A concept for a plasma-core nuclear rocket is presented, which utilizes Lorentz forces to drive a vortex. The control of diffusion processes by the vortex isolates a zone of fuel from zones of propellant within the vortex. The primary propellant flows bypass the fuel in the axial direction, receiving heat by radiant transport. A parametric study of fuel containment conditions is presented for a simplified two-dimensional model, including radiant transport. The study indicates that laminar vortex flow would provide containment of a critical mass of fuel. The pressure level required to achieve criticality decreases with increasing cavity radius and tends to impose a requirement for radii exceeding 1 m. Electric power requirements for driving the vortex are modest compared to reactor power levels. Typical reactor power levels exceeding 50,000 Mw provide thrusts exceeding 1 X 106 Ib at a specific impulse of 2500 sec. HE gaseous-core nuclear rocket contains fissionable fuel and propellant, both in gaseous form, within a cavity surrounded by a reflector-moderator. Interest in gaseous-core reactors for rocket propulsion has been stimulated by the possibility of achieving a very high propellant exhaust temperature. The propellant temperature attainable in a solidcore nuclear rocket (of the NERVA type) is limited by the structural integrity and possible melting of solid fuel elements, and so the attainable specific impulse is of the order of 1000 sec or less. Since only about 10% of the energy produced by each fission will be deposited in the reflector-moderator of a gaseous-core reactor, propellant exhaust temperatures about 10 times higher than for a solid-core reactor should be possible. Thus, although the propellant exhaust temperature will be limited by nozzle cooling requirements, a specific impulse of 3000 sec is conceivable for a gaseous-core nuclear rocket. There are three basic problem areas for developing a gaseous-core reactor concept and demonstrating its feasibility. These are nuclear criticality, radiant heat transfer, and fuel containment. This paper is primarily concerned with the problem of fuel containment. This entails containment of a critical mass of fuel, retention of the fuel in the core for a sufficient time to be economical, and isolation of the hot fuel from solid boundaries. The application of vortex flows to achieve fuel contain