Nano-scale inks could lighten airliners by hundreds of kilograms | Hacker News Reader

Nano-scale inks could lighten airliners by hundreds of kilograms

newatlas.com

43 pointsbookofjoe59 comments

> One area that's crying out for super-lightweight paints is the aviation sector. Airliners, according to Simple Flying, carry between 272-544 kg )600-1,200 lb) of paint – and everything an aircraft carries has a direct impact on fuel efficiency.

The vast majority of that weight is in the white paint on the body of the plane, which has to be thick because of mechanical abrasion in flight so that weight is largely unavoidable.

Also, "hundreds of kilograms" is not a lot if you consider how much the rest of the plane weighs --- a 737 MAX is ~100k lbs empty, so this is less than 1% of its empty weight, and a 747 is between 300-500k lbs empty.

Then again, given how airlines would cram in even 1 more passenger if they could, and the absolute minimum robustness of other mechanisms on a plane as a result of weight-saving, I think they will still chase after <1% gains.

>Also, "hundreds of kilograms" is not a lot if you consider how much the rest of the plane weighs

It's a lot more than you'd think: https://www.kiwi.com/stories/united-prints-lighter-magazine-...

Reports annual savings of about $300k by shaving a few grams off each of the pamphlets they stick in the seats.

That's about 0.0006% of United's revenue.

Or more like 0.006% of their profit. And this paint thing looks to be about 100x more weight difference, so perhaps 0.6% of their profit.

mmmm profit

Think about it as a small, seeminlgy useless change and giving your company 0.0006% more revenue.

Now every employee applies the same mindset and the company starts to fly (pun intended).

Or otherwise, you just not care about everything lose money everywhere.

The average profit of a large commercial passenger flight in the US is about one ticket.

If this were true, the majority of flights would be a loss.

If that were true, so what? That would be by my calculations 611,793,750 dollars a year for American Airlines Group (6700 flights/day, 250 dollars a ticket). While that is significantly less than their operating income, it's significantly more than their net income.

Why would that be the case? A flight can profitable even if it is half empty. The profit can still be one ticket.

The average flight is not half empty. If a half empty flight is profitable, then the profit of the average flight could not possibly be one ticket.

I think you are thinking about this way too much. The mean profit per flight is about $500. This number tells you nothing about whether a particular half empty flight is profitable or not. Literally every flight except one could be empty and you could still end up at a mean value of $500 if that one remaining flight is profitable enough.

I am surprised a 737 is only 100k lbs, I would have assumed like 250k. A blue whale weighs significantly more.

I assume that is a result of the need for the 737 to fly and for it to be as light as possible. The whale has no such constraint.

You jest (and you jest well)., And yet there is at least one rather-famously documented case of a whale grappling with that very same constraint:

"Another thing that got forgotten was the fact that against all probability a sperm whale had suddenly been called into existence several miles above the surface of an alien planet.

And since this is not a naturally tenable position for a whale, this poor innocent creature had very little time to come to terms with its identity as a whale before it then had to come to terms with not being a whale any more." -DA

That's not correct. The need for buoyancy is a very similar constraint, just with a different threshold. If a blue whale is too heavy (or rather more accurately, too dense), then it will become very challenging for the whale to surface to breathe.

But I'm not sure why anyone would want to paint one?

Can blue whales fly?

Can 737s swim?

https://en.wikipedia.org/wiki/Transair_Flight_810

(Sorry, could not resist...)

Weight doesn't tend to be a limiting factor for swimmers. Hence blue whales.

It does tend to be a limiting factor for fliers (hence hollow bones, etc). The heaviest flying creature on Earth does not exceed about 40 pounds.

Including extinct animals, the heaviest flier was not more than 550 pounds. A blue whale can weigh almost 1,000 times that.

I would think that modern planes are more constrained by volume than weight.

Not "constrained" really, but every pound you put up in the air costs fuel. Making the plane lighter immediately saves money.

> ... and the absolute minimum robustness of other mechanisms on a plane as a result of weight-saving ...

