Gas Core Reactor Rocket - Magnetic Confinement

Magnetic Confinement

Barring an external force, hydrodynamic containment is the only way to increase the residence time of the fuel in the reactor. However, one may ask why bar an outside force, could not magnetic confinement be used since the fuel would be highly ionized (three or four times ionized) while the propellant is only partially ionized? To answer this question one must understand a little about magnetic plasma confinement. The key parameter of interest for magnetic confinement is the ratio of kinetic pressure to magnetic pressure, β.

When β<1 magnetic confinement is possible (most fusion schemes have a β close to 0.05). However, the pressures in a gas core rocket are much higher than pressures in fusion devices, approximately 1000 atm (100 MPa). For these pressures, the necessary magnetic field strength required is close to 16 teslas just to produce β=1. For a magnetic field of this magnitude, superconducting technology is necessary and the added mass of such a system would be detrimental. Also, even with a β<1, resistive diffusion will cause the fuel core to collapse almost immediately unless β<<1, which would require an even larger magnetic field.