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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The aurora and the magnetosphere - The Chapman Memorial Lecture

Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

Akasofu, S.-I.↗
NASA NTRS1974

Lectures on the scattering of light

The exact (Mie) theory for the scattering of a plane wave by a dielectric sphere is presented. Since this infinite series solution is computationally impractical for large spheres, another formulation is given in terms of an integral equation valid for a bounded, but otherwise general array of scatterers. This equation is applied to the scattering by a single sphere, and several methods are suggested for approximating the scattering cross section in closed form. A tensor scattering matrix is introduced, in terms of which some general scattering theorems are derived. The application of the formalism to multiple scattering is briefly considered.

Saxon, D. S.↗
NASA NTRS1975

Planetary exploration - Earth's new horizon /Twelfth von Karman Lecture/

Planetary exploration is examined in terms of the interaction of technological growth with scientific progress and the intangibles associated with exploring the unknown. The field is limited to unmanned exploration of the planets and their satellites. A descriptive model of the endeavor, its activities and achievements in the past decade, a characterization of the current state of the art, and a look at some of the planetary mission opportunities for the next decade are presented. A case is made for the value to civilization of ongoing planetary exploration. The pioneering U.S. planetary explorers, Mars, Venus, and Jupiter, are discussed in the second part of the work. Launch velocity, navigation, the remote system, the earth base, and management technology are considered in the third part. Authorized near-term U.S. planetary projects and opportunities of the next decade are described in the last section.

Schurmeier, H. M.↗
NASA NTRS1975

X-ray astronomy in the Uhuru epoch and beyond /Newton Lacy Pierce Prize Lecture/

A review of results from the Uhuru satellite is presented. An intensive treatment of two subjects is given, rather than a broad review. First, Cyg X-1, a stellar X-ray source and a candidate for a black hole, is discussed; second, the X-ray source in the Perseus cluster of galaxies, which may be a cloud of hot intergalactic gas, is treated. In both cases, the train of logic used in establishing the nature of these objects is presented and evaluated. For both, while alternative explanations cannot be completely eliminated, they become more difficult to sustain when examined in detail, suggesting that the candidate explanations are more likely correct.

Kellogg, E. M.↗
NASA NTRS1975

Planetary exploration - Earth's new horizon /12th von Karman Lecture/

The article gives an account of the history of unmanned exploration of the planets of the solar system, including both earthbound exploration and exploration with spacecraft. Examples of images of the Martian surface are presented along with images obtained in Jupiter and Mercury flybys. Data are presented on the growth of US launch vehicle performance capability, navigation performance, and planetary data rate capability. Basic information regarding the nature of the scientific experiments aboard the Pioneer and Viking spacecraft is given. A case is put forward for the ongoing exploration of the planets as a worthwhile endeavor for man.

Schurmeier, H. M.↗
NASA NTRS1975

Apollo and the geology of the moon /Twenty-eighth William Smith Lecture/

Lunar geology evidence is examined for clues to the origin and evolution of the moon and earth. Seven evolutionary episodes, the last covering three billion years to the present day, are constructed for the moon. Parallel episodes in the earth's evolution are masked by the dynamic continuing evolution of the earth over a 4.5 billion year span, in contrast to the moon's quiescence and inability to retain fluids. Comparisons are drawn between the geochemistry and tectonics of the lunar basaltic maria and the earth's ocean basins. Lunar maria rocks differ strikingly in chemical composition from meteoritic matter and solar material. Inundation of frontside lunar maria basins by vast oceans of dark basalt mark the last of the major internally generated evolutionary episodes, and is attributed to consequences of meltdown of the lunar mantle and crust by radioisotope decay from below. Data are drawn primarily from Apollo missions 11-17, supplemented by other sources.

Schmitt, H. H.↗
NASA NTRS1975

Some considerations in the design of transport aircraft /The W. Rupert Turnbull Lecture for 1975/

The slow landing speeds (30 mph, 65 mph) and light wing loading required for safety in the early days of aviation are shown to be irrelevant to safe landings of propeller-driven aircraft, while increases in wing loading and landing speed have been accompanied by improved safety records. This is attributed to length of runway and time available for approach maneuvers, plus immunity to wind gusts and turbulence conferred by higher wing loadings. Aerodynamical and mechanical aspects of safe landing are discussed, with no mention of instruments. Fuel savings achievable through high aspect ratio, variable sweep angle, and supercritical airfoils are also considered.

Jones, R. T.↗
NASA NTRS1978

Lectures on algebraic system theory: Linear systems over rings

The presentation centers on four classes of systems that can be treated as linear systems over a ring. These are: (1) discrete-time systems over a ring of scalars such as the integers; (2) continuous-time systems containing time delays; (3) large-scale discrete-time systems; and (4) time-varying discrete-time systems.

