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Everybody always focuses on the Hindenburg, but it's not as though helium airships were much safer. In some scenarios they were marginally safer, but the deadliest airship disaster of them all was the USS Akron, a helium airship. 73 dead and 3 survivors, vs the Hindenburg's 36 dead and 62 survivors.

As for marginally safer: There were some cases of helium airships breaking up due to weather and people surviving the ride to the ground on still somewhat buoyant sections of the destroyed airship, whereas that was less likely with hydrogen airships because the wrecks would also burn. Compare the crash of the USS Shenandoah to the British R101; both were destroyed by bad weather but R101 had far fewer survivors because the wreck burned. But even with helium, airships are still very fragile and dangerous. Using helium isn't truly a panacea to the hazards of airships.

> But even with helium, airships are still very fragile and dangerous.

True. But with high speed landing and takeoff aeroplanes are extremely dangerous too.

Thousands of gallons of high octane fuell in the tanks on board does not help

> high octane fuel

Doesn’t jet fuel have a relatively low octane rating compared to most liquid fuels?

Yes, but I think he's using it in the colloquial sense that means "highly energetic".

It depends on the plane, but both your point and the parent point are correct.

Piston engines run on high octane gasoline (Avgas) . This is the stuff that powered planes up to, and just past, ww2. Today it's still used in planes from that era, and some smaller general aviation planes.

Jet fuel (jet a1) is basically paraffin. All turbine engines (think "jets", but also turbofan etc) run on this. It's a lot less flammable than Avgas, but, well, still makes a big bang if you fly it into a mountain.

In short both are dangerous because they are high-density liquid energy. Hydrogen is also dangerous, and there does appear to be a double standard here.

You can dump plane fuel before an emergency landing, making the whole process safer. it's not just double standards.

Yes and no, but mostly no.

Planes dump fuel to get below maximum landing weights. This typically happens when planes encounter an issue right after takeoff, and need to return to the airport.

There are two kinds of emergency landing - those that happen in a hurry, and those that happen slowly.

If it happens in a hurry there's no time to vent fuel. If it happens slowly fuel can be vented, but typically just enough to get below max landing weight. It's not like they "empty the tanks".

> Hydrogen is also dangerous, and there does appear to be a double standard here.

I don't have beef with hydrogen, but I suspect it's a lot easier to secure fuel in a liquid state versus a gaseous state. Putting a lot of hydrogen in a relatively small steel container for use in an engine seems quite a lot safer than putting it in a big bubble and then dangling people from it. But I am not an aerospace engineer, could be wrong, etc.

I too am not an aerospace engineer, but venting hydrogen after touch down seems easy enough. After all if you open the cells the gas just goes away.

By contrast a broken fuel tank leads to liquids spilling on the ground, which seems like fun.

That all said, liquids don't explode, gasses do. So if you were unlucky and the hydrogen exploded then life would get very exciting very quickly.

> That all said, liquids don't explode, gasses do

There may be a technical definition of explosion that says an exploding tank of fuel is not "exploding". Do you care?

A ball of fire is an horrific thing

It's probably helpful to ignore Hollywood here. We see exploding cars all the time, but in real life cars don't explode.

They can burn of course, and a fireball is a fireball, but an explosion creates shock waves, and all kinds of ancillary damage. Recall the Beirut explosion recently - the fire was relatively contained, but the damage from the explosion is vast.

So yeah, talking about gasoline here - the liquid doesn't explode, it burns. However the gas (as in gas, not liquid) can explode, rupturing the tank and spraying burning liquid everywhere. The worst case is a tank mostly empty - the fumes explode, spraying the rest of the liquid. The best case is a full tank. Liquids can absorb a lot of heat, without expanding or creating pressure. Once they boil though (which requires that the liquid doesn't already "fill the tank", pressure builds leading ultimately to the rapid disassembly of the container.

Incidentally this is why throwing an _empty_ aerasol can on a fire is very dangerous, possibly more dangerous than a completely full one (depending on the contents).

But to your point, and explosion and a fire are very different animals, with very different outcomes.

I don't know the statistics, but a damaged and leaking LPG cylinder seems more dangerous than leaking kerosene or gasoline, because the gas boils off and leaks itself.

