The Celera 500L passenger plane gets hydrogen powertrain | Hacker News Reader

The Celera 500L passenger plane gets hydrogen powertrain

newatlas.com

126 pointsclouddrover140 comments

for comparison between battery and energy density:

typical lipo as used in a short flight endurance hobby quadcopter (5-7" prop size) is 155Wh/kg

the best lithium ion cylindrical cells are around 255Wh/kg right now. quite a bit more limited in instantaneous amperage draw per cell than high C rate lipo.

hydrogen fuel cell tank+PEM+piping+DC apparatus for large octocopters comes in somewhere around 1500Wh/kg

There's a south korean company that recently hovered a large octocopter with hydrogen power source for 10.5 hours. Same system with lithium ion battery power would be approximately a 1 hour endurance.

note that 1500Wh/kg is considerably less than the energy density of jet-a or diesel or ordinary 87/89 octane petrol, BUT, you have to account for 50% of it being lost to waste heat in an internal combustion engine, and the weight of the engine and drivetrain. or weight of jet turbine+generator vs hydrogen tank + fuel cell PEM apparatus.

255Wh/kg? That’s not true. About 300Wh/kg has been available for over a decade. The next Gen lithium metal anode and lithium sulfur batteries can do 400-500Wh/kg, up to 650Wh/kg in the lab.

I'm referring to li ion cylindrical cells in the 18650, 20700 and 21700 formats which are commercially available right now. Which I can buy online in 5 minutes with my visa card from a battery wholesaler.

If you can find me the pdf datasheet for one that's above that I'd love to see it!

And even better a vendor link.

Note I am also referring to something like the actual usable watt hours from a battery before you discharge it below "permanently damaged" state, in the range starting from 100% SOC standard full voltage and manufacturer's do-not-exceed floor voltage. Such as on the NCR18650GA.

I don't doubt there are specialty rare "ask us for a price" low volume 300Wh/kg in circulation if you have the right contacts.

Okay, but you can’t get a non-science-kit fuel cell of decent size online in 5 minutes with my visa card from a battery wholesaler. You need the right contacts.

We can: https://www.fuelcellstore.com/

Their max fuel cell stack goes up to 6kw so its no longer in hobby territory.

Thanks!

Still pretty expensive and heavy for just a 6kW fuel cell stack alone! $27,000 is the base MSRP for a Chevy Bolt, before incentives.

So we're down to only a 50% energy density compared to a fuel cell.

But the fuel cell uses hydrogen, which leaks inevitably (it slowly diffuses through all materials), and is an extremely potent greenhouse effect gas.

How long does it take for hydrogen floating in the atmosphere to react with the oxygen?

Your question would make sense only if it was a direct greenhouse effect gas, but H2 effect is indirect (but still huge), precisely in the way it disappears by combining with other molecules.

The greenhouse effect of H2 is by reacting with the HO naturally present in the atmosphere (giving water vapour: 2 HO + H2 -> 2 H2O), thus reducing the concentration of HO, and thus modifiying the dynamics of atmospheric methane and ozone.

From my understanding, in the atmosphere, HO has an important role in the decay of CH4.

http://agage.mit.edu/publications/global-environmental-impac...

No, that is factually incorrect, hydrogen is not an "extremely potent" greenhouse gas in this context.

Hydrogen has a GWP of 11, meaning it is 11 times worse than emitting CO2. Methane, for example, has a GWP of 34, which is starting to get kind of bad, but "extremely potent" is something like SF6 wich has a GWP of 22800.

Furthermore, GWP is calculated on a mass basis, which skews things a lot for a light molecule like hydrogen.

I'm kind of astonished at the fear mongering on this issue, because it means people cannot be arsed to spend 20 minutes on Google with a calculator to check the numbers before they spread something as a truth. Let's do the actual math.

If you look at a Toyota Mirai, it needs 5 kg of hydrogen to get a 300 mile range. A comparable diesel car needs 28 kg diesel to get that range, and will emit 88 kg of CO2 when that diesel is burned (the O's in CO2 comes from the air).

Even if the hydrogen car had an absurdly high leakage rate of 50% during that trip and the period it stood still before next trip, it would still emit only the equivalent of 27.5 kg of CO2. So at insanely high leakage rate, diesel is still 3x worse than hydrogen.

If we are realistic about leakage rate, published numbers from actual measurements with the Toyota Mirai placed in a sealed container gives us 2 mL/min at 1 bar, so the time to leak the entire contents of the tank is more than 3000 days.

So let's say this is a hobby vehicle (like a small aircraft) seeing infrequent use, you consume two tanks of hydrogen per month. That puts your leakage rate at 0.5%, giving an emissions equivalent of 0.56 kg CO2, while the diesel (avgas) powered equivalent would emit 166 kg CO2 - 300x worse.

Note that this is all based on technology that is already here - you can go buy it today - not some hypothetical developments.

It's never a bad time to remind that avgas still contains lead.

Of course, but my point is do we choose to invest massively in hydrogen planes or in battery planes.

Once done the choice it's hard to go back.

