Electrohydrodynamic (EHD) drive

Grey Havoc

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One of the people responsible for that demonstration co-authored a paper in 2013. It is available here:

http://rspa.royalsocietypublishing.org/content/469/2154/20120623

Need to improve efficiency in terms of power in to thrust out and thrust per volume. But it was a much more convincing demonstration that the tinfoil triangles floating around YouTube. It takes a lot of power though. Interested to know how they plan on generating that power on an aircraft.
 
Yes, if you were carrying around a mini reactor, then you could have an aircraft of unusual shape and behaviour that might be practical......
 
I just started a thread on EHD drive, with this link.

Is this the same?

(Sorry, I didn't find this threat with search before.)
 
 
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The basic principle is simple enough: ionise air with a high voltage and attract the ions backwards with a second electrode place further back. The ions then bump into more air, drawing it along with them a bit like the Dyson air blade idea. Throwing this wake backwards creates forward thrust.
But efficiency is poor and the MIT model had to be so light that it had no flight control system.

The aircraft designer Seversky built a more controllable flying model around 1960. However it had to be tethered to a heavy off-board high-voltage power supply. There was an informative article published in Popular mechanics: "Major de Seversky's Ion-Propelled Aircraft", Popular mechanics, Vol. 122, No. 2, August 1962, pp.58-61, 196. https://books.google.co.uk/books?id=ROMDAAAAMBAJ&pg=PA58

I remember that the odd science fiction story picked up on the idea.

However its development has been hampered by several problems. Besides low efficiency, there is also a need for electrical safety. As significant, I would suggest, was a tendency in the past to focus on VTOL performance, in the form that is nowadays termed "powered lift", as it requires an order of magnitude more efficiency in thrust generation than conventional aerodynamic flight. Seversky's model being a case in point.

You can waste a lot of power turning a high-voltage electrical current into an air current and most research goes into trying to improve conversion efficiency through variations in electrode geometry. Also, the larger the volume of air you move, the slower you need to move it and the higher your efficiency (hence the huge fans on jet airliners). So a whole-wing EHD system is attractive. But rain stops play. It draws the charge out of the air, falls away with it, and the thrust dies. So any practical design must be enclosed in a water-shedding duct, perhaps like the dust-filtering vortex intakes fitted to helicopters in the desert. And that makes a whole-span installation next to impossible to engineer.

Another big problem with a practical system is corrosion. Ions are corrosive beasts. In a previous life I built power supplies for them to them to etch away silicon chips. However on an EHD drive they eat away at one or both of the electrodes instead. The more you crank up the power to useful levels, the faster your electrodes corrode. This was the problem that sounded the death knell of the electromagnetic rail gun.

Unless they can increase both conversion efficiency and power density by an order of magnitude, the idea can never really take off.
 
There is another thread about electrohydrodynamic drive:
Mods: merge?
 
One of the people responsible for that demonstration co-authored a paper in 2013. It is available here:

http://rspa.royalsocietypublishing.org/content/469/2154/20120623

Need to improve efficiency in terms of power in to thrust out and thrust per volume. But it was a much more convincing demonstration that the tinfoil triangles floating around YouTube. It takes a lot of power though. Interested to know how they plan on generating that power on an aircraft.
Hello, hole in the ground, I'm unable to open this doc, do you have it in a different format or other. Thnx. Kevin
 
One of the people responsible for that demonstration co-authored a paper in 2013. It is available here:

http://rspa.royalsocietypublishing.org/content/469/2154/20120623

Need to improve efficiency in terms of power in to thrust out and thrust per volume. But it was a much more convincing demonstration that the tinfoil triangles floating around YouTube. It takes a lot of power though. Interested to know how they plan on generating that power on an aircraft.
Hello, hole in the ground, I'm unable to open this doc, do you have it in a different format or other. Thnx. Kevin

Web page version of the full paper, courtesy of the Wayback Machine:
https://web.archive.org/web/2014123...cietypublishing.org/content/469/2154/20120623
 
The Japanese builded a small ship (Jamato-1 ) with a marine version of that propulsion the ship looked fast, had powerfull Diesel generators and drove 15 km/h...
 
