Would it be possible? - A fifth mode of transport

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Would it be possible? -- A fifth mode of transport...

There has been a lot of talk about developing a fifth mode of transport, and most of these involve some sort of tube such as the hyperloop idea from Elon Musk. Now I don't know why but I have the idea stuck in my head that the fifth mode of transport should not be close to the ground, but should be around 400-500m above ground, underneath airplanes but above everything else.

From here I began thinking of a method of doing this, for instance would it be possible/viable to have some sort of transport similar to a harrier jumpjet that could "hover" as such and be boarded that high up? I then began to consider the fact that the cost efficiency of this would not be worth even considering, which is when ion drives came to mind. Now i'm no expert on this sort of thing whatsoever and i'm sure a lot of corrections/flaws will be pointed out in my idea, but the cheapness of using an ion drive (after the initial investment) appears to be relatively good. Again i'm not even sure if the use of ion drives in anywhere other than space is possible.

To actually operate this mode of transport I was picturing that you could take the current gps systems and (once improved) simply raise it up 400-500m and create a new virtual transport grid. So yes they would be automatic. Essentially, in a nut shell, it would be a taxi service.

This may well be laughed at and just remain a fantasy inside my own head, but I thought it might be worth to get a few opinions on the matter before I carried on thinking about it any further. In addition to this I am aware I have not thought about every single aspect of this, nor am I giving any validity to this idea.
 

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  • #2
phinds
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You would do well to look into ion drives a bit. You clearly don't understand them at all.
 
  • #3
Like I said I haven't exactly looked into this at all, and I've posted here because if someone is able to confidently tell me there isn't a chance in hell then it would save a lot of time
 
  • #4
I'm not here to be a snob, i'm here to learn. So i'd really appreciate it if it could be explained why it isn't possible, where the flaws are etc. Instead of just telling me I don't know what i'm talking about when I've clearly stated this is just something i'm throwing out there.
 
  • #5
phinds
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I'm not here to be a snob, i'm here to learn. So i'd really appreciate it if it could be explained why it isn't possible, where the flaws are etc. Instead of just telling me I don't know what i'm talking about when I've clearly stated this is just something i'm throwing out there.
If you actually want to learn then look into ion drives even a little, say using Wikipedia, and you'll see what I mean fairly quickly.
 
  • #6
Ibix
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I think I get the general idea. That ion drives are only useful in space because of the lack of gravity affecting it, hence why a large rocket is used to escape earths atmosphere. Fair enough. That discounts the ion drives, however are there any possible methods which could be used to create such a system as I've described?
 
  • #8
phinds
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I think I get the general idea. That ion drives are only useful in space because of the lack of gravity affecting it, hence why a large rocket is used to escape earths atmosphere. Fair enough. That discounts the ion drives, however are there any possible methods which could be used to create such a system as I've described?
No, gravity is not the issue. The ion drives in space still have to push mass, just as they would on Earth.

If you had a frictionless rail system an ion drive would STILL be useless for what you suggest.
 
  • #9
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Time is the important difference. A trip to other planets takes months to years, it does not matter if you need one week to accelerate. To travel from one town to another, that would be extremely impractical.

Like I said I haven't exactly looked into this at all
There is a huge difference between "there are some technical issues that might be problematic" and "I propose a system which is too weak by a factor of at least 10000".
 
  • #10
Ryan_m_b
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There has been a lot of talk about developing a fifth mode of transport
Fifth? You mean after the car, the bike, the bus, the tram, the train, the monorail, the helicopter, the plane, the airship and the boat to name a few common methods?

From here I began thinking of a method of doing this, for instance would it be possible/viable to have some sort of transport similar to a harrier jumpjet that could "hover" as such and be boarded that high up?
An airship could cover that, I remember hearing a few years ago about renewed interest in commercial passenger airships.

I then began to consider the fact that the cost efficiency of this would not be worth even considering, which is when ion drives came to mind. Now i'm no expert on this sort of thing whatsoever and i'm sure a lot of corrections/flaws will be pointed out in my idea, but the cheapness of using an ion drive (after the initial investment) appears to be relatively good. Again i'm not even sure if the use of ion drives in anywhere other than space is possible.
Ion drives have veeeeeeeeeeery low thrust. Taking days to get to 60mph doesn't strike me as a useful transport system (and that's not taking into account wind resistance).

To actually operate this mode of transport I was picturing that you could take the current gps systems and (once improved) simply raise it up 400-500m and create a new virtual transport grid. So yes they would be automatic. Essentially, in a nut shell, it would be a taxi service.
Supposing for a moment that floating a small vehicle a few hundred metres up was economical and safe why would it have to follow GPS on the ground? Aside from the obvious dangers of trying to fly through a mountain tunnel a few hundred metres above the road wouldn't it be more sensible to just fly along a suitable flight path between A and B?
 