We should do both. Both hydrogen and battery use an electrified power train, and the hydrogen plane would probably have a small lithium battery anyway.

I agree.

All I care is that all GHG are accounted thoroughly, including H2 leaks. Then, if at the end we are reducing atmospheric GHG contents at the planned rate, all is fine.

Please don't say CH4 is "kind of bad". It's an atrocious threat for the planet (and Humanity) right now (thawing of permafrost and of oceanic floor, etc).

Be it 11x more potent that CO2 or just 1x, it's completely enough that H2 has a GHG effect, and that H2 leaks are impossible to prevent due to the size of the molecule.

For me, that's enough to make it less desirable than batteries, especially if we are speaking of policies of mass investment on a planet scale!!!

Also, you use a leakage at 1bar then you transpose it to a plane which would obviously not transport the H2 at 1bar but at a much higher pressure.

Finally, if it is not zero-carbon, then it is not. Even "a little" is not zero.

We need to account for it, and never put ZERO on this CO2e accounting line, that's all.

Oh I agree that methane is a horrible threat if it is released at massive scale, like from the permafrost. We should absolutely do everything we can to avoid that.

My point is that if you compare hydrogen on propulsion equivalent basis and with realistic leakage rates, it is so much better than today's solutions that we should absolutely use it.

When it comes to batteries, yeah, that's just not going to happen for anything over 20 passengers and 200 mile operating range. It's physically impossible to obtain sufficient Wh/kg to run even a small airliner on batteries. Airbus is investing heavily in liquid hydrogen fuelled jets, and it's not because they are stupid.

> Also, you use a leakage at 1bar then you transpose it to a plane which would obviously not transport the H2 at 1bar but at a much higher pressure.

So this part was probably too brief in my first post to be perfectly clear. Imagine that you have the 700 bar pressure tank of the Toyota Mirai, and the entire leakage out to 1 bar (the atmosphere) happens in a single point. Then you put a ballon over that point and measure how quickly it grows. That rate is reported as "2 mL/min at 1 bar".

Ok, thanks for the clarification about the calculation. (I should have seen that, as a gas stored at 1 bar will not pour out of its container very well)

That is fine to employ H2 technology if all is accounted for and the leaks are included in the big picture (at consumer end-points as well as producer end-points).

Because, as a reminder, about emissions, we do not only need to "do a lot better" than now, we need to do zero (scratch that, we need to do negative).

As an aside:

> Airbus is investing heavily in liquid hydrogen fuelled jets, and it's not because they are stupid.

Well, I would not use that as an argument. For example Toyota invested a lot in the wrong direction (and now they cling on their hybrid vehicles even if it makes no sense). (Even worse, see the diesielgate with Volkswagen. Huge corporations can do stupid things)

What a truly amazing comment. Upvoted, but I needed to explicitly praise it as well.

Thanks. You made me richer (as in: wiser) today.

The effective GHG potential is about 200x CO2. All of that, short of 6x direct effect, is secondary effects, e.g. scavenging the stuff that removes CH4 from that atmosphere.

It is not at all hard to look this up.

But it doesn't matter very much for aviation; you make it on the spot, put it in, take off, and burn it all before it gets a chance to leak. LH2 does not seep through everything like gaseous H2. It's cold. It freezes stuff it touches, too.

50% of the energy density of a setup using compressed hydrogen. Large passenger aircraft are more likely to use liquid hydrogen if hydrogen does indeed become the fuel of choice. LH2 aircraft could actually exceed the performance of fossil fuelled aircraft, let alone battery electric.

Batteries also leak energy, and no, hydrogen isn't a potent greenhouse gas.

Your last statement is false, H2 is a potent ghg, because it removes OH molecules from atmosphere and thus modifies the dynamics of ozone and methane:

http://agage.mit.edu/publications/global-environmental-impac...

We really need to think twice before investing like crazy and reaching the point of no return on a technology that could bring the threat that it was meant to let us escape from...

At least with batteries we do not have this risk of GHG leaks.

As for:

> Batteries also leak energy

this is not the same at all, batteries do not leak anything outside of themselves, the "leak" you're speaking about is the battery consuming slowly its own chemical potential energy. They do not emit anything physical.

> BUT, you have to account for 50% of it being lost to waste heat in an internal combustion engine

What's the efficiency of a battery-powered system in flight? E.g. disregarding ground charging and grid supply.

(edit) Wikipedia says ~95% for a generic electric motor and ~85% for a generic lithium-ion battery for a very rough estimate of about 80% efficiency in toto.

Also depends how you have many batteries paralleled and the amp draw per cell, for instance a single Sony vtc6 cell might be ok for 30A draw for short times but will heat up while doing it. And needs cooling/thermal dissipation solution. The lower amp draw per cell the less is lost to heat.

Note that a full sized battery pack will also need piping, cooling, cables, etc. So it won't actually reach 255 Wh/kg.

Some analysis from the 'aviation forums':

> But let's say you can climb the thing at 1000FPM and 100KIAS. That takes you an hour (covering roughly 250 nm?) to hit 65,000. If you spend an hour at cruise and then come down at 2000 fpm again covering 150nm ... you've just taken 2:30 block to go 900nm. What market does that make sense in? Might make a great autonomous cargo bird for Fedex.

