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Ionocraft or "lifters" are lightweight devices that produce thrust by ionizing the air around an electrode, and then accelerating the ions toward another electrode with an electric field, during which the ions push against neutral air molecules and produce thrust.

Ionocraft flying

There used to be a Wikipedia article for "Electrohydrodynamic thruster", which was deleted for not having any references. It said that the efficiency can be improved by separating the ionization and acceleration into stages, and using multiple acceleration stages:

Ionocrafts 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.

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. 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.

Are the claims in this article realistic/true? Know any references for it? Is this well-known under a different name?

Sounds like the same principle as Electrostatic fluid accelerators? But that article says "[Generating thrust] relies on the same electrodes and electric field as the corona [ionization] process."

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i don't know, but definitely sounds like a great homegrown experiment to do! –  diffeomorphism Sep 7 '12 at 20:29
    
@diffeomorphism: If I understood the principle behind the claim, sure. –  endolith Feb 5 '13 at 16:09

1 Answer 1

I am an engineering student making an ionocraft as my master's project, these are my 2 cents:

Initially, there is the problem of space charge saturation: simply put, there is an upper limit to the amount of ions that can coexist in a given space. This has been shown and modelled in papers concerning high voltage coronas. Another way to see this is as a saturation current, which is a limit on the basic electrokinetic equation, F=id/k.

Realistically, I cannot stress enough how difficult it would be to manufacture something that would be effective in accelerating your ions over great distances at this scale and weight class.

Additionally, I can't think of a way that you could "accelerate" your ions without using an electric field (which is how ionocrafts work in the first place). Increasing the voltage causes a spark that kills your effect unless you increase the air gap accordingly. This however is the only way to get more thrust. This leads to increasingly larger models with increasingly chunkier power supplies used.

Concerning two stage mechanisms, currently there is some work being done with theoretical models and EHD simulations concerning optimising the flow in an asymmetric capacitor with multiple voltage sources, one negative and one positive. This however wouldn't be of practical use to an ionocraft, since most of the thrust comes from the reactions of the coulomb forces in the ions colliding with air molecules, not the gas flow.

I hope this helps!

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"there is an upper limit to the amount of ions that can coexist in a given space" Ah, hadn't heard of that. But what is the limit for air in practical terms? –  endolith Jan 31 '13 at 18:56
    
Also, I don't think the term "asymmetric capacitor" should be used. A capacitor is a device that stores electrical energy by setting up an electric field (with no current flow) between two plates. An ion thruster necessarily does have a current between the plates, and is not meant to store energy, so the term "capacitor" is not valid. Vacuum tubes have plates of metal near each other with charges on them, too, but we don't call them capacitors. –  endolith Jan 31 '13 at 18:59

protected by Qmechanic Jul 22 at 19:30

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