Analysis of the Beirut explosion?!

[Guest]

3 hours ago, kerbiloid said:

It doesn't matter how.

Of course it does. This is a fundamental difference between explosives. Material can only be scattered by the shockwave if it's not shock-sensitive. AN is shock sensitive, therefore it will be detonated, not scattered. You're confusing it with heat-sensitive materials. AN doesn't burn, it decomposes explosively through a completely different mechanism than something like gunpowder.

If not, tell me how exactly does the explosion throw around a shock-sensitive material without making it explode?

[kerbiloid]

4 minutes ago, Dragon01 said:

Of course it does. This is a fundamental difference between explosives.

It just initiates the process, but doesn't provide conditions of its progress. So, it doesn't.

[Guest]

8 minutes ago, kerbiloid said:

It just initiates the process, but doesn't provide conditions of its progress.

That's nonsense. It doesn't need to provide "conditions of its progress". It's an exothermic decomposition, which means it will happen all by itself. Once initiated, it will happen, no matter the external conditions. Unlike a fire, AN decomposition can run without an external substrate, and you cannot take heat away fast enough to stop it that way. Again, this is different from many other explosives, especially ones that you could have encountered and handled.

BTW, it's the same reason your assertions about containment are bunk. With a shock-sensitive explosive, no containment is needed for the explosion to occur. AN is not gunpowder. 

Edited August 9, 2020 by Guest

[kerbiloid]

It just means that most part of reaction mass will fly away before it can react, so no wave of pressure can happen.

Again, I won't keep repeating all said endlessly.

Edited August 9, 2020 by kerbiloid

[Guest]

30 minutes ago, kerbiloid said:

It just means that most part of reaction mass will fly away before it can react, so no wave of pressure can happen.

I know what it means. I'm asking, what pushes it away, before the shockwave can hit it, so gently that it does not explode?

FYI: "Shock sensitive" means "explodes when hit really, really hard". A shockwave from explosion is not fire, it's a wave of pressure that hits things really, really hard. 

Edited August 9, 2020 by Guest

[RCgothic]

1 hour ago, kerbiloid said:

It just means that most part of reaction mass will fly away before it can react, so no wave of pressure can happen.

Not with a supersonic shockwave it won't. The triggering shockwave arrives before any mass can be scattered.

[kerbiloid]

2 hours ago, Dragon01 said:

I know what it means. I'm asking, what pushes it away, before the shockwave can hit it, so gently that it does not explode?

FYI: "Shock sensitive" means "explodes when hit really, really hard". A shockwave from explosion is not fire, it's a wave of pressure that hits things really, really hard. 

 

1 hour ago, RCgothic said:

Not with a supersonic shockwave it won't. The triggering shockwave arrives before any mass can be scattered.

Once again. If somebody doesn't read, it doesn't mean I must rewrite.

[mikegarrison]

On 8/7/2020 at 10:59 PM, kerbiloid said:

 

Clarification is required. What exactly do they call "dimensional analysis" and its algorithm.

Dimensional analysis is a common engineering technique for determining relationships between various things.

For instance. Lift is a force. It has dimensions of mass * distance * (1/time)^2. That means if you know that Lift is proportional to velocity^2 and surface area and something else, that something else must have dimensions of mass/volume. In other words, you can figure out you are missing a density somewhere. And sure enough, the actual calculation for lift includes the fluid density.

Edited August 9, 2020 by mikegarrison

[Guest]

57 minutes ago, kerbiloid said:

Once again. If somebody doesn't read, it doesn't mean I must rewrite.

Quote it, then. There are no rules about quoting yourself, if you think we have missed the part in which you answered that question. 

Of course, you never did, because the real answer is "nothing, and the shockwave causes it to explode". There is no other non-absurd answer. You are demonstrably wrong on a fairly straightforward matter and just refuse to admit it.

[kerbiloid]

38 minutes ago, mikegarrison said:

Dimensional analysis is a common engineering technique for determining relationships between various things.

For instance. Lift is a force. It has dimensions of mass * distance * (1/time)^2. That means if you know that Lift is proportional to velocity^2 and surface area and something else, that something else must have dimensions of mass/volume. In other words, you can figure out you are missing a density somewhere. And sure enough, the actual calculation for lift includes the fluid density.

Thank you.
Then I was using the dimensional analysis from the first post in another thread.

[mikegarrison]

16 minutes ago, kerbiloid said:

Thank you.
Then I was using the dimensional analysis from the first post in another thread.

Strictly speaking, dimensional analysis and ROM (rough order of magnitude) analysis are different things, but they are often combined together, so I'm not sure if the reference to dimensional analysis included a ROM component or not.

