Thrusters powered by ionic wind may be efficient alternative to conventional atmospheric propulsion technologies

Apr 03, 2013 by Jennifer Chu
Thrusters powered by ionic wind may be efficient alternative to conventional atmospheric propulsion technologies

When a current passes between two electrodes—one thinner than the other—it creates a wind in the air between. If enough voltage is applied, the resulting wind can produce a thrust without the help of motors or fuel.

This phenomenon, called electrohydrodynamic thrust—or, more colloquially, "ionic wind"—was first identified in the 1960s. Since then, ionic wind has largely been limited to science-fair projects and basement experiments; hobbyists have posted hundreds of how-to videos on building "ionocrafts"—lightweight vehicles made of balsa wood, and wire—that lift off and hover with increased voltage.

Despite this wealth of hobbyist information, there have been few rigorous studies of ionic wind as a viable propulsion system. Some researchers have theorized that ionic thrusters, if used as , would be extremely inefficient, requiring massive amounts of electricity to produce enough thrust to propel a vehicle.

Now researchers at MIT have run their own experiments and found that ionic thrusters may be a far more efficient source of propulsion than conventional . In their experiments, they found that ionic wind produces 110 newtons of thrust per kilowatt, compared with a jet engine's 2 newtons per . The team has published its results in the Proceedings of the Royal Society.

Steven Barrett, an assistant professor of at MIT, envisions that ionic wind may be used as a propulsion system for small, lightweight aircraft. In addition to their relatively , ionic thrusters are silent, and invisible in infrared, as they give off no heat—ideal traits, he says, for a surveillance vehicle.

"You could imagine all sorts of military or security benefits to having a silent propulsion system with no ," says Barrett, who co-authored the paper with graduate student Kento Masuyama.

Shooting the gap

A basic ionic thruster consists of three parts: a very thin copper electrode, called an emitter; a thicker tube of aluminum, known as a collector; and the air gap in between. A lightweight frame typically supports the wires, which connect to an electrical power source. As voltage is applied, the field gradient strips away electrons from nearby air molecules. These newly ionized molecules are strongly repelled by the corona wire, and strongly attracted to the collector. As this cloud of ions moves toward the collector, it collides with surrounding neutral air molecules, pushing them along and creating a wind, or thrust.

To measure an ion thruster's efficiency, Barrett and Masuyama built a similarly simple setup, and hung the contraption under a suspended digital scale. They applied tens of thousands of volts, creating enough current draw to power an incandescent light bulb. They altered the distance between the electrodes, and recorded the thrust as the device lifted off the ground. Barrett says that the device was most efficient at producing lower thrust—a desirable, albeit counterintuitive, result.

"It's kind of surprising, but if you have a high-velocity jet, you leave in your wake a load of wasted kinetic energy," Barrett explains. "So you want as low-velocity a jet as you can, while still producing enough thrust." He adds that an ionic wind is a good way to produce a low-velocity jet over a large area.

Getting to liftoff

Barrett acknowledges that there is one big obstacle to ionic wind propulsion: thrust density, or the amount of thrust produced per given area. Ionic thrusters depend on the wind produced between electrodes; the larger the space between electrodes, the stronger the thrust produced. That means lifting a small aircraft and its electrical power supply would require a very large air gap. Barrett envisions that electrodynamic thrusters for aircraft—if they worked—would encompass the entire vehicle.

Another drawback is the voltage needed to get a vehicle off the ground: Small, lightweight balsa models require several kilovolts. Barrett estimates a small craft, with onboard instrumentation and a power supply, would need hundreds or thousands of kilovolts.

"The voltages could get enormous," Barrett says. "But I think that's a challenge that's probably solvable." For example, he says power might be supplied by lightweight solar panels or fuel cells. Barrett says ionic thrusters might also prove useful in quieter cooling systems for laptops.

Ned Allen, chief scientist and senior fellow at Lockheed Martin Corp., says that while ionic thrusters face serious drawbacks—particularly for aerospace applications—the technology "offers nearly miraculous potential."

"[Electrohydrodynamic thrust] is capable of a much higher efficiency than any combustion reaction device, such as a rocket or jet thrust-production device," Allen says. Partly for this reason, Allen says Lockheed Martin is looking into the technology as a potential means of propulsion.

"Efficiency is probably the number one thing overall that drives aircraft design," Barrett says. "[Ionic ] are viable insofar as they are efficient. There are still unanswered questions, but because they seem so efficient, it's definitely worth investigating further."

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Lurker2358
1.8 / 5 (12) Apr 03, 2013
Ironically I was thinking about this technology yesterday.

I had not realized it was that much more efficient than conventional engines.

110N/kW vs 2N/kW

This doesn't even seem mathematically possible, since the existing aircraft engines were supposedly 20% to 30% efficient.