  • #11
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This may well be laughed at and just remain a fantasy inside my own head
I am aware I have not thought about every single aspect of this, nor am I giving any validity to this idea.
if it could be explained why it isn't possible, where the flaws are etc. Instead of just telling me I don't know what i'm talking about
This seems contradictory to me. It seems you want people not to tell you you don't know what you're talking about, but you want people to explain why you don't know what you're talking about.

The biggest issue here for me is that you need to do some sort of basic research before you just throw things to the community. Even a simple Wikipedia search would have told you why this wouldn't work. It would have been less costly for you to do that than to write up your idea and explain it and less work for us to read it, understand it, then do the basic search and report to you. Hopefully you can be more considerate of that next time.
 
  • #12
phinds
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The biggest issue here for me is that you need to do some sort of basic research before you just throw things to the community. Even a simple Wikipedia search would have told you why this wouldn't work. It would have been less costly for you to do that than to write up your idea and explain it and less work for us to read it, understand it, then do the basic search and report to you. Hopefully you can be more considerate of that next time.
Well said.
 
  • #13
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I think instead of ion thrust you meant to say an ionocraft, which will work in the atmosphere but requires a great deal power with extremely high voltage. Not to mention ionizing the air produces O zone.


The airship would be close to what you are describing and I too believe it could be a great means of mobility. Ive always though the airship could come back as the new luxury "airliner" for cross country or transcontinental movement. I think it would be a wonderful experience to spend a week floating a few hundred(?) feet in the sky seeing the entire country.
 
  • #14
phinds
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I think instead of ion thrust you meant to say an ionocraft ...
Kind of hard to see how you think he meant anything other than ion thrust since that's what this whole thread has been about and the term has been used repeatedly, including by the OP.
 
  • #15
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Well, they are easy to confuse from a beginners standpoint. He may not have realized there are two ion based modes of transportation which are generally ill suited to the task at hand.
 
  • #16
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I see your point Aero, but I still say a simple Wikipedia search would have cleared the difference up.
 
  • #17
To someone that didn't know the difference and didn't know ANY science they could still be confused after reading the wiki I think. All he would know is that they both work using ionics.
 
  • #18
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It's a valid idea actually. If one used ionocraft technology properly scaled up and integrated it into aircraft it could work as an air taxi service. Sort of like a flying car. And GPS could be used for navigational support.
 
  • #19
Ryan_m_b
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It's a valid idea actually. If one used ionocraft technology properly scaled up and integrated it into aircraft it could work as an air taxi service. Sort of like a flying car. And GPS could be used for navigational support.

Welcome to the forums. An ion drive and an ionocraft are not the same. In any case have you done a calculation to determine the necessary size of a man rated ionocraft? I bet it would be extremely prohibitive.
 
  • #20
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Yes an ion drive has a lower density thrust since the propulsive mass is ions, that's why its use is limited to space propulsion applications that don't require high velocities.

Anyway MIT did a study last year on ionocraft and found that they're a method of propulsion that's 50 times more efficient than Jet Engines.

http://newsoffice.mit.edu/2013/ionic-thrusters-0403

And given that it's such a potentially revolutionary propulsion technology with no moving parts it's surprising that few in academia or industry have seriously researched it.
 
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  • #21
cjl
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Yes an ion drive has a lower density thrust since the propulsive mass is ions, that's why its use is limited to space propulsion applications that don't require high velocities.

Anyway MIT did a study last year on ionocraft and found that they're a method of propulsion that's 50 times more efficient than Jet Engines.

http://newsoffice.mit.edu/2013/ionic-thrusters-0403

And given that it's such a potentially revolutionary propulsion technology with no moving parts it's surprising that few in academia or industry have seriously researched it.
That's one of those headlines that is misleading at best - it's simply stating the well known fact that for a given amount of thrust, you use less power if you have a higher mass flow rate with a lower exhaust velocity. It's the same reason propellers are more efficient than jet aircraft at low speeds, and why turbofans are more efficient than turbojets at moderate speeds. You can gain a similar benefit though by simply using a really large propeller powered by a turboshaft engine, and I'd be curious to see how their ionic wind craft compares in efficiency to something like a helicopter main rotor, which also uses the principle of moving a very large volume of air.

(Also, using something like this with a very large mass flow rate and a low exhaust velocity does give you a good static thrust per watt, but it isn't very good as soon as you actually want to go somewhere - with a very low exhaust velocity, your top speed is quite limited)
 

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