Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Plumes”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Shuttle system ascent aerodynamic and plume heating

The shuttle program provided a challenge to the aerothermodynamicist due to the complexity of the flow field around the vehicle during ascent, since the configuration causes multiple shock interactions between the elements. Wind tunnel tests provided data for the prediction of the ascent design heating environment which involves both plume and aerodynamic heating phenomena. The approach for the heating methodology based on ground test firings and the use of the wind tunnel data to formulate the math models is discussed.

Foster, L. D.↗
NASA NTRS1985

Results of the SPAS-01 RCS plume impingement test

The Orbiter RCS flowfield is modeled in the free molecular region and an impingement analysis is performed to characterize on-orbit plume interactions with nearby bodies, such as the SPAS-01 satellite. The flow in the far field is treated with a source flow model at any point 40 ft from the nozzle. Impingement is calculated according to Newtonian impact theory. The flow density in the far field is expressed in terms of a conservation of energy equation, with account taken of the expansion of the gas, cooling, and the angular distribution. The SPAS-01 platform gathered data at eight different positions around the Orbiter to test the model predictions. Excellent agreement was obtained in predictions of the torque and rotation rate induced on the SPAS by firing the thrusters.

Lazaron, M. P.↗
NASA NTRS1985

Sea floor swells and mantle plumes

Most of the intraplate oceanic hot spots are located on the crest of broad topographic swells in the sea floor. These swells have Gaussian shaped profiles, with up to 1.6 km of relief and half widths of 200 to 300 km. Swells are accompanied by positive geoid height anomalies with amplitudes of 6 to 8 m. In the Atlantic and Pacific basins swells cover an area equal to 10% of the Earth's surface. Next to boundary layer contraction, swells are the most important cause of uplift and subsidence in oceanic lithosphere. Calculation of buoyancy supported topography and geoid height were combined with uplift data from laboratory experiments to assess whether sea floor swell can be produced by mantle plumes. The critical constraints are: (1) swell topographic profiles; (2) geoid height/topographic height ratios; and (3) uplift rates, estimated to be 0.2 km/ma.

Olson, P.↗
NASA NTRS1985

Plasma-gas interactions studies in a hybrid plume plasma rocket

Plasma-gas interaction was investigated and the basic mechanisms for energy and particle transport. The solution approach assumes cylindrical geometry and includes a multiplicity of atomic reactions, and the presence of a strong magnetic field is described. The principal reactions are electron and ion impact ionization, and charge exchange between hot ions and cold neutrals. Radial particle and energy transport is mainly by diffusion. A modified Bohm diffusion model for plasma in the core of the plume, and classical neutral particle diffusion in the cooler regions of the flow are presented. Neutrals are allowed to free stream in the low density regions, where the collision mean-free-path becomes comparable, or even larger than the characteristic dimensions of the system.

Chang, F. R.↗
NASA NTRS1987

Plasma Rocket With Hybrid Exhaust Plume

Proposed plasma rocket, described in report, generates hybrid exhaust plume comprising annular layer of relatively cool neutral gas around plasma core. Plasma and gas intermix, providing gradual radial transition between the two. Amount of gas injected adjusted to control propulsive efficiency; relatively cool gas boundary layer at surface of nozzle insulates nozzle from high plasma temperature.

Chang, Franklin R.↗
NASA NTRS1987

Model and full scale study of twin supersonic plume resonance

This paper examines the effect of both nozzle geometry and scale on the twin supersonic plume resonance phenomenon associated with aircraft having engine nozzle center-to-center spacings less than two diameters. Exit plane near field dynamic pressures were measured for both single and dual nozzle operation in 4.7 percent model and full scale under static conditions. The frequencies associated with this phenomenon were predicted to within 5 percent for a full scale F-15 aircraft. Amplitude levels associated with this phenomenon were found to dominate the dynamic pressure fluctuations in the inter-nozzle region, and reach a level near the structural design limit for this aircraft. The model scale studies, which involved both axisymmetric and rectangular geometry, indicated that amplitude levels could be expected to be much higher in flight. High amplitude levels would likely occur in the overexpanded region for axisymmetric geometry, and in the underexpanded region for rectangular geometry.

