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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The critical velocity phenomenon and the origin of the regular satellites

A theory is developed for the formation of the satellite systems which are likely to have been formed in situ, that is, not by capture of the satellite by the central planet. The foundation of the theory is the observation of the similarity between the band structure of such satellites and the band structure of cosmically abundant elements. That means that the values of the quantity log Gamma, where Gamma is the ratio of the mass of the central body to the orbital radius of the secondary body, are grouped into three bands which can be identified with the three bands into which are grouped the values of the ratio of the mass of a central body to the distance at which the kinetic energy of a freely falling cloud of atoms of a given kind equals the ionization energy. A coherent series of processes that could have led to the formation of satellites is outlined. The theory is valid also for planets, since the above-mentioned band structure is noted for the sun-planets system also.

De, B. R.↗
NASA NTRS1978

Effects of rotor location, coning, and tilt on critical loads in large wind turbines

Several large (1500 kW) horizontal rotor configurations were analyzed to determine the effects on dynamic loads of upwind downwind rotor locations, coned and radial blade positions, and tilted and horizontal rotor axis positions. Loads were calculated for a range of wind velocities at three locations in the structure: (1) the blade shank; (2) the hub shaft; and (3) the yaw drive. Blade axis coning and rotor axis tilt were found to have minor effects on loads. However, locating the rotor upwind of the tower significantly reduced loads at all locations analyzed.

Spera, D. A.↗
NASA NTRS1978

A critical evaluation of the predictions of the NASA-Lockheed multielement airfoil computer program

Theoretical predictions of several versions of the multielement airfoil computer program are evaluated. The computed results are compared with experimental high lift data of general aviation airfoils with a single trailing edge flap, and of airfoils with a leading edge flap and double slotted trailing edge flaps. Theoretical and experimental data include lift, pitching moment, profile drag and surface pressure distributions, boundary layer integral parameters, skin friction coefficients, and velocity profiles.

Brune, G. W.↗
NASA NTRS1978

Grain formation in astronomical systems: A critical review of condensation processes

An analysis is presented of the assumption and the applicability of the three theoretical methods for calculating condensations in cosmic clouds where no pre-existing nuclei exist. The three procedures are: thermodynamic equilibrium calculations, nucleation theory, and a kinetic treatment which would take into account the characteristics of each individual collision. Thermodynamics provide detailed results on the composition temperature and composition of the condensate provided the system attains equilibrium. Because of the cosmic abundance mixture of elements, large supersaturations in some cases and low pressures, equilibrium is not expected in astronomical clouds. Nucleation theory, a combination of thermodynamics and kinetics, has the limitations of each scheme. Kinetics, not requiring equilibrium, avoids nearly all the thermodynamics difficulties but requires detailed knowledge of many reactions which thermodynamics avoids. It appears to be the only valid way to treat grain formation in space. A review of experimental studies is given.

Donn, B.↗
NASA NTRS1978

Critical review of Ames Life Science participation in Spacelab Mission Development Test 3: The SMD 3 management study

A management study was conducted to specify activities and problems encountered during the development of procedures for documentation and crew training on experiments, as well as during the design, integration, and delivery of a life sciences experiment payload to Johnson Space Center for a 7 day simulation of a Spacelab mission. Conclusions and recommendations to project management for current and future Ames' life sciences projects are included. Broader issues relevant to the conduct of future scientific missions under the constraints imposed by the environment of space are also addressed.

Helmreich, R.↗
NASA NTRS1978

Some flow phenomena in a constant area duct with a Borda type inlet including the critical region

Mass limiting flow characteristics for a 55 L/D tube with a Borda type inlet were assessed over large ranges of temperature and pressure, using fluid nitrogen. Under certain conditions, separation and pressure drop at the inlet was sufficiently strong to permit partial vaporization and the remaining fluid flowed through the tube as if it were a free jet. An empirical relation was determined which defines conditions under which this type of flow can occur. A flow coefficient is presented which enables estimations of flow rates over the experimental range. A flow rate stagnation pressure map for selected stagnation isotherms and pressure profiles document these flow phenomena.

Hendricks, R. C.↗
NASA NTRS1978

A critical review of the state of foreign space technology

A conference was held to exchange technical information in the area of space technology. Soviet system capability and technology both in Intersputnik and in the domestic Ekran system was discussed in detail. The thermonic power conversion system used in the Soviet Topaz nuclear power reactor was described in detail. Other areas of examination included: (1) Bioastronautics; (2) Space based industry; (3) Propulsion; (4) Astrodynamics; (5) Contact with extraterrestrial intelligence; and (6) Space rescue and safety.

