Propellant

From Wikipedia, the free encyclopedia

A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the engine that expels the propellant is called a reaction engine. Although technically a propellant is the reaction mass used to create thrust, the term "propellant" is often used to describe a substance which contains both the reaction mass and the fuel that holds the energy used to accelerate the reaction mass. For example, the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, although the propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two distinct concepts.

Vehicles can use propellants to move by ejecting a propellant backwards which creates an opposite force that moves the vehicle forward. Projectiles can use propellants that are expanding gases which provide the motive force to set the projectile in motion. Aerosol cans use propellants which are fluids that are compressed so that when the propellant is allowed to escape by releasing a valve, the energy stored by the compression moves the propellant out of the can and that propellant forces the aerosol payload out along with the propellant. Compressed fluid may also be used as a simple vehicle propellant, with the potential energy that is stored in the compressed fluid used to expel the fluid as the propellant. The energy stored in the fluid was added to the system when the fluid was compressed, such as compressed air. The energy applied to the pump or thermal system that is used to compress the air is stored until it is released by allowing the propellant to escape. Compressed fluid may also be used only as energy storage along with some other substance as the propellant, such as with a water rocket, where the energy stored in the compressed air is the fuel and the water is the propellant.

In electrically powered spacecraft, electricity is used to accelerate the propellant. An electrostatic force may be used to expel positive ions, or the Lorentz force may be used to expel negative ions and electrons as the propellant. Electothermal engines use the electromagnetic force to heat low molecular weight gases (e.g. hydrogen, helium, ammonia) into a plasma and expel the plasma as propellant. In the case of a resistojet rocket engine, the compressed propellant is simply heated using resistive heating as it is expelled to create more thrust.

In chemical rockets and aircraft, fuels are used to produce an energetic gas that can be directed through a nozzle, thereby producing thrust. In rockets, the burning of rocket fuel produces an exhaust, and the exhausted material is usually expelled as a propellant under pressure through a nozzle. The exhaust material may be a gas, liquid, plasma, or a solid. In powered aircraft without propellers such as jets, the propellant is usually the product of the burning of fuel with atmospheric oxygen so that the resulting propellant product has more mass than the fuel carried on the vehicle.

Proposed photon rockets would use the relativistic momentum of photons to create thrust. Even though photons do not have mass, they can still act as a propellant because they move at relativistic speed, i.e., the speed of light. In this case Newton's third Law of Motion is inadequate to model the physics involved and relativistic physics must be used.

In chemical rockets, chemical reactions are used to produce energy which creates movement of a fluid which is used to expel the products of that chemical reaction (and sometimes other substances) as propellants. For example, in a simple hydrogen/oxygen engine, hydrogen is burned (oxidized) to create H₂O and the energy from the chemical reaction is used to expel the water (steam) to provide thrust. Often in chemical rocket engines, a higher molecular mass substance is included in the fuel to provide more reaction mass.

Rocket propellant may be expelled through an expansion nozzle as a cold gas, that is, without energetic mixing and combustion, to provide small changes in velocity to spacecraft by the use of cold gas thrusters, usually as maneuvering thrusters.

To attain a useful density for storage, most propellants are stored as either a solid or a liquid.

Vehicle propellants

Main articles: Rocket propellant and Jet propulsion

A rocket propellant is a mass that is expelled from a vehicle, such as a rocket, in such a way as to create a thrust in accordance with Newton's third law of motion, and "propel" the vehicle forward. The engine that expels the propellant is called a reaction engine. Although the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two distinct concepts.

In electrically powered spacecraft, electricity is used to accelerate the propellant. An electrostatic force may be used to expel positive ions, or the Lorentz force may be used to expel negative ions and electrons as the propellant. Electothermal engines use the electromagnetic force to heat low molecular weight gases (e.g. hydrogen, helium, ammonia) into a plasma and expel the plasma as propellant. In the case of a resistojet rocket engine, the compressed propellant is simply heated using resistive heating as it is expelled to create more thrust.

In chemical rockets and aircraft, fuels are used to produce an energetic gas that can be directed through a nozzle, thereby producing thrust. In rockets, the burning of rocket fuel produces an exhaust, and the exhausted material is usually expelled as a propellant under pressure through a nozzle. The exhaust material may be a gas, liquid, plasma, or a solid. In powered aircraft without propellers such as jets, the propellant is usually the product of the burning of fuel with atmospheric oxygen so that the resulting propellant product has more mass than the fuel carried on the vehicle.

The propellant or fuel may also simply be a compressed fluid, with the potential energy that is stored in the compressed fluid used to expel the fluid as the propellant. The energy stored in the fluid was added to the system when the fluid was compressed, such as compressed air. The energy applied to the pump or thermal system that is used to compress the air is stored until it is released by allowing the propellant to escape. Compressed fluid may also be used only as energy storage along with some other substance as the propellant, such as with a water rocket, where the energy stored in the compressed air is the fuel and the water is the propellant.

Proposed photon rockets would use the relativistic momentum of photons to create thrust. Even though photons do not have mass, they can still act as a propellant because they move at relativistic speed, i.e., the speed of light. In this case Newton's third Law of Motion is inadequate to model the physics involved and relativistic physics must be used.

In chemical rockets, chemical reactions are used to produce energy which creates movement of a fluid which is used to expel the products of that chemical reaction (and sometimes other substances) as propellants. For example, in a simple hydrogen/oxygen engine, hydrogen is burned (oxidized) to create H₂O and the energy from the chemical reaction is used to expel the water (steam) to provide thrust. Often in chemical rocket engines, a higher molecular mass substance is included in the fuel to provide more reaction mass.

Rocket propellant may be expelled through an expansion nozzle as a cold gas, that is, without energetic mixing and combustion, to provide small changes in velocity to spacecraft by the use of cold gas thrusters, usually as maneuvering thrusters.

To attain a useful density for storage, most propellants are stored as either a solid or a liquid.

Propellants may be energized by chemical reactions to expel solid, liquid or gas. Electrical energy may be used to expel gases, plasmas, ions, solids or liquids. Photons may be used to provide thrust via relativistic momentum.

