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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Thermal buffering of receivers for parabolic dish solar thermal power plants

A parabolic dish solar thermal power plant comprises a field of parabolic dish power modules where each module is composed of a two-axis tracking parabolic dish concentrator which reflects sunlight (insolation) into the aperture of a cavity receiver at the focal point of the dish. The heat generated by the solar flux entering the receiver is removed by a heat transfer fluid. In the dish power module, this heat is used to drive a small heat engine/generator assembly which is directly connected to the cavity receiver at the focal point. A computer analysis is performed to assess the thermal buffering characteristics of receivers containing sensible and latent heat thermal energy storage. Parametric variations of the thermal inertia of the integrated receiver-buffer storage systems coupled with different fluid flow rate control strategies are carried out to delineate the effect of buffer storage, the transient response of the receiver-storage systems and corresponding fluid outlet temperature. It is concluded that addition of phase change buffer storage will substantially improve system operational characteristics during periods of rapidly fluctuating insolation due to cloud passage.

Manvi, R.↗
NASA NTRS1980

Spinning for safety's sake

NASA Langley is currently engaged in a comprehensive research program to improve the stall/spin characteristics of general aviation airplanes. Part of this program has included systematic flight tests of a fully instrumented airplane to determine the effects of various tail, wing, and fuselage modifications, and variation of inertia, center-of-gravity, and control positions on the spin and recovery characteristics. Airplane equipment, onboard instrumentation ground equipment, test area, and test procedures have been combined to provide a safe, practical means for conducting research in preplanned hazardous conditions. Configuration changes produced spins varying from easily recoverable to unrecoverable, and wind section design significantly influenced airplane stall, spin, and recovery characteristics.

Stough, H. P., III↗
NASA NTRS1982

Efficient Energy-Storage Concept

Space-platform energy-storage and attitude-stabilization system utilizes variable moment of inertia of two masses attached to ends of retractable cable. System would be brought to its initial operating speed by gravity-gradient pumping. When fully developed, concept could be part of an orbiting solar-energy collection system. Energy would be temporarily stored in system then transmitted to Earth by microwaves or other method.

Brantley, L. W. J.↗
NASA NTRS1980

Applications of HCMM satellite data to the study of urban heating patterns

The first analyses of the Washington, D.C. area was completed in which a method was employed to determine the surface energy balance, moisture availability, and thermal inertia. Further analyses of the Clarksville, Tennessee area during project STATE were completed. To test a newly operational interactive system, a temperature study of the Central Pennsylvania Barrens was performed.

Carlson, T. N.↗
NASA NTRS1981

Theory of strong turbulence by renormalization

The hydrodynamical equations of turbulent motions are inhomogeneous and nonlinear in their inertia and force terms and will generate a hierarchy. A kinetic method was developed to transform the hydrodynamic equations into a master equation governing the velocity distribution, as a function of the time, the position and the velocity as an independent variable. The master equation presents the advantage of being homogeneous and having fewer nonlinear terms and is therefore simpler for the investigation of closure. After the closure by means of a cascade scaling procedure, the kinetic equation is derived and possesses a memory which represents the nonMarkovian character of turbulence. The kinetic equation is transformed back to the hydrodynamical form to yield an energy balance in the cascade form. Normal and anomalous transports are analyzed. The theory is described for incompressible, compressible and plasma turbulence. Applications of the method to problems relating to sound generation and the propagation of light in a nonfrozen turbulence are considered.

Tchen, C. M.↗
NASA NTRS1980

Thermal mapping, geothermal source location, natural effluents and plant stress in the Mediterranean coast of Spain

Although no significant results were achieved during the report period, research continues. A sample of imagery showing thermal inertia and temperature differences over the northeastern United States and Europe was received. The project coordinator attended a TELLUS Project meeting in Ispra, Italy at which general guidelines for the future were established and the quality of the data received was discussed.

