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  • 1
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    Convective and radiative heating for vehicle return from the Moon and Mars (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The aerothermal environment is examined for two vehicle forebodies near the peak heating points of lunar and martian return-to-earth trajectories at several nominal entry velocities. The first vehicle forebody is that of a 70 deg aerobrake for entry into earth orbit; the second, a capsule of Apollo configuration for direct entry into the earth's atmosphere. The configurations and trajectories are considered likely candidates for such missions. Two-temperature, thermochemical nonequilibrium models are used in the flow field analyses. In addition to Park's empirical model for dissociation under conditions of thermal nonequilibrium, the Gordiets kinetic model for the homonuclear dissociation of N2 and O2 is also considered. Temperature and emission profiles indicate nonequilibrium effects in a 2 to 5 cm post shock region. Substantial portions of the shock layer flow appear to be in equilibrium. The shock layer over an aerobrake for return from the moon exhibits the largest extent of nonequilibrium effects of all considered missions. Differences between the Gordiets and Parks kinetic model were generally very small for the lunar return aerobrake case, the greatest difference of 6.1 percent occurring in the radiative heating levels.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-110185 , NAS 1.15:110185
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  • 2
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    A parametric analysis of radiative structure in aerobrake shock layers (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A broad-spectrum version of the NEQAIR code was modified to account for self-absorption and applied to AFE flowfields calculated by the LAURA code with a variety of kinetic models. The resulting radiative fluxes were obtained in a decoupled fashion from the flowfield solver along the vehicle's stagnation streamline. The radiative flux obtained was broken down by causative process to study the radiative structure of the AFE's flowfield for the various kinetic models. In addition, the radiative fluxes for several points on a typical AFE trajectory were analyzed to examine how the radiative structure changes as the vehicle completes its aeropass. Only two radiative processes dominated the stagnation radiative flux, and the flow field conditions near the wal were found to exert considerable influence over the radiative flux to the wall.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-2970
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  • 3
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    Electron number density profiles for the Aeroassist Flight Experiment (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The basic features of a Microwave Reflectometer Ionization Sensor (MRIS) as designed for utilization on the Aeroassist Flight Experiment are described. A parametric study of the effects of trajectory and unknowns in the thermochemical nonequilibrium models for translational and vibrational-electronic energy exchange rates, reaction rates, and the average electronic excitation level of atoms is performed to illustrate how the MRIS data may be employed for code validation. This study, implemented with program LAURA, shows a particular sensitivity of the onset and severity of an electron avalanche phenomena associated with changes in these physical models.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: AIAA PAPER 92-0804
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  • 4
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    Finite-Difference Solution for Laminar or Turbulent Boundary Layer Flow over Axisymmetric Bodies with Ideal Gas, CF4, or Equilibrium Air Chemistry (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer code was developed that uses an implicit finite-difference technique to solve nonsimilar, axisymmetric boundary layer equations for both laminar and turbulent flow. The code can treat ideal gases, air in chemical equilibrium, and carbon tetrafluoride (CF4), which is a useful gas for hypersonic blunt-body simulations. This is the only known boundary layer code that can treat CF4. Comparisons with experimental data have demonstrated that accurate solutions are obtained. The method should prove useful as an analysis tool for comparing calculations with wind tunnel experiments and for making calculations about flight vehicles where equilibrium air chemistry assumptions are valid.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-3271 , L-17102 , NAS 1.60:3271
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  • 5
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    Comparison of vibration dissociation coupling and radiative heat transfer models for AOTV/AFE flowfields (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A series of detailed studies comparing various vibration dissociation coupling models, reaction systems and rates, and radiative heating models has been conducted for the nonequilibrium stagnation region of an AFE/AOTV vehicle. Atomic and molecular nonequilibrium radiation correction factors have been developed and applied to various absorption coefficient step models, and a modified vibration dissociation coupling model has been shown to yield good vibration/electronic temperature and concentration profiles. While results indicate sensitivity to the choice of vibration dissociation coupling model and to the nitrogen electron impact ionization rate, by proper combinations accurate flowfield and radiative heating results can be obtained. These results indicate that nonequilibrium effects significantly affect the flowfield and the radiative heat transfer. However, additional work is needed in ionization chemistry and absorption coefficient modeling.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-2673
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  • 6
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    Calculation of convective and radiative heating on the forebody heatshield of the aeroassist flight experiment vehicle (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The total (convective and radiative) heating is calculated over the entire forebody heatshield of the Aeroassist Flight Experiment (AFE) vehicle. The convective heating is calculated using a three-dimensional Navier-Stokes code (LAURA) which includes both chemical and thermal nonequilibrium effects. The flowfield solution is then used to provide inputs to a nonequilibrium air radiation code (NEQAIR) to calculate the nonequilibrium radiative heating. Results are presented at two points on the current Baseline 5A trajectory corresponding to the start of the primary data taking period and peak heating.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-104103 , NAS 1.15:104103
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  • 7
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    An approximate method for the calculation of nonequilibrium radiative heat transfer (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A simplified method for the calculation of radiative heat transfer in hypersonic reentry flows where local thermal nonequilibrium (LTNE) conditions exist is presented. This method has been incorporated into the computer code RADMC (RADiation/Modified Corrections), which utilizes an approximate 'two-state' model of the electronic levels of atoms and molecules in the determination of the populations of the excited states for both LTNE and local thermal equilibrium (LTE) conditions for each of the relevant chemical species. The population data are used to calculate a correction factor to the radiative cross sections in an eight-step nongray radiative heat-transfer model. Results have been obtained for various points along the proposed trajectory of the Aeroassist Flight Experiment and the Fire II trajectory, and compared with results obtained for the same flowfields from the NEQAIR radiative heat-transfer code.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-0135
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  • 8
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    Heating analysis for a Lunar Transfer Vehicle at near-equilibrium flow conditions (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A heating analysis for a 15.2 m diameter Lunar Transfer Vehicle (LTV) at 0 and 10.6 deg angle of attack for a nominal trajectory through the earth's atmosphere is described. The analysis utilizes the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) with thin-layer, Navier-Stokes, thermochemical nonequilibrium options. Radiative heating levels are calculated using the Langley Optimized RAdiative Nonequilibrium (LORAN) and the Non-EQuilibrium AIr Radiation (NEQAIR) codes. At peak heating, the shock layer is substantially in equilibrium. Comprehensive spatial and spectral grid convergence studies have been implemented to quantify grid effects on the convective and radiative heating levels. Axisymmetric tests including the coupled effects of radiative energy transfer show negligible change to the convective heating and a 20 percent reduction in the radiative heating.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 93-0270 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 13 p.
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  • 9
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    Parametric analysis of radiative structure in aerobrake shock layers (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 30; 1; p. 51-58.
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  • 10
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    Calculated electron number density profiles for the aeroassist flight experiment (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 29; 5; p. 621-626.
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