Cordite
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Cordite is a particular family of smokeless propellants made by combining two high explosives: nitrocellulose and nitroglycerin, i.e. it is a double-base propellant. However, Cordite N, a triple-base propellant is also used (see below). Cordite is classified as an explosive, but it is normally used as a propellant for guns and rockets.
Cordite was developed in Great Britain in the late 19th Century and has been used since World War I by Britain, and in British Commonwealth countries, as a military propellant for firearms, artillery and naval guns. Its use was further developed in the early years of World War II, as 2 inch and 3 inch diameter solid fuel rockets for launching anti aircraft weaponsBrown, Chapter 17. Small Cordite rocket charges were also developed for Ejector seats, made by the Martin-Baker Company. Cordite was used in the Little Boy atomic bomb dropped on Hiroshima.
Early history of smokeless powders
Poudre B
In 1886, French chemist Paul Vieille invented the first smokeless powder, called Poudre B (Poudre Blanche = white powder). It was made out of two forms of nitrocellulose (collodion and guncotton) softened with ethanol and ether and kneaded together, i.e. a single-base propellant. Three times more powerful than black powder and relatively free from vast quantities of smoke, Poudre B was a great improvement on black powder (or Poudre Noire = black powder).The reason that Poudre B was smokeless is that the combustion products were mainly gaseous, compared to around 60% solid products for black powder (e.g. potassium carbonate, potassium sulfate, etc). It was immediately adopted by the French military but it tended to become unstable over time and this led to many accidents; for example two battleships, the Jena and the Liberté, blew up in Toulon harbour in 1907 and 1911 respectively.
Alfred Nobel and Ballistite
In 1887, Alfred Nobel invented and Patented a smokeless propellant, he called Ballistite, which was composed of 10% camphor, 45% nitroglycerin and 45% collodion (nitrocellulose), i.e. a double-base propellant. His patent specified that the nitrocellulose should be "of the well-known soluble kind". Over time, the camphor tended to evaporate, leaving an unstable explosive.Nobel and Abel Patent dispute
Nobel sued Abel and Dewar over patent infringement (see Cordite Mk I below), eventually getting to the House of Lords in 1895, but lost because the words "of the well-known soluble kind" in his patent were taken to mean the soluble collodion and hence specifically excluded the insoluble guncotton.Cordite formulations
Abel and Cordite (Mk I)
A United Kingdom government committee, known as the "Explosives Committee", chaired by Sir Frederick Abel, monitored foreign developments in explosives, and obtained samples of Poudre B and Ballistite. Abel and Sir James Dewar, who was also on the committee, jointly patented in 1889 a new propellant, consisting of 58% nitroglycerin by weight, 37% guncotton and 5% vaseline in 1889. Using acetone as a solvent, it was extruded as spaghetti-like rods initially called "cord powder" or "the Committee's modification of Ballistite", but this was swiftly abbreviated to "Cordite". It was quickly discovered that the rate of burning could be varied by altering the surface area of the cordite. Narrow rods were used in small-arms and gave relatively fast burning, whilst thicker rods would burn more slowly and were used for longer barrels such as those used in artillery.This is now obsolete, as it caused excessive gun barrel erosion; other formulations of Cordite were produced and the original Abel / Dewar formulation became known as Cordite Mark I, Cordite Mk I.
Cordite MD
Cordite, Ballistite and Poudre B continued to be used in different armed forces for many years, but Cordite gradually became predominant. One problem was that early versions of cordite quickly eroded gun barrels. To combat this, the British changed the composition to 65% guncotton and 30% nitroglycerine (keeping 5% vaseline) in their version shortly after the end of the Second Boer War. This was known as Cordite MD (= MoDified). Cordite MD is also obsolete.Cordite RDB and Cordite SC
During the World War I, acetone was in short supply in Great Britain and so a new form was developed. This was Cordite RDB (= Research Department formula B); which was 52% collodion, 42% nitroglycerin and 6% vaseline (Petroleum jelly). It tended to become unstable if stored too long. Once acetone production increased by fermentation, (see Chaim Weizmann), the older form of Cordite replaced it.Research on solvent-free Cordite RDB continued primarily on the addition of stabilizers, which led to the type commonly used in World War II, onwards. In Great Britain this was known as Cordite SC (= Solventless Cordite). Cordite SC was produced in different shapes and sizes, so the particular geometry of Cordite SC was indicated by the use of letters and/or numbers after the SC. For example SC followed by a number was rod-shaped cord, with the number representing the diameter, in one-thousandths of an inch. SC T followed by two sets of numbers was tubular propellant, with the numbers representing the two diameters, in one-thousandths of an inch.
Two inch and three inch diameter rocket Cordite SC charges were developed, in great secrecy, in the later stages of WW II for anti-aircraft purposes; the so-called Z-gun batteries.
Great Britain changed to metric units in the 1960s, so there was a discontinuity in the propellant geometry numbering system.
In World War I, a great Cordite factory, HM Factory, Gretna Green, was opened on the England / Scotland border at Gretna to manufacture Cordite for the British Army and for British Commonwealth forces. A separate factory, The Royal Navy Cordite Factory, Holton Heath, was opened to manufacture Cordite for the Royal Navy. Both the Greta and the Holton Heath Cordite factories closed at the end of World War I.
By the start of World War II, Holton Heath had reopened and an additional factory for the Royal Navy, The Royal Navy Propellant Factory, Caerwent, opened at Caerwent, in Wales. A very large Royal Ordnance Factory, ROF Bishopton, was opened in Scotland to manufacture Cordite for the British Army and the Royal Air Force; a new Cordite factory at Waltham Abbey and two additional ROF's: ROF Ranskill and ROF Wexham. Cordite produced in these factories was sent to Filling Factories for filling into ammunition.
Additional sources of propellant were also sought from the British Commonwealth. The United States did not use Cordite, however several ammunition filling factories were set up in Canada to fill American propellant supplied by the USA under Lend-Lease. India, Pakistan and Australia were also approached.
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.Triple-base propellant and Cordite N
An important development during the Second World War was the addition of another explosive, nitroguanidine, to the mixture to form triple-base Cordites, or Cordite N. This solved two problems with the large naval guns of the day as fitted to capital ships. Nitroguanidine produces large amounts of nitrogen when heated, which had the benefit of reducing the muzzle flash, and its lower burning temperature greatly reduced the erosion of the gun barrel.Cordite charge design
to be addedCordite Manufacture
In Great Britain, Cordite was developed for military use at the Royal Arsenal, Woolwich and at the Waltham Abbey Royal Gunpowder Mills, from 1889 onwards. Notes
References
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