Gunpowder

Gunpowder burns producing a subsonic deflagration[?] wave rather than a supersonic detonation[?] wave as do high explosives. This reduces peak pressures in a gun, but makes it less suitable for shattering rock or fortifications.

Smokeless powder consists of almost pure nitrocellulose, frequently combined with up to 20 percent nitroglycerin corned into small spherical balls or extruded into cylinders or flakes using solvents such as ether. Smokeless powder burns only on the surfaces of the granules. Larger granules burn more slowly, and the burn rate is further controlled by flame-deterrent coatings which retard burning slightly. The intent is to regulate the burn rate so that a more or less constant pressure is exerted on the propelled projectile as long as it is in the barrel so as to obtain the highest velocity. Cannon powder has the largest granules, up to thumb-sized cylinders with seven perforations (one central and the other six in a circle halfway to the outside of the cylinder's end faces). The perforations stabilize the burn rate because as the outside burns inward (thus shrinking the burning surface area) the inside is burning outward (thus increasing the burning surface area, but faster, so as to fill up the increasing volume of barrel presented by the departing projectile). Fast-burning pistol powders are made by extruding shapes with more area such as flakes or by flattening the spherical granules. Drying is usually performed under a vacuum. The solvents are condensed and recycled. The granules are also coated with graphite to prevent static electricity sparks from causing undesired ignitions.

Black powder consists of the granular ingredients sulfur (S), charcoal (provides carbon to the reaction) and saltpeter (saltpetre, potassium nitrate, KNO₃). The optimum proportions for gunpowder are : Saltpetre 74.64%, Sulphur 11.85%, Charcoal 13.51%.

The basic ratio is:

2 parts Sulfur : 3 parts Charcoal : 15 parts Saltpetre

Black powder is also corned to change its firing rate. Corning black powder is very dangerous because black powder explodes when ground. Corning must be done with the powder wet.

Although black powder is not a true high explosive, the U.S. Department of Transportation classifies it as a "Class A High Explosive" for shipment because it is so easily set off.

History

Gunpowder was first discovered in China in the 9th century. The discovery appears to have been by accident by alchemists seeking the elixir of immortality, and the first references to gunpowder appear as warnings in alchemy texts not to mix certain materials together. By the 10th century, gunpowder began to be used for military purposes in China in the form of rockets and explosive bombs fired from catapults. The first reference to cannon appears in 1126 when oil bamboo tubes were used to launch missiles at the enemy. Eventually bamboo tubes were replaced by metal tubes, and the oldest cannon in China dates from 1290. From China, the military use of gunpower appears to have spread to Japan and Europe. It was used by the Mongols against the Hungarians in 1241 and was mentioned by Roger Bacon in 1248. By the mid 14th century, early cannons are mentioned extensively both in Europe and in China.

In China as in Europe, the use of gunpowder to produce firearms and cannon was delayed by difficulties in creating metal tubes that would contain an explosion. This problem may have led to the false myth that the Chinese used their discovery only for the manufacture of fireworks. In fact, gunpowder powered cannon and rockets were extensively used in the Mongol conquests of the 13th century and were a feature of East Asian warfare afterwards. The short squat and thick city walls of Beijing for example, were specifically designed to withstand an artillery attack.

The 15th through 17th century saw widespread development in gunpowder technology both in Europe and the Far East. Advancements in metallugy lead to small weapons and the development of muskets. Cannon technology in Europe gradually outpaced that of China and these technological improvements transfered back to China through Jesuit missionaries who were put in charge of cannon manufacture by the late Ming and early Qing emperors.