Chemically powered

Solid propellant

Further information: Solid fuel and Solid-fuel rocket

• Composite propellants made from a solid oxidizer such as ammonium perchlorate or ammonium nitrate, a synthetic rubber such as HTPB, PBAN, or Polyurethane (or energetic polymers such as polyglycidyl nitrate or polyvinyl nitrate for extra energy), optional high-explosive fuels (again, for extra energy) such as RDX or nitroglycerin, and usually a powdered metal fuel such as aluminum.
• Some amateur propellants use potassium nitrate, combined with sugar, epoxy, or other fuels and binder compounds.
• Potassium perchlorate has been used as an oxidizer, paired with asphalt, epoxy, and other binders.

Propellants that explode in operation are of little practical use currently, although there have been experiments with Pulse Detonation Engines. Also the newly synthesized bishomocubane based compounds are under consideration in the research stage as both solid and liquid propellants of the future.

Grain

Solid fuel/propellants are used in forms called grains. A grain is any individual particle of fuel/propellant regardless of the size or shape. The shape and size of a grain determines the burn time, amount of gas, and rate of produced energy from the burning of the fuel and, as a consequence, thrust vs time profile.

There are three types of burns that can be achieved with different grains.

Progressive burn

Usually a grain with multiple perforations or a star cut in the center providing a lot of surface area.

Degressive burn

Usually a solid grain in the shape of a cylinder or sphere.

Neutral burn

Usually a single perforation; as outside surface decreases the inside surface increases at the same rate.

Composition

There are four different types of solid fuel/propellant compositions:

Single-based fuel/propellant

A single based fuel/propellant has nitrocellulose as its chief explosives ingredient. Stabilizers and other additives are used to control the chemical stability and enhance its properties.

Double-based fuel/propellant

Double-based fuel/propellants consist of nitrocellulose with nitroglycerin or other liquid organic nitrate explosives added. Stabilizers and other additives are also used. Nitroglycerin reduces smoke and increases the energy output. Double-based fuel/propellants are used in small arms, cannons, mortars and rockets.

Triple-based fuel/propellant

Triple-based fuel/propellants consist of nitrocellulose, nitroguanidine, nitroglycerin or other liquid organic nitrate explosives. Triple-based fuel/propellants are used in cannons.

Composite

Composites do not utilize nitrocellulose, nitroglycerin, nitroguanidine or any other organic nitrate as the primary constituent. Composites usually consist of a fuel such as metallic aluminum, a combustible binder such as synthetic rubber or HTPB, and an oxidizer such as ammonium perchlorate. Composite fuel/propellants are used in large rocket motors. In some applications, such as the US SLBM Trident II missile, nitroglycerin is added to the aluminum and ammonium perchlorate composite as an energetic plasticizer.

Liquid propellant

Further information: liquid fuel and liquid-propellant rocket

In rockets, three main liquid bipropellant combinations are used: cryogenic oxygen and hydrogen, cryogenic oxygen and a hydrocarbon, and storable propellants.

Cryogenic oxygen-hydrogen combination system

Used in upper stages and sometimes in booster stages of space launch systems. This is a nontoxic combination. This gives high specific impulse and is ideal for high-velocity missions

Cryogenic oxygen-hydrocarbon propellant system

Used for many booster stages of space launch vehicles as well as a smaller number of second stages. This combination of fuel/oxidizer has high density and hence allows for a more compact booster design.

Storable propellant combinations

Used in almost all bipropellant low-thrust, auxiliary or reaction control rocket engines, as well as in some in large rocket engines for first and second stages of ballistic missiles. They are instant-starting and suitable for long-term storage.

Propellant combinations used for liquid propellant rockets include:

• Liquid oxygen and liquid hydrogen
• Liquid oxygen and kerosene or RP-1
• Liquid oxygen and ethanol
• Liquid oxygen and methane
• Hydrogen peroxide and mentioned above alcohol or RP-1
• Red fuming nitric acid (RFNA) and kerosene or RP-1
• RFNA and Unsymmetrical dimethylhydrazine (UDMH)
• Dinitrogen tetroxide and UDMH, MMH, and/or hydrazine

Common monopropellant used for liquid rocket engines include:

• Hydrogen peroxide
• Hydrazine
• Red fuming nitric acid (RFNA)

Electrically powered

Main article: Electrically powered spacecraft propulsion

Electrically powered reactive engines use a variety of usually ionized propellants, including atomic ions, plasma, electrons, or small droplets or solid particles as propellant.

Electrostatic

Main article: Ion thruster

If the acceleration is caused mainly by the Coulomb force (i.e. application of a static electric field in the direction of the acceleration) the device is considered electrostatic. The types of electrostatic drives and their propellants:

• Gridded ion thruster – using positive ions as the propellant, accelerated by an electrically charged grid
  • NASA Solar Technology Application Readiness (NSTAR) – positive ions accelerated using high-voltage electrodes
  • HiPEP – using positive ions as the propellant, created using microwaves
  • Radiofrequency ion thruster – generalization of HiPEP
• Hall-effect thruster, including its subtypes Stationary Plasma Thruster (SPT) and Thruster with Anode Layer (TAL) – use the Hall effect to orient electrons to create positive ions for propellant
• Colloid ion thruster – electrostatic acceleration of droplets of liquid salt as the propellant
• Field-emission electric propulsion – using electrodes to accelerate ionized liquid metal as a propellant
• Nano-particle field extraction thruster – using charged cylindrical carbon nanotubes as propellant

Electrothermal

These are engines that use electromagnetic fields to generate a plasma which is used as the propellant. They use a nozzle to direct the energized propellant. The nozzle itself may be composed simply of a magnetic field. Low molecular weight gases (e.g. hydrogen, helium, ammonia) are preferred propellants for this kind of system.

