Airborne wind generators

Factual Questions
1

In addition to mention of space-based solar power, I have also seen mention of airborne windmills for power generation. I am talking about the tethered generators which fly in the jet stream like a really big kite. Are these just pie-in-the-sky (heh) or might these become feasible in the foreseeable future?

Thanks,
Rob

2

I’ve read of these, too. Kites with propellers, sending electrical power down their line-cord strings. It sounds good to me - the wind is much better up there, and it’s pretty easy to haul them down for maintenance. Don’t know why they aren’t up there yet.