Past analyses of conventional MHD accelerator systems, which employ arc heaters in conjunction with alkali metal seeding of the air, have concluded that this approach to acceleration of air is not capable of reaching the high total enthalpy, low temperatures, and high dynamic pressures required to support advanced engine testingl'2>3. The very high temperatures required to ionize the seed material, coupled with known limits on the maximum operating pressures attainable in arc heaters, dictate that the final entropy of the test gas will exceed the targeted test section value, resulting in test section pressures or Mach numbers which are too low. This was the basic conclusion of the NASA-sponsored MARIAH study3. The present work describes the fist phase of a planned multi-year experimental effort to demonstrate an alternative mode of MHD accelerator operation which can potentially obviate these limitations. The concept is to exploit the ionizing power of electron beams to create a nonequilibrium ionization condition in the MHD channel, thus greatly increasing the electrical conductivity compared to its thermodynamic equilibrium (essentially zero) value. The advantage of this mode of operation is that the static temperatures can be kept relatively low through the MHD channel. The paper summa rizes themore » theoretical model for electron beam ionization in air, recently developed by Macheret et a12. Experiments conducted at San&a National Laboratories for the purpose of validating this model are also described. The fust phase of these experiments consist of measuring the bulk electrical conductivity of static air in a confined volume in the vicinity of an energetic electron beam. The experimental method is described, preliminary data is presented, and the results are interpreted in the light of the theoretical model.« less