PRECURSOR AND OTHER EFFECTS IN THE ELECTRICALLY DRIVEN SHOCK TUBE.
Flight Sciences Lab. rept.
BOEING SCIENTIFIC RESEARCH LABS SEATTLE WASH
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This report was concerned with the nature, cause and magnitude of some of the precursor effects and the separation of the shock from the hot gas associated with the discharge in the 6-inch electromagnetically driven shock tube. The fact that the shock tube is 4 m long allows one to study the propagation of the shock wave after the discharge has terminated. The large diameter makes the tube wall effects less important. It was found that the main precursor effect was caused by vacuum ultraviolet radiation. Impurities in the gas were probably ionized. It should be noted that near the discharge, a very large percentage of these impurities will be ionized. If the impurity level is not very low, it is quite possible to increase the enthalpy of the gas ahead of the shock significantly through ionization of the impurities. For instance, if the average energy absorbed per impurity molecule were 20 ev and the impurity concentration were 0.1 mole percent, the absorption of this much energy would correspond to an increase in temperature of about 150 K. Any calculations based on the Rankine-Hugoniot relations would have to take this fact into account.