Explosives Lecture Notes

Flashcards on Explosives

Explosives

Extremely fast combustion reaction where the fuel brings its own oxidizer, creating lots of gases.

Low explosives

Explosives that need confinement to explode and have an explosion slower than the speed of sound (1085 ft/s). They deflagrate, meaning they burn faster than combustion but slower than detonation.

High explosives

Explosives that don’t need confinement to explode and have an explosion faster than the speed of sound. They detonate, causing instantaneous conversion of solid or liquid fuel to gas, heat, and sound, creating a detonation wave.

VOE

The velocity of explosion, or VOE, is the speed at which an explosion travels.

VOD

Velocity of Detonation; the speed at which the detonation wave travels through an explosive.

Black powder

A common low explosive that needs confinement for deflagration. It can be initiated directly by heat, shock, or friction, or with another explosive like a primer in a bullet, creating a propelling effect.

Composed of potassium nitrate/sodium nitrate, sulfur, and charcoal in different proportions.

Black Powder

Nitrocellulose (Guncotton)

Used in some smokeless powders, made by nitrating cotton with nitric acid and cellulose. It burns very quickly with little residue.

Smokeless Powder

Used in most bullet/shotgun shells, with hundreds of different varieties. Additives include color, shape, number of explosives, holes, and base types.

Smokeless Powder - Base

Single base: nitrocellulose (guncotton)

Smokeless Powder - Base

Double base: + nitroglycerin

Smokeless Powder - Base

Triple base: + nitroguanidine (suppresses muzzle flash)

High Explosives

Creates a shock wave due to a fast chemical reaction, causing a pressure difference and a shattering effect (Brisance).

Primary and secondary explosives

Explosives divided based on how easy/hard they are to ignite. Primary explosives are most sensitive and used in detonators, while secondary explosives need more energy to start but are more powerful and require a detonator.

Dynamite

Long history – developed by Alfred Nobel in 1867

Dynamite

Usually nitroglycerin based mixed with: nitrates (sodium or ammonium to supply oxygen), Wood pulp to absorb liquid explosive, Ethylene glycol dinitrate to lower freezing point

RDX; Cyclo-Trimethylene Trinitramine

High brisance, VOD: 28,700 ft/s. Mixed with plasticizers to form C4.

PETN; Pentaerythritol Tetranitrate

VOD: 27,600 ft/s. Used in detonator caps and cords.

TNT; Trinitrotoluene

Very stable, “bullet safe”. Fine with water and heat. VOD: 22,600 ft/s

ANFO; Ammonium Nitrate Fuel Oil

Very stable, needs a detonator plus a booster to get going. VOD: 8000 ft/s to 15,600 ft/s. Can’t be used in wet conditions. Used in fertilizer bombs.

TATP; Triacetone triperoxide

Very sensitive, the more impure the more sensitive. Made from 2 widely available compounds, acetone and hydrogen peroxide. Used in “Shoe bomber”, London transit attacks, Paris Attacks.

Greiss test

Looks for nitrates or nitrites, turns pinkish red

Alcoholic KOH

Tests for nitroaromatics (TNT-like explosives) - Turns red-violet to red

DPA (Diphenylamine)

Tests for oxidizers (usually nitrates and nitrites) - Turn deep blue

Methylene Blue

Hydroxy radicals

Barium chloride

Carboniates and sulfuates

IMS – Ion Mobility Spectrometry

Ionized with beta rays from radioactive nickel, allowed to drift down a tube, electric field applied

Microscopy

Especially for unburned low explosives, smokeless powders come in unique shapes

Extraction

For all other methods need the explosive/residues isolated. Swab and then rinse, rinse directly. Usually acetone and water. Get different compounds.