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British Mines British Mines Updated 23 May 2006 Information . Nomenclature Until after the end of World War II most British mines had both a "type" letter and a Mark number. Between about 1918 and 1930 horned contact mines were designated as either "Type H" for those mines using Hertz (acid) horns or "Type T" for Trigger (switch) mines. Moored mines designed after the early 1920s generally had only Mark numbers, but this was not always the case. From that period onwards until after the end of World War II there were the following designations in general use: Mark numbers only - Moored contact, snagline, acoustic and antenna mines A Mark Y - Air launched mines M Mark Y - Special magnetic ground mines S Mark Y - Submarine launched ground mines Where "Y" represents the various mark numbers. In addition, there were also "R" mines, intended for use in rivers, "L" mines that were shore controlled and an "O" mine that oscillated from bottom to surface. These were all apparently scrapped shortly after the war ended. Sometime in the 1950s these designations were merged into a single Mark series. Unfortunately, Mark numbers were then reused, causing some confusion. Triggering or Fuzes Contact mines with Hertz Horns were common in designs from World War I to about 1922. Each horn contained acid. Contact with the horn broke open the acid container which energized a battery and exploded the mine. British contact mines were considered unreliable until a German one was captured and duplicated. In the 1920s a variation was developed that replaced the acid horns with switch triggers that activated when a ship hit a horn. By definition, horned mines were short ranged weapons and fields needed to be densely packed to be effective against shipping. http://www.navweaps.com/Weapons/WAMBR_Mines.htm (1 of 10)7/20/2006 16:53:56 British Mines Hertz Horn Picture copyrighted by Royal Naval Minewarfare & Clearance Diving Officer's Association Late in World War I the British developed a magnetic trigger for ground mines. This was not very successful and little post-war work was done in this area for over a decade. Not until 1936 was a new development order placed for a magnetic trigger for moored mines. A small production order was placed in July 1939 with some 200 being delivered by April 1940. These used a coil-rod (CR) which was fired by an increase in the rate of change of magnetism in the horizontal portion of the field around the trigger. Various delay mechanism were employed to ensure that the ship was close to the mine before firing, not always successfully. Antenna mines using underwater electric potential (UEP) were developed during World War II, apparently with USA help. An acoustic trigger was developed with USA help in the summer of 1942 and first used that fall. Combined acoustic/magnetic triggers were developed the following year and first employed in April 1943. A magnetic/pressure trigger was developed late in the war but it did not see service. British Aerospace developed a microprocessor sensor and processing unit (SAP) in the 1980s that used magnetic and pressure sensors. This design analyzes acoustic frequencies in three bands intended to cover sonar, engines and propeller noises so as to provide a high degree of target identification. The mines can be programmed prior to launch to fire for specific kinds of targets. Explosives http://www.navweaps.com/Weapons/WAMBR_Mines.htm (2 of 10)7/20/2006 16:53:56 British Mines Owing to shortages of TNT and RDX (cyclonite) most World War II mines had had 50/50 ammonium nitrate and TNT (amatol) warheads. This was a low quality explosive but was later improved by the addition of about 20% aluminum to produce minol. During the modernization program of the 1980s it was discovered that many of the TNT and RDX fillings of the World War II-era mines had crystallized, causing at least two mines to explode prematurely. Effectiveness during World War I During the "Great War" the British attempted a variety of mine and physical barriers across the Dover Straits, the North Channel and the Adriatic Sea with a total of 128,000 mines being laid. Most of these fields were of