> People spending 5 million on an airplane do not care about $180 of fuel difference per flight, and also that is only at altitude. If the climb rate of that airplane is 1,000fpm, which seems optimistic, it would take nearly an hour to get up there. If you are going on a 2 or 3 hour leg, fuel burn could be the same or worse.

https://www.beechtalk.com/forums/viewtopic.php?f=49&t=174467...

Longer analysis video:

https://www.youtube.com/watch?v=E38cc-4TvX8

IMHO (almost layman), takoff catapult is the way to go for energy efficiency of aircraft. If you imagine a takeoff around 200KIAS, the conversion of cynetic energy in potential energy gives you a big part of the climb. The spared energy would increase the flight range.

Prototype can hold 6 passengers. The design can scale up to 19, but "the low-drag laminar flow model relies on a width-to-length ratio that'd be impractical in a bigger bird" so it won't work for airline use.

Was wondering about this - im just not that impressed about anyone making personal jets more efficient. Those things shouldn’t be in the sky in the first place.

Fully agreed. Personal aviation is ludicrously inefficient and still often remains outside of meaningful regulation in key ways like using leaded fuels. Poisoning the globe and locales for one person’s convenience should always be questioned as a sign of inequality too far gone

I imagine that at capacity, they can just as efficient as larger jets (if not more efficient). There may be a sweet spot in terms of efficiency that can be achieved that is smaller than what we've got now. We've already seen jumbo jets fall out of favor, and e.g. this can be seen in the sales of the A380 and 787 (launched around the same big, with A380 going big, and 787 going efficient and mid-sized with about 10x the sales). I imagine that planes would get smaller still, but the reason they don't is that even with high oil prices, human costs still tend to dominate the cost of a flight (two pilots, cabin crew). It's not so hard to imagine that with more automation it will become viable to have much smaller, more frequent routes that are both more economically and environmentally efficient.

Jetliners have an industry average 51mpg per passenger. Private learjets pull, at capacity, 28mpg per passenger. I’ll let you decide which one of these flies around more often at lower percentages of capacity.

Learjet was a brand name (used to be an independent company founded by Bill Lear), which is no longer active (after having been acquired and subsequently discontinued). The more generic terms are 'general aviation' and 'business aviation'; most small jets are 'business jets'.

I am citing specific statistics for a specific and popular private jet, as these things are not well analyzed for not surprising reasons. Feel free to prove the point with statistics, semantics are definitely an aside to the point at hand

You're comparing obsolete small jets to a much newer fleet of commercial passenger aircraft. While business jets do tend to be older, your choice is rather extreme, and introduces a huge bias. This website has some interesting examples of more modern aircraft in a few categories: https://www.flyingmag.com/the-most-fuel-efficient-aircraft-i...

A bunch of 4mpg 7-8 seaters align perfectly with my criticism of private jets. Actually, I don’t really understand what leads you to think there is any pressure in this space for fuel efficient development. In the space of jetliners, the airlines optimize for cost, of which fuel is a primary driver.

While it is cool local planes pull 25mpg, they spew lead on their local communities.

I don’t think humanity can put the cat of air travel back in the bag, and if I understand correctly the SUV market is actually driving as much CO2 emissions as the entirety of aviation; I still don’t see why individuals should be privileged to do such damage of poison and inefficiency for their pleasure. It is pleasing to others to imagine a long lived humanity on a globe hosting life as we know it, after all.

Obviously the private jet industry optimizes more for comfort and other things before efficiency today.

The commercial aviation industry does optimize for efficiency but only with larger planes since human costs (and airport costs) are mostly fixed per plane.

I’m simply saying that perhaps the future could have smaller, more efficient planes and more automation that removes fixed costs. (The design in the article is such a plane, in theory.) You seem to be conflating big/small with commercial/private and taking a firm anti-private position.

Jets [and turboprops] don’t use leaded fuel. Many of the small, piston-engined airplanes do, but because current FAA regulation forces them to, not because of a lack of regulation.

And some engines are rated to run automotive gas, but it's just not available at smaller airports.

Most of those are only rated to run on E0 (ethanol-free) gasoline, which is also hard to find outside the airport fence in most places.

I was actually surprised when I looked how many places carry e0. There were several near me in Seattle. https://www.pure-gas.org/

Off-topic question. Did you have to advance your ignition timing when you started running E0? I've thought about using it in my Datsun, especially with E15 rolling out now. I've got a 1980 280ZX, modded with flat top pistons mated w/ a p79 head for about 10:1 compression. Currently though, with normal E10 92 octane gas, I have the distributor set to maximum advance and even with that I feel like it's not getting peak performance. In theory I should already be running lower octane for more advance, but I don't b/c I worry about detonation, and my understanding is that E0 is also more prone to detonation than the same octane ethanol blend b/c it runs hotter without the evaporative cooling of the ethanol, so I might even need to back off the advance when really I'd like to increase it. Did you find running E0 retarded the timing and/or led to any performance changes?