[kerbiloid]

5 minutes ago, mikegarrison said:

Strictly speaking, dimensional analysis and ROM (rough order of magnitude) analysis are different things, but they are often combined together, so I'm not sure if the reference to dimensional analysis included a ROM component or not.

No, I mean the very first posts in another thread, where I was estimating the overpressure value.

[magnemoe]

10 hours ago, Dragon01 said:

Of course it does. This is a fundamental difference between explosives. Material can only be scattered by the shockwave if it's not shock-sensitive. AN is shock sensitive, therefore it will be detonated, not scattered. You're confusing it with heat-sensitive materials. AN doesn't burn, it decomposes explosively through a completely different mechanism than something like gunpowder.

If not, tell me how exactly does the explosion throw around a shock-sensitive material without making it explode?

Now, with an fairly low power blast like demolition you can easy get settings where gaps between TNT blocks shatter the blocks after the blocks rather than detonating them. 
With an kiloton blast the shock will set off pretty much everything. 

[Guest]

That's because shattering a TNT block is not very difficult. I've never handled it myself, but from what I've read it's got basically no structural strength. Judging from the numbers, you can easily break up a TNT block with your hands. If the actual shockwave is almost completely absorbed between one block and the next, it could easily crack another block without it blowing up. It wouldn't really throw the pieces around by that point, though.

[kerbiloid]

Not the "shockwave is almost completely absotbed" but "the explosive gets too porous to support reproducing the wave of pressure".
Why, do you think, they always stick multiple detonators into a large pack explosives, and cover it with ground.

[Silavite]

This is just my opinion, but it seems to me that all the discussion about the AN being wet, decayed, partially stolen, or not detonated seems to be rather beside the point right now. There is some circumstantial evidence for these, but trying to pin down the energy released in the blast by these (circumstantial) factors seems to be of questionable utility. The only piece of direct prior evidence is that the freighter offloaded 2,750 metric tons of AN. On the other hand, we have sundry imagery of the blast itself, the crater, and damage the blast caused. We have seismic data which may be compared to other explosions.

Rather than trying to estimate the energy by factors from prior to the blast, it seems better to look at factors which came about during/after the blast.

[sevenperforce]

Explosives experts agree that visual analysis of the shockwave and fireball suggest complete or near-complete detonation of the AN in a 1-1.5 kt range:

https://indaily.com.au/news/2020/08/06/beirut-blast-one-of-biggest-ever-non-nuclear-explosions/

On 8/8/2020 at 1:59 AM, kerbiloid said:

It could not detonate completely even if staying completely intact, because it was neither encased, nor properly initiated in many places.
Only a small part of it could detonate, and the question is just how much small.

That is how black powder works, but that is not how AN works. AN is a high explosive. Lower-energy than many other high explosives like Semtex or NG, but a high explosive regardless.

Have you ever seen someone put plastic explosive on a door in a movie? Well, movie physics is typically not accurate, but that part is. You don't need a bomb casing for C4. High explosives do not need to be encased because the hypersonic shockwave does all the work.

On 8/8/2020 at 1:59 AM, kerbiloid said:

ignition is not enough. The AN should be encased and ignited in many points, otherwise most part of it would be just spread around and burn without detonation, and what we can see looks exactly like this.

Again, high explosive does not need containment or encasing. Once detonation initiates, the shockwave does the rest.

On 8/8/2020 at 1:59 AM, kerbiloid said:

AN consists of 2 N, 3 O, 4 H.
N is nearly inert ballast, it's mostly exhausted as N.
4 H get bound with 2 O.
1 O gets released.

So, AN doesn't depend on the air at all, it can't be a fuel-air explosive. In air it just has greater surface area, that's all.

You miss the point.

Both the decomposition and the detonation of AN are oxygen-rich. A high-temperature indoor fire is fuel-rich. What happens when you mix a fuel-rich gas with an oxygen-rich gas?

Spoiler

 

That's right, a fuel-air explosive. 

On 8/8/2020 at 1:59 AM, kerbiloid said:

In this case the impurities are an excessive entity. Nothing makes to think they were there even if they were, as the total yield of the explosion looks much less than kilotons.

You keep insisting the total yield looks too small, despite every single demonstrated metric showing it is kiloton-level.

What makes you think that the impurities were inert rather than reductants?

On 8/8/2020 at 1:59 AM, kerbiloid said:

And even if it actually was that strong, don't compare the strong metal hull of the ship (i.e. the casing, keeping both pressure and reaction mass inside) and lightweight storage construction with windows and doors.
Of course, the storehouse walls became a cloud of flying rubbish before the AN could react completely.

Doesn't matter. High explosive.

