2700 tons of Ammonium Nitrate went bang to put it mildly. I understand clearly that there needs to be a ‘spark’ to set it off, but how does it all go at the same some, rather than for example 2700 smaller bangs?
In: Chemistry
Basically an explosion sets off the other material which itself explodes and sets off more, so though it looks like a single explosion it is really a series of microexplosions spreading rapidly outwards at the rate of the explosion so it all looks like one big explosion.
The simple answer is that it’s a chain reaction. When one molecule explodes (chemical bonds are broken) those atoms crash into the next molecule, which explodes and crashes into the next molecule, etc, etc. This is all happening at near the speed of light at a molecular level.
The technical name for it is “detonation”. This refers to a process where a supersonic shockwave travels through the material in a self-sustaining way.
Think about setting one corner of a piece of paper on fire. The fire will slowly but steadily spread as the heat from the flame gets the paper next to it hot enough to start to burn. But, this is limited by how fast the paper can be heated up by the flame.
In a detonation, the energy released by a small section of the material exploding, in the form of heat and pressure, is enough to set off the neighboring material almost instantly, which in turn sets of the next little bit and so on. This results in a fiery pressure wave traveling though material at extreme speed, and wherever the wave crosses it causes the chemical reactions that release the energy to happen.
Explosives are explosive because there is a lot of energy holding the molecules together, but the molecules aren’t very stable. They fall apart pretty easily when certain forces such as heat or impact cause the weak bonds to break.
When those bonds break, the energy holding it together releases all at once.
That force is an explosion and it can travel very fast, the speed/force of which varies depending on the substance.
But a weak explosion will travel at least 1600 meters per second. Solid explosives have more force, so in this case it’d be closer to 4000+ m/s.
So you have a big room full of explosive substance. The explosion triggers when some of the substance is triggered by heat or a spark of what have you.
That explosion travels 4000m/s and triggers whatevers around it much faster than neurons in your brain can even process whats going on (neurons fire at about 70 to 120 meters/second).
So it triggers all the other explosives faster than your brain even realised.
A lot like a nuclear reactor honestly.
Once it reaches the critical stage, the combination of oxygen with decomposing NaNO2 creates a perfect situation for combustion.
The decomposition can create heat inside the pile, ask a farmer about manure fires, if not turned during decomp, they literally spontaneously catch fire.
In an explosion, the pressure at the heart of the fire is too high, and the atmospheric pressure outside it can’t contain it anymore, and it erupts, releasing energy its stored as it burned
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