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Pressurized cabins are going to be essential for electric flight to have any kind of reasonable speed (and range). It shows that the most impressive electric a

Pressurized cabins are going to be essential for electric flight to have any kind of reasonable speed (and range). It shows that the most impressive electric aircraft specs are for the pressurized Eviation Alice (1000km, minus margin for contingency, and 250 knots cruise). If you stay low enough to not require pressurization, then you have to compromise the lift to drag in order to have a decent cruise speed or you have to tolerate a really low cruise speed. Altitude is essential. Bite the bullet and build a pressurized cabin so we can get on with replacing fossil fuel aviation with full electric. https://www.eviation.co/alice/ https://www.eviation.co/alice/ Doesn't have to be above the Armstrong Limit, but it sure does help to be above 10,000 feet. Eventually we'll have supersonic electric aircraft. To have sufficient efficiency, they'll need to be at or above the Armstrong Limit, like Concorde. (And perhaps higher, like the 96,000 feet record holder for horizontal powered flight, NASA's Helios... which just happens to be electrically powered. https://en.wikipedia.org/wiki/Helios_Prototype https://en.wikipedia.org/wiki/Helios_Prototype .) EDIT: High altitude enables you to use an extremely efficient airframe with sailplane-like lift to drag but STILL achieve high cruise speeds. For instance, the Perlan II glider actually has no engine and is able to soar higher than any towplane, above 76,000 ft where it flies at about 250 knots (actual airspeed). Without any engine at all. https://www.youtube.com/watch?v=NnpE5xS1g80 https://www.youtube.com/watch?v=NnpE5xS1g80 And here's a solar electric aircraft aiming for similar goals: https://www.solarstratos.com/en/challenge/ https://www.solarstratos.com/en/challenge/

semi-extrinsic 7y ago
All passenger jets have pressurized cabins, but they are working at lower pressure differentials than what you need above 60k feet, and they sometimes fail, with oxygen masks being the fail-safe. If you go above 60k, and the plane experiences a rapid loss of cabin pressure, you have 60 seconds to restore cabin pressure before the passengers start dying. So the failsafe system will have to be massive. That increase in weight and complexity isn't worth the efficiency gains. You mention Concorde, and indeed it had a very substantial failsafe system even though it only touched the lower end of the limit. Concorde had really small windows, so even with two windows gone it took some time to equalize pressure. The pilots had positive pressure oxygen masks, and the plane had the ability to drop altitude immensely fast in an emergency.
- Robotbeat 7y ago
  Concorde flew above 60,000ft. You may just have to demonstrate loss of cabin pressure is rare enough that it's worth doing.

semi-extrinsic 7y ago

All passenger jets have pressurized cabins, but they are working at lower pressure differentials than what you need above 60k feet, and they sometimes fail, with oxygen masks being the fail-safe. If you go above 60k, and the plane experiences a rapid loss of cabin pressure, you have 60 seconds to restore cabin pressure before the passengers start dying. So the failsafe system will have to be massive. That increase in weight and complexity isn't worth the efficiency gains. You mention Concorde, and indeed it had a very substantial failsafe system even though it only touched the lower end of the limit. Concorde had really small windows, so even with two windows gone it took some time to equalize pressure. The pilots had positive pressure oxygen masks, and the plane had the ability to drop altitude immensely fast in an emergency.

Robotbeat 7y ago
Concorde flew above 60,000ft. You may just have to demonstrate loss of cabin pressure is rare enough that it's worth doing.