Sound?
They could put playing cards in the spokes, no?
As I move from enormous two-terminal "dry cells" (approximately 3" diameter, 10" long) in 1940-1950:
As well as 22-1/2 and 67-1/2 volt "B" batteries for portable tube-operated radios, I am constantly amazed at the progress in energy density that has been made.
The thought of a modern drone flying up and down the California coast for at least 15 minutes to observe erosion boggles my mind, especially considering the drain on those motors and the distances involved. Where did they squeeze in all them extra electrons?
I remember my brother's RC plane having only an escapement rudder control, with the escapement powered by a twisted rubber band. One pulse, full left. Two pulses full left and return to neutral. Three pulses, left, neutral, right turn. Four pulses, left, neutral, right, neutral.
All at 27.255 MHz
Today? Proportional control on multiple channels way high up there in the spectrum is the norm.
So. You've seen the future. But keep today in your memory banks.
Terry