Seiner, John M.↗
NASA NTRS1987

Velocity measurements in the plume of an arcjet engine

A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

Pivirotto, T. J.↗
NASA NTRS1987

Flow field description of the Space Shuttle Vernier reaction control system exhaust plumes

The flow field for the Vernier Reaction Control System (VRCS) jets of the Space Shuttle Orbiter has been calculated from the nozzle throat to the far-field region. The calculations involved the use of recently improved rocket engine nozzle/plume codes. The flow field is discussed, and a brief overview of the calculation techniques is presented. In addition, a proposed on-orbit plume measurement experiment, designed to improve future estimations of the Vernier flow field, is addressed.

Cerimele, Mary P.↗
NASA NTRS1987

Space Shuttle Main Engine plume spectral monitoring preliminary results

In order to provide the information necessary to develop a rocket engine ground test failure detection monitor which keys on anomalous activity in the plume, a series of experimental observations were made during single engine Space Shuttle Main Engine (SSME) tests. The observations were conducted from the 220 nm wavelength in the ultraviolet out to the 15 micron wavelength in the infrared. Four types of instruments were employed including analog autoranging narrow band radiometers, optical multichannel analyzers, mechanical scanning and film plate spectrometers, and imaging cameras. Some results included: strong OH radiation in the UV up to vibrational transition state four; Na and K radiation lines in all phases of engine operation; reaction of some of the instruments to minor engine anomalies; good shock structure imaging; striations in the flow in the 310 nm OH band; and detection of gross changes in engine operating state such as start or shutdown.

Cikanek, H. A., III↗
NASA NTRS1987

Effect of nozzle geometry on the resistojet exhaust plume

Five nozzle configurations were used to study the effect of geometry on the plume structure of a resistojet exhausting into a vacuum. Mass flux data in the forward and back flux regions were obtained with a cryogenically cooled quartz crystal microbalance. The propellant used was CO2 at 300 K and a mass flow rate of 0.2 g/s. The data reveal that the percent of mass flow contained within half angles of 10, 30, and 40 deg varied by less than 12 percent from a standard 20 deg half-angle cone nozzle.

Breyley, Loranell↗
NASA NTRS1988

Experimental evaluation of resistojet thruster plume shields

The exhaust of an engineering model resistojet has been investigated using rotary pitot probes and a rotary quartz crystal microbalance. The resistojet operated on CO2 propellant at a mass flow rate of 0.29 g/sec in both heated and unheated flows. Measurements of local flow angles in the near field of a conical plume shield indicated that the shield was not wholly effective in confining the flow to the region upstream of its exit plane. However, the absolute levels of the measured mass flux into the backflow region were very low, on the order of 7 x 10 to the -7 power g/sqcm/sec or less. The use of a circualr disk at the exit plane of the existing conical shield showed some benefit in decreasing the amount of backflow by a factor of two. Lastly, a detached shield placed upstream of the resistojet exit plane demonstrated a small degree of local shielding for the region directly behind it.

Carney, Lynnette M.↗
NASA NTRS1988

The onset of plume dynamics in the spectral space

Time-dependent convection for infinite Prandtl number fluids has been investigated hitherto in the physical domain. Dynamics of plumelike structures resulting from boundary-layer instabilities can be interpreted in the spectral domain as having both direct and inverse cascades of energy taking place. In the physical domain only a small part of the spectrum is discernible. But the rest of the spectrum is needed for properly describing the nonlinear process. Only a relatively few modes, fewer than ten, are actually required for describing the essential features associated with the onset of plume dynamics.

Vincent, Alain P.↗
NASA NTRS1988

3-D plume flow computations with an upwind solver

In the present study multi-nozzle plume flows are computed with a three-dimensional, Navier-Stokes solver. Numerical simulations are performed with the flux-split, two-factor, time symptotic, viscous flow solver. The two factor splitting provides a stable three-dimensional solution procedure under ideal-gas assumptions. Viscous, ideal-gas solutions for a thin lip symmetrical nozzle are compared with experimental and numerical solutions. Computed solutions to axisymmetric and three-dimensional, multi-nozzle problems at various altitudes and flight conditions demonstrate flow field complexity and three-dimensional effects.

