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Cordite
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Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant.
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Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant. Like gunpowder, Cordite is classified as a low explosive because of its slow burning rates and consequently low brisance. These produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The hot gases produced by burning gunpowder or Cordite generate sufficient pressure to propel a bullet or shell to its target, but not enough to destroy the barrel of the firearm, or gun.
Cordite was used initially in the .303 British, Mark I and II, standard rifle cartridge between 1891 and 1915; however shortages of cordite in World War I led to United States-developed smokeless powders being imported into the UK for use in rifle cartridges. Cordite was also used for large weapons, such as tank guns, artillery and naval guns. It has been used mainly for this purpose since the beginning of World War I by the UK and British Commonwealth countries. Its use was further developed in the early years of World War II, as 2-inch and 3-inch diameter Unrotated Projectiles for launching anti-aircraft weapons. Small Cordite rocket charges were also developed for ejector seats made by the Martin-Baker Company.
Cordite is now obsolete and it is no longer produced. Production ceased in the United Kingdom, around the end of the 20th century, with the closure of the last of the World War II Cordite factories, ROF Bishopton. However, Cordite propellant may still be encountered in the form of legacy ammunition dating from World War II onwards. The smell of Cordite is referenced erroneously in fiction to indicate the recent firing of weapons.
Adoption of smokeless powder by the British government
Replacements for gunpowder (Black powder)
Gunpowder, an explosive mixture of sulfur, charcoal and potassium nitrate (also known as saltpetre/saltpeter), was the original gun propellant employed in firearms and fireworks. It was used from about 10th or 11th century, onwards; but had a number of disadvantages. With the 19th century development of various "nitro explosives", based on the reaction of nitric acid mixtures on materials such as cellulose and glycerine, a search began for a replacement for gunpowder.
Early European smokeless powders
The first smokeless powder, Poudre B, was developed in 1884 by the French chemist Paul Vieille. It was made out of two forms of nitrocellulose (collodion and guncotton) softened with ethanol and ether and kneaded together. It was immediately adopted by the French military but it tended to become unstable over time. The rifle and cartridge developed to utilize this powder were known generically as the '8 mm Lebel', after the officer in charge of the development board, and were fielded in 1886.
The following year, 1887, Alfred Nobel invented and patented a smokeless propellant he called Ballistite. It was composed of 10% camphor, 45% nitroglycerine and 45% collodion (nitrocellulose). Over time the camphor tended to evaporate leaving an unstable explosive.
Development of cordite
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. However, neither of these smokeless powders were recommended for adoption by the Explosives Committee.
Abel and Sir James Dewar, who was also on the committee, developed and jointly patented in 1889 a new propellant consisting of 58% nitroglycerine, by weight, 37% guncotton and 5% vaseline. 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".
Cordite began as a double-base propellant and later triple-base cordites were developed. Cordite was made by combining two high explosives: nitrocellulose and nitroglycerine. Whilst Cordite is classified as an explosive, it is not employed as a high explosive. It is designed to deflagrate, or burn, to produce high pressure gases.
Nobel and Abel patent dispute
Alfred Bernhard Nobel sued Abel and Dewar over an alleged patent infringement. His patent specified that the nitrocellulose should be "of the well-known soluble kind". This dispute eventually reached 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
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, while thicker rods would burn more slowly and were used for longer barrels such as those used in artillery and naval guns.
Cordite (Mk I) and Cordite MD
The original Abel-Dewar formulation was soon superseded as it caused excessive gun barrel erosion. It has since become known as Cordite Mk I.
The composition of Cordite was changed to 65% guncotton and 30% nitroglycerine (keeping 5% vaseline) shortly after the end of the Second Boer War. This was known as Cordite MD (= MoDified).
Cordite MD cartridges typically weighed approximately 15% more than the cordite Mk I cartridges they replaced, to achieve the same muzzle velocity, due to the inherently less powerful nature of cordite MD.
Cordite MD is also obsolete.
Cordite RDB
During World War I acetone was in short supply in Great Britain and a new experimental form was developed. This was Cordite RDB (= Research Department formula B); which was 52% collodion, 42% nitroglycerine and 6% vaseline (Petroleum jelly). It was produced at HM Factory, Gretna; and the Royal Navy Cordite Factory, Holton Heath.
Cordite RDB, unfortunately, tended to become unstable if stored too long. Once acetone production increased, by the use of fermentation (see Chaim Weizmann), the older form of Cordite, Cordite MD, was brought back for use by the Royal Navy.
Cordite SC
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 or numbers, or both, after the SC. For example SC followed by a number was rod-shaped cord, with the number representing the diameter in Thou. SC T followed by two sets of numbers was tubular propellant with the numbers representing the two diameters in Thou.
Two-inch (approximately 50 mm) and three-inch (approximately 75 mm) diameter, Unrotated Projectiles, 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.
Cordite N
An important development during World War II was the addition of another explosive, nitroguanidine, to the mixture to form triple-base propellant 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
Cordite manufacture
UK Government factories
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.
In World War I a great Cordite factory, HM Factory, Gretna, which straddled the Scotland-England 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 Gretna and the Holton Heath Cordite factories closed at the end of World War I; and the Gretna factory was demolished.
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 Wrexham—were also opened. Cordite produced in these factories was sent to Filling Factories for filling into ammunition.
