid horizontal winds on the solar surface. Under the action of the Coriolis force, the main horizontal motions are converted into polar and equatorial wind currents which have the proper directions to drive the differential rotation long observed on the sun's surface.

Wolff, C. L.↗
NASA NTRS1975

The quiet-time low energy nucleon spectrum in the vicinity of earth

Observations of the low energy quiet-time interplanetary nucleon spectrum obtained by Explorer 47 are examined for March 9-12, 1973, the quietest period from Sept. 26, 1972 through Feb. 15, 1975. The quiet-time energy spectrum may be represented by a power law with an index of about -3.1. The H/He ratio below 2 MeV is about 10. The ratio of antisunward to sunward intensities is about 2.6, increasing to about 8.55 in a frame moving with the solar wind. The angular distributions show that in the 0.3-0.5 MeV range most of the proton intensity originates in the earth's magnetosphere. The spectral behavior and enhancement of proton counting rates during microbursts suggest that the magnetosphere is a significant source at energies up to 2 MeV. The observed intensities are lower than those reported by Simpson and Tuzzolino (1973) by factors of 3 to 10. It is suggested that the low energy upturn in the quiet-time interplanetary proton spectrum may be related to particle emissions from planetary magnetospheres, such as that of Jupiter.

Krimigis, S. M.↗
NASA NTRS1976

Temperature distribution of a hot water storage tank in a simulated solar heating and cooling system

A 2,300-liter hot water storage tank was studied under conditions simulating a solar heating and cooling system. The initial condition of the tank, ranging from 37 C at the bottom to 94 C at the top, represented a condition midway through the start-up period of the system. During the five-day test period, the water in the tank gradually rose in temperature but in a manner that diminished its temperature stratification. Stratification was found not to be an important factor in the operation of the particular solar system studied.

Namkoong, D.↗
NASA NTRS1979

Differences between seasonal and mean annual energy balance model calculations of climate and climate sensitivity

The paper extends a simple Budyko-Sellers mean annual energy balance climate model with diffusive transport to include a seasonal cycle. In the model the latitudinal distribution of the zonal average surface temperature is represented by Legendre polynomials and its time-dependence by a Fourier sine-cosine series, and it has three parameters adjusted so that the observed amplitudes of the Northern Hemisphere zonal mean surface temperature are recovered. The seasonal model is used to reveal how the annual mean climate and the sensitivity to changes in incident radiation differ from the predictions obtained with the corresponding mean annual model. The distribution of the incident solar radiation in the models is shown to be insensitive to changes in the eccentricity and the longitude of perihelion and sensitive only to changes in the obliquity of the earth, and for past orbital changes both the seasonal and the mean annual model fail to produce glacial advances of the magnitude that are thought to have occurred.

North, G. R.↗
NASA NTRS1979

Solar power satellite system definition study, volume 4, phase 2

Results of an overall evaluation of the solar power satellite concept are reported. Specific topics covered include: solid state sandwich configuration; parametric development of reliability design; power distribution system for solid state solar power satellites; multibeam transmission; GEO base system configuration; suppression of the heavy lift launch vehicle trajectory; conceptual design of an offshore space center facility; solar power satellite development and operations scenario; and microwave power transmission technology, advancement, development, and facility requirements.

Source record↗
NASA NTRS1980

Solar heating system at Security State Bank, Starkville, Mississippi

The 312 square feet of Solaron flat plate air collectors provide for 788 square feet of space heating, an estimated 55 percent of the heating load. Solar heated air is distributed to the 96 cubic foot steel cylinder, which contains two inch diameter rocks. An air handler unit moves the air over the collector and into the steel cylinder. Four motorized dampers and two gravity dampers are also part of the system. A Solaron controller which has sensors located at the collectors, rock storage, and at the return air, automatically controls the system. Auxiliary heating energy is provided by electric resistance duct heaters.

Source record↗
NASA NTRS1980

Physical characteristics of cometary dust from dynamical studies - A review

Progress made in the determination of the physical characteristics of cometary dust particles from studies of dust tail dynamics is reviewed. Applications of the combined dynamical photometric approach of Finson and Probstein (1968) to studies of cometary tails exhibiting continuous light intensity variations are discussed, with attention given to determinations of the particle-size-related distribution function of the solar radiation pressure exerted on the particles, the contribution of comets to the interplanetary dust, calculations of dust ejection rates and a Monte Carlo approach to the analysis of dust tails. Investigations of dust streamers and striae, which are believed to be related to comet outbursts entailing brief but sharp enhancements of dust production, are then reviewed, with particular attention given to observations of Comet West 1976 VI. Finally, the question of cometary particle type is addressed, and it is pointed out that the presence of submicron absorbing particles in the striae of Comet West is not incompatible with the presence of micron-size dielectric particles in the inner coma.

Sekanina, Z.↗
NASA NTRS1980

Finite element models and feedback control of flexible aerospace structures

Large flexible aerospace structures, such as the solar power satellite, are distributed parameter systems with very complex continuum descriptions. This paper investigates the use of finite element methods to produce reduced-order models and finite dimensional feedback controllers for these structures. The main results give conditions under which stable control of the finite element model will produce stable control of the actual structure.

Balas, M. J.↗
NASA NTRS1981

Control system development for an organic Rankine cycle engine

The development of a control logic to govern the toluene throttle valve and verify the stability of the speed control approach for multiple engines connected to a 1 MWe point focus solar generator installation for distributed applications is presented. The toluene is is pumped by booster and main feed pumps through a regenerator to the parabolic focus receiver, with the flow rate controlled by a valve to remain at critical level of 4.1 MPa. The valve changes the inlet pressure at the turbine nozzle block. Each concentrator would produce 76 kWth and 20 kWe. Dynamic variables in the logic account for insolation variation, fluid temperature, ac grid voltage, the thermal dynamics of the regenerator, and variations in the head supplied by the feed pump. Separate analyses are presented for the turbine shaft speed and toluene loop dynamics. The resulting logic is considered preliminary and suitable only in full insolation conditions. Extension of the model to nonlinear perturbations is indicated.

Bergthold, F. M., Jr.↗
NASA NTRS1982

Lower hybrid waves in the solar wind

It is demonstrated that the frequently observed broad band low frequency electrostatic noise in the solar wind generally has a dominant lower hybrid component. These modes are probably produced by the anisotropic halos of the solar wind electron velocity distributions exhibiting 'heat flux' profiles and thus, are accompanied by broad band, 'hybrid-like' whistler waves. When the electron temperature is much larger than the ion temperature, these modes can also co-exist with the ion acoustic waves. Since lower hybrid modes propagate nearly normal to the interplanetary magnetic field lines, the ions can be transversely accelerated by these waves and attain the observed anisotropic and/or loss-cone-like distributions.

Marsch, E.↗