Thermal capacitance calorimeters are the standard instrument used to measure cold wall heat fluxes in high-enthalpy flows that simulates hypersonic flight conditions. These instruments play a fundamental role in the development and testing of Thermal Protection Systems for space re-entry conditions. However, despite their rugged and simple design, they are affected by large uncertainty errors. These have been estimated in literature at 15%. Despite their importance, and large errors, no proper uncertainty analysis has been performed. Uncertainty analysis is difficult due to the complex physics of the environment these calorimeters have to operate into