Here's what happened 10 years ago: https://www.youtube.com/watch?v=FG1LGKieTxY

I understand that it's just reckless driving. And had this been a gasoline tank, it may have burned as well, but at least no cylinders would have flown around.

Though, its still seems safer than pressurized methane. 300 bar make cylinders explode, probably from material fatigue. It doesn't burn, because decompression makes it super cold, but still, the car is ripped apart. https://www.google.com/search?q=%D0%B2%D0%B7%D1%80%D1%8B%D0%...

Yes, but this octane-fire mixing is a bunch of confusion to begin with.

Gasoline is less ready to ignite than diesel~=jet fuel, but has fumes.

Diesel~=jet fuel has little fumes, but is easier to ignite by heat, i.e. in an engine, but it will almost never be ignited outside of an engine. Meanwhile, gasoline is hard to ignite with heat and pressure in an engine, but easier to ignite in air than diesel.

Octane also has a higher boiling point than for example heptane, so higher octane fuel is probably not related to easy of ignition due to the fumes either.

The situation's more complicated than that.

Gasoline is easier to ignite than diesel fuel.

Both fuels burn as vapours rather than as liquids. The vapour pressure of gasoline at any given temperature is higher than diesel, that is, gasoline evaporates far more readily, making liquid gasoline far more hazardous to store, as the vapours can ignite and explode.

Diesel fuel resists autoignition under compression to a greater degree than gasoline, and so can be used in high-compression engines without spark ignition.

The flash point is the temperature at which vapours of a fuel can ignite given a spark. These are given for various fuels here: <https://www.engineeringtoolbox.com/flash-point-fuels-d_937.h...>

For gasoline: -42.5 C / -45 F

Diesel: 37.8 -- 54.4 C / 100 -- 130 F (depending on grade)

Kerosene / Jet Fuel: 37.8 -- 72.2 C / 100 - 162 F

Yes, the autoignition temperature of diesel is modestly lower than that of gasoline, but in practice the principle concern is vapours igniting from a spark rather than net ambient temperature reaching the autoignition point.

(I'd expected gasoline to have a lower autoignition temperature than diesel, this was a surprise for me, though multiple sources seem to indicate a lower ignition temperature for diesel. I learned something researching your comment.)

The autoignition point of various fuels is given here: <https://www.engineeringtoolbox.com/fuels-ignition-temperatur...>

For gasoline: 246 - 280C / 475 - 536F

Diesel: or Jet A: 210 / 410

Kerosene: 210C / 410F

Ah, I was actually trying to express precisely what you're saying here, and don't immediately see the difference between the views we're laying out.

Even with the Akron, we're focusing on the first disaster and not on the improvements or possible improvements since then.

Akron crashed into the Atlantic in April. "Most casualties had been caused by drowning and hypothermia, since the crew had not been issued life jackets, and there had not been time to deploy the single life raft."

Followed by: "Macon and other airships received life jackets to avert a repetition of this tragedy. When Macon was damaged in a storm in 1935 and subsequently sank after landing in the sea, 70 of the 72 crew were saved."

The R101 was a stupid tragedy - they designed and built it, then extended it, then launched the first flight without sufficient testing to learn how the extension had gone and how it handled after, in poor weather conditions, because the launch date had been decided by politicians as a piece of propaganda about reaching the far corners of the British Empire by airship.

> Followed by: "Macon and other airships received life jackets to avert a repetition of this tragedy. When Macon was damaged in a storm in 1935 and subsequently sank after landing in the sea, 70 of the 72 crew were saved."

Yeah, but notably they hadn't solved the problem of wind tearing airships apart.

In the case of Macon they landed gently and in warm water, and lifejackets certainly helped. But a soft landing is by no means a guarantee in any airship crash, and even with most people surviving the Navy still lost their investment in the airship because of some wind. Putting lifejackets on an airship flying over water should be common sense, but it only makes the airship marginally safer. It's hard for airships to be viable when they're so prone to tearing apart and falling out of the sky.

I think his point is that most of these are measurable, concrete problems that can be solved or mitigated enough to be considered "safe," in the same way airplanes have all sorts of risks and issues we solved or mitigated to make them safer than the cars many use every day.

