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In this study we investigate the interaction of pyrolysis gas from an ablating material with different, high-temperature gases present in the thermal boundary layer formed over the material in a plasma test facility. We present information on the impact of pyrolysis gas on the heat flux, the thermo-chemistry and the flow pattern at the stagnation point in the near surface region. A parallel investigation of pyrolysis using a simulation probe is also presented. The simulation probe provides a steady CO 2 gas flow into the oncoming plasma flow through a porous graphite plug to mimic the release of gas through the charred layer of an actual ablator. Tests are performed in pure N 2 , air and CO 2 plasma flows. All experiments are conducted in the 30 kW Inductively Coupled Plasma (ICP) Torch Facility at the University of Vermont. Data are presented for varying gas injection velocities and plasma chamber pressures and the results are compared with tests of a phenolicimpregnated carbon ablator (PICA).

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Soft x-ray appearance spectroscopy is used to monitor nickel contamination levels in an iron substate during glow discharge sputter cleaning, most severe surface contamination is introduced from an electrically floatting stainless steel shield during dc sputter cleaning. Grounding the shield minimizes the contamination and rf sputtering virttually eliminates it.(AIP)