Application of Pyrometry on High Enthalpy Facilities.

Abstract

Shock tunnels or hot shot facilities are used for the simulation of re-entry conditions in aerodynamic sense. But the short test duration of these facilities (in millisecond range) does not allow to study the thermal behaviour of re-entry vehicles. Because of their long testing time arc or induction heated facilities are very useful tools for the qualification of thermal protection materials. Depending on the trajectory and geometry of the vehicle surface temperatures up to 2000 K can be reached at critical parts of the vehicle during re-entry phase. Because of much higher gas temperatures around vehicles or test model, there is a strong chemical interaction between the gas and surface material. This fact limits the application of intrusive temperature measurement techniques like thermocouples, etc. Pyrometry is one of the most efficient non-intrusive measurement techniques for the determination of the surface temperature. Based on the spectral properties of the test models or high enthalpy gas in high enthalpy facilities, pyrometers have to be specified. Since the emissivity of different models may have strong spectral variations, a reliable matching between spectral properties of the pyrometer and model surface is necessary.