Operational behavior of inductively heated plasma source IPG3 for entry simulations

The design of the plasma wind tunnel (PWK3), its inductively heated plasma generator (IPG3), and experimental results using O-2 and CO2 as operational gases are described. Various operational conditions (mass flow rate, frequency) were applied. The thermal plasma powers measured with a calorimeter in the chamber of PWK3 are presented, leading to the possibility to determine efficiencies. When the power was varied, two discrete operational transitions were observed. The simultaneous differences in the discharge behavior of IPG3 are represented by sudden changes of parameters such as calorimetric powers and local heat fluxes measured with a stationary heat flux probe in the chamber of the facility. Additionally, the cooling power of the IPG3 plasma tube is presented. Here, a plasma stabilization effect appearing with the second operational transition was observed when the tube cooling power decreased suddenly despite the simultaneous increase of the plasma power in the chamber. An imaging spectrometer measuring the radial intensity of the plasma through an axial optical window of IPG3 was used. Both the operational behavior, in particular the stabilization effect, and the heat flux measurements show that PWK3 enables high-enthalpy tests for both basic thermal protection material tests and atmospheric entry simulation of spacecrafts.