Smokeless powder
Smokeless powder is a type of
Despite its name, smokeless powder is not completely free of smoke;[3]: 44 while there may be little noticeable smoke from small-arms ammunition, smoke from artillery fire can be substantial.
Invented in 1884 by
Smokeless powders are typically classified as division 1.3 explosives under the
Smokeless powder made autoloading firearms with many moving parts feasible (which would otherwise jam or seize under heavy black powder fouling). Smokeless powder allowed the development of modern semi- and fully automatic firearms and lighter breeches and barrels for artillery.
History
Before the widespread introduction of smokeless powder the use of gunpowder or black powder caused many problems on the battlefield. Military commanders since the Napoleonic Wars reported difficulty with giving orders on a battlefield obscured by the smoke of firing. Visual signals could not be seen through the thick smoke from the gunpowder used by the guns. Unless there was a strong wind, after a few shots, soldiers using gunpowder ammunition would have their view obscured by a huge cloud of smoke. Snipers and other operators firing from concealed positions risked revealing their locations with a cloud of smoke. Gunpowder burns in a relatively inefficient process that produces lower pressures, making it about one third as powerful as the same amount of smokeless powder.[5] A significant portion of the combustion products from gunpowder are solids, that are also hygroscopic, meaning it attracts moisture from the air, making cleaning mandatory after every use to prevent water accumulation in the barrel that can lead to corrosion and premature failure. These solids are also behind gunpowder's tendency to produce severe fouling that causes breech-loading actions to jam and can make reloading difficult.
Nitroglycerine and guncotton
A major step forward was the invention of
English interest languished after an explosion destroyed the Faversham factory in 1847. Austrian Baron Wilhelm Lenk von Wolfsberg built two guncotton plants producing artillery propellent, but it too was dangerous under field conditions, and guns that could fire thousands of rounds using black powder would reach the end of their service life after only a few hundred shots with the more powerful guncotton. Small arms could not withstand the pressures generated by guncotton.
After one of the Austrian factories blew up in 1862, Thomas Prentice & Company began manufacturing guncotton in Stowmarket in 1863; and British War Office chemist Sir Frederick Abel began thorough research at Waltham Abbey Royal Gunpowder Mills leading to a manufacturing process that eliminated the impurities in nitrocellulose making it safer to produce and a stable product safer to handle. Abel patented this process in 1865 when the second Austrian guncotton factory exploded. After the Stowmarket factory exploded in 1871, Waltham Abbey began production of guncotton for torpedo and mine warheads.[4]: 141–144
Improvements
In 1863,
In 1882, the Explosives Company at Stowmarket patented an improved formulation of nitrated cotton gelatinised by ether-alcohol with nitrates of potassium and barium. These propellants were suitable for shotguns but not rifles,[8]: 138–139 because rifling results in resistance to a smooth expansion of the gas, which is reduced in smoothbore shotguns.
In 1884,
Meanwhile, in 1887,
Britain conducted trials on all the various types of propellant brought to their attention, but were dissatisfied with them all and sought something superior to all existing types. In 1889, Sir
The Anglo-American Explosives Company began manufacturing its shotgun powder in
In 1897, United States Navy Lieutenant
Characteristics
The properties of the propellant are greatly influenced by the size and shape of its pieces. The specific surface area of the propellant influences the speed of burning, and the size and shape of the particles determine the specific surface area. By manipulation of the shape it is possible to influence the burning rate and hence the rate at which pressure builds during combustion. Smokeless powder burns only on the surfaces of the pieces. Larger pieces burn more slowly, and the burn rate is further controlled by flame-deterrent coatings that 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. 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).[3]: 41–43 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.[6]: 306
Smokeless powder does not leave the thick, heavy
Faster-burning propellants generate higher temperatures and higher pressures, however they also increase wear on gun barrels.[citation needed]
