French cruiser Pluton
Encyclopedia
The Pluton was a fast minelaying cruiser
built for the French Navy
in the late 1920s. She was also able to carry 1,000 troops on her mine deck as a fast troop transport. Shortly after completion she was modified and became a gunnery training ship, replacing the elderly armored cruiser
. Shortly before the beginning of World War II
, she reverted to her original role and most of the gunnery training equipment was removed. She was sent to Casablanca
, in French Morocco, when the war began to lay a minefield, but the order was cancelled a day later and she was ordered to disembark her naval mine
s. She exploded while landing her still-fuzed mines on 13 September 1939.
of 15.5 metre and a draft
of 5.2 metre. Her longitudinally-framed hull was subdivided by 15 transverse watertight bulkhead
s. Duralumin
was extensively used in the superstructure to save weight, but this resulted in corrosion problems and strength issues. She was fitted with a single counter-balanced rudder powered by an electric motor that was too weak for the job. Her turning circle was 875 m (956.9 yd) with 25° of rudder at 27 kn (52.9 km/h; 32.9 mph), larger than that of the 8000 t (7,873.6 LT) light cruiser which was 30 metre longer. She was totally unarmored and relied upon her watertight subdivision for survival.
s and provide drinking water. Each propeller shaft drove a three-bladed 4.08 metre bronze three-bladed propeller for a designed speed of 30 kn (58.8 km/h; 36.5 mph), but she achieved 31.4 kn (61.5 km/h; 38.2 mph) on trials. 1150 t (1,131.8 LT) of fuel oil
was carried which was originally calculated to provide an endurance of 7770 nmi (14,390 km; 8,941.6 mi) at 14 kn (27.4 km/h; 17 mph), but it was revised downwards to 4510 nmi (8,352.5 km; 5,190 mi) once she entered service because the demands of her auxiliary machinery had been seriously underestimated. Two 200-kilowatt turbo generator
s provided electricity at 235 volts. Two 100-kilowatt diesel generator
s were mounted in the aft engine room to provide power while in harbor and a third was installed in a special compartment on the first deck for emergency use.
(AA) guns and four light 37 mm (1.46 in) AA guns. However four 138 mm (5.4 in) guns were substituted for the 203 mm guns before construction began and six more 37 mm guns were added in lieu of the 75 mm guns during construction although the baseplates for the 75 mm guns were retained for future use.
The four 138 mm 40-caliber
guns were on M1924 mounts with gun shield
s. Two guns each were fore and aft in superfiring
positions on the centerline. Their elevation limits were -10° to +35° and they had a 270° arc of fire. Their rate of fire was a nominal eight to nine rounds per minute, but proved to be considerably less in service. They had a maximum range of about 18200 m (19,903.8 yd) with a 40 kg (88.2 lb) shell at a muzzle velocity of 700 m/s (2,296.6 ft/s). 150 rounds were provided for each gun. One powder and one shell magazine served each pair of guns, each of which had their own individual hoist.
Ten 37 mm/50 cal semi-automatic AA guns were carried by Pluton. Two were fitted on the foredeck, six amidships between the funnels and two on a platform at the stern. 10,000 rounds were carried with 144 rounds in ready-use boxes near each gun. The guns could depress 15° and elevate to 80°. They fired 0.725 kg (1.6 lb) shells at a muzzle velocity of 810 m/s (2,657 ft/s). Their effective anti-aircraft range was less than 5000 metres (16,404 ft). All of these guns—except for the pair on the stern—were removed shortly after Pluton was commissioned in 1932.
Twelve obsolete 8 mm (0.31496062992126 in) Hotchkiss M1914
machine gun
s were carried in six twin mounts. Two mounts were on top of the bridge, two atop the after boiler room ventilator housing and two just forward of the tripod mainmast. 48,000 rounds were provided for them. They were removed shortly after Pluton was commissioned in 1932.
