Making Explosions

OK. So let's say your characters were trapped in something similar to a convenience store, and it was under siege. And you needed, for story purposes, to absolutely explode the thing. Just blow the hell out of it. As big an explosion as possible. Assume that the survival of whoever sets the explosion off isn't particularly necessary.

How would you do it? Is it possible? (What if you had, say, an oven with a gas line you could get to. Does that help?)

Step 1: Get gasoline.

Step 2: Get an electric mains.

Step 3: Put (1) around (2).

Step 4: ???

Step 5: KA-BOOM!

Step 6: Profit!

That's my way, though. There can be other more interesting solutions.

Liquid gasoline burns, it does not explode unless under pressure in a situation we call a BLEVE.

Now pour it all about and let it sit for about 10 minutes and it'll explode. Gasoline vapors are inherently explosive and liquid gasoline loves to evaporate at room temperature.

edited 24th Jan '11 8:13:24 AM by MajorTom

Major Tom is right. You want vapor, and you want it as strong and as widely spread throughout the store as possible. Gasoline may be hard to come by inside a convenience store, but there's probably several bottles each of cigarette lighter fluid and charcoal lighter fluid. Pour them all out on the floor. Dozens (if not hundreds) of butane lighters you can smash open; do so— the butane will vaporize. There may be a natural gas line to either the water heater or the furnace: you can disconnect it from the appliance and leave it open — or just cut the line. Do everything you can to fill the building with flammable vapor.

Light a match just before you pass out from asphyxiation. Building go boom.

edited 24th Jan '11 9:48:26 AM by Madrugada

BOOM.

Oh, one other possibility, if the people in the store can go outside for a very short time and get back in safely — around here,a lot of convenience stores have locked racks of LP (liquid propane) tanks outside for sale/rent. The tanks are usually the twenty-pounders. If some one in the store can get outside and back in with even one or two of those and open the valve to let the LP out, you'd get an even bigger BOOM.

^ Better yet. Pour gasoline over them and set those tanks on fire without opening them.

Remember that wiki link a couple posts ago? That's what will happen.

Well, yes, if you've got enough time to get the gasoline and spread it, and let it vaporize a while,as opposed to unlocking the door of the cage, grabbing a tank and bolting back inside the building. If there's a cage of them outside, you'll get the BLEVE anyway, when the building goes.

edited 24th Jan '11 7:05:28 PM by Madrugada

The Bleve won't happen because of an explosion, it will happen because fire around it is making the gas inside boil under pressure until the container cannot stay together.

The Mythbusters tried exploding propane tanks with outside fires to shoot off like a rocket (And ultimately succeeded somewhat. The rest of the tests before largely ended in Bleves.)

Meaning, a sudden blast is just likely to rupture the tanks and send them flying in random directions without exploding or knock them over. Not make them explode into giant fireballs. Now the whole station engulfed in flames and the tanks right next to it? Bleve waiting to happen depending on distance from the flames.

edited 24th Jan '11 7:25:06 PM by MajorTom

Hmm. There was a recent explosion in San Bruno due to a faulty gas pipeline. I think electricity made it explode, but I'm not sure.

edited 24th Jan '11 7:54:27 PM by JackMackerel

Gas pipelines (natural gas like in San Bruno) are prone to explosion if ruptured and set to a spark like a frayed electrical wire or whatnot.

If it only has to be similar to a convenience store they could make a fertilizer bomb. They'd need Ammonium nitrate (fertilizer) and some kid of fuel oil (diesel should do). I don't know the exact mixture, but I’m sure a short search would give you that info (and put you on the FBI watch list).

^ FBI doesn't have that power. They couldn't know if you were a farmer looking for a new fertilizer supplier and diesel supplier or a guy looking to make a bomb, at least not without some seriously illegal search actions going on.

And the FBI has been slapped down by the courts and Congress before for those kinds of actions. They are neither immune to or above the law and Constitution.

Besides ammonium nitrate explosives are seriously overrated. There's better stuff that's less likely to provoke suspicion.

A gas line would be more common in a restaurant rather than a convenience store. Other possible improvised explosives would include hair spray or spray paint which could go boom if you put them in a microwave.

Another possibility is to induce a dust explosion, but you would probably need a small amount of standard explosives to a) act as a bursting charge for flour, icing sugar, cake mix or whatever and b) an initiation charge to ignite the dust cloud. If it worked at all you would only need a few blasting caps, but the timing one after the other would be important.

edited 25th Jan '11 11:27:30 AM by 66Scorpio

You don't need blasting caps for a dust explosion, you just need a spark like from a lighter provided you have the sufficient dust/air ratio.

Why do you think old grain silos in farmlands keep blowing up?

The FBI part was a joke. Should've added Sarcasm Mode.

Natural gas in a very common fuel for both water heaters and furnaces. Either one means that you have both a decent sized gas line and probably at least one pilot light.

Agreed with whoever mentioned dust, and here's a particularly spectacular variant on that one...sawdust.

Fine sawdust is murderously explosive if distributed in air. Mills invest hundreds of thousands of dollars on spark detection and fire suppression, and with good reason. Dust collection systems are basically fast-moving air full of flammable powder; one spark makes a hell of an explosion.

Example: I watched a table-saw blow up because the operator fed a board with a nail into the blade. The blade sparked when it hit the nail, the hot metal was sucked into the dust collector, and WHAMMO! Suddenly the table-saw could breathe fire.

A fireball shot twenty feet out of the blade slot, and the dust collection bag was literally vaporized. Only the fact that we had just cleaned up the shop of scrap wood and sawdust prevented a more lasting fire. As it was the operator had to be treated for second-degree burns and have several saw-blade fragments pulled out of his arm.

Another example: My father watched a millyard get flattened by an even more serious explosion. He was on his way to work when a freaking mushroom cloud appeared behind the hill, and a shockwave rocked his car. Given that this was 1965, visions of ICB Ms were dancing in his head. But as he crested the hill, he saw that the mill's dust silo was, well...gone.

Cause? Someone had flicked a cigarette butt in the wrong place. Guess who is to this day a fanatic about no smoking on jobsites.

edited 25th Jan '11 2:42:13 PM by drunkscriblerian

I'd give suggestions, but I'm pretty sure your characters cannot harness sheer awesomeness, so it probably wouldn't work.

You'd need a blasting cap as a bursting charge to fill the store with dust. If you got tge air/dust mixture right then yes, damn near anything would set it off. But I was thinking if you want to remotely command detonate the whole store then a proper electrical initiation set would work and maybe a blasting cap would be enough to kick it off if the air/dust mix wasn't perfect.

I don't know if it would work for real, but that is what I was thinking. As long as it is plausible then you might be able to get away with it in your writing which could be a good thing because natural gas explosions are relatively common and an intentional dust explosion would be novel in comparison.