AsianScientist (May 19, 2015) – A team led by Dr. Kazunori Takahashi and Professor Akira Ando from Tohoku University’s Department of Electrical Engineering have designed an electrodeless, helicon plasma thruster. A detailed description of the workings of the device has been published in Physical Review Letters.
To date, electric propulsion devices have been the key technology for space exploration. Such devices use charged particles produced by electric discharge which are accelerated via eletromagnetic fields. The thrust force which propels the spacecraft is equivalent to the momentum exhausted by the device.
Mature electric propulsion devices such as ion engines, hall thrusters and magnetoplasmadynamic thrusters have electrodes exposed to the plasmas. Ion sputtering and erosion damage these exposed electrodes over time. For propulsion systems that are used over a long period, electrodeless propulsion devices have been suggested and rigorously researched as an alternative option. These are represented by the Variable Specific Impulse Magneto-plasma Rocket (VASIMR) and the helicon plasma thruster.
In the helicon plasma thruster concept, the charged particles in a high density helicon plasma source are guided to the open source exit and accelerated by the magnetic nozzle via a magnetic expansion process. Various gain and loss processes of the particle momentum occur in the thruster, significantly affecting the propulsive performance, where the thrust force is equivalent to the momentum exhausted from the system.
The major momentum loss is thought to occur at the source lateral wall, where the radial momentum is transferred to the wall via an electrostatic ion acceleration in the plasma sheath. In contrast, the loss of the axial momentum has been treated as negligible. However, data from the present experiments clearly show the presence of the axial momentum lost to the lateral wall, which is transferred by the radially lost ions.
This significant axial momentum loss seems to have originated from the internal axial electric field in the plasma core, which appears to be enhanced by the highly ionized plasmas for the future high power operation of the helicon plasma thruster. More detailed understanding of the plasma dynamics will hopefully lead to further development of the advanced high power and electrodeless electric propulsion device.
The article can be found at: Takahashi et al. (2015) Axial Momentum Lost to a Lateral Wall of a Helicon Plasma Source.
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Source: Tohoku University.
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