
New Electric Motor That’s Super Light and Powerful for Electric Airplanes - davidst
https://transportevolved.com/2016/07/08/siemens-showcases-brand-new-electric-motor-thats-super-light-super-powerful-and-perfect-for-electric-airplanes/
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swingbridge
A lighter engine certainly doesn't hurt, but it's really the batteries that
are an issue. The other item often overlooked on the battery front is that
most batteries hate the cold. Take your iPhone out on a 20F day and see how
long that 100% charge lasts! (Spoiler alert, likely a few minutes).

As you go up in the atmosphere things start to get really cold. Until the
weight and temperature issues with batteries can be address electrical
aviation will be mostly a concept on paper.

~~~
sandworm101
> As you go up in the atmosphere things start to get really cold.

Yes, but the air is also much much thinner. So it doesn't suck heat away
nearly as quickly as it might at ground level. So the batteries should retain
heat.

I don't see the energy-density math. Batteries in passenger planes would have
to last far longer than the flight duration, at least 30minutes more to
accommodate safety margins such as diversion to other landing sites. And a
battery-powered plane must suffer from the fact that it hauls around dead
batteries. A gas-powered plane gets lighter as it burns fuel. So, by my math,
an electric passenger plane would require an energy density at least four or
five times that of current battery tech. The motor isn't the issue.

~~~
soperj
I would assume a bunch of the battery usage would be from take off. You'd
think they could design a system like a rocket launch with a "staged" plane
launch, where the batteries used for take off would then be jettisoned to land
safely back at the airport for re-use.

~~~
sandworm101
A while ago I read a proposal by airbus for an electric airliner. They
speculated that batteries could be recharged on the way back down from
altitude. If you want to recover energy, you;ll need those empty batteries.

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kragen
You'd think that since the article is about how this motor is a new record in
power density (or rather specific power), it would include the specific power
in the article somewhere. You would be wrong, but it does include the
information needed to calculate it. The SP260D motor they're talking about has
a specific power of 260 kW / 50 kg = 5.2 kW/kg. It's not clear if this
includes the weight of the batteries or not.

The article says the usual motor for the Walter Extra 330L is 315 horsepower,
which is 234 kW. The "E" in the model number "330LE" apparently refers to the
electric version.

To contextualize, motor specific power is actually really important for
heavier-than-air flight. The reason Leonardo's helicopter designs wouldn't
work is a lack of specific power in the (human) motors he had in mind, more
than any aerodynamic reason. (Sufficiently high specific powers can overcome
even remarkably poor aerodynamics.) The Wright brothers' main innovations
were: a workable system for steering, and a motor with sufficiently high
specific power.

The bit about the motor's end shield seems to be describing topological
optimization, but the description of the process is somewhat ambiguous. It
would be nice to see a picture of the end shield and maybe information about
how it's made.

Maybe a less clueless, though even more information-scarce, article is
[http://www.flyingmag.com/extra-unveils-
electric-330le](http://www.flyingmag.com/extra-unveils-electric-330le)

Other commenters are pointing out that this won't work for long-distance
flight. The Flying article I linked above says it will actually only last
either 5 minutes or 15–20 minutes (it seems to contradict itself, but maybe I
just don't understand it.) So it's adequate for aerobatics only. But it should
be better at aerobatics than the standard engine was.

Further links from other comments:
[https://news.ycombinator.com/item?id=12060954](https://news.ycombinator.com/item?id=12060954)
[http://www.gizmag.com/siemens-world-record-electric-motor-
ai...](http://www.gizmag.com/siemens-world-record-electric-motor-
aircraft/37048/) [https://newshour.online/2016/07/04/world-record-electric-
mot...](https://newshour.online/2016/07/04/world-record-electric-motor-makes-
first-flight/)

~~~
VLM
Speaking of helicopters and specific power and weight and all that, it seems
an article of faith that eventually an electromotive tail fan will be lighter
than all equivalent reliability mechanical or pneumatic systems. I mean sooner
or later as magnet strengths and VFD voltages approach infinity and VFD and
motor mass approach zero, at some point the rube goldberg mechanics that make
the tail rotor spin will be replaced by a near weightless power cable and
electric motor.

You don't need a battery to spin a tail rotor... once the main disk stops
spinning there isn't much point in keeping the tail rotor spinning.