relatively limited value, although some success was achieved late in the war. British mines sank a total of 150 enemy war vessels and naval auxiliaries including some 35 U-boats. Worldwide, British mines are reckoned to have sunk a total of 1,047 enemy vessels and damaged a further 541. A total of 48 German submarines were sunk by all Allied mines in World War I. British contact mines of this era suffered from a variety of faults, especially when compared to the German equivalents and to the USA "K" type mines. As noted above, a magnetic ground mine was developed and deployed in August of 1918, but this was too late to be of significant use and was not very successful. Effectiveness during World War II During World War II the RAF Home Command laid 48,158 mines during the entire war in enemy waters and these sank 545 merchant ships of 591,143 tons gross and 217 assorted warships of 147,264 tons displacement. Over 20,000 additional mines were laid by surface ships and submarines. The success of these additional mines is not broken out, but one souce claims that British mines in total sank 1,050 Axis warships and merchant ships and damaged a further 540. As opposed to the successes achieved via offensive mining, it appears that the British greatly overrated the effectiveness of mines as defensive weapons during World War II. Some 170,000 mines were laid in protective fields by surface ships, the majority in the Iceland and Faeroes passages. This massive effort resulted in exactly one U-boat (U-647) being sunk and had no appreciable effect on the number of U-boats engaged in anti-commerce operations. This might have been forecasted by a study of the 1918 Orkney to Norway mine barrier (also known as the North Sea Mine Barrage) which was an expensive failure. In some ways, these defensive fields restricted the Royal Navy more than the Kriegsmarine. For example, although the German small battleships Gneisenau and Scharnhorst were able to traverse the Dover Straits in 1942, the first http://www.navweaps.com/Weapons/WAMBR_Mines.htm (3 of 10)7/20/2006 16:53:56 British Mines British capital ship to do so was HMS Warspite, which passed that way only after the Normandy invasion. . World War I . Unknown An early World War I mine apparently designed by Sir Hiram Maxim, of machine gun fame. No details are available. Images at The Vickers Photographic Archives See Furness Railway Steam Mine . Type H Mark II The first reliable British contact-type mine, this was copied from the successful German Hertz-horn contact mine. Production started in early 1917, but it not available in useful numbers until November 1917. Spherical design. Total weight not available, charge was 320 lbs. (145 kg) and used Hertz horns. Still in use early World War II. Images at The Vickers Photographic Archives See 5163 and 5164 . Type H Mark IV Another Hertz-horn, spherical design. Total weight not available, charge was 150 lbs. (68 kg). Mark I (M) Ground mine. The first magnetic mine, used operationally in August 1918. 1,000 lbs (554 kg) crude TNT charge. Obsolete by the start of World War II but still used in some numbers after 1939. . Between the Wars . http://www.navweaps.com/Weapons/WAMBR_Mines.htm (4 of 10)7/20/2006 16:53:56 British Mines Contact Mines Britain developed a series of Hertz (acid) horned contact mines just after World War I, with Vickers being heavily involved in production both for the Royal Navy and for other nations. These appear to have been improved versions of the Type H Mark II. I lack data on most of these early designs, but there are many pictures of them and their components at the following location: Images at The Vickers Photographic Archives See Submarine Mine . Of special interest in these photographs are the "sinkers" attached to the contact mines. These are the "boxes" that the mines sit in. When deployed from the mine laying craft, the mine and its sinker fall to the bottom of the sea, where upon the mine, connected to the sinker by a tether, is released to float to the top. Type T Mark II Moored contact mine. Constructed from two hemispheres with a belt between. Charge weight was 440 lbs. (200 kg) with a 500 foot (150 m) mooring wire. Designed to be