Investigation of High-Enthalpy Air Plasma Flow with Electrostatic Probes

At the Institute for Space Systems of the University of Stuttgart, four plasma wind tunnels are in operation to investigate the thermochemical behavior of thermal protection systems of various space vehicles during planetary entries. To achieve a detailed understanding of the plasma conditions in a plasma wind tunnel and of the erosion mechanisms of thermal protection materials, a specific flight condition on the re-entry trajectory of a winged vehicle has been investigated experimentally and numerically over the past few years. Electron temperatures, electron densities, plasma potentials, electron energy functions, and particle velocities of the air plasma flow generated by a magnetoplasmadynamic plasma generator were investigated by cylindrical electrostatic single, double, and triple probes. Plasma velocities were determined with time-of-flight probes, taking advantage of natural fluctuations of the ion current densities in the air plasma flow. Using the ratio of directed aud thermal ion velocities related to currents of parallel- and perpendicular-oriented probes according to the Kanal theory, the ion temperature is estimated. (Author)