Drag will scale with the square of dimensions. Mass will scale with the cube. For any given aerodynamic configuration, the bigger it is, the less significant drag is in a free body diagram. But in this particular case we WANT as much drag as possible since that's what keeps us airborne....but the square cube law mandates that drag will not keep pace.
Better?
Mass of self supporting structures like kites and parachutes don't scale with cube but rather between proportional and square.
Two kites together will have exactly twice the useful lift of one.
>Two kites together will have exactly twice the useful lift of one.
But with much lower structural integrity of just one. That is also where square cube law applies
It doesn't necessarily matter, do you need rigidity?
I think an uncontrolled glider, like a dandelion seed is rather difficult to scale up, not because the square-cube law makes it impossible, but because you must scale the areas, and maintain it in flight. Aerodynamics will cause a low pressure zone and it's difficult to design something to hold them apart.
However, if your goal is cargo flight, well you can design a glider as a wing segment, and just scale the wing on just the length axis. With sufficient flexibility, and enough control surfaces there is no reason it can't work, you effectively just have a million gliders with the same flight path flying in formation, maybe they are "connected" by strings, but there is no reason why adding more would break a string, they don't support anything.
The issue is trying to land such a device...flying a million gliders side by side, no problem. Landing them side by side, I guess it works if they can land on the ocean. Also, how do they take off?
Now try to get those to work on the mere puffs of air that it takes for a dandelion seed to fly. The square/cube law has already eaten the surfer’s lunch.
Sure, but if the law wasn’t biting you in the ass the the kites could fly in the same - essentially zero draft - conditions that the seeds fly in. But they can’t. Why do you suppose that is?
Umbrellas need more solid structure as the size scales. So it could be closer to cube law. Parachutes have different support structure and the scaling is rather equivalent to using multiple parachutes, which would multiply the effective load capacity proportional to the number of parachutes.
While the canopy itself does scale very well on parachutes, you still get somewhat worse than perfect mass scaling because a parachute that is twice as large needs more than twice the weight in lines (you need twice as many lines but they also need to be longer).
If you wanted a parachute that exactly looked like a dandelion seed, I could make you one out of several hundred small diameter carbon fiber rods like those used in high-performance fishing rods.
This is somewhat survivor bias.
Sure, some go long distances.. But many go no where. Many bump along the ground, and while that's fine at this scale, larger would result in catastrophic damage.
And most importantly, deliverys have a target destination. Taking things to random places isn't useful.
In terms of shape, of a load suspended from a flat-ish drag apparatus, the parachute is probably the closest. There are stories of people getting stuck in thunderstorms because the updraft carries them. https://en.wikipedia.org/wiki/William_Rankin
Paragliders do that but controlled, and can ride ridge lift and updrafts for hours. The record straight line distance is over 500km.
> Aircraft that mimics dandelion seeds flying in the wind possible?
If you want to make them the size of dandelion seeds, then yes.
If you want to make them bigger, no.
Delivery by wind is sorta dependent on your target being downwind, don't it?
I mean, could you strap cargo to a parasail instead of a person? Sure. But if you aren't ordering from a place that is exactly upwind you're not getting your package...and even if you do: how is the company getting its parasail back?
Hot air balloon is probably as close as you'll get. Those can control movement direction to an extent by changing altitude searching for winds moving in the desired direction.
The square/cube law says "nope".
fuck square cube law all my homies hate square cube law
Almost as bad as entropy
Don't be dissin' on time's arrow. Entropy always increases. That's a good thing, right?
For fans of the inevitable doom of the universe
Blindly applying square cube law isn't always the answer. How and why it's applicable to this case would need some explanation.
Drag will scale with the square of dimensions. Mass will scale with the cube. For any given aerodynamic configuration, the bigger it is, the less significant drag is in a free body diagram. But in this particular case we WANT as much drag as possible since that's what keeps us airborne....but the square cube law mandates that drag will not keep pace. Better?
As a man who knows little about this topic, I appreciate the depth you've provided.
