If you’d not heard about Alphabet’s “flying power kites” project, it’s an interesting concept. Tethered kites, flying big vertical circles, extracting power, and pulling down energy. They can also fly on their own for the purposes of takeoff, landing, and presumably emergency “cable broke” sort of stuff.
The project is ended, but they’ve released a rather impressive set of documents involving what they learned.
Worth poking through, if you’re interested in flying things and power production!
Wow! They’re putting everything into Public Domain, including these big 3 things
Makani’s entire avionics, flight controls, and simulation code repository
Flight data logs for every crosswind flight of the M600
A non-assertion pledge for the free use of Makani’s worldwide patent portfolio
That’s huge, and even if nobody else takes it and works towards the same thing in the future, I’d be willing to be large parts of it can be re-used for anyone with an idea for a kite or towed based system, even if it doesn’t have anything to do with generating power. Especially that flight control and avionics, and free-use for the patents.