Spectrum Modeling for Air Shock-Layer Radiation at Lunar-Return Conditions

Johnston, Christopher O.; Hollis, Brian R.; Sutton, Kenneth

doi:10.2514/1.33004

Cited by 143 publications

(79 citation statements)

References 46 publications

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“…The significant absorption from VUV molecular band systems shown in Figures 1 and 2 indicates that significant optically-thick absorption is encountered in an ablating or non-ablating boundary layer. The sufficient accuracy of the SRB model for the VUV absorption in a non-ablating boundary layer was shown by Johnston et al 46 . To assess the validity of the SRB model in the presence of ablation species, Figure 6 presents the VUV flux from layer 2 for = 0.4 and T 2 = 5,000 K. The spectrum and cumulative flux (starting from zero at 8 eV) obtained by ignoring all of the VUV band systems are represented by the dashed lines.…”

Section: Radiation Analysis Of a Simplified Ablating Shock Layermentioning

confidence: 89%

“…The details of this code for treating air species are presented by Johnston et al 46,47 . Briefly, it is based on a set of atomic levels and lines obtained from the National Institute of Standards and Technology (NIST) online database 48 and the Opacity Project 49 , as well as atomic bound-free cross sections from the TOPbase 50 .…”

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

“…The negative nitrogen and oxygen ions are treated using cross sections suggested by Soon and Kunc 51 and Chauveau et al 52 , respectively. The molecular band systems are treated using a smeared-rotational band (SRB) model 53 , which was shown by Johnston et al 46 to be sufficient for treating VUV absorbing and optically-thin emitting band systems in air. The accuracy of the SRB model for treating band systems resulting from ablation species is discussed in Section IV.…”

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

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Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2009

Journal of Spacecraft and Rockets

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Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative heating by 30 -60% and the convective heating by less than 5%. = thickness of the constant-property layers defined in Fig. 3, with i = 1 or 2 (cm) h = absorption coefficient (cm -1 ) = blowing reduction parameter = trasmissivity defined in Eq. (2) Subscripts h = indicates a spectral dependence in terms of eV Superscripts abl = refers to ablation species, meaning species containing any C or H atoms air = refers to air species, meaning species containing no C or H atoms Abbreviations eV = electron volts; the frequency in eV, labeled h , is equal to 1.24x10 -4 / c IR = infrared; refers here to the spectral region below 6 eV NIST = National Institute of Standards and Technology OP = Opacity Project VUV = vacuum ultraviolet; refers to the spectral region above 6 eV

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Section: Radiation Analysis Of a Simplified Ablating Shock Layermentioning

confidence: 89%

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

See 1 more Smart Citation

Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2009

Journal of Spacecraft and Rockets

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“…Two flight tests of the Apollo command modules were conducted at orbital (Apollo-09,11) and at super-orbital speeds (Apollo17,20) [13]. In the present the numerical investigation bases on some previously published works [14][15][16][17][18]. Detailed analysis of radiative gas dynamics of experimental space vehicles Fire-II and Stardust was presented in [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…Detailed analysis of radiative gas dynamics of experimental space vehicles Fire-II and Stardust was presented in [14,15]. Several recent publications were dedicated to studying the real re-entry conditions of super-orbital capsule [16,17]. Some analytical correlations for intensity of convective and radiative heating, based on a large number of numerical simulation results, were recently suggested in [18].…”

Section: Introductionmentioning

confidence: 99%

Spatial Multiphysics Models of the Radiation Gas Dynamics of Super Orbital Re-Entry Space Vehicles

Суржиков

2017

J. Phys.: Conf. Ser.

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Abstract. The multiphysics models of non equilibrium physical and chemical processes that should be considered together with radiative gas dynamic models for a description of the aero physics of super-orbital space vehicles are described.As an example of application of the multiphysics approach a three-dimensional numerical simulation analysis of radiative gas dynamics of Apollo-17 command module is analyzed. The results of calculations are compared with other numerical predictions, analytical correlations, and available experimental data.

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Introduction to Hypersonic Flow

Gaitonde

2010

Encyclopedia of Aerospace Engineering

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This chapter introduces the main aerodynamic physical phenomena encountered in hypersonic flow. The vehicle environment is first set into context by examining flight paths of typical vehicles, for missions from ballistic to access‐to‐space. The principal engineering problems arising in the harsh environment are outlined together with preliminary considerations on the manner in which these impact the mission‐dependent shape of the vehicle. The physics of high‐speed flow are introduced by first discussing strong inviscid and viscous interactions encountered at higher Mach numbers. This is followed by a brief description of some of the most striking features distinguishing hypersonic from supersonic flow. These include high‐altitude low‐density effects that need recourse to molecular dynamics, thermo‐chemistry effects that are triggered at high temperatures and enthalpies, the effects of ablation for thermal protection, the potential impact of thermal radiation, and the newly energized field of flow control with natural or artificially enhanced ionization.

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Spectrum Modeling for Air Shock-Layer Radiation at Lunar-Return Conditions

Cited by 143 publications

References 46 publications

Influence of Ablation on Radiative Heating for Earth Entry

Influence of Ablation on Radiative Heating for Earth Entry

Spatial Multiphysics Models of the Radiation Gas Dynamics of Super Orbital Re-Entry Space Vehicles

Introduction to Hypersonic Flow

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