Gunpowder propellant

Numerous terrorist activities as well as many serious criminal offensives involve firearms. When a firearm is discharged, a variety of materials is emitted by the muzzle (accompanying the projectile), including primer and gunpowder (propellant) residues... 

They had never bothered to ponder the inconvenient fact, for instance, that the gunpowder propelling every bullet and the explosive charge inside every cannon shell were made from nitric acid, and that nitric acid was manufactured from nitrate that arrived on ships from Chile. The fragile supply lines across the Atlantic now were blocked by British warships. 

Gunpowder was first employed as a propellent explosive in guns, although later it was also employed for blasting. In neither case, however, does it detonate in the same way as the blasting explosives described in Part I, or the initiating explosives described in Part II of this book. 

Gunpowder was supplied in pellet form as a propellant and the substitutes were similarly manufactured. They were therefore called powders. Subsequent developments have led to the provision of propellent explosives in special and often massive form. Nevertheless, the term powder is still retained for their nomenclature, and the individual unit of the charge, no matter how large, is still called a grain. 

When black powder is used to propel rockets it is classed as a composite propellant (where the fuel and oxidiser are intimately mixed) and forms part of a rocket motor in which the powder is compressed to form a monolithic single grain inside a combustion chamber as shown in Figure 3.1. As well as gunpowder, the composite propellant mix will contain a binder which is used to improve the cohesion of the ingredients. Binders form a distinct phase and tend to reduce the sensitiveness of the propellant to shock and impact. When based on organic materials, as is normally the case, they will serve as part of the fuel component also. 

The constants "V and are dependent upon the chemical composition of the grains and their initial temperature. The burning rate equation (3.1) is based on the various empirical measurements and differs with the type of propellant. For one type of gunpowder the equation might be expressed as follows ... 

Although gunpowder remains the propellant of choice for the production of firework rockets, there has been development on military compositions since the beginning of the 19th century, notably in Europe. 

Of these, the most successful appeared in 1887 when Alfred Nobel patented a nitrocellulose propellant plasticised with nitroglycerine. Known as a double-base propellant, it is virtually smokeless, with a very high specific impulse as compared to gunpowder. Single-base propellants were developed in 1865 and 1890 by Schultz and Vieille respectively and these took the form of gelatinised nitrocellulose for use in firearms and mortars. 

The superiority of double-base propellant as compared to gunpowder is clearly reflected in the properties of the two products. For example the heat of reaction is about 900 as opposed to 700 calories g while the volume of gas produced is around 950 in comparison to 370 cm atm g at STP. The flame temperatures are listed as 3200 K and 2700 K respectively, while the specific impulse is about 1800 for smokeless propellant and bOONskg for gunpowder. 

Modern guns are more than 30% efficient, relying on smokeless propellants (where the gas volume at STP is around lOOOcm g and heat of explosion is at least 3000 Jg ). On the other hand, gunpowder will only produce about 400 cm g gas at STP, while the corresponding heat of explosion is approximately 1550 Jg ... 

Thus, in summary, the composition can be divided into propellant, emitter and additives. The propellant is invariably gunpowder, whilst the emitter might be carbon, steel, iron, aluminium, magnesium/ aluminium alloy or even titanium. Additives are often used to promote the visual effects and to cheapen the composition. 

BLACK POWDER (synonymous with Gunpowder) An intimately milled mixture of potassium nitrate, sulfur and charcoal that has propellant or explosive properties. 

Gunpowder was discovered by the Chinese many centuries ago, but they used it primarily for fireworks until it was imported to the West and used to blow up castles and then to propel projectiles. Explosives are solids that are endothermic with respect to their decomposition products. [We will consider the explosions of solids more in Chapter 10.] Typically explosives contain fuel atoms (C, H, and S) in close proximity to oxygen atoms (as nitrates and perchlorates) so that they will react to form CO2, H2O, and SO2, but only (one hopes) when intentionally ignited. Another class of exothermically decomposing solids is azides, and they are frequently used as igniters or fuses to heat up conventional explosives. 

The fire-arm of Rouen was, accdg to Greener (Ref 7, p 20), a small iron-forged weapon. It was shooting feathered iron arrows, loaded from muzzle, propelled by a charge of Gunpowder, which was put in a separate movable breech-block or chamber (See illustrations on pp 21 22 of Ref 7)... 

The first incendiary shot was a stone ball, preheated on a fire or by quicklime, and propelled from a cannon by a charge of gunpowder. In... 

Gunpowder, Brown. See BkPdr Modification, known as Brown-, Cocoa or Chocolate Powder described in Vol 2 of Encycl, p B173-L. It is also listed under CANNON PROPELLANT on p C30-L of Vol 2... 

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