Nitrocellulose deteriorates with time, yielding acidic byproducts. Those byproducts catalyze the further deterioration, increasing its rate. The released heat, in case of bulk storage of the powder, or too large blocks of solid propellant, can cause self-ignition of the material. Single-base nitrocellulose propellants are hygroscopic and most susceptible to degradation; double-base and triple-base propellants tend to deteriorate more slowly.[6]: 313 To neutralize the decomposition products, which could otherwise cause corrosion of metals of the cartridges and gun barrels, calcium carbonate is added to some formulations.[12]
To prevent buildup of the deterioration products, stabilizers are added. Diphenylamine is one of the most common stabilizers used.[13][14] Nitrated analogs of diphenylamine formed in the process of stabilizing decomposing powder are sometimes used as stabilizers themselves.[3]: 28 [6]: 310 The stabilizers are added in the amount of 0.5–2% of the total amount of the formulation; higher amounts tend to degrade its ballistic properties. The amount of the stabilizer is depleted with time with substantial changes of ballistic properties.[15] Propellants in storage should be periodically tested for the amount of stabilizer remaining,[3]: 46 as its depletion may lead to auto-ignition of the propellant.[6]: 308 Moisture changes the stabilizers comsumption over time. [16]
Composition
Propellants using
Propellants mixtures containing nitrocellulose and nitroglycerin (detonation velocity 7,700 m/s (25,260 ft/s), RE factor 1.54) as explosive propellant ingredients are known as double-base powder. Alternatively diethylene glycol dinitrate (detonation velocity 6,610 m/s (21,690 ft/s), RE factor 1.17) can be used as a nitroglycerin replacement when reduced flame temperatures without sacrificing chamber pressure are of importance.[6]: 298 Reduction of flame temperature significantly reduces barrel erosion and hence wear.[7]: 30
During the 1930s, triple-base propellant containing nitrocellulose, nitroglycerin or diethylene glycol dinitrate, and a substantial quantity of nitroguanidine (detonation velocity 8,200 m/s (26,900 ft/s), RE factor 0.95) as explosive propellant ingredients was developed. These "cold propellant" mixtures have reduced flash and flame temperature without sacrificing chamber pressure compared to single- and double-base propellants, albeit at the cost of more smoke. In practice, triple base propellants are reserved mainly for large caliber ammunition such as used in (naval) artillery and tank guns, which suffer from bore erosion the most. During World War II, it had some use by British artillery. After that war it became the standard propellant in all British large caliber ammunition designs except small-arms. Most western nations, except the United States, followed a similar path.[citation needed]
In the late 20th century new propellant formulations started to appear. These are based on nitroguanidine and high explosives of the RDX type (detonation velocity 8,750 m/s (28,710 ft/s), RE factor 1.60).[citation needed]
Detonation velocities are of limited value in assessing the reaction rates of nitrocellulose propellants formulated to avoid detonation. Although the slower reaction is often described as burning because of similar gaseous end products at elevated temperatures, the decomposition differs from combustion in an oxygen atmosphere. Conversion of nitrocellulose propellants to high-pressure gas proceeds from the exposed surface to the interior of each solid particle in accordance with Piobert's law. Studies of solid single- and double-base propellant reactions suggest reaction rate is controlled by heat transfer through the temperature gradient across a series of zones or phases as the reaction proceeds from the surface into the solid. The deepest portion of the solid experiencing heat transfer melts and begins phase transition from solid to gas in a foam zone. The gaseous propellant decomposes into simpler molecules in a surrounding fizz zone. Energy is released in a luminous outer flame zone where the simpler gas molecules react to form conventional combustion products like steam and carbon monoxide.[17] The foam zone acts as an insulator slowing the rate of heat transfer from the flame zone into the unreacted solid. Reaction rates vary with pressure; because the foam allows less effective heat transfer at low pressure, with greater heat transfer as higher pressures compress the gas volume of that foam. Propellants designed for a minimum heat transfer pressure may fail to sustain the flame zone at lower pressures.[18]
The energetic components used in smokeless propellants include nitrocellulose (the most common), nitroglycerin, nitroguanidine, DINA (bis-nitroxyethylnitramine; diethanolamine dinitrate, DEADN; DHE), Fivonite (2,2,5,5-tetramethylol-cyclopentanone tetranitrate, CyP), DGN (diethylene glycol dinitrate), and acetyl cellulose.[19]
