The electrodeless plasma thruster is a spacecraft propulsion engine commercialized under the acronym "E-IMPAcT" for "Electrodeless-Ionization Magnetized Ponderomotive Acceleration Thruster". 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

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

less plasma thruster is currently being developed and adapted to various spacecraft propulsion needs b
The Elwing Company
The Elwing Company was founded in 2002 by Gregory Emsellem.

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: #* bombarding the propellant with

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

s emitted by a

hot cathode In vacuum tubes and gas-filled tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission. This is in contrast to a cold cathode, which does not have a heating elemen ...

or by an

electron gun An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly ...

. #* a steady state

electrical discharge An electric discharge is the release and transmission of electricity in an applied electric field through a medium such as a gas (ie., an outgoing flow of electric current through a non-metal medium).American Geophysical Union, National Research ...

between two electrodes. #* applying an alternating electric field either via a capacitive discharge or an inductive discharge or even a

helicon discharge In electromagnetism, a helicon is a low-frequency electromagnetic wave that can exist in bounded plasmas in the presence of a magnetic field. The first helicons observed were atmospheric whistlers, but they also exist in solid conductorsBowers, ...

. #*

electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...

s of various frequency from

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...

up to

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s, which is especially useful for solid propellant in which case the propellant can be simultaneously vaporized and ionized by a

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...

impulse. #As the ionization stage is subjected to a steady magnetic field, the ionization process can use one of the numerous resonances existing in magnetized plasma, such as

ion cyclotron resonance Ion cyclotron resonance is a phenomenon related to the movement of ions in a magnetic field. It is used for accelerating ions in a cyclotron, and for measuring the masses of an ionized analyte in mass spectrometry, particularly with Fourier transfo ...

(ICR),

electron cyclotron resonance Electron cyclotron resonance (ECR) is a phenomenon observed in plasma physics, condensed matter physics, and accelerator physics. It happens when the frequency of incident radiation coincides with the natural frequency of rotation of electrons in m ...

(ECR) or

lower hybrid oscillation In plasma physics, a lower hybrid oscillation is a longitudinal oscillation of ions and electrons in a magnetized plasma. The direction of propagation must be very nearly perpendicular to the stationary magnetic field, within about radians. Othe ...

, to produce a high density

cold plasma A nonthermal plasma, cold plasma or non-equilibrium plasma is a plasma which is not in thermodynamic equilibrium, because the electron temperature is much hotter than the temperature of heavy species (ions and neutrals). As only electrons are ther ...

. # 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 physics, a ponderomotive force is a nonlinear force that a charged particle experiences in an inhomogeneous oscillating electromagnetic field. It causes the particle to move towards the area of the weaker field strength, rather than oscilla ...

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 In architecture, a hall is a relatively large space enclosed by a roof and walls. In the Iron Age and early Middle Ages in northern Europe, a mead hall was where a lord and his retainers ate and also slept. Later in the Middle Ages, the grea ...

or grid electrical screening. Further, as the ponderomotive force accelerates 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 Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...

and higher

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that sys ...

. The field of ponderomotive force is created by a non-uniform high frequency field and static magnetic field, thus it implies no grids nor 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

geostationary satellite A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitude ...

s, and would also be able to perform

orbital stationkeeping In astrodynamics, orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft or celestial body. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its ...

, 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 on the same phenomenon

The use of

to accelerate a plasma has recently been investigated from a theoretical point of view by

Princeton Plasma Physics Laboratory Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. Its primary mission is research into and development of fusion as an energy source. It is known ...

scientists I. Y. Dodin, Y. Raitses and N. J. Fisch. Princeton Plasma Physics Laboratory publications http://htx.pppl.gov/publications.html 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.

References

External links

AIAA paper on this technology

{{spacecraft propulsion Ion engines Spacecraft components