• Resistojet – using a usually inert compressed propellant that is energized by simple resistive heating
• Arcjet – uses (usually) hydrazine or ammonia as a propellant which is energized with an electrical arc
• Microwave – a type of Radiofrequency ion thruster
• Variable specific impulse magnetoplasma rocket (VASIMR) – using microwave-generated plasma as the propellant and magnetic field to direct its expulsion

Electromagnetic

Main article: Plasma propulsion engine

Electromagnetic thrusters use ions as the propellant, which are accelerated by the Lorentz force or by magnetic fields, either of which is generated by electricity:

• Electrodeless plasma thruster – a complex system that uses cold plasma as a propellant that is accelerated by ponderomotive force
• Magnetoplasmadynamic thruster – propellants include xenon, neon, argon, hydrogen, hydrazine, or lithium; expelled using the Lorentz force
• Pulsed inductive thruster – because this reactive engine uses a radial magnetic field, it acts on both positive and negative particles and so it may use a wide range of gases as a propellant including water, hydrazine, ammonia, argon, xenon and many others
• Pulsed plasma thruster – uses a Teflon plasma as a propellant, which is created by an electrical arc and expelled using the Lorentz force
• Helicon Double Layer Thruster – a plasma propellant is generated and excited from a gas using a helicon induced by high frequency band radiowaves which form a magnetic nozzle in a cylinder

Nuclear

Nuclear reactions may be used to produce the energy for the expulsion of the propellants. Many types of nuclear reactors have been used/proposed to produce electricity for electrical propulsion as outlined above. Nuclear pulse propulsion uses a series of nuclear explosions to create large amounts of energy to expel the products of the nuclear reaction as the propellant. Nuclear thermal rockets use the heat of a nuclear reaction to heat a propellant. Usually the propellant is hydrogen because the force is a function of the energy irrespective of the mass of the propellant, so the lightest propellant (hydrogen) produces the greatest specific impulse.

Photonic

See also: Laser propulsion and Photon rocket

A photonic reactive engine uses photons as the propellant and their discrete relativistic energy to produce thrust.

Projectile propellants

See also: Gunpowder, Smokeless powder, and Cartridge (firearms) § Propellant

Compressed fluid propellants

Compressed fluid or compressed gas propellants are pressurized physically, by a compressor, rather than by a chemical reaction. The pressures and energy densities that can be achieved, while insufficient for high-performance rocketry and firearms, are adequate for most applications, in which case compressed fluids offer a simpler, safer, and more practical source of propellant pressure.

A compressed fluid propellant may simply be a pressurized gas, or a substance which is a gas at atmospheric pressure, but stored under pressure as a liquid.

Compressed gas propellants

In applications in which a large quantity of propellant is used, such as pressure washing and airbrushing, air may be pressurized by a compressor and used immediately. Additionally, a hand pump to compress air can be used for its simplicity in low-tech applications such as atomizers, plant misters and water rockets. The simplest examples of such a system are squeeze bottles for such liquids as ketchup and shampoo.

However, compressed gases are impractical as stored propellants if they do not liquify inside the storage container, because very high pressures are required in order to store any significant quantity of gas, and high-pressure gas cylinders and pressure regulators are expensive and heavy.

Liquified gas propellants

See also: Aerosol_spray § Aerosol_propellants

Principle

Liquified gas propellants are gases at atmospheric pressure, but become liquid at a modest pressure. This pressure is high enough to provide useful propulsion of the payload (e.g. aerosol paint, deodorant, lubricant), but is low enough to be stored in an inexpensive metal can, and to not pose a safety hazard in case the can is ruptured.

The mixture of liquid and gaseous propellant inside the can maintains a constant pressure, called the liquid's vapor pressure. As the payload is depleted, the propellant vaporizes to fill the internal volume of the can. Liquids are typically 500-1000x denser than their corresponding gases at atmospheric pressure; even at the higher pressure inside the can, only a small fraction of its volume needs to be propellant in order to eject the payload and replace it with vapor.

Vaporizing the liquid propellant to gas requires some energy, the enthalpy of vaporization, which cools the system. This is usually insignificant, although it can sometimes be an unwanted effect of heavy usage (as the system cools, the vapor pressure of the propellant drops). However, in the case of a freeze spray, this cooling contributes to the desired effect (although freeze sprays may also contain other components, such as chloroethane, with a lower vapor pressure but higher enthalpy of vaporization than the propellant).

Propellant compounds

Chlorofluorocarbons (CFCs) were once often used as propellants,[18] but since the Montreal Protocol came into force in 1989, they have been replaced in nearly every country due to the negative effects CFCs have on Earth's ozone layer. The most common replacements of CFCs are mixtures of volatile hydrocarbons, typically propane, n-butane and isobutane.[19] Dimethyl ether (DME) and methyl ethyl ether are also used. All these have the disadvantage of being flammable. Nitrous oxide and carbon dioxide are also used as propellants to deliver foodstuffs (for example, whipped cream and cooking spray). Medicinal aerosols such as asthma inhalers use hydrofluoroalkanes (HFA): either HFA 134a (1,1,1,2,-tetrafluoroethane) or HFA 227 (1,1,1,2,3,3,3-heptafluoropropane) or combinations of the two. More recently, liquid Hydrofluoroolefin (HFO) propellants have become more widely adopted in aerosol systems due to their relatively low vapor pressure, low global warming potential (GWP), and nonflammability.

Payloads

The practicality of liquified gas propellants allows for a broad variety of payloads. Aerosol sprays, in which a liquid is ejected as a spray, include paints, lubricants, degreasers, and protective coatings; deodorants and other personal care products; cooking oils. Some liquid payloads are not sprayed due to lower propellant pressure and/or viscous payload, as with whipped cream and shaving cream or shaving gel. Low-power guns, such as BB guns, paintball guns, and airsoft guns, have solid projectile payloads. Uniquely, in the case of a gas duster ("canned air"), the only payload is the velocity of the propellant vapor itself.

