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Comment by twp | Hacker News Reader

This is really cool and innovative thinking, but anything aerodynamic does not scale linearly. It's really easy to make something light fall slowly. Baby spiders use "ballooning" -- a single thread -- to fall so slowly that they can travel far in thermal updrafts.

What's missing here is any evidence that the same cool parachutes will work on anything of significant mass, e.g. a parcel weighing 2kg or an average human weighing 80kg.

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  >Baby spiders use "ballooning" -- a single thread -- to fall so slowly that they can travel far in thermal updrafts.

It's even cooler. Spiders probably also exploit the Earth's natural electrostatic gradient (100 volts per meter!) to "ride" on electrostatic repulsion. This would even give up and down control, simply by changing the length of silk.

https://www.youtube.com/watch?v=Ja4oMFOoK50

https://www.feynmanlectures.caltech.edu/II_09.html

I was about to point this out as I recently learned about it from Howtown! https://youtube.com/shorts/qjUAhaRdVb4?si=iK94u6VQOnJ2IMn5

I've worked on mission planning software for parachute systems and the precision we can achieve is already extremely high. Given how poorly this seems to scale, the only use case that makes any sense to me would be something like sensor drop, which are the only payloads small enough for these chutes. Or potentially for drogues on multi-stage systems, but I'm not sure they'd even be useful there because usually a fast descent is part of the appeal of a drogued payload, and not just to reduce time exposed to wind drift (e.g., to reduce time it is vulnerable to enemy fire).

What kind of wind profile range and accuracy is necessary to achieve the high precision you mentioned ?

Depending on the use case, a hot-air balloon sized parachute to safely drop a person might be perfectly acceptable.

It looks like adding flexible ailerons or whatever they'd be called could give a big advantage in precision landing, with slower forward/sideways speeds but much better control.

Making it modular, with interlocking but separate parts, might make great sense for repairability and safety for skydiving? From the little I know of the sport, things tend to fail catastrophically, going from perfect condition to total disaster without a whole lot of graduated steps in between. I also wonder if there's some utility in paramotoring - multiple kirigami stabilizers, maybe, with a central parafoil, or one big kirigami rig with the fan blowing straight up its skirt?

This is awesome research. Paper drone-delivery parachutes are definitely a use case, but maybe some of the more dangerous flying sports could be made much safer, as well.

edit: Apparently no, 100 meter radius kirigami chute would be needed for a single person parachute, not exactly practical. Apparently it's just really, really good at ensuring things drop straight down with a lot of drag.

I agree that it's not a practical form of transportation, but that 100 meter radius parachute drop would be beautiful as an art project.

Does the (stainless steel?) vacuum bottle, used in their demo, not have significant mass?

https://www.coopoly.ca/p-545851-bouteille-noire-thermos-510m...

Note also the extra weight attached by the researchers to its bottom

(This is not yet taking into account the data-based scaling formulae presented in the paper)

Spider ballooning is an interesting phenomena. I also assumed that the spider is just falling a bit slower than the air is rising, due to convection. However some people think there is also a strong electrostatic component to spider ballooning. I'm not sure how that works once the spider is well clear of the ground though.

>I'm not sure how that works once the spider is well clear of the ground though.

Apparently the electric field is till quite strong some way from the surface.

The tested it with a standard size waterbottle, so you know it works fine for 0.8 kg paloads.

Unclear whether the water bottle had any water in it. Closer to 0.2kg if not.

>> does not scale linearly

It looks like it depends on the stiffness of the material (paper), so scaling it up to human (or bigger) sized will come with "interesting" challenges :(

Looking at the video, it seems that even the bottle lands quite fast.

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