Being on a plane is the single safest place you could possible be at any time as a human.

Surely there are safer places, such as those that aren’t hours away from medical care…

You're correct. The other poster is thinking being one of the safest forms of transportation in terms of disastrous accidents == safest state of existence, which is a big misunderstanding.

It's a good thought exercise, but I suspect that's not the case. The plane will land and deposit you somewhere with nearby medical care, and except over the pacific or poles, you're not too far from an airport. There's also staff on hand that have more experience caring for most basic issues that might arise than the people around you ordinarily. There's also very good odds that a doctor is onboard, and of course, defibrillators will be onboard and at least in the US staff are trained to use them.

Further the places you'd be that aren't a plane have plenty of their own safety risks, that people aren't checking for constantly as a matter of course. Whereas on a plane, there's very little that can hurt you, and your job is to, well, remain seated. A fairly safe activity, in moderation.

Combined with the fact your risk of dying due to a fatal accident is about 500 in 9.4 billion, I stand by my rough assessment.

Does your calculations account for the base-risk value of what happens to people that die on planes, not necessarily death by planes.

Plane flight is an additional risk, it doesn't mitigate existing risks in place.

Probably true, but you also have to account for the mitigation of 'opportunity risks', rather than just the inherent risk of being (there's probably a proper name for this, but I don't know what it is).

For example, if you're on a plane, you're not scuba diving, base jumping, driving a car, etc.

I’ll be the first to admit it wasn’t properly calculated. I do think there’s some benefit to personal safety due to the selection bias and process for the people around you.

It might show up that way, but it's almost certainly not.

If all I do is sit in a chair, getting up to use the restroom occasionally, my home is probably safer than a plane. However the data will presumably show a much higher accident rate at home, because I also do things like cook, clean, and move goods.

Related, I bet cleaning and moving things have a fairly high accident rate on airplanes, but the accidents happen on the ground to employees so won't show up in the data.

> However the data will presumably show a much higher accident rate at home, because I also do things like cook, clean, and move goods.

Part of my premise is that a place you're forbidden from doing dangerous things is safe. I'm sure it's more dangerous to operate a chop saw on a plane, but you're not allowed to do that either. That's part of what makes it safe to be there ;) You're not allowed to do anything dangerous up there and neither is anyone around you. You're also screened on the way in for dangerous goods, and your ID is verified, and that of your fellow passengers.

> Related, I bet cleaning and moving things have a fairly high accident rate on airplanes, but the accidents happen on the ground to employees so won't show up in the data.

Sure, I meant as a passenger, not as a ramper or cleaner.

Do you have a source for that?

Global passenger volume in 2023 was about 8.6 billion, anticipated to be 9.4 billion in 2024. Total, global death count due to accident fatalities is measured in the hundreds. Usually 100-500 per year.

Global accidents per million departures usually hovers around 2, and that's not fatal accidents, which are about an order of magnitude less frequent.

Here's the 2023 ICAO safety report. [1]

[1] https://www.icao.int/safety/Documents/ICAO_SR_2023_20230823....

But nobody has ever died on my couch. There have been a few nonfatal accidents, but they mostly involved salsa going where it wasn't meant to and led to no injuries.

There were actually significantly more furniture tip-over injuries than airplane injuries since 2020. [1] So maybe you should add a yet ;)

[1] https://www.npr.org/2022/02/03/1077996126/furniture-tip-over...

That's pretty much all things like bookshelves, dressers, and TVs. Couches are not high on the list of furniture with a propensity for falling on children who use them incorrectly.

Could you expand on this?

Flying a jet at 600 mph through dusty air is abrasive. The paint protects the aluminum from corrosion and abrasion. If chemical and mechanical barrier is too thin, the metal will become damaged.

Not really. AA left their planes unpainted for decades and they were fine because aluminum is naturally corrosion resistant through the formation of aluminum oxide. However, the aluminum dulls and needs to be polished regularly to not look like shit. Also, the composite surfaces need to be painted to avoid UV damage, so most airlines just paint everything anyway.

