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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Analysis of space tug operating techniques. Volume 2: Study results

The design requirements for space tug systems and cost analysis of the refurbishment phases are discussed. The vehicle is an integral propulsion stage using liquid hydrogen and liquid oxygen as propellants and is capable of operating either as a fully or a partially autonomous vehicle. Structural features are an integral liquid hydrogen tank, a liquid oxygen tank, a meteoroid shield, an aft conical docking and structural support ring, and a staged combustion main engine. The vehicle is constructed of major modules for ease of maintenance. Line drawings and block diagrams are included to explain the maintenance requirements for the subsystems.

Source record↗
NASA NTRS1978

Influence of wave dispersion on vortex pairing in a jet

The geometry of large-scale structures in the turbulent mixing layer of a moderate Reynolds number jet is deduced from measurements of the fluctuating pressure in the hydrodynamic near field. The structures are rings of concentrated vorticity that distort with downstream distance until statistical axisymmetry disappears. The rings are spaced quasi-periodically and coalesce with each other, producing larger spacings. Statistical and flow-visualization techniques are applied to free and forced jets over a range of Reynolds numbers from 5000 to 50,000 to demonstrate that rings of a given spacing do not coalesce with each other until they are far enough downstream that the local mixing layer has attained some critical thickness which scales with the wavelength of the vortex pair. Wave dispersion is evaluated as a plausible mechanism for localizing the coalescences. The central feature of the model is the observation that a shear layer is dispersive to wavelengths much longer than its thickness and nondispersive to shorter waves.

Petersen, R. A.↗
NASA NTRS1983

The evolution of spokes in Saturn's B ring

Three types of Saturnian ring spoke structure have been observed which are distinguished by their optical appearance. Extended spokes are found inside the corotation radius. They are of irregular shape, with diffuse edges, but often narrowed at large distances. Their width at the base is typically 20,000 km, and their radial extent is 8000 km. The random velocity of their particles is about 2 m/s, and the total kinetic energy of their random velocity component is about 20 billion J. Narrow spokes are observed to cross the corotation distance and are characterized by high-contrast edges. Their number of particles and total energy content are about 10 percent of the values for extended spokes. Filamentary spokes are observed outside approximately 110,000 km and are usually connected to narrow or extended spokes further in. Their width is typically 500 km and their length is about 3000 km. Their number of particles and total energy content are about 0.5 percent of those of an extended spoke.

Gruen, E.↗
NASA NTRS1983

The rings of Uranus - Occultation profiles from three observatories

Occultation profiles for the nine confirmed Uranian rings obtained from Las Campanas, the European Southern Observatory, and Cerro Tololo on 15-16 August 1980 are compared. The alpha ring shows a 'double-dip' structure; the eta ring shows a broad and narrow component (similar to Saturn's F ring); and the epsilon ring shows six features that appear in the data from all three observatories. Diffraction fringes appear at the edges of several of the occultation profiles.

Elias, J. H.↗
NASA NTRS1996

Megavolt, Multigigawatt Pulsed Plasma Switch

Plasma switch proposed for use in high-voltage, high-current pulse power system. Designed not only to out-perform conventional spark-gap switch but also relatively compact and lightweight. Features inverse-pinch configuration to prevent constriction of current sheets into filaments, plus multiple-ring-electrode structure to resist high-voltage breakdown.

Lee, Ja H.↗
NASA NTRS1997

Experimental indication of a naphthalene-base molecular aggregate for the carrier of the 2175 angstroms interstellar extinction feature

Experiments where the simple polycyclic aromatic hydrocarbon (PAH) naphthalene (C10H8) is subjected to the energetic environment of a plasma have resulted in the synthesis of a molecular aggregate that has ultraviolet spectral characteristics that suggest it provides insight into the nature of the carrier of the 2175 angstroms interstellar extinction feature and may be a laboratory analog. Ultraviolet, visible, infrared, and mass spectroscopy, along with gas chromatography, indicate that it is a molecular aggregate in which an aromatic double ring ("naphthalene") structural base serves as the electron "box" chromophore that gives rise to the envelope of the 2175 angstroms feature. This chromophore can also provide the peak of the feature or function as a mantle in concert with another peak provider such as graphite. The molecular base/chromophore manifests itself both as a structural component of an alkyl-aromatic polymer and as a substructure of hydrogenated PAH species. Its spectral and molecular characteristics are consistent with what is generally expected for a complex molecular aggregate that has a role as an interstellar constituent.

NASA Discipline Exobiology↗
NASA NTRS2005

UV IRRADIATION OF AROMATIC NITROGEN HETEROCYCLES IN INTERSTELLAR ICE ANALOGS

Here, we present information on the properties of the ANH quinoline frozen in interstellar water-ice analogs. Quinoline is a two-ring compound structurally analogous to the PAH naphthalene. In this work, binary mixtures of water and quinoline were frozen to create interstellar ice analogs, which were then subjected to ultraviolet photolysis. We will present the infrared spectra of the resulting ices at various temperatures, as well as chromatographic analysis of the residues remaining upon warm-up of these ices to room temperature.

Elsila, J. E.↗