An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

Dec, John A.; Braun, Robert D.

doi:10.2514/6.2006-780

Cited by 38 publications

(8 citation statements)

References 4 publications

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“…Previous researchers have used the charring material ablation (CMA) code for thermal protection sizing [10,21]. The CMA code solves the internal energy balance and decomposition equations coupled with the ablating surface energy balance condition [22].…”

Section: A Fully Implicit Ablation Thermal Materials Response Modelmentioning

confidence: 99%

Significance of Nonequilibrium Surface Interactions in Stardust Return Capsule Ablation Modeling

Beerman

Lewis

Starkey

et al. 2009

Journal of Thermophysics and Heat Transfer

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The gas-surface modeling of high-density materials exposed to high-pressure atmospheric reentry conditions was extended to include low-density materials interacting with low-pressure atmospheric conditions. The fully implicit ablation thermal response code and multicomponent ablation thermochemistry program were extended to include nonequilibrium surface conditions for the Stardust return capsule. The Stardust return capsule reentered Earth's atmosphere experiencing low pressure and had a low-density heat shield material. The material response of the Stardust return capsule was previously only modeled with surface equilibrium. Validation against Stardust reentry flight data showed that the equilibrium assumption led to an overprediction of recession and that the inclusion of nonequilibrium reduced the overprediction of this parameter. Incorporating the Park finite rate model nonequilibrium surface conditions led to a reduction in the calculated value of recession at the stagnation point from 1.12 to 0.72 cm in a nominal simulation of the Stardust return capsule. The nonequilibrium recession was closer to the measured recession of 0.65 cm. Incorporating nonequilibrium conditions also decreased the calculated total heat load from 28 to 19 kJ=cm 2 . The improved material response method is applicable to a range of reentries, including future missions such as the Orion crew exploration vehicle. NomenclatureB = preexponential factor, s 1 B 0 = dimensionless mass blowing rate, _ m= e u e C M C H = Stanton number for heat transfer C i = mass fraction for species i C M = Stanton number for mass transfer c p = specific heat, J=kg-K D i = diffusion coefficient for species i, m 2 =s E = activation temperature, K F = view factor H r = recovery enthalpy, J=kg h = enthalpy, J=kg h = partial heat of charring, J=kg k = Boltzmann constant, J=K M = molecular weight, kg=mole m = mass, kg _ m = mass flux, kg=m 2 s p = pressure, N=m 2 q c = conductive heat flux, W=m 2 q rad = radiative heat flux, W=m 2 T = temperature, K u = velocity, m=s v w = mass injection velocity, m=s x = moving coordinate system, y s, m Y = element mass fraction y = stationary coordinate, m = surface absorption = efficiency of gas-surface interaction = volume faction of resin " = surface emissivity = blowing reduction parameter = density, kg=m 3 = Stefan-Boltzmann constant, W=m 2 K 4 = decomposition reaction order Subscripts c = char d = density component e = boundary-layer edge g = pyrolysis gas i = surface species k = element or gaseous base species s = surface v = original w = wall

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Section: A Fully Implicit Ablation Thermal Materials Response Modelmentioning

confidence: 99%

Significance of Nonequilibrium Surface Interactions in Stardust Return Capsule Ablation Modeling

Beerman

Lewis

Starkey

et al. 2009

Journal of Thermophysics and Heat Transfer

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“…However, to account for the effects of the pyrolysis gas on the vehicle, the chemistry model of the flow field must include the reactions associated with the presence of this gas. Because ablation coupling is becoming an increasingly important research topic, [1][2][3][4][5][6][7] the development of an accurate, yet usable, chemistry model is of great importance. Models have been proposed in the past [8][9][10] but important reactions were not included, and some of the reaction rates were inappropriate or simply outdated.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of the CN spectral emission of the Stardust re-entry vehicle

Martin

Farbar²,

Boyd³

2011

42nd AIAA Thermophysics Conference

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Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain better predictions, an appropriate gas flow chemistry model needs to be included in the CFD calculations. Although more arc-jet experimental data is becoming available for model comparison, very little flight data exists for comparison and validation. However, because of the observation mission campaign led by NASA, data is available for the re-entry of the Stardust sample return vehicle, which employed a heat shield constructed of phenolic impregnated carbon ablator (PICA). Using a recently developed chemistry model for ablating carbon-phenolic-in-air species, a CFD calculation of the Stardust re-entry at 71 km is presented. The result demonstrates the need to account for different species in the flow field than the ones composing the pyrolysis gas. It is also shown that the main heat flux reduction phenomenon is through mass diffusion, and not through translational-rotational conduction, as is the case at higher altitude. The flow field solutions are also used to generate nonequilibrium radiation spectra, which are compared to the experimental data obtained during Stardust re-entry by the Echelle instrument. The predicted emission from the CN lines compares quite well with the experimental results, demonstrating the validity of the current approach.

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“…The present paper tries to improve on those models by addressing these omissions. Because ablation coupling is becoming an increasingly important research topic, [3][4][5][6][7][8][9] the development of an accurate, yet usable, chemistry model is of great importance.…”

Section: Introductionmentioning

confidence: 99%

Chemistry Model for Ablating Carbon-Phenolic Material During Atmospheric Re-Entry

Martin

Boyd²,

Cozmuta

et al. 2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Recent and future re-entry vehicle designs, such as the CEV, use ablative material as the main component of the heat shield of their thermal protection system. In order to properly predict the behavior of the vehicle, it is imperative to take into account the gases produced by the ablation process when modeling the reacting flow environment. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled in the boundary layer is complex and might lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain better predictions, a proper gas flow chemistry model needs to be included in the CFD calculations. The present paper proposes an extensive set of reactions that are relevant to carbon-phenolic ablators, such as PICA, the ablative material that was used on the Stardust return capsule and that will be used on the entry vehicle of the Mars Science Laboratory (MSL). Nomenclature A Pre-exponent factor B g Non dimensional pyrolysis gas rate B c Non dimensional surface ablation rate k Kinetic rate n Pre-exponent temperature power p Pressure ppm Parts per million S Non dimensional sensitivity T Temperature T a Activation temperature X Sensitive variable

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An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

Cited by 38 publications

References 4 publications

Significance of Nonequilibrium Surface Interactions in Stardust Return Capsule Ablation Modeling

Significance of Nonequilibrium Surface Interactions in Stardust Return Capsule Ablation Modeling

Numerical modeling of the CN spectral emission of the Stardust re-entry vehicle

Chemistry Model for Ablating Carbon-Phenolic Material During Atmospheric Re-Entry

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