Heterogeneous catalytic recombination reactions including energy accommodation considerations in high enthalpy gas flows

Abstract

For many years different plasma wind tunnel facilities have been in operation all over the world in order to simulate the thermal and chemical loads a space vehicle is exposed to while returning to earth or entering the atmospheres of other celestial bodies. Parallel to the construction of the different plasma generators, e.g. magnetoplasmadynamic, thermal or inductively heated plasma sources, diverse plasmadiagnostic tools and measurement techniques have been developed. At the Institut fur Raumfahrtsysteme of the University of Stuttgart, where four plasma wind tunnels (PWK1-4) are operated, besides optical measurement techniques and diverse mechanical and electrostatic probes, a mass spectrometer as well as different heat flux probes are in use. Especially the results obtained by the last two diagnostic tools are strongly influenced by the catalytic effects of the used probe material and in the case of heat flux measurements additionally possibly by incomplete energy accommodation. Within this paper mass spectrometric results carried out using an inlet system coated with different materials as well as results of numerical simulations of the mass spectrometer orifice flow using different inlet geometries are presented and discussed. Additionally, heat flux measurements in the orifice plane of the mass spectrometer were performed in order to obtain qualitative information about the energy accommodation of the diverse coatings. Finally a concept for an energy accommodation probe is proposed and first results are presented and discussed.