A spacecraft entering an atmosphere experiences high heat fluxes giving rise to the need ofthermal protection systems. Materials necessary for thermal protection are investigatedin various ground facilities and one of the important parameters that has to be computedis the heat flux at the stagnation region. The heat flux envelope of the mini-radiation andarc-jet facilities using a copper cylinder probe is investigated in this thesis. The heat fluxprobe used in the investigation was calibrated against a null point calorimeter; tests wereconducted by permuting different parameters and the effect of the varied parameter was studied. The variation in static chamber pressure was found to be the major contributorin the fluctuation of heat flux in both the facilities.

The radiative heat flux investigation tests allowed to conduct in-situ ablation tests. Thein-situ ablative tests with X-ray tomography were done for DLR-cork and ZURAM materials.The tests further showed the degradation of material inside the chamber on areal-time basis leading to better understanding of the structural changes in materials dueto high directional heat loads. In-situ tests with the arc-jet facility and comparative studiesusing the same testing conditions with different material models will provide a goodfollow-up to this research.