Flight of an aeroplane with solid-state propulsion

[rfeecs]

So it's an ion engine propelled model airplane.

 https://www.nature.com/articles/s41586-018-0707-9 (Paywalled article)

Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forces accelerate ions in a fluid^1,2, has been proposed as an alternative method of propelling aeroplanes—without moving parts, nearly silently and without combustion emissions^3,4,5,6. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelled heavier-than-air aeroplane.

https://www.technologyreview.com/s/612451/an-electric-plane-with-no-moving-parts-has-made-its-first-flight/ (Free article with a short video)

[Domagoj T]

I am not convinced that the video shows a sustained flight. The plane was launched from a raised platform using a catapult. Without proper measurements, it's hard to tell if it maintains both airspeed and altitude, or just uses the initial kinetic energy from the catapult to fly for those few seconds of the video.
In any case, not only energy storage tech is nowhere near the needed level for full scale applications, this seems to be a very low efficiency approach to thrust generation.
There have been talks about battery powered airliners using conventional ducted fans, but even those, while realistically possible, are facing issues that make them non competitors to jets, mainly due to the need to haul all those heavy batteries during the entire flight, reducing the autonomy and negatively affecting safety during landing.
I call it a gimmick.

[Urs42]

https://www.nature.com/articles/s41586-018-0707-9 (Paywalled article)

sci-hub helps with the paywall: http://sci-hub.tw/https://www.nature.com/articles/s41586-018-0707-9

[Berni]

A full sized human carrying airplane with solid state propulsion has already been built by the Russians in 1961.

https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL

Its basically a bomber that had a nuclear reactor strapped to its wings. Air would simply flow trough the hot reactor core, rapidly expand and create more thrust out the back.

But one could argue solid-state flight was achieved even before that. The first supersonic jet engine used a similar method of operation where it was pretty much a hollow pipe where they would squirt jet fuel into. The contours of the pipe manipulates the air speed inside to below supersonic to allow a stable burn before using the extra volume of hot air to speed it back up and throw it out the back. Its not quite solid state since you have to push liquid fuel into it but its pretty close.

Pulsejet engines also only squirt in fuel and burn it and they ware also used to fly a plane. The Germans used them to create unnamed planes with explosive strapped to them as a early alternative to long range missiles.

[helius]

"Solid-state" is being used in a very misleading way here. The term properly refers to devices which utilize the electronic or magnetic properties of materials in the solid phase (as opposed to the liquid, gas, or plasma phases). Ion propulsion obviously does not qualify as it is plasma based. Neither do jet engines as their thrust is provided by a gas.

[T3sl4co1l]

The only interpretation I can find: yet another MIT backslide.

"Lifters" have been known among high voltage enthusiasts for decades.  I don't see how any of this can be original and new; how did it get published?  What did they establish or refine?

I shouldn't be so negative.  Maybe it's a review of the literature on the subjects, and the demonstration is incidental to the paper?

Tim

[rstofer]

It is just a teaser to get DARPA interested.  Think about totally silent drones - how cool is that?

[BrianHG]

Think about totally silent drones - how cool is that?

This is the 1 big thing about it.  However, thrust is just enough to keep it off the ground, so, a launcher will be needed...
Though, I wonder how weather and humidity will affect it.  Rain alone may destroy the thrust.  Also, in the evening, there may be a visible aura...

[SiliconWizard]

We provide a proof of concept for electroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions.

Uh huh. It may fail to mention whatever else is emitted, though.

[Gyro]

Uh huh. It may fail to mention whatever else is emitted, though.

Having done the experiment (lifter), I can say that it kicks out a hell of a lot of Ozone!

https://www.eevblog.com/forum/dodgy-technology/ionic-lifters-has-anyone-else-around-here-build-one/

[rdl]

Short article at Ars Technica with a bit more info:

Ion drive meets drone, as small plane flies with no moving parts

[Domagoj T]

it kicks out a hell of a lot of Ozone!

So the marketing department doesn't even have a right to stick a "non-polluting" sticker on it.

EDIT:
What's the power consumption and thrust of such a device?

[Gyro]

EDIT:
What's the power consumption and thrust of such a device?

It depends very heavily on construction and complexity. A rough estimate from existing lifter designs is anything from 50W for 0.1 Newtons thrust, to 300W for 2.5 Newtons. That actually compares very favorably with the Ion thrusters that NASA experiments with / uses for Space, those are in the order of 100kW for 5.4 Newtons thrust!

You'll find useful links in my thread that I already linked: https://www.eevblog.com/forum/dodgy-technology/ionic-lifters-has-anyone-else-around-here-build-one/

For such low thrust devices, it certainly makes sense to turn them on their side and use them to power something aerodynamic, with wings and control surfaces, rather that straight vertical takeoff - as applies to all aircraft.

I'm still surprised that they've made something capable of lifting its own power source (presumably Lipo + inverter) - something that has certainly eluded vertical lifters (although one has managed to lift Orville the mouse).   I wonder what its flight duration is, I guess that with sufficient scaling, solar power could become feasible.

[MarkR42]

I'm very disappointed with the general lack of scepticism and accuracy of reporting.

The media I've seen generally talk about fancy applications such as manned aircraft, without considering any of the problems inherent in this system.

It's an interesting device, but as far as I can tell, it's extremely inefficient, generates a lot of ozone, and has a very poor thrust/weight.

I can't see how it can compete on efficiency or thrust with a simple electrically driven propeller, which we already have. There might be some niche applications (which have been discussed) but otherwise, it's just a curiosity.

Add that to the fact that the tech isn't particularly new, the researchers were probably just the first ones to build a working aircraft with it. Which is not surprising because it's so bad (see above).

