Space shuttle overheating during the re-entry phase, due to catalytic oxygen recombination on the surface, is a problem of practical and theoretical interest. The energy transfer is characterized by the product of the accomodation coefficient Beta, and the recombination coefficient Gamma. The Gamma coefficient determines the atoms transfer to the surface, while the Beta coefficient defines the heat transfer, and their determination for a material allows to characterize it in terms of catalicity. Another aspect of this study is the quick ageingof the material. Insofar, modifications are supposed to occur, during the first milliseconds of the exposition to the atomic flow, we have used pulsed discharges of 200 milliseconds. In the post-discharge, we measured characteristic temperature increasing of a material, which allowed to establish a catalycity scale. Then 'gamma' measurements were performed in the pulsed discharge, in order to qualify these samples in terms of absolute catalycity. According to the literature, both experiments confirm one another. The experimental set-up enables quick 'GAmma' measurements with good precision of about 40 %. At last, surface analyses by X Photoelectron Spectroscopy complement a good knowledge of the short ageing effects.
Catalycity measurements on metallic surfaces in a pulsed plasma reactor
Katalyzitätsmessungen auf metallischen Oberflächen in einem Impulsplasmareaktor
1995
8 Seiten, 1 Bild, 6 Tabellen, 3 Quellen
Conference paper
English
Catalycity measurements on metallic and SiC material surfaces, in a pulsed plasma reactor
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