Pluton was designed to carry 220 1500 kg (3,306.9 lb) Sautter-Harlé mines, but had space for 30 extra, for a total of 250. They were carried on the first deck, or mine deck, using a system of four rails along the sides of the ship and moved via chain-drives. Each pair of rails converged on a turntable at the forward end of the rails and a transverse spur connected the two turntables. The spur facilitated loading mines from one side of the ship and allowed mines to be moved to each of the rails. The rails ended in four ramps at the stern of the ship that sloped down at a 30° angle to minimize the shock of impact when the mines were released from the chain drive. Up to 270 of the smaller Bréguet B4 mines could be carried.
Dockyard for the necessary modifications on 24 October 1932. Quarters for 40 men were added on the mine deck. Most of the 37-mm AA guns and all of the 8 mm machine guns were replaced by four 50-caliber 75 mm Canon de 75 mm Mle 22 or 24 AA guns and 12 13.2 mm (0.519685039370079 in) Hotchkiss mahine gun
s on six twin mounts, two mounts where the 37 mm guns had been mounted on the foredeck and four between the funnels. The 75 mm guns had a maximum depression of 10° and a maximum elevation of 90°. They fired a 5.93 kilograms (13.1 lb) shell at a muzzle velocity of 850 m/s (2,788.7 ft/s) at a rate of fire of 8–18 rounds per minute and had a maximum effective ceiling of 8000 m (26,246.7 ft). The Hotchkiss guns had a cyclic rate of fire of 450 rounds per minute, but the practical rate was between 200 and 250 rounds per minute to allow for reloading its 30-round magazines. They had a theoretical ceiling of 4200 m (13,779.5 ft). A simple fire-control director was added for the 138 mm guns and 15 additional rangefinders were installed for use by the Rangefinding School.
Pluton spend much of 1933-1935 in dockyard hands after finishing her first round of modifications on 27 April 1933. She was refitted four times during this period to add more gunnery equipment and to rectify some of her defects. These included reinforcement of her superstructure where it had been damaged by the muzzle blast
from her 138 mm guns and replacement of her corroded aluminum ladders and booms with steel ones. A high-angle fire-control director for her 75 mm guns was added, two of her 75 mm gun were converted to powered, remotely-controlled mounts, gun shields were added to the 75 mm guns to protect their crews from blast and facilities for another 40 men was installed on her mine deck.
In 1936, an experimental twin 13.2 mm gun mount with a gun shield was added between the starboard 75-mm guns and more rangefinders were added to bring her total up to 31. Her boilers and condensers were repaired in a refit between 25 November 1936 and 13 March 1937. Later that year Pluton had a major refit that involved repair of her turbines, replacement of her 138 mm fire-control director by one of the type used by the 8000 t (7,873.6 LT) light cruisers and the transfer of the foredeck 13.2 mm machine guns to positions on the forward superstrucut. Her last refit, from 15 November 1938-15 February 1939, retubed two boilers, enclosed the AA director to protect it from the weather, improved the remote control of the 138 mm guns and added gun shields to each of the twin 13.2 mm mounts.
Pluton was transferred to Lorient
on 10 May 1939 when the French Navy formed the 5e Escadre there which controlled all training ships and planned to convert her into a full-time training ship as consort to the training cruiser on 1 June 1940. She would have been renamed La Tour d'Auvergne at that time, as the name Pluton was reserved for mine warfare ships in the French Navy.
As war approached, it was decided to retain her as a minelayer and most of the extra fire control equipment was removed. She was transferred to Brest
as part of the reorganization of the 5e Escadre. She sailed for Casablanca, French Morocco on 2 September with 125 Bréguet mines embarked. She was ordered to lay a defensive minefield there on 4 September, but this order was rescinded the next day, after the mines had already been fuzed, and the ship was ordered to disembark the mines. While landing the mines on 13 September one of them exploded, destroying the ship and killing 186 people. A further 73 crewmen and 47 others were injured and significant damage was caused by flying debris. One gun and some armor was salvaged during the war, but demolition work did not begin until October 1952 and was completed by July 1953.
Minelayer
Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...
built for the French Navy
French Navy
The French Navy, officially the Marine nationale and often called La Royale is the maritime arm of the French military. It includes a full range of fighting vessels, from patrol boats to a nuclear powered aircraft carrier and 10 nuclear-powered submarines, four of which are capable of launching...
in the late 1920s. She was also able to carry 1,000 troops on her mine deck as a fast troop transport. Shortly after completion she was modified and became a gunnery training ship, replacing the elderly armored cruiser
Armored cruiser
The armored cruiser was a type of warship of the late 19th and early 20th centuries. Like other types of cruiser, the armored cruiser was a long-range, independent warship, capable of defeating any ship apart from a battleship, and fast enough to outrun any battleships it encountered.The first...