Big Bertha (howitzer)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Big_Bertha_(howitzer) 

 

42-centimetre M-Gerät "Big Bertha"
Model of an M-Gerät at the Musée de l'Armée
Type	Siege artillery
Place of origin	German Empire
Service history
In service	1914–1918
Used by	German Empire
Wars	World War I
Production history
Manufacturer	Krupp
Variants	30.5-centimetre Beta-M-Gerät
Specifications
Mass	42,600 kg (93,900 lb)
Length	10 m (33 ft)
Barrel length	5.04 m (16 ft 6 in) L/12
Width	4.7 m (15 ft)
Height	4.5 m (15 ft)
Diameter	42 cm (17 in)
Caliber	420 mm (17 in)
Elevation	+65°
Traverse	360°
Rate of fire	8 shells an hour or 1 shell per 7.5 minutes
Muzzle velocity	400 m/s (1,300 ft/s)
Maximum firing range	9,300 m (30,500 ft)

The 42-centimetre kurze Marinekanone 14 L/12 (short naval cannon), or Minenwerfer-Gerät (M-Gerät), popularly known by the nickname Big Bertha, was a German siege howitzer built by Krupp AG in Essen, Germany and fielded by the Imperial German Army from 1914 to 1918. The M-Gerät had a 42 cm (17 in) calibre barrel, making it one of the largest artillery pieces ever fielded.

The M-Gerät designed in 1911 as an iteration of earlier super-heavy German siege guns intended to break modern fortresses in France and Belgium and entered production in 1912. Test firing began in early 1914 and the gun was estimated to be finished by October 1914. When the First World War broke out, the two M-Gerät guns, still prototypes, were sent to Liège, Belgium, and destroyed Forts Pontisse and Loncin. German soldiers bestowed the gun with the nickname "Big Bertha", which then spread through German newspapers to the Allies, who used it as a nickname for all super-heavy German artillery. The Paris Gun, a railway gun used to bomb Paris in 1918, has historically been confused for the M-Gerät.

Due to losses from faulty ammunition and Allied counter-battery artillery, a smaller-calibre (30.5 cm (12.0 in)) gun called the Beta-M-Gerät was built and fielded from 1916 until the end of the war. It had a longer and heavier barrel that was mated to the M-Gerät's carriage but was found to be less effective than the base gun.

Development and design

The quick advancement of artillery technology beginning in the 1850s provoked an arms race between artillery and military architecture. Rifled artillery could now fire out of range of fortress guns, so military architects began placing forts in rings around cities or in barriers to block approaching armies. These forts were vulnerable to new artillery shells, which could penetrate earth to destroy masonry underground. In response, star forts evolved into polygonal forts, mostly underground and made of concrete with guns mounted in armoured, rotating casemates. Combining rings and barriers, France created a vast fortified zone on its border with Germany, while Belgium began construction of the National Redoubt in 1888.

The German Empire also fortified its borders, but Chief of the General Staff Helmuth von Moltke the Elder desired the ability to break through Franco-Belgian fortifications. Although German artillery had been effective during the Franco-Prussian War, it had been allowed to stagnate. By the 1880s the barrel diameter of the German Army's most powerful gun, the 21 cm (8.3 in) field howitzer, was no longer adequate against fortresses. Moltke began requesting more powerful guns that same decade. More powerful artillery became essential to his successor, Alfred von Schlieffen, who planned quickly to defeat France by sweeping through Belgium (the Schlieffen Plan) in response to the 1893 Franco-Russian Alliance. To be able to reduce French and Belgian fortresses, the Artillerieprüfungskommission [de] (Artillery Test Commission, APK) formed a partnership with Krupp AG in 1893. The first result of this partnership was a 30.5 cm (12.0 in) mortar, accepted into service four years later as the schwerer Küstenmörser L/8, but known as the Beta-Gerät (Beta Apparatus) to disguise its purpose as a siege gun. Tests in the mid-1890s showed that the Beta-Gerät could not destroy French or Belgian forts, even with improved shells. Interest in a more powerful siege gun waned until the Russo-Japanese War, during which the Japanese Army used 28 cm howitzer L/10 (28 cm (11 in) coastal guns) brought from Japan to end the 11-month long Siege of Port Arthur.

The Gamma-Gerät, predecessor of the M-Gerät

In 1906, Helmuth von Moltke the Younger became Chief of the General Staff and instructed the APK to study and improve the performance of the Beta-Gerät. The APK recommended a more powerful gun, with a diameter as large as 45 centimetres (18 in), but the German Army opted for a 30.5-centimetre howitzer, the Beta-Gerät 09 and a 42 cm (17 in) gun. Design and testing for the Gamma-Gerät began in 1906 and lasted until 1911. Although the Gamma-Gerät had the destructive power the General Staff required and could outrange French and Belgian fort guns, it could only be emplaced near rail lines and took 24 hours to prepare. As early as 1907, Krupp began development of siege artillery transported by gun carriage. Testing resulted in a 28 cm (11 in) howitzer transportable over road and countryside but it was rejected by the APK, as was Krupp's 30.5-centimetre model. Finally, in late 1911, Krupp and the APK developed a wheeled 42-centimetre howitzer, the 42-centimetre kurze Marinekanone 14 L/12 or Minenwerfer-Gerät (M-Gerät). The APK ordered its first M-Gerät in July 1912 and another in February 1913. Tests of the gun's mobility began in December 1913 and found that gas-powered tractors were best for pulling it. Test firing, at one point observed by Kaiser Wilhelm II, began in February 1914, and Krupp estimated that the M-Gerät would be complete by October 1914.

Design and production

Assembled and emplaced, the M-Gerät weighed 42.6 t (47.0 tons), was 4.5 m (15 ft) tall, 10 m (33 ft) long and 4.7 m (15 ft) wide, and sat on a steel base with a spade for bracing. This spade could be lifted out of the ground while the M-Gerät was emplaced to move it, giving it a traverse of 360°. The gun was breech loaded, using a horizontally-sliding breech block and had a 5.04 m (16.5 ft) barrel that could be elevated to a maximum of 65°. The M-Gerät had a muzzle velocity of about 815 m/s (2,670 ft/s) and a maximum range of 9,300 m (30,500 ft). Post-prototype M-Gerät guns had a crew platform in front of the blast shield, a detachable breech, and solid wheels. The APK ordered the first M-Gerät in July 1912, delivered the following December, and a second in February 1913. Another two guns were ordered before the First World War on 31 July 1914, and then two more on 28 August and another pair on 11 November. Krupp eventually built 12 M-Gerät howitzers.