[GeorgeOfTheJungle]

It's an interesting device, but as far as I can tell, it's extremely inefficient, generates a lot of ozone, and has a very poor thrust/weight.

Nah, 100kW buys you 5.4 full newtons of pure thrust, says in the other thread :-)

[Gyro]

It's an interesting device, but as far as I can tell, it's extremely inefficient, generates a lot of ozone, and has a very poor thrust/weight.

Nah, 100kW buys you 5.4 full newtons of pure thrust, says in the other thread :-)

No, that's for Vacuum Ion thrusters (Nasa) - not saying the 'lifter' technology they're demonstrating is anything approaching efficient, but it's orders of magnitude higher! 

EDIT: I indicated the currently demonstrated power/thrust range in my post above - looking at the 'plane' construction, it think it would be somewhere in the middle.

[dmills]

It is orders of magnitude higher because Isp is not something that matters for air breathing engines!

When you have to carry your own reaction mass, throwing it out the back quickly matters far more then the electrical power required to do so, where in an aero engine it is the power consumption per unit thrust (at whatever velocity is appropriate) that matters, not mass consumed per newton/second. The optimisation problem is very different.

Regards, Dan.

[GeorgeOfTheJungle]

Nah, 100kW buys you 5.4 full newtons of pure thrust, says in the other thread :-)

No, that's for Vacuum Ion thrusters (Nasa) - not saying the 'lifter' technology they're demonstrating is anything approaching efficient, but it's orders of magnitude higher! 

EDIT: I indicated the currently demonstrated power/thrust range in my post above - looking at the 'plane' construction, it think it would be somewhere in the middle.

Ok.

A rough estimate from existing lifter designs is anything from 50W for 0.1 Newtons thrust, to 300W for 2.5 Newtons.

1 kg (force) = 9.8 Newtons => you'd need 300[W]*(9.8[N/kg]/2.5[N]) = 1176 W/kg ? That's no too shabby!

( The other end of the scale: 50[W]*(9.8[N/kg]/0.1[N]) = 4900 W/kg )

[Domagoj T]

Ion thrusters for space have different requirements that atmospheric engines.
When it comes to space travel, pretty much everything boils down to mass, the less of it, the better.
Ion engines are good for space probes because they have insane specific impulse compared to chemical rockets, so if you can live with low thrust and long burn times, high power usage is more than offset by advantage that this high ISP brings to the equation.

[Berni]

Yes Ion engines in space and this "electrostatic fan" are two very different things. The ion engine is trying to shoot out ions as close to the speed of light as possible to maximize ISP for the limited fuel it has. This air operating ion engine does not care about ISP since it has all the air it wants around it. It just needs to grab and throw as much of it as possible.

These "electrostatic fans" do have the potential to be pretty efficient since while the voltage to run them in extremely high the current is very low. The problem they have is that they don't scale very well for large amounts of thrust. They become more powerful as you increase the voltage, but at some point the air arcs over. This means you have to move your ion producing wire farther away, but at the same time this makes the electric field gradient weaker so you don't get as much electrostatic force on your ion. At some point the voltages just become so ridiculously high that the dimensions of the thing become huge. Its also a safety concern running these exposed high voltage wires all over the plane.

The concept is certainly pretty cool but we are going to need some serious technological advances before we can manage to build an engine even remotely powerful enough for a drone.

[rfeecs]

Another longer video:

https://youtu.be/boB6qu5dcCw

[Vtile]

The only interpretation I can find: yet another MIT backslide.

"Lifters" have been known among high voltage enthusiasts for decades.  I don't see how any of this can be original and new; how did it get published?  What did they establish or refine?

I shouldn't be so negative.  Maybe it's a review of the literature on the subjects, and the demonstration is incidental to the paper?

Tim

My thoughts, put out. 

[GeorgeOfTheJungle]

A rough estimate from existing lifter designs is anything from 50W for 0.1 Newtons thrust, to 300W for 2.5 Newtons.

1 kg (force) = 9.8 Newtons => you'd need 300[W]*(9.8[N/kg]/2.5[N]) = 1176 W/kg ? That's no too shabby!

Let's do some more math:

1) A 5Ah 18650 weights ~50g
2) => 1kg of 18650s is 20 cells
3) 20*5Ah*3.7V = 370 Wh
4) => 60*370/1176 = 18.9 minutes

A 1kg ion-driven drone could fly for 18 minutes ? (I find it hard to believe)

[Berni]

Yeah i did say this has the potential to be pretty efficient since you are sort of directly accelerating air with an electric field.

The hard part is how do you build one of these electrostatic engines powerful enough to produce 1kg of thrust. (Without being the size of a car)

EDIT:
To put things into perspective this is the smallest ion lifter they managed to build to be powerful enough to carry one mouse as cargo:
http://jnaudin.free.fr/lifters/orville/index.htm

Tho the efficiency they got is not as high using 350W to produce over 180g of lift, but keeping 35kV contained can be tricky so a good deal of this might have also been leakage.

[GeorgeOfTheJungle]

Yeah i did say this has the potential to be pretty efficient since you are sort of directly accelerating air with an electric field.

The hard part is how do you build one of these electrostatic engines powerful enough to produce 1kg of thrust. (Without being the size of a car)

The pesky details... lol

EDIT:
To put things into perspective this is the smallest ion lifter they managed to build to be powerful enough to carry one mouse as cargo:
http://jnaudin.free.fr/lifters/orville/index.htm

Tho the efficiency they got is not as high using 350W to produce over 180g of lift, but keeping 35kV contained can be tricky so a good deal of this might have also been leakage.

That's not too bad, look: 350*1000/180 => 1944 W/kg ! But yeah, the payload is just a tiny fraction of the total weight, those pesky details ruin the party.