. Shortly before the beginning of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, she reverted to her original role and most of the gunnery training equipment was removed. She was sent to Casablanca
Casablanca
Casablanca is a city in western Morocco, located on the Atlantic Ocean. It is the capital of the Grand Casablanca region.Casablanca is Morocco's largest city as well as its chief port. It is also the biggest city in the Maghreb. The 2004 census recorded a population of 2,949,805 in the prefecture...
, in French Morocco, when the war began to lay a minefield, but the order was cancelled a day later and she was ordered to disembark her naval mine
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...
s. She exploded while landing her still-fuzed mines on 13 September 1939.
Design
The Marine Nationale decided to build a fast minelayer as part of its 1925 Naval Programme after the British made her debut in the early 1920s. Pluton was similar in many respects, also being armed with four single destroyer-caliber guns, but was smaller and faster. She could also be used as a fast transport for up to 1,000 troops. The sides of the mine deck were normally open to the weather, but metal panels could be used to close it off when carrying troops.General characteristics
Pluton was 152.5 metre long overall. She had a beamBeam (nautical)
The beam of a ship is its width at the widest point. Generally speaking, the wider the beam of a ship , the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position...
of 15.5 metre and a draft
Draft (hull)
The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...
of 5.2 metre. Her longitudinally-framed hull was subdivided by 15 transverse watertight bulkhead
Bulkhead (partition)
A bulkhead is an upright wall within the hull of a ship or within the fuselage of an airplane. Other kinds of partition elements within a ship are decks and deckheads.-Etymology:...
s. Duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...
was extensively used in the superstructure to save weight, but this resulted in corrosion problems and strength issues. She was fitted with a single counter-balanced rudder powered by an electric motor that was too weak for the job. Her turning circle was 875 m (956.9 yd) with 25° of rudder at 27 kn (52.9 km/h; 32.9 mph), larger than that of the 8000 t (7,873.6 LT) light cruiser which was 30 metre longer. She was totally unarmored and relied upon her watertight subdivision for survival.
Propulsion
Pluton had a two-shaft unit machinery layout with alternating boiler and engine rooms. Her Bréguet single-reduction impulse geared steam turbines were designed for 57000 shp, but made 64705 shp on trials. Four small-tube boilers powered the turbines at a pressure of 20 kg/cm2. An auxiliary boiler was fitted to heat or cool the ship's magazineMagazine (artillery)
Magazine is the name for an item or place within which ammunition is stored. It is taken from the Arabic word "makahazin" meaning "warehouse".-Ammunition storage areas:...
s and provide drinking water. Each propeller shaft drove a three-bladed 4.08 metre bronze three-bladed propeller for a designed speed of 30 kn (58.8 km/h; 36.5 mph), but she achieved 31.4 kn (61.5 km/h; 38.2 mph) on trials. 1150 t (1,131.8 LT) of fuel oil
Fuel oil
Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power, except oils having a flash...
was carried which was originally calculated to provide an endurance of 7770 nmi (14,390 km; 8,941.6 mi) at 14 kn (27.4 km/h; 17 mph), but it was revised downwards to 4510 nmi (8,352.5 km; 5,190 mi) once she entered service because the demands of her auxiliary machinery had been seriously underestimated. Two 200-kilowatt turbo generator
Turbo generator
A turbo generator is a turbine directly connected to an electric generator for the generation of electric power. Large steam powered turbo generators provide the majority of the world's electricity and are also used by steam powered turbo-electric ships.Smaller turbo-generators with gas turbines...
s provided electricity at 235 volts. Two 100-kilowatt diesel generator
Diesel generator
A diesel generator is the combination of a diesel engine with an electrical generator to generate electrical energy....
s were mounted in the aft engine room to provide power while in harbor and a third was installed in a special compartment on the first deck for emergency use.