I’ve run some modded engines (including higher than stock compression) and for street usage, I’d be worried about the variability of gas you get over the years. You’re eventually going to get some crap gas on a hot day and have a bad day if you’re right on the ragged edge (especially without knock sensing).

For track or drag usage, running on the ragged edge makes more sense.

I use it for small engines and my motorcycle for the most part. The place by me is all boats, performance cars, snowmobiles, and people with 7 Jerry cans.

I would, as I did, call regulations forcing stupidity as a lack of meaningful regulation; but I take your point. It is even a problem of negative regulation.

Small jets do indeed use jet fuel but have a terrible efficiency proposition when ran at even 50% capacity, which is not the standard use case.

It hasn't been a regulation issue from the FAA that piston engines must use leaded fuel for some reason but rather there hasn't been a viable unleaded aviation fuel that worked with all piston engines.

This is about to change though with G100UL finally being approved. https://gami.com/g100ul/g100ul.php.

It’s on the type certificate that stock Lycoming and Continental engines are certified to run on 100LL. The standard for 100LL is a composition standard (not a performance standard; it literally has to have x grams of TEL/gallon, not just have a certain demonstrated octane).

Absent an STC (Supplemental Type Certificate) to change that, there is a regulation that those engines in certified aircraft have to use leaded fuel to be airworthy (legal) as airworthiness requires both “in condition for safe operation” and “in conformance with its type design”.

GAMI is pursuing an all-model (or many, many model) STC for their fuel to remedy this, but it’s a regulation issue currently.

Let's not be so dramatic as to say that the general aviation fleet is single handedly responsible for poisoning the world with lead.

When leaded car gas was still in use it resulted in 4-5 million tons of lead emissions per year.[1]

The use of leaded aviation fuel contributes 500 tons per year according to the EPA[2]. Compared to 5,000,000 tons for cars historically.

Of course, any lead is not good and we should be shooting for zero. Which is the goal of the unleaded G100UL aviation fuel. But let's not try to say that personal aviation is evil when it's contributing a fraction of a percent of lead contamination. Frankly, we have bigger pollution problems to worry about than a very small amount of lead emissions from an ever shrinking fleet of piston powered aircraft.

Mind you that general aviation is more than rich people flying around in their planes. It's medical flights, it's training future airline pilots, it's aerial surveying, and many more critical tasks for society.

1. https://grist.org/regulation/leaded-gasoline-lead-poisoning-...

2. http://www.reidhillview.com/EPA_GA_Lead_2002.pdf

https://paloaltoonline.com/news/2021/08/06/new-study-finds-l...

I in no way imply aviation is the greatest poison emitted by humanity; it is one of the most selfish emissions by any standard. It is not that leased fuels support meaningful industry as suggested, nor is it as if there are not alternatives. Instead, the FAA and pilots of piston driven planes have simply decided lead poisoning is a justifiable price to pay for people living near an airport in exchange for individuals getting to fly their quarter million+ $ aircraft.

Everything you suggest it is useful for could be performed with the already proven and no longer new unleaded alternative. Defending this practice is asinine.

The source you cited conveniently links to a 404 page for the study it cites.

But yes, I've read quite a bit about the Reid-Hillview Airport saga. These claims of leaded gas hurting the children around airport is just the newest in a long list of excuses to close airports so their land can be redeveloped into more strip malls and condos. These neighborhood groups are biased towards wanting airports closed. It's textbook NIMBYism and they'll look for any excuse to achieve their goals. If it's not leaded gas, it's something else.

> Instead, the FAA and pilots of piston driven planes have simply decided lead poisoning is a justifiable price to pay for people living near an airport in exchange for individuals getting to fly their quarter million+ $ aircraft.

Don't buy a house near an airport if you're concerned about it then. The airport was there before the houses were.

> Everything you suggest it is useful for could be performed with the already proven and no longer new unleaded alternative. Defending this practice is asinine.

Where did I say I liked leaded gas exactly? I'm quite excited about G100UL being rolled out, even if it costs a bit more, so I can stop having this exact argument about how we need to close airports because of leaded gas. Everything with the FAA moves slowly, but it's moving. We're about to have unleaded gas for all planes.

By the way, the average Cessna 172 is well under $100k (at least prior to the previous two years before asset prices for everything went through the roof). For every fancy late model Cirrus SR22T there's 10 more shitbox Cessna's from the 1970s barely hanging onto life. You think of private pilots as all extremely wealthy individuals. Most of us are solidly middle class. How many people have boats or RVs that cost the same or more? Small planes fall into that same category.

