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.
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.
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.
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.
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.
> 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 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.
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%...
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.
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".
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.
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.
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.)
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.