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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Nearly spherical constant-power detonation waves as driven by focused radiation.

Analysis is made of the flow within a 3-D spark created in a gas absorbing energy from a steady conical beam of radiation (typically obtained from an array of lasers) with nearly spherical symmetry. First-order deviations are represented by series of Legendre polynomials of the polar angle. Self-similarity is demonstrated. For harmonics 1 to 5 radial profiles of velocity components, density and pressure are presented. The linear perturbation scheme exhibits a singularity at the focus. This reflects the existence of a 'forbidden zone', as is shown by a study of the full non-linear flow equations.

George, Y. H.↗
NASA NTRS1973

Neutron-star formation in the carbon-detonation supernova.

Neutrino losses, such as those driven by the convective Urca process, may affect the evolution of stars in the mass range from 4 to 8 solar masses so as to lead to collapse of their degenerate carbon/oxygen cores. A corresponding hydrodynamic model is computed which leads to the formation of a 1.3 to 1.4 solar mass neutron star with the expulsion of a small fraction of the mass, about 0.l solar mass at about 20,000 km/sec into the overlying hydrogen envelope. This sets the stage for the Ostriker-Gunn mechanism in which Type II supernovae and pulsars are formed.

Wheeler, J. C.↗
NASA NTRS1973

Nearly spherical constant-power detonation waves as driven by focused radiation

An analysis is made of the flow within a three-dimensional explosion, or spark, created in a gas absorbing energy from a steady conical beam of radiation with nearly spherical symmetry. The radiation, typically from an array of lasers with a common focus, is assumed to be very intense and absorbed immediately behind an outwardly advancing strong shock. Departures of the laser power from spherical uniformity, which would result from practical problems of arrangement, are conveniently represented by an ascending series of Legendre polynomials in the polar angle. For nonuniformities of small amplitude, first-order perturbations of the flow field are analyzed in detail. Self-similarity is shown to be retained for zero counter-pressure and power constant with time. For the first five harmonics in power distortion, the resulting fourth-order system of equations is solved numerically for profiles of velocity components, density, pressure, and shock shape. Results are presented graphically.

George, Y. H.↗
NASA NTRS1980

A boundary-layer treatment for turbulent detonation waves

The profile of turbulent intensity versus Reynolds number from bursts found in an ignition front agrees with the Orr-Sommerfeld solutions for unstable boundary-layer flow. This result provides the first evidence of a formal connection between bursting transition to turbulence in flows which share the boundary-layer approximation but which are otherwise unrelated.

Johnson, J. A., III↗
NASA NTRS1980

Numerical calculation of shock-induced initiation of detonations

Results of numerical calculations of the impact of steel cylinders and spheres on the plastic bonded high explosive PBX 9501 are described. The calculations were carried out by a reactive, multicomponent, two dimensional, Eulerian hydrodynamic computer code, 2DE. The 2DE computer code is a finite difference code that uses the donor acceptor cell method to compute mixed cell fluxes. The parameters in the Forest Fire burn model are developed from experiments where the induced shock approximates a plane wave and are applied, in this case, to a situation where the induced shock is a divergent wave with curvature that depends on the size and shape of the projectile. The calculated results are compared with results from experiments involving instrumented mock and live high explosives, with projectiles of varying size, shapes, and velocities.

Cort, G. E.↗
NASA NTRS1986

Mixing of cryogenic fluids and predicted detonation properties for multiphase liquid oxygen and liquid hydrogen

The mixing and explosion of LOX and LH sub 2 is a concern for Space Transportation System operations. To understand this problem, cryogenic mixing is experimentally studied by pouring 1,2,2 trichloro 2,1,1 trifluoroethane (Freon 113) into LN sub 2, LN sub 2 into LH sub 2, and LH sub 2 into into LN sub 2 in a 1 m by 15 cm cylindrical glass vessel. Data from these experiments is compared with previous studies and a hypothesis is advanced that LOX/LH sub 2 mixing will result in a complex, heterogenous, multiphase aggregation including LOX, SOX, LH sub 2, and VH sub 2 using the multiphase hypothesis. Visual and x ray observations of the process and mass measurements are reported.

Bishop, C. V.↗
NASA NTRS1991

Timing system for firing widely spaced test nuclear detonations

The national weapons design laboratories (Los Alamos National Laboratory and Lawrence Livermore National Laboratory) test fire nuclear devices at the Nevada Test Site (NTS), which is spread over an area of over 1200 square miles (a bit larger than the state of Rhode island). On each test there are hundreds of high time resolution recordings made of nuclear output waveforms and other phenomena. In order to synchronize these recordings with each other, with the nuclear device, and with offsite recordings, there is a requirement that the permanent command center and the outlying temporary firing sites be time tied to each other and to UTC to permit firing the shot at a predetermined time with an accuracy of about a microsecond. The system is so designed that this can reduce to about 100 nanoseconds if it should prove necessary in the future.

Ralph E. Partridge↗
NASA NTRS1993

Ram acceleration from a two phase detonative system

A concept for ram acceleration is presented here, which uses a combination of a gas core and a layer of solid explosive or propellant to generate high thrust densities. The concept can be either self-synchronized or externally synchronized, and may be reusable. It has the potential to achieve very high acceleration rates, higher exit velocities and to lower the tube length requirements. Preliminary numerical simulations are presented and discussed, which show the characteristics of the flow fields. Stable conditions can be achieved for low mass loadings of solid explosive, and relatively slow combustion. Accurate knowledge of the thermo-chemical properties and the equations of state of the gas and solid components is essential for further tuning of the concept.

Cambier, Jean-Luc↗