Electrodeless Plasma Thruster - Operating Principle

Operating Principle

1. Propellant is injected at the upstream side of the thruster body. In cases where the propellant used is not gaseous (e.g., alkali metals) at the local temperature, the propellant must be vaporized.
2. Gaseous propellant is ionized by one of the following methods:
   • bombarding the propellant with electrons emitted by a hot cathode or by an electron gun.
   • a steady state electrical discharge between two electrodes.
   • applying an alternating electric field either via a capacitive discharge or an inductive discharge or even a helicon discharge.
   • electromagnetic waves of various frequency from radio frequency up to gamma rays, which is especially useful for solid propellant in which case the propellant can be simultaneously vaporized and ionized by a laser impulse.
3. As the ionization stage is subjected to a steady magnetic field, the ionization process can leverage this situation by using one of the numerous resonances existing in magnetized plasma, such as ion cyclotron resonance (ICR), electron cyclotron resonance (ECR) or lower hybrid oscillation, to produce a high density cold plasma.
4. The cold and dense plasma, produced by the ionization stage, then drifts toward the acceleration stage by diffusion across a region of higher magnetic field intensity.
5. In the acceleration stage the propellant plasma is accelerated by magnetized ponderomotive force in an area where both non-uniform static magnetic fields and non-uniform high-frequency electromagnetic fields are applied simultaneously.