The Japanese builded a small ship (Jamato-1 ) with a marine version of that propulsion the ship looked fast, had powerfull Diesel generators and drove 15 km/h...
Am wondering if the terms EHD and MHD are intended to mean the same thing, or? As to the Japanese ship, I understood that to be an example of Magnetohydrodynamics where the term Electrohydrodynamic is something different. I know thr ship worked cuz ocean (salt) water is conductive. Now I have to study this.
If being strict with semantics, "hydro" shouldn't be used at all. One might see "fluid" popping up in the literature soon MFD or EFD
 
Am wondering if the terms EHD and MHD are intended to mean the same thing, or? As to the Japanese ship, I understood that to be an example of Magnetohydrodynamics where the term Electrohydrodynamic is something different. I know thr ship worked cuz ocean (salt) water is conductive. Now I have to study this.
If being strict with semantics, "hydro" shouldn't be used at all. One might see "fluid" popping up in the literature soon MFD or EFD
Magnetohydrodynamics is the interaction of magnetic fields with electrically charged (ionised) fluids. Electrohydrodynamics is the interaction of electric fields with those same fluids.
The "hydro" term got used because early studies involved solutions in water. The general fields are more accurately referred to as magneto- (or electro- as appropriate) fluid dynamics, but only pedants bother with that.
One practical difference between them is that magnetic fields only interact with moving flows (currents) of charged particles, while electric fields act directly on the charged particles regardless of relative velocity. Both phenomena can be used to generate thrust by pushing the fluid out the back, but their engineering is very different. Broadly speaking, the strong magnetic fields used in MHD are generated by large electric currents, while the strong electric fields used in EHD are generated by large voltages. After that, things get deeply technical.
The EHD drive, the subject of this thread, is all about maintaining and applying those voltages to generate thrust.
Hope this helps.
 
In both cases you need ions, those are much easier to produce in salt water instead air (by ionizing), but the physics of propulsion are quite the same. I don"t no each and each and every variant but in my understanding, in both cases you make the ions move by an electric fiels and use the lorenz forces by a magnitic fiels for propulsion.
 
In both cases you need ions, those are much easier to produce in salt water instead air (by ionizing), but the physics of propulsion are quite the same. I don"t no each and each and every variant but in my understanding, in both cases you make the ions move by an electric fiels and use the lorenz forces by a magnitic fiels for propulsion.
Yikes, had to copy this out of the text. I've been working with gasses that are aready ionized, so creation of a/the magnetic field is what I think I understand. Here's the text:
"Fluid flow influenced by electric and magnetic fields has classically been divided into two separate, simplified categories: electro-hydrodynamics (EHD) studying flows under the influence of an electric field with free electric charges and no magnetic field, and magneto-hydrodynamics (MHD) studying flows under the influence of a magnetic field and no free electric charges or electric fields. This division was necessary to reduce the extreme complexity of the coupled system of Navier-Stokes, Maxwell's and constitutive equations describing combined electro-magneto-hydrodynamic (EMFD) flows [G. S. Dulikravich and S. R. Lynn, Unified electro-magneto-fluid dynamics (EMFD): introductory concepts. Int. J. Non-Linear Mechanics 32, 913–922 (1997)]. In this paper, the unified EMFD theory is compared with classical EHD and MHD models. This reveals the inconsistencies and shortcomings of classical formulations and allows discussion of the relative importance of terms describing the electro-magnetic force, electric current and heat transfer."
 
