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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 NTRS1985

Impact and explosion crater ejecta, fragment size, and velocity

The present investigation had the objective to develop models for the distribution of fragments which are ejected at a given velocity for both impact and explosion cratering. It is pointed out that the results have application to the physics of planetary accretion and the origin of meteorites. The impact ejection of fine dust into the earth's atmosphere has been proposed as a mechanism for extinctions which occurred at the end of the Cretaceous. A technique is developed for determining the distribution of fragments which are ejected at a given velocity. The experimental data base for the distribution fragments in the ejecta blankets of impact, explosion, and nuclear craters, are discussed. Attention is also given to impact flow field calculations, fragmentation theory, and the applications of the derived relations.

Okeefe, J. D.↗
NASA NTRS1985

Contribution of explosion and future collision fragments to the orbital debris environment

The time evolution of the near-earth man-made orbital debris environment modeled by numerical simulation is presented in this paper. The model starts with a data base of orbital debris objects which are tracked by the NORAD ground radar system. The current untrackable small objects are assumed to result from explosions and are predicted from data collected from a ground explosion experiment. Future collisions between earth orbiting objects are handled by the Monte Carlo method to simulate the range of collision possibilities that may occur in the real world. The collision fragmentation process between debris objects is calculated using an empirical formula derived from a laboratory spacecraft impact experiment to obtain the number versus size distribution of the newly generated debris population. The evolution of the future space debris environment is compared with the natural meteoroid background for the relative spacecraft penetration hazard.

Su, S.-Y.↗
NASA NTRS1985

Explosive magnetic reconnection - Puzzle to be solved as the energy supply process for magnetospheric substorms?

It is pointed out that magnetospheric substorms are perhaps the most basic type of disturbances which occur throughout the magnetosphere. There is little doubt that the energy for magnetospheric substorms is delivered from the sun to the magnetosphere by the solar wind, and theoretical and observational studies have been conducted to uncover the processes associated with the energy transfer from the solar wind to the magnetosphere, and the subsequent processes leading to various magnetospheric substorm phenomena. It has been widely accepted that explosive magnetic reconnection supplies the energy for magnetospheric substorm processes. It is indicated that the auroral phenomena must be various manifestations of a large-scale electrical discharge process which is powered by the solar wind-magnetosphere dynamo. Certain problems regarding explosive magnetic reconnection are discussed.

Akasofu, S.-I.↗
NASA NTRS1987

Evolution of a localized thermal explosion in a reactive gas

Experimental observations of ignition in premixed gaseous reactants indicate that perfectly homogeneous initiation is practically unrealizable. Instead, combustion first sets in, as a rule, at small, discrete sites where inherent inhomogeneities cause chemical activity to proceed preferentially and lead to localized explosions. Combustion waves propagating away from these hot spots or reaction centers eventually envelop the remaining bulk. This study examines the spatial structure and temporal evolution of a hot spot for a model involving Arrhenius kinetics. The hot spot, characterized by peaks in pressure and temperature with little diminution in local density, is shown to have one of two possible self-similar structures. The analysis employs a combination of asymptotics and numerics, and terminates when pressure and temperature in the explosion have peaked.

Jackson, T. L.↗
NASA NTRS1987

Explosive volcanic deposits on Mars: Preliminary investigations

Two investigations were undertaken to examine possible large scale explosive volcanic deposits on Mars. The first includes an analysis of Viking Infrared Thermal Mapper (IRTM) data covering the vast deposits in the Amazonis, Memnonia, and Aeolis regions. These postulated ignimbrites have been previously mapped, and at least five high resolution nighttime IRTM data tracks cross the deposits. Preliminary analysis of the data covering Amazonis Planitia show that local features have anomalous thermal inertias but the ignimbrites as a whole do not consistently have significantly different thermal inertias from their surroundings. Preliminary photogeologic and IRTM studies of the large and small highland paterae have also begun. The purpose of IRTM studies of postulated Martian explosive volcanic deposits is to determine the physical properties of the proposed ignimbrites. If volcanic deposits are exposed at the surface, high thermal inertias, as are observed for Apollinaris Patera, should be present.

