Design of a fusion propulsion system - Part 2: Numerical simulation of magnetic-nozzle flows

Numerical simulations of magnetic-nozzle flows have been successfully conducted in the interest of providing valuable insights and detailed design guidance to near-future experimental efforts. Quasi-steady modeling using helium propellant with classical resistivity demonstrates a nearly isentropic expansion of the confined gas to exhaust speeds that exceed 270 km/s. For a stagnation temperature of 100 eV, approximately 70% of the thermal power is converted to thrust power (0.4 GW), producing 4.6 kN of thrust. Further expansion can lead to additional gains in thrust by utilizing the thermal power that is retained in the 20-eV plasma at the exit. In the inlet of the nozzle, near the plasma field interface, the development of nonuniformities in the magnetic field is exposed. For T₀ = 100 eV as much as 50% of the mass flux is found to penetrate the current layer across the magnetic field lines. At fixed plasma pressure and applied field the layer at the throat increases in thickness from approximately 3 to 5 cm when the stagnation temperature is decreased from 250 to 100 eV.