The qualification of thermal protection systems (TPS) and numerical de
sign tools for re-entry vehicles and space probes requires the ability
to understand and duplicate the prevailing complex physico-chemical p
henomena, including thermal and chemical nonequilibrium near the surfa
ce of a body that enters the atmosphere of the Earth or another celest
ial body. At the Institut fur Raumfahrtsysteme of the University of St
uttgart, four plasma wind tunnels (PWK1-4) are in operation to simulat
e the thermal, aerodynamic, and chemical loads on the surface of a spa
ce vehicle. Three different plasma sources have been developed for thi
s purpose: 1) a magnetoplasmadynamic generator for the simulation of t
he high-enthalpy and low-pressure environment during the first phase o
f re-entry, 2) a thermal arcjet device for the follow-on night path at
moderate specific enthalpies and higher stagnation pressures, and 3)
an inductively heated generator for basic materials experiments over a
wide range of specific enthalpies and pressures. Special efforts were
made to avoid electrode erosion to preclude impairing the erosion and
catalytic behavior of TPS materials. A detailed description of these
plasma generators and an overview of the simulation regions and operat
ion areas of the plasma wind tunnels are presented.