If these findings prove true, it will validate my claim that the definitions of "Energy" and "Kinetic Energy" are flawed, and moreover, the definition of Gibbs Free Energy in chemistry is also flawed.

For example, 110N thrust applied to 1kg payload for one second produces 110m/s velocity.

Ek = 6,050 Joules @ 110m/s and 1kg mass.

The kinetic Energy is over 6 times the amount of "Joules" of electricity which would be spent in one second; as 1 kilowatt * 1 second equals 1000 Joules.

Thereby confirming my suspicions.

If the findings are true, the definition of energy is flawed.
axemaster
5 / 5 (1) Apr 03, 2013
http://en.wikiped...ficiency

Seems like the jet engine efficiency is indeed 20-30%, so I agree that something seems fishy here. Perhaps they are talking about the max output pressure or something like that - in that case the maximum force wouldn't be directly related to the energy. For example, an open circuit might have 100V available, but actually connecting a load might cause it to drop tremendously.
Shootist
2.3 / 5 (6) Apr 03, 2013
General Electric CF34 = 82.5kN of thrust and 7300 shaft horsepower.

Now I'm no physics boffin, or mechanical engineer, but doesn't 7300 horsepower, more or less equal 5369.14 kilowatts?

Something is amiss.
ShotmanMaslo
3 / 5 (2) Apr 03, 2013
This will be ideal for drone propulsion..
Lurker2358
2 / 5 (4) Apr 03, 2013
Now I'm no physics boffin, or mechanical engineer, but doesn't 7300 horsepower, more or less equal 5369.14 kilowatts?

Something is amiss.


Close enough.

Eikka
4.2 / 5 (10) Apr 03, 2013
The kinetic Energy is over 6 times the amount of "Joules" of electricity which would be spent in one second; as 1 kilowatt * 1 second equals 1000 Joules.


The problem is that as you speed up, you do in fact need to increase your power to maintain the same amount of thrust. If you maintain constant power, the thrust the engine produces, and the acceleration starts to fall off as soon as your engine starts to move.

You will not be getting 110 N of thrust after one second. Instead, you will be moving at 44.7 m/s and your thrust will be 22.4 Newtons instead.

If on the other hand you maintain constant thrust as in a rocket engine or other reaction engine that works by throwing its own mass behind, what you'll notice is that your power does indeed increase as your speed increases, seemingly even beyond the available chemical energy you have on-board because of the gained kinetic energy of the fuel itself. This is called the Oberth effect.
Eikka
4.4 / 5 (7) Apr 03, 2013
The reason why the engine needs to increase power to maintain thrust is simple to understand.

At speed, the engine sees incoming air coming through at speed and to create constant acceleration it must cause a constant increase in the speed of the airstream as it travels through the engine.

The energy needed to make that change is constant, but because the speed of the airstream through the engine increases all the time as it moves faster, the time that the mass of air actually spends inside the engine gets shorter and shorter and therefore the engine must increase power as it or the air speeds up, or it simply won't have the time to add that required amount of energy to the airstream to maintain the constant amount of thrust.

So, you may get 110 Newtons per kilowatt at some specific airspeed, but you won't get it at all airspeeds. Most likely what they're measuring is static thrust which is the engine standing still and pulling stationary air through itself.
Lurker2358
1 / 5 (5) Apr 03, 2013
because of the gained kinetic energy of the fuel itself. This is called the Oberth effect.


I figured this out on my own for hypothetical relativistic rocketry. It's easy to say with anti-matter that if the mass of the fuel increases with velocity, then the energy of the reaction increases.
Eikka
5 / 5 (5) Apr 03, 2013
I figured this out on my own for hypothetical relativistic rocketry.


The Oberth effect really doesn't have anything to do with approaching the speed of light. It's basic Newtonian physics where masses remain what they are.

It's simply due to the fact that you're throwing back fuel that already has kinetic energy that you added to it previously, which is kinda like jumping up in an ascending elevator.
indio007
1 / 5 (1) Apr 03, 2013
Ionic thrusters are not powered by ionic wind.
The force is an asymmetric electrostatic force.
http://arxiv.org/...6111.pdf
Eikka
4 / 5 (4) Apr 03, 2013
ionic thrusters are silent, and invisible in infrared, as they give off no heat—ideal traits, he says, for a surveillance vehicle.


What they do give out instead is radio noise and ultraviolet light due to the corona discharge that propels the air molecules.
alq131
5 / 5 (1) Apr 03, 2013
I seem to recall some wing design which had jets along the leading edge to increase air velocity over the wing, essentially lowering the stall speed. Couldn't the "ionic wind" be used for the same purpose, rather than lift by thrust, just use it to create lift by blowing laminar air over the wing?
indio007
1 / 5 (2) Apr 03, 2013
I seem to recall some wing design which had jets along the leading edge to increase air velocity over the wing, essentially lowering the stall speed. Couldn't the "ionic wind" be used for the same purpose, rather than lift by thrust, just use it to create lift by blowing laminar air over the wing?


