Caltech professor helps solve Hindenburg disaster
caltech.edu
caltech.edu
Imagine a tin cigar filled with explosive gas! Combine that with oxygen from the air, and a source of ignition, and kaboom! Today we call those "airliners".
If people had continued to develop Zeppelins, the problems with safely handling hydrogen would have been solved, just like the problems with handling aviation gas and jet fuel have been solved. There's a lot of consideration with airliners about dealing with lightning strikes and all sorts of possible sources of sparks so the fuel is not ignited.
What we have naturally comes from radioactive decay deep in the earth. This will continue for some time, but it's a fixed, slow rate.
Helium evaporates into space. Once it's gone, it's gone for good.
The other options we have are hydrogen (extremely reactive), heated oxygen (also reactive), methane (reactive), ammonia...
It's a hard problem.
https://physics.stackexchange.com/questions/71027/is-it-poss...
Nitpick: So is hydrogen.
More precisely, helium is an element that doesn't readily form compounds. Hydrogen does, and as such can be extracted from, say, water via electrolysis.
The secondary issue with helium is that it's much lighter than air -- this is why helium and neon are both much rarer than, say, argon (which is actually the third-most common element in the air after nitrogen and oxygen).
Actually, hydrogen is lighter, and so a better lifting gas, than helium.
He: 0.1786 kg/m^3
H: 0.08988 kg/m^3
Air: 1.225 kg/m^3
Air vs He: 1.0464 kg/m^3
Air vs H: 1.13512 kg/m^3
To put it differently, for helium, the lift is about 86% of the weight of the displaced air, while for hydrogen it's 93%.
Both very good, and both are much better than hot air!
(which gives a lift of only about 25% of the weight of the displaced air, at typical temperatures of about 120 deg C)
> In a practical dirigible design, the difference is significant, making a 50% difference in the fuel-carrying capacity of the dirigible and hence increasing its range significantly
But I wouldn't know :)
> While helium is exceedingly light as compared with air, it is somewhat heavier than hydrogen. The total lift of a helium-filled dirigible is accordingly some 10% less than that of the hydrogen-filled airship. The difference does not appear important at first sight, but the total lift of the gas carries the structure, the motors and the crew. It is only the last 20% or so that is available for carrying fuel, and hence a difference of 10% in the gross lift may spell a difference of 50% in the fuel-carrying capacity. On long-distance flights this difference is vital.
> Nor is the danger of fire totally eliminated with the use of helium; the gas-tanks and the fuel system generally are still vulnerable. But when a ship is properly designed and carefully handled, the danger of fire is comparatively small, even with hydrogen.
https://web.archive.org/web/20110209024932/http://www.time.c...
No.
Hydrogen is highly explosive/flammable — that is why Helium is preferred.
But that doesn't significantly impact rarity of hydrogen, as it reacts very readily and is typically found in compounds.
You don't find much hydrogen gas in nature (~1ppm in the atmosphere, vs 5ppm for helium).
Better the hydrogen, a few small technical problems aside.
Gravity also matters here.
On the other hand, zeppelins like the Hindenburg were literally just filled with Hydrogen. It was a fundamental part of the design; they hydrogen provided the buoyancy needed for the vessel to float. The vessel and the fuel tank were one and the same. Moreover, there isn't a way to design a hydrogen-based zeppelin that can both use hydrogen for buoyancy and hold it safely; even today containers for gas hydrogen are bulky and heavy. The solution is simply not using hydrogen.
> Moreover, there isn't a way to design a hydrogen-based zeppelin that can both use hydrogen for buoyancy and hold it safely; even today containers for gas hydrogen are bulky and heavy.
Of course there is a way. The Hindenburg's dialectric problem could have been solved. It's frankly incredible how good we have gotten at making airliners safe despite being pretty much a flying bomb. See the 9-11 films of what happens when two of them, loaded with jet fuel, hitting a skyscraper. Those fireballs weren't from materials in the buildings.
This is a false statement.