> These claims of leaded gas hurting the children around airport is just the newest in a long list of excuses to close airports so their land can be redeveloped into more strip malls and condos

One thing particularly twisted about that is:

1. The airport announced that it is trying to convert to unleaded fuel

2. Immediately after that announcement, the NIMBYs tried to get an emergency judgement to close the airport (because converting to UL fuel would completely undermine their only semi-legitimate argument for closure)

3. If the airport is closed, and if the lead pollution is truly as bad as they claim, then it will be economically infeasible to re-develop the airport as condos (which is what they're actually trying to do, not save the children) because the ground would be too polluted.

cleveland and st pete, fl, have awesome airports at risk of closure for no reason other than water front property means expensive condos. only thing saving KSPg right now is that they took FAA grant money and cant be closed for eight years as a result

I'm agree with you about lead is bad, but only oldest designs of aircraft engines depend on lead (they use it as lubricant for valves, as it deposits on surfaces when gas evaporate).

Because of this, leaded gas still produced in commercial volumes.

Modern aircraft engines could work on unleaded gas, and especially Celera use aircraft diesel engine, working on basically aviation kerosene (with tiny addition of lubricants for diesel equipment).

BTW diesel add about 30% of Celera range.

Yup, and I really hope we get G100UL distributed widely soon so we can stop having this asinine discussion about how we need to close airports because we're all going to die from the tiny amount of lead they emit.

Ideally we could have the FAA promote the certification of newer engine designs so we didn't need to keep flying around with 1940s engine tech as well that relies on lead, but that's another issue.

Agree. Each day,decreased number of old cool planes, which flight from 1940s and still in flight condition.

I cry every time see, how good maintained old aviation history in US, comparable to exUSSR.

Even more impressive, there are examples of old soviet planes in flight condition in US - you will not see them flight in exUSSR.

Unfortunately, not all 1940s engines have modern substitutions.

For me this is our history. I think it is acceptable to make for them exclusion from rules.

90% of the world's piston GA fleet is using 80 year old engine designs, so...

19 passengers isn’t personal aviation. It comparable to passenger aircraft used in places like islands and elsewhere where demand isn’t enough for big jets and there’s no ground option.

Fundamentally, it could be nearly as cost efficient as large jets. The pilot wage is a small portion of the overall cost. A big reason big jets are big is because jet propulsion scales down poorly while electric scales down very well.

For plane engineering aware person, all ok.

- Commercial planes begin at about 50-60 seats, less are non-viable.

Normal commercial size - 100 seats.

For air-dynamics, 3 times capacity enlarge (from 6 to 18) typically possible, but more changes too much.

And 3 times capacity in avia measured non linear, but with famous square-cube rule, which mean, change size will increase mass as square, but capacity as cube, so to got 3x capacity, need 1.443 increase of size (1.442^3=3.0046853).

> "the low-drag laminar flow model relies on a width-to-length ratio that'd be impractical in a bigger bird" so it won't work for airline use.

We can always reimagine airports as well.

I don't believe regular planes to ever run on hydrogen and be commercially viable. Hydrogen is not very dense, even in liquid form (to be compared with the volume already taken by kerosene on a plane). And requires very strong -and thick- container walls.

However with dwindling fuel supplies, I'm pretty positive we'll see the return of glorious, massive blimps. Powered by a fraction of the hydrogen it uses to float in the air, savvy meteorology, and thin solar panels.

Can't the low density be taken advantage of, producing aircraft with blimp-ish characteristics? Not sure how practical that is...

And given how big % of fuel is needed for ascending to cruise height, I'd imagine you could have a decent % of the fuel in take-off tanks with thin walls, since those tanks only need to contain the fuel for less than 10 minutes anyway.

I could imagine future planes using hydrogen for take-off and batteries for cruising.

> producing aircraft with blimp-ish characteristics

Drag nearly directly proportional to the cross section of the craft. Something blimp like would be necessarily slow, to stay efficient.

This is true, but depending on how you use the hydrogen, you can fly much higher than you would with kerosene. Hydrogen burning jets would fly at around 70-80k feet, not the usual 35k that we're used to. Not to mention, the weight savings mean you cut down on the amount of fuel you need to carry, so the 'blimp' effect is overstated. One third the energy in LH2 gets you around half the distance as an equivalent volume of kerosene, because the volume of hydrogen only weighs one tenth the mass of the kerosene. So getting the same range means you need more volume, but you need less total energy to get you to the same destination because you're lofting less mass.

>I'm pretty positive we'll see the return of glorious, massive blimps

Na thanks i take the train ;) But for good's i could image that.

Not really, it's more likely to be stored at low temperature to avoid embrittlement. Liquid Hydrogen has an energy density of approximately 120 MJ/kg, almost three times more than diesel or gasoline. Even with the cryogenic storage and reheating equipment it has comparable power to weight ignoring electrical motor efficiency advantages. Comparable flight hours do take up 2-3x more volume than diesel (including pumps and fuel cells), but at larger sizes (e.g. 737 and larger) most commercial flight distances are limited by weight rather than volume.

A lot of things come down to scale. Small drones can run reasonable distances on LiPo, which scales very badly to larger vehicles.

Right. The strongest evidence is commercial planes will be exclusively hydrogen powered. Airbus is working on one right now https://www.airbus.com/en/innovation/zero-emission/hydrogen/... (I think 2035 is way too long - it needs to be done 10 years ago)

What more there will be hydrogen fuel plants onsite at the airports

Additionally you'll see hydrogen in similar large systems such as rail and earth moving equipment.