The M-Gerät had to be assembled for firing and for transport was dismantled and towed in five wagons. These wagons, weighing 16 to 20 t (16 to 20 long tons; 18 to 22 short tons) each, were designed to hold a specific portion of the M-Gerät, sans the gun carriage, which was its own wagon. These were towed by purpose-built, gas-powered tractors as the wagons were too heavy to be pulled by horses. To move across open country, the wagon wheels were fitted with articulated feet called radgürteln to reduce their ground pressure. Under optimal circumstances, the tractors and wagons could move at 7 km/h (4.3 mph).

The 30.5-centimetre Beta-M-Gerät, called the schwere Kartaune L/30, was developed in late 1917 to replace M-Gerät guns that had been rendered inoperable by premature detonation of shells. To increase the range of the M-Gerät and lower the likelihood of premature detonation, the APK selected a 9 m (30 ft)-long, 16 t (16 long tons; 18 short tons) naval barrel to be mounted onto the chassis of the M-Gerät. Two large spring cylinders were added to the front of the gun to counterbalance the new barrel, which had to be carried in a new carriage weighing 22 t (22 long tons; 24 short tons). Fully assembled, the Beta-M-Gerät weighed 47 t (46 long tons; 52 short tons) and had a maximum range of 20,500 m (67,300 ft). The propellant used to achieve that range caused three of the four Beta-M-Gerät guns to explode, forcing their crews to limit its range by 4,000 m (13,000 ft), defeating the purpose of the longer L/30 barrel. Only four Beta-M-Gerät guns were modified from two M-Gerät guns and two Gamma-Gerät guns (a one- to two-month-long process per gun), but 12 L/30 barrels were built.

"Gerät" siege artillery variants

Name	Calibre	Weight	Range	Rate of fire	Time to emplace (hours)
M-Gerät "Big Bertha"	42 cm (17 in)	42.6 t (41.9 long tons; 47.0 short tons)	9,300 m (30,500 ft)	8 shells an hour	5–6
Gamma-Gerät		150 t (150 long tons; 170 short tons)	14,000 m (46,000 ft)		24
Beta-M-Gerät	30.5 cm (12.0 in)	47 t (46 long tons; 52 short tons)	20,500 m (67,300 ft)		7–8
Beta-Gerät 09		45 t (44 long tons; 50 short tons)	12,000 m (39,000 ft)	12 shells an hour	12
Beta-Gerät		30 t (30 long tons; 33 short tons)	8,200 m (26,900 ft)	15 shells an hour

Ammunition

A 42 cm projectile in 1918

German siege artillery had three types of projectiles: armour-piercing, high-explosive and intermediate. The armour-piercing shell was designed to smash through concrete and metal armour but was largely ineffective against reinforced concrete. High-explosive shells were fitted with two charges and could be set to have no delay, a short delay or a long delay. If set to "no delay" the shell burst on impact. If set to a delayed detonation, it could penetrate up to 12 m (39 ft) of earth. Finally, the intermediate, or "short shell", weighed half as much as the high-explosive shell and was fitted with a ballistic tip for range and accuracy. Shells for the 42-centimetre guns were generally 1.5 m (4 ft 11 in) long, weighed between 400 and 1,160 kg (880 and 2,560 lb), and were propelled via primer loaded into the gun with a brass casing. Siege artillery shells were produced in limited runs of varying quality. Beginning in early 1916, German siege guns began to suffer internal explosions due to faulty ammunition. Crews were required to disembark from the gun before firing via a lanyard.

Service history

The kurze Marinekanone (KMK) batteries that formed with M-Gerät guns were 3 (2 August 1914), 5 (June 1915), 6 (Summer 1915) and 7 (early 1916). Battery 3 was split in half in April 1916 to form 10 with a single M-Gerät each. The four Beta-M-Gerät guns produced were fielded by KMK Batteries 8 and 10 after their M-Gerät gun barrels had been destroyed by premature detonation. When the German Army was reorganised in late 1918, only Battery 5 had M-Gerät guns, and schwere Küstenmörser (SKM) Battery 3 was assigned the remaining two Beta-M-Gerät guns.

Western Front

See also: German invasion of Belgium (1914) and Battle of Verdun

Ruins of the Fort de Loncin, 1914

By June 1914, the prototype M-Gerät howitzers had returned to Essen for final adjustments and would have been formed into a reserve artillery battery on completion in October. On 2 August 1914, they were organised into KMK Battery 3 and sent to the Western Front with 240 men. On 4 August, the 1st Army arrived near Liège, Belgium, the first objective of the Schlieffen Plan and began the Battle of Liège. Although German troops entered the city on 7 August, its forts were firing upon the road to be taken by the 2nd Army and had to be reduced. Heavy artillery began their attack on 8 August. KMK Battery 3 was the first siege battery sent into battle to bombard the Fort de Pontisse on 12 August, which surrendered after two days. The battery next moved to the Fort de Liers but the fort surrendered as the battery was being emplaced. KMK Battery 3 relocated to the Fort de Loncin, where Gérard Leman directed the defence of Liège. Firing commenced on 15 August and lasted two hours, as the 25th shot fired struck a magazine and caused an explosion that destroyed the fort. The Germans carried Leman, unconscious, out of Loncin, and the last two forts, Hollogne and Flémalle, capitulated on 16 August.

With Liège captured, the 1st Army continued north-west while the 2nd and 3rd Armies marched to Namur, whose forts were undermanned, unmaintained, and poorly stocked with ammunition. The 2nd Army arrived on 20 August 1914 to open the Siege of Namur, but began their main attacks the following day with 400 pieces of artillery. KMK Battery 3 fired upon the Fort de Marchovelette, which was destroyed on 23 August by a magazine explosion. The battery shifted its fire to the Fort de Maizeret, already under bombardment by four Austro-Hungarian Skoda 30.5-centimetre guns, and compelled its surrender. With the eastern forts occupied, the Germans entered Namur and the remaining Belgian forces evacuated from the city.