As I understand it this is inaccurate -- there is an aircraft frame (made of aluminum) with canvas stretched around it. Then inside that frame there are gas bladders filled with hydrogen. Short of a very intense electrical discharge that would jump the gap, there is no electrical connectivity between the outer skin/frame and the inner bladders. And the bladders in turn were designed to vent upwards in the event of an emergency to prevent exactly this situation, since hydrogen is not an explosive gas unless it is sufficiently mixed with oxygen, which is hard since it will disperse rapidly in air.
One thing often overlooked about the Hindenburg and its reputation as being a dangerous bomb with people hanging below it is that there were a substantial number of survivors -- out of 97 passengers/crew, 62 survived.
I think the GP is probably correct that had not development stopped, we would likely have very safe storage for hydrogen at that scale; like the hybrid helium/hydrogen mechanisms originally intended for the Hindenburg class.
Hindenburg wasn't the deadliest airship disaster, it was just the final straw. It's the best known of the crashes because it was highly publicized and the last. The USS Akron crash killing 73 of 76 crewmen. There were no survivors from the 52 people on the Dixmude. 44 of 49 died in the R38 crash. 34 of 43 died in the Roma crash. 48 of 54 died in the R101 crash.
https://en.wikipedia.org/wiki/TWA_Flight_800
The probable cause was a spark in the fuel tank.
https://www.powermag.com/lessons-learned-from-a-hydrogen-exp...
and this:
https://www.youtube.com/watch?v=vVyZeSgxmsw&t=74s
The thing Lindbergh was most afraid of in his transatlantic attempt was the fuel load. His predecessor died in a huge fireball on takeoff.
You can put a match out in a jar of jet fuel at room temp. (Start at 1m30s: https://m.youtube.com/watch?v=7nL10C7FSbE )
The idea that jet fuel is safe and doesn't burn in crashes is very, very false. Remember those fireballs when jets crashed into the World Trade Center?
There is a clear spectrum of flammability/explosiveness in which hydrogen, gasoline, and jet fuel are sorted in that descending order. That's what several posters are saying.
An explosion has a reaction front moving faster than the speed of sound. A deflagration is a rapid combustion, but without the shockwave.
Sufficient quantities of aviation fuel --- in the case of piston-powered craft, petrol rather than the heavier and less volatile kerosene of jet fuel --- especially when mixed with or dispersed through air will burn quite vigorously. Unless specifically contained, they won't actually explode. Even combustion at high pressures within a piston's cylinder is more a combustion than explosion.
Yes, if exposed to air, hydrogen will mix itself more readily than jet fuel will, but it is also much less energy dense, so it will burn out quickly and cause much less damage. A Hindenburg could not have brought down the World Trade Center buildings.
If you have hydrogen sealed in a fireproof bag of some sort, you can heat the outside with a blowtorch, send giant electric sparks through it, etc., and no explosion if the bag doesn't rupture. Because it's not explosive. If it does rupture, no explosion, but the gas will burn as it rises into air with oxygen that hasn't yet been consumed.
I imagine (would have to be rigorously proved, of course) that if you compartmentalized hydrogen in lots of bagged "cells", and the cell membranes were designed so that even if the neighboring cells all ruptured, encountered air, and burned, the heat would not be enough to rupture an unruptured cell, you could have a safe hydrogen airship. It might even be less vulnerable to certain dangers (ex: shoulder-launched terrorist missile) than an airliner.
Now imagine a metal aircraft full of fuel with a cargo of wheat--if you dare. Oh the humanity!
Wheat is scary in a silo, but in a 50 lb bag not so much. I liked the cell engineering idea with hydrogen - not sure of weight / etc tradeoffs.
You're safer crashing a glider full of TNT and lit sparklers than a jet full of fuel.
All the videos on YouTube of hydrogen-filled balloons (yes, pure hydrogen, not HHO) disagree with you.
Not sure I'd want to cross an ocean in a Zeppelin, but I think I'd enjoy a quiet leisurely one week flight safari over the Serengeti, Ngoro Ngoro, Kruger, and Okavango Delta, for example. Particularly with panorama windows and a lounge and fine restaurant and bar. Pity.
Both crashed after a few years in service, in weather related accidents (with significant loss of lives in Akron case).
