V-3 Cannon

The V-3 (german: Vergeltungswaffe 3, ("Vengeance Weapon 3") was a German World War II large-caliber gun working on the multi-charge principle whereby secondary propellant charges are fired to add velocity to a projectile.

The Germans planned to use the weapon to bombard London from two large bunkers in the Pas-de-Calais region of northern France, but they were rendered unusable by Allied bombing raids before completion. Two similar guns were used to bombard Luxembourg from December 1944 to February 1945.

The V-3 was also known as the ''Hochdruckpumpe'' ("High Pressure Pump," HDP for short), which was a code name intended to hide the real purpose of the project. It was also known as ''Fleißiges Lieschen'' ("Busy Lizzie"). (bottom of page)

Description

The gun used multiple propellant stages placed along the barrel's length in order to provide an additional boost. These were ignited by the hot gases that propelled the projectile as it passed them. Solid-fuel rocket boosters were used instead of explosive charges because of their greater suitability and ease of use. These were arranged in symmetrical pairs along the length of the barrel, angled to project their thrust against the base of the projectile as it passed. This layout spawned the German codename ''Tausendfüßler'' ("millipede").

The barrel and side chambers were designed as identical sections to simplify production and allow damaged sections to be replaced. The entire gun would use multiple such sections bolted together. The smoothbore gun fired a fin-stabilized shell that depended upon aerodynamic forces rather than gyroscopic forces to prevent tumbling (as distinct from conventional rifled weapons which cause the projectile to spin).

Background

The basic idea of the multi-charge concept is that in a traditional single-charge gun the pressure in the barrel is at its peak when the charge is fired, and then continually dwindles to some much lower value as the shell travels down the barrel and the combustion gasses expand. This requires a traditional gun to be much heavier at the breech end in order to successfully contain this pressure, and as the gun grows in power, the weight becomes untenable. The multi-charge concept uses a low-power initial charge and continues adding more charges as the shell moves along the barrel, resulting in a much more constant pressure as the shell moves. This reduces peak pressure and the need to have a heavy breech, as well as providing smoother acceleration.

The origin of the multi-chamber gun dates back to the 19th century. In 1857, U.S. inventor Azel Storrs Lyman (1815–1885) was granted a patent on ''"Improvement in accelerating fire-arms"'', and he built a prototype in 1860 which proved to be unsuccessful. Lyman then modified the design in collaboration with James Richard Haskell, who had been working for years on the same principle.

Haskell and Lyman reasoned that subsidiary propellant charges could increase the muzzle velocity of a projectile if the charges were spaced at intervals along the barrel of a gun in side chambers and ignited an instant after a shell had passed them. The "Lyman-Haskell multi-charge gun" was constructed on the instructions of the U.S. Army's Chief of Ordnance, but it did not resemble a conventional artillery piece. The barrel was so long that it had to be placed on an inclined ramp, and it had pairs of chambers angled back at 45 degrees discharging into it.

It was test fired at the Frankford Arsenal at Philadelphia in 1880 and was unsuccessful. The flash from the original propellant charge bypassed the projectile due to faulty obturation and prematurely ignited the subsidiary charges before the shell passed them, slowing the shell down. The best velocity that could be obtained from it was , inferior to the performance of a conventional RBL 7 inch Armstrong gun of the same period. New prototypes of multi-charge guns were built and tested, but Lyman and Haskell abandoned the idea.

During the same period, French engineer Louis-Guillaume Perreaux, one of the pioneers of the motorcycle, had been working on a similar project since before 1860. Perreaux was granted a patent in 1864 for a multi-chamber gun. In 1878, Perreaux presented his invention at the World Exhibition of Paris.

Development

In 1918, the French Army made plans for a very long range multi-chamber gun in response to the German Paris Gun. The Paris Gun was built by Friedrich Krupp AG and could bombard Paris from German lines over a distance of no less than . The French initiative did not reach the prototype stage, as it was discontinued when the retreat of the German armies and the armistice put an end to the bombardment. The plans for the multi-chamber gun were archived, as they had been envisioned to counter the German fire.

France collapsed in June 1940 at the beginning of World War II, and German troops acquired the plans of this long-range gun. In 1942, this patent attracted the attention of August Cönders,August Cönders is often incorrectly considered the inventor of the multi-chamber gun. developer of the Röchling shell and chief engineer of the plants "Röchling Stahlwerk AG" in Wetzlar, Germany. Cönders thought that the gradual acceleration of the shell by a series of small charges spread over the length of the barrel might be the solution to the problem of designing very long range guns. The very strong explosive charge needed to project shells at a high speed was causing very rapid degradation of the gun tubes of conventional guns.For example, in 1918, the tube of the Paris Gun needed to be changed after only 65 shots. Moreover, the shells had to be made in progressively larger diameter to compensate for wear of the tube, and were numbered from 1 to 65 to be used in the correct order. ()

Cönders proposed the use of electrically activated charges to eliminate the problem of the premature ignition of the subsidiary charges, the problem experienced by the Lyman-Haskell gun. Cönders built a prototype of a 20 mm multi-chamber gun using machinery readily available at the Wetzlar plant, machinery that was producing tubes of this calibre for the Flak 38 anti-aircraft guns of 20 mm. The first tests were encouraging, but to get the support of the Ministry of arms, Hermann Röchling had to present to Albert Speer Cönders' project of a cannon capable of firing on London from the coast of the Pas-de-Calais. The project intended to use two batteries to crush London under a barrage of hundreds of shells per hour, shells of with an explosive charge of .