In both cases you need ions, those are much easier to produce in salt water instead air (by ionizing), but the physics of propulsion are quite the same. I don"t no each and each and every variant but in my understanding, in both cases you make the ions move by an electric fiels and use the lorenz forces by a magnitic fiels for propulsion.
Yikes, had to copy this out of the text. I've been working with gasses that are aready ionized, so creation of a/the magnetic field is what I think I understand. Here's the text:
"Fluid flow influenced by electric and magnetic fields has classically been divided into two separate, simplified categories: electro-hydrodynamics (EHD) studying flows under the influence of an electric field with free electric charges and no magnetic field, and magneto-hydrodynamics (MHD) studying flows under the influence of a magnetic field and no free electric charges or electric fields. This division was necessary to reduce the extreme complexity of the coupled system of Navier-Stokes, Maxwell's and constitutive equations describing combined electro-magneto-hydrodynamic (EMFD) flows [G. S. Dulikravich and S. R. Lynn, Unified electro-magneto-fluid dynamics (EMFD): introductory concepts. Int. J. Non-Linear Mechanics 32, 913–922 (1997)]. In this paper, the unified EMFD theory is compared with classical EHD and MHD models. This reveals the inconsistencies and shortcomings of classical formulations and allows discussion of the relative importance of terms describing the electro-magnetic force, electric current and heat transfer."
Nicknick and steelpillow, did you read what it posted recently of super fast solar wind sailing? Did I get it right? ....explaining it. Kevin
 
In both cases you need ions, those are much easier to produce in salt water instead air (by ionizing), but the physics of propulsion are quite the same. I don"t no each and each and every variant but in my understanding, in both cases you make the ions move by an electric fiels and use the lorenz forces by a magnitic fiels for propulsion.
Yikes, had to copy this out of the text. I've been working with gasses that are aready ionized, so creation of a/the magnetic field is what I think I understand. Here's the text:
"Fluid flow influenced by electric and magnetic fields has classically been divided into two separate, simplified categories: electro-hydrodynamics (EHD) studying flows under the influence of an electric field with free electric charges and no magnetic field, and magneto-hydrodynamics (MHD) studying flows under the influence of a magnetic field and no free electric charges or electric fields. This division was necessary to reduce the extreme complexity of the coupled system of Navier-Stokes, Maxwell's and constitutive equations describing combined electro-magneto-hydrodynamic (EMFD) flows [G. S. Dulikravich and S. R. Lynn, Unified electro-magneto-fluid dynamics (EMFD): introductory concepts. Int. J. Non-Linear Mechanics 32, 913–922 (1997)]. In this paper, the unified EMFD theory is compared with classical EHD and MHD models. This reveals the inconsistencies and shortcomings of classical formulations and allows discussion of the relative importance of terms describing the electro-magnetic force, electric current and heat transfer."
Nicknick and steelpillow, did you read what it posted recently of super fast solar wind sailing? Did I get it right? ....explaining it. Kevin
no, I"m going to bed.... (can be deleted...)
 
Just as a little warning/tip to anyone interested in the whole ionic propulsion topic, watch your sources really closely when researching this stuff. There's a whole...mythos about it that goes around in the UFO community, if you see the term "Biefield-Brown effect" you can probably discount whatever that source is saying. Otherwise you're likely to end up down a rabbit hole of antigravity, Nazi flying saucers, TR-3Bs and the whole "secret space program" shtick that's appeared over the past few years (not to be confused with actual classified space projects, I'm talking Mars bases and Dark Fleet Nazi-Reptillian alliances here).
 
Just as a little warning/tip to anyone interested in the whole ionic propulsion topic, watch your sources really closely when researching this stuff. There's a whole...mythos about it that goes around in the UFO community, if you see the term "Biefield-Brown effect" you can probably discount whatever that source is saying. Otherwise you're likely to end up down a rabbit hole of antigravity, Nazi flying saucers, TR-3Bs and the whole "secret space program" shtick that's appeared over the past few years (not to be confused with actual classified space projects, I'm talking Mars bases and Dark Fleet Nazi-Reptillian alliances here).
Yep! Lorentz and/or Laplace force real, Biefield-Brown not so much.
 
To night, my brain worked during sleep and my good old book from my teen years came into my mind (https://www.amazon.de/Wie-funktioniert-das-Technik-Leben/dp/3411017325 written by real engineers for those who will become engineers...). I remember, there was an Ion drive rocket, which worked basically as a EHD (without magnets).

It’s no big deal being wrong and I’m not going to invent stories about mystic lawn mowers..
 
