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June 27, 2019, 11:53:49 AM

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Author Topic: Ionic wind?  (Read 1409 times)

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Offline Michael_Rolls

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Ionic wind?
« on: November 23, 2018, 08:07:56 AM »
Seems too good to be true?

https://www.bbc.co.uk/programmes/w3cswmqc

Mike
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Online paulinfrance

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Re: Ionic wind?
« Reply #1 on: November 23, 2018, 08:19:18 AM »
Yes I saw it yesterday, I have put a magnet in the nose and tail of my plane to see if that works as well ,,,  :co
Mode 2 THE only way to fly

Offline itsme

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Re: Ionic wind?
« Reply #2 on: November 23, 2018, 16:32:15 PM »
Its magic. Same magic that lifts wings through thin air and makes little sticks on a box I have control models. Magic. All magic. Dont try to understand it, it will fry your brain.


Offline EssJay

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Re: Ionic wind?
« Reply #3 on: November 25, 2018, 22:20:10 PM »
No trees were harmed by this post, but some electrons have been slightly inconvenienced

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Offline Michael_Rolls

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Re: Ionic wind?
« Reply #4 on: November 26, 2018, 07:35:58 AM »
Thanks for the link - fascinating
Mike
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Re: Ionic wind?
« Reply #5 on: November 26, 2018, 13:10:39 PM »
Ionic propulsion is an interesting concept, but it has extremely low thrust and so needs very large "effector" elements in proportion to the thrust it can produce. This in turn means that it will tend to have a high-ish parasitic drag when used to propel aircraft at low altitudes, so its best application is in very low-speed flight and/or high altitudes where the air density/viscosity is lower.

That it looks like magic is just an example of Arthur C Clarke's 3rd law: "Any sufficiently advanced technology is indistinguishable from magic."

This should never be confused with Jackie Stewert's 1st law (coined by his habit of ascribing Lewis Hamilton's successes entirely to the Mercedes engine): "Any sufficiently consistant magic is indistinguishable from technology."

0.0000006 supplied,

PDR
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Offline itsme

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Re: Ionic wind?
« Reply #6 on: November 26, 2018, 19:52:19 PM »
I think the aim would be high altitude spy/weather/surveillance at slow speeds without ever landing, but surely the tried and tested electric motor system is more efficient? To get the high current would be difficult.

Offline PDR

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Re: Ionic wind?
« Reply #7 on: November 26, 2018, 20:23:37 PM »
The energy required to produce the thrust would be similar in either case, but the ion electrode array would be draggy.

It's difficult to do "slow" at high altitude using wing-lift because the air density is so low. Air density at 50,000 feet is only 15% of the density of the thick soup we wade through at sea level, so an aeroplane that flies at 20mph to maintain height at sea level needs to fly at over 130mph to do the same at 50,000 feet. Fortunately the drag is lower as well, but it does funny things to reynolds numbers and pitches of props.

PDR
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Offline itsme

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Re: Ionic wind?
« Reply #8 on: November 27, 2018, 08:39:38 AM »
The energy required to produce the thrust would be similar in either case, but the ion electrode array would be draggy.

It's difficult to do "slow" at high altitude using wing-lift because the air density is so low. Air density at 50,000 feet is only 15% of the density of the thick soup we wade through at sea level, so an aeroplane that flies at 20mph to maintain height at sea level needs to fly at over 130mph to do the same at 50,000 feet. Fortunately the drag is lower as well, but it does funny things to reynolds numbers and pitches of props.

PDR
Yeah, its all relative, as some bloke said. The idea could also work on Mars I suppose. Be interesting to see which is more efficient at those heights.


Offline PDR

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Re: Ionic wind?
« Reply #9 on: November 27, 2018, 13:34:25 PM »
Mars is an interesting problem. The atmosphere is very thin even at the surface - about 0.6% ISO sea-level density (ie roughly the same as our atmosphere at ~110,000 feet)*, and the temperature varies from around -20C to -100C.

The low density causes stall speeds to be much higher, while the low temperature causes the speed of sound (and the onset of compressibility effects) to be much lower. The net result is that pretty well any aeroplane design ends up treatiung a fine line between stall buffet and mach buffet trhoughout the whole flight - a genuine "coffin corner" in the flight envelope.

Even if you can keep it subsonic the aeroplane would need to travel much faster, and that's problematic. Lift and drag increase with the square of airspeed, so if you double the airspeed you get four times the lift. But you also get four times the drag, which means that you need eight times the power to do it. And so it all starts stacking up against you. We (the industry, ESA, NASA etc) have looked at "Mars Plane" projects many times, but we haven't seen an answer so far.

PDR

* That's the only real technical blooper in the film "the Martian" - the atmosphere is so thin that even gale-force storms wouldn't produce the dynamic pressure required to lob an antenna array (the accident at the start of the film). But it's just the one - the three other minor bloopers can be forgiven in the name of dramatic license
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

Offline itsme

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Re: Ionic wind?
« Reply #10 on: November 27, 2018, 15:21:37 PM »
Mars is an interesting problem. The atmosphere is very thin even at the surface - about 0.6% ISO sea-level density (ie roughly the same as our atmosphere at ~110,000 feet)*, and the temperature varies from around -20C to -100C.

The low density causes stall speeds to be much higher, while the low temperature causes the speed of sound (and the onset of compressibility effects) to be much lower. The net result is that pretty well any aeroplane design ends up treatiung a fine line between stall buffet and mach buffet trhoughout the whole flight - a genuine "coffin corner" in the flight envelope.

