Another interesting idea in this domain is to use wind power rather than solar power. Wind gradients can be harnessed through dynamic soaring although this can

Another interesting idea in this domain is to use wind power rather than solar power. Wind gradients can be harnessed through dynamic soaring although this can be a bit limiting. One way we might get around this is by flying two airplanes connected by a long tether.[0][1] One airplane flying at a different altitude where the wind is significantly different can be used like a kite sail to pull the other airplane. Although it has been shown to be a pretty nasty control problem at least for a human[2]. [0]https://www.nasa.gov/feature/flight-demonstration-of-novel-atmospheric-satellite-concept https://www.nasa.gov/feature/flight-demonstration-of-novel-a... [1]https://www.nasa.gov/sites/default/files/atoms/files/14-2015_phase_i_william_englom_virtual_flight_demostration_stratospheric_dual_aircraft_platform.pdf https://www.nasa.gov/sites/default/files/atoms/files/14-2015... [2]https://arc.aiaa.org/doi/10.2514/6.2018-1492 https://arc.aiaa.org/doi/10.2514/6.2018-1492