These two examples are not isolated cases, several zeppelin crashed in similar circumstances.
Replacing H with He solves part of the safety issues with zeppelin, but not the main source of accidents. Given how high the susceptible to weather is, due to the inherent size an light weight of zeppelins, I don't think we will see a large zeppelin being built in the foreseeable future, despite all the projects around these.
"Despite a U.S. ban on the export of helium under the Helium Control Act of 1927, the Germans designed the airship to use the far safer gas in the belief that they could convince the US government to license its export. When the designers learned that the National Munitions Control Board refused to lift the export ban, they were forced to re-engineer Hindenburg to use hydrogen for lift."
Explody lift gas is only one of numerous failure modes of lighter-than-air craft. Handling in winds, structural stability (the frames are at the very limits of material science), limited lift capacity (the only very slightly greater density of helium has a disproportionate impact on payload capacity reduction), all impose severe limits.
Wishing away problems doesn't.
In the end I folded the bag around a military-grade flashbang (which has magnesium). That worked.
What that means, is that if the Germans had use slightly conductive spacers rather than wooden dowels, they would have been able to keep the voltage difference between the frame and the envelope below the dielectric breakdown point of the gap. At the cost of the sparks happening at the ends of the mooring ropes as they touched the ground.
Another useful experiment if you still had a zeppelin would be to see if you could usefully use the voltage differential to do some useful work (like flashing lights on the sides of the ship or something)
Or was it that there has never been any leak across the whole structure when docked in wet?
Alas, Airship Ventures went out of business about ten years ago, due in part to the loss of a corporate sponsor and no luck getting a new one. I remember seeing 23 and Me on the zeppelin when it flew overhead.
Ten years ago, a good friend treated me to a ride on one of their last local flights (this time the zepp was decorated with the Farmers Insurance logo). They still fly in Germany, though, so if you are ever in the Friedrichshafen area and can afford the somewhat pricey flight, do it! I promise you won't regret it; it was truly an experience of a lifetime.
I posted a couple of comments here in the last year or two, so rather than repeat all the details and photo gallery, you can find them here:
https://news.ycombinator.com/item?id=21662645
https://news.ycombinator.com/item?id=18897492
p.s. These new Zeppelin NT airships do use helium!
https://www.dailymotion.com/video/x2ncm5i
The OP article pretty much takes the flammability of the doped skin for granted. The "distributed capacitor" theory certainly would account for the rapidity of the fire spread, with multiple ignition points.
Update: nvm, just found this: https://www.airships.net/hindenburg-paint
At least, those who used to make model aircraft with balsa wood and dope.
It's also available as an audio book on youtube [0]. (I couldn't find it as an audio feed)
[0] https://www.youtube.com/watch?v=97OnTDaLqqk&list=PL0INsTTU1k...
From another article, about a 1916 German bomber .. https://eandt.theiet.org/content/articles/2017/11/eccentric-...
> First, Cellon, a type of cellulose acetate, was highly flammable, which, combined with the wooden fuselage, made the plane a tinderbox. Secondly, it wasn’t very strong or stable; in dry weather the material shrank, warping the wooden fuselage, while in damp weather it expanded and made the whole structure sag. This had a very unnerving effect in flight, as the control surfaces changed characteristics from moment to moment depending on humidity. Cellon also decayed in ultraviolet light, becoming yellowed, brittle and prone to explosive shattering.
> The truth is that the dope used on the Hindenburg was specifically chosen for its low flammability, and the composition of the dope had almost nothing in common with the formula used to make rocket fuel.
Cellulose acetate has lower flammability but that isn't saying much.
Have a look at the Pathé video of the Hindenburg disaster. The "skin" is clearly on fire.
> they concluded the Hindenburg's demise could be attributed to both the hydrogen and the paint,
which is what I'm suggesting.
This is useful: https://iafss.org/publications/frn/19/-1/view/frn_19.pdf
"TITLE: FLAMMABILITY AND FLASH POINT OF CELLULOSE ACETATE FIlM CONTAINING VARIOUS AMOUNTS OF CELLULOSE NITRATE" 1952
”Reinforced aerostat technology for safe hydrogen use in airships”: