A Code Calibration Study for Huygens Entry Aeroheating

Wright, Michael J.; Olejniczak, Joseph; Walpot, L.; Raynaud, E.; Magin, Thierry; Caillaut, Lise; Hollis, Brian R.

doi:10.2514/6.2006-382

Cited by 20 publications

(17 citation statements)

References 15 publications

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“…This has led to investigations into the heating environments encountered during entry into various atmospheric compositions [1][2][3]. During high-speed entry into atmospheres such as Titan, the CN molecule is formed in concentrations above equilibrium [1,2,4,5].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Nonequilibrium CN Radiation Encountered During Titan Atmospheric Entry

Brandis

Morgan

McIntyre

2011

Journal of Thermophysics and Heat Transfer

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The focus of this paper is to analyze the Titan reaction scheme and determine the mechanisms that control the formation and decay of the radiation emitted by the cyanogen molecule (CN) during entry into Titan's atmosphere. Through a parametric study of important reactions combined with an investigation into reaction pathways, it has been concluded that the coupling between the dissociation of N 2 and the formation of the CN (through the reaction N 2 C $ CN N) controls the radiation decay rate. The reason for the super equilibrium concentrations (approximately 50% higher than equilibrium) was identified to be a result of the N 2 C $ CN N reaction continuing to overproduce the CN after nominal equilibrium values were reached. This is due to the slow buildup of N to drive the reverse reaction. The absolute level of emitted radiation has been shown to be controlled by the lifetime of the CNB state and the excitation of CNX to CNB by heavy particle impact. Thus, it is the conclusion of this paper that CN radiation is primarily controlled by N 2 dissociation.

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Section: Introductionmentioning

confidence: 99%

Analysis of Nonequilibrium CN Radiation Encountered During Titan Atmospheric Entry

Brandis

Morgan

McIntyre

2011

Journal of Thermophysics and Heat Transfer

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“…The second step is the measurement of nonequilibrium spectra, producing data for the development of electronically and vibrationally resolved collisional-radiative models. As stated earlier, the nonequilibrium flow conditions in the immediate postshock region present during entry or aerocapture in the atmosphere of Titan, which have been computed for flight conditions [1][2][3][4][5][6][7][8][9] or simulated in shock tubes [14][15][16][17], cannot be replicated in the facility used for the present investigation. Moreover, the total specific enthalpy of the VKI Minitorch facility, which was in the range of 8-10 MJ=kg on the jet axis, is rather low with respect to the required values ranging from 12.5 to 15 MJ=kg for peak radiative heating of the Huygens entry [9].…”

Section: Introductionmentioning

confidence: 99%

“…E VEN if performed at moderate speed (6-10 km=s) [1][2][3][4][5][6][7], entry or aerocapture maneuvers in the atmosphere of Titan are characterized by significant radiation emission in the shock layer surrounding the space probe. This strong emission is due to the composition of the atmosphere of Titan, which is mainly composed of nitrogen with a small percentage of methane.…”

Section: Introductionmentioning

confidence: 99%

Erratum on Spectroscopic Analysis of Titan Atmospheric Plasmas

Playez

Fletcher

2008

Journal of Thermophysics and Heat Transfer

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“…The column labeled "coupled-TW" presents the coupled radiative heating predicted using the Tauber-Wakefield approximate method 3 . This method depends on the uncoupled radiative heating and a constant, κ, which has been assumed equal to 2 in previous studies 1,2 . The present results show that this method over predicts the effect of coupling for the first two trajectory points.…”

Section: Uncoupled and Coupled Radiative Heating Assuming A Boltzmentioning

confidence: 99%

“…The first of these was made clear by Hollis et al 1 , who showed that two widely used radiation codes, NEQAIR and RAD/EQUIL, disagreed by a factor of two for Huygens conditions. Wright et al 2 have since…”

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confidence: 99%

Radiative Heating Methodology for the Huygens Probe

Johnston

Hollis

Sutton

2007

Journal of Spacecraft and Rockets

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The radiative heating environment for the Huygens probe near peak heating conditions for Titan entry is investigated in this paper. The task of calculating the radiation-coupled flowfield, accounting for non-Boltzmann and non-optically thin radiation, is simplified to a rapid yet accurate calculation. This is achieved by using the viscous-shock layer (VSL) technique for the stagnation-line flowfield calculation and a modified smeared rotational band (SRB) model for the radiation calculation. These two methods provide a computationally efficient alternative to a Navier-Stokes flowfield and line-by-line radiation calculation. The results of the VSL technique are shown to provide an excellent comparison with the Navier-Stokes results of previous studies.It is shown that a conventional SRB approach is inadequate for the partially optically-thick conditions present in the Huygens shock-layer around the peak heating trajectory points. A simple modification is proposed to the SRB model that improves its accuracy in these partially optically-thick conditions. This modified approach, labeled herein as SRBC, is compared throughout this study with a detailed line-by-line (LBL) calculation and is shown to compare within 5% in all cases. The SRBC method requires many orders-of-magnitude less computational time than the LBL method, which makes it ideal for coupling to the flowfield. The application of a collisional-radiative (CR) model for determining the population of the CN electronic states, which govern the radiation for Huygens entry, is discussed and applied. The non-local absorption term in the CR model is formulated in terms of an escape factor, which is then curve-fit with temperature. Although the curve-fit is an approximation, it is shown to compare well with the exact escape factor calculation, which requires a computationally intensive iteration procedure.

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A Code Calibration Study for Huygens Entry Aeroheating

Cited by 20 publications

References 15 publications

Analysis of Nonequilibrium CN Radiation Encountered During Titan Atmospheric Entry

Analysis of Nonequilibrium CN Radiation Encountered During Titan Atmospheric Entry

Erratum on Spectroscopic Analysis of Titan Atmospheric Plasmas

Radiative Heating Methodology for the Huygens Probe

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