Woo alert: There's a new spate of EM Space-Drive woo washing through, as the 'Usual Media' have mega-hyped an obscure Chinese announcement of a 'better' toroidal ion drive, and the 'Usual Suspects' have broken out the champagne, yet again, yet again...

Beyond the obvious Newtonian / Einsteinian issues, I've been unable to find a reliable 'primary source', or even a woo-minimal one for this announcement, so 'Due Care', please ??

FWIW, the 'ion flyer' ? Some years back, our local library had a book by a guy who'd built a series of such. A cross between pico-light aero-modelling, 'kitchen foil' origami and scary DIY EHT PSUs that made me warily 'suck my teeth', those tethered things actually hovered and flew in 'still, dry air'.
When I tried to borrow the book a second time, it had been 'withdrawn' on safety grounds: PSUs non-compliant with 'British Standards'...

( IMHO, his hacked PSUs were no more dangerous than a mid-sized Tesla Coil, but even they are prone to biting users, spamming RF spectrum and, um, 'Spontaneous Combustion'... )

IIRC, even such 'toy' ion-flyers spawned a woo-storm of speculation about 'Black Triangle' aero-space craft with EHT aerospikes...
 
Woo alert: There's a new spate of EM Space-Drive woo washing through, as the 'Usual Media' have mega-hyped an obscure Chinese announcement of a 'better' toroidal ion drive, and the 'Usual Suspects' have broken out the champagne, yet again, yet again...

Beyond the obvious Newtonian / Einsteinian issues, I've been unable to find a reliable 'primary source', or even a woo-minimal one for this announcement, so 'Due Care', please ??

FWIW, the 'ion flyer' ? Some years back, our local library had a book by a guy who'd built a series of such. A cross between pico-light aero-modelling, 'kitchen foil' origami and scary DIY EHT PSUs that made me warily 'suck my teeth', those tethered things actually hovered and flew in 'still, dry air'.
When I tried to borrow the book a second time, it had been 'withdrawn' on safety grounds: PSUs non-compliant with 'British Standards'...

( IMHO, his hacked PSUs were no more dangerous than a mid-sized Tesla Coil, but even they are prone to biting users, spamming RF spectrum and, um, 'Spontaneous Combustion'... )

IIRC, even such 'toy' ion-flyers spawned a woo-storm of speculation about 'Black Triangle' aero-space craft with EHT aerospikes...
Not exactly clear as to what it is that you're trying to say. R U talking about the Shawyer EM drive or Ion lifters, Or? We were discussing neither of those. ... Or am I having an Iowa attack and am just CORNfused? : ) K
 
Um, 'NOTA', given they are all currently far from practicable...

I'm sorta-kinda hoping that some-one can kick 'Teleparallel Gravity' into play, given it uses 'mostly respectable' String Theory, and Einstein toyed with it but lacked the math...

I fetch out the 'New Scientist' article about 'TG' about once a week, and it seems to make sense for about ten minutes. Then the grok evaporates again. Mind you, as the same applies to any 'Greek Alphabet Soup' beyond middlin' calculus...
 
I suppose it needs saying.

Woo alert:
Not exactly clear as to what it is that you're trying to say. R U talking about the Shawyer EM drive or Ion lifters, Or? We were discussing neither of those. ... Or am I having an Iowa attack and am just CORNfused? : ) K
Sawyer is 110% woo - take it from a seasoned EM pro. Ion lifters work but are pathetically weak; the principle has long been used for ion thrusters in space, but is nothing more than a fragile toy back down in the gravity well.

Teleparallel Gravity
A fascinating attempt to rewrite fundamental physics, along with a dozen others. Extrapolating it to the real world is on a par with wormholes, time travel, Boltzmann brains and doppelgagers in parallel universes. To parallel the old saying "not even wrong", I'd suggest that it is not even woo.
For information, the curves and twists Einstein worked on are in the domain of a branch of geometry known as topology. I am not a pro this time, but I do have a peer-reviewed track record of sorts. There have been many attempts to unify electromagnetism with gravity, the earliest with any serious possibility being known as Kaluza-Klein theory and two modern contenders being loop quantum gravity and M- or string theory. To pick one of the less developed ones and then bandy it about in high ignorance is not likely to take anyone anywhere useful. Hence my assessment.
 
