GER Gradually Expanded Rotamak-Like Plasma Thruster

Project Number
NRF-OSTIn GER

Project Duration
August 2015 - November 2018

Status
In-Progress

Abstract
GER thruster is a “green” electric propulsion system which features a new way of generating potentially high thrust density. In GER, solid-state propellant is first converted into ultra-high density plasma (of ~1E20m-3) by our proprietary internal crossed unidirectional oscillating RF current sheets. An elongated Rotamak plasma will then be produced by a Rotating Magnetic Field (RMF) generated by feeding RF currents, de-phased by 90 degree through two pairs of orthogonal Helmholtz coils. The interaction of screening currents and the rotating field will produce a steady-state azimuthal plasma current (J), which is predominantly in the toroidal direction. The steady poloidal magnetic field, which is generated by the toroidal plasma current, will produce a magnetic field in the radial and axial direction (Br, Bz). The toroidal plasma current coupled with the unbalanced poloidal magnetic field in the gradually-expanded plasma will produce large net axial thrust (Fthr = Jtor X Bpol) to drive the nano-satellite. In GER, a proprietary real-time plasma diagnostics system will be integrated to provide robust propulsive attitude control, orbit raising, translation, and precision positioning to the satellite. The plasma density, temperature and scattering behavior are characterized and precisely controlled in real-time for achieving high plasma stability and precise thrust outputs. A magnetic nozzle, which features a convergent-divergent geometry, will be installed in the GER thruster to guide, expand, accelerate a plasma jet, and meanwhile to prevent wall-plasma contact (i.e. magnetic mirror effect). This will not only improve the robustness of specific impulse/thrust control but also enhance the lifetime of the thruster parts. In the last part of the project, we will reconfigure our pilot-scale high vacuum, large vessel (300 litre) into a space-environment simulator coupled with a ballistic pendulum system for GER’s field testing.

Funding Source
Mr Kelvin Tan

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