A ruined cupola at one of the Maubeuge forts, 1914

Following the defeat of the Western Allies at Charleroi and at Mons, the British Expeditionary Force withdrew past Maubeuge, their base of operations after arriving in France. On 24 August 1914, the advancing Germans arrived at the fortresses of Maubeuge and began the Siege of Maubeuge and its garrison of 45,000 soldiers. The next day, the VII Reserve Corps were left behind the main German armies to take the city. Bombardment of the forts began on 30 August, with KMK Battery 3 tasked with reducing Ouvrage Les Sarts (Fort Sarts) but it mistakenly shelled an interval fortification in front of Sarts. By 5 September, a hole in the fortress ring had been opened by German 21-centimetre guns, but they had by now exhausted their ammunition. To widen that gap, the siege guns then expended their remaining ammunition against Forts Leveau, Héronfontaine, and Cerfontaine on 7 September, and destroyed them in quick succession. The two remaining French forts surrendered that same day and the Germans occupied Maubeuge on 8 September.

With Maubeuge taken, German siege guns were available for an attack on Paris, but Germany's defeat at the Battle of the Marne blocked the advance of the 1st and 2nd Armies, and the guns were instead sent to Antwerp. King Albert I had ordered a general retreat to Antwerp on 18 August, and his army arrived in the city two days later. From Antwerp, Albert made attacks on the German flank on 24–25 August and 9 September, prompting General Alexander von Kluck of the 1st Army to send the III Reserve Corps to seize Antwerp. It arrived and partially surrounded Antwerp from the south-west on September 27, and bombardment began the next day. KMK Battery 3 arrived on 30 September and opened fire on the Fort de Lier [nl], whose artillery narrowly missed the battery. The fort was abandoned by its garrison on 2 October, allowing KMK Battery 3 to attack and destroy the Fort de Kessel [nl] in a day. The battery then moved to attack the Fort de Broechem [nl], which was also destroyed within two days. From 7 to 9 October, the Belgian army fled from Antwerp and the city surrendered on 10 October.

Early in 1916, all 42-centimetre guns were assigned to the 5th Army, which amassed a total of 24 siege guns, the highest concentration of them during the war. The Battle of Verdun was opened on 21 February 1916 with an intense, nine-hour long artillery bombardment. The 42-centimetre guns had to suppress the artillery of Forts Vaux, Douaumont, Souville and Moulainville [fr] but were unable to penetrate the concrete of the modern fortresses. On the second day of the battle, both of KMK Battery 7's M-Gerät guns were destroyed by premature detonations and KMK Batteries 5 and 6 both lost an M-Gerät each to the same cause. Most of the siege guns at Verdun were moved north in July to participate in the Battle of the Somme, and by September the only M-Gerät units left in Verdun were KMK Batteries 3 and 6.

In the final two years of the war, KMK batteries that suffered losses of their big guns had them replaced with smaller–calibre weapons. Those that remained primarily shelled field works and often had low survivability due to malfunctions or Allied counter-battery artillery. KMK Battery 10 lost one M-Gerät to a premature detonation and the other to British warships near Ostend in August 1917 and was rearmed with captured Russian 12 cm (4.7 in) howitzers. It and KMK Battery 10 were given the four Beta-M-Geräts made during the war in early 1918. For the German spring offensive, KMK Battery 8 was assigned to the 6th Army, Battery 6 to the 2nd Army, and Battery 3 to the 18th Army. The effect of the siege guns was negligible. For Germany's final offensive in July 1918, KMK Batteries 5 and 6 were reassigned to the 7th Army at the Marne, while Batteries 3, 8 and 10 went to the 1st Army at Reims. The batteries again had little to no effect, and Battery 10 became the last German siege battery to fire on a fort, the Fort de la Pompelle. In November 1918, KMK Battery 5 surrendered its guns, the remaining two M-Gerät howitzers, to the American Expeditionary Force.

Eastern Front

Kaunas's Fort II in ruins, 2011

On 2 May 1915, August von Mackensen launched the Gorlice-Tarnow Offensive. By the end of the month, his forces neared Przemyśl, which had been captured by the Russians from Austria-Hungary on 22 March 1915. KMK Battery 6 took part in the bombardment of forts X, Xa, XI and XIa, opened on 30 March. Two days later, the Germans took and held forts X, Xa and XI against counter-attack, compelling the Russians to abandon Przemyśl. German troops entered the city on 3 June, then took the remaining forts two days later. From 8 August, KMK Battery 6 supported the XXXX Reserve Corps in its attack on Kaunas Fortress by bombarding Kaunas's three westernmost forts. Although the German siege artillery's shelling of Kaunas was slow, the fortifications were outdated and were easily destroyed. The city fell on 18 August.

To the south, KMK Batteries 3 and 5 participated in the siege of Novogeorgievsk, which the Germans had surrounded on 10 August. On 13 August, KMK Batteries 3 and 5 attacked with the siege guns from the north, shelling forts XIV, XV and XVI. On 16 August, German infantry stormed forts XV and XVI as the artillery bombarded them. A 42-centimetre shell struck German troops attacking Fort XV, resulting in heavy casualties but the Germans took the forts. The Russians abandoned the outer ring on 18 August, allowing the Germans to open a hole in the inner ring and capture Novogeorgievsk the next day. The Russians abandoned fortresses wholesale during the Great Retreat. At Grodno, KMK Batteries 3, 5, and 6 were not even fully emplaced when the fortress was evacuated on 3 September. The last deployment of M-Gerät guns on the Eastern Front was in October 1915, when KMK Battery 6 was attached to the German 11th Army as it invaded Serbia.

Replicas and legacy

The nickname "Big Bertha" appeared early in the war, when German soldiers named the guns Dicke Berta at the Battle of Liège, a reference to Bertha Krupp, who had inherited the Krupp works from her father. The name spread to German newspapers and then to Allied troops as "Big Bertha" and became slang for all heavy German artillery, but especially the 42-centimetre guns. The name has since entered the public consciousness, for example being applied as a moniker to a line of Callaway golf clubs and a satirical French-language magazine and a bond-buying policy by Mario Draghi, President of the European Central Bank.

