Ionic Thruster

An Experiment to Determine the Viability of Atmospheric Ionic Propulsion

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This project presents a test rig to measure the thrust produced by the acceleration of ionized air using a static electric field.

The initial thruster design is fairly simple and is divided into two sections. The first section is responsible for producing the negative ions used by the second section. The second section houses screens that produce a static voltage gradient. The static voltage gradient exerts a constant force on the negative ions which pass between the screens and the counter force from accelerating the negative ions produces a forward thrust. Separating the ion production from the acceleration chamber minimizes the chance of producing a conducting channel and triggering an arc-over event.

To minimize fringe effects and promote a uniform voltage gradient, the sides of the chambers will house the voltage multipliers. The multipliers have been designed to present a uniform voltage gradient along their length when energized. With a 12 inch separation and a 108 kV differential voltage, the field strength in the acceleration chamber will be 354 kV/m. This yields 354 kN of force for every coulomb of ions present within the chamber. Assuming a current of 10 mA and air flow of 1 foot per second, there would be 10 mC of ions present within chamber which would produce a force of 3.54 kN or 79 lbs. While impressive, this number does not reflect reality since the resultant force would accelerate the air column which, in turn, would would increase the air flow velocity and reduce the ion density in the chamber. The purpose of this project is to observe the equilibrium state under various ambient air flow velocities and observe the amount of thrust produced and the power consumed.

While the diagram shows the ion emitters as having a potential voltage of -73 kV, this is merely the maximum voltage. The actual system provides current limiting and will supply whatever voltage produces the desired current flow.

Please see #Ionic Thruster Power Supply for details about the voltage source used in this project.

  • Earlier Work

    Robert Rouquette01/26/2016 at 15:41 0 comments

    Here are some images of a simpler test rig I made about a year ago. It wasn't very efficient since it was only intended to provide a load for some voltage multipliers.

    The outer dimensions are 4.25" x 4.25" x 6".

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RichardCollins wrote 05/23/2019 at 22:08 point


If you will tell me what you hope to accomplish (payload, speed, acceleration) and how you intend to measure your results, I might be a bit more specific. I don't have a very good idea of what you have done and intend to do.

Does your device actually move air?  How much?  Do you have a way to measure pressures and forces?  Velocities, vorticity, temperatures, densities, composition?

Here is an interesting approach where they use lasers to activate the air, and then electric fields to provide the energy

I think that ionizing the air, molecule by molecule, is expensive.  Do the numbers.  But, if you can hit molecular groups and transfer momentum, going in the right directions, you can be more efficient.  

I guess your goal is to move craft in air, not move air itself?  Have you done the basic calculation for holding flight?  If you keep the craft perfectly stable, it requires less and less power. When you let things drift the cost goes up.  Could you try to get a self-levitating engine, then try to optimize the measurement systems and controls to reduce the power requirements to the minimum?  Start with dx = (1/2) g * t^2 and try to minimize the uncontrolled time of falling.  That gives a small dt and a higher restoring frequency.  If you use MHz acoustics there might be a sweet spot that gives decent power requirements for weight, and low cost control systems


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RichardCollins wrote 05/23/2019 at 21:40 point

I am trying to understand your example.

3.54 kiloNewtons is 3540 Newtons which is 795.8 pounds of force

Your 108 kV per foot is correctly 354,331 volts per meter

I think your ions are going to be swept out of the air quickly (microseconds?) as soon as you turn on the field. There isn't anything to bind the free ions and electrons to the air itself.

N2 and O2 make up most of the air.  You might be able to modulate the electric field to find resonances to grab onto.  Then you have a way to transfer energy to those molecules.  If you check the literature on measuring sound velocity in air, you find eventually that the sound speed depends on vibrational states of N2 and O2 molecules, and the rates of transfer of that energy between molecules.  There are resources for that kind of calculation but much of it is older and somewhat hard to read -

This NASA paper is fairly readable and seems to indicate you might want to increase the humidity and temperature to get better absorption of the energy in the air.  They used low frequencies, but perhaps you could try audio frequencies to check since it might be easier to build those first at high voltages -

If you modulate at ultrasonic frequencies, you can use a simpler model and treat it like an electrostatic sound generator. 

This Electrostatic Loudspeaker Design Cookbook is old, but they do talk about 75 Watt units, so the power they can deliver is not shabby, and they give fairly specific details of construction and design considerations.

You can get some useful links by googling ["kilowatt" ]

The ultrasound will be quickly absorbed by all the molecules of air, and transmit your force accordingly.  You need to be looking for ways to transmit force and energy to the molecules, and to try to keep the molecule where they are, so they couple to other molecules nearby.

If you google [ "absorption" "ultrasound" "air" ] you will quickly find that you need to be in the MHz and higher acoustic frequencies for most of the energy to be deposited.  If you create a spectrum of frequencies, you can delay absorption according to depth and grab a larger volume of air.  If you put all your energies into very high frequencies they get absorbed nearby and overheat the close molecules.   If you could use LIDAR and Doppler, you can look for molecules going the way you want them to go.  That is the method used for laser cooling.  But it will work for electrostatic fields as well.

You probably do not have access to radioactive sources, but that would be a low cost way to make lots of ions. The problem is coupling them to the air. A miltary craft could use that.

The N-N stretching frequency is 2744 cm-1 which is 0.34021 eV or 82.26305 THz

The O-O stretching frequency is 2061 cm-1 or 0.25553 eV or 61.78723 THz

You could try to polarize the molecules or just grab the polar water molecules and try to use them to entrain the oxygen and nitrogen.

There are lots of ways to move air with electric, magnetic, acoustic and electromagnetic fields.  They all require fairly detailed modelling of the effects, and lots of attention to measuring the effects.  When you are starting out, you might not get much force measurement at all, just indications you got some molecules to go in the right direction.

I did not give credit to your main thrust - ion wind propulsion.  It is fairly advanced in some ways, but also very primitive in others.  Last year

I think they could benefit from modelling and improving the understanding of coupling of the energy they provide, to the microscale turbulent flow they induce.  The trick, I think, will be to pulse the air, then look to see what you have produced, then pulse again, knowing what specific frequencies and directions to use.  In a fully evolved craft, you would continuously monitor the turbulence (search for the words "aeronomy" and "vorticity" and "vorticity" "measurement") and aim your field generator to maximize energy and momentum transfer to the air.  Eventually you can "stand" on the air.  You won't get anything for free, but you can do better than throwing molecules out at subsonic speeds, by using electric fields which are moving at the speed of light or thereabouts.

This NASA report, "An Investigation of Ionic Wind Propulsion" from 2009 has some good notes, but like many it does not treat the whole problem from what is happening in the air.  Like many, they simply assume that they have to use "only ion wind", when there are hundreds of complementary tools and methods they could use to manage all the pieces needed to create a workable craft.  I would go so far as to say that ionic propulsion is only one ten thousandth of what is needed to move craft through the air using fields.

Richard Collins, The Internet Foundation

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