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I don't have such a sign, but 100 passengers is still smaller than what current jets do, so it might be possible. It would be a radically more efficient design than what we currently have, though. Before we can even think of long-range flights, let's consider mid-range: A 737-300 has a range of ca. 4000km from 20,000l of fuel. But that's not flying with full tanks all the time. It has a payload capacity of 17t (on top of passengers, I think) and carries up to 149 passengers. If we cut the payload to 10t and passengers to 100, our "comparable" electric plane has 10t free payload for batteries (3t for the 50 passengers and 7t from the reduced payload). If we, generously, assume that we can add another 10t as "structural batteries" (basically, building the airframe out of batteries, because, why not, but also smaller and lighter engines), we end up with maybe a total capacity of 40t for our batteries (assuming 1kg/l for the jet fuel). We need the energy for a mid-range flight, say 1000km. That would be about 5000l of kerosene, in a 737 (not completely true due to weight loss during the flight). Fortunately, our electric propulsion is probably much more efficient (thermally) than a turbojet, so we might only need about 2/3 of the same energy. That puts us, very roughly, to the equivalent of 3.333l of kerosene, or about 86GJ. Hence our battery would have to offer 3.6MJ/kg. This is inside the theoretical realm of a zinc-air battery. So with this very rough calculation it does not seem to be impossible to achieve mid-range battery electric flight. And this usually means it is going to happen whenever it is economically sensible. For long-range flight, though, we would need even better batteries. Like, at least 4 times better. This is not on the horizon, currently. |