Testing of the EXPERT thermal protection system junction in a plasma wind tunnel

The European Space Agency EXPERT vehicle thermal protection system is composed of a ceramic nose and a metallic body skirt, such that a transition in the recombination efficiency occurs when the plasma flow travels across their junction during the reentry phase. In this situation a heat flux jump is experienced between the two materials and has to be carefully handled for a safe vehicle design. Ground experiments in the induction-coupled plasma wind tunnel of the von Karman Institute are performed, in order to simulate this flight phenomenon. Three probe models (low catalytic, high catalytic and combined low-high catalytic) are tested and the temperature distributions over the samples are measured by means of infrared techniques. An experimental proof and a quantification of the transition are provided. Air recombination coefficients for the material studied are determined under typical flight conditions.