Magnetohydrodynamics (MHD) is the study of the flow of electrically conducting fluids in the presence of electromagnetic fields.  Some of the better-known applications of MHD accelerators are arc-jets and magnetoplasmadynamic thrusters [1].  Although the subject is not new, the flow control of electrically conductive fluids by MHD methods remains a topic of current research interest [2,3].  Periodically, MHD acceleration has been proposed to augment the propulsion system of a hypersonic vehicle and to improve the performance of ground test facilities [4].  However, these applications remain unrealized concepts.  A significan't factor in this present status is the lack of credible, quantitative, experimental evidence on MHD devices at relevant test conditions.  There are still unresolved issues regarding the mechanism by which conducting fluid is accelerated and about the effectiveness of the energy coupling.  Again, although the results are limted, studies have indicated that acceleration may be due more to ohmic heating by electrical discharge than to true electromagnetic and fluid dynamic coupling.  One detailed investigation of MHD for supersonic flow acceleration is currently underay [5].  This study is aimed at carefully characterization of the flow before and after the accelerator.  Owing to practical considerations, this study is being conducted in a short duration flow facility, which places limits on flow diagnostics.

 It is proposed herein to investigate MHD acceleration of subsonic plasma flows in a similar manner, and to thereby broaden the knowledge of MHD device operation in different flow regimes for possible future exploitation.  In contrast to the supersonic flow study, the present study is aimed at the investigation of MHD acceleration of a subsonic, highly ionized plasma flow, in which a greater array of experimental techniques can be used to characterize the thermochemical state of the plasma.