Kirigami-inspired parachute falls on target | Hacker News Reader

Kirigami-inspired parachute falls on target

physicsworld.com

309 pointssohkamyung90 comments

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.

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.

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.

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.

>> 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 :(

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 ?

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)

  >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

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

The journal Nature (where the original article was published) has a video about that parachute:

https://www.youtube.com/watch?v=6rrDW6YIbXI

I had to wonder if Nature (the Mother, not the journal) had first created anything similar, because she always does.

One answer is a dandelion seed. Not exactly the same, but a dandelion seed is about 85%+ "porous" - the pores here being the space between the spindles, not actual holes per se. And it turns out that high porosity is critical to stabilizing the wake turbulence not unlike what is described in the Nature video. https://sites.nd.edu/biomechanics-in-the-wild/2021/06/01/inn...

A learning that kirigami parachute researches might apply: The dandelion pappus is less porous near the center and becomes more porous toward the outer edge. A lower porosity near the central hub can increase shear flow, helping to detach and strengthen the vortex

Furthermore, spiders which have been known to "balloon" on the wind even across entire oceans use multiple strands of silk which are negatively charged to repel each other, thus forming some of the same gaps that are seen in a dandelion pappus, with similar aerodynamic benefits. https://journals.aps.org/pre/abstract/10.1103/PhysRevE.105.0...

The fine article mentions this, including mentioning dandelion seeds specifically:

  > As well as kirigami, the team drew inspiration from nature. Instead of relying on a gliding angle, many wind-dispersed seeds are equipped with structures that stabilize the airflow around them: including the feathery bristles of dandelion seeds, which create a stabilized vortex in their wake.

Is that really Nature's channel? It sucks that I have to ask, but I just ran across that video (and channel) on the weekend. I have a new policy where I don't trust videos to not be AI slop when they don't have a real, on screen presenter. This one didn't, but it also didn't really feel like AI slop, but it could have been stolen content since that is very common nowadays because it goes unpunished.

I was reseaching kirigami yesterday for a DYI project, and it was the first time I heard about kirigami, and of course I stumbled upon the parachute application. And now its on the front page of HN?

To whoever is running the simulation: This is a bit on the nose. And don't even try to Baader-Meinhof me.

Hey! As a simulated NPC, I don't appreciate being called out like that.

Wanna go consume a_beer at local_tavern? I'm in-between MMORPG adventures.

I used to be an adventurer like you.

But the I took an arrow to the knee.

Baader-Meinhof in action :)

I hope the paper and cardboard construction they mention is feasible for commercial use. Otherwise I'm picturing a future where drone deliveries are commonplace and these plastic parachutes litter our streets and waterways.

I always assumed that drone delivery was just a publicity stunt (in urban areas anyway). I am hoping that it stays that way. I am really not convinced that a sky full of buzzing drones delivering people's toothpaste and takeaways is a great idea.

But it would probably makes economic sense. A big cost of delivery is the personal that actually does the delivery. It might not be viable for all packages but probably for the premium delivery that promises sub 1 hour delivery.

>But it would probably makes economic sense.

Only if you don't price in all the externalities: loss of delivery jobs, environmental cost of the drones, cost of drones hitting people, cars, buildings and powerlines etc.

Replacing jobs with better or lower cost alternatives is not an externality.

Like if you switch from a low quality butcher to a higher quality butcher, you are not imposing a cost on the lower quality butcher.

You can not like it as a consequence of course, whether it is an externality or not.

>Replacing jobs with better or lower cost alternatives is not an externality.

Replacing 3 delivery guys with 1 drone maintenance guy imposes a cost on society if those delivery guys can't then find work.

Fine, then we stop making heavy equipment and dig ditches with spoons.

It'll be like living in a late-game Factorio base.

I think this would actually make me buy less stuff. Like, I can see the neighbors think, oh look, wkjagt getting junk from Amazon AGAIN.

Biopolymer or paper, hopefully.

(not a very serious comment, feel free to skip)

This is a funny timing. I was just discussing with my son this morning what the most efficient ways were to set free the mice we catch in our mouse friendly trap. One of the "options" we came up with was a launching mechanism and a tiny parachute to send them to a field at the end of our street. The main problem we came up with was that it was really hard to predict where the mouse would land. I'll show him this kirigami design this afternoon :-)

(Disclaimer: obviously we're not actually launching mice. These are just thought experiments. I actually walk to the field to release the mice.)

