Abstract: An electric propulsion system comprising a plasma chamber having first and second apertures for producing ion beams. Respective first and second coils are arranged about the chamber to produce an electromagnetic field in regions adjacent to the apertures, and are driven differentially by a radio frequency (RF) drive module. By driving the coils differentially, the electric field in the region of the two apertures can be differentially controlled, and a variation of output thrusts at the two apertures is possible. In this way a net thrust can be produced, which net thrust is varied by controlling the drive to the two coils.

Abstract: An electric propulsion system comprising a plasma chamber having first and second apertures for producing ion beams. Respective first and second coils are arranged about the chamber to produce an electromagnetic field in regions adjacent to the apertures, and are driven differentially by a radio frequency (RF) drive module. By driving the coils differentially, the electric field in the region of the two apertures can be differentially controlled, and a variation of output thrusts at the two apertures is possible. In this way a net thrust can be produced, which net thrust is varied by controlling the drive to the two coils.

Abstract: An electric propulsion system including a plasma chamber having a first output aperture having first acceleration and screen grids, and a second output aperture having second acceleration and screen grids. The screen grids are maintained at a constant positive potential. In use, ions are expelled from the two apertures in anti-parallel directions. By independently controlling the potentials of the acceleration grids to adjust the rates of ion extraction from the output apertures, small resultant thrusts at the ?N level may be obtained and the resultant thrust maybe continuously reduced to zero. By closing off apertures of one of the screen grids, thrust at the mN may be obtained with sub-?N accuracy. The system therefore provides functionality previously achievable only with plural types of electric propulsion system, providing weight and complexity savings for satellites or space-probes comprising such systems.