Deterrents (or moderants) are used to slow the burning rate. Deterrents include centralites (symmetrical diphenyl urea—primarily diethyl or dimethyl), dibutyl phthalate, dinitrotoluene (toxic and carcinogenic), akardite (asymmetrical diphenyl urea), ortho-Tolyl urethane,: 174 and polyester adipate.[19] Camphor was formerly used but is now obsolete.[7]
Stabilizers prevent or slow down self-decomposition. These include diphenylamine, petroleum jelly, calcium carbonate, magnesium oxide, sodium bicarbonate, and beta-Naphthol methyl ether[19] Obsolete stabilizers include amyl alcohol and aniline.[6]
Wear reduction materials including wax, talc and titanium dioxide are added to lower the wear of the gun barrel liners. Large guns use polyurethane jackets over the powder bags.[20]
Other additives include ethyl acetate (a solvent for manufacture of spherical powder), rosin (a surfactant to hold the grain shape of spherical powder) and graphite (a lubricant to cover the grains and prevent them from sticking together, and to dissipate static electricity).[6]
Flash reduction
Flash reducers dim muzzle flash, the light emitted in the vicinity of the muzzle by the hot propellant gases and the chemical reactions that follow as the gases mix with the surrounding air. Before projectiles exit, a slight pre-flash may occur from gases leaking past the projectiles. Following muzzle exit, the heat of gases is usually sufficient to emit visible radiation: the primary flash. The gases expand but as they pass through the Mach disc, they are re-compressed to produce an intermediate flash. Hot, combustible gases (e.g. hydrogen and carbon-monoxide) may follow when they mix with oxygen in the surrounding air to produce the secondary flash, the brightest. The secondary flash does not usually occur with small arms.[21]: 55–56
Nitrocellulose contains insufficient oxygen to completely oxidize its carbon and hydrogen. The oxygen deficit is increased by addition of graphite and organic stabilizers. Products of combustion within the gun barrel include flammable gasses like hydrogen and carbon monoxide. At high temperature, these flammable gasses will ignite when turbulently mixed with atmospheric oxygen beyond the muzzle of the gun. During night engagements, the flash produced by ignition can reveal the location of the gun to enemy forces[6]: 322–323 and cause temporary night-blindness among the gun crew by photo-bleaching visual purple.[22]
Flash suppressors are commonly used on small arms to reduce the flash signature, but this approach is not practical for artillery. Artillery muzzle flash up to 150 feet (46 m) from the muzzle has been observed, and can be reflected off clouds and be visible for distances up to 30 miles (48 km).[6]: 322–323 For artillery, the most effective method is a propellant that produces a large proportion of inert nitrogen at relatively low temperatures that dilutes the combustible gases. Triple based propellants are used for this because of the nitrogen in the nitroguanidine.[21]: 59–60
Flash reducers include potassium chloride, potassium nitrate, potassium sulfate,[7] and potassium bitartrate (potassium hydrogen tartrate: a byproduct of wine production formerly used by French artillery).[6] Before the use of triple based propellants, the usual method of flash reduction was to add inorganic salts like potassium chloride so their specific heat capacity might reduce the temperature of combustion gasses and their finely divided particulate smoke might block visible wavelengths of radiant energy of combustion.[6]: 323–327
All flash reducers have a disadvantage: the production of smoke.[6]
Manufacturing
Smokeless powder may be
The United States Navy manufactured single-base tubular powder for naval artillery at
Unreacted acid was removed from pyrocellulose pulp by a multistage draining and water washing process similar to that used in
Alcohol and ether were then evaporated from "green" powder grains to a remaining solvent concentration between 3 percent for rifle powders and 7 percent for large artillery powder grains. Burning rate is inversely proportional to solvent concentration. Grains were coated with electrically conductive graphite to minimize generation of static electricity during subsequent blending. "Lots" containing more than ten tonnes of powder grains were mixed through a tower arrangement of blending hoppers to minimize ballistic differences. Each blended lot was then subjected to testing to determine the correct loading charge for the desired performance.[3]: 35–41 [6]: 293 & 306
Military quantities of old smokeless powder were sometimes reworked into new lots of propellants.