TG "... is not likely to take anyone anywhere useful."

Always the case: The difference with TG being its math may be hashed out and peer-reviewed long, lonnng before any-one figures how to craft a physical implementation to confirm / falsify the hypothesis...
 
Could you clarify...I'm not sure we're talking about the same thing. I've been discussing "The Plasma Magnet"(ic sail). Are you referring to this propulsion concept or something else? Thnx. K
 
I was attempting to garner a better understanding about difference between EHD and MHD.
This was all because I want to be able to better explain the Plasma Magnet(ic Sail) during presentation.
No woo-hoo about the concept: it's basically a Tesla induction motor (stator) operating in a conductive fluid....the solar wind electrons and ions. If I inadvertently created any confusion, my apologies. , Kevin
 
The article from my initial post, just in case the paywall acts up again:

Star Trek-style 'ionic wind' plane hailed as most significant advance in flight since the Wright brothers​


ByJamie Merrill21
November 2018 • 6:00pm

A revolutionary Star Trek-style electric plane that flies silently and has no moving parts has completed its first test flight, in what is being hailed as one of the most significant advances in flight since the early experiments of the Wright brother more than 100 years ago.

The battery-powered plane, which was developed and tested by engineers at Massachusetts Institute of Technology in the US, is not kept in flight by propellers or a turbine but by an ionic wind system.

The 16ft aircraft is completely silent and colliding electrically charged air molecules provide the thrust needed to make it fly, opening the door to new generation of emissions-free passenger aircraft and silent drones.

Professor Steven Barrett, lead researcher on the project at MIT in Massachusetts, told the Telegraph that the plane’s first flight, which is detailed in the journal Nature, was “super exciting”.

1665785230394.png
The battery-powered plane, which was developed and tested by engineers at Massachusetts Institute of Technology is powered by an ionic wind system


He said: “This is the first time an aeroplane with no moving parts has flown. It’s taken nine years of work to get here, and it’s a hundred years since the ionic wind was first discovered”.
In the tests, the battery-powered unmanned aircraft, that weighs just five pounds, managed sustained flights of 197 ft in an MIT gym hall.

Professor Barrett was inspired to launch the project after watching sci-fi series Star Trek as a child. He was especially impressed by the show's futuristic shuttle crafts that skimmed through space with "just a blue glow and silently glide".

1665785367376.png
The project was inspired by the shuttlecraft featued in sci-fi series Star Trek CREDIT: Sportsphoto Agency


"This made me think, in the long-term future, planes shouldn't have propellers and turbines," he said. "They should be more like the shuttles in Star Trek."

Ionic wind, also known as electroaerodynamic thrust, was first identified in the 1920s and explored by scientists and engineers in the US and at Britain’s Royal Aircraft Establishment at Farnborough in the 1960s, but they were only able to produce very low levels of thrust, insufficient for flight.

To overcome this obstacle, the MIT test aircraft carries an array of thin wires strung beneath the front end of its wings. A high voltage current passed through the wires via a lightweight power converter strips negatively charged electrons from surrounding air molecules.

This produces a cloud of positively charged ionised air molecules that are attracted to another set of negatively charged wires at the back of the plane, like a giant magnet attracting iron filings

As they flow towards the negative charge, the ions collide millions of times with other air molecules, creating the thrust that pushes the aircraft forward.

1665785580151.png

One of the biggest challenges faced by the MIT team was designing a power supply that would generate 40,000 volts from the plane's battery output, one of the biggest stumbling blocks in adapting the technology for large-scale commercial use.

Prof Barrett told the Telegraph that while it will take “several decades” for the technology to be advanced enough to power passenger aircraft, unmanned aircraft with wingspan of up to 80 ft will be possible in the "nearer term".

The silent aircraft has obvious applications as a stealth drone, as it would not be detected by infrared scanners. Defence giant Lockheed Martin has reportedly already expressed interest in the project.

Guy Gratton, an aerospace engineer and visiting professor at Cranfield University, said: “It's clearly very early days: but the team at MIT have done something we never previously knew was possible, in using accelerated ionised gas to propel an aircraft.