I've read that you have to move them several miles if you don't want them to return. Back when I had a mouse problem, I would take them to a field behind my gym.

Now your gym has a mouse problem :)

But the mice solved their adipose tendency problem!

That would be pretty cool actually. Maybe I'm going to start marking them, to see if maybe it's always the same mouse :-)

Regretting my choice to do a PhD in CS instead of whatever this cool thing is…

your PhD probably gives you the wherewithal to do the cool things now or after a few years of work ...

I mean, sure, it does, but I could have had a PhD in folding pieces of paper!

*cutting

Krigami is about folding and cutting - this looks like cutting only, though it kind of folds due to air drag

They also looked at using Origami with the Kirigami to see if they could pack the parachute in novel ways (according to the Nature video)

I mean, you could have BOTH!

Applied topology and fluid dynamics + origami? Pretty sure there’s no program for this so you can just show up.

Also I bet they really need people who can help with the simulations. If you email the authors you can probably get added to the team.

I too love this. It’s that intersection of devilishly hard and almost useless unless you squint then it’s sci-fi magic tech. There are quite a few cases where you want the parachute to drop straight down.

>There are quite a few cases where you want the parachute to drop straight down.

Model rocketry, for example. You don't want your rocket to drift miles on its chute. However this is mostly solved by 2 stage deploy (drogue deployed at apogee, then full size chute deployed near ground).

Related work that his lab was doing when I got to take a seminar with him at IU: https://gwern.net/doc/design/typography/1993-mcgraw.pdf

Gary was one of the TAs in the class. The non-reducibility of letterforms has remained a fascination—I always did like the (computational) linguistics corner of cognitive science!

https://news.ycombinator.com/item?id=45495711 - I think you meant to comment on this one.

Really cool stuff, and it's published in Nature proper [1].

What an achievement for such a simple and elegant solution, bravo!

[1] Kirigami-inspired parachutes with programmable reconfiguration:

https://www.nature.com/articles/s41586-025-09515-9

Reminds me of a shuttlecock.

I wonder if it is easier/lighter to make a parachute that can handle different speeds, e.g. for atmospheric reentry, reusing the same structure for the drogue chute and the main chutes.

idk still looks like it hits pretty hard https://youtu.be/6rrDW6YIbXI?t=246

Manufacturing cost is a major benefit of this kind of design. You could just stamp these out of paper en masse for pennies. Great for mass production.

And at first I thought, "Why would anyone need parachutes for pennies? Hell, we don't need those coins in the first place!"

I wonder if this would be suitable for drone delivery of small groceries, to keep the drone high enough that people don’t have to hear the noise.

This looks perfect for bomblets. I imagine the Ukrainians are already stamping these out of plastic somewhere.

Why would you want to make a bomblet fall more slowly (allowing the intended targets to escape)? They already have fins to maintain their approximate direction.

Yeah, I can't think of a single use case for ordnance, which if anything you typically want to travel faster not slower.

Illumination flares. Air dropped mines.

However it isn't clear that these would be any better than conventional parachutes.

Improvised plunger-type fuzes depend on the bomb(let) falling straight down. This ensures that occurs, but takes up very little packing space compared to a more conventional empennage. A straight up-and-down attitude also tends to increase the efficiency of fragmentation bomb(let)s.

Secondarily, slowing the weapon can be useful for low flying platforms. Retarded bombs use spring-loaded airbrakes, inflatable ballutes, and/or parachutes to slow the weapon enough to allow the bomber to escape damage.

Example: parafrag bombs in WW2, extensively used against soft targets. The USAAF found them three times more effective than fin stabilized fragmentation bombs of the same size.

https://www.youtube.com/watch?v=RRJHMtWoQ28

I hear you, but I also look at how bombs are typically being used in Ukraine; they're small enough not to present any risk to the drone that's dropping them vertically usually on unfortunate individual soldiers).

That war frequently goes very low tech (kind of COTS :) - plastic bottle as stabilizers

https://youtu.be/dcsf5yuEHDY?t=69

https://forum.cartridgecollectors.org/t/drone-dropped-anti-t...

On the second pipe you can also see small fan which probably arms the side attached detonator.

Linked paper: https://www.nature.com/articles/s41586-025-09515-9.epdf

Modern parachutes can be packed relatively small and open quite quickly. Not sure how you would pack one of these parachutes, especially if they are made from a relatively stiff plastic.

