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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 793 records · Page 44

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NASA NTRS1979

Satellite-aided mobile radio concepts study: Concept definition of a satellite-aided mobile and personal radio communication system

The satellite system requires the use of a large satellite antenna and spacecraft array power of about 12 kW or more depending on the operating frequency. Technology developments needed include large offset reflector multibeam antennas, satellite electrical power sybsystems providing greater than 12 kW of power, signal switching hardware, and linearized efficient solid state amplifiers for the satellite-aided mobile band. Presently there is no frequency assignment for this service, and it is recommended that an allocation be pursued. The satellite system appears to be within reasonable extrapolation of the state of the art. It is further recommended that the satellite-aided system spacecraft definition studies and supporting technology development be initiated.

Anderson, R. E.↗

NASA NTRS1981

Synchrotron emissivity from mildly relativistic particles

Approximate analytic expressions are presented for evaluation of the frequency and angular dependence of synchrotron emissivity from mildly relativistic particles with arbitrary energy spectrum and pitch angle distribution in a given magnetic field. Results agree with previous expressions for a nonrelativistic Maxwellian particle distribution, and when extrapolated to nonrelativistic and extreme relativistic regimes, they also agree with the previous expressions obtained under those limiting conditions. The results from the analytic expression are compared with results from detailed numerical evaluations. Excellent agreement is found not only at frequencies large compared to the gyro-frequency but also at lower frequencies, in fact, all the way down to the gyro-frequency, where the analytic approximations are expected to be less accurate.

Petrosian, V.↗

NASA NTRS1976

Dust content and particle release experiments

Since dust particles are carried away from a comet nucleus by sublimating ices the effects from the ambient Earth's atmosphere on shuttle-based simulation experiments at lower altitudes are of the same concern to the studies of the dust behavior as they are to the investigation of the volatile component. Also, since the experimental modeling could realistically be performed on a linear scale that is at least three orders of magnitude smaller than required by the true conditions in comets, severe problems of extrapolation may arise in the interpretation of some of the simulation results. Subject to these limitations, future dust-release experiments made on artificial comets could prove fruitful, as they would test the correctness of the understanding of the fundamental properties of the dust emission mechanism in comets, and at the same time insight into the behavior of dust particles after expulsion would be gained.

Sekanina, Z.↗

NASA NTRS1980

Solar energy system economic evaluation: Fern Tunkhannock, Tunkhannock, Pennsylvania

The economic performance of an Operational Test Site (OTS) is described. The long term economic performance of the system at its installation site and extrapolation to four additional selected locations to demonstrate the viability of the design over a broad range of environmental and economic conditions is reported. Topics discussed are: system description, study approach, economic analysis and system optimization, and technical and economical results of analysis. Data for the economic analysis are generated through evaluation of the OTS. The simulation is based on the technical results of the seasonal report simulation. In addition localized and standard economic parameters are used for economic analysis.

Source record↗

NASA NTRS1980

The helium abundance of Jupiter from Voyager

Full disk measurements recorded 31 days before the Voyager 1 encounter with Jupiter by the radiometer of the infrared instrument, IRIS, indicate a geometric albedo of 0.274 + or - 0.013. Combining this measurement with the Pioneer derived phase integral of 1.25 and our error estimate of 0.1 yields a Jovian Bond albedo of 0.343 + or - 0.032. Infrared spectra recorded at the same time by the Michelson interferometer, along with a model extrapolation to low wave numbers not covered by the instrument, yield a thermal emission of (1.359 + or - 0.014) .001 W cm to the (-2) power. As in the case of the albedo measurement, the quoted errors in the emission measurement reflect estimates of systematic effects and are uncertain while the random component is negligible. From these measurements the internal heat flux of Jupiter is estimated to be (5.444 + or - 0.425) .0001 W cm to the (-2) power, and the energy balance defined as the ratio of emitted thermal to absorbed solar energy is 1.668 + or - 0.085.

