Why can’t electric motors be used in aviation? Is it a problem with batteries, torque, or what? From what I’m aware motors at high torque are expensive and need a massive footprint, than a high rpm low torque motor. Is the issue the weight and size of a motor to lift 500,000 pounds off the ground? We have motors right now that can spin a turbo fan at a high speed and compute a comparable thrust, but is that thrust under load a different story? Is the energy required way too much for a realistic battery size?
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3$\begingroup$ It's not the motor, it's the weight of the batteries. There are some electric aircraft, but their endurance is quite limited, or they have impractical for general use wingspans &c: en.wikipedia.org/wiki/Electric_aircraft $\endgroup$– jamesqfCommented May 25, 2019 at 3:22
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$\begingroup$ @jamesqf that's good enough to be an answer. You should maybe expand it a bit and post it. $\endgroup$– John KCommented May 25, 2019 at 4:02
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$\begingroup$ Electric power does not need to be delivered by batteries, fuel cells or a generator work as well. $\endgroup$– KoyovisCommented May 25, 2019 at 5:49
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$\begingroup$ @John K: There are already several questions with answers saying essentially the same thing. $\endgroup$– jamesqfCommented May 25, 2019 at 18:03
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$\begingroup$ @Koyovis: Fuel cells need to carry fuel, and AFAIK are fairly rate-limited. Using a generator to produce electricity to run an electric motor that drives your propellor would be stupidly inefficient. Though one might consider solar power, as with the Solar Impulse en.wikipedia.org/wiki/Solar_Impulse to be a sort of generator. But again, it's hardly suited to practical uses. $\endgroup$– jamesqfCommented May 25, 2019 at 18:08
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Electric motors can be and are used in aviation - there's hundreds of them on any airliner you fly on.
As for using them for main propulsion, let's first look at the power/weight ratios. The highest number for Tesla's car motors is 8.5 kW/kg. The electric-aircraft-specific Emrax 268 delivers about 12 kW/kg.
In comparison, the Trent XWB delivers 430 kN of thrust at 300m/s flow rate, which equates to 64.5 MW of power, in a 7,550 kg package - a power/weight ratio of 8.5 kW/kg. However this isn't apples to oranges: this ratio is for the whole package, engine and fan, and measures useful output, like wheel power for a car.
In short, turbine engines are still lighter than electric motors, but the difference is not dramatic. Where all-electric powerplants fail to stack up is range. I've elaborated on it in response to another question - Are there any hybrid electric planes?. The short version is that the maximum possible range of an electric aircraft is 10 nmi for every % of its weight dedicated to the battery. This limits the range of electric aircraft to 300-450 nmi, if sticking with the fuel fractions of known airliners.
But there are aviation applications where this is enough. The most important non-renewable resource consumed by modern aviation - the supply of 1960s Cessnas and Pipers, without which no one could afford to become a pilot - will not last forever. Should authorities permit it, mass-produced Tesla powerplants could power trainers and GA planes at a fraction of the ownership cost of a certified avgas engine.
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$\begingroup$ Emrax 268 delivers up to 10kW/kg emrax.com/products/emrax-268 $\endgroup$ Commented Dec 20, 2019 at 11:05
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$\begingroup$ @jamesqf, magnix just powered the first commercial plane w/electric, a little bigger motor, magni500 560kW on a DHC-2Beaver $\endgroup$– Ian WCommented Dec 21, 2019 at 11:16