Ion aircraft propulsion

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I saw a video on youtube and it explains in a vague way how the system works, so there is a potential difference between two sets of electrodes and air between them is ionized in the presence of the E field but how muhc is it ionized?
Because I get the impression that the ionization is not in the range of creating and arc as that would short circuit the electrodes and require massive amounts of current and also probably ruin the propulsion, so how much exactly they ionize the air and how much current is there between the electrodes when operating?


It seems this approach differs from the one NASA uses for spacecraft?

 

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  • #2
anorlunda
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If anyone can find a link to a peer reviewed paper, it would be welcome. I found this very brief explanation.

http://news.mit.edu/2018/first-ionic-wind-plane-no-moving-parts-1121 said:
Once the wires are energized, they act to attract and strip away negatively charged electrons from the surrounding air molecules, like a giant magnet attracting iron filings. The air molecules that are left behind are newly ionized, and are in turn attracted to the negatively charged electrodes at the back of the plane.

As the newly formed cloud of ions flows toward the negatively charged wires, each ion collides millions of times with other air molecules, creating a thrust that propels the aircraft forward.
...
The team flew the plane a distance of 60 meters (the maximum distance within the gym) and found the plane produced enough ionic thrust to sustain flight the entire time. They repeated the flight 10 times, with similar performance.
Don't expect airliners with ion drives, but there are specialty cases where this kind of drive might be useful. One article mentioned high-altitude solar-powered aircraft to serve as communication repeaters.
 
  • #3
sophiecentaur
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The Dyson Fan must work on the same principle. These are very expensive, for what they do and are mainly novelty value I think. At sea level pressures, I cannot see and real advantage when you think how light weight the small permanent magnet motors are but, at high altitude, you could well find that the device could take over when a conventional airscrew could need an inconvenient area, just to transfer enough momentum into the rarified air.
Re Space craft propulsion: for a spacecraft, you need to supply your own propellant (as with a rocket), whereas for an aircraft there is always some atmosphere available to use as propellant. That's a significant difference.
 
  • #4
RPinPA
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Don't expect airliners with ion drives, but there are specialty cases where this kind of drive might be useful. One article mentioned high-altitude solar-powered aircraft to serve as communication repeaters.
My first thought was, "it would be cool but a little frightening to ride an aircraft with silent propulsion but also know there were no engines".

But then I read that, as you say, they're thinking more in terms of very small drones. Going to smaller rather than larger aircraft. That mosquito who is pestering you might be a spy plane!

I haven't read any detailed articles about this technology yet, but if they're talking about using it to achieve long endurance, i.e., staying up months at a time, that's an enabler for all kinds of missions, including as you say communication nodes that don't have to be in space. Imagine what you could do with "geostationary" aircraft that didn't have to be over the equator!
 
  • #6
russ_watters
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I saw a video on youtube and it explains in a vague way how the system works, so there is a potential difference between two sets of electrodes and air between them is ionized in the presence of the E field but how muhc is it ionized?
Because I get the impression that the ionization is not in the range of creating and arc as that would short circuit the electrodes and require massive amounts of current and also probably ruin the propulsion, so how much exactly they ionize the air and how much current is there between the electrodes when operating?
Here's a description of the principle of operation:
https://en.wikipedia.org/wiki/Ionocraft
It includes a comment about the MIT plane.
It seems this approach differs from the one NASA uses for spacecraft?
It strikes me as similar, but I'm not sure of the details. One obvious difference though is that ion thrusters on spacecraft carry their own reaction mass.
 
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  • #8
russ_watters
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Dyson have mains voltage to play with so that could be why it's different. I meant the similarity is what happens with the ions.
No, what's different is that Dyson fans are just fans - they don't use ions at all.

This is why I think Dyson is little more than a charismatic fraud.
 
  • #9
LURCH
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This looks like an airborne version of magneto-hydrodynamic drive used on the Yamato-1.
 
  • #10
sophiecentaur
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No, what's different is that Dyson fans are just fans - they don't use ions at all.

This is why I think Dyson is little more than a charismatic fraud.
Haha. I was completely taken in by the sales talk. Thanks for putting me right.
You saved me a pile of money because I no longer want one!!!!
 
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  • #11
sophiecentaur
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Haha. I was completely taken in by the sales talk. Thanks for putting me right.
You saved me a pile of money because I no longer want one!!!!
It's even worse than that. I saw a YouTube video of someone making a DIY 'bladeless fan' and I thought it was a con.
 
  • #12
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I suppose this ion thrust has, well very little thrust so it can only lift very light objects. It would probably take an extremely large electrode area to lift something as heavy as a passenger jet weighing about 200 tons ?

