A blast in Tianjin sets off an explosion online | Hacker News Reader

A blast in Tianjin sets off an explosion online

economist.com

34 pointsjeo123416 comments

by the way, have you seen a "21 ton TNT" crater :

http://www.wsj.com/articles/tianjin-blast-destruction-from-a...

Looking at it i'm pretty sure there should be at least 1 more trailing zero in the TNT equivalent number, and the 21 ton is just a small portion of the explosion energy, ie. it is the portion which went into the ground and formed the seismic wave.

Also: Explosive energy rises much, much faster than crater diameter. http://palaeo.gly.bris.ac.uk/communication/brana/equation.ht... says energy goes up roughly with the 3.4th power of crater diameter, in impact craters.

To those who wonder, Little Boy and Fat Man, the atomic bombs, exploded each at about 18 to 21 kton TNT, which is a thousand times more. Interestingly enough, they both could have tripled their power depending on how much fissile material would react.

Apparently the blast was so powerful it was picked up by US Geological Survey equipment which is built to detect earthquakes. http://www.theguardian.com/world/2015/aug/12/china-explosion...

Those systems (or ones like them) are also meant to detect weapons tests, so it appears they are doing their job.

The explosion and smoke plume was picked up by Japan's new weather satellite too. http://www.citylab.com/weather/2015/08/satellites-spot-the-t...

The make and model of my car in my driveway was picked up by the satellite Google was buying from in 1997.

I don't understand why "It was seen from space!" is at all a part of the story today.

> I don't understand why "It was seen from space!" is at all a part of the story today.

Becuase most people still do not realize that the space is closer to their home, than holidays resort they have visited this summer.

Thunderfoot did a video about this where, like you, he estimated the order of magnitude to be 1-2x greater than the most likely fake number reported by the Chinese government: https://www.youtube.com/watch?v=_hcwMwFbJKc.

interesting, he puts it between 3kt and 300 tons based on the fireball size from the video where is my first immediate estimate just based on the same video - only i used distance and blast sound wave - was 2kt. I adjusted it down (mainly by adjusting down the most speculative element - estimate of the sound wave from the video) to 500-200 tons once i saw the next day photos with the apartment buildings still standing at 300m distance. Once i saw the crater - i became pretty sure that it is more close to 500 than 200.

James Kennedy has this analysis of the explosion [ https://jameskennedymonash.wordpress.com/2015/08/17/the-chem... ], including the possible chemical reactions and the amount of energy released.

Curious that he couldn't "find" the enthalpy of reaction for the ammonium nitrate. Surely he could calculate it from the sum of the products minus the sum of the reactants.

Sum of products is surprisingly hard to do for something like ammonium nitrate.

Among other things, there are actually multiple distinct breakdowns:

      NH4NO3 ---->   HNO3 +   NH3 
    5 NH4NO3 ----> 2 HNO3 + 9 H2O + 4 N2
    2 NH4NO3 ---->     O2 + 4 H2O + 2 N2
      NH4O3  ---->    N2O + 2 H2O

I suspect you could do fairly well by assuming that it follows reaction 3, though. Like with assuming complete combustion.

The article make it sound like the incompetence of the Chinese officials is something particularly bad or remarkable.

For my experience those level of incompetence is just what you should expect.

Western world have no idea what China really means...

Nice try by the author to convince people to believe whatever the social media threw at them.

Funny how a "we are dying" note reads like.

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