Modern smokeless powder is produced in the United States by St. Marks Powder, Inc. owned by General Dynamics.[25]
See also
References
- ^ Hatcher, Julian S. and Barr, Al Handloading Hennage Lithograph Company (1951) p.34
- ISBN 0-935998-34-9.
- ^ a b c d e f g h i Sharpe, Philip B. Complete Guide to Handloading 3rd Edition (1953) Funk & Wagnalls
- ^ "Black Powder vs. Smokeless Powder | Comparing Gunpowder Types, Bob Shell, Tuesday, October 13, 2015". Archived from the original on 26 November 2022. Retrieved 10 August 2018.
- ^ a b c d e f g h i j k l m n o p q r s t u Davis, Tenny L. The Chemistry of Powder & Explosives (1943)
- ^ a b c d e f Davis, William C., Jr. Handloading National Rifle Association of America (1981)
- ^ a b c d e Hogg, Oliver F. G. Artillery: Its Origin, Heyday and Decline (1969)
- ^ Manufacture of explosive, H. S. Maxim
- ^ smokeless powder
- ^ "Laflin & Rand Powder Company". DuPont. Archived from the original on 29 February 2012. Retrieved 24 February 2012.
- ^ Watters, Daniel E. "The Great Propellant Controversy". The Gun Zone. Archived from the original on 22 July 2013. Retrieved 29 June 2013.
- ISSN 0737-0652.
- ISSN 0737-0652.
- .
- ISSN 0969-0239.
- ^ "Propellant Properties" (PDF). Nevada Aerospace Science Associates. Archived from the original (PDF) on 26 July 2014. Retrieved 19 January 2017.
- ISBN 978-0854041275.
- ^ a b c d Campbell, John Naval Weapons of World War Two (1985
- ^ a b Moss G. M., Leeming D. W., Farrar C. L. Military Ballistics (1969)
- ISBN 0-87021-450-0.
- ^ Matunas, E. A. Winchester-Western Ball Powder Loading Data Olin Corporation (1978) p.3
- ^ Wolfe, Dave Propellant Profiles Volume 1 Wolfe Publishing Company (1982) pages 136–137
- ^ General Dynamics Commercial Powder Applications Archived 16 November 2017 at the Wayback Machine.
Bibliography
- Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.
- Davis, Tenney L. (1943). The Chemistry of Powder & Explosives (Angriff Press [1992] ed.). John Wiley & Sons Inc. ISBN 0-913022-00-4.
- Dallman, John (2006). "Question 27/05: "Flashless" Propellant". Warship International. XLIII (3): 246. ISSN 0043-0374.
- Davis, William C. Jr. (1981). Handloading. National Rifle Association of America. ISBN 0-935998-34-9.
- Fairfield, A. P., CDR USN (1921). Naval Ordnance. Lord Baltimore Press.
{{cite book}}
: CS1 maint: multiple names: authors list (link) - Gibbs, Jay (2010). "Question 27/05: "Flashless" Propellant". Warship International. XLVII (3): 217. ISSN 0043-0374.
- Grobmeier, A. H. (2006). "Question 27/05: "Flashless" Propellant". Warship International. XLIII (3): 245. ISSN 0043-0374.
- Grulich, Fred (2006). "Question 27/05: "Flashless" Propellant". Warship International. XLIII (3): 245–246. ISSN 0043-0374.
- Hatcher, Julian S. & Barr, Al (1951). Handloading. Hennage Lithograph Company.
- Matunas, E. A. (1978). Winchester-Western Ball Powder Loading Data. Olin Corporation.
- Wolfe, Dave (1982). Propellant Profiles Volume 1. Wolfe Publishing Company. ISBN 0-935632-10-7.
External links
- The Manufacture of Smokeless Powders and their Forensic Analysis: A Brief Review. Robert M. Heramb, Bruce R. McCord
- Hudson Maxim papers Archived 9 March 2018 at the Wayback Machine (1851–1925) at Hagley Museum and Library. Collection includes material relating to Maxim's patent on the process of making smokeless powder.