Gautier, D.↗

NASA NTRS1981

High temperature alkali corrosion in high velocity gases

The effects of potential impurities in coal derived liquids such as Na, K, Mg, Ca and Cl on the accelerated corrosion of IN-100, U-700, IN-792 and Mar-M509 were investigated using a Mach 0.3 burner rig for times to 1000 hours in one hour cycles. These impurities were injected in combination as aqueous solutions into the combustor of the burner rig. The experimental matrix utilized was designed statistically. The extent of corrosion was determined by metal recession. The metal recession data were fitted by linear regression to a polynomial expression which allows both interpolation and extrapolation of the data. As anticipated, corrosion increased rapidly with Na and K, and a marked maximum in the temperature response was noted for many conditions. In contrast, corrosion decreased somewhat as the Ca, Mg and Cl contents increased. Extensive corrosion was observed at concentrations of Na and K as low as 0.1 PPM at long times.

Lowell, C. E.↗

NASA NTRS1981

Sensitivity of optimum solutions to problem parameters

Derivation of the sensitivity equations that yield the sensitivity derivatives directly, which avoids the costly and inaccurate perturb-and-reoptimize approach, is discussed and solvability of the equations is examined. The equations apply to optimum solutions obtained by direct search methods as well as those generated by procedures of the sequential unconstrained minimization technique class. Applications are discussed for the use of the sensitivity derivatives in extrapolation of the optimal objective function and design variable values for incremented parameters, optimization with multiple objectives, and decomposition of large optimization problems.

Sobieszczanski-Sobieski, J.↗

NASA NTRS1981

Simultaneous observations of active galactic nuclei with IUE

The IUE observations of four active nuclei were coordinated with radio, infrared, and X-ray measurements to obtain simultaneous determinations of their continuous spectra. The results for the BL Lac objects 0735+178 and I Zw 187 indicate sufficient UV and X-ray fluxes to ionize any gas. Comparison of the X-ray measurements with the extrapolated optical UV continuum show a definite X-ray excess for I Zw 187 but none for the other BL Lac object.

Bregman, J. N.↗

NASA NTRS1981

Cometary particulate analyzer design definition study

A concept for remotely determining the relative abundance of elements contained in cometary particulates collected by a spacecraft was conducted with very encouraging results. The technique utilizes a short high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser-produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. A prototype analyzer system was designed, constructed, and tested. Results show that: (1) energy-time focus performs as predicted in improving resolution; (2) power densities sufficient to produce usable ionization efficiencies can be obtained; (3) complex alloys such as stainless steel can be analyzed; and (4) a tiny, simple and reliable laser used in the demonstration easily meets spacecraft power and mass limitations. A mass resolution of 150 was experimentally demonstrated at mass 108, and an analytical extrapolation predicts a resolution sufficient to separate masses 250 and 251.

Utterback, N. G.↗

NASA NTRS1981

Structural analysis of cylindrical thrust chambers, volume 3

A system of three computer programs is described for use in conjunction with the BOPAGE finite element program. The programs are demonstrated by analyzing cumulative plastic deformation in a regeneratively cooled rocket thrust chamber. The codes provide the capability to predict geometric and material nonlinear behavior of cyclically loaded structures without performing a cycle-by-cycle analysis over the life of the structure. The program set consists of a BOPACE restart tape reader routine, and extrapolation program and a plot package.

Pearson, M. L.↗

NASA NTRS1981

Radio frequency interference at the geostationary orbit

Growing demands on the frequency spectrum have increased the possibility of radio frequency interference (RFI). Various approaches to obtain in orbit RFI data are compared; this comparision indicates that the most practical way to obtain RFI data for a desired orbit (such as a geostationary orbit) is through the extrapolation of in orbit RFI measurements by a low orbit satellite. It is concluded that a coherent RFI program that uses both experimental data and analytical predictions provides accurate RFI data at minimal cost.

