Future forms of propulsion

I hope this thread to be a place where we can talk about things from solid state batteries, fuel cells, capacitors, engines, motors, and every other future form of paramotor propulsion that we can think of.

I have been thinking about flywheel propulsion for a long time. Back in the 50´s they where used in buses and gave a 6 km range with top speeds of over 50 kmh and more recently they have been looked at as a way of clean and cheap energy storage. I have been thinking of using them to power a paramotor so I decided to dig in a bit more. Currently the world record for the fastest flywheel surface speed is just over 3100 mph so i will pretend that in the future we could build an air worthy flywheel that could handle this. Plugging some numbers into a fancy online calculator I was surprised to see that if you could spin two counter rotating(cancels net gyroscopic effect) 15 pound, 12 inch diameter cylinders/pancakes at 84k rpm you could store nearly 1.7 kwh energy in it. Even better, if you could design the same weight and diameter flywheels into rings, you could get closer to 3.4 kwh. To top it all of you could charge it as fast as the motor/generator in it could handle which could be as little as 4 minutes(25 kw motor w/ 1.6 kwh flywheel), it could handle nearly indefinite charge and discharge cycles, would give no voltage sag, and it could actually be more efficient than a battery.

I would defiantly put this into the future category as we have not developed motors/generators that operate at the required power and rpms while maintaining a reasonable weight, The flywheels would instantly shatter going around corners due to the enormous gyroscopic effect felt by the flywheels combined with the thousands of Gś trying to pull them apart, and finally these flywheels need magnetic bearings which I don´t believe have been properly developed for this scale and this much gyroscopic force.

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Flywheels are heavy, the heavier the better, therefore not good for flying (can be done but barely, with flywheel ring around propeller)

Hydrogen fuel cells are very promising and already used in airplanes and drones. Fuel cells have no moving parts and are very reliable. “hydrogen is about one-third of the weight of kerosene jet-fuel for the same amount of energy” but takes more volume, something that is no problem on huge paraglider.

Personally, I would love to see a paraglider or at least a motorized hang glider made of flexible solar panel fabric, we may also see them “soon” on sailboat sails.

It has already been proven by “unlimited range” solar planes, e.g.

A 25 square meter wing could produce 150x25 = 3750 Watts of electricity, which seems to be just enough for sustained flight (albeit a small battery would still be needed for take off).

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