Electron beam-driven MHD for the RDHWT/MARIAH II hypersonic wind tunnel

The USAF Radiatively Driven Hypersonic Wind Tunnel (RDHWT)/Magnetohydrodynamic Accelerator Research Into Advanced Hypersonics (MARIAH II) Hypersonic Wind Tunnel Research Program is being conducted with the objective of developing enabling technologies and conceptual design criteria leading to a Medium-Scale Hypersonic Wind Tunnel (MSHWT) with a Mach 8-15 test capability. A true air test environment for Mach 8-12 flight conditions at a dynamic pressure of 2,000 Ibf/ft² (psf) is achieved using an ultra-high pressure (UHP) air supply system operating at a pressure of 2,300 MPa and temperature of 750 K. Thermal energy is added to a Mach 2 nozzle flow by an e-beam to achieve the desired flight enthalpy and entropy condition. Magnetohydrodynamic (MHD) augmentation is required to achieve the MSHWT operating point of testing behind the oblique shock of a 5-degree wedge, where the equivalent free stream conditions ahead of the shock would be Mach 15 at a dynamic pressure of 2,000 psf. A high performance MHD accelerator operating near atmospheric pressure is required to achieve this operating point. Nonequilibrium electrical conductivity is achieved in the MHD duct using an array of e-beams injected along the magnetic field lines, producing secondary ionization. This paper discusses the critical technical issues that must be addressed and the progress in the modeling and design of the e-beam seeded MHD accelerator. Concepts for e-beam windows into the sidewall of the MHD duct are also discussed. Engineering and design issues are addressed.