Honestly the only question I have in the large vehicle systems is cargo ships. There's plenty of space and benefit to large solar wings expanding the vessel surface area that can fold up when necessary

If you see the efficiency gains and cost reduction in commercial grade PV continue, it's going to be unit cost economically superior fairly soon.

Alternatively there could be some mystery device that can get a net energy gain by processing sea water to hydrogen fuel. This doesn't look physically impossible but I haven't heard of any serious efforts to do so yet and personally I'd need a lot of convincing to be assured it wouldn't just be doing a new flavor of ocean polluting

Cargo ships will go with methanol or ammonia, both of which are easy to synthesise from green hydrogen. I'm more partial to methanol since it can be carbon negative and provides a market for the tremendous amount of waste we generate, but ultimately the most effective solution will win.

Containment and leaks is a huge problem with those fuels

Millions of tons of ammonia are synthesized, handled, and used industrially every year.

That doesn't project to a guarantee of safety for all use cases.

Thankfully both our opinions are irrelevant on this.

> Liquid Hydrogen has an energy density of approximately 120 MJ/kg

8 MJ/liter for liquid hydrogen vs. 32 MJ/liter for gasoline

Size matters

Then you will use hydrogen in cases where mass is more important than volume.

You need to take tank mass into account.

Not for aviation. What matters in aviation is weight.

Air Nostrum has ordered some airships:

https://edition.cnn.com/travel/article/airlander-10-air-nost...

An amazing technology, optimizing the thing we need the least right now: rich people's private jets.

We need to fly as little as possible, not to incentivize it even more. 80% less fuel consumption? Expect people flying 5 times more, and feeling like they are doing a favor to the environment. Jevons Paradox.

I don’t understand your comment…

If, indeed, this can be made to work with a zero emission hydrogen power source, why would we seek to limit that air travel the same way we might seek to limit fossil fuel based planes ?

Are you suggesting that air travel - of any kind - is negative?

Sure, once world emissions are zero, this could be zero emission. Before it obviously comes at the expense of something else.

Yes. The core concept of progressive views is 'pain and sacrifice'. It doesn't matter who but someone should always be making some personal sacrifices for the whole to be satisfied. Some times it is plastic straws by common people and some other times it is billionaires's hydrogen jets.

Ooof. Absolute RED FLAG.

These go as follows.

---

Hey we have this AMAZING tech (supposedly). But wait, we're not going to commercialize / actually produce it even though if true it'd print money.

Look we have this (other) AMAZING tech, we are going to combine these so that's why we aren't showing Amazing Tech #1.

And repeat.

---

Most get rich books / authors / etc - if they had a way to actually beat for the forex market etc they wouldn't be selling $50/books on how to do it. Same thing here. if they had a massively efficient plane (with a prop - also efficient) they'd actually deliver.

The claims made by Celera have always been aggressive - and I hope they’re real. Why add more claims? Why not just deliver on what they currently offer?

This seems like a red flag and possibly indicates shenanigans.

They've optimized for cabin volume and all their claims are weirdly crafted to take advantage of that design choice.

For passengers who expect a flight with 4 first class-type seats, their competition isn't a minivan with wings like the beechcraft bonanza, it's a learjet with half the seats removed.

Whenever a company pivots to another tech without publicly proving the original tech, i get the heeby jeebies.

If laminar flow tech worked as they claimed, you wouldn't need hydrogen to be a market success.

Exactly what I thought. Laminar airfoils with max thickness far back do very well in the computer but they behave poorly. I would want to see proven that this plane is stable in all conditions.

Putting a hydrogen engine in it seems like a distraction.

I wonder what happened. This aircraft was designed for a piston engine, RED A03: https://red-aircraft.com/press_release/niche-company-with-a-....

>Running on an efficient 550-horsepower combustion engine, Otto claims this thing will fly six passengers up to 4,500 nautical miles (8,334 km) at cruise speeds over 460 mph (740 km/h)

That is the top warbirds' speed at 1/4th power and double range. Basically a top speed for a reasonably powered propeller aircraft. Sounds like we have a winner here. I wonder if chasing hydrogen fuel cell will add a lot of costs and risks in development and various issues for users like it can be expected with a new technology. I'm all for electric, yet i think it may make sense to separate development/products - one is extremely efficient and fast plane with already great aircraft diesel, and another - the same plane (or may be adjusted as needed) with hydrogen.

For plane engineering aware person, all ok.

- Commercial planes begin at about 50-60 seats, less are non-viable on median market (90%), but could be unavoidable or very competitive in some niches, like tractor-planes for swamps.

Normal commercial size - 100 seats.

For air-dynamics, 3 times capacity enlarge (from 6 to 18) typically possible, but more changes too much.

I imagine there's some useful information in this comment, but I found it incomprehensible.

precisely

Why waste time say lot word when few word do trick

If you are illiterate this is opportunity to learn, not reason to burn books.

A bold claim, perhaps they have done it but I have my doubts that such a large efficiency gain is left in aeronautical engineering.