“Aeronautical engineers around the world are already trying hard to find ways to use electric propulsion, and this technology will offer something else that in the future may allow manned and unmanned aircraft to be more efficient, and non-polluting.”
 
Thanks Grey! I remember seeing this at some point awhile ago. If I can ever get PMsail project behind me, I'll ask you about Zubrin's Diopole Drive....all sorts of arguments surounding it. K
 
The article from my initial post, just in case the paywall acts up again:

Star Trek-style 'ionic wind' plane hailed as most significant advance in flight since the Wright brothers​


ByJamie Merrill21
November 2018 • 6:00pm

A revolutionary Star Trek-style electric plane that flies silently and has no moving parts has completed its first test flight, in what is being hailed as one of the most significant advances in flight since the early experiments of the Wright brother more than 100 years ago.

The battery-powered plane, which was developed and tested by engineers at Massachusetts Institute of Technology in the US, is not kept in flight by propellers or a turbine but by an ionic wind system.

The 16ft aircraft is completely silent and colliding electrically charged air molecules provide the thrust needed to make it fly, opening the door to new generation of emissions-free passenger aircraft and silent drones.

Professor Steven Barrett, lead researcher on the project at MIT in Massachusetts, told the Telegraph that the plane’s first flight, which is detailed in the journal Nature, was “super exciting”.

View attachment 685550
The battery-powered plane, which was developed and tested by engineers at Massachusetts Institute of Technology is powered by an ionic wind system


He said: “This is the first time an aeroplane with no moving parts has flown. It’s taken nine years of work to get here, and it’s a hundred years since the ionic wind was first discovered”.
In the tests, the battery-powered unmanned aircraft, that weighs just five pounds, managed sustained flights of 197 ft in an MIT gym hall.

Professor Barrett was inspired to launch the project after watching sci-fi series Star Trek as a child. He was especially impressed by the show's futuristic shuttle crafts that skimmed through space with "just a blue glow and silently glide".

View attachment 685551
The project was inspired by the shuttlecraft featued in sci-fi series Star Trek CREDIT: Sportsphoto Agency


"This made me think, in the long-term future, planes shouldn't have propellers and turbines," he said. "They should be more like the shuttles in Star Trek."

Ionic wind, also known as electroaerodynamic thrust, was first identified in the 1920s and explored by scientists and engineers in the US and at Britain’s Royal Aircraft Establishment at Farnborough in the 1960s, but they were only able to produce very low levels of thrust, insufficient for flight.

To overcome this obstacle, the MIT test aircraft carries an array of thin wires strung beneath the front end of its wings. A high voltage current passed through the wires via a lightweight power converter strips negatively charged electrons from surrounding air molecules.

This produces a cloud of positively charged ionised air molecules that are attracted to another set of negatively charged wires at the back of the plane, like a giant magnet attracting iron filings

As they flow towards the negative charge, the ions collide millions of times with other air molecules, creating the thrust that pushes the aircraft forward.

View attachment 685552

One of the biggest challenges faced by the MIT team was designing a power supply that would generate 40,000 volts from the plane's battery output, one of the biggest stumbling blocks in adapting the technology for large-scale commercial use.

Prof Barrett told the Telegraph that while it will take “several decades” for the technology to be advanced enough to power passenger aircraft, unmanned aircraft with wingspan of up to 80 ft will be possible in the "nearer term".

The silent aircraft has obvious applications as a stealth drone, as it would not be detected by infrared scanners. Defence giant Lockheed Martin has reportedly already expressed interest in the project.

Guy Gratton, an aerospace engineer and visiting professor at Cranfield University, said: “It's clearly very early days: but the team at MIT have done something we never previously knew was possible, in using accelerated ionised gas to propel an aircraft.

