Catalysis of Metallic and Ceramic TPS-Materials

Abstract

A facility for the determination of total and spectral emission coefficients is described. Values of measured total emission coefficients of the different high temperature ceramics such as HfO2, Al2O3, Yt2O3 and the metals/alloys Tungsten, TZM and PM1000 in the temperature regime of 750-1800 K are given. The drastic influence of the oxidation state of PM1000 on the emissivity is discussed. Additionally, results of an investigation of the influence of surface roughness and surface topology on emissivity are presented. Therefore, three SSiC samples with root-mean-squared roughness surface roughness from Rq = 0.05 to Rq = 0.66 have been prepared using common finishing operations. The tests showed that the emissivity increased about 10 % with an increase of the surface roughness even in the regime where Rq values are in the same magnitude or much smaller than the maximum emitting wavelength. Knowledge on emissivity is a basis for the analysis of thermo-chemical behavior and related properties (i.e. recombination coefficients) as the two properties influence each other. In a second step a high enthalpy inductively heated plasma wind tunnel (PWK3) is described and a methodology to derive recombination coefficients is explained. Recombination coefficients for the above mentioned materials have been determined in pure oxygen plasma. The methodology for the determination of recombination coefficients of ceramic and metallic Thermal Protection System (TPS) materials in single species gases used at IRS and its latest improvements are presented. Test results for the recombination coefficients in oxygen plasma are shown between 1469 and 2072 K.

Health Monitoring of TPS Structures by Measuring Their Electrical Resistance

“…There are various facilities at the Institute of Space Systems capable of creating a high temperature environment, for instance different plasma generators in the plasma wind tunnels 7,8) or the resistively heated graphite tube in the Emissivity Measurement facility (EMF) 9) .…”