A hybrid helicopter is an interesting concept, rather than zero torque the
instant the engine dies and hope for good luck WRT autorotation technique,
even merely giving the pilot 15 extra seconds of battery thrust would probably
save some lives.

~~~
kragen
Pneumatic hoses are pretty light too, and pneumatic motors are usually a lot
lighter and more reliable than electric motors of the same power. But maybe
you're saying that this is merely a function of low voltages and weak
permanent magnets, and we can expect electric motors to get a lot lighter? I
guess that's possible; can you point me at some exemplary modern motors?

I tried to write a thing here about the physics of the situation — saturation
flux densities and layer-wound armatures and resistivities and dielectric
strengths and so on — but then I realized that I don't actually understand the
physics of electric motors well enough to say anything coherent. How are
electric motors increasing their specific powers — is it just by higher RPMs,
or is it a matter of more poles and/or better materials and geometries? What
are the limiting factors?

~~~
abecedarius
Drexler gets into electrostatic motor scaling in Nanosystems and presumably
his thesis. I have no idea about the kind of designs made today, though.

------
ars
This article has almost nothing about the actual motor in the title except
this:

"every component from previous motors was examined and optimized to lighten
this motor and improve efficiency. The end-shield for the motor, for example,
was analyzed using a software package that divided the component into over
100,000 elements, each of which was individually further stress-analyzed and
subject to iterative improvement loops. Eventually, the custom software spat
out a filigree structure that weighs 4.9kg instead of the 10.5kg from the
previous design."

The rest of the article is basically fluff with no info.

~~~
dbyte
Even this paragraph is just a general description of what could potentially be
a FEM analysis and some optimisation algorithm associated with that.
Interesting result on the other hand.

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ChuckMcM
Just penciling in the math that means a quad copter is pretty straight forward
with this motor. 200kg for a "megawatt" of thrust. Now all we need are
batteries that are 3x as power dense as the current best of class and you'll
be able to hop from home to the office in your 'quad'.

~~~
oconnore
Why would you use batteries? Fuel gets lighter as you use it, and the density
is already there. Automate maintenance so you can use turbines.

~~~
ianpurton
My guess would be electric might be simpler and easier to maintain and with
electric you can charge at home.

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usrusr
I applaud Siemens for venturing outside their comfort (profit?) zone instead
of just incrementally improving whatever they did for decades already (and did
not sell for having a bad quarter), but they are really overdoing milking this
little plane for publicity. An electric motor being lighter, per Watt, than an
ICE, who would have guessed.

That being said, a hybrid setup could well be worth it, even with the abysmal
specific energy density of real life batteries: keep just as much conventional
engine as needed for cruise flight only and have some form of electrical
assist for the few minutes of a flight that need more power than that. Battery
density isn't a problem at all when you don't need endurance.

~~~
phire
For a hybrid setup, regulations will likely require that both the conventional
engine and the electrical system to be powerful enough on their own to still
take off if the other system fails after V1.

Still, that's massive savings over the current twinjets, which require two
engines, both powerful enough to take off after a failure of the other at V1.

~~~
usrusr
Sounds reasonable. But in an unlikely best case scenario, the electric part
might somehow be certified for single engine reliability, capable of
everything except endurance. A wave of comparatively liberal cruise engine
development might then catch up with a few decades of combustion engine
refinement.

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Osiris30
Already discussed at
[https://news.ycombinator.com/item?id=12060954](https://news.ycombinator.com/item?id=12060954)
... Some commenters had more info on the engine on this thread.

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ptaipale
I wouldn't think even older electric motors wouldn't work well enough in
electric airplanes regarding weight and power? The weight of batteries is the
biggest problem.

~~~
SixSigma
Have an on board diesel generator

~~~
jkot
LOL. Technically some heavy trucks and engines, are powered by electric motor
with generator. Some of the biggest trucks and tanks were electric ;-)

[https://en.wikipedia.org/wiki/Diesel-
electric_transmission](https://en.wikipedia.org/wiki/Diesel-
electric_transmission)

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JoeAltmaier
I thought it was the battery, not the engine, that prevented long-distance
flight? For energy / kilogram, lithium batteries are around 200 while gasoline
is around 13,200.

~~~
gambiting
Yep - and as you use up fuel, your plane gets lighter, saving more fuel the
longer you fly. With batteries, you have to carry the same weight for the
duration of the flight. Which actually is a huge problem, because on most
airplanes maximum take-off weight is higher than maximum landing weight.

~~~
agumonkey
I have the stupidest idea. As energyless state fuel is released in the air,
just drop 'depleted' battery modules and have them collected.

~~~
patrickk
Another stupid idea: use aircraft catapults[1] to reduce the onboard energy
requirements. Takeoff seems to be the most energy demanding stage of the
flight.

Obviously a drawback is that existing airfields' or airports' runways would
have to be retrofitted, but if the fuel and maintenance savings were enough,
it might make sense.

