Electrodeless plasma thruster

The electrodeless plasma thruster is a spacecraft propulsion engine. It was created by Mr. Gregory Emsellem based on technology developed by French Atomic Energy Commission scientist Dr Richard Geller and Dr. Terenzio Consoli, for high speed plasma beam production.

The electrodeless plasma thruster is currently being developed and adapted to various spacecraft propulsion needs by [http://www.elwingcorp.com The Elwing Company] .

Operating principle

# 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.
# Gaseous propellant is ionized by one of the following methods. By bombarding the propellant with electrons emitted by a hot cathode or by an electron gun. Another possible method can be to use a steady state discharge between two electrodes. Ionization can also be performed by applying an alternating electric field either via a capacitive discharge or an inductive discharge or even a helicon discharge. Propellant can also be ionized by electromagnetics 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. 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.
# 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.
# 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.

Advantages

This thruster technology can deliver large thrust density as the acceleration process is not limited by plasma density through Hall Parameter or grid electrical screening. Further as the ponderomotive force accelerate all plasma species in the same direction, this thruster technology does not need any neutralizer. The fact that electrodeless plasma thruster is inherently multi-staged allows it to optimize both stages independently, or to throttle the thruster at constant power between higher specific impulse and higher thrust. The field of ponderomotive force is created by non-uniform high frequency field and static magnetic field, thus it implies no grids or contact between the plasma and any electrodes hence it avoids most thruster erosion and spacecraft contamination issues.

Applications

Propulsion systems based on electrodeless plasma thrusters seem ideally suited for orbit raising for large geostationnary satellites, and would also be able to perform station keeping, hence enabling important propellant mass savings. The ability of this technology to provide large thrust density also allows faster missions to the outer planets.

Other research

The use of ponderomotive force to accelerate a plasma has recently been investigated from a theoretical point of view by Princeton Plasma Physics Laboratory scientists I. Y. Dodin, Y. Raitses and N. J. Fisch.

Some theoretical research has also been reported around the debated issue of the existence of a double layer in such a thruster, even if such a double layer structure would be current-free, as both ions and electrons travel in the same direction at the same average terminal speed. The existence of current free double layer is still debated among plasma physicists.

See also

* Spacecraft propulsion
* Magnetic sail
* Hall effect thruster
* VASIMR
* Magnetoplasmadynamic thruster
* Field Emission Electric Propulsion
* Helicon Double Layer Thruster
* Ion thruster
* Pulsed inductive thruster

External links

* [http://pdf.aiaa.org/preview/CDReadyMJPC2005_1177/PV2005_3855.pdf AIAA paper on this technology]
* [http://www.elwingcorp.com/extras2.html List of articles, presentations and patents by the Elwing Company on this technology]
* [http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=20619178 Princeton Plasma Physics lab publications]