Sue, M. K.↗

NASA NTRS1981

Comparison of three thrust calculation methods using in-flight thrust data

The gross thrust of an experimental airplane was determined by each method using the same flight maneuvers and generally the same data parameters. Coefficients determined from thrust stand calibrations for each of the three methods were then extrapolated to cruise flight conditions. The values of total aircraft gross thrust calculated by the three methods for cruise flight conditions agreed within + or - 3 percent. The disagreement in the values of thrust calculated by the different techniques manifested itself as a bias in the data. There was little scatter (0.5 percent) for the thrust levels examined in flight.

Hughes, D. L.↗

NASA NTRS1981

A Fresnel collector process heat experiment at Capitol Concrete Products

An experiment is planned, conducted and evaluated to determine the feasibility of using a Power Kinetics' Fresnel concentrator to provide process heat in an industrial environment. The plant provides process steam at 50 to 60 psig to two autoclaves for curing masonry blocks. When steam is not required, the plant preheats hot water for later use. A second system is installed at the Jet Propulsion Laboratory parabolic dish test site for hardware validation and experiment control. Experiment design allows for the extrapolation of results to varying demands for steam and hot water, and includes a consideration of some socio-technical factors such as the impact on production scheduling of diurnal variations in energy availability.

Hauger, J. S.↗

NASA NTRS1981

Characteristic boundary conditions for the Euler equations

The boundary conditions are demonstrated for the quasi-one-dimensional Euler equations with the extension to two and three dimensions being straightforward. In this application an implicit finite-difference scheme is employed with the boundary conditions being applied implicitly. The boundary application uses both characteristic extrapolations and evaluations which distinguishes it from other theories. Flow fields with shocks are calculated with inflow-outflow conditions of supersonic-subsonic and subsonic-subsonic flow.

T H Pulliam↗

NASA NTRS1981

Boundary treatments for implicit solutions to Euler and Navier-Stokes equations

It seems apparent that for inviscid calculations the differences between the explicit and implicit boundary formulations tested are far smaller than anticipated. New work should focus on understanding of how the convergence rate is limited or affected by boundary formulations. Since the inflow/outflow boundary treatments tested were simple extrapolations, it may be the case that treatments more closely representing the differential equations will prove to have superior convergence properties. However, several such improved boundary treatments were attempted with disappointing results.

Thompkins, W. T., Jr.↗

NASA NTRS1980

Nonrelativistic hyperfine splitting in muonic helium by adiabatic perturbation theory

Huang and Hughes have discussed the hyperfine splitting delta mu of muonic helium using a variational approach. In this paper, the Born-Oppenheimer approximation is used to simplify the evaluation of delta mu in the nonrelativistic limit. The first-order perturbed wave function of the electron is obtained in closed form by modifying the method used by Dalgarno and Lynn. The result is close to those of Huang and Hughes which required a large Hylleraas expansion and considerable extrapolation.

Drachman, R. J.↗

NASA NTRS1980

The elemental abundances of hydrogen through nickel in the low energy cosmic rays

The relative abundances of the elements H through Ni in the galactic cosmic rays have been measured in the energy range 70-280 MeV/nucleon with the University of Chicago cosmic ray telescope on board the satellite IMP-8 from January 1973 to September 1978. Cosmic ray source abundances have been derived by extrapolating the measured composition back to the source. A key factor in the propagation calculation is the use of a pathlength distribution and a solar modulation level shown to be consistent with the secondary to primary ratios and their energy dependence below about 1 GeV/n.

Garcia-Munoz, M.↗

NASA NTRS1980

Abundances of energy spectra of individual iron-secondary elements

Relative abundances of individual Iron-secondary elements have been measured using a balloon-borne 6.6 m ster ionization/Cerenkov detector system. The unusually large geometry factor and single-charge resolution yield empirical atmospheric attenuation curves for individual elements which combine with high statistics at float altitude to yield individual element abundances, extrapolated to the top of the atmosphere, with high precision. Results are presented for top-of-the-atmosphere abundances (relative to iron) of individual elements in the Z range 13-30.

Israel, M. H.↗