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Comment by Mvandenbergh | Hacker News Reader

Interesting. Obviously this is challenging from a power and energy density point of view but I suspect the play is likely to be in being able to land planes at airports very close in to major cities where noise and pollution constraints dominate. If you have a plane that you're allowed to land 300 times a year at midnight at a field where you'd only be allowed to land at 50 times a year before 10pm with a conventionally powered plane you might be able to stake out a commercially viable niche.

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> I suspect the play is likely to be in being able to land planes at airports very close in to major cities where noise and pollution constraints dominate.

Midnight arrival at the destination isn't the problem. It's 6am departure from whoever your vacation house that's the pain point for people who are rich enough to be chartering jets and helicopters.

With an electric jet you can depart from Long Island or Cape Cod in time to arrive at your office on Wall Street for that Monday morning video conference with your business partners in Zurich and do so without annoying your neighbors.

With a conventional jet/turboprop/helicopter you're limited to about once or twice a month before your neighbors get annoyed with the early morning noise and sick the local bylaw Stasi on you. (This is the means by which people in these sorts of communities feud over minor inconveniences. If your constantly annoying people by chartering a jet at 5am they'll complain about the unsightliness of the sailboat under a carport in your driveway or something.)

An electric jet will be by no means quiet (gotta create thrust somehow) but an electric jet can be substantially quieter than a petroleum fueled jet (and noise reduction appears to be a quality they're specifically designing for). Being able to have the travel time of a jet but no more noise than a turboprop would probably a big enough selling point for a few charter companies to add a few to the fleet.

I used to work at one of these sorts of airports, early morning departures is the biggest pain point a quieter jet solves for the kind of people chartering jets (you can't just roar out of there at 5am every Monday without pissing people off).

The amount of air you need to move to create the thrust is not silent at all. Whether it is all electric or gas turbine it's going to be noisy.

So far, noise level seems to be a repeating argument in favour of electric planes, so I suspect it's still much less noisy

Electric is quieter than gas turbine. That I agree. But quiet enough to meet residential quiet time requirements is still up for debate. The quietest jackhammer in the world still can't run at night.

Hopefully these planes are some sort of VTOL and can descend within the confines of the airport property and zone. Current planes line up over residential neighborhoods with the homes closest to the runway getting the worst of the noise.

Its like how about somewhere around 30 mph cars make more noise from going through the air than their engines.

Tyre noise sounds like the more likely source of car noise, at least that's how I previously heard this statement being made.

Cars don't derive their propulsion by pushing air. Airboats are a closer comparison. They normally are powered by a V8 and are extremely loud. Not just from the unmuffled engine but also from the big ass fan that's attached to it.

Yes, however a large chunk of that is created by the flaps. If you have shape memory flaps, you can reduce noise by up to 40% on takeoff and landing. I know one company has already proven this technology on some Gulfstreams for qualification.

I believe the big difference is that electric engines are wildly more reliable than piston engines. That allows less maintenance and shorter turnaround times, so it spends more time in the air than turboprops can.

Turboprops don't use piston engines.

Turbines are not very low-maintenance, too.

At least, electric motors are likely lower maintenance than turbines.

That's probably true, but I don't think we have much experience with electric motors operating in high altitude at the power levels required by planes. It'll be some time before we have as good an understanding as we have with jet engines, turboprops and piston engines. Remember these engines will cycle through extreme temperature changes every day of their active lives.

Yes, they will be quite hot, just below the Curie point of the magnets, during flights, especially during take-offs, and ambient temperature when on land (which can easily be freezing at winter time).

I wonder how much different it's from terrestrial electric motors that are not constantly powered. They don't have the weight limitations, though.

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