Two M-Gerät guns were surrendered to the US Army at Spincourt in November 1918. One was taken to the United States, evaluated and then put on display at the Aberdeen Proving Ground, while the other was left unassembled in its transport configuration. Both were scrapped in 1943 and the early 1950s. World War I veteran Emil Cherubin built a replica of an M-Gerät, which toured Germany and appeared on a few postage stamps. The Paris Gun, a railway gun developed during the war and used to bomb Paris in 1918, has historically been confused with the M-Gerät since World War I.

Paris Gun

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Paris_Gun 

 

Paris Gun
The German Paris Gun, also known as the Kaiser Wilhelm Gun, was the largest gun of World War I. In 1918 the Paris Gun shelled Paris from 120 km (75 mi) away.
Type	Super heavy field gun
Place of origin	German Empire
Service history
Used by	German Empire
Wars	World War I
Production history
Designer	Fritz Rausenberger (de:Fritz Rausenberger)
Manufacturer	Krupp
Specifications
Mass	256 tons
Length	34 m (111 ft 7 in)[1]: 84
Barrel length	21 m (68 ft 11 in)
Caliber	211 mm, later rebored to 238 mm
Breech	horizontal sliding-block
Elevation	55 degrees
Muzzle velocity	1,640 m/s (5,400 ft/s)
Maximum firing range	130 km (81 mi)

Scale model of a Paris Gun on its fixed mounting, Wehrtechnische Studiensammlung Koblenz

The Paris Gun (German: Paris-Geschütz / Pariser Kanone) was the name given to a type of German long-range siege gun, several of which were used to bombard Paris during World War I. They were in service from March to August 1918. When the guns were first employed, Parisians believed they had been bombed by a high-altitude Zeppelin, as the sound of neither an airplane nor a gun could be heard. They were the largest pieces of artillery used during the war by barrel length, and qualify under the (later) formal definition of large-calibre artillery. Also called the "Kaiser Wilhelm Geschütz" ("Kaiser Wilhelm Gun"), they were often confused with Big Bertha, the German howitzer used against Belgian forts in the Battle of Liège in 1914; indeed, the French called them by this name as well. They were also confused with the smaller "Langer Max" (Long Max) cannon, from which they were derived. Although the famous Krupp-family artillery makers produced all these guns, the resemblance ended there.

As military weapons, the Paris Guns were not a great success: the payload was small, the barrel required frequent replacement, and the guns' accuracy was good enough for only city-sized targets. The German objective was to build a psychological weapon to attack the morale of the Parisians, not to destroy the city itself.

Description

A Paris gun turntable mounting, as captured by United States forces near Château-Thierry, 1918 postcard

Due to the weapon's apparent total destruction by the Germans in the face of the final Entente offensives, its capabilities are not known with full certainty. Figures stated for the weapon's size, range, and performance varied widely depending on the source—not even the number of shells fired is certain. In the 1980s a long note on the gun was discovered and published. This was written by Dr. Fritz Rausenberger (in German), the Krupp engineer in charge of the gun's development, shortly before his death in 1926. Thanks to this, the details of the gun's design and capabilities were considerably clarified.

The gun was capable of firing a 106-kilogram (234 lb) shell to a range of 130 kilometres (81 mi) and a maximum altitude of 42.3 km (26.3 mi)—the greatest height reached by a human-made projectile until the first successful V-2 flight test in October 1942. At the start of its 182-second flight, each shell from the Paris Gun reached a speed of 1,640 m/s (5,904 km/h; 5,381 ft/s; 3,669 mph).

The distance was so far that the Coriolis effect—the rotation of the Earth—was substantial enough to affect trajectory calculations. The gun was fired at an azimuth of 232 degrees (southwest) from Crépy-en-Laon, which was at a latitude of 49.5 degrees north.

Seven barrels were constructed. They used worn-out 38 cm SK L/45 "Max" 17,130 millimeter gun barrels that were fitted with an internal tube that reduced the caliber from 380 mm (15 in) to 210 mm (8 in). The tube was 31 metres (102 ft) long and projected 13.9 m (46 ft) out of the end of the gun, so an extension was bolted to the old gun-muzzle to cover and reinforce the lining tube. A further, 6-meter–long smooth-bore extension was attached to the end of this, giving a total barrel length of 37 m (121 ft). This smooth section was intended to improve accuracy and reduce the dispersion of the shells, as it reduced the slight yaw a shell might have immediately after leaving the gun barrel produced by the gun's rifling. The barrel was braced to counteract barrel drop due to its length and weight, and vibrations while firing; it was mounted on a special rail-transportable carriage and fired from a prepared, concrete emplacement with a turntable. The original breech of the old 38 cm gun did not require modification or reinforcement.

The Paris Gun prepared for rail transport.

Since it was based on a naval weapon, the gun was manned by a crew of 80 Imperial Navy sailors under the command of Vice-Admiral Maximilian Rogge, chief of the Ordnance branch of the Admiralty. It was surrounded by several batteries of standard army artillery to create a "noise-screen" chorus around the big gun so that it could not be located by French and British spotters.

The projectile flew significantly higher than projectiles from previous guns. Writer and journalist Adam Hochschild put it this way: "It took about three minutes for each giant shell to cover the distance to the city, climbing to an altitude of 25 miles [40 km] at the top of its trajectory. This was by far the highest point ever reached by a man-made object, so high that gunners, in calculating where the shells would land, had to take into account the rotation of the Earth. For the first time in warfare, deadly projectiles rained down on civilians from the stratosphere". This reduced drag from air resistance, allowing the shell to achieve a range of over 130 kilometres (81 mi).

The unfinished V-3 cannon would have been able to fire larger projectiles to a longer range, and with a substantially higher rate of fire. The unfinished Iraqi super gun would also have been substantially bigger.

Projectiles

Diagram of a Paris gun shell published in 1921

The damage caused by a shell landing on the Père Lachaise Cemetery on the 25 March 1918

The Paris Gun shells weighed 106 kg (234 lb). The shells initially used had a diameter of 216 mm (8.5 in) and a length of 960 mm (38 in). The main body of the shell was composed of thick steel, containing 7 kg (15 lb) of TNT.

