[HN Gopher] Caltech professor helps solve Hindenburg disaster
___________________________________________________________________
Caltech professor helps solve Hindenburg disaster
Author : chmaynard
Score : 66 points
Date : 2021-05-17 19:44 UTC (3 hours ago)
(HTM) web link (www.caltech.edu)
(TXT) w3m dump (www.caltech.edu)
| chmaynard wrote:
| My compliments to the writer of this story, Emily Velasco. She
| clearly communicated the science and still managed to keep the
| reader (me) on the edge of my seat.
| emmelaich wrote:
| I wonder whether the Cellon dope caught fire first. It's highly
| flammable and unstable.
|
| 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._
| js2 wrote:
| This still leaves part of the disaster unanswered:
|
| > Regardless of the source of ignition or the initial fuel for
| the fire, there remains the question of what caused the rapid
| spread of flames along the length of the airship, with debate
| again centered on the fabric covering of the airship and the
| hydrogen used for buoyancy.
|
| https://en.wikipedia.org/wiki/Hindenburg_disaster#Rate_of_fl...
|
| MythBusters did an experiment concluding it was both the skin and
| hydrogen:
|
| https://go.discovery.com/tv-shows/mythbusters/videos/hindenb...
| WalterBright wrote:
| > Imagine a cigar-shaped balloon as large as a skyscraper filled
| with explosive gas. Combine that hydrogen with oxygen from the
| air, and a source of ignition, and you have "literally a bomb,"
| Giapis says.
|
| 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.
| SiVal wrote:
| I agree. Hydrogen and jet fuel are not "explosive". True
| explosives contain all the components they need for the
| reaction. Hydrogen and jet/diesel/gasoline fuel require
| injected oxygen to burn, and you can create an explosive
| mixture by mixing it with oxygen or keep it non-explosive if
| you can keep the oxygen out.
|
| 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.
| gamblor956 wrote:
| It's not the same thing. Airliners are not filled with
| explosive gas, they're filled with breathable air. They have
| these specialized things called "fuel tanks" that are purpose-
| designed to safely hold combustible fuel.
|
| 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.
| andrewla wrote:
| > zeppelins like the Hindenburg were literally just filled
| with Hydrogen
|
| 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.
| WalterBright wrote:
| Airliners carry a _lot_ of fuel. The wings are fuel tanks,
| and there are more in the belly. There 's so much fuel they
| cannot even land after takeoff without dumping it.
|
| > 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.
| mulmen wrote:
| It depends on the plane but airliners can land with full
| fuel loads. Juan Browne does a great job explaining this on
| his YouTube channel:
| https://www.youtube.com/watch?v=4D2Kj0t4t9s.
| zdragnar wrote:
| Jet fuel is flammable, but hardly explosive in the same sense
| that hydrogen is.
| WalterBright wrote:
| https://www.britannica.com/topic/Air-France-flight-4590
|
| 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.
| WalterBright wrote:
| The passengers and crew aboard TWA Flight 800 would probably
| disagree if they'd lived.
|
| https://en.wikipedia.org/wiki/TWA_Flight_800
|
| The probable cause was a spark in the fuel tank.
| snypher wrote:
| It's disingenuous to present the parent comment as saying
| "jet fuel isn't explosive". Here's some more info on a
| hydrogen accident involving a relatively small amount.
|
| https://www.powermag.com/lessons-learned-from-a-hydrogen-
| exp...
| WalterBright wrote:
| Whether its explosive or not is irrelevant when it comes
| to aircraft/Zeppelins. The problems is it _burns_ very
| hot and any airplane that catches fire has only seconds
| before it is consumed, whether or not it explodes.
| FabHK wrote:
| > If people had continued to develop Zeppelins
|
| 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.
| fastball wrote:
| Don't we have Helium anyway?
| timbit42 wrote:
| We don't have an unlimited supply.
| echelon wrote:
| Helium is extremely limited and cannot be manufactured at any
| appreciable scale (you're not dealing with typical chemistry,
| but physics. Helium is an element.)
|
| 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.
| fastball wrote:
| One more problem that will be solved by fusion energy!
| zabzonk wrote:
| > Helium is an element
|
| Nitpick: So is hydrogen.
| vitus wrote:
| Yes.
|
| 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).
| zabzonk wrote:
| > The secondary issue with helium is that it's much
| lighter than air
|
| Actually, hydrogen is lighter, and so a better lifting
| gas, than helium.
|
| https://www.wikiwand.com/en/Lifting_gas#/Hydrogen
| FabHK wrote:
| Yes, but while hydrogen (H) has half the mass of helium
| (He), H is only 8% better than He in providing lift in
| the air, if I computed correctly (as that is generated
| from displacing much heavier air), so it's not a huge
| deal:
|
| 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)
| zabzonk wrote:
| According to the wikipedia page I linked to:
|
| > 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 :)
| cbsmith wrote:
| Yeah, but only one of them is a noble gas that is rarely
| bound into molecules that would be found in solid form.
| As a consequence, it tends to just leak out of the
| atmosphere without a lot of sources for replenishment.
| fatsdomino001 wrote:
| We can theoretically do vacuum zeppelins, which is of
| course lighter than helium and unlimited tho it has its own
| problems too.
| bentcorner wrote:
| I was curious about this and it looks like it's currently
| impossible to have a material that is both strong enough
| and light enough to support a vacuum balloon:
|
| https://physics.stackexchange.com/questions/71027/is-it-
| poss...
| treeman79 wrote:
| Don't forget about "null" gas.
|
| Better the hydrogen, a few _small_ technical problems
| aside.
|
| https://en.m.wikipedia.org/wiki/Vacuum_airship
| fnord77 wrote:
| iirc, the germans wanted to use helium at the time, but the
| US more or less had a monopoly on it and would not sell to
| germany
| [deleted]
| ChuckMcM wrote:
| This is pretty good, it has a both the theory of how it started,
| an experiment to validate the theory, and math to show that the
| event timeline matches the theory. I'm generally convinced this
| is the correct answer (at last).
|
| 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)
| jonsen wrote:
| Relevant for the discussion here.
|
| "Reinforced aerostat technology for safe hydrogen use in
| airships":
|
| https://safeairship.com/
| jonny_eh wrote:
| I recall seeing a previous documentary where they found evidence
| that the paint on the exterior of the balloon was new, never
| used, and highly flammable. Perhaps that, combined with this
| latest capacitor theory, full explains what happened.
|
| Update: nvm, just found this:
| https://www.airships.net/hindenburg-paint
| emmelaich wrote:
| That article says it's not "rocket fuel", but everyone knows
| that Cellon dope is highly flammable.
|
| At least, those who used to make model aircraft with balsa wood
| and dope.
___________________________________________________________________
(page generated 2021-05-17 23:00 UTC)