“Aeronautical engineers around the world are already trying hard to find ways to use electric propulsion, and this technology will offer something else that in the future may allow manned and unmanned aircraft to be more efficient, and non-polluting.”
Ionic-assisted flight using something like those NASA solar ultra-endurance UAVs is an interesting prospect. Not sure that would be enough to generate the necessary voltage, though. I do wonder if you could use it as a sort of auxiliary lift generator on a normal aircraft, just to push the performance envelope that much further. Envisioning something like the active boundary layer control on the ShinMaywa seaplanes driven by a separate compressor engine.
 
If EHD is ever to power aircraft, it is useful to compare it with the electric-powered fans beloved of today's dot-com hopefuls.

Electric propulsion is really quite efficient these days. However EHD is pretty darn inefficient. Besides circuit losses in the high-voltage generator, very little of the energy which goes into ion creation and emission will get converted into forward thrust. Much of it is wasted as heat or glow discharge during recombination at the cathode. Before EHD can make the grade, we will have to develop technologies to recover the energy of recombination and convert it back into electric power.

Rain is sufficiently conductive to play havoc with the ion wind. I have severe doubts whether an EHD drive can function at all in wet weather. Even high humidity will see a significant drop in maximum operating voltage. If you leave the plane out overnight, dew may render it inoperable until it has dried out. If you create a spanwise umbrella shroud like a biplane, you would still have to shake the raindrops from the incoming air. Jet engines in dusty conditions use centrifugal filters, but to install those on an EHD air intake entails either a compact drive with high power density or a shroud bigger than a conventional propeller. Neither solution speaks of practical, efficient engineering.

Reliability: fans have bearings which wear out. But EHD has electrodes, especially the cathode, which erode or corrode under the electrochemical activity of the ions. There is no known technical or scientific principle which offers a route to electrodes which are more durable than bearings. Periodic electrode changes will make for higher operating costs.

Electric fans may have a moving part and whirr a bit, but they do at least work reliably, efficiently, economically and in the rain.

Somewhere I have an SF short story from the 1970s which features an electrostatic hovercraft and graphically illustrates the engineering reasons why the author regarded even such a limited technology as a non-starter.

Perhaps EHD will find a niche in silent stealthy drones or similar, but I doubt if it can ever achieve more.
 
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As an aside, this principle of flight seems to be strictly limited to be used by humans, if at all. But during breakfast,
I was just reading the latest issue of the German Spektrum magazine (my wife is reading her newspaper then , too .. ;) ),
featuring an article about the well known flying spiders, mainly seen during the times of the Indian Summer. For a long time, their abilty to lift off was reasoned by some kind of wind currents, but actually, they are using the natural electric
field in the atmosphere, too, though the principles aren't fully understood still yet.
 
As an aside, this principle of flight seems to be strictly limited to be used by humans, if at all. But during breakfast,
I was just reading the latest issue of the German Spektrum magazine (my wife is reading her newspaper then , too .. ;) ),
featuring an article about the well known flying spiders, mainly seen during the times of the Indian Summer. For a long time, their abilty to lift off was reasoned by some kind of wind currents, but actually, they are using the natural electric
field in the atmosphere, too, though the principles aren't fully understood still yet.

Again, the problem is scaling up. Giant electrically-charged flying spiders, descending on hapless virgins with lightning belching forth from their legs, what a great black-and-white B-movie that would make! :eek: :D
 
As an aside, this principle of flight seems to be strictly limited to be used by humans, if at all. But during breakfast,
I was just reading the latest issue of the German Spektrum magazine (my wife is reading her newspaper then , too .. ;) ),
featuring an article about the well known flying spiders, mainly seen during the times of the Indian Summer. For a long time, their abilty to lift off was reasoned by some kind of wind currents, but actually, they are using the natural electric
field in the atmosphere, too, though the principles aren't fully understood still yet.

Again, the problem is scaling up. Giant electrically-charged flying spiders, descending on hapless virgins with lightning belching forth from their legs, what a great black-and-white B-movie that would make! :eek: :D If you have a serious argument to make, it would be appreciated if you were to make it. Ridicule should not part of this forum.

The fact is that within the theory scaling down is the problem.....
A 10 meter diameter coil with 1 kilowatt would create a much larger RMF than a 1 meter diameter coil powered with 10 kilowatts.
Did you read either or both of the papers?
 

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