1. Catrin Lewis
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    Catrin Lewis Contributing Member Contributor

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    Explosions and Other Fun Stuff

    Discussion in 'Research' started by Catrin Lewis, Feb 7, 2015.

    I need an explosion for my thriller. Not atomic, just a good-sized high-explosives explosion. I've been wasting my time searching Google the past four hours, but haven't come up with what I require.

    Specifically, how would a honking big blow-up would feel and look and sound to my protagonists under the following circumstances?
    • The explosion is about two miles from them as the crow flies
    • It's on the other side and towards the top of an Appalachian-sized mountain, maybe 2,000 feet up from where they are
    • The top of this mountain is riddled with limestone caves
    • One of which holds my domestic terrorist villain's stockpile of high explosives, etc., that he has saved up for his upcoming race war.
    • The cops are closing in and the stockpile gets touched off
    • The blast is big enough to blow off the other side of the mountain
    • When the blast goes, my female protag is climbing into the backseat of a police cruiser and the male protag is about to get in, but his legs are still on the pavement
    • Both their heads are under the cover of the roof
    • They both have their backs to the explosion
    Given all that, would they feel a significant shockwave? Would it be enough to push him in on top of her? Would the pavement ripple or the car jump? Or would the lower part of the mountain absorb the shock?

    For them, the sound would come next. Would having the bulk of the mountain between them and the blast muffle it significantly?

    What about debris? Would a good-sized explosion throw stuff up and over and down on them?

    When the debris, if any, stops falling I want them both to get out, turn around, and see the dust cloud from the explosion and the fire and smoke from the trees it's caught on fire. Its appearance drives the next part of the action. That should ascend high enough for them to see, wouldn't it?

    If I have to, I'll do the math of this, though it means assigning specific values to my variables. But can anyone help me find a source for the formulas I need?

    Thanks
     
  2. Chinspinner
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    Chinspinner Contributing Member Contributor

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    I remember hearing this one in London: -

    http://en.wikipedia.org/wiki/Buncefield_fire

    As for all the variables in yours, I have no idea.
     
  3. Bryan Romer
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    Bryan Romer Contributing Member Contributor

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    At two miles distance, conventional explosives are not likely to produce more than a heavy rumble and possibly some vibration in the ground. It is possible that some debris might reach that far, but nothing huge, more like individual pieces of gravel. Fireball and smoke would depend upon the surroundings and the nature of the explosives.

    C4 (US military grade plastic explosive) would produce a cloud of dust and debris, not much smoke or flame (at 2 miles).

    Other explosives e. g. ANFO (ammonium nitrate and diesel fuel)

    C4 vid:


    ANFO vid:
     
  4. Catrin Lewis
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    Catrin Lewis Contributing Member Contributor

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    Thanks. It wouldn't be C4, more like TNT, nitroglycerin, that kind of thing. I wonder if you'd get more of a shockwave if there's a lot more of it.

    I'm thinking any flame would be from surrounding flammables (i.e., trees) catching fire.
     
  5. Bryan Romer
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    Bryan Romer Contributing Member Contributor

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    Explosions are funny things. It depends a lot on the placement of the explosives, whether they are in any way in a contained space (which will make the explosion more intense), the shape of the surroundings, and the nature of the surroundings - rock vs soft earth vs sand vs swamp or water.
     
  6. Sam Mills
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    Sam Mills New Member

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    For a domestic terrorist hold up inside a cave I would imagine his primary explosive is going to be something along the lines of ANAL (Ammonium Nitrate Aluminum Power) (and yes, that is really the abbreviation for it, I'm not kidding). The ingredients to produce ANAL are easy to acquire and it is easy to make. With an average RE factor of about 0.6 - 0.8 it isn't as powerful as TNT but would be much easier for a domestic terrorist to acquire.

    RE factor is the measure of an explosive's blast yield when compared to the blast yield of TNT of the same weight. e.g. 1lbs of ANAL with an RE factor of 0.8 will will have 80% of the power of 1lbs of TNT. This system, however, is more a measure of the explosives output efficiency and not really an exclusive assessment for how well an explosive will accomplish a certain job. TNT (RE factor of 1) is classified as a pushing explosive as it explodes slowly in relation to other explosives (19,000 fps). Therefore it works better for demolitions than C4 does. C4 has an RE factor of 1.34 and explodes at about 24,000 fps, and is a cutting explosive and is better applied when used to make small, precise explosions. I don't know exactly what the explosive velocity of ANAL is, but it is a slower, pushing explosive like TNT. (also, in case you didn't know, TNT and dynamite are not the same thing. Dynamite has an RE factor of about 0.9 and it is less stable and less reliable than TNT. As such, it isn't really used anymore.)