It comes as a flat disc. For some applications that might be more convenient packaging than traditional parachutes.

And then you could roll the flat disc into a tube.

I really like this kind of exploration that blends natural principles, aesthetics, and engineering. It is not just a technical breakthrough but a fresh way of thinking about what it means to land.

I can imagine how meaningful it would be if one day these kirigami parachutes are used to drop medical supplies, support disaster relief, or even serve space missions. Beautiful and practical at the same time.

Relief packages, cheaply dispersed over a multi-block area, would make it more difficult for invading forces to massacre civilians at drop sites.

I can think of one place that would have IMMEDIATE utility.

Looks like it could stuck around animals necks like soda can 6 pack packaging.

> When dropping a payload from a drone or aircraft, this gliding angle means parachutes will often drift far from their intended targets. This can be especially frustrating and potentially dangerous for operations such as humanitarian aid delivery, where precisely targeted airdrops are often vital to success.

I could't help but roll my eyes at this textbook example of describing new technology as being "useful for humanitarian or search & rescue work", instead of the much more obvious usefulness in military applications.

Who's kidding who about what "precisely targeted airdrops" are most likely to be used for? These will be in use by Ukraine well before anything beyond a technology demo drops on to a "stranded hiker" in a National Park...

I thought the same at first, but actually - you don't want your bombs to fall slowly. Supply drops are another matter. These don't kill people directly at least.

This looks like a good way if not only ensuring that things fall slowly, but also ensuring that they fall in the proper orientation. Gravity bombs typically use fins at the back for this purpose, but that makes them actually turn into the wind by pushing the back of the bomb in the direction of the wind. Smaller fins combined with some drag provided by such a parachute as this, could help gravity bombs be more resistant to winds, while ensuring that the fuse stays pointed down.

You do when you're flying low and you need to escape the munition's effective radius.

Retarded bombs are slowed with a variety of mechanisms, from spring-loaded airbrakes to inflatable ballutes to parachutes. Fuzing can range from superquick for conventional bombs to extended timers for nuclear weapons, all depending upon the application. These parachutes would be great for low flying drone bombers as well as munitions that are highly attitude-sensitive (such as those with improvised fuzes).

I want my landmines to fall slowly, directly and land in a specific orientation. I also want to keep the cost low so that I can distribute a whole lot of them.

This is for Amazon deliveries. The whole thing is written for that, the material is the same as their packaging even.

Bombs go down fast, specially from drones, there's no advantage in slowing them down.

>I could't help but roll my eyes at this textbook example of describing new technology as being "useful for humanitarian or search & rescue work", instead of the much more obvious usefulness in military applications.

I've seen this so many times now. Is there a established Internet meme for it yet?

Both can be simultaneously true.

Dropping supplies to isolated or behind-the-lines forces is a very real logistical issue. While some of those supplies might be munitions, rations and medical supplies are a significant part of the need.

I know, it doesn't make you feel any friendlier to the issue, but tech has multiple applications. Chainsaws were invented to increase survivability of mothers in difficult births.

How long before we see these attached to bombs dropped by drones? It would reduce time over target and likely increase accuracy.

Dropping bombs straight down seems like a solved problem. The difficult part here is dropping something slowly.

Cool. This looks like a huge ecological nightmare similar to six pack rings and shopping plastic bags.

Rest assured. This will only be used for cluster bombs.

Six pack rings were the first thing I thought of when I saw the picture. The article says they made the parachutes out of paper and cardboard too, but if history is any guide they'll end up making them from plastic. "What if it rains!?"

Can one nest those kirigami structures on top of each other? Imagine if you had a smaller-diameter version right on top of it. It would open up inside the outer one, increasing the surface area. The bottle example didn't seem convincing in and of itself in the videos, but the small egg and LEGO figure had what looked like somewhat functional.

My uneducated guess is that they would interfere with each other, and only whatever portion of the top ones that fits the profile of a single, larger chute would give you any extra lift. To the point that you are better just making a single one the size you need.

now swoop it!

Insane how much precision our modern world needs for people to be happy.

My grandma wouldn't have been happy if my father dumped the bucket from the well near the kitchen sink.

Nothing much has changed about precision in delivery of goods.

"drone delivery and humanitarian aid". Right. Thousands of military FPV drone operators beg to differ.

That's literally drone delivery.

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