Electrohydrodynamic thruster: Difference between revisions
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#REDIRECT [[Electrohydrodynamics]] |
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An '''[[electrohydrodynamic]] thruster''' is a high voltage device that propels air or fluids to achieve relative motion. '''EHD''' thrusters, unlike [[ion thruster]]s, do not carry their own propellant and thus cannot operate in space or vacuum. |
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== What is an EHD thruster == |
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An EHD thruster is a propulsion device based on ionic fluid propulsion which works without moving parts, using only electrical energy. The principle of ionic (air) propulsion with corona-generated charged particles has been known since the earliest days of the discovery of electricity, with references dating back to year 1709 in a book titled ''Physico-Mechanical Experiments on Various Subjects'' by [[Francis Hauksbee]]. The first publicly demonstrated tethered model was developed by Major De Seversky in the form of an [[Ionocraft]], a single stage EHD thruster, in which the thruster lifts itself by propelling air downwards (see [[Newton's laws of motion|Newton's Third Law of Motion]]). De Seversky contributed much to its basic physics and its construction variations during the year 1960 and has in fact patented his device ({{US patent|3130945}}, April 28, 1964). Only electric fields are used in this propulsion method. |
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The basic components of an EHD thruster are two: an [[air ioniser|ioniser]] and an [[ion accelerator]]. [[Ionocraft]]s form part of this category, but their energy conversion efficiency is severely limited to less than 1% by the fact that the ioniser and accelerating mechanisms are not independent. Unlike the [[ionocraft]], within an EHD thruster, the air gap in its second stage is not restricted or related to the [[Corona discharge]] voltage of its ionising stage. Also, EHD thrusters are not restricted to air as their main propulsion fluid, and work perfectly in other fluids, such as oil{{Cn|date=November 2011}}. |
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== EHD thruster operation == |
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The first stage consists of a powerful [[air ioniser]] which, when supplied by high [[voltage]] in the kilovolt to megavolt range, ionises the intake air into ion clouds which flow into the second stage of the device. |
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The second stage consists of one or multiple stages of ion accelerators, powered by voltages in the kilovolt or megavolt range, in which the ionised fluid is moved on a straight path along the length of the accelerating unit. Movement of the ion clouds can be electronically controlled to increase the effective efficiency. Within this path, the ions travel at a constant [[drift velocity]] and multiple impacts occur with the neutral fluid molecules present in the accelerating unit, which is open to the surrounding fluid. In accordance with [[Newton's Third Law]] of motion, the thruster will be acted upon by an equal and opposite force to the total [[force]] exerted by the ions over the neutral fluid within the second stage. |
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Optionally, the temperature, pressure and fluid constituents may be synthesised within the accelerating stage to increase the efficiency of [[momentum]] transfer between the charged ions and the neutral fluid molecules. The charged ions are then neutralised on their exit from the second stage. The electrical to mechanical conversion efficiency is equal to the ratio of the velocity of the neutral fluid to that of the moving ions. In a single stage [[ionocraft]] type EHD thruster, this ratio is typically equal to 1 m/s:100 m/s or 1%. |
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==See also== |
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*[[Field Emission Electric Propulsion]] |
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*[[Hall effect thruster]] |
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*[[Ion wind]] |
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*[[Ion thruster]] |
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*[[List of plasma (physics) applications articles]] |
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*[[Magnetohydrodynamic drive]] |
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*[[Magnetoplasmadynamic thruster]] |
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*[[Pulsed inductive thruster]] |
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*[[Spacecraft propulsion]] |
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==External links== |
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*[http://blazelabs.com/l-intro.asp Blaze Labs Research — Introduction to EHD thrusters] |
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*[http://www.iop.org/EJ/abstract/0022-3727/19/9/011 Effect of neutral fluid velocity on EHD efficiency — Journal of Physics (abstract)] |
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*[http://www.edpsciences.org/articles/epjap/abs/2003/04/ap02008/ap02008.html Electric wind characterisation in negative point-to-plane corona discharges in air (abstract)] |
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*[http://www.rmcybernetics.com/science/propulsion/ehdt.htm Make your Own Electrohydrodynamic Thruster] |
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*[http://www.aip.org/tip/INPHFA/vol-6/iss-5/p16.pdf Plasma propulsion in space] |
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[[Category:Plasma physics]] |
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[[Category:Spacecraft propulsion]] |
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[[fr:Propulseur électrohydrodynamique]] |
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Revision as of 23:10, 12 December 2011
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