Three-dimensional modeling of magnetic nozzle processes

Simulations of plasma flow through a magnetic nozzle were conducted using the time-dependent, threedimensional magnetohydrodynamics code MACH3. Modeling of magnetic nozzle flow using constant, classical isotropic, and classical tensor resistivity provides preliminary quantitative depiction of the core-plasma flow, evolution of the magnetic field, and conversion of stagnation enthalpy to directed exhaust thrust energy, and serves as verification for the numerical model. For stagnation conditions of 100 eV and 0.355 MPa, steady-state modeling using helium propellant demonstrates a nearly isentropic expansion through the nozzle to exhaust speeds near 160 km=s. The extent of the contribution from the magnetic diffusion and the mass-flux penetration to the thickness of the current layer strongly depends on plasma resistivity. Plasma-field interaction results in a reduction of approximately 50% of the directed axial thrust when compared with a solid-wall nozzle of equivalent Mach number design. At fixed plasma pressure and applied field the exhaust velocity scales appropriately as the square root of the stagnation temperature.