Do airlines that have a “bare metal” livery still coat the planes with something, then? (I assume there’s a clear coat.) Does that weigh less than white paint?

Does anyone still do that? American Airlines has a white base now.

American stopped because the new composite planes like the 787 aren’t metal any more.

I'd assume the alternative is probably the same weight as paint, as the bulk of the paint mass is likely the protective polyurethane/whatever.

Or to put it another way, does clear paint weigh less than colored?

No, there is no clear coating. It's bare metal that gets polished:

> The metallic fuselage skin of modern airplanes is made of alclad aluminum alloy.

The word “alclad” means a thin layer of pure aluminum is applied over the entire aluminum alloy fuselage skin, generally a variant of 2024 alloy, at manufacture.

This pure aluminum layer almost immediately turns into aluminum oxide: and then begins its magic.

A bit of polish applied periodically keeps the pure aluminum layer at a silver shine, otherwise it grows dull — but still continues to protect.

https://www.quora.com/Why-did-American-Airlines-stop-paintin...

Is that still used in modern aircraft though?

Depositing a layer of pure Al on the surface seems... heavy.

Especially if you have access to high performance paints.

Absolutely:

> Alclad has been most commonly present in certain elements of an aircraft, including the fuselage, structural members, skin, and cowls. The aluminium alloy that Alclad is derived from has become one of the most commonly used of all aluminium-based alloys. While unclad aluminium has also continued to be extensively used on modern aircraft, which has a lower weight than Alclad, it is more prone to corrosion; the alternating use of the two materials is often defined by the specific components or elements that are composed of them. In aviation-grade Alclad, the thickness of the outer cladding layer typically varies between 1% and 15% of the total thickness.

https://en.wikipedia.org/wiki/Alclad

Yes, I read Wikipedia before posting.

It's unclear where exactly alclad is used in modern aircraft.

You don't need to be rude. I was trying to help. It's not like you were clear what level of detail you were looking for, and plenty of people don't.

Pigment does have weight. I'm not sure of anything useful that has no mass.

Photons are useful.

Not if you are blind

I'm both not blind and sure that fiber optics (and solar panels and trees) don't much care.

Blind people would find themselves cold and hungry without the sun’s photons.

To what extent would it be possible to trade off between that and more abrasion-resistant materials? Are there materials with a comparable or higher strength-to-weigh ratio that have less tendency to gradually ablate in 600mph air/dust/rain/etc? (Are there materials that would work better but cost more, and aluminum-with-thick-paint is a cost tradeoff?)

For clarity: I'm sure that aeronautics engineers have thought extensively about that question, and while it's possible that a small fraction of the answer is "we've always done it this way" and there might exist better alternatives, my expectation on balance is of learning the reasons why it's done this way.

related, I wonder how much tesla is saving with the cybertruck.

One important asterisk: how safe are the nano particles to humans and other critters?

Is aircraft-grade Hemp Composite lighter than fiberglass?

Aircraft-grade hemp composite appears to have a lower density than fiberglass, and greater tensility.

How does the greater tensility of [hemp-based] biocomposite wings and fuselages change the flight characteristics?

I remember seeing a YouTube video about how there are newer ways of laying down a round fiberglass fuselage that are much more efficient than basically additive lathing?

Speaking of aerospace-grade HEMP biocomposites instead of paint on fiberglass,

From https://news.ycombinator.com/item?id=39064549 :

> Would there be advantages to a tensile biocomposite with Starlite and/or Firepaste e.g. as a coating or blended?

> Can Starlite be used as heat shielding for [biocomposite] civilian rockets, and how would the reentry emissions differ?

Source - referenced in this summary: https://www.kobe-u.ac.jp/en/news/article/20240131-21760/

"These machines tend to be operational for several decades – provided they don't have 'Boeing,' '737' and 'Max' written on them – so there could yet be a strong business case for these ultra-thin structural color inks once they're ready for production."

LOL. Becomes a meme.

Reply on news.ycombinator.com