Development and Testing of an Ablation Model Based on Plasma Wind Tunnel Experiments

Ablative materials are extensively used in several aerospace applications. Their employ
as heat shield for re-entry capsules enables to survive re-entry conditions that would be
otherwise unfeasible. The coupled experimental-numerical work is fundamental to grow the
understanding of their behavior in operative conditions. This work deals with the develop-
ment and testing of an ablation model able to reproduce the stagnation-point gas-surface
interaction over non-charring carbon-based ablative materials. Numerical tools, specifi-
cally developed at the von Karman Institute for Fluid Dynamics for re-entry application
studies, are used together in the analysis to obtain relevant quantities as the stagnation-
point surface mass blowing rate and temperature. Data from the experiments performed
in the von Karman Institute Plasmatron in both air and nitrogen environment are used
to compare with the numerical results and to tailor the ablation model. Test results in
nitrogen environment prove that active surface nitridation takes place, and a proper nitri-
dation reaction probability is extracted from the tests using the developed model with a
reverse approach. Comparisons with the measured surface temperatures suggest that ad-
ditional surface phenomena can occur in the low cold-wall heat flux tests. Surface nitrogen
recombination, identified as one of these possible mechanisms, is analyzed.

ISBN:978-1-62410-281-3

Publication year:2014

Keywords:ablation modelling