It’s hard to offer anything beyond generalities and theory because it’s so early in the research process. Of course, we can start with the OP’s link:
- Use the fact that electric motors are granular and distribute many of them across the wing. This improves low-speed lift and allows a relatively shorter wing.
- Also put motors on the wingtips. These can be sized for cruise, due to the extra power available from the distributed motors. They reduce losses from wingtip vortices.
- Make the whole thing out of composites.
One thing I’d like to see is the use of the cells as structural material. I don’t know exactly what form this would take–that’s a research program in and of itself. But one possibility would be to form the cells into long rods that could stiffen the wings or fuselage. Cells come in many form factors, one of them cylindrical–and cylinders are pretty good structural components. One could put a number of individual cells into each unit.
I was serious before when I mentioned sodium power cabling. It’s not completely unheard of; in fact there’s a paper on the subject from 1967. It is significantly lighter than aluminum.
Superconductors? It may happen. The equipment is liable to be expensive and heavy, but the tradeoffs here need to be explored. It may make a good pairing with a cryogenic hydrogen fuel cell craft (use the hydrogen to cool the superconductors).
Overall, there’s likely to be a greater trend toward “unobtainium” (i.e., expensive but high performance materials). Carbon fiber everywhere; in the seats, the toilet bowl, wherever. Airplanes never want to be heavier than necessary, but in the end there is always a point where they can save one more kilogram for X dollars, and they have to decide whether it’s a worthwhile tradeoff. For electric planes, the tradeoff is completely different: the “fuel” barely costs anything, but that kilogram could have gone to batteries. Does lightening the plane open up a new route?
I’m interested in the altitude/efficiency tradeoff. Electric motors don’t need air, so it should be possible to fly higher than traditional craft. Does it make sense to go to 50k, 60k, 70k, 80k feet?
The speed/efficiency tradeoff is also interesting. My intuition tells me one wants to go as slowly as possible (due to the v^2 drag term). But induced drag goes down as the speed goes up, so it might end up being better to go fast, especially if one can reduce parasitic drag (like with the X-57’s short wing). If parasitic drag is the dominant factor, what can be done to reduce that–narrow but long fuselages, for instance? Low friction coatings?
Generally speaking, there’s a many dimensional design space to explore with entirely new tradeoffs. Aircraft *already *come in a huge variety; it would be absurd to expect that electric planes somehow hit exactly the same designs. And in any case, the overall technology level of aircraft is progressing (though slowly).
Incidentally, NASA is hoping to achieve a five-fold efficiency increase over comparable craft with the X-57. We aren’t talking small factors here. And that’s just one fairly narrow research program; many others are also working on the problem. I’m looking forward to what others come up with.