ELECTRON ATTACHING ADDITIVES FOR THE MODIFICATION OF RE-ENTRY PLASMAS
Scientific rept. no. 1
SPACE SCIENCES INC WALTHAM MA
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The report is part of an analytical and experimental program to investigate the enhancement of microwave communication by employing small quantities of chemical additives introduced into the plasma sheath of a re-entry vehicle and to deduce the optimum types and forms of additives to be used. An analytical investigation has shown that electron attachment to electrophylic molecules is one of the more important mechanisms in reducing the plasma free electron concentration and thereby in alleviating the re-entry sheath black-out problem. The attachment cross section data necessary for the theoretical selection of the more effective additives is not always available in the literature. An analysis is presented here, where attachment cross sections are correlated with more readily available fundamental thermodynamic data so that attachment data can be predicted. Qualitative reasoning based upon the potential energy diagram concept is employed to describe the physics of electron attachment and to derive graphical correlations between the more readily obtained thermodynamic values and the attachment cross-section parameters. Average attachment rate constants are also calculated for molecules from data in the literature. The attachment rate constant can be employed as a figure of merit to determine the most efficient additive, for the limiting case of negligible dissociation. The results show that carbon tetrachloride is the most efficient of the compounds investigated and is potentially at least two orders of magnitude better than water for moderate plasma temperatures.
- Plasma Physics and Magnetohydrodynamics
- Unmanned Spacecraft
- Radio Communications