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At least 181 records · Page 10

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NASA NTRS1975

Summary of nozzle-exhaust plume flowfield analyses related to space shuttle applications

Exhaust plume shape simulation is studied, with the major effort directed toward computer program development and analytical support of various plume related problems associated with the space shuttle. Program development centered on (1) two-phase nozzle-exhaust plume flows, (2) plume impingement, and (3) support of exhaust plume simulation studies. Several studies were also conducted to provide full-scale data for defining exhaust plume simulation criteria. Model nozzles used in launch vehicle test were analyzed and compared to experimental calibration data.

Penny, M. M.↗

NASA NTRS1975

Velocity variations of an Equatorial plume throughout a Jovian year

Features in the equatorial zone of Jupiter show that the equatorial plume reported by Pioneer 10 has existed for an 11-year interval. During this interval the plume has shown an acceleration which can be interpreted as a constant component of 3 x 10 to minus 8th power m/sq cm and a sinusoidal component which anticorrelates with the planetocentric declination of the sun, D sub s, and has an amplitude of -0.96 meters per second per degree change of D sub s. The sinusoidal component has been interpreted in terms of solar heating. Throughout this interval of time the equatorial zone has appeared abnormally dark and has contained many dark projections along the northern edge. When the plume approaches to within 25 to 30 deg of these features they are deflected in the direction of motion of the plume and then dissipate or become obscured as the plume passes. After passage of the plume normal features are again observed.

Reese, E.↗

NASA NTRS1974

A Transonic and Surpersonic Investigation of Jet Exhaust Plume Effects on the Afterbody and Base Pressures of a Body of Revolution

An experimental aerodynamic investigation was conducted to provide data for studies to determine the criteria for simulating rocket engine plume induced aerodynamic effects in the wind tunnel using a simulated gaseous plume. Model surface and base pressure data were obtained in the presence of both a simulated and a prototype gaseous plume for a matrix of plume properties to enable investigators to determine the parameters that correlate the simulated and prototype plume-induced data. The test program was conducted in the Marshall Space Flight Center's 14 x 14-inch trisonic wind tunnel using two models, the first being a strut mounted cone-ogive-cylinder model with a fineness ratio of 9. Model exterior pressures, model plenum chamber and nozzle performance data were obtained at Mach numbers of 0.9, 1.2, 1.46, and 3.48. The exhaust plume was generated by using air as the simulant gas, or Freon-14 (CF4) as the prototype gas, over a chamber pressure range from 0 to 2,000 psia and a total temperature range from 50 to 600 F.

Andrews, C. D.↗

NASA NTRS1976

Velocity variations of an equatorial plume throughout a Jovian year

Analysis of features in the Equatorial Zone of Jupiter has shown that the equatorial plume reported by Pioneer 10 has existed for an 11-yr interval. During this interval, the plume has shown an acceleration which can be interpreted as a constant component of 3 hundred-millionths m/sec-squared and a sinusoidal component which anticorrelates with the planetocentric declination of the sun and has an amplitude of -0.96 m/sec per degree change of planetocentric declination. The sinusoidal component has been interpreted in terms of solar heating. Throughout this interval of time, the Equatorial Zone has appeared abnormally dark and has contained many dark projections along the northern edge. When the plume approaches to within 25 to 30 deg of these features, they are deflected in the direction of motion of the plume and then dissipate or become obscured as the plume passes. After passage of the plume, normal features are again observed.

Reese, E.↗

NASA NTRS1978

A computational scheme usable for calculating the plume backflow region

The effects of the nozzle wall boundary layer on the plume flowfield are neglected in the majority of computational schemes which exist for the calculation of rocket engine exhaust plume flowfields. This neglect, which is unimportant in many applications, becomes unacceptable for applications where a surface which can be adversely affected by plume impingement forces, heating, or contamination is located behind the nozzle exit plane in what is called the 'plume backflow region'. The flow in this region originates in, and is highly affected by, the nozzle wall boundary layer. The inclusion of the effects of the boundary layer in the calculations is required for an appropriate determination of the flowfield properties within this region. A description is presented of the results of modifications of a method-of-characteristics computer program. The modifications were made to include the effects of the nozzle wall boundary layer on the plume flowfield. A comparison of computed and experimental data indicates that the employed computer program may be a useful tool for calculating the entire plume flowfield for liquid propellant rocket engines.

Cooper, B. P., Jr.↗

NASA NTRS1979

Volcanic eruption plumes on Io

Preliminary analyses of the eight volcanic eruption plumes detected on Io by Voyager 1 are presented. Plumes were observed on the bright and dark limbs of the satellite corresponding to half of the surface and range from 10,000 to 75 km in width and 280 to 70 km in height. Most plumes were observed to be umbrella-shaped, however one consists of a very diffuse cloud lacking columnar fountain characteristics. Plume sources are characterized by a dark central area, surrounded by a bright ring, which in turn is surrounded by a broad, diffuse region; the presence of similar markings in regions not observed at the limb indicates additional volcanic activity on Io. No changes were detected in the sizes or intensities of the eruptions over the 6.5-day viewing period, however a change in the appearance of a region near one plume suggests a short-lived eruption between observations. Seven of the eight plumes are located within 30 deg of the equator, implying that equatorial surfaces are generally younger than those in the polar regions.

