*3.1. Verification*

To verify the accuracy of the solver, the solution for non-ablative and non-decomposing materials can be compared with available analytical solutions. The solver is able to accurately predict the thermal response of a passive TPS. The details of this verification procedure can be found in Appendix A. As there is no known analytical solution for the decomposing case, a comparison with other programs is performed. For this purpose, the theoretical ablative composite for open testing (TACOT) material is used, and the results presented by Lachaud et al. in [33] are used for verification. For the considered verification sample, a 7% higher recession was obtained by Hot-STARSHIP compared to the software presented in [33] (PATO or Amaryllis). The final difference between the results of the two solvers for the back-face temperature is about 12 K, and the average difference is even lower as the two curves cross each other (Appendix A, Figure A2). This is considered to be accurate enough for fast preliminary design purposes and for mass optimisation.