The way I see it, aircraft have become mechanically reliable and airships could become mechanically reliable too. But airships will always be structurally vulnerable relative to aircraft. They're inherently very light with very large surface areas and there's no way around this.

The strength to weight ratio of a carbon fibre scaffolding would be far superior to steel.

Isn't the clothy stuff the problem though rather than the scaffolding?

Same on most sailboats: what makes them get into trouble is not the hull cracking but rather the sail tearing up in a storm or the mast snapping off and making them uncontrollable / sink.

(Im guessing out loud here, statements probably wrong)

Mast snapping happens. Rudder snapping off is also bad. Often the issue is running into rocks/a reef due to a navigation failure. Sails do tear, but for sailboats I don’t think it’s as simple as the clothy bits being the main weak point. I don’t know about airships though.

If the clothy bits tear on a sailboat it’s an inconvenience. When the hard bits (eg keel) fail, it’s a problem.

For airships, the entire structure (frame, envelope, gas bags) are at the limits of materials engineering. Failure of any of the components is both likely and catastrophic to the craft.

There's actually no need for hydrogen. Helium would do just fine. From the blog post, filling the hypothetical airship with helium would cost $8 MM, while filling it with hydrogen would cost only $100k. Sounds like a no brainer. But, the overall cost of the airship would be at $100 MM. Hydrogen would result in a less than 10% cost reduction.

Now, the FAA approved unleaded jet fuel in 2022. Yes, that's how conservative FAA is. We'll sooner achieve world peace than the FAA would approve hydrogen for airships.

Preventing the helium from leaking out of wherever its stored is challenging, it's not a "fill once and forget about it" kind of deal. Helium is bound to get more expensive too.

Helium is a non-renewable resource drilled out of the ground, of which there is a global 'crisis' shortage[1]. Hydrogen is easy to make in vast quantities and cheaper. But more importantly, while they have similar lift capacities on paper (Helium ~90% of Hydrogen), in practice they don't - https://www.airships.net/helium-hydrogen-airships/ has an explanation and calculations.

Hydrogen lift airships set off fully inflated and vent Hydrogen along the way for control of altitude and to stop their lift cells expanding too much as they rise into lower pressure air; Helium is too expensive to vent casually, so they have to start less inflated to protect the lift cells, and other concerns so Helium lift ends up with half the payload carrying capacity, less fuel, shorter flight distances.

And, nb. the deadliest airship disaster was the USS Akron which was was a Helium lift airship which crashed in a storm with 73 deaths and 3 survivors. It's not as simple as Hydrogen = danger, Helium = safe.

[1] https://www.forbes.com/sites/omerawan/2022/11/10/the-helium-...

If fusion power takes off, could you produce helium as a by-product?

if we figured out fusion, it would alter the economics of all of this

why not fusion powered ships/trains/airplanes

> why not fusion powered ships/trains/airplanes[?]

What could possibly go wrong?

We already have fission powered ships and submarines.

We almost had fission powered airplanes and airships: https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

and https://en.wikipedia.org/wiki/Lockheed_CL-1201

And dreams of fission trains: https://twsmedia.co.uk/2020/05/09/atomic-trains/

Sense prevailed, and we do not have civilian mobile nuclear reactors.

The military are mad. Mad and bad. It is in the job description.

We would all be better off if none of them (the military) existed

Afaik what makes fusion hard is maintaining the conditions that allow fusion to occur. Because of this, it’s quite safe - if anything goes wrong, it’ll just stop working.

Safe? Really?

I expect that the containment vessels will get very radioactive.

But all a bit hypothetical, since none exist

Yes they do exist, link elsewhere in this thread, Helion have a 7th generation nuclear fusion reactor fusing once every ten seconds or so. https://www.youtube.com/watch?v=_bDXXWQxK38

(It's not surplus of power, but it is repeatable fusion actually happening).

That is not a fusion reactor

There's a fusion startup called Helion near Seattle working on this, it'll be really exciting if it pans out at scale.

This video was a fascinating watch: https://www.youtube.com/watch?v=_bDXXWQxK38

Basically, no: https://www.jerf.org/iri/post/2922/

And that assumes perfect capture, too.

