These ram air kites by Skysails power flying in a figure eight circuit can develop power and also work as ship propulsion. Ideas like this have probably been toyed by many, it’s nice to see some execution. The biggest current product is 320 square meters and produces something equivalent to 2 MW of propulsion.
A flexible structure might be easy to store and the absolute lift is probably much more important than lift to drag at these low vessel speeds. I still wonder what high speed high aspect ratio glider style vehicles (tailed or tailles) could do in these applications. Control surfaces and all. Since lift is proportional to square of velocity.
And wouldn’t flying a circle or flattened ellipse or oval be more aerodynamically efficient with less tight turns and produce gentler load changes? Maybe there’s symmetry problems if you always go in a particular direction at higher altitude where the wind speed is higher. Or maybe the pull direction varies more.
The figure eight is simply to prevent twisting up the lines. With a simple two-line controlled kite, all the hardware and controls are on the ground, and the kite can be replaced cheaply if damaged or destroyed. Doing figure eights prevents the lines from sliding against each other, preventing damage.
Ah! Shows my lack of experience in kite flying very well…
I don’t see any control lines, so how is the kite manoeuvred?