There is already a patent for it. Rumor has it that it was in the SR-71.
Yevgen
not rated yet Apr 03, 2013
Efficiency of ionic wind apparatus have been explored and published
years ago, in 2002, and optimized designs have been analysed.
Collection of these publications can be found here:
http://sudy_zhenja.tripod.com/lifter_theory/
daqman
not rated yet Apr 03, 2013
One way of increasing the thrust with no loss of efficiency is to take advantage of the Lorentz force. A charged particle moving through a magnetic field feels a force that is perpendicular to both the field and the direction of motion. This requires modifying the ion wind engine so that there is a magnetic field that is at all times perpendicular to both the electric field and the desired direction of the jet.

In the case of a wire and tube the field would have to be toroidal. Since such fields are difficult to produce at a high field strength a better design is a plane of wires and a single metal plate. In this design the Ions move from the plane of wires to the collector plate and a series of permanent magnets can be arranged to produce the thrust.

I wish I could draw a diagram!
Eikka
3 / 5 (2) Apr 03, 2013
One way of increasing the thrust with no loss of efficiency is to take advantage of the Lorentz force. A charged particle moving through a magnetic field...


You will find it mighty inefficient to maintain a magnetic field without using superconductors, which is a whole other can of worms.
Husky
5 / 5 (3) Apr 03, 2013
I wonder how this play out on the nanoscale, if you cover an complete wing with nanorod electrodes, individual nanorods would needs smaller voltages applied so the airgap, while really tiny inabsolute scale could be made relativelely large to the tiny voltage applied, now add up the sum of all the nanoparts....and well if no impressive thrust can be gained from the compouded nanotods alone, than it still might give a moving boudery layer like golfball dimples and still contribute to more efficient airflow over the wing....
TheGhostofOtto1923
1.5 / 5 (8) Apr 03, 2013
This phenomenon, called electrohydrodynamic thrust—or, more colloquially, "ionic wind"—was first identified in the 1960s
The first lifters or ionocrafts based on Bifield-Brown effect were patented in 1934 already. This principle is highly ineffective though, because the energy expended to air ionization is lost. Such a lifters are essentially just a huge flying generators of toxic ozone. This NASA page summarizes some exotic http://www.grc.na...WW/bpp/.
What, you dont think this is yet one more example of suppressed technology that would have reduced oil consumption and decreased western influence around the world? You know like magnetic motors, cold fusion, and suchlike? You believe everything NASA tells you?
ValeriaT
1.8 / 5 (5) Apr 03, 2013
You believe everything NASA tells you?
Of course not, actually NASA recently withdrew all links to existing reports about concepts, which already proved their feasibility, like the EMDrive a Woodward drives with the following message:
The NASA technical reports server will be unavailable for public access while the agency conducts a review of the site's content to ensure that it does not contain technical information that is subject to U.S. export control laws and regulations

In 1941 Stalin has started to deal with serious research of nuclear bomb, just because all references to nuclear fission suddenly disappeared from western journals.
Q-Star
2.6 / 5 (5) Apr 03, 2013
...Ionic thrusters are not powered by ionic wind. The force is an asymmetric electrostatic force...
They don't work in vacuum.


Psst, Zeph,, we're not talking about a vacuum here. ATMOSPHERIC PROPULSION.

What they do give out instead is radio noise and ultraviolet light due to the corona discharge that propels the air molecules.
They could be detected in ultraviolet because of their ozone generation. And I don't even believe, they will be very quiet. Every lifter is hissing loudly because of massive corona discharge. Such a high-frequency noise can be easily localized.


But since ya brought up vacuum, ozone isn't produced in a vacuum either. Hissing is not transmitted in a vacuum.

Now pick one and register your objections. Atmosphere? Or vacuum? When ya try to cover all the bases, ya get confused (or more confused).
Wolf358
1 / 5 (4) Apr 03, 2013
"Supposedly" NASA patented a reactionless thruster designed around an asymetric capacitor; like the the Bifield-Brown device, but it "supposedly" provides thrust without pushing any air. for example, see: http://www.google...p;q=NASA patent asymetric capacitor&source=web&cd=2&ved=0CEAQFjAB&url=http%3A%2F%2Fintalek.com%2FPapers%2FLifters.pdf&ei=7bRcUfrhPMLF0gGW1YCYDQ&usg=AFQjCNFC73HUa6ueXt9d-yCje2NnGb9qnQ
Wolf358
1 / 5 (4) Apr 03, 2013
Google "NASA patent asymetric capacitor" and you'll see that we're looking first at good old ion wind, but something else as well. All manner of references to tests in vacuum showing measurable thrust without the blessings of Sir Isaac...
TheGhostofOtto1923
1.6 / 5 (7) Apr 03, 2013
Stalin has started to deal with serious research of nuclear bomb, just because all references to nuclear fission suddenly disappeared from western journals
Wait - are you saying that stalin only began doing nuclear weapons research because we suddenly stopped giving it to him? So we should have given it to him, so he wouldnt have done his own research?