MoS Agency Factories and ICI Nobel, in World War II
The British Government set up additional Cordite factories, not under Royal Ordnance Factory control but as Agency Factories run on behalf of the Ministry of Supply (MoS). The company of ICI Nobel, at Ardeer, was asked in 1939 to construct and operate six factories in southern Scotland. Four of these six were involved in Cordite or firearm-propellant manufacture. The works at MoS Drungans (Dumfries) produced guncotton that was converted to Cordite at MoS Dalbeattie (triple-base cordite) and at MoS Powfoot (monobase granulated guncotton for small-arms). A smaller site at Girvan,South Ayrshire, now occupied by Grant's distillery, produced cordite and TNT. The ICI Ardeer site also had a mothballed World War I Government-owned Cordite factory.
35% of British Cordite produced between 1942 and 1945 came from Ardeer and these agency factories. ICI ran a similar works at Deer Park near Melbourne in Australia and in South Africa.
Overseas supplies
Additional sources of propellant were also sought from the British Commonwealth in both World War I and World War II. Canada, South Africa and Australia, had ICI-owned factories that, in particular, supplied large quantities of Cordite.
World War I
Canadian Explosives Limited was formed in 1910 to produce rifle cordite, at its Beloeil factory, for the Quebec Arsenal. By November 1915 production had been expanded to produce 350,000 lb (159,000 kg) of cordite per month for the Imperial Munitions Board.
The Imperial Munitions Board set up a number of additional explosives factories in Canada. It built The British Cordite Ltd factory at Nobel, Ontario, in 1916/1917, to produce Cordite. Production started in mid 1917.
Canadian Explosives Limited built an additional Cordite factory at Nobel, Ontario. Work stated in February 1918 and was finished on 24 August 1918. It was designed to produce 1,500,000 lb (681,000 kg) of Cordite per month.
World War II
The United States did not use Cordite, however, several ammunition filling factories were set up in Canada in World War II to fill American propellant supplied by the USA under Lend-Lease. India, Pakistan and Australia were also approached. Cordite was used in "Little Boy", the atomic bomb dropped on Hiroshima, Japan during World War II. A "gun" using Cordite fired a subcritical piece of U-235 into another to form a supercritical mass.
Production quantities
Large quantities of cordite were manufactured in both World Wars for use by the military.
Pre-World War I
Prior to World War I, most of the Cordite used by the British Government was produced in its own factories. Immediately prior to World War I, between 6,000 and 8,000 tons per year of Cordite were produced in the United Kingdom by private manufacturers; with between 1,000 and 1,500 tons per year being made by Nobel's Explosives, at Ardeer. However, private industry had the capability to produce about 10,000 tons per year; with Ardeer able to produce some 3,000 tons of this total.
World War I
At the start of World War I, Private industry in the UK was asked to produce 16,000 tons of cordite; and all the companies started to expand. HM Factory, Gretna, the largest propellant factory in the United Kingdom, which opened in 1916, was by 1917 producing 800 tons (812 tonne) of Cordite RDB per week (approximately 41,600 tons per year). The Royal Navy had its own factory at Royal Navy Cordite Factory, Holton Heath.
In 1910, Canadian Explosives Limited produced 3,000 lb (1,362 kg) of rifle Cordite per month at its Beloeil factory, for the Quebec Arsenal. By November 1915 production had been expanded to 350,000 lb (159,000 kg) of cordite per month (approximately 1,900 tonnes per year).
The Canadian Explosives Limited Cordite factory at Nobel, Ontario was designed to produce 1,500,000 lb (681 tonne) of Cordite per month (approximately 8,170 tonnes per year).
Between wars
HM Factory, Gretna and the Royal Navy Cordite Factory, Holton Heath both closed after the end of the war and the Gretna factory was dismantled. This left Waltham Abbey and Ardeer in production.
Bibliography
- Bowditch, M.R. and Hayward, L. (1996). A Pictorial record of the Royal Naval Cordite Factory: Holton Heath. Wareham: Finial Publishing. ISBN 1-900467-01-1.
- Brown, Donald, (1999), Somerset v Hitler: Secret Operations in the Mendips 1939 - 1945, Newbury: Countryside Books. ISBN 1-85306-590-0.
- Carnegie, David (1925). The History of Munitions Supply in Canada 1914-1918. London: Longmans, Green and Co.
- Cocroft, Wayne D. (2000). Dangerous Energy: The archaeology of gunpowder and military explosives manufacture. Swindon: English Heritage. ISBN 1-85074-718-0.
- Davis, Tenney L. (1943). The Chemistry of Powder and Explosives, Volume II, New York: John Wiley & Sons, and London: Chapman & Hall.
- Hartcup, Guy (1970). The Challenge of War: Scientific and Engineering Contributions to World War Two. Newton Abbot: David & Charles. ISBN 0-7153-4789-6.
- Reader, W.J. (1975). Imperial Chemical Industries: A History. Volume II; The First Quarter-Century 1926-1952. London: Oxford University Press. ISBN 0-19-215944-5.
- Ministry of Munitions of War, (1919). H.M. Factory, Gretna: Description of plant and process. Dumfries: J. Maxwell and Son, for His Majesty's Stationery Office.
- Rotter, Andrew J. (2008). Hiroshima: The World's Bomb. Oxford University Press. ISBN 0-19280-437-5
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