Strom, R. G.↗

NASA NTRS1981

Application of the mixing-reaction in series model to NO/x/-O3 plume chemistry

The mixing-reaction in series model developed by Ghodsizadem (1978) is successfully applied to the study of NO oxidation in the near-source portion of the Potomac Electric Company's Morgantown, Maryland power plant plume. The model employs a single parameter. With initial conditions consistent with the plume data measured by Davis et al. (1974) and utilizing the mixing parameter estimated from the study by Shu et al. (1978), the predicted temporal profiles of the ratio of the concentration of NO2 to NO, of NO2 to NO plus NO2, in-plume concentrations of NO and O3, and fraction of NO remaining are consistent with field study data. In addition, the model predicts large deviations from the photostationary state in the near-source portion of the plume, also consistent with field study data. In the far field region of this plume (t greater than approximately 20 min), the mixing processes are essentially complete over much of the plume cross-section.

Carmichael, G. R.↗

NASA NTRS1982

Volcanic eruption plumes on Io

The nine eruption plumes observed by Voyager 1 are discussed. The plumes range in height from about 60 to over 300 km with corresponding ejection velocities of about 0.5 to 1.0 km/s. Plume sources are located on level plains rather than topographic highs and consist of either fissures or calderas. Except for Ple, the brightness distribution monotonically decreases from the core to the top of the plume. Numerous surface deposits similar to those associated with active plumes probably mark the sites of recent eruptions. The distribution of active and recent eruptions appears to be concentrated in the equatorial regions. This suggests that the depositional rate is greater and the surface age younger in the equatorial regions, possibly accounting for the active eruptions suggests that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

Strom, R. G.↗

NASA NTRS1985

Bright spot analysis of ocean-dump plumes using Landsat MSS

Identifying ocean-dumped materials by analysing the upwelled solar energy from the plume is complicated by the dispersion of the plume and the spectral absorption of the water. It is shown that the spectral analysis of ocean-dump plumes, using Landsat multispectral scanner (MSS) data, should be confined to the brightest area within the plume, the region where the waste material is least dispersed and nearest the surface. The decay of the upwelled radiance with time of the brightest pixel within the plume, at least for iron acid waste, is predictable. An accurate age determination of an acid plume is limited by striping within the MSS data.

Bowker, D. E.↗

NASA NTRS1985

High-altitude plume computer code development

The flowfield codes that have been developed to predict rocket motor plumes at high altitude were used to predict plume properties for the RCS motor which show reasonable agreement with experimental data. A systematic technique was established for the calculation of high altitude plumes. The communication of data between the computer codes was standardized. It is recommended that these outlined procedures be more completed, documented and updated as the plume methodology is applied to the varied problems of plume flow and plume impingement encountered by space station design and operation.

Audeh, B. J.↗

NASA NTRS1988

Development of a shuttle plume radiation heating indicator

The primary objectives were to develop a Base Heating Indicator Code and a new plume radiation code for the Space Shuttle. Additional work included: revision of the Space Shuttle plume radiation environment for changes in configuration and correction of errors, evaluation of radiation measurements to establish a plume radiation model for the SRB High Performance Motor (HPM) plume, radiation predictions for preliminary designs, and participation in hydrogen disposal analysis and testing for the VAFB Shuttle launch site. The two most significant accomplishments were the development of the Base Heating Indicator Code and the Shuttle Engine Plume Radiation (SEPRAD) Code. The major efforts in revising the current Shuttle plume radiation environment were for the Orbiter base heat shield and the ET components in the Orbiter-ET interface region. The work performed is summarized in the technical discussion section with references to the documents containing detailed results. The technical discussion is followed by a summary of conclusions and recommendations for future work.

Reardon, John E.↗

NASA NTRS1991

A preliminary characterization of applied-field MPD thruster plumes

Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied field magnetohydrodynamic thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 times 10 (exp 18) to 8 times 10 (exp 18) m(exp -3) and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.

Myers, Roger M.↗

NASA NTRS1991

The effects of the exhaust plume on the lightning triggering conditions for launch vehicles

Apollo 12 and Atlas Centaur 67 are two launch vehicles that have experienced triggered lightning strikes. Serious consequences resulted from the events; in the case of Atlas Centaur 67, the vehicle and the payload were lost. These events indicate that it is necessary to develop launch rules which would prevent such occurrences. In order to develop valid lightning related rules, it is necessary to understand the effects of the plume. Some have assumed that the plume can be treated as a perfect conductor, and have computed electric field enhancement factors on that basis. The authors have looked at the plume, and believe that these models are not correct, because they ignore the fluid motion of the conducting plates. The authors developed a model which includes this flow character. In this model, the external field is excluded from the plume as it would be for any good conductor, but, in addition, the charge must distribute so that the charge density is zero at some location in the exhaust. When this condition is included in the calculation of triggering enhancement factors, they can be two to three times larger than calculated by other methods which include a conductive plume but don't include the correct boundary conditions. Here, the authors review the relevant features of rocket exhausts for the triggered lightning problem, present an approach for including flowing conductive gases, and present preliminary calculations to demonstrate the effect that the plume has on enhancement factors.