Crown, D. A.↗
NASA NTRS1986

Joining technologies for the 1990s: Welding, brazing, soldering, mechanical, explosive, solid-state, adhesive

A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Society, and Society of Manufacturing Engineers Conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

Buckley, John D.↗
NASA NTRS1986

Explosive coalescence of magnetic islands

Simulation results from both the EM collisionless particle code and the MHD particle code reveal an explosive reconnection process associated with nonlinear evolution of the coalescence instability. The explosive coalescence is a self-similar process of magnetic collapse, and ensuing amplitude oscillations in the magnetic and electrostatic energies and temperatures are modeled by an equation of motion for the scale factor in the Sagdeev potential. This phenomenon may explain the rapid energy release of a certain class of solar flares during their impulsive phase.

Tajima, T.↗
NASA NTRS1986

Impulsive phase explosive dynamics

Observational evidence and theoretical models for explosive mass motion in the impulsive phase of solar flares are reviewed. Data showing X-ray blueshifts and H-alpha redshifts are presented in graphs and diagrams and interpreted in terms of upward-moving material at 10 million K and downward-moving material at 10,000 K. This motion is found to be most simply explained in terms of explosive chromospheric evaporation.

Canfield, Richard C.↗
NASA NTRS1987

Gamma-ray constraints on Na-22 yields in nova explosions

The longitudinal distribution of diffuse 1.275 MeV emission produced by the decay of interstellar Na-22 generated by a limited class of energetic novae-accreting ONeMg white dwarfs is modeled. The probability distributions for the locations of disk novae are derived as functions of Galactocentric cylindrical coordinates. The occurrence rate for novae of all classes in the Galactic disk is about 30/yr. An occurrence rate of about 16/yr is found for spheroid novae of all classes. By comparing these simulation results with HEAO 3 upper limits on diffuse 1.275 MeV emission, upper limits of (3-5.6) x 10 to the -7th solar mass are determined for the mean Na-22 yield for energetic novae generated by accreting ONeMg white dwarfs. These Na-22 limits constrain future models of explosive nucleosynthesis in energetic nova explosions.

Higdon, J. C.↗
NASA NTRS1987

Scaling the electromagnetically driven explosive shock simulator

A heavy payload electromagnetically driven explosive shock simulator, referred to as EDESS-3, has been assembled and characterized at the Navel research Weapons Center. EDESS-3 is the logical outgrowth of the earlier EDESS 1 and 2 simulator work which explored the use of electrical pulse power technology for the generation of explosive like shocks. The features of the EDESS-3 are presented, and designs for the next generation of EDESS machines are introduced.

Persh, Robert I.↗
NASA NTRS1987

Heat budgets of analyses and forecasts of an explosively deepening maritime cyclone

The contribution of different physical processes to the explosive maritime cyclogenesis event in western North Pacific during January 12-15, 1979 was estimated by calculating quasi-Lagrangian heat budgets based on the ECMWF analyses and the numerical predictions by the UCLA general circulation model. The heat budgets suggest that the explosive cyclogenesis event was associated with very strong latent heat release in the lower troposphere, with the heating rate about twice as large as was found in studies of nonexplosively deepening extratropical cyclones. An experimental integration of the UCLA model without latent heat release indicates that 75 percent of the deepening in this cyclogenesis event can be explained by dry dynamics alone. The latent heat release serves to enhance and modulate the rapid cyclogenesis.

Liou, Chi-Sann↗
NASA NTRS1988

On the hazard of hydrogen explosions at space shuttle launch pads

This report was prepared in support of efforts to assess the hazard of accidental explosions of unburned hydrogen at space shuttle launch pads. It begins with presentation of fundamental detonation theory and a review of relevent experiments. A scenario for a catastrophic explosion at a KSC launch pad and a list of necessary conditions contributing to it is proposed with a view to identifying those conditions which, if blocked, would prevent a catastrophe. The balance of the report is devoted to juxtaposition of reassuring and disquieting facts, presentation of a set of recommendations that ignition of hydrogen-air mixtures by weak ignition sources in unconfined geometries may produce a detonation, provided the effective flame area in the initial fireball is rapidly increased by turbulent mixing. Another conclusion is that detonability limits can be different from and narrower than flammability limits only if one restricts the rate of work that can be done on a flammable gas by mechanical agencies acting on its boundaries.

