Recent Improvements of the Parallel-Multiblock URANUS 3D Nonequilibrium Code

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Recent Improvements of the Parallel-Multiblock URANUS 3D Nonequilibrium Code M. Fertig 1 , F. Infedl, F. Olawskyl, M. Auweter-Kurtzl, and P. Adamidis 2 1

Institute of Space Systems, Pfaffenwaldring 31, 70550 Stuttgart, Germany

2

Rechenzentrum der Universitat Stuttgart, Allmandring 30, 70550 Stuttgart, Germany adamidis®b.Irs. de

fertig~irs.uni-stuttgart.de

The 3D Parallel-Multiblock URANUS code has been extended by models for radiative exchange between the surface elements and for heat conduction within the TPS (Thermal Protection System). The coupling of the newly developed models with catalytic effects for the real TPS, predicted by a global catalysis model, and with temperature dependent emissivity leads to significant differences in surface temperature distribution. Results for the X-38 re-entry vehicle will be discussed in some detail. Large memory and computational time requirements arise in order to solve the non-equilibrium NavierStokes equations on 1.02 million cells coupled with the surface models.

1 Introduction For the development of reusable space transport systems, a detailed prediction of the thermal loads during re-entry is essential. If reliability can be proved, a partial catalytic TPS design would result in low weight TPS. For this purpose the DRANDS (Upwind Relaxation Algorithm for Nonequilibrium Flows of the University of Stuttgart) code for hypersonic non-equilibrium flows has been developed at the Institute of Space Systems IRS of the University of Stuttgart in cooperation with the HLRS within SFB 2593 • X-38 is an example of a re-entry vehicle which is thermally highly loaded within a large trajectory range. It was equipped with an advanced reusable TPS, consisting of SiC-based ceramics at the high temperature areas, such as stagnation point and body flap regions, and Si0 2 shuttle tiles for the colder surface areas. Along the upper trajectory, a dissociated, laminar non-equilibrium flow exists which leads to significant catalytic reactions at the surface. Redox reactions coupled 3

Sonderforschungsbereich 259, Collaborative Research Center 259: "High Temperature Problems of Reusable Space Transportation Systems"

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M. Fertig, F. Infed, F. Olawsky, M. Auweter-Kurtz, and P. Adamidis

to catalytic reactions leading to passive and possibly active oxidation become important in the high-temperature areas, especially at the body flaps where free surface radiation is partially hindered due to their installation in a cavity. Up to now, the heat shield design was based on the fully catalytic design assumption. In the present paper, X-38 surface temperature distributions are computed with the advanced URANUS non-equilibrium code, where the influential gas-surface interaction is taken into account by a global catalysis model with temperature-dependent overall recombination coefficients for SiC and Si0 2 measured by Stewart.[I8] With this formulation the measured forebody surface heat flux along the integral CjC-SiC heat shield of the MIRKA [5] capsule was reconstructed satisfactorily along the trajectory. Heat flux within the TPS material tends to decrease surface temperature in highly loaded arC&"> while temperature in moderately loaded surface arc&"> increases. Within this paper significant surface temperature uncertainties dependent on the coupling of the different models are shown. Note that the results given here have already been discussed previously.[IO]

2 URA.NUS Code In the Parallel-Multiblock (P-MB) URANUS Nonequilibrium Navier-Stokes code the governing equations in finite volume formulation are solved fully coupled.[8] The Navier-Stoke.