Armament
Pluton was originally intended to carry two single turrets, one each fore and aft, with 203 mm (8 in) guns, four 75 mm (2.95 in) anti-aircraftAnti-aircraft warfare
NATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...
(AA) guns and four light 37 mm (1.46 in) AA guns. However four 138 mm (5.4 in) guns were substituted for the 203 mm guns before construction began and six more 37 mm guns were added in lieu of the 75 mm guns during construction although the baseplates for the 75 mm guns were retained for future use.
The four 138 mm 40-caliber
Caliber (artillery)
In artillery, caliber or calibredifference in British English and American English spelling is the internal diameter of a gun barrel, or by extension a relative measure of the length....
guns were on M1924 mounts with gun shield
Gun shield
thumb|A [[United States Marine Corps|U.S. Marine]] manning an [[M240 machine gun]] equipped with a gun shieldA gun shield is a flat piece or section of armor designed to be mounted on a crew-served weapon such as a machine gun or artillery piece, or, more rarely, to be used with an assault rifle...
s. Two guns each were fore and aft in superfiring
Superfire
The idea of superfire is to locate two turrets in a row, one behind the other, but with the second turret located above the one in front so that the second turret could fire over the first...
positions on the centerline. Their elevation limits were -10° to +35° and they had a 270° arc of fire. Their rate of fire was a nominal eight to nine rounds per minute, but proved to be considerably less in service. They had a maximum range of about 18200 m (19,903.8 yd) with a 40 kg (88.2 lb) shell at a muzzle velocity of 700 m/s (2,296.6 ft/s). 150 rounds were provided for each gun. One powder and one shell magazine served each pair of guns, each of which had their own individual hoist.
Ten 37 mm/50 cal semi-automatic AA guns were carried by Pluton. Two were fitted on the foredeck, six amidships between the funnels and two on a platform at the stern. 10,000 rounds were carried with 144 rounds in ready-use boxes near each gun. The guns could depress 15° and elevate to 80°. They fired 0.725 kg (1.6 lb) shells at a muzzle velocity of 810 m/s (2,657 ft/s). Their effective anti-aircraft range was less than 5000 metres (16,404 ft). All of these guns—except for the pair on the stern—were removed shortly after Pluton was commissioned in 1932.
Twelve obsolete 8 mm (0.31496062992126 in) Hotchkiss M1914
Hotchkiss M1914 machine gun
The Mle 1914 Hotchkiss machine gun became the standard machine gun of the French Army during World War I. It was manufactured by the French arms company Hotchkiss et Cie, which had been established in the 1860s by American industrialist Benjamin B. Hotchkiss...
machine gun
Machine gun
A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....
s were carried in six twin mounts. Two mounts were on top of the bridge, two atop the after boiler room ventilator housing and two just forward of the tripod mainmast. 48,000 rounds were provided for them. They were removed shortly after Pluton was commissioned in 1932.
Pluton was designed to carry 220 1500 kg (3,306.9 lb) Sautter-Harlé mines, but had space for 30 extra, for a total of 250. They were carried on the first deck, or mine deck, using a system of four rails along the sides of the ship and moved via chain-drives. Each pair of rails converged on a turntable at the forward end of the rails and a transverse spur connected the two turntables. The spur facilitated loading mines from one side of the ship and allowed mines to be moved to each of the rails. The rails ended in four ramps at the stern of the ship that sloped down at a 30° angle to minimize the shock of impact when the mines were released from the chain drive. Up to 270 of the smaller Bréguet B4 mines could be carried.
Service
She entered service with the French Mediterranean Fleet in 1932. Pluton experienced many teething problems, particularly with the machinery. Shortly after she was commissioned the Navy decided to give her an extra role as a gunnery training ship and she entered ToulonToulon
Toulon is a town in southern France and a large military harbor on the Mediterranean coast, with a major French naval base. Located in the Provence-Alpes-Côte-d'Azur region, Toulon is the capital of the Var department in the former province of Provence....