    I feel nitroglycerin is a poor choice for a terrorist in a cave up in the mountains. Nitroglycerin is extremely volatile, and it would be very foolish to be transporting it up and down a mountain. I'm not saying that a terrorist will not use nitroglycerin, but a smart one who knows what he is doing will probably not take the risk, especially when there are better alternatives that are easier to acquire.

    As for what you actually want to accomplish with your explosion, two miles is a long distance to feel the effects of an explosion, especially with a mountain in the way. Someone with more knowledge than me may be able to estimate how large an explosion you would need in order to feel the ground shake, but I would guess at least a few thousand pounds if the explosion were sitting on the side of the mountain and facing them. I'll give an example from my personal experience to try to give some context. I've had about 1000lbs of tritonal (an explosive compound made of a mixture of TNT and Aluminum Power with an RE factor of 1.18) go off about 300m away and the ground shook and i felt a mild shock wave. The force was not nearly enough to knock someone down or even make them almost lose their balance. I've also been up to 1000m away from similar explosions, and could barely feel the ground vibrate.

    Blowing the back out of a mountain would be quite a tricky endeavor. I cant give you a super accurate estimate on the amount of explosives you will need as I do know the exact circumstances, but to blow out the backside of a mountain, I imagine you will need at least several tons of TNT. Obviously the thickness of the mountain wall and the placement of the explosives in relation to the wall will have a huge impact on the amount needed. Being inside the confines of a cave could, however, make it easier, as the pressure will be confined thus allowing the potential for greater results from a smaller blast. The fewer chambers the cave has, and the smaller the entrance is will likely increase the efficiency of the blast

    I can tell you with about 99% certainty that an explosion such as the one you want will not create a fire, even if there is an ample supply of flammable material around. Maybe if it was all soaked in gasoline--maybe. Contrary to what Hollywood would have you believe, most explosions (unless they are specially designed thermobaric explosions) will not produce fire. For explosions produced by chemicals such as C4 and TNT, the flash that you may or may not be able to see is produced by friction and only lasts a millisecond and is not enough to set things on fire. It could be compared to heat lightning that you seen in the clouds. Now I say 99% because sure, I guess it is possible, but it is not probable. There will be a ton of dust, although probably not anywhere near them.

    As for debris, even with a small explosion it is very possible for them to get hit with debris, and even with a large explosion it is possible that they wouldn't get hit with any. It is almost impossible to predict what debris is going to do. For an explosion large enough to blow the back of a mountain out and large enough for them to feel the shock wave, it would be very believable for debris to be falling around them.

    So this may be more information than you wanted, but I hope some of it is helpful. I'm really bored right now and I've blown a lot of shit up so I figured I'd just share some knowledge.
     
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  7. Catrin Lewis
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    Catrin Lewis Contributing Member Contributor

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    Thanks, this is actually useful. What I want out of the explosion primarily is a dust cloud of a particular description. Everything else is just color and drama.

    Because . . . My villain, in addition to his cache of TNT, ANAL, etc. (no nitro. OK. :agreed: ), has got himself a pet nuclear physicist who has built him a working suitcase nuke. My protags have seen the device in person and when they see the dust cloud from the explosion, they're looking to make sure it didn't go up with the rest of the stuff. In other words, the blast cloud can't be big enough to mushroom.

    Having done some research, I'm aware that a big enough conventional explosion can produce a mushroom cloud. But my protags don't know that, there's no reason why they should know it. And I doubt my potential readers would know it, either.

    Why do I want the explosion to be on the other side of the mountain? So they can be afraid-- for a few seconds at least, that it's the A-bomb that went off. They're not scientists, they're in a stressful situation-- it'd be quite normal for them to think, "Oh God, the A-bomb went off, and the only reason the shockwave hasn't killed us is because the mountain's in the way."

    And then they turn around and go, "Whew!"

    I want them to be relieved that they're in no danger of radioactive fallout-- then get scared wondering where the heck the A-bomb is that it didn't go off with everything else.

    The villain's made off with it before the cache went up.

    As for fire . . . You're saying it wouldn't set the surrounding trees, structures, and vehicles ablaze? OK. Don't need that, really. My only personal experience with large explosions has been with underground gas pipes blowing. And that set a lot of things on fire.
     
    Last edited: Feb 15, 2015
  8. Sam Mills
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    Sam Mills New Member

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    I can definitely see that being a realistic fear.

    I find it unlikely, although not impossible, that standard chemical explosives (TNT, ANAL, etc.) even of that magnitude would start a fire on buildings and trees. Vehicles would be more likely because of the fuel. However, with a terrorist who has a tactical nuke, it is reasonable to believe that he also has something like white phosphorus or a benzene based fuel explosive within his stockpile. That will set water on fire.

    Glad I could help
     

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