Kamen, E. W.↗
NASA NTRS1979

Computational aerodynamics development and outlook /Dryden Lecture in Research for 1979/

Some past developments and current examples of computational aerodynamics are briefly reviewed. An assessment is made of the requirements on future computer memory and speed imposed by advanced numerical simulations, giving emphasis to the Reynolds averaged Navier-Stokes equations and to turbulent eddy simulations. Experimental scales of turbulence structure are used to determine the mesh spacings required to adequately resolve turbulent energy and shear. Assessment also is made of the changing market environment for developing future large computers, and of the projections of micro-electronics memory and logic technology that affect future computer capability. From the two assessments, estimates are formed of the future time scale in which various advanced types of aerodynamic flow simulations could become feasible. Areas of research judged especially relevant to future developments are noted.

Chapman, D. R.↗
NASA NTRS1980

The Voyager spacecraft /James Watt International Gold Medal Lecture/

The Voyager Project background is reviewed with emphasis on selected features of the Voyager spacecraft. Investigations by the Thermo-electric Outer Planets Spacecraft Project are discussed, including trajectories, design requirements, and the development of a Self Test and Repair computer, and a Computer Accessed Telemetry System. The design and configuration of the spacecraft are described, including long range communications, attitude control, solar independent power, sequencing and control data handling, and spacecraft propulsion. The development program, maintained by JPL, experienced a variety of problems such as design deficiencies, and process control and manufacturing problems. Finally, the spacecraft encounter with Jupiter is discussed, and expectations for the Saturn encounter are expressed.

Heacock, R. L.↗
NASA NTRS1981

On making things the best - Aeronautical uses of optimization /Wright Bros. lecture/

The paper's purpose is to summarize and evaluate the results of an investigation into the degree to which formal optimization methods have contributed practically to the design and operation of atmospheric flight vehicles. The nature of this technology is reviewed and illustrated with simple structural examples. A series of published successful applications is described, from the fields of aerodynamics, structures, guidance and control, optimal trajectories and vehicle configuration optimization. The corresponding improvements over conventional analysis are assessed. Speculations are offered as to why these tools have made such little headway toward acceptance by designers. The growing need for their use in the future is explained; they hold out an unparalleled opportunity for improved efficiencies.

Ashley, H.↗
NASA NTRS1983

Fluid mechanics in crystal growth - The 1982 Freeman scholar lecture

An attempt is made to unify the current state of knowledge in crystal growth techniques and fluid mechanics. After identifying important fluid dynamic problems for such representative crystal growth processes as closed tube vapor transport, open reactor vapor deposition, and the Czochralski and floating zone melt growth techniques, research results obtained to date are presented. It is noted that the major effort to date has been directed to the description of the nature and extent of bulk transport under realistic conditions, where bulk flow determines the heat and solute transport which strongly influence the temperature and concentration fields in the vicinity of the growth interface. Proper treatment of near field, or interface, problems cannot be given until the far field, or global flow, involved in a given crystal growth technique has been adequately described.

Ostrach, S.↗
NASA NTRS1983

Coronal disturbances and their terrestrial effects /Tutorial Lecture/

An assessment is undertaken of recent approaches to the prediction of the interplanetary consequences of coronal disturbances, with attention to the relationships of shocks and energetic particles to coronal transients, of proton events to gamma-ray and microwave bursts, of geomagnetic storms to filament eruptions, and of solar wind increases to the flare site magnetic field direction. A discussion is given concerning the novel phenomenon of transient coronal holes, which appear astride the long decay enhancements of 2-50 A X-ray emission following H-alpha filament eruptions. These voids in the corona are similar to long-lived coronal holes, which are the sources of high speed solar wind streams. The transient coronal holes may also be associated with transient solar wind speed increases.

Rust, D. M.↗
NASA NTRS1983

Upstream waves and particles /Tutorial Lecture/

The plasma waves, MHD waves, energetic electrons and ions associated with the proximity of the region upstream from terrestrial, planetary and interplanetary shocks are discussed in view of observations and current theories concerning their origin. These waves cannot be separated from the study of shock structure. Since the shocks are supersonic, they continually overtake any ULF waves created in the plasma in front of the shock. The upstream particles and waves are also of intrinsic interest because they provide a plasma laboratory for the study of wave-particle interactions in a plasma which, at least at the earth, is accessible to sophisticated probing. Insight may be gained into interstellar medium cosmic ray acceleration through the study of these phenomena.

Russell, C. T.↗
NASA NTRS1983

Three Lectures on Theorem-proving and Program Verification

Topics concerning theorem proving and program verification are discussed with particlar emphasis on the Boyer/Moore theorem prover, and approaches to program verification such as the functional and interpreter methods and the inductive assertion approach. A history of the discipline and specific program examples are included.

Moore, J. S.↗