And also because any time I see "% reduction" that is a bit of a red flag. Whats the math on this one?

(existing 6 passenger plane drag[cessna citation?] - (existing 6 passanger plane drag * 0.59) = celera 500 drag)?

the wikipedia article goes into a bit of detail on some of their more dubious claims.

https://en.wikipedia.org/wiki/Otto_Celera_500L

Also note how the prototype has no windows....

Very amusing wikipedia article. The only things that aren't speculative are when they started, how much funding they raised, and how many flights their prototype has had.

> A bold claim, perhaps they have done it but I have my doubts that such a large efficiency gain is left in aeronautical engineering.

It is a laminar flow design. It's been known for a long time that you can push drag down a lot below the state of the art in commerical aviation that way, and it's been used in a lot of gliders, but it doesn't come for free.

Most importantly: The shape of the aircraft is almost entirely determined by physics, not your wishes, which typically makes it quite inconvenient to build and use. Maintaining the high performance depends on keeping the skin of the aircraft very clean and smooth -- even collecting a few too many bugs can cause a lot of problems.

Gliders have a wing cord of maybe a foot or two. The body of this thing is like 30 feet long. Maintaining laminar flow across such a surface is mostly impossible. Bugs and scratches are bad, but at that size tiny paint defects would be an issue.

"This is your pilot speaking. It looks like we have some bird dirt stuck to us. We therefore must cut our journey short."

Is there really any calculation source or even equation of fuel efficiency due to battery is dead weight whilst fuel burn itself.

https://github.com/electricitymap/bloom-contrib/issues/271 This mention spreadsheet with script or pdf. Authority but not that useful for calculation.

Search for “Bernard van Dijk” on LinkedIn. He is a professor on an Aviation University. He has a very solid story about why hydrogen will never work in airplanes. I’m addition, a well explained video about it: https://youtu.be/nrCE9duCej0

I wouldn't say never, but based on the tankage requirements and tank structural needs for high pressures, it'll be limited to short range regional craft only.

There is still a lot of market in the size of things like the Q400 flown by Alaska Air. Like a Seattle to Montana flight.

An interesting video - but I am unconvinced this is "hydrogen can't work" - just the current approach won't work.

The point seems to be (watch the video) that the fuel is currently stored in wings of aircraft, which in layman's terms means the wings bend up carrying the weight of the fuselage, but the weight of the fuel is in the wings meaning fuel weight does not contribute to wing bend

Current hydrogen fuel power trains put the hydrogen into the fuselage in big tanks. This means the fuel weight now does count to wing bending and so fundamentally you can either take off without passengers or you can have your wings snap.

The answer seems to be put the hydrogen fuel in the wings. I could not find the argument against that. I suspect there is a lot more in the weeds in the industry

>"The answer seems to be put the hydrogen fuel in the wings. I could not find the argument against that. I suspect there is a lot more in the weeds in the industry "

This is impractical with current technology. The insulation for liquid hydrogen in wings would be impractically thick and heavy. The structure for pressure vessels for gas in wings would also be impractical.

Err… not all the fuel goes in the wings, and not all planes put their fuel in the wings.

This argument makes no sense to me.

I believe that all modern commercial aircraft, and many smaller ones store substantial proportions of their fuel in the wings.

Of course, but just because more weight is going into the fuselage doesn't mean the wings are going to "snap off" because the wings are empty. I mean, if the wing tanks aren't needed, surely you could replace them with structure that allows the wings to take the higher loading?

Even in the 747 and A380, the majority of fuel is stored near the wing roots, so the whole idea reads like a non sequitur to me.

The reason hydrogen in the wings doesn't work is because wings are thin and hydrogen tanks need thick walls. Also a lot more volume (hydrogen is not super mass inefficient as a fuel, but is super volume inefficient.)

Seems like you need a flying wing design so you can have gigantic wings to put your giant tanks (and also passengers) in. Maybe this https://www.nbcnews.com/mach/science/futuristic-flying-v-air... ?

This professor has a nice theory (hydrogen will never work in air planes), which is trivially falsified by simply pointing at planes that fly that use hydrogen as a fuel. That seems to have already happened. There are multiple companies that have flying prototypes.

Hydrogen planes are now an engineering and logistics challenge. The science is ancient history.

What is the deal with its windows?

Looks like the bare minimum windows needed to fly it. Windows create drag. The overall design reduces drag by "59 percent".

Would be interesting to make "virtual windows" where you take a camera on the hull and just stream its feed to like the in-flight entertainment system or a wall mounted monitor.

I would love this in cars one day. Getting into an unbearable hot car on a summer day would be a thing of the past.

That can be handled with pre-cooling your car.

...a car without windows would get hotter than one without because windows are at least somewhat reflective (depending on the angle of the sun) and because they can be left cracked open to let the heat escape.

The first half of your supposition is dead wrong, but the second half is correct. Opaque materials will always transmit less solar energy than transparent materials. The most effective insulated multi-pane windows available for homes today are still less efficient than a wall.

Yes, light travels through glass and not through metal and paint.

But if the outside of the car gets hot, the inside will too.

