[dbatten]

Noteworthy comment:

> It is unfortunate that in the public mind, hydrogen as a lifting gas is associated with the Hindenburg disaster. Actually, hydrogen filled airships were extremely difficult to set alight. Just ask the Brits in WWI.

> The RAF could easily hit the German airships with gun fire, but couldn’t get them to ignite until they developed special phosphorus filled ammunition. They used sustained machine gun fire to rip a section of the gas bags to get the hydrogen to mix with air at their surfaces. Then, the small number of phosphorus burning bullets could ignite this hydrogen air mix. Even then, the RAF brought down very few of them.

> Because of this knowledge of how difficult it is to get a hydrogen filled airship to burn, there has been much speculation that the Hindenburg was sabotaged, set to burn deliberately, in a very public act of terrorism / economic / public relations warfare against the NAZI regime (and who could blame them?).

I had no idea that there were controversies regarding the cause of the disaster, nor that hydrogen was (arguably, at least) dangerous more in the public eye than in reality. I'd be interested to hear other modern engineering perspectives on the hydrogen issue...

[dwohnitmok]

I don't know much about the Hindenburg disaster, but the fact that it is difficult to set something alight with bullets traveling through a thin fabric and then (flammable) air (as opposed to having sparks generated by bullets hitting e.g. metal and even then, there's not a lot of sparks) is not really evidence of hydrogen's safety. It's really really hard to make even normally flammable things catch fire with normal bullets or even tracer bullets. You could shoot at a gas tank all day and it won't explode. Even absolutely riddling a gas tank with tracer rounds often won't set it alight. It is far far far easy to set something alight with a single match than it is even with full magazines of bullets, all the more so if it's a patch of air that the bullet goes straight through.

Hydrogen is still widely acknowledged to be extremely flammable (see all the references here https://en.wikipedia.org/wiki/Hydrogen_safety). We have had many many disasters with hydrogen explosions pre and post-Hindenburg.

[hguant]

> to having sparks generated by bullets hitting e.g. metal and even then, there's not a lot of sparks

Just wanted to chime in on this - it's impossible for most bullets to cause a spark, unlike what TV and movies show. Most projectiles (including the .303 round the British were using back then!) are lead with a copper plating, which are both non-ferrous metals.

Some Soviet era and US military ammunition (specifically m855 rounds) have a steel core, and those can cast sparks, but almost all handguns, and most rifles, aren't using ammunition capable of doing do.

[progre]

The reason for this is that the bullet has to be made of a softer material than the barrel, or else the barrel would wear out really fast.

[sandworm101]

Sparks no, but a spall can be hot. Fabric will not spall but whether by spark or spall, bullets hitting solid objects can generate enough heat to ignite things they touch.

[dwohnitmok]

Ah yes you're totally right! I suppose the majority of fires I've seen have been caused by spalling or something similar as sandworm101 points out.

[arghwhat]

Note that regardless of what you do, a container of fuel (without its own oxidizer) would never successfully light/sustain fire without first having displaced the majority of the fuel with atmospheric air to provide the necessary oxidizer. That’s why you can’t light a full container even with tracer rounds.

Otherwise, you are only be able to light the part of the fuel that leaked into the atmosphere.

[dwohnitmok]

I think people have done experiments with gasoline exposed to open air or with a chamber of air and even then it is quite difficult to ignite, especially if the bullet has nothing to impact against, but travels through the vapor.

[nonameiguess]

This is interesting to contrast with my experience as a former tank commander doing range gunnery with wooden targets and dry brush. Range fires due to machine gun fire happened all the time. They were not remotely uncommon or difficult to cause.

I know next to nothing about chemistry or materials science, so offer no explanation of why this would be the case but a gas tank is difficult to ignite. The only layman intuitive answer I can think of is that a high speed projectile traveling through wood generates a lot more friction than one traveling through a liquid or gas, and something has to happen to that energy.

[dwohnitmok]

Yeah as soon as you have a solid chunk of something to hit it's a lot easier to start a fire. E.g. it's actually quite easy to start a fire by shooting a lot of bullets into a gas station pump rather than a thin barrel.

[GeorgeKangas]

I read (I forget where) that the Hindenburg's skin is where it started burning. The skin was fabric, painted with flammable shellac, and the shellac contained a lot of aluminum powder.

[mental1896]

steel beams 1.0 lol

[calvinmorrison]

This is a major plot line in the kids series "Pendragon". One of the books centers around the blowing up of the hindenburg. I guess the author was onto this as a conspiracy and decided their own explanation! (If your child liked Artemis Fowl, they might like this series)

[nradov]

Perhaps airships need a different lifting gas, one with "almost indefinite powers of expansion".

http://www.forgottenfutures.com/game/ff1/night.htm

[jamiek88]

Wow that was such a trip.

I love the old sci fi where they extrapolate (incorrectly) new inventions such as the dirigible to the future.

This was well worth the read! Thanks!

[notatoad]

if you go down this rabbit hole on google, just be wary that while the hindenburg sabotoge conspiracy theory actually seems fairly plausible, most of the people you'll find talking about it are right at the top of this chart:

https://www.irishtimes.com/polopoly_fs/1.4532919!/image/imag...

[loufe]

A bit off topic but I'm a little sad to see "Covid-19 made in lab" in the "dangerous to yourself and others" tier, especially with how much public view has evolved. Very few people will ever know for certain, it seems, but it could very well have naturally mutated from an existing virus in captivity and then escaped accidently. We have to be careful how we approach framing conspiracies because you risk to alienate and smother valid discussion.

[laserphysicist_]

(Scientist chiming in, albeit not working in a relevant field for this discussion) In fact, several well-respected scientists are calling for a scientific and unbiased debate on the origin of covid, as it is now almost impossible for scientists to simply mention lab origin as a possible origin to study. Here is one of the last papers I've seen on this subject:

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

[missedthecue]

I wonder where "Stevie Wonder Can Actually See" lies on that chart.

[Igelau]

I'd say right on the speculation line. It's far-fetched to say he can totally see, but he may very well experience some limited optical sensation, albeit one of such limited utility that we can't really call it sight.

The story about him seeing Shaq is an interesting example. If you already know that Shaq lives in your apartment building, how much visual acuity do you need to make an educated guess that the large form waiting for the elevator is probably Shaq? There's also no one to tell us if he ever stood there talking to thin air thinking it might be Shaq ;)

It also seems like the kind of thing that would be difficult to give a satisfactory description of, so being coy about it is probably for the best.

[shiftpgdn]

I thought Stevie Wonder could see? He's just blind by the legal definition (shapes only, etc)

[xwdv]

He can not see.

[WalterBright]

NOVA did an episode recently that demonstrated how the Hindenberg could have burned based on a confluence of the weather and coincidences. No sabotage or conspiracy is necessary.

https://www.pbs.org/video/hindenburg-the-new-evidence-3hjhu3...

[dredmorbius]

If your hydrogen-filled airship is flying through heavy anti-aircraft fire, you likely have bigger problems.

This scenario also fails to address the numerous failure modes of airships, including but not limited to the extraordinarily wide range of explosive mixes of hydrogen and air, as well as the rapidity and violence of hydrogen combustion and explosions.