If you're going that route it'd probably be better to just use hot air with the energy.

Nice! Thanks.

Probably, but the amount would be tiny. ITER is trying to generate 500 megawatt from a half-gram of hydrogen.

Yeah hydrogen sounds like it could even be safer given that you get a larger buoyancy buffer to fight downdrafts? It's a real public misconception that it just explodes from all those oxyhydrogen experiments at chemistry class, but pure hydrogen such as in airships just slowly burns, much like any other fuel we fill our planes with.

The main problem is still that you need to contain a large volume, which will inevitably get pushed around by wind more than you can compensate for.

I wonder if you could use a fuel cell to get power from the hydrogen you'd otherwise vent.

You may have overlooked the part where filling the quantity of airships that would (theoretically) be used would represent over half of the KNOWN quantity exploitable on earth, and would take decades to produce at current production rates. Also, they would need topped up over time. Compared to hydrogen, which is cheap, available, and renewable.

> KNOWN quantity exploitable on earth

It's great that you emphasized "known".

Knowledge is not a static thing. Also what's economically exploitable is a variable thing.

Currently, the US produces 40% of the world's helium, despite producing only 25% of the world's natural gas. Is it because the US has drawn a lucky lottery ticket for helium?

That's very unlikely. Helium is being produced continuously inside Earth as the alpha particles generated during the radioactive decay of some elements (mainly Uranium and Thorium, but Radon too). It seeps upward, and it generally escapes in the atmosphere, but some of it gets trapped in the same geological formations that trap natural gas.

In most places people don't bother to see how much helium there is in natural gas. They just sell the gas and take the money. Separating helium can increase the profitability a bit, but it depends on how cheaply you can do the separation. It's very likely that the US has better technology than the rest of the world, and because of that it separates more helium for the same quantity of natural gas.

As the technology will spread out, more helium will become recoverable.

Also, it may come as a tautology, but more helium is economically recoverable if its price goes up.

As a noble gas, helium can't be synthesized, so its cost is because of its scarcity— and because it's a small molecule (like hydrogen), you inevitably lose some and require continuous top-ups.

None of this sounds like it would be realistic at scale, no matter the amount of money in play.

The FAA approved modifications to piston engines to use unleaded avgas. Jet fuel doesn’t have lead.

Also, this isn’t about the FAA just being slow for no reason. Switching from leaded to unleaded without the engine modifications was not safe for the piston aircraft that need it.

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

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

It's not safe for us to be breathing. But that doesn't matter to cheapskate rich private plane owners or their regulatory-captured FAA.

The really rich private plane owners all have planes that burn jet fuel, which is always unleaded. The piston planes are generally owned by "doctor rich" upper-middle class people, who have political influence to be sure but they're hardly the billionaires that might be known by name to politicians.

I think it's more likely that the FAA protects general aviation because general aviation is part of the professional pilot training pipeline.

The people that are below “doctor rich” just rent their planes from the FBO, a cheap piston plane can rent for $125-$175/hour. So you can get in a couple hours of flying for what it costs a couple to go to a football game.

Nothing is stopping the EPA from banning it regardless of what the FAA wants. The FAA doesn’t regulate emissions.

Lift gas is a consumable. You have to vent it to descend in many cases, and that’s ignoring the inevitable leaks and diffusion.

> Lift gas is a consumable. You have to vent it to descend in many cases, and that’s ignoring the inevitable leaks and diffusion

Helium blimps compression the gas to lower buoyancy

So, if filling your gas tank cost 8% of the price of your car... you'ld think nothing of it? Lift gas leaks (esp He) and gets vented. So this seems odd to me. It's kinda like buying your car again every few months to a year or paying $250/gal to fill up. Now 80x lower at 0.1% of the car price you're in the regime where it's negligible like an EV.

> Lift gas leaks (esp He)

Hydrogen more than helium, I believe.

Each Hydrogen molecule is more reactive, but actually a larger molecule (less leaky) because there are two (it's diatomic H2 rather than monoatomic He).