Russell, John M.↗
NASA NTRS1990

Redundant, Confined-Explosive Severance Device

Noncontaminating, long, explosive joint with highly reliable separation capability invented for such applications as separation of rocket-motor stages of spacecraft from rockets or Space Shuttle. Two explosive cords housed in tubes held in place by two notched doublers and commercially available fasteners. When either cord fired, its tube expands, bending doublers and causing fracture at adjacent notch.

Bement, Laurence J.↗
NASA NTRS1989

Explosive east coast cyclogenesis - Numerical experimentation and model-based diagnostics

Numerical experimentation of explosive east-coast cyclogenesis is performed using the Florida State University Global Spectral Model (FSUGSM). The three cases examined here are the Presidents' Day storm of February 18-19, 1979 and the North Atlantic and Pacific bombs of January 18-20, 1979 which formed off the east coasts of the United States and Japan, respectively. The use of a global model provides a framework for studying the phenomena on the 3-5 day time scale. The forecast verifications of the numerical experiments indicate that the FSUGSM was able to adequately predict the phase, intensity, and synoptic-scale structure. These results justify the use of model data for diagnostic studies of the bomb. The model data are used to quantify the role of the adiabatic and diabatic forcing in the explosive cyclogenetic process, using surface pressure tendency to gage development.

Manobianco, John↗
NASA NTRS1989

Explosive spread F caused by lightning-induced electromagnetic effects

Lightning-produced electromagnetic effects may produce significant modifications in the ionospheric plasmas. An outstanding phenomenon investigated in this paper is the so-called explosive spread F, whose close link with lightning has been identified (Woodman and Kudeki, 1984). Parametric instability excited by the lightning-induced whistler waves is proposed as a potential source mechanism causing the explosive spread F.

Liao, C. P.↗
NASA NTRS1990

Explosive nucleosynthesis in SN 1987A. II - Composition, radioactivities, and the neutron star mass

The 20 solar mass model of Nomoto and Hashimoto (1988) is utilized with a 6 solar mass. He core is used to perform explosive nucleosynthesis calculations. The employed explosion energy of 10 to the 51st ergs lies within the uncertainty range inferred from the bolometric light curve. The nucleosynthesis processes and their burning products are discussed in detail. The results are compared with abundances from IR observations of SN 1987A and the average nucleosynthesis expected for Type II supernovae in Galactic chemical evolution. The abundances of long-lived radioactive nuclei and their importance for the late light curve and gamma-ray observations are predicted. The position of the mass cut between the neutron star and the ejecta is deduced from the total amount of ejected Ni-56. This requires a neutron star with a baryonic mass of 1.6 + or - 0.045 solar mass, which corresponds to a gravitational mass of 1.43 + or - 0.05 solar mass after subtracting the binding energy of a nonrotating neutron star.

Thielemann, Friedrich-Karl↗
NASA NTRS1991

The magnetic network location of explosive events observed in the solar transition region

Compact short-lived explosive events have been observed in solar transition region lines with the High-Resolution Telescope and Spectrograph (HRTS) flown by the Naval Research Laboratory on a series of rockets and on Spacelab 2. Data from Spacelab 2 are coaligned with a simultaneous magnetogram and near-simultaneous He I 10,380 -A spectroheliogram obtained at the National Solar Observatory at Kitt Peak. The comparison shows that the explosive events occur in the solar magnetic network lanes at the boundaries of supergranular convective cells. However, the events occur away from the larger concentrations of magnetic flux in the network, in contradiction to the observed tendency of the more energetic solar phenomena to be associated with the stronger magnetic fields.

Porter, J. G.↗
NASA NTRS1991

Explosive desorption of icy grain mantles in dense clouds

The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

Schutte, W. A.↗