[1] used on aircraft carriers:
[https://en.wikipedia.org/wiki/Aircraft_catapult](https://en.wikipedia.org/wiki/Aircraft_catapult)

~~~
marcosdumay
You just need to carry energy into the airplane, with coils for example. No
need for a catapult.

~~~
patrickk
The catapult is a proven technology for aircraft though, with decades of
development.

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tonmoy
Solar powered recon UAV with near unlimited flight time could be an
application

~~~
petra
Just combine some lighter-than-air structure with a UAV to achieve really
great energy efficiency , and put solar panels on it. It would probably be
possible in no-wind conditions to stay at the same point while charging the
batteries.

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userbinator
Nothing at all about reliability, which is going to be the biggest factor the
aerospace industry will be considering about this. You can sacrifice
reliability for _extreme_ power-to-weight ratio, as evidenced by things like
Top Fuel dragsters and even the electric motors in RC planes are optimised
more for power than longevity.

------
elmar
better articles

WORLD-RECORD ELECTRIC MOTOR MAKES FIRST FLIGHT

[https://newshour.online/2016/07/04/world-record-electric-
mot...](https://newshour.online/2016/07/04/world-record-electric-motor-makes-
first-flight/)

Siemens' world-record electric aircraft motor punches above its weight

[http://www.gizmag.com/siemens-world-record-electric-motor-
ai...](http://www.gizmag.com/siemens-world-record-electric-motor-
aircraft/37048/)

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saidajigumi
It seems that this motor's power-to-weight ratio advantage applies just as
well to ground vehicles. Are there reasons why that isn't the case? I.e. is
this approach somehow specific to heavier-than-air engines? (Also, speaking
not necessarily to using _this specific motor_ , but rather applying Siemens'
cited optimization techniques for ground applications.)

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oska
The most recent episode of Fully Charged [1] looked at a 100% electric racing
plane currently in development that uses two electric motors to drive two
counter rotating propellers at the front of the aircraft.

[1]
[https://www.youtube.com/watch?v=Xe1g1JrRRkY](https://www.youtube.com/watch?v=Xe1g1JrRRkY)

~~~
elmar
the use case for this aircraft is to fly 20 minutes maximum so current battery
technology power to weight is enough.

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Pxtl
This should be interesting for solar-powered remote-controlled aircraft, where
battery weight is less of a concern.

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emilong
To what size of aircraft can a motor like this scale? Or perhaps more
importantly, motor + batteries? To put it another way, is this technology
likely to scale to an aircraft transporting 4 or more people anytime soon?

~~~
ianpurton
Airbus are planning a 100 seater aircraft by around 2030.

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topbanana
It's all about the batteries. That's what's holding us back

~~~
intrasight
Electric engines doesn't necessarily mean batteries. Consider micro-
turbogenerators.
[http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/...](http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/3792/Camacho_duke_0066N_10953.pdf)
As others mentioned, fuel has the advantage of getting lighter over travel
time. Also, electric motor planes should be wrapped with solar cells.

~~~
JoeAltmaier
Solar cells add weight. As an energy source its hard to quantify them since
they never run out, and weight the same the whole trip. Maybe more like
batteries. Anyway energy/kilo is probably pretty bad. So for any finite trip,
leave off the solar cells and use gasoline.

~~~
mikeash
It's easy to quantify solar cells on an airplane, just look at power consumed
by propulsion and compare to power generated by the cells. The result is that
the power generated is pretty much useless and doesn't even justify the weight
of the solar cells, unless you design a plane to be _extremely_ light and with
nearly no payload, a la Solar Impulse.

Solar could be good for drones that stay almost permanently airborne and just
need to carry some electronics, but it's pretty much useless for
transportation. If you must use electricity there, you'd want to use batteries
on the plane, and keep your solar panels on the ground.

~~~
Pxtl
But for the specific case you're discarding here - a solar-powered camera
drone - doesn't this new motor provide a serious improvement?

Low-cost solar-powered drones could be a wonderful tool for aerial cameras.

~~~
mikeash
I'm sure it'll help, but the fundamental problem with solar powered aircraft
is that one pound of solar panel can lift barely more than one pound. That
means saving weight on the motor can cut out a lot of solar panels, of course,
but it also means you still need a ton of solar panels just to lift the
structure of the aircraft and the payload.

I don't think we'll see cheap solar drones anytime soon. Current solar
aircraft need to be gigantic and fly extremely slowly. Small drones typically
want to be quadcopters, which are inherently inefficient, but have other nice
properties. If you want a solar-powered small drone, make a stationary solar
array, give the drone a swappable battery pack, and charge batteries with the
stationary array while different batteries are powering the drone.

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peter303
As we approach the 200th anniversary of Faraday's 1821 invention of the
electric motor, I am impressed we are wringing out improvements.