Delascuevas, R. N.↗
NASA NTRS1981

High frequency drive mechanism for an active controls systems aircraft control surface

The mechanism was successfully utilized on a wind tunnel model tested in the transonic blow down tunnel. The mechanism is also applicable to a flying aircraft. Several interrelated mechanical subsystems were utilized, including a low inertia antibacklash drive mechanism for high frequency oscillation and a compact antibacklash drive mechanism for conversion of rotary motion to linear motion.

Smith, H. E.↗
NASA NTRS1981

Design and development of an optical scanning mechanism (OSMA) with minimum momentum transfer

The development model for an optical scanning mechanism assembly is described as being two equal inertial masses which collide with each other to minimize the momentum transfer to the satellite and other mounted instruments. The design criteria for the mirror, the compensating inertia structure and other components are given. The details of the design are discussed and related test results are presented, which show the validity of the design concept for momentum compensation.

Sainz, L. B. F.↗
NASA NTRS1981

Superrotation planetary atmospheres: Mechanical analogy, angular momentum budget and simulation of the spin up process

Superrotation rates observed in planetary atmospheres are analyzed based on the concept of a thermally driven zonally symmetric circulation. Specifically, how this superrotation is produced and maintained against the tendency for friction to oppose differential motions between the atmosphere and the underlying planet is addressed. The time evolution of a fluid leading from corotation under uniform heating to superrotation under globally nonuniform heating is simulated using a three dimensional zonally symmetric spectral model and Laplace transformation. The increased tendency toward geostrophy combined with the increase of surface pressure toward the poles (due to meridional mass transport), induces the atmosphere to subrotate temporarily at lower altitudes. The resulting viscous shear near the surface thus permits angular momentum to flow from the planet into the atmosphere where it propagates upwards and, combined with the change in moment of inertia, produces large superrotation rates at higher viscosities.

Mayr, H. G.↗
NASA NTRS1980

A consistent set of trial functions for conical shells

A consistent approach is developed for the determination of trial functions for a class of shells of revolution. The trial functions satisfy the in-plane and out-of-plane boundary conditions at the shell ends and include the effects of tangential inertia. The resulting expressions converge rapidly for the problem of linear free vibration

El-Raheb, M.↗
NASA NTRS1981

Geologic remote sensing

Remote-sensing techniques based on the analysis of spectral reflectance, spectral emittance, thermal inertia, and radar measurements are reviewed. Specific applications of Landsat multispectral scanner are examined with emphasis on mineral exploration. The potential of satellite systems for detailed lithologic mapping is pointed out.

Goetz, A. F. H.↗
NASA NTRS1981

Stability theorems for multidimensional linear systems with variable parameters

A Liapunov-type approach is used to derive two equivalent theorems which govern the stability of coupled linear systems with varying multiple parameters. The theorems generalize some of the existing theorems applicable to systems with constant parameters and the Sonin-Polya theorem applicable to a single-degree-of-freedom system with variable coefficients. As an illustration, the proposed theorems are applied to mechanical systems with varying inertia, stiffness, gyroscopic, and damping terms, and velocity and position-dependent forces.

Shrivastava, S. K.↗
NASA NTRS1980

Io - Observational constraints on internal energy and thermophysics of the surface

Infrared observations of the Io eclipse of April 12, 1980, in five broad bands from 3 to 30 microns define the thermal emission spectrum both during and after eclipse. A substantial fraction of the emitted radiation during eclipse arises from hot spots; the equivalent global average heat flow is 1.5 + or - 0.3 W/sq m, corresponding to an internal source of (6 + or - 1) x 10 to the 13th W. The hot spot spectra can be matched by components with color temperatures of 200-600 K covering 1-2% of the surface. Comparison with observations over the past eight years suggests that, while the flux at the hottest temperatures may be highly variable, there is no evidence for major changes in the total heat flow, which is emitted primarily in the spectral region 10-20 microns. The heating curves of the surface were observed at 10 and 20 microns; when corrected for the hot spot contribution they indicate a typical global thermal inertia for Io of 0.0002 + or - 0.0001 cal/sq cm sec(exp 1/2) K, similar to that of the other Galilean satellites.