Speer told Adolf Hitler about the proposal in May 1943. After the Royal Air Force (RAF) bombed the Peenemünde rocket center on 17 August, Hitler agreed to Speer's suggestion that the gun be built without more tests. Cönders constructed a full-calibre gun at the Hillersleben proving ground near Magdeburg but, by the end of 1943, he had encountered severe problems both in putting the gun's basic principle into operation and in producing a feasible design for the shells that it was to fire. Even when everything worked, the muzzle velocity was just over , which was nowhere near what had been promised. Nonetheless, a proposal was made to build a single full-sized gun with a barrel at Misdroy on the Baltic island of Wolin, near Peenemünde, while construction went ahead at the Mimoyecques site in France (which had already been attacked by the USAAF and the RAF). The ''Heereswaffenamt'' (Weapon Procurement Office) took control of the project by March 1944, and, with no good news from Misdroy, Cönders became one of the engineers working on the three chief problems: projectile design, obturation, and ignition of the secondary charges.

Six different companies produced satisfactory designs for projectiles, including Krupp and Škoda Works. Obturation problems were solved by placing a sealing piston between the projectile and the initial propellant charge, which in turn prevented the flash from the charge from getting ahead of the projectile and solved the problem of controlling the initiation of the secondary charges. By the end of May 1944, there were four designs for the 150 mm finned projectile, one manufactured by Fasterstoff (designed by Füstenberg) and three others by Röchling (Cönders), Bochumer (Verein-Haack), and Witkowitz Ironworks (Athem).

Trials were held at Misdroy from 20–24 May 1944 with ranges of up to being attained. On 4 July 1944, the Misdroy gun was test-fired with 8 rounds (one of the long shells travelled ). The gun burst during the testing, putting an end to the tests.

Mimoyecques site

Major Bock of Festung Pioneer-Stab 27 (the fortification regiment of LVII Corps, Fifteenth Army, at the time based in the Dieppe area) was given the task of finding a suitable site for the HDP batteries following Hitler's decision that HDP guns should be sited in northern France to bombard London. A study in early 1943 concluded that a hill with a rock core would be most suitable, as the gun tubes could be placed in drifts (inclined tunnels) and support equipment and supplies located in adjacent tunnels. The guns would not be movable and would be permanently aimed at London.

A suitable site was selected at a limestone hill about north of the Hidrequent quarries, near Mimoyecques in the Pas-de-Calais region of northern France behind Cap Gris Nez, very close to the French end of the present day Channel tunnel, where V-1 and V-2 launch sites were already under construction. The site was from the sea and from London. It was code-named ''Wiese'' (meadow) and ''Bauvorhaben 711'' (Construction Project 711), and Organisation Todt began construction in September 1943 with the building of railway lines to support the work, and began to excavate the gun shafts in October. The initial layout comprised two parallel facilities approximately apart, each with five drifts which were to hold a stacked cluster of five HDP gun tubes, for a total of 50 guns. Both facilities were served by an underground railway tunnel and underground ammunition storage galleries.

The eastern complex consisted of five drifts angled at 50 degrees reaching below the hilltop. The five drifts exited the hilltop through a concrete slab wide and thick. Large steel plates protected the five openings and each drift had a special armoured door. Extensive tunnels and elevator shafts supported the guns and, if the site had become operational, about 1,000 troops from Artillerie Abteilung 705 and supporting units would have been deployed at Mimoyecques. Artillerie Abteilung 705 had been organised in January 1944 under Oberstleutnant Georg Borttscheller to operate the Wiese gun complex.

The plans were to have the first battery of five gun tubes ready for March 1944, and the full complex of 25 gun tubes by 1 October 1944. A failure occurred at the Misdroy proving ground in April 1944 after only 25 rounds had been fired and, as a result, the project was further cut back from five drifts to three, even though work had begun on some of the other drifts.

The site was finally put out of commission on 6 July 1944, when bombers of RAF Bomber Command's 617 Squadron (the famous "Dambusters") attacked using " Tallboy" deep-penetration bombs.

Luxembourg bombardment

The project eventually came under the control of the SS, and SS General Hans Kammler ordered it to be ready for action in late 1944, assisted by Walter Dornberger. A battery was constructed of two shorter or 'half-barrel' V-3 guns approximately long with 12 side-chambers, and it was placed in the hands of the army artillery unit ''Artillerie Abteilung 705'' under the command of Hauptmann (Captain) Patzig. These were sited in a wooded ravine

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