Now it does get complicated, because the simple atomic radii aren't sufficient when you start bouncing around and leaking through other materials, but suffice it to say that He is still smaller once you look at the Vander Walls attraction and everything. It may only be 10% smaller, but that leads to at least a 20% lower leak rate.

https://bbblimp.com/2021/09/17/helium-vs-hydrogen-atom-size/

Author mentioned a market for 25K of these airships, which is like half the helium on earth the first time you fill them up. $8M will go up once you start building

> Helium would do just fine.

Though that creates another problem: there is a shortage of Helium developing that is starting to cause concerts in a few places (like medical imaging, which it is used as a coolant for devices like MRI scanners). That $8E6 might grow significantly not long after the first airships roll off the production line, and it'll raise for other users significantly too as available supply becomes more contested.

> There's actually no need for hydrogen.

The Hindenburg was originally designed with Helium in mind, but because of a US export ban (at the time Helium was in even shorter supply, and most of it was being produced from resources in the US) forced a redesign.

Unless new practical+affordable sources are found, the same sort of design limitations could strike again.

Aircraft today are so safe because we had decades of improvements in both engineering and safety regulations. I am adamant that we could improve reliability and reduce potential damage in accidents so as long as we apply the same principles to airships.

Aircraft survive because they're mechanically reliable, and airships could also be made mechanically reliable. But aircraft also survive because they're reasonably robust in adverse environmental conditions. Airships aren't and never will be, because they have to be built very large and very light or they don't work at all. Furthermore airships are slower and harder to hanger, which makes it even harder for airships to avoid bad weather. Better weather forecasting could help some, but keeping airships out of storms really is of the utmost importance.

I guess the last time was in 2013. Asiana Airlines Flight 214, a Boeing 777 jumbo jet, crashed at SFO with only 3 fatalities. Those are tough airplanes and low-speed crashes are often survivable if passengers can evacuate before the inevitable fire spreads.

https://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214?wpr...

It was kind of freaky seeing the burned-out wreck sitting next to the runway when I flew out of SFO a few days later.

I was going to say that the 777 isn't a jumbo, but it looks like they're now calling it a 'mini jumbo'. Feelings of inadequacy, I guess, compared to the 747.

Meh, terms like this are pointless. Completely arbitrary where you put them.

It's probably more sensible to use terms like wide body, implying 2 aisles.

People often forget that the metallic paint used to coat the Hindenberg is now used as solid state jet fuel.

> What if some of those "flew into a mountain", "engines failed", "mid-air-collision" had been captured on video

I'm now picturing how each of these situations would look with airships.

Most of them, in my mind, make a very nice "Boink" sound.

My guess is the relevant sound is rrrrrrip.

airships have multiple cells though, a single rip wouldn't doom the entire thing

But what caused the airship to rip? If it was wind, then you now have that same destructive wind ripping through the inside of your airship through the hole.

I mean, I was specifically talking about the collision scenario...

Even still though, you'd come down to the ground for a soft-ish landing (relative to a jet or helicopter, anyway).

You have to multiply by the respective probabilities of both of these things happening to arrive at the expected number of deaths. 0.01*(35/97) would be significantly bigger than 0.000001*(97/97), as a hypothetical example.

That said, planes have had years of safety R&D which helps get that number down to 0.000001, and maybe the same could have been done with blimps if they were given the opportunity?

The Graf Zeppelin, one of the Hindenburg's contemporaries, flew regularly accross the Atlantic, flew into the Arctic Circle and exchanged mail with a ship there, was the first vehicle to fly around the world and set a round the world speed record, was the first vehicle to cross a million miles flown, did 590 flights, carried 34,000 passengers, and did so with no harmful accidents and no fatalities, despite losing four engines on one flight and needing a forced landing.

Yes I imagine something similar could have been done in the last 70 years if they'd kept being built en-masse.

https://en.wikipedia.org/wiki/LZ_127_Graf_Zeppelin#/media/Fi...

> (NB. people now want aircraft which can legally be pushed horizontally by hydrogen, but cannot legally be pushed upwards by hydrogen.)

I laughed out loud when I read that, thank you!

I completely agree. In addition to that, the Nazis neglected a lot security measures that this aircraft actually had in place. There's a nice episode of "well there's your problem" on the Hindenburg: https://www.youtube.com/watch?v=chlF5oubFHU