Comment by masklinn | Hacker News Reader

Comment by masklinn | Hacker News Reader

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> I'm not sure it's ignoring everything - as this article states, electric planes exist today

Prop toys exist, not "future of aviation" anything. Props being an other issue, electric planes means no turbofans.

> Batteries are also improving

Batteries are not improving at a rate which would increase their specific energy by 2 orders of magnitude (the difference between the specific energy of the best batteries available today and bog-standard jet fuel) in any sort of interesting timescale. And that's before considering environmental issues, most batteries don't appreciates temperatures of -20C and below.

> thanks to Musk

That's a joke right? Tesla's battery innovations are related to manufacturing efficiency and structural sharing.

> So whilst far away, it's an extrapolation from our current position.

It's not extrapolation it's daydreaming based on what is basically magical thinking. It's less of an extrapolation than dyson spheres are.

> Nuclear planes don't exist today in any form

Nuclear planes were demonstrably feasible (if not necessarily smart) in the 60s: https://en.wikipedia.org/wiki/Tupolev_Tu-95LAL

The original supposition was that electric planes are the future - albeit a future very far way - because electric means no oxygen concerns, which means higher altitude, which increases efficiency and / or speed.

Now, electric doesn't mean battery. Fuel cells, solar, or even hybrid might all play a part. I believe a large proportion of energy consumption is during takeoff - what if you could draw take off power needs from the airfield rather than from the aircraft? What about hybrid - use gas to get to 30,000 feet, then turn on electric to go higher than that? Yes battery energy density is miles away currently, but if we avoid batteries in part, and improve them too, where might things be in 50 years time? The point is we are on the journey with electric planes, and the goal is a good one for reasons stated. Major problems to overcome - absolutely, but this is not a short or medium term prediction. But 'Magical thinking' required, more so than Dyson spheres? That's harsh.

I think Musk said he'd like this to be a far future project for him. He said he's driven by not wanting to go backwards - how space travel was worse than the 60s, as is air travel (no supersonic public aircraft any more). Electric planes - if possible - would be the solution to faster air travel. With Tesla and SpaceX under his belt, he'd certainly got the necessary chops to tackle it.

How is a turbofan/turboprop engine going to work in the thin air at these high altitudes? True jet engines work because of the combustion of jetfuel, but those are not really used much...

> The original supposition was that electric planes are the future - albeit a future very far way - because electric means no oxygen concerns, which means higher altitude

But higher altitude means lower air density which means your turboprops windmill into nothingness and have no way to propel the plane forward (even ignoring the issue of staying up in the air at all, existing airliners already fly quite close to the limits of their flight envelopes in normal conditions).

> What about hybrid - use gas to get to 30,000 feet, then turn on electric to go higher than that?

And where would you get the energy to do that in-flight? Certainly not solar, Helios already had a larger wingspan than a 747-8.

> Major problems to overcome - absolutely, but this is not a short or medium term prediction.

Neither are dyson spheres, and at least we've got some idea about how to handle those.

> But 'Magical thinking' required, more so than Dyson spheres? That's harsh.

Is it now?

> no supersonic public aircraft any more

There is no supersonic "public" aircraft because people have decided it wasn't worth the cost and have gravitated towards cheap high-density flying instead, it's not like we're flying any less than in the 60s or less far (a 777LR can go halfway around the globe without stopping) so the comparison to space travel is bonkers.

> Electric planes - if possible - would be the solution to faster air travel.

That doesn't make a lick of sense, electric engines are the slowest thing you can find in the sky. The only way "electric planes" would be faster than turbojets — let alone ramjets or rocket engines — is for the plane itself to be a ballistic component launched by a gigantic railgun, and then — assuming you manage to build the thing in the first place — your passengers are literally paste on takeoff as they eat a few hundred Gs.

"That's a joke right? Tesla's battery innovations are related to manufacturing efficiency and structural sharing"

That's exactly what brings costs down: economies of scale via efficient mass production. Whether we're talking about dramatically boosting the electric car market, or the giga factory.

Dyson spheres? Now who's exaggerating. Electric airplanes already exist, and will continue to improve for decades to come. Dyson spheres do not exist, and are not on the horizon.

> That's exactly what brings costs down

The problem of batteries on airliners is not cost, it's that they don't store enough energy per mass. Even if your batteries are free, when your plane can't take off because its mass has increased >10 fold there's very little point, you're left with an expensive bus too wide to take roads.

> Dyson spheres? Now who's exaggerating.

Same as before.

> Electric airplanes already exist, and will continue to improve for decades to come.

The original assertion is that they're the future of air travel, not the future of small-scale hobbyists.

> Dyson spheres do not exist, and are not on the horizon.

Both of which apply equally to electric airliners. Electric airliners require a literal technological revolution, so do dyson spheres.

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