Prediction of the Aerothermodynamic Environment of the Huygens Probe

Hollis, Brian R.; Striepe, Scott A.; Wright, Michael J.; Bose, Deepak; Sutton, Kenneth; Takashima, Naruhisa

doi:10.2514/6.2005-4816

Cited by 17 publications

(14 citation statements)

References 24 publications

(23 reference statements)

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“…The flowfield solutions obtained with the VSL method developed for this study were found to compare well with the Navier-Stokes solutions of previous studies 1 . Figure 1 presents the temperature profiles for the three trajectory points.…”

Section: The Viscous Shock-layer Stagnation Line Flowfieldsupporting

confidence: 65%

“…Only the stagnation line flowfield was considered in the present study, although the same method may be used to obtain solutions downstream of the stagnation line. Chemical nonequilibrium was treated following the work of shown to give good agreement with the shock standoff and convective heating predicted by previous analyses 1 . A constant wall temperature of 2000 K was assumed for all cases and a wall emissivity of 0.9 was used for the radiation coupling calculation.…”

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

“…A review of these studies leads to the conclusion that this uncertainty may be attributed to three primary sources: 1) the accuracy of the CN violet and red molecular band spectral representations (these band systems contribute the majority of the radiation at Huygens entry conditions); 2) the influence of radiation-flowfield coupling; 3) the accuracy of the kinetic scheme required for modeling the CN electronic state populations. 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…”

mentioning

confidence: 93%

“…A constant wall temperature of 2000 K was assumed for all cases and a wall emissivity of 0.9 was used for the radiation coupling calculation. This wall temperature was chosen to approximately match the radiative equilibrium wall values obtained in previous studies 1 . Therefore, the effect of radiation on the equilibrium wall temperature, which should have a negligible influence on the flowfield calculation, is not accounted for in this study.…”

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

“…The present study will concentrate on the three peak heating trajectory points identified in previous studies 1 . These conditions are shown in Table 1.…”

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

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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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Section: The Viscous Shock-layer Stagnation Line Flowfieldsupporting

confidence: 65%

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

mentioning

confidence: 93%

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

“…The present study will concentrate on the three peak heating trajectory points identified in previous studies 1 . These conditions are shown in Table 1.…”

Section: The Viscous Shock-layer Stagnation Line Flowfieldmentioning

confidence: 99%

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Radiative Heating Methodology for the Huygens Probe

Johnston

Hollis

Sutton

2007

Journal of Spacecraft and Rockets

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Dynamic characteristics of MarcoPolo-R Entry Capsule in low subsonic flow

et al. 2015

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On binary scaling and ground-to-flight extrapolation in high-enthalpy facilities

Looringhe¹,

Arwid²

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The binary scaling law is commonly used to study the aerothermodynamics of hypersonic vehicles in high-enthalpy facilities. It enables the duplication of the shock layer in the vicinity of the stagnation point, including binary chemistry and nonequilibrium processes, through the reproduction of the Péclet and wall Damköhler numbers. These are both conserved through the duplication of the composition of the gas, the free-stream enthalpy h ∞ and the product of a density and a length-scale of the flow ρL.Binary scaling is built on the assumption of a flow devoid of radiation coupling and governed by binary reactions. These two conditions drastically narrow down the envelope of flows for which binary scaling can be used. Moreover, diffusive transport and wall chemistry have never been addressed although they can have an important impact on the wall heat flux.The first part of this thesis consists in an effort to better understand the theoretical role and effect of the different assumptions done to build the binary scaling. It is first shown that diffusive transport and wall chemistry should scale appropriately. Second, that non-binary chemistry will cause the shock layer in the laboratory flow to be hotter and less dissociated. A methodology is proposed to identify clearly what free-stream conditions will affect the least the flow variables of interest. Lastly, that radiation coupling will be weaker in the laboratory flow than in flight, causing the enthalpy contained in the shock layer to be greater in the laboratory flow.These findings are verified in the second part with two experiments. The first experiment was performed in the Plasmatron plasma wind tunnel at the von Karman Institute, Belgium. Binary scaled boundary layers were obtained for flows where diffusion and wall chemistry contribute significantly to the heat flux. The stagnation point heat fluxes were measured and exhibit a good agreement with the theoretical scaling law. This also validates the use of the binary scaling law in subsonic high-enthalpy facilities.The second experiment was performed in the X2 expansion tube at the Centre for Hypersonics, Australia. Three flows were obtained over cylinders of different radii, adapting the free-stream density according to the binary scaling law. The free-stream conditions were determined in order to ensure a significant radiative coupling. Its effect could clearly be identified through measurements of the shock standoff distance, stagnation point heat flux, and shock layer radiation. A new method, based on a mix of experiments, computational fluid dynamics, and informed use of engineering correlations is proposed to perform ground to flight extrapolation for cases for which the radiative coupling is non-negligible. Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have include...

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Prediction of the Aerothermodynamic Environment of the Huygens Probe

Cited by 17 publications

References 24 publications

Radiative Heating Methodology for the Huygens Probe

Radiative Heating Methodology for the Huygens Probe

Dynamic characteristics of MarcoPolo-R Entry Capsule in low subsonic flow

On binary scaling and ground-to-flight extrapolation in high-enthalpy facilities

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