In previous posts, I had mentioned the catenary sag effect as a factor that could limit scalability by the number of stacked rotors and their mass, due to the mass causing the middle of the stacked rotors to bend toward the ground, with the lifter kite at the top alone not being enough to counter this effect when the set is very long.
Moreover, the lifter kite should also allow the whole assembly to lift, but, for long sets, this seems difficult due to the tilting effect of the horizontal wind force, even though lift aggregated with that of the lifter kite is observed.
It seems that ballutes (torus) inflated with helium or hydrogen could help overcome these difficulties and lead to larger dimensions, both in the diameter of the rotors whose blades could be twisted, and in length by the number of rotors.
But then I see another problem that might not be one. How will the whole system behave, knowing that the rotors will be subjected to winds of different directions and intensities? Will the rotations self-regulate, at least up to a certain threshold of irreversible torsion?
This problem can also be posed (and maybe it has been) for long stacked Daisy.
Perhaps it would be possible to calculate this threshold of irreversible twisting with respect to different parameters (diameter, number of rotors…), using the appropriate methods: Rotary Kite Turbine Development Roderick Read, Windswept and Interesting Ltd - AWEC 2021 - AWESystems Forum?
Another interesting point is the possibility of using hydrogen, much less expensive and rare than helium, because there is no relative movement within the set of rotors that rotate as a single piece, except for takeoff and landing where the rotors are superimposed by their respective ballutes. Info on hydrogen and (tethered) hydrogen aerostats - Engineering / Lifters / Pilot kites - AWESystems Forum.