Non-Boltzmann Modeling for Air Shock-Layer Radiation at Lunar-Return Conditions

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

doi:10.2514/1.33006

Cited by 110 publications

(59 citation statements)

References 34 publications

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“…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 molecular data for modeling these band systems are obtained from Laux 54 , except for the VUV N 2 systems, which are obtained from various other sources 55,56,57 . The non-Boltzmann modeling of the atomic and molecular electronic states is based on a set of electron-impact excitation rates compiled from the literature and presented in detail by Johnston et al 47 . Following the work of Park 58 , the quasi-steady state assumption is made when solving the Master Equation.…”

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 Modeling Of Air With Ablation Productsmentioning

confidence: 99%

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2009

Journal of Spacecraft and Rockets

Self Cite

View full text Add to dashboard Cite

show abstract

“…The details of this code for treating air species are presented by Johnson, et al 5,6 . Briefly, it is based on a set of atomic levels and lines obtained from the National Institute of Standards and Technology (NIST) online database 27 and the Opacity Project 28 , as well as atomic bound-free cross sections from the TOPbase 29 .…”

Section: Details Of the Non-equilibrium Radiation Modelmentioning

confidence: 99%

“…The molecular data for modeling these band systems are obtained from Laux 33 , except for the VUV N2 systems, which are obtained from various other sources [34][35][36] . The non-Boltzmann modeling of the atomic and molecular electronic states is based on a set of electron-impact excitation rates compiled from the literature and presented in detail by Johnston, et al 6 . Following the work of Park 37 , the quasi-steady state assumption is made when solving the Master …”

Section: Details Of the Non-equilibrium Radiation Modelmentioning

confidence: 99%

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Comparison of DSMC and CFD Solutions of Fire II Including Radiative Heating

Liechty

Johnston

Lewis

2011

42nd AIAA Thermophysics Conference

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The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. These flows may also contain significant radiative heating. To prepare for these missions, NASA is developing the capability to simulate rarefied, ionized flows and to then calculate the resulting radiative heating to the vehicle's surface. In this study, the DSMC codes DAC and DS2V are used to obtain charge-neutral ionization solutions. NASA's direct simulation Monte Carlo code DAC is currently being updated to include the ability to simulate charge-neutral ionized flows, take advantage of the recently introduced Quantum-Kinetic chemistry model, and to include electronic energy levels as an additional internal energy mode. The Fire II flight test is used in this study to assess these new capabilities. The 1634 second data point was chosen for comparisons to be made in order to include comparisons to computational fluid dynamics solutions. The Knudsen number at this point in time is such that the DSMC simulations are still tractable and the CFD computations are at the edge of what is considered valid. It is shown that there can be quite a bit of variability in the vibrational temperature inferred from DSMC solutions and that, from how radiative heating is computed, the electronic temperature is much better suited for radiative calculations. To include the radiative portion of heating, the flow-field solutions are post-processed by the non-equilibrium radiation code HARA. Acceptable agreement between CFD and DSMC flow field solutions is demonstrated and the progress of the updates to DAC, along with an appropriate radiative heating solution, are discussed. In addition, future plans to generate more high fidelity radiative heat transfer solutions are discussed.

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Prediction of Stagnation-Point Radiative Heating for FIRE II

Park

Kwon

2019

31st International Symposium on Shock Waves 2

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Non-Boltzmann Modeling for Air Shock-Layer Radiation at Lunar-Return Conditions

Cited by 110 publications

References 34 publications

Influence of Ablation on Radiative Heating for Earth Entry

Influence of Ablation on Radiative Heating for Earth Entry

Comparison of DSMC and CFD Solutions of Fire II Including Radiative Heating

Prediction of Stagnation-Point Radiative Heating for FIRE II

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