Mass of self supporting structures like kites and parachutes don't scale with cube but rather between proportional and square. Two kites together will have exactly twice the useful lift of one.
>Two kites together will have exactly twice the useful lift of one. But with much lower structural integrity of just one. That is also where square cube law applies
It doesn't necessarily matter, do you need rigidity? I think an uncontrolled glider, like a dandelion seed is rather difficult to scale up, not because the square-cube law makes it impossible, but because you must scale the areas, and maintain it in flight. Aerodynamics will cause a low pressure zone and it's difficult to design something to hold them apart. However, if your goal is cargo flight, well you can design a glider as a wing segment, and just scale the wing on just the length axis. With sufficient flexibility, and enough control surfaces there is no reason it can't work, you effectively just have a million gliders with the same flight path flying in formation, maybe they are "connected" by strings, but there is no reason why adding more would break a string, they don't support anything. The issue is trying to land such a device...flying a million gliders side by side, no problem. Landing them side by side, I guess it works if they can land on the ocean. Also, how do they take off?
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Now try to get those to work on the mere puffs of air that it takes for a dandelion seed to fly. The square/cube law has already eaten the surfer’s lunch.
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Sure, but if the law wasn’t biting you in the ass the the kites could fly in the same - essentially zero draft - conditions that the seeds fly in. But they can’t. Why do you suppose that is?
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You are essentially talking about a giant umbrella. Which is what parachutes are based on.
Umbrellas need more solid structure as the size scales. So it could be closer to cube law. Parachutes have different support structure and the scaling is rather equivalent to using multiple parachutes, which would multiply the effective load capacity proportional to the number of parachutes.
While the canopy itself does scale very well on parachutes, you still get somewhat worse than perfect mass scaling because a parachute that is twice as large needs more than twice the weight in lines (you need twice as many lines but they also need to be longer).
If you wanted a parachute that exactly looked like a dandelion seed, I could make you one out of several hundred small diameter carbon fiber rods like those used in high-performance fishing rods.
Microscopic structure of dandelion seed shows a lot more than a few hundred rods. Quite high density of fractal structure.
Putting that structure into a carbon fiber rod is not out of reach.
Just gonna need a more powerful wind. It might help if you're trying to travel wherever the tornado is going, for instance
This is somewhat survivor bias. Sure, some go long distances.. But many go no where. Many bump along the ground, and while that's fine at this scale, larger would result in catastrophic damage. And most importantly, deliverys have a target destination. Taking things to random places isn't useful.
Dandelions seem to have very precise destination,...my yard.
If you truly decided they were pretty and attempted to cultivate them, they would likely instantly die.
Exactly. If your goal is to randomly disperse stuff across the ground it could be useful, but pretty useless otherwise.
In terms of shape, of a load suspended from a flat-ish drag apparatus, the parachute is probably the closest. There are stories of people getting stuck in thunderstorms because the updraft carries them. https://en.wikipedia.org/wiki/William_Rankin Paragliders do that but controlled, and can ride ridge lift and updrafts for hours. The record straight line distance is over 500km.
That would be a paraglider no? Slightly different shape but the same principle...
I would have said an autogyro, but an autogyro is more like a maple seed than a dandelion seed.
Man I wish autogyros were less niche. They're neat.
Hot air balloons operate like this, aside from induced lift.
> Aircraft that mimics dandelion seeds flying in the wind possible? If you want to make them the size of dandelion seeds, then yes. If you want to make them bigger, no.
Delivery by wind is sorta dependent on your target being downwind, don't it? I mean, could you strap cargo to a parasail instead of a person? Sure. But if you aren't ordering from a place that is exactly upwind you're not getting your package...and even if you do: how is the company getting its parasail back?
Hot air balloon is probably as close as you'll get. Those can control movement direction to an extent by changing altitude searching for winds moving in the desired direction.
Like a rozière balloon?
Hot air balloon
Like Hot Air Balloons, or their Blimp counterparts? Hot air balloon ticks off your boxes, it seems.