Venkatapathy, Ethiraj↗
NASA NTRS1989

The effects of arcjet operating condition and constrictor geometry on the plasma plume

Measurements of plasma number density and electron temperature were obtained in the plumes of lab arcjet thrusters using electrostatic probes of both spherical and cylindrical geometry. The two arcjet thrusters used had different constrictor and/or nozzle geometries and operated on mixtures of nitrogen, hydrogen, and ammonia to simulate the decomposition products of hydrazine and ammonia. An increase in the measured electron density was observed for both geometries with increasing arc power at a constant mass flow rate and with increasing mass flow rate at a constant arc current. For a given operating condition, the electron number density decreased exponentially off centerline and followed an inverse distance squared relationship along the thrust axis. Typical measured electron temperatures ranged from 0.1 to 0.2 eV.

Carney, Lynnette M.↗
NASA NTRS1989

Near-field acoustic environment of a supersonic plume adjacent to a wall

The interaction of a supersonic plume with an adjacent plane surface has been studied using phase-conditioned schlieren flow visualization and near-field microphone measurements. As a consequence of interaction with the wall, the round and 3:1 rectangular/divergent nozzle configurations generated the most intense screech at about one throat diameter from the wall. It is found that the low-aspect-ratio rectangular nozzle has a screech oscillation parallel to the wall which is enhanced by proximity to the wall.

Wlezien, R. W.↗
NASA NTRS1988

Experimental evaluation of resistojet thruster plume shields

The exhaust of an engineering model resistojet has been investigated using rotary pitot probes and a rotary quartz crystal microbalance. The resistojet operated on CO2 propellant at a mass flow rate of 0.29 g/sec in both heated and unheated flows. Measurements of local flow angles in the near field of a conical plume shield indicated that the shield was not wholly effective in confining the flow to the region upstream of its exit plane. However, the absolute levels of the measured mass flux into the backflow region were very low, on the order of 7 x 10 to the -7 power g/sq cm/sec or less. The use of a circular disk at the exit plane of the existing conical shield showed some benefit in decreasing the amount of backflow by a factor of two. Lastly, a detached shield placed upstream of the resistojet exit plane demonstrated a small degree of local shielding for the region directly behind it.

Carney, Lynnette M.↗
NASA NTRS1988

A tandem mirror hybrid plume plasma propulsion facility

This paper discusses a novel concept in electrodeless plasma propulsion, in which the materials problems are ameliorated by an electrodeless magnetic confinement scheme borrowed from the tandem mirror approach to controlled thermonuclear fusion. The concept also features a two-stage magnetic nozzle with an annular hypersonic coaxial gas injector near the throat. The nozzle produces hybrid plume by the coaxial injection of hypersonic neutral gas, and the gas layer thus formed protects the material walls from the hot plasma and, through increased collisions, helps detach it from the diverging magnetic field. The tandem mirror plasma propulsion facility is capable of delivering a variable I(sp). The results of numerical simulation of this concept are presented together with those from an experimental tandem-mirror plasma propulsion device.

Yang, T. F.↗
NASA NTRS1989

The effects of arcjet thruster operating condition constrictor geometry on the plasma plume

Measurements of plasma number density and electron temperature were obtained in the plumes of lab arcjet thrusters using electrostatic probes of both spherical and cylindrical geometry. The two arcjet thrusters used had different constrictor and/or nozzle geometries and operated on mixtures of nitrogen, hydrogen, and ammonia to simulate the decomposition products of hydrazine and ammonia. An increase in the measured electron density was observed for both geometries with increasing arc power at a constant mass flow rate and with increasing mass flow rate at a constant arc current. For a given operating condition, the electron number density decreased exponentially off centerline and followed an inverse distance squared relationship along the thrust axis. Typical measured electron temperatures ranged from 0.1 to 0.2 eV.

Carney, Lynnette M.↗