The small amount of explosive – around 6.6% of the weight of the shell – meant that the effect of its shellburst was small for the shell's size. The thickness of the shell casing, to withstand the forces of firing, meant that shells would explode into a comparatively small number of large fragments, limiting their destructive effect. A crater produced by a shell falling in the Tuileries Garden was described by an eyewitness as being 10 to 12 ft (3.0 to 3.7 m) across and 4 ft (1.2 m) deep.

The shells were propelled at such a high velocity that each successive shot wore away a considerable amount of steel from the rifled bore. Each shell was sequentially numbered according to its increasing diameter, and had to be fired in numeric order, lest the projectile lodge in the bore and the gun explode. Also, when the shell was rammed into the gun, the chamber was precisely measured to determine the difference in its length: a few inches off would cause a great variance in the velocity, and with it, the range. Then, with the variance determined, the additional quantity of propellant was calculated, and its measure taken from a special car and added to the regular charge. After 65 rounds had been fired, each of progressively larger caliber to allow for wear, the barrel was sent back to Krupp and rebored with a new set of shells.

The shell's explosive was contained in two compartments, separated by a wall. This strengthened the shell and supported the explosive charge under the acceleration of firing. One of the shell's two fuzes was mounted in the wall, with the other in the base of the shell. The fuzes proved very reliable as every single one of the 303 shells that landed in and around Paris successfully detonated.

The shell's nose was fitted with a streamlined, lightweight, ballistic cap and the side had grooves that engaged with the rifling of the gun barrel, spinning the shell as it was fired so its flight was stable. Two copper driving bands provided a gas-tight seal against the gun barrel during firing.

Use in World War I

Map of central districts of Paris, showing where shells fired by the Paris Gun landed, June-August 1918, and a line indicating the direction of the German guns. (Some shells landed outside this area.) Based on Miller (1921), pg. 735

The damage to St-Gervais-et-St-Protais Church (1918)

The Paris gun was used to shell Paris at a range of 120 km (75 mi). The gun was fired from a wooded hill (Le mont de Joie) near Crépy, and the first shell landed at 7:18 a.m. on 23 March 1918 on the Quai de la Seine, the explosion being heard across the city. Shells continued to land at 15-minute intervals, with 21 counted on the first day. On the first day, fifteen people were killed and thirty-six wounded. The effect on morale in Paris was immediate: by 27 March, queues of thousands had started at the Gare d'Orsay and, at the Gare Montparnasse, ticket sales out of the capital were suspended due to demand.

The initial assumption was these were bombs dropped from an airplane or Zeppelin flying too high to be seen or heard. Within a few hours, sufficient casing fragments had been collected to show that the explosions were the result of shells, not bombs. By the end of the day, military authorities were aware the shells were being fired from behind German lines by a new long-range gun, although there was initial press speculation on the origin of the shells. This included the theory they were being fired by German agents close by Paris, or even within the city itself, so abandoned quarries close to the city were searched for a hidden gun. Three emplacements for the gun were located within days by the French reconnaissance pilot Didier Daurat, the path of the shells which landed in Paris having revealed the direction from which they were being fired. The closest emplacement was engaged by a 34 cm railway gun while the other two sites were bombed by aircraft, although this failed to interrupt the German bombardment.

Between 320 and 367 shells were fired, at a maximum rate of around 20 per day. The shells killed 250 people and wounded 620, and caused considerable damage to property. The worst incident was on 29 March 1918, when a shell hit the roof of the St-Gervais-et-St-Protais Church, collapsing the roof onto the congregation then hearing the Good Friday service. A total of 91 people were killed and 68 were wounded. There was no firing between 25 and 29 March, when the first barrel was being replaced; an unconfirmed intelligence report claimed that it had exploded. Barrels were probably changed again between 7-11 April and again between 21-24 April. The diameter of the later shells increased from 21 to 24 cm, indicating that the used barrels had been re-bored.

A further emplacement, later identified as specifically designed for the Paris Gun, was found by advancing US troops at the beginning of August, on the north side of the wooded hill at Coucy-le-Château-Auffrique, some 86 kilometres (53 mi) from Paris.

The gun was taken back to Germany in August 1918 as Allied advances threatened its security. No guns were ever captured by the Allies. It is believed that near the end of the war they were completely destroyed by the Germans. One spare mounting was captured by American troops in Bruyères-sur-Fère, near Château-Thierry, but the gun was never found; the construction plans seem to have been destroyed as well.

After World War I

A K 12 railway gun elevated to the firing position

Under the terms of the Treaty of Versailles, the Germans were required to turn over a complete Paris Gun to the Allies, but they never complied with this.

In the 1930s, the German Army became interested in rockets for long-range artillery as a replacement for the Paris Gun—which was specifically banned under the Versailles Treaty. This work eventually led to the V-2 rocket that was used in World War II.

Despite the ban, Krupp continued theoretical work on long-range guns. They started experimental work after the Nazi government began funding the project upon coming to power in 1933. This research led to the 21 cm K 12 (E), a refinement of the Paris Gun design concept. Although it was broadly similar in size and range to its predecessor, Krupp's engineers had significantly reduced the problem of barrel wear. They also improved mobility over the fixed Paris Gun by making the K 12 a railway gun.

The first K 12 was delivered to the German Army in 1939 and a second in 1940. During World War II, they were deployed in the Nord-Pas-de-Calais region of France; they were used to shell Kent in Southern England between late 1940 and early 1941. One gun was captured by Allied forces in the Netherlands in 1945.

In popular culture

"Big Bertha" in the Charlie Chaplin film The Great Dictator.

A parody of the Paris Gun appears in the Charlie Chaplin movie The Great Dictator. Firing at the Cathedral of Notre Dame, the "Tomanians" (the fictional country that represented Germany) succeed in blowing up a small outhouse.

The destruction of the St-Gervais-et-St-Protais Church inspired Romain Rolland to write his novel Pierre et Luce.