You are viewing a single comment's thread.

view the rest of the comments →

0
1

[–] alele-opathic 0 points 1 point (+1|-0) ago 

Sorry for the long post.

Drones are the least efficient mobility device we have available.

Do you mean in the “energy cost/productivity ratio” sense?

I mean in the mechanical physics sense, which translates into energy cost, and expands into other costs (sooner battery replacement from faster cycling, etc). I meant to put this into a 'physics redpill' post that I began when I first got here, but got so sidetracked delving into the politics that I got distracted and never finished it.

 

In short, the wing is the original 'overunity' device, allowing e.g. a 400 ton 747 to lift itself with just 24 tons of thrust (its wing producing 17 times as much lift as drag). Rotary wings (e.g. helicopters) are worse, since the inside part of the wing sees relatively little airflow, and most of the lift is produced on the outside of the blades, and then you have the quadcopters/etc, whose propellers are commonly not even wings at all (meaning lift:drag ratio is below 1) and requires the craft to produce thrust higher than the weight of the craft to even stay airborne. This is why the military, having had drones for decades, always used miniature planes for drones. The power density of batteries/motors simply wasn't high enough for them to lift their own weight directly.

The long story is a rabbit hole: in short, we don't know why planes fly. When Lord Kelvin + Newton + etc claimed heavier than air flight is impossible, they ran their calculations on flat plate. Since it should be physically impossible for lift to exceed drag, they did their calculations using flat plate (it should be the most efficient airfoil), and since lift can never exceed drag, they reasoned that heavier than air flight should be impossible. They were technically correct, but, in fact, wrong.

Drones without wings eliminate all of that benefit, which is why they have abysmal flight times (the heavy-lift drones have 20ish minute flight times with a payload) and terrible flight characteristics. They are simply all muscle that is wasted literally brute-forcing themselves into the air.

And this is before you consider the economies of scale of transporting additional packages at once.

0
0

[–] alele-opathic ago 

Hey @Tallest_Skil, just a reminder ping, as this conversation seemed like it would have been quite interesting. If you get the chance, I'd still like to know what you think!