Dockyard for the necessary modifications on 24 October 1932. Quarters for 40 men were added on the mine deck. Most of the 37-mm AA guns and all of the 8 mm machine guns were replaced by four 50-caliber 75 mm Canon de 75 mm Mle 22 or 24 AA guns and 12 13.2 mm (0.519685039370079 in) Hotchkiss mahine gun
13.2 mm Hotchkiss machine gun
The 13.2 mm Hotchkiss machine gun was a heavy machine gun designed and manufactured by Hotchkiss et Cie from the late 1920s until World War II where it saw service with various nation's forces, including Japan where the gun was built under licence....
s on six twin mounts, two mounts where the 37 mm guns had been mounted on the foredeck and four between the funnels. The 75 mm guns had a maximum depression of 10° and a maximum elevation of 90°. They fired a 5.93 kilograms (13.1 lb) shell at a muzzle velocity of 850 m/s (2,788.7 ft/s) at a rate of fire of 8–18 rounds per minute and had a maximum effective ceiling of 8000 m (26,246.7 ft). The Hotchkiss guns had a cyclic rate of fire of 450 rounds per minute, but the practical rate was between 200 and 250 rounds per minute to allow for reloading its 30-round magazines. They had a theoretical ceiling of 4200 m (13,779.5 ft). A simple fire-control director was added for the 138 mm guns and 15 additional rangefinders were installed for use by the Rangefinding School.
Pluton spend much of 1933-1935 in dockyard hands after finishing her first round of modifications on 27 April 1933. She was refitted four times during this period to add more gunnery equipment and to rectify some of her defects. These included reinforcement of her superstructure where it had been damaged by the muzzle blast
Muzzle flash
Muzzle blast is the term used to describe the release of high temperature, high pressure gases expelled from the muzzle of a firearm when it is discharged. Muzzle flash is the term used to describe the visible light of the muzzle blast. The blast and flash are caused by the combustion products of...
from her 138 mm guns and replacement of her corroded aluminum ladders and booms with steel ones. A high-angle fire-control director for her 75 mm guns was added, two of her 75 mm gun were converted to powered, remotely-controlled mounts, gun shields were added to the 75 mm guns to protect their crews from blast and facilities for another 40 men was installed on her mine deck.
In 1936, an experimental twin 13.2 mm gun mount with a gun shield was added between the starboard 75-mm guns and more rangefinders were added to bring her total up to 31. Her boilers and condensers were repaired in a refit between 25 November 1936 and 13 March 1937. Later that year Pluton had a major refit that involved repair of her turbines, replacement of her 138 mm fire-control director by one of the type used by the 8000 t (7,873.6 LT) light cruisers and the transfer of the foredeck 13.2 mm machine guns to positions on the forward superstrucut. Her last refit, from 15 November 1938-15 February 1939, retubed two boilers, enclosed the AA director to protect it from the weather, improved the remote control of the 138 mm guns and added gun shields to each of the twin 13.2 mm mounts.
Pluton was transferred to Lorient
Lorient
Lorient, or L'Orient, is a commune and a seaport in the Morbihan department in Brittany in north-western France.-History:At the beginning of the 17th century, merchants who were trading with India had established warehouses in Port-Louis...
on 10 May 1939 when the French Navy formed the 5e Escadre there which controlled all training ships and planned to convert her into a full-time training ship as consort to the training cruiser on 1 June 1940. She would have been renamed La Tour d'Auvergne at that time, as the name Pluton was reserved for mine warfare ships in the French Navy.
As war approached, it was decided to retain her as a minelayer and most of the extra fire control equipment was removed. She was transferred to Brest
Brest, France
Brest is a city in the Finistère department in Brittany in northwestern France. Located in a sheltered position not far from the western tip of the Breton peninsula, and the western extremity of metropolitan France, Brest is an important harbour and the second French military port after Toulon...
as part of the reorganization of the 5e Escadre. She sailed for Casablanca, French Morocco on 2 September with 125 Bréguet mines embarked. She was ordered to lay a defensive minefield there on 4 September, but this order was rescinded the next day, after the mines had already been fuzed, and the ship was ordered to disembark the mines. While landing the mines on 13 September one of them exploded, destroying the ship and killing 186 people. A further 73 crewmen and 47 others were injured and significant damage was caused by flying debris. One gun and some armor was salvaged during the war, but demolition work did not begin until October 1952 and was completed by July 1953.