But in fact we DID give it to him.
http://en.wikiped...ic_spies

-The most trusted and secure way of sharing sensitive information, is through intelligence agencies. Theyre full of well-trained pros you see.

In order for the cold war to work as Planned, both sides had to be on an equal footing.

Nazi spies were allowed to infiltrate every defense-related industry in the US and so by the beginning of the war they had detailed info and blueprints for all major weapons systems.
http://www.histor...14-1.htm

-These are some of the many Ways in which wars are Planned and the results of them Predetermined.
indio007
1 / 5 (4) Apr 03, 2013
Ionic wind theory can not account for this.
http://jnaudin.fr...ndex.htm

here's video
http://jnaudin.fr...Test.wmv

Tri-ring
not rated yet Apr 04, 2013
If you have ionized material blowing out then it can be further accelerated using Lorentz force with yes using super conductive material. Heating the material will give additional thrust as well.
It will basically be an ionic wind-ion engine hybrid.It can also be used in outer space if some other material substitute the air.
nuge
5 / 5 (1) Apr 04, 2013
A few hundred thousand kilovolts is actually very easy to generate. Use a cockroft-walton multiplier or somesuch. These sorts of things have been around for a very long time, and the electronics behind them is extremely simple and uncontroversial

http://en.wikiped...enerator
Eikka
5 / 5 (1) Apr 04, 2013
Ionic thrusters in vacuum typically use xenon gas for reaction mass. Without a propellant to accelerate they simply don't do anything.

Eikka
5 / 5 (3) Apr 06, 2013
The thruster could theoretically work with electrons: these electrons have sufficient momentum]


No it wouldn't, because expelling electrons would cause the craft to become so strongly charged that it would pull the electrons right back.

The common electron gun works because there is a path back to ground from the target the electrons hit, to form a closed circuit.
Accidental TemporalGhost2_0
2 / 5 (4) Apr 06, 2013
I seem to recall some wing design which had jets along the leading edge to increase air velocity over the wing, essentially lowering the stall speed. Couldn't the "ionic wind" be used for the same purpose, rather than lift by thrust, just use it to create lift by blowing laminar air over the wing?


For what its worth there was a strong "rumor" it is used on the B-2 bomber…

There is already a patent for it. Rumor has it that it was in the SR-71.
ValeriaT
1 / 5 (2) Apr 06, 2013
because expelling electrons would cause the craft to become so strongly charged that it would pull the electrons right back.
Why not - but after then every ionic thruster should face exactly the same problem - it just ejects positively charged ions instead of electrons.
jibbles
3 / 5 (2) Apr 07, 2013
_traw_at
5 / 5 (1) Apr 07, 2013
A caution or two to note when playing with ionocraft: the high amounts of ozone and NOx produced can be a serious health hazard.

Same goes for the high voltages you're dealing with.

http://en.wikiped...onocraft

Play Safely. :-)
Eikka
5 / 5 (1) Apr 07, 2013
Why not - but after then every ionic thruster should face exactly the same problem - it just ejects positively charged ions instead of electrons.


They don't.

In ion wind lifters, only a small portion of the air molecules are actually ionized. Those ions accelerate towards the electrodes and hit the electrodes, some glancing off and some stopping entirely, but along the way there they collide with neutral air molecules and that is the major source of thrust. The ions act more like paddles of a rowboat.

With ion engines designed to work in vacuum, a stream of electrons is shot into the exhaust to neutralize it. This stream of slow electrons actually slows down the exhaust, but since electrons are so much lighter than the ions it doesn't really matter.

You can quickly see that if you designed an engine that exhausts electrons instead of ions, you would need to shoot ions into the cloud of electrons to neutralize it, and the heavier ions would then cause most of the thrust.
Wolf358
1 / 5 (1) Apr 07, 2013
I seem to recall some wing design which had jets along the leading edge to increase air velocity over the wing, essentially lowering the stall speed. Couldn't the "ionic wind" be used for the same purpose, rather than lift by thrust, just use it to create lift by blowing laminar air over the wing?


The Navy is using an analog for high-speed torpedos; a tiny jet of hydrogen out the front of the projectile, and it's no longer dealing with the resistance of the water...
For what its worth there was a strong "rumor" it is used on the B-2 bomber…

There is already a patent for it. Rumor has it that it was in the SR-71.

Cliff Claven
1 / 5 (4) Apr 10, 2013
These high voltages would produce a huge wake of ozone. The EPA will shut this down in a heartbeat.