Computation of radiative and convective contributions to Viking afterbody heating

Potter, Daniel; Karl, Sebastian; Lambert, Markus; Hannemann, Klaus

doi:10.2514/6.2013-2895

Cited by 14 publications

(2 citation statements)

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“…To further confirm the importance of the afterbody radiation during Mars entry, in 2013, Potter et al [1] numerically investigated the hypothesis that the discrepancy between the thermocouple-derived heating on the afterbody of the Viking aeroshell and the respective CFD results is caused by the mid-infrared carbon dioxide radiation. The Viking aeroshell contained two thermocouples on the afterbody, as shown on Figure 2.1.…”

Section: Simulation Of Afterbody Radiation During Mars Entrymentioning

confidence: 99%

“…Protection of the entry vehicle afterbody is important for surviving atmospheric entry and preventing damage to the vital instruments which are normally contained in the rear of the entry vehicle. In the past, the effect of radiative heating on the afterbody of a Mars entry vehicle has been largely neglected [1]. Afterbody thermal protections were designed by considering only the convective heating [2].…”

Section: Introductionmentioning

confidence: 99%

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Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Gu¹

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This thesis presents an experimental study of high temperature CO2 flowsfocusing on CO2 flows subjected to rapidly expanding conditions relevant to Mars entry and representative of the corner expansion around the shoulder, between the windward and leeward flows, on an entry capsule. This is an important but poorly understood aspect of spacecraft design. Past numerical research showed that, during Mars entry, the CO2 4.3 µm and 2.7 µm band radiation from the aforementioned expanding flow produce non-negligible contributions to the heating of the capsule afterbody.Consequently, this radiative heating should be considered in the sizing of the afterbody thermal protection systems (TPS). However, due to a lack of experimental research, the nonequilibrium characteristics of CO2 expanding flows are not well understood. Therefore, to help with the design of future Mars entry vehicles, it is necessary to investigate such flows.The X2 expansion tube was used to facilitate the current study. Three expansion tube test conditions with differing velocitiesnominally 2.8 km/s, 3.4 km/s, and 4.0 km/swere developed. Using a two-dimensional wedge model with a 54° convex corner along with the new conditions, flows with similarities to the expanding flow around the shoulder of an aeroshell at certain Mars entry conditions were created. Mid-wavelength infrared emission spectroscopy of the 4.3 μm and 2.7 μm bands were performed on the flow. The spectroscopic measurements were used to estimate the rotational and vibrational temperatures and the CO2 number densities using a spectral fitting method. Supplementing the spectroscopic measurements, filtered images of the 4.3 μm and 2.7 μm bands were taken to provide a two-dimensional spatial map of the band radiance in the flow around the wedge. Estimates of the experimental inflow conditions were produced by solving for the intermediate test gas states using measurements of various properties of the operating condition. CO2 spectroscopic measurements of the inflow along with measurements of the wedge model shock location and deduced post-shock conditions were also used to help characterize the test conditions. Using estimated inflow conditions, three-dimensional CFD simulations of the experiments were conducted using a two-temperature model. The computed results were compared to the available measurements to examine the appropriateness of the current numerical model at simulating the CO2 flow.Important qualitative results were obtained in this thesis in regards to the high temperature CO2expanding flow. The temperatures estimated in the wedge flow using both the 2.7 and 4.3 µm spectroscopic measurements were found to be the same. This provides some confidence to the validity of NEQAIR, using CDSD-4000, at predicting CO2 radiation under gas-dynamic conditions which are more relevant to Mars entry. Using the estimated rotational and vibrational temperatures, the CO2 II thermal non-equilibrium in the expanding flow was shown to be smallless than 10%. As the experiments simulate the expanding fl...

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Section: Simulation Of Afterbody Radiation During Mars Entrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Gu¹

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Multi-objective Shape Optimization of Airfoils for Mars Exploration Aircraft Propellers

Park

Jung²,

Jeong³

2022

Int. J. Aeronaut. Space Sci.

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Predicting lift and drag coefficients during hypersonic Mars reentry using hyStrath

Maigler,

Pessina,

Schein

2024

Physics of Fluids

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During hypersonic reentry, a spacecraft experiences several different fluid flow regimes, which usually require the application of different software frameworks to simulate the respective regimes. This study aims to evaluate the hyStrath library for predicting aerodynamic lift and drag coefficients of complex three-dimensional (3D) geometries during hypersonic Mars reentry, using flight data of the Viking 1 mission as reference. A range of altitudes (h=30−140 km) and Mach numbers (M=13−24) where flight data is available is considered, covering the rarefied, transitional, and continuum fluid flow regimes. The hyStrath library contains a set of modified solvers and state-of-the-art thermophysical and chemistry models within the framework of OpenFOAM, dedicated to modeling high-enthalpy hypersonic flow problems. Depending on the flow regime, the computational fluid dynamics solver hy2Foam or direct-simulation Monte Carlo solver dsmcFoam+ are employed in the study. Because hyStrath is based on OpenFOAM, it allows the use of an unstructured adaptive mesh refinement approach for arbitrary geometries. We obtain excellent results throughout all investigated flow regimes and Mach numbers with an average deviation of 1.5% and 2% from the measured lift and drag coefficients, respectively. The applicability of the framework for accurately modeling both rarefied and continuum Mars reentry problems of complex 3D geometries such as the Viking capsule is demonstrated.

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Computation of radiative and convective contributions to Viking afterbody heating

Cited by 14 publications

References 8 publications

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

Multi-objective Shape Optimization of Airfoils for Mars Exploration Aircraft Propellers

Predicting lift and drag coefficients during hypersonic Mars reentry using hyStrath

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