On a sunny day, why are the contents of my trunk cooler than the interior of my car?

It's kind of a weird idea to get used to, but I think windowless cars could be pretty cool. Maybe the driver puts on a VR helmet and can see everything. (Obviously the technology would have to be extremely reliable.)

It solves a bunch of problems: it gets rid of all the trade-offs between structural integrity and visibility. It reduces costs and makes manufacturing easier. The driver could be anywhere, even in the back seat if that makes sense for some reason.

This seems like it would be extra useful for military vehicles. I wonder if you were to redesign something like the A-10 or F-16 from scratch and you could put the pilot anywhere you want because visibility isn't an issue, would you come up with the same design or would the cockpit end up somewhere strange, like in the back of the plane?

I did a napkin math a while back: the standard for 20/20 vision or 1.0 acuity scale equals to 1 arc minute resolution, or 1MOA, or an Euclidean angle of 1/60th degree.

A spherical VR image that resolves to 20/20 acuity is as large as (60 x 360, 60 x 180) = (21600, 10800)px before requisite oversampling, and that’s kind of hard. Then of course those fighter guys has/need better visibility than 20/20 which only makes it harder.

And by the way modern digital image pipelines buffer and delay transfers, sometimes as much as 200ms, which is absurd considering the CPU runs at literally millions of times better clock frequencies and latencies, but that’s what readily available implementations are.

These mean that we are still some time away until such “local remote driving” not just complements but totally replace heat formed and dielectric coated pane of plexiglass.

I guess it eventually will beyond upper edge of atmosphere as glasses don’t work well and vision required surpass human eyeballs, i.e. in interstellar settler’s carriages and planetary orbital fighter jets, but for now and for forward windscreen applications, it makes more sense to just put on panes of plain old transparent aluminum.

Some passenger jets have had this for a while, giving you various views from the seatback screen. Not sure which airlines or jets but I've definitely heard of it.

Airbus A380 has this in first class.

A similar camera was present on the old DC-10. AFAIK, it was removed after an pretty big crash in Chicago. Nothing to do with forthrightness, iirc (outside of the usual flying coffin perception of the DC-10).

EDIT: https://en.wikipedia.org/wiki/American_Airlines_Flight_191

Looks like it was a cockpit camera, not an external camera.

I was on an Emirates flight that had this.

I absolutely loved the few times I was in a plane that had a forward and downward facing camera that you could watch on the screen. So great to just watch it for hours. Windows are nice but in most transatlantic flights they are all closed the majority of the trip so that people can sleep.

How about no? A camera doesn't give you the same view as a window does. You can't move around to get different angles. Not to mention the pixel resolution of in-flight entertainment is nowhere near what you get with your eyes. Looking out the window at the sights is one of the few great things about flying.

I don't know, I've been on flights with webcams on the nose/tail/belly and found those to be pretty entertaining. And it's available to every passenger, not just the window seats. If an airplane design really leaned in to the webcams, I think it could be fantastic!

Put aside controversies, I believe the window requirements are for rescuers to scout the cabin in a crash than for occupant entertainment. Else makes no sense to have window shades open during takeoff & landing.

Windows themselves don't create drag, it's the interruption of the surface that creates drag. If they do a very good job of getting the windows put in, it shouldn't be an issue. The bigger reason is: it's a prototype, so it's easier not to cut the windows out and fill them with glass.

Why do they create drag? Is it difficult to make them flush with the exterior of the plane?

I guess the main problem is weight. 6-10 windows might weight ~100 kg, and you'll need more aluminium in the frame because of more complex structure.

The final version will have passenger windows, this is just a prototype.

They're doing something that's a red flag IMHO by talking about a fuel cell version. If you've got a great idea - and 80 precent less fuel consumption should qualify - then bring it to market. Every additional "revolutionary" concept you add increases the risk of a new product never materializing. Next up, an all new material and manufacturing process... 3D printed crypto nanotube/metal composite!

I assume they’re just taking free money from a third party to subsidize their main development. If the fuel cell partnership works then great otherwise no big deal.

Wouldn't a flying wing design be more efficient? I'm suspicious this comes down to engineering a big-enough pressure vessel into the wing design.

Also good luck landing this thing with strong crosswinds. Or god forbid rupture the pressure vessel with a hard landing... It's an interesting concept but looks very impractical.

Possibly. Though functionally this isn't much different from a flying wing, as the fuselage is a lifting body. It's basically like a large capacity powered glider.

No. Flying wings do not allow for efficient internal layout of passenger seats, cargo areas, and engines. You're better off designing something with minimal wing drag and a body that provides additional lift.

Now we need more hydrogen vehicles!!

is there an airport anywhere that stocks hydrogen fuel?

Why would they? There are no planes to fuel yet.

Most efficient small-scale prototype of a passenger plane... title is way overselling the article.

Edit: All of the photos are of the smaller prototype... and I missed the text saying they had a full-scale one. Oops.

In the article, it says the it's a full-scale prototype. Still agree the title is overstating it, especially since they explicitly say the design cannot be used for an airliner.

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