Eriksen, Frederick J.↗

NASA NTRS1990

Evolution of tropical plumes in VAS water vapor imagery

Synoptic scale tropical plumes are analyzed using satellite data and outgoing longwave radiation data. The evolution of plumes is described and their precursor signals are examined. The horizontal moisture patterns of the plumes are compared with nonplume climatology, and the predictability of plumes based solely on satellite imagery is assessed. The results show that a plume evolves as a stationary, tropical, dry or moist dipole, separated by an exceptionally strong cloud or moisture gradient. Tropical plume evolution is accompanied by a systematic drying of the tropical eastern Pacific atmosphere before development, and moistening and increased cloudiness with development.

Mcguirk, James P.↗

NASA NTRS1991

Navier-Stokes computations with finite-rate chemistry for LO2/LH2 rocket engine plume flow studies

Computational fluid dynamics methods have been developed and applied to Space Shuttle Main Engine LO2/LH2 plume flow simulation/analysis of airloading and convective base heating effects on the vehicle at high flight velocities and altitudes. New methods are described which were applied to the simulation of a Return-to-Launch-Site abort where the vehicle would fly briefly at negative angles of attack into its own plume. A simplified two-perfect-gases-mixing approach is used where one gas is the plume and the other is air at 180-deg and 135-deg flight angle of attack. Related research has resulted in real gas multiple-plume interaction methods with finite-rate chemistry described herein which are applied to the same high-altitude-flight conditions of 0 deg angle of attack. Continuing research plans are to study Orbiter wake/plume flows at several Mach numbers and altitudes during ascent and then to merge this model with the Shuttle 'nose-to-tail' aerodynamic and SRB plume models for an overall 'nose-to-plume' capability. These new methods are also applicable to future launch vehicles using clustered-engine LO2/LH2 propulsion.

Dougherty, N. Sam↗

NASA NTRS1991

A preliminary characterization of applied-field MPD thruster plumes

Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied-field MPD thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 x 10 to the 18th to 8 x 10 to the 18th cu m and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.

Myers, Roger M.↗

NASA NTRS1992

Computational fluid dynamics analysis of Space Shuttle main engine multiple plume flows at high-altitude flight conditions

Computational fluid dynamics (CFD) analysis is providing verification of Space Shuttle flight performance details and is being applied to Space Shuttle Main Engine Multiple plume interaction flow field definition. Advancements in real-gas CFD methodology that are described have allowed definition of exhaust plume flow details at Mach 3.5 and 107,000 ft. The specific objective includes the estimate of flow properties at oblique shocks between plumes and plume recirculation into the Space Shuttle Orbiter base so that base heating and base pressure can be modeled accurately. The approach utilizes the Rockwell USA Real Gas 3-D Navier-Stokes (USARG3D) Code for the analysis. The code has multi-zonal capability to detail the geometry of the plumes based region and utilizes finite-rate chemistry to compute the plume expansion angle and relevant flow properties at altitude correctly. Through an improved definition of the base recirculation flow properties, heating, and aerodynamic design environments of the Space Shuttle Vehicle can be further updated.

Dougherty, N. S.↗

NASA NTRS1991

Four dimensional reconstruction and analysis of plume images

A number of methods have been investigated and are under current investigation for monitoring the health of the Space Shuttle Main Engine (SSME). Plume emission analysis has recently emerged as a potential technique for correlating the emission characteristics with the health of an engine. In order to correlate the visual and spectral signatures of the plume emission with the characteristic health monitoring features of the engine, the plume emission data must be acquired, stored, and analyzed in a manner similar to flame emission spectroscopy. The characteristic visual and spectral signatures of the elements vaporized in exhaust plume along with the features related to their temperature, pressure, and velocity can be analyzed once the images of plume emission are effectively acquired, digitized, and stored on a computer. Since the emission image varies with respect to time at a specified planar location, four dimensional visual and spectral analysis need to be performed on the plume emission data. In order to achieve this objective, feasibility research was conducted to digitize, store, analyze, and visualize the images of a subsonic jet in a cross flow. The jet structure was made visible using a direct injection flow visualization technique. The results of time-history based three dimensional reconstruction of the cross sectional images corresponding to a specific planar location of the jet structure are presented. The experimental set-up to acquire such data is described and three dimensional displays of time-history based reconstructions of the jet structure are discussed.

Dhawan, Atam P.↗