Interaction of Electromagnetic Waves With Plasmas of Hypersonic Flows

Problems involving the interaction of electromagnetic waves with the plasma sheath surrounding a hypervelocity vehicle lead to new and challenging areas of research. Communication blackout'' and the tasks of locating reentering ICBM warheads and of discriminating such warheads from decoys by microwave methods are examples of important problems of this type. It is shown that, due to the complexity of the aerodynamic, chemical kinetic, and electrodynamic phenomena, useful small-scale experiments are not possible for many problems of interest. A new hypersonic shock tunnel with a test section 6 ft in diameter has been built. The capabilities of this tunnel for the study of problems involving the interaction of electromagnetic waves and hypersonic plasmas are discussed and some recent experimental results reported. The communication blackout problem for a lifting hypersonic vehicle, such as the Dynasoar, is considered as a problem to be studied in this shock tunnel. It is shown that two useful approaches can be followed, one leading to the gathering of test data for various configurations, and the other leading to the assessment of the validity of various schemes for the amelioration of the problem.