Wanggongchang Explosion | Hacker News Reader

Wanggongchang Explosion

en.wikipedia.org

204 pointsbenbreen41 comments

While the Wikipedia article says "no academic consensus has been reached" it seems pretty clear from the "possible causes" section that a bolide (meteor exploding in the air above) is the only explanation listed which seems to fit the facts.

I'm curious, therefore, why the lack of consensus? Is there any evidence inconsistent with the bolide hypothesis? Or is there just no positive proof whatsoever (e.g. some type of meteor residue or other) so it can never be conclusively demonstrated?

> The ground around the immediate vicinity of Wanggongchang Armory, the epicenter of the explosion, had sunken for over 2 zhangs (about 6.5 m or 21 feet), but there was a notable lack of fire damage

it seems a bit improbable that a bolide would just so happen to hit the armory. Given that bolide events are rare to begin with, the low chance of hitting a military building is enough to make me skeptical.

I have no idea what contemporary chemical explosives were extant, but if there were any plausible agent I would favor that instead.

> I have no idea what contemporary chemical explosives were extant

Only black-powder. Nitroglycerin, the first practical explosive more powerful than black-powder, was invented two centuries later.

> it seems a bit improbable that a bolide would just so happen to hit the armory. Given that bolide events are rare to begin with, the low chance of hitting a military building is enough to make me skeptical.

Well, isn't the probability of hitting the armory identical to that of hitting anywhere else on the planet?

Yes, but the probability of hitting a place that contains many other explosive agents which could cause the same effect is far far lower than hitting anywhere else on the planet.

Yes, and there's a very big number of things in the "anything else" category, and only very few things in the "armory" category.

On the other hand explosive materials accidents happen where big amounts of explosive materials are stored, and there's few places in the "anything else than armory" category so the event is more likely.

An airborne explosion of the bolide (which is the most popular hypothesis) could easily cause a secondary explosion in armory.

If it were not for the astounding coincidence of it being a munitions factory, it looks to me like we would be assuming an impact. But, given the absence of any smoking gun (e.g. impact crater), and the abundance of gunpowder on the site, I'm not surprised that there is debate.

Except any sound before the initial explosion would be impossible. The meteor would be traveling faster than the speed of sound, the first thing felt or heard by anyone would be the light and heat of the explosion followed by the shockwave.

When anything combustible is aerosolized and mixed with oxygen, it allows it to explode. This is how thermobaric explosives work https://en.wikipedia.org/wiki/Thermobaric_weapon see also https://en.wikipedia.org/wiki/Dust_explosion

Gunpowder doesn't need oxygen, but it burns instead of exploding. If there was an initial set of fires and smaller explosions that dispersed unburned gunpowder and wood/grain dust into the sky, once it was dispersed a flash could have spread through the dust cloud and created a huge explosion as described. This theory would explain both the initial disturbances and the huge explosion at the end, but I don't see it mentioned anywhere.

If the meteor passed overhead and then exploded some distance away you'd get the sound before the shockwave.

Perhaps the passby tore the roof off the armory and sucked black powder into the air, and then the impact shockwave caused a fuel/air-like explosion?

Also note that the description is by survivors, so the sequence of sounds maybe different away from the impact.

> If there was an initial set of fires and smaller explosions that dispersed unburned gunpowder and wood/grain dust into the sky, once it was dispersed a flash could have spread through the dust cloud and created a huge explosion as described.

That was my thought too, especially with the description of the initial rumbling noises. Gunpowder burning in a small space might well provide the energy needed to disperse something flammable in a cloud above the armory which could then be ignited at some interval after it was created, providing a fuel-air explosion above ground level which would explain the over pressure damage without burning, the shape of the mushroom cloud, and the magnitude of the explosion.

The following resources provide some context about the frequency of high energy atmospheric meteorite impacts:

https://cneos.jpl.nasa.gov/fireballs/

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

Edited 14:32 MET

A combination of meteorite air burst with compounding effects from a combustion explosion due to ammunition storage seems like it could have unpredictable effects that could account for some of the strange outcomes seen here.

Indeed - a bolide crossing the city from northeast to southwest is by far the most plausible explanation, though, as the sky was clear, it would surely have been seen as a fireball, as in Chelyabinsk? Therefore, I would guess that the "bright streak" was coincident with the initial "roaring rumble", rather than following it, and the reports are conflating the passage of the fireball with its final explosion.

If it caused the detonation or deflagration of the armory's gunpowder, that might account for most of the clouds, including trails of smoke from burning fragments thrown high into the air (the "messy strands of silk"?)