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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Satellite broadcasting system study

The study to develop a system model and computer program representative of broadcasting satellite systems employing community-type receiving terminals is reported. The program provides a user-oriented tool for evaluating performance/cost tradeoffs, synthesizing minimum cost systems for a given set of system requirements, and performing sensitivity analyses to identify critical parameters and technology. The performance/ costing philosophy and what is meant by a minimum cost system is shown graphically. Topics discussed include: main line control program, ground segment model, space segment model, cost models and launch vehicle selection. Several examples of minimum cost systems resulting from the computer program are presented. A listing of the computer program is also included.

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NASA NTRS1973

Orientation-dependent effects in Oort's theory of comet origin. II - Anisotropies in the distribution of long-period comet orbits.

The statistical significance of anisotropies in the distribution of orbital orientations among the long-period and nearly parabolic comets is evaluated. It is suggested that these anisotropies are not the result of observational selection effects. A numerical model for the distribution of orbital orientations is constructed, based on Oort's theory of comet origin and the assumption that the observed anisotropies are caused by multiple planetary perturbations over the course of many perihelion passages. The model, which is restricted to comets with perihelion distances less than 0.3 AU, does not predict any significant anisotropies.

Joss, P. C.↗
NASA NTRS1974

Ablative thermal protection for space tug multipass, aerobraking entry

Analytical studies had found the employment of an aerobraking trajectory for return of a reusable Space Tug from geosynchronous missions to be feasible and practical. To establish the minimum-weight ablative dome heat shield, trajectories involving 2 and 30 perigee passes were investigated both analytically and by plasma arc testing. Silicone-base ablators with densities of 15, 30, and 50 lb/cu ft were selected for evaluation. All models withstood the multipass exposures without deleterius surface recession or char erosion. Dome heat shield weights based on optimum ablative compositions indicated that ablators are a highly efficient thermal protection system for these missions.

Strauss, E. L.↗
NASA NTRS1975

Studies in the demand for short haul air transportation

Demand is analyzed in a short haul air transportation corridor. Emphasis is placed on traveler selection from available routes. Model formulations, estimation techniques, and traffic data handling are included.

Kanafani, A.↗
NASA NTRS1976

Definition study for photovoltaic residential prototype system

A site evaluation was performed to assess the relative merits of different regions of the country in terms of the suitability for experimental photovoltaic powered residences. Eight sites were selected based on evaluation criteria which included population, photovoltaic systems performance and the cost of electrical energy. A parametric sensitivity analysis was performed for four selected site locations. Analytical models were developed for four different power system implementation approaches. Using the model which represents a direct (or float) charge system implementation the performance sensitivity to the following parameter variations is reported: (1) solar roof slope angle; (2) ratio of the number of series cells in the solar array to the number of series cells in the lead-acid battery; and (3) battery size. For a Cleveland site location, a system with no on site energy storage and with a maximum power tracking inverter which feeds back excess power to the utility was shown to have 19 percent greater net system output than the second place system. The experiment test plan is described. The load control and data acquisition system and the data display panel for the residence are discussed.

Shepard, N. F.↗
NASA NTRS1977

The Potential for Helicopter Passenger Service in Major Urban Areas

An interurban helicopter cost model having the capability of selecting an efficient helicopter network for a given city in terms of service and total operating costs was developed. This model which is based upon the relationship between total and direct operating costs and the number of block hours of helicopter operation is compiled in terms of a computer program which simulates the operation of an intracity helicopter fleet over a given network. When applied to specific urban areas, the model produces results in terms of a break-even air passenger market penetration rate, which is the percent of the air travelers in each of those areas that must patronize the helicopter network to make it break even commercially. A total of twenty major metropolitan areas are analyzed and are ranked initially according to cost per seat mile and then according to break-even penetration rate.

Dajani, J. S.↗
NASA NTRS1977

Low-profile heliostat design for solar central receiver systems

Heliostat designs intended to reduce costs and the effect of adverse wind loads on the devices were developed. Included was the low-profile heliostat consisting of a stiff frame with sectional focusing reflectors coupled together to turn as a unit. The entire frame is arranged to turn angularly about a center point. The ability of the heliostat to rotate about both the vertical and horizontal axes permits a central computer control system to continuously aim the sun's reflection onto a selected target. An engineering model of the basic device was built and is being tested. Control and mirror parameters, such as roughness and need for fine aiming, are being studied. The fabrication of these prototypes is in process. The model was also designed to test mirror focusing techniques, heliostat geometry, mechanical functioning, and tracking control. The model can be easily relocated to test mirror imaging on a tower from various directions. In addition to steering and aiming studies, the tests include the effects of temperature changes, wind gusting and weathering. The results of economic studies on this heliostat are also presented.

Fourakis, E.↗
NASA NTRS1979

Plotting max/min data envelopes

Study of maximum and minimum load distributions along structural section is aided by visual display of load distribution data. Maximum/minimum envelope plot program plots these envelopes of the stresses and shear loads at selected points in beam modeled by series of finite elements. Digital output for engineers and management is presented for quick analysis and understanding.

Furuike, T.↗
NASA NTRS1978

Reference aircraft for ICAO Working Group E

The results of an advanced supersonic transport aircraft/engine integration study to be used as a detail preliminary design case to assist in the assessment of noise standards applicable to future supersonic transports are summarized. The design considered reflects the application of the advanced technologies which are projected to be available for program initiation in the 1980-1985 time period. Suppression characteristics included were obtained in simulated forward flight in the Rolls-Royce spin rig using a small scale model. The engine size selected produces a noise no greater than 108 EPNdB at any of the three Far Part 36 (Stage 2) defined measuring points and is sized slightly larger than the optimum cruise size to meet this noise constraint condition.

