Magnetic nozzle

The conversion of high-energy charged particles into thrust depends on the design of the magnetic nozzle. The aim of this study is to critically review current, proposed schemes in order to identify reasonable values for conversion efficiency and point out possible problems in magnetic nozzle design.

B.4.2 Specific design studies Colliding beam fusion reactor

The use of an FRC as a background neutralizer for non-thermal schemes that produce fusion power by beam-beam reactions (CBFR) has also been proposed for fusion propulsion [Cheung et al., 2004]. There is a need to perform a parameter optimization for space propulsion, by critically reviewing conventional plasma dynamics assumptions as well.

Spherical tokamak

The spherical tokamak is a closed configuration and the extraction (for direct thrust) of high-energy particles from the reaction chamber and the toroidal magnet is not trivial, although probably less difficult than in conventional tokamaks equipped with heavy magnets producing the toroidal magnetic field. Nevertheless, the existing medium-scale experiments have already shown the significant potential of spherical tokamaks for energy production. Specific design studies (see [Williams et al., 1998]) exist for space propulsion systems based on spherical tokamaks although the issue of particle extraction is not addressed in detail. Divertor configurations capable of extracting particles from the reaction chamber, possibly looking at very-low-aspect-ratio (R/ a < 1.5) equilibria, should be investigated.

Levitated dipole coils

As discussed in Section B.3.5, the levitated dipole coil must comply with the following requirements: high surface radiation (e.g., by high surface temperature), good neutron shielding of the superconducting magnet, efficient energy conversion of incoming heat into electricity for system refrigeration and low total mass. The present design is only conceptual and a further assessment could set a limit on coil mass (and therefore on foreseeable specific power).

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