Grey, J.↗
NASA NTRS1977

A critical evaluation of the application of amino acid racemization to geochronology and geothermometry

Attempts have been made to determine the age of biological samples by measuring the racemization of amino acids in protein samples. The pitfalls and inherent complications in diagenetic racemization studies are reviewed, and recent advances in improving techniques are outlined. Methodological topics include isolation of amino acids from geological samples, resolution of amino acid enantiomers, and the effects of acid hydrolysis. The theory and kinetics of amino acid racemization are discussed with attention to the derivation of the rate expression for amino acid racemization, isoleucine and the equilibrium constant, the mechanism of amino acid racemization, the racemization of 'bound' versus 'free' amino acids, and factors affecting the racemization rates of free amino acids in aqueous solution. Applications of amino acid racemization kinetics to geochronology is considered with reference to shells, marine sediments, and bones. Potential complications include heating and diagenesis, diagenetic formation of amino acids, the effect of clays, species effect, and contamination.

Williams, K. M.↗
NASA NTRS1977

Effects of rotor location, coning, and tilt on critical loads in large wind turbines

Three large (1500 kW) horizontal rotor configurations were analyzed to determine the effects on dynamic loads of upwind and downwind rotor locations, coned and radial blade positions, and tilted and horizontal rotor axis positions. Loads were calculated for a range of wind velocities at three locations in the structure: the blade shank, the hub shaft, and the yaw drive. Blade axis coning and rotor axis tilt were found to have little effect on loads. However, locating the rotor upwind of the tower significantly reduced loads at all locations analyzed.

Spera, D. A.↗
NASA NTRS1978

Temporal and latitudinal variations of stratospheric trace gases - A critical comparison between theory and experiment

Global calculations of stratospheric HOx, Clx, and NOx are presented which include the effects of planetary albedo and diurnal and seasonal variations of the insolation. Comparisons are made with a wide range of atmospheric measurements at different latitudes and altitudes. Agreement between theory and observations is generally within a factor of 2. The theory appears to explain adequately the major features of latitude and seasonal distributions of NO2 and HNO3. The results indicate that mesospheric OH makes an appreciable contribution to the total OH column abundance and strongly suggest that nitrogen oxides exist principally in the form of HNO3 at high latitudes in winter. There are difficulties in reconciling OH, ClO, and O3 observations in the upper stratosphere.

Wofsy, S. C.↗
NASA NTRS1978

A critical review of the state of foreign space technology

Scientific and technical capabilities of foreign nations, i.e., USSR, Japan, West Germany, UK, France, and other ESA nations, are reviewed. Attention is given to areas in which these nations are concentrating their efforts, as well as to areas in which achievements have already been realized. Among them: space industry and processing (including nonterrestrial mining), communications satellite technology, life support systems and space colonies, earth observation, space-borne astronomy and unmanned planetary probes, materials and propulsion, and exobiology (CETI/SETI).

Grey, J.↗
NASA NTRS1978

A critical examination of expansion tunnel performance

An experimental study of the performance of the expansion tunnel for various test gases and range of quiescent acceleration section and nozzle pressure, nozzle geometric area ratio, and nozzle axial station has been performed. Flow diagnostics used to examine expansion tunnel flow characteristics were time histories and profiles of pitot pressure and axial component of flow velocity. The purpose of this study was to determine experimentally what limitations might restrict predicted operational flexibility and the advantages and disadvantages of this mode of operation as compared to the expansion tube. Results are presented which demonstrate the expansion tunnel offers several advantages over the expansion tube, but the severity of the disadvantages of the tunnel makes the expansion tube mode of operation the more desirable for performing hypersonic-hypervelocity aerothermodynamic studies of proposed entry configurations.

Miller, C. G.↗
NASA NTRS1978

Critical study of higher order numerical methods for solving the boundary-layer equations

A fourth order box method is presented for calculating numerical solutions to parabolic, partial differential equations in two variables or ordinary differential equations. The method, which is the natural extension of the second order box scheme to fourth order, was demonstrated with application to the incompressible, laminar and turbulent, boundary layer equations. The efficiency of the present method is compared with two point and three point higher order methods, namely, the Keller box scheme with Richardson extrapolation, the method of deferred corrections, a three point spline method, and a modified finite element method. For equivalent accuracy, numerical results show the present method to be more efficient than higher order methods for both laminar and turbulent flows.

Wornom, S. F.↗
NASA NTRS1978

Critical inclinations in satellite theory

The main problem of satellite theory is described in polar coordinates by a Hamiltonian function. It is proposed to find a solution of the Hamiltonian function with the following properties: (1) the reference orbit is Keplerian; (2) no restriction is imposed on the eccentricity; in particular, it is exempt of singularities - real or apparent - for small eccentricities; and (3) no restriction is imposed on the inclination; in particular, it is exempt of singularities - real or apparent - for small inclinations; also it is valid even in the neighborhood of inclinations at which the perigee is stationary.

Deprit, A.↗
NASA NTRS1979

A critical review of the life sciences project management at Ames Research Center for the Spacelab Mission development test 3

A management study was initiated by ARC (Ames Research Center) to specify Spacelab Mission Development Test 3 activities and problems. This report documents the problems encountered and provides conclusions and recommendations to project management for current and future ARC life sciences projects. An executive summary of the conclusions and recommendations is provided. The report also addresses broader issues relevant to the conduct of future scientific missions under the constraints imposed by the space environment.

Helmreich, R. L.↗