Feasibility study of a hybrid MHD/radiatively driven facility for hypersonic ground testing
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1997, by S.O. Macheret, R.B. Miles, and G.L. Nelson. Published by the American Institute of Aeronautics and Astronautics, Inc. A new concept is suggested for high Mach number, high dynamic pressure, long run time hypersonic wind tunnel. The concept includes an ultrahigh-pressure (UHP) driver, beamed energy addition to dense supersonic stream, and an MHD accelerator. The hybrid scheme is shown to benefit from the synergistic action of the components. The UHP driver and beamed energy sources add enthalpy and accelerate the flow at high density, relaxing requirements on the MHD accelerator and creating favorable conditions at the MHD channel entrance. On the other hand, MHD accelerator directly increases kinetic energy of the flow with little entropy change, and is capable of significantly extending the performance envelope (Mach number, dynamic pressure) compared with the pure beamed energy addition case. Two major versions of the hybrid facility are considered, corresponding to MHD operation at high and low pressures. In the first scenario, flow exiting the UHP driver will be directly passed into an MHD channel, where a rapid-fire sequence of bright arcs will be initiated by lasers or electron beams. The arcs will be sustained by linear electrodes on each side of the flow, accelerated in the presence of a magnetic field, and used to impart momentum to the bulk flow. The second scenario includes the UHP driver followed by the beamed energy addition and isentropic expansion to low pressure and temperature, at which point the flow will be passed into an MHD duct, where ionization is created by beams of energetic electrons. One-dimensional analysis and analytical estimates show that such a scheme could significantly augment the Mach number and dynamic pressure, or it could be used to substantially relax requirements on the UHP. Key technical issues to be resolved in the development of the hybrid concept are identified and briefly discussed.
