The Surface Protected Ablator (SPA) is a lightweight and cost effective thermal protection for single use reentry capsules. It is characterised by a combination of load carrying structure, ablator and abrasion protection system. A simulation software has been developed to predict the thermal behaviour of the SPA during plasma wind tunnel tests and under atmospheric reentry conditions. Test samples have been exposed to different aerothermal heat fluxes. Test results have been used to calibrate the numerical model and to determine unknown properties of the ablative material. The calibrated model was applied for accurate flight predictions of the MIRKA reentry.