Since semiconductors are small and lightweight these days maybe such a ion drive could replace costly satellites and I guess satellites cannot be recovered but these could?


Reading the info given here it seems that the PD across the electrodes is made such that the air between them is near the point of forming an arc but not close but just enough to ionize the molecules?
Since the air is ionized but there is no arc how much current is transferred between the electrodes I simply wonder how efficient is such a propulsion system?
 
  • #13
OmCheeto
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I suppose this ion thrust has, well very little thrust so it can only lift very light objects. It would probably take an extremely large electrode area to lift something as heavy as a passenger jet weighing about 200 tons ?
I think it's somewhat a moot point, as these devices run around 40,000 EXPOSED volts, and probably shouldn't be taken outside.
It would be an interesting math problem though. From my calculations, based on an MIT experimental device's best performance, a 200 ton helicopter would only require 16 megawatts to fly. (Which is equivalent to about 22,000 hp)
(I switched your "jet" to "helicopter", as I couldn't imagine football fields of flimsy foil flying around at high speeds)

Since semiconductors are small and lightweight these days maybe such a ion drive could replace costly satellites and I guess satellites cannot be recovered but these could?
As referenced earlier in post #6, "ionocraft", (aka "electrohydrodynamic") type drives don't work in a vacuum. (from the wiki reference)

Reading the info given here it seems that the PD across the electrodes is made such that the air between them is near the point of forming an arc but not close but just enough to ionize the molecules?
Since the air is ionized but there is no arc how much current is transferred between the electrodes I simply wonder how efficient is such a propulsion system?
Not much current flows. The units I've looked at run in the single milliamp range.
As to their efficiency. I'm hesitant to state my findings, as I find it hard to believe.

Meh. What the hell: They use less power than helicopters, to hover.

W/kg what
304 Mi-26 helicopter [ref]: all helicopters: powerplant rating/max takeoff weight
311 CH-47 "Chinook" helicopter [ref]
264 Bell 212 helicopter [ref]
213 Bell 206 helicopter [ref]

306 AA108 personal drone [ref]: 2.6 Wh battery/(weight * 6 minute flight time)

143 Masuyama 2012 masters project ionocraft [ref]; "68.43 mN/W"
89 Masuyama & Barrett 2013 ionocraft [ref]; "100 N/kW"

1000 wiki's ionocraft claim [ref]; "1 gram per watt"
12500 RimstarOrg 2012 ionocraft [ref]: 25,000 volts * 1 ma / 2 grams

--------------------------
Ah! I just discovered that the "Barrett" in my 89 W/kg reference is the same person as in your original video! What a small world.
 
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  • #14
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I wasn't thinking that they would orbit outside atmosphere as there is a vacuum sure, I was thinking that maybe they could hoover in the upper atmosphere being lightweight and replace some of the functions satellites currently do ? when in need of update or repair or recharge or whatever one simply makes it go down?
 
  • #15
OmCheeto
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I wasn't thinking that they would orbit outside atmosphere as there is a vacuum sure, I was thinking that maybe they could hoover in the upper atmosphere being lightweight and replace some of the functions satellites currently do ? when in need of update or repair or recharge or whatever one simply makes it go down?
Off the top of my head, I think it would be difficult.
The first thing I would look at, was if someone else has done this.
And the answer is yes. (Kind of. They did experiments.)
The Helios Prototype was the fourth and final aircraft developed as part of an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as atmospheric satellites, to perform atmospheric research tasks as well as serve as communications platforms. [ref]​

From data there:
20000 m___ altitude
1052_ kg__ weight
1500_ w___ engine consumption
10___ unit engines
15000 w___ total power consumption
18500 w___ solar power​

I got:
14 w/kg​

Which is a much better number than the best ionocraft, so far.
And I don't know what the thrust numbers are for an ionocraft at 20 km altitude, where my calculations say that atmospheric pressure is only 6% that of sea level.

There are of course, other problems:
power to weight ratio of batteries and solar cells
energy to weight ratio of batteries (important when the sun goes down)
and probably more​

But, there's always new technology popping up every day:

Conventional silicon-based solar modules produce about 6.8 watts per lb. (15 watts per kilogram), but these new devices can generate more than 2,720 watts per lb. (6 watts per gram), or about 400 times as much. [ref]​

6000 watts/kg! :oldsurprised:
Wow!

So, maybe someday.
 
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  • #16
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indeed wow 6kw per kg sounds very very strong. I would want one of those for my house to be honest
 

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