Photogrammetric Measurement of Recession Rates of Low Temperature Ablators in Supersonic Flow

Callaway, David W.; Reeder, Mark F.; Greendyke, Robert B.; Gosse, Ryan; Afb, Wright-Patterson

doi:10.2514/6.2010-1216

Cited by 10 publications

(4 citation statements)

References 13 publications

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“…For a flight vehicle to survive in this environment, it requires a thermal protection system (TPS) composed of materials that can withstand extreme heat fluxes and temperatures. 1 Ablative, carbon-based TPS materials are often used, and are classified as porous (volumetric) ablators and non-porous (surface) ablators. Although the details of the ablation process differ in porous and non-porous ablators, the oxidation of carbon is central to the ablation of any carbon-based TPS.…”

Section: Introductionmentioning

confidence: 99%

Finite-rate oxidation model for carbon surfaces from molecular beam experiments

Poovathingal

Schwartzentruber

Murray

et al. 2016

46th AIAA Thermophysics Conference

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An oxidation model for carbon surfaces is developed where the gas-surface reaction mechanisms and corresponding rate parameters are based solely on observations from recent molecular beam experiments. In the experiments, a high energy beam of oxygen (93% atoms and 7% molecules) was directed at a high-temperature carbon surface. The measurements revealed that CO was the dominant reaction product and that its formation required a high surface coverage of oxygen atoms. As the carbon sample temperature was increased during the experiment, the surface coverage was reduced and the production of CO diminished. Most importantly, the measured time-of-flight distributions of surface reaction products indicated that CO and CO2 were predominately formed through thermal reaction mechanisms and not impulsive reactive scattering. These observations enabled the formulation of a finite-rate oxidation model including surface-coverage dependence, similar to existing finite-rate models used in computational fluid dynamics (CFD) simulations. However, each reaction mechanism and all rate parameters of the new model are determined individually based on the molecular beam data. The new model is compared to existing models using both zero-dimensional gas-surface simulations and full CFD simulations of hypersonic flow over an ablating surface. The new model predicts similar overall mass loss rates compared to existing models, however, the individual species production rates are completely different. The most notable difference is that the new model (based on molecular beam data) predicts CO as the oxidation reaction product with virtually no CO2 production, whereas existing models predict the exact opposite trend.

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Section: Introductionmentioning

confidence: 99%

Finite-rate oxidation model for carbon surfaces from molecular beam experiments

Poovathingal

Schwartzentruber

Murray

et al. 2016

46th AIAA Thermophysics Conference

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“…Materials used in previous studies are not well-suited for liquid ablation experiments in shock tunnels. Naphthalene [13] and camphor [14] made of water ice [8] or CO2 ice [9] melt and also evaporate during the test preparation.…”

Section: B Low Temperature Ablating Metalmentioning

confidence: 99%

“…While they are well suited for material analysis under stagnation point flow conditions, they are not able to reproduce the aerothermodynamics experienced by a hypersonic model. However, some recent ablation experiments were carried out in hypersonic shock tunnels but they used low temperature ablators such as water ice [8] or dry ice [9] instead of an ablating metal.…”

mentioning

confidence: 99%

Experimental Investigation of Thermal Ablation by Melting in a Hypersonic Shock Tunnel

Denis¹,

Hruschka²,

Bastide³

et al. 2022

Journal of Spacecraft and Rockets

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In this paper a novel approach for the experimental measurement of the ablation by melting is presented. The experiments are carried out with a hypersonic shock tunnel. The tested models are made of gallium, which melts at low temperatures, allowing the generation and then the measurement of the ablation profiles within only two milliseconds. By means of an optical visualization, the model surface changes are recorded during the experiment. An image post-processing algorithm computes the ablation profiles. The results for two hemisphere-cone models and one hemisphere-cylinder model in a Mach 4.5 nitrogen flow are presented. It is found that the maximum ablation occurs at an angular position of around 30 degrees off-axis rather than at the stagnation point. This is most likely a consequence of the laminar-turbulent transition on the model forebody. Nomenclature Cp= Heat capacity at constant pressurenumber [−] P = Pressure [Pa] or Power flux [W • m −2 ] Re = Reynolds number [−] Re/x = Reynolds number per meter [m −1 ]

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“…3 While high temperature ablation is difficult and expensive to recreate in a laboratory environment and while high-temperature ablation is a very complex process involving nonequilibrium gaseous and surface chemistry, spallation, radiation, etc., low temperature ablation creates a limited physics problem that can be used to simulate the ablation process. Naphthalene, 4 camphor, 5 wax, 6 CO 2 (dry ice), 7 and water-ice 8 -all low-temperature sublimating ablators-have been used previously to study ablation, with camphor and CO 2 being employed most often. Determining ablation rates of cones, hemispheres, and other projectile-like models has been the focus of the majority of ablation studies performed using low-temperature sublimating ablators.…”

Section: Introductionmentioning

confidence: 99%

Development of Naphthalene PLIF for Visualizing Ablation Products from a Space Capsule Heat Shield

Combs

Clemens²,

Danehy

2014

52nd Aerospace Sciences Meeting

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The Orion Multi-Purpose Crew Vehicle (MPCV) will use an ablative heat shield. To better design this heat shield and others that will undergo planetary entry, an improved understanding of the ablation process would be beneficial. Here, a technique developed at The University of Texas at Austin that uses planar laser-induced fluorescence (PLIF) of a low-temperature sublimating ablator (naphthalene) to enable visualization of the ablation products in a hypersonic flow is applied. Although high-temperature ablation is difficult and expensive to recreate in a laboratory environment, low-temperature sublimation creates a limited physics problem that can be used to explore ablation-product transport in a hypersonic flow-field. In the current work, a subscale capsule reentry vehicle model with a solid naphthalene heat shield has been tested in a Mach 5 wind tunnel. The PLIF technique provides images of the spatial distribution of sublimated naphthalene in the heat-shield boundary layer, separated shear layer, and backshell recirculation region. Visualizations of the capsule shear layer using both naphthalene PLIF and Schlieren imaging compared favorably. PLIF images have shown high concentrations of naphthalene in the capsule separated flow region, intermittent turbulent structures on the heat shield surface, and interesting details of the capsule shear layer structure. It was shown that, in general, the capsule shear layer appears to be more unsteady at lower angels of attack. The PLIF images demonstrated that during a wind tunnel run, as the model heated up, the rate of naphthalene ablation increased, since the PLIF signal increased steadily over the course of a run. Additionally, the shear layer became increasingly unsteady over the course of a wind tunnel run, likely because of increased surface roughness but also possibly because of the increased blowing. Regions with a relatively low concentration of naphthalene were also identified in the capsule backshell recirculation region and are most likely the result of cross-flow-induced vortices on the capsule afterbody.

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Photogrammetric Measurement of Recession Rates of Low Temperature Ablators in Supersonic Flow

Cited by 10 publications

References 13 publications

Finite-rate oxidation model for carbon surfaces from molecular beam experiments

Finite-rate oxidation model for carbon surfaces from molecular beam experiments

Experimental Investigation of Thermal Ablation by Melting in a Hypersonic Shock Tunnel

Development of Naphthalene PLIF for Visualizing Ablation Products from a Space Capsule Heat Shield

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