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NASA NTRS1978

Cloudiness and the radiation budget

The problem of obtaining data for quantification of the effects of clouds on radiation budget measurements is discussed. Areas considered include the relationship between observed cloud characteristics and model predicted characteristics and selection of an angular distribution function for conversion of scanning radiometer radiance to irradiance. Storage of meteorological satellite data related to cloud-radiation interactions is discussed.

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NASA NTRS1980

On the performance of explicit and implicit algorithms for transient thermal analysis

The status of an effort to increase the efficiency of calculating transient temperature fields in complex aerospace vehicle structures is described. The advantages and disadvantages of explicit and implicit algorithms are discussed. A promising set of implicit algorithms, known as the GEAR package is described. Four test problems, used for evaluating and comparing various algorithms, have been selected and finite element models of the configurations are discribed. These problems include a space shuttle frame component, an insulated cylinder, a metallic panel for a thermal protection system and a model of the space shuttle orbiter wing. Calculations were carried out using the SPAR finite element program, the MITAS lumped parameter program and a special purpose finite element program incorporating the GEAR algorithms. Results generally indicate a preference for implicit over explicit algorithms for solution of transient structural heat transfer problems when the governing equations are stiff. Careful attention to modeling detail such as avoiding thin or short high-conducting elements can sometimes reduce the stiffness to the extent that explicit methods become advantageous.

Adelman, H. M.↗
NASA NTRS1980

Developing the concept of a geostationary platform

A geostationary platform concept with a proliferation of low-cost earth stations is discussed. Candidate platform concepts, servicing, life, and Orbital Transfer Vehicle (OTV) options are considered. A Life Cycle Costing model is used to select the minimum cost concept meeting program criteria. It is concluded that the geostationary platform concept is a practical and economical approach to providing expanding communication services within the limitations imposed by the available frequency spectrum and orbital arc.

Carey, W. T.↗
NASA NTRS1981

Decision Aids for Airborne Intercept Operations in Advanced Aircrafts

A tactical decision aid (TDA) for the F-14 aircrew, i.e., the naval flight officer and pilot, in conducting a multitarget attack during the performance of a Combat Air Patrol (CAP) role is presented. The TDA employs hierarchical multiattribute utility models for characterizing mission objectives in operationally measurable terms, rule based AI-models for tactical posture selection, and fast time simulation for maneuver consequence prediction. The TDA makes aspect maneuver recommendations, selects and displays the optimum mission posture, evaluates attackable and potentially attackable subsets, and recommends the 'best' attackable subset along with the required course perturbation.

Madni, A.↗
NASA NTRS1981

Effect of polynucleotides on the dimerization of glycine

Results from experiments to determine the effect of polynucleotides on abiological formation of peptide bonds are reported. The reaction between glycine molecules in an aqueous phase in the presence of a condensing agent was chosen as a model, with polyphosphates being selected as the condensing agent for biologically relevant peptide formation. Four types of polynucleotides were used: polygluanic acid (G), polyuridic acid (U), polyadenylic acid (A), and polycytidylic acid (C); the effects of small anions, acetate, chloride, and phosphate, were also studied. Procedures are given, including concentrations, pH, and incubation time, and the type of amino acid analyzer. The diglycine yields were, in order of most to least: G, C, A, U, and are diagrammed as a function of time; rate of formation followed the same order of magnitude as the final yields. Anion presence displayed no discernible effect. The results are taken to indicate that polynucleotides do have an effect on the formation of peptide bonds, an effect significant in the understanding of chemical evolution.

Mizutani, H.↗
NASA NTRS1981

NASA LeRC/Akron University Graduate Cooperative Fellowship Program and Graduate Student Researchers Program

The requisite methodology to solve linear and nonlinear problems associated with the static and dynamic analysis of rotating machinery, their static and dynamic behavior, and the interaction between the rotating and nonrotating parts of an engine is developed. Linear and nonlinear structural engine problems are investigated by developing solution strategies and interactive computational methods whereby the man and computer can communicate directly in making analysis decisions. Representative examples include modifying structural models, changing material, parameters, selecting analysis options and coupling with interactive graphical display for pre- and postprocessing capability.

Fertis, D. G.↗
NASA NTRS1984

Regularized Monte-Carlo calculations of the optical polarization induced by scattering in X-ray binaries

The results of regularized Monte Carlo calculations of the optical polarization Stokes parameters expected as a result of scattering from gas streams or accretion wakes in close binary systems whose properties resemble those of X-ray binaries are presented. The physical processes occurring in the system are represented by a model which follows a selected sample of individual photon paths from each emitting element on the surface of the primary to the photon's detection at earth. The result represents the variations in the intensity from each individual emitting element caused by the effects of limb darkening, gravity darkening, and variation in the projected area of the emitting element as seen from the scattering element.

Dolan, J. F.↗
NASA NTRS1985

Free-tip-rotor wind-tunnel test results

Seven controller mechanisms and several tip geometries were proposed and evaluated in the course of a free tip rotor development program which integrated those components into a model rotor system for wind tunnel testing. After a rigid whirl test was run to determine controller mechanism performance and structural integrity, a second whirl test was performed with a model rotor incorporating a selected controller design and a selected tip platform to determine the transient behavior of the tips in response to aerodynamic excitation. The results obtained demonstrate that a swept, tapered tip with a tension-torsion strap controller furnished satisfactory mechanical operation, achieved the specified output torque, possessed a low spring rate, and had fast and stable response to excitation.

Stroub, R. H.↗