Electrodeless plasma thruster
Encyclopedia
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 electrode
less plasma
thruster is currently being developed and adapted to various spacecraft propulsion needs by The Elwing Company.
and higher thrust
. 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.
, hence enabling important propellant mass savings. The ability of this technology to provide large thrust density also allows faster missions to the outer planets.
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.
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
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 electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
less plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
thruster is currently being developed and adapted to various spacecraft propulsion needs by The Elwing Company.
Operating principle
- PropellantPropellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
is injected at the upstream side of the thruster body. In cases where the propellant used is not gaseous (e.g. alkali metalAlkali metalThe alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
s) at the local temperature, the propellant must be vaporized. - Gaseous propellant is ionized by one of the following methods:
-
- bombarding the propellant with electronElectronThe electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s emitted by a hot cathodeHot cathodeIn vacuum tubes, a hot cathode is a cathode electrode which emits electrons due to thermionic emission. In the accelerator community, these are referred to as thermionic cathodes. The heating element is usually an electrical filament...
or by an electron gunElectron gunAn electron gun is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in television sets and computer displays which use cathode ray tube technology, as well as in other instruments, such as electron microscopes and particle...
. - a steady state electrical discharge between two electrodes.
- applying an alternating electric field either via a capacitive dischargeCapacitively coupled plasmaA capacitively coupled plasma is one of the most common types of industrial plasma sources. It essentially consists of two metal electrodes separated by a small distance, placed in a reactor. The gas pressure in the reactor can be lower than atmosphere or it can be atmospheric.A typical CCP system...
or an inductive dischargeInductively coupled plasmaAn inductively coupled plasma is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.-Operation:...
or even a helicon discharge. - electromagnetic waves of various frequency from radio frequencyRadio frequencyRadio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
up to gamma rayGamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s, which is especially useful for solid propellant in which case the propellant can be simultaneously vaporized and ionized by a laserLaserA laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
impulse.
- bombarding the propellant with electron
-
- As the ionization stage is subjected to a steady magnetic fieldMagnetic fieldA magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
, the ionization process can leverage this situation by using one of the numerous resonances existing in magnetized plasma, such as ion cyclotron resonanceIon cyclotron resonanceIon 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 transform ion cyclotron resonance mass spectrometers...
(ICR) , electron cyclotron resonanceElectron cyclotron resonanceElectron cyclotron resonance is a phenomenon observed both in plasma physics and condensed matter physics. An electron in a static and uniform magnetic field will move in a circle due to the Lorentz force...
(ECR) or lower hybrid oscillationLower hybrid oscillationA 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...
, 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 impulseSpecific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
and higher thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
. 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 satellites, and would also be able to perform orbital stationkeepingOrbital stationkeeping
In astrodynamics orbital station-keeping is a term used to describe the orbital maneuvers made by thruster burns that are needed to keep a spacecraft in a particular assigned orbit.For many Earth satellites the effects of the non-Keplerian forces, i.e...
, 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 LaboratoryPrinceton Plasma Physics Laboratory
Princeton Plasma Physics Laboratory is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science located on Princeton University's Forrestal Campus in Plainsboro Township, New Jersey. Its primary mission is research into and development of fusion as an...
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
Double layer (plasma)
A double layer is a structure in a plasma and consists of two parallel layers with opposite electrical charge. The sheets of charge cause a strong electric field and a correspondingly sharp change in voltage across the double layer. Ions and electrons which enter the double layer are accelerated,...
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
- Electrodeless plasma excitation
- List of plasma (physics) applications articles