On 8/8/2020 at 1:59 AM, kerbiloid said:

On 8/7/2020 at 1:27 PM, sevenperforce said:

We also can see from visual inspection of footage that the instantaneous fireball was between 60 and 110 meters, comparable to a one-kiloton nuclear blast.

While 1 kt nuke blast would have at least 120 m in diameter.

60-110 meters is the observable radius. Thanks for pointing out that I didn't specify.

On 8/8/2020 at 1:59 AM, kerbiloid said:

We can see the progress of the fireball expansion, and it unlikely can be defined so precisely, so the 7 Mach is just the upper (and emotional) value.

Emotional?

Mach 7 is not an upper limit. It is a lower limit. If you want to insist otherwise you will need to show maths.

[sevenperforce]

12 hours ago, kerbiloid said:

Not the "shockwave is almost completely absotbed" but "the explosive gets too porous to support reproducing the wave of pressure".

Please explain the physics of that particular idea.

A tertiary explosive becomes "too porous" to "support reproducing" a hypersonic detonation wave?

12 hours ago, kerbiloid said:

Why, do you think, they always stick multiple detonators into a large pack explosives, and cover it with ground.

I don't think you know anything about planned detonation of high explosive. Might I suggest reading?

[mikegarrison]

12 hours ago, kerbiloid said:

Why, do you think, they always stick multiple detonators into a large pack explosives, and cover it with ground.

My assumption is that the timing of which explosive packages fire first is important.

[sevenperforce]

19 minutes ago, mikegarrison said:

My assumption is that the timing of which explosive packages fire first is important.

I'm not entirely sure that they DO stick multiple dets into explosives, typically. At least, not more than two. I don't think that snippets inside films are a good guide on this point.

Having two detonators per explosive pack is important in case one fails, but beyond that it's not necessary unless you specifically need to do a shaped charge. For example if you need to cut a linear slice through a barrier, you can throw on C4 or Semtex in a long, narrow column and then place pairs of detonators on either side of it so that the hypersonic shockwave meets in the center and causes a constructive interference wave...knife through butter.

Of course "cover it with ground" is just nonsense. Covering high explosives with dirt does nothing whatsoever. 

[mikegarrison]

8 minutes ago, sevenperforce said:

Of course "cover it with ground" is just nonsense. Covering high explosives with dirt does nothing whatsoever. 

This is not true.

I mentioned that time when I was a kid and was blowing stumps with dynamite and ANFO. One time we put a rock on the top of it. That rock went sailing into the air very spectacularly. (This was, of course, a profoundly stupid thing to do.)

[magnemoe]

13 hours ago, kerbiloid said:

Not the "shockwave is almost completely absotbed" but "the explosive gets too porous to support reproducing the wave of pressure".
Why, do you think, they always stick multiple detonators into a large pack explosives, and cover it with ground.

its not common to use multiple detonators if you have one pile of explosives as they are very reliable. If you do rock blasting you drill many holes and each hole get one detonator. 
Now then doing demolition and put out an line of linear shaped charges you might use multiple detonator or something like detonating cord as air gaps between TNT blocks can get the explosion to shatter the blocks behind the gap rater than detonating them. 

Now aircraft bombs and artillery shells often has multiple detonation systems in case the primary failed or got destroyed on impact. Say you fire an shell set to explode 50 meter above ground but the radar fails or is jammed, it will then explode then hitting ground. 
 

[sevenperforce]

5 minutes ago, mikegarrison said:

This is not true.

I mentioned that time when I was a kid and was blowing stumps with dynamite and ANFO. One time we put a rock on the top of it. That rock went sailing into the air very spectacularly. (This was, of course, a profoundly stupid thing to do.)

Well yes obviously it does that.

I meant it does nothing to help contain the explosion, which was presumably @kerbiloid's contention.

[kerbiloid]

I have nothing to add to the said earlier, and definitely I don't think that this is a proper forum for moar info on this topic.

[mikegarrison]

14 minutes ago, sevenperforce said:

I'm not entirely sure that they DO stick multiple dets into explosives, typically. At least, not more than two. I don't think that snippets inside films are a good guide on this point.

Having two detonators per explosive pack is important in case one fails, but beyond that it's not necessary unless you specifically need to do a shaped charge. For example if you need to cut a linear slice through a barrier, you can throw on C4 or Semtex in a long, narrow column and then place pairs of detonators on either side of it so that the hypersonic shockwave meets in the center and causes a constructive interference wave...knife through butter.

We are miscommunicating. I did not mean multiple dets into one explosive charge. (Although, the idea of a backup does seem like a good idea.) I meant when there are multiple charges. They typically don't just hope for sympathetic detonation, but rather arrange so that each charge happens in sequence or simultaneously (as needed). Like when imploding buildings or blowing rock apart.