Even if you can keep it subsonic the aeroplane would need to travel much faster, and that's problematic. Lift and drag increase with the square of airspeed, so if you double the airspeed you get four times the lift. But you also get four times the drag, which means that you need eight times the power to do it. And so it all starts stacking up against you. We (the industry, ESA, NASA etc) have looked at "Mars Plane" projects many times, but we haven't seen an answer so far.

PDR

* That's the only real technical blooper in the film "the Martian" - the atmosphere is so thin that even gale-force storms wouldn't produce the dynamic pressure required to lob an antenna array (the accident at the start of the film). But it's just the one - the three other minor bloopers can be forgiven in the name of dramatic license
So Arthur Clarke had it right back in the fifties with his rocket powered moon jumpers in 'A Fall of Moondust'

Offline flynn

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Re: Ionic wind?
« Reply #11 on: November 29, 2018, 16:07:22 PM »
Maybe you could argue that it wasn't just the wind that dislodged the dish but the combined effect of the wind and the mass of sand that was being blown along with the wind?...   oooo.. I wonder if this is a can of worms or me showing my lack of knowledge of physics? :xx

Offline PDR

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Re: Ionic wind?
« Reply #12 on: November 29, 2018, 19:08:33 PM »
Maybe you could argue that it wasn't just the wind that dislodged the dish but the combined effect of the wind and the mass of sand that was being blown along with the wind?

The Martian wind wouldn't lift that much sand for essentially the same reason.

PDR
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Offline itsme

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Re: Ionic wind?
« Reply #13 on: November 30, 2018, 08:01:40 AM »
The Martian wind wouldn't lift that much sand for essentially the same reason.

PDR
but they do have massive sandstorms...https://www.youtube.com/watch?v=JcMpO4Tn0UE

Offline PDR

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Re: Ionic wind?
« Reply #14 on: November 30, 2018, 11:59:36 AM »
They do, but the sand is a fine dust that doesn't significantly increase the air density, so it doesn't add the extra pressure/force needed to throw a large antenna (which was the original question). The dust is like flour - it's so fine that it gets into shaft bearings and gears and bungs them up (technical term) - this has been the most common cause of final terminal failure in mars exploration vehicles IIRC.

PDR
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Re: Ionic wind?
« Reply #15 on: November 30, 2018, 14:45:05 PM »
Must be bad having Chronic wind  :o
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Offline SteveBB

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Re: Ionic wind?
« Reply #16 on: December 01, 2018, 01:14:13 AM »
They do, but the sand is a fine dust that doesn't significantly increase the air density, so it doesn't add the extra pressure/force needed to throw a large antenna (which was the original question). The dust is like flour - it's so fine that it gets into shaft bearings and gears and bungs them up (technical term) - this has been the most common cause of final terminal failure in mars exploration vehicles IIRC.

PDR



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Offline PDR

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Re: Ionic wind?
« Reply #17 on: December 01, 2018, 07:13:19 AM »
Are you calling me a pirate?

PDR
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Offline itsme

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Re: Ionic wind?
« Reply #18 on: December 01, 2018, 08:59:33 AM »
Are you calling me a pirate?

PDR
he was talking to the parrot

Offline SteveBB

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Re: Ionic wind?
« Reply #19 on: December 01, 2018, 17:13:33 PM »
he was talking to the parrot

Martian parrots? I bet they can fly.
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Offline Phil_G

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Re: Ionic wind?
« Reply #20 on: December 02, 2018, 11:01:15 AM »
"The Martian" is a very technically satisfying read, and those who only saw the film have missed out,
To me, Marks detailed thought processes were the essential theme of the story and most of that was lost.
Is anyone following Insight?  isnt the lack of updates frustrating?  $%&
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Phil

« Last Edit: December 02, 2018, 11:02:20 AM by Phil_G »

Offline PDR

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Re: Ionic wind?
« Reply #21 on: December 02, 2018, 12:02:39 PM »
"The Martian" is a very technically satisfying read, and those who only saw the film have missed out,
To me, Marks detailed thought processes were the essential theme of the story and most of that was lost.

Absolutely agree. When I bought the bluray Sainsburys were giving away the the book with it, and I'm very glad they did because I wouldn't have thought of buying it afterwards. It's not the greatest literary work ever written (it was his first attempt at a book), but it's a fascinating read. The story is longer and richer (the journey from the Hab to the MAV that takes 5 mins of screen time is a third of the book), and a lot of the blanks are filled in (like why the Hab exploded).

Don't get me wrong - I love the film*, but reading the book makes the film experience even better. Do both - they complement eachother.

PDR

* I'm part of a group who are trying to get the guvmint to negotiate a license so that the film and the book can be incorporated into the national curriculum for kids aged about 13-14 to foster interest in STEM subjects as a career.
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Offline itsme

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Re: Ionic wind?
« Reply #22 on: December 02, 2018, 14:41:24 PM »
Absolutely agree. When I bought the bluray Sainsburys were giving away the the book with it, and I'm very glad they did because I wouldn't have thought of buying it afterwards. It's not the greatest literary work ever written (it was his first attempt at a book), but it's a fascinating read. The story is longer and richer (the journey from the Hab to the MAV that takes 5 mins of screen time is a third of the book), and a lot of the blanks are filled in (like why the Hab exploded).

Don't get me wrong - I love the film*, but reading the book makes the film experience even better. Do both - they complement eachother.

PDR

* I'm part of a group who are trying to get the guvmint to negotiate a license so that the film and the book can be incorporated into the national curriculum for kids aged about 13-14 to foster interest in STEM subjects as a career.
The book is now on my Xmas list! Never thought of that, loved the film. As an aside, I also loved First Man. Well worth seeing.


 

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