> 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.