Morrison, D.↗
NASA NTRS1981

Density of the mantle of Mars

The range of zero pressure densities of the Martian mantle which are compatible with the mean density and moment of inertia factor of Mars has been explored by: (1) considering the full range of plausible core compositions and densities, and (2) investigating the sensitivity of computed mantle densities to uncertainties in the input parameters. Ni, Fe, Fe3O4, and FeS cores were considered; corresponding zero pressure mantle densities range from 3.47 to 3.41 g/cu cm. Uncertainty in the mantle density of about 0.04 g/cu cm for the Fe core model and about 0.05 g/cu cm for the FeS core model results from uncertainties in the input parameters. The zero pressure density of the Martian mantle is estimated to be 3.44 plus or minus 0.06 g/cu cm.

Goettel, K. A.↗
NASA NTRS1980

Super-size space telescope

A class of space telescopes for astronomical observations with a resolution and collecting capability more than one order of magnitude better than what is expected from the 2.4 m Space Telescope is discussed. To this purpose aplanatic two-mirror systems of coplanar primary/secondary mirror arrangements with approximately 45 deg angles of incidence and an overall diameter of about 100 m have been designed and analyzed. The main advantages of these systems are their compactness and the associated minimization of the moment of inertia in two axes. Two opposing secondary arrangements, one forward-reflecting and the other backward-reflecting are analyzed and compared.

Korsch, D.↗
NASA NTRS1981

Short period tidal variations of earth rotation

It is explained that the tidal deformation of the earth's polar moment of inertia by the moon and sun cause periodic variations in rotation. The short period oscillations give rise to a meter-sized, diurnal signature in the lunar laser ranging data obtained at McDonald Observatory. A solution is given for the scale parameter k/C at fortnightly and monthly tidal frequencies. The results are compared with those obtained by other investigators and with a theoretical estimate which includes the effect of oceans and a decoupled fluid core.

Yoder, C. F.↗
NASA NTRS1981

Jupiter - Structure and composition of the upper atmosphere

The Voyager ultraviolet stellar occultation data yield a temperature of 200 + or - 50 K at about 400 km, and the solar occultation data give 1100 + or - 200 K at 1450 km above the ammonia cloud tops. The temperature gradient between 400 and 1450 km is approximately 1 K/km. The mesospheric temperature structure gives no strong indication of an earth-like mesopause. The heating of the upper atmosphere appears to result from a combination of magnetospheric charged particle precipitation, ion drag, inertia gravity waves, and solar EUV. The volume mixing ratios of CH4 and C2H6 at 325 km are measured to be 2.5(+3, -2) x 10 to the -5th and 2.5(+2.0, -1.5) x 10 to the -6th, respectively, which are lower than in the stratosphere. The C2H2 volume mixing ratio is not greater than 5 x 10 to the -6th at 300 km. The homopause value of the equatorial eddy diffusion coefficient is found to be 1-2 x 10 to the -6th sq cm/s.

Atreya, S. K.↗
NASA NTRS1981

The dynamics of large flexible earth pointing structures with a hybrid control system

The dynamics and control of large flexible structures nominally oriented along the local horizontal are analyzed. Orientation and shape control is assumed to be provided by a hybrid system consisting of a passive spring loaded gimballed dumbbell damper in addition to active point thrusters. In addition to the passive damping capability, the dumbbell, through attachment at the center of mass of the main structure, also provides a favorable composite moment of inertia ratio required for gravitational stabilization. The hybrid system is seen to generally result in improved transient responses to initial perturbations in orientation and modal shape functions, while requiring less force impulse than that for the active system operating alone.

Bainum, P. M.↗