placed in waters up to 150 feet (45 m) deep. Type T Mark III Moored contact mine. Similar to the Type T Mark II. Type H Mark VA Moored contact mine. Mark XIV A 1920s design with either a 320 lbs. (145 kg) or 500 lbs. (227 kg) charge and Hertz horns. When switch horns were developed this mine became the Mark XVII. Mark XV Moored contact mine. Constructed from two 40 inch (102 cm) hemispheres with a 13.5 inch (34 cm) belt between. There were 11 switch horns. Buoyancy 840 lbs. (381 kg) with a 320 lbs. (145 kg) charge and 650 lbs. (295 kg) with a 500 lbs. (227 kg) charge. Originally designed for 200-1000 fathoms (365-1830 m) but its high buoyancy made it valuable in tidal currents and it became a general purpose mine. In 1949, 1,972 were in storage. Redesignated as "Mark 15" in the 1950s. Mark XVI Similar to the Mark XV except that the shell was thicker. Designed for laying in 100 fathoms (180 m) or less. Hertz horns were used with a 320 lbs. (145 kg) explosive charge. http://www.navweaps.com/Weapons/WAMBR_Mines.htm (5 of 10)7/20/2006 16:53:56 British Mines Mark XVII Similar to the Mark XIV but with a larger belt. Used 11 switch horns and could be laid in waters up to 500 fathoms (915 m) deep. Available charges were 320 lbs. (145 kg), 450 lbs. (204 kg) or 500 lbs. (227 kg). This was the standard British contact mine of World War II. In 1949, 14,933 were in storage. Mark XIX A small spherical mine with eight switch horns and a 100 lbs. (45 kg) charge. Could be laid in 200 fathoms (360 m) and was intended for anti-submarine barrages at 35 feet (10.7 m) below the surface. The parts were mainly used to build up Mark XIXS and Mark XXVII mines and the rest scrapped in 1944. The Mark XIXS was designed to be used against shallow draft ships. . World War II . Moored Mines Mark XVII Moored acoustic mine for use against S and R-boats. Laid in 7-40 fathoms (13-73 m). The charge was 320 lbs. (145 kg) originally and later upped to 500 lbs. (227 kg) in some. In 1949, 14,933 were in storage. Redesignated as "Mark 17" in the 1950s. Mark XX Moored antenna mine similar in appearance to the Mark XVII with either a 320 lbs. (145 kg) or 500 lbs. (227 kg) charge. The upper antenna was 60 feet (18 m) and the lower antenna was 74 feet (22.5 m) long. Mark XX* used only the lower antenna. Mark XXII and XXII* Similar to Mark XX but had a floating 60 foot (18 m) tubular antenna instead of solid ones supported with floats. Used with either a 320 lbs. (145 kg) or 500 lbs. (227 kg) charge. Mark XXV A snagline mine intended to be used against S-boats. 40 inches (102 cm) in diameter and very similar to Mark XII*. There were four switch horns, one of which had codline and bottle corks attached. 500 lbs. (227 kg) charge and the mine was laid 15 feet (4.6 m) below the low water mark. Approved in 1943 but replaced by the Mark XVII snagline version shortly after the war. Mark XXVII Snagline version of the Mark XIX in service in 1942 but obsolete by 1944. Magnetic Ground Mines http://www.navweaps.com/Weapons/WAMBR_Mines.htm (6 of 10)7/20/2006 16:53:56 British Mines M Mark I Similar in design to the Mark XV. The mine was emplaced 80-1000 fathoms (146-1,830 m) and had a 500 lbs. (227 kg) charge. In 1949, 8,948 were in storage. M Mark II (formerly Type G) Submarine launched ground mine. Two of these would occupy the space of one torpedo. Used a CR magnetic trigger and weighed 1,760 lbs. (798 kg) with a 1,000 lbs. (454 kg) minol charge. Could be laid at 8 knots in 5-60 fathoms (9-110 m) and was carried by "T" and a few "S" class submarines. A modification designated Mark IID could be carried by Dutch submarines. A contract for 2,000 was placed in 1940 but production was halted in November 1942. In 1949, 1,310 were in storage. M Mark III (formerly Type J) A CR magnetic mine with a 1,500 lbs. (680 kg) minol charge. Designed for laying from wide-track mine-layer rails in 6-20 fathoms (11-37 m). First deliveries in 1941. Modified in 1942 to increase the charge to 1,600 lbs. (726 kg) amatol or 1,750 lbs. (794 kg) minol. Acoustic triggers added in 1943. M Mark V (formerly Type Q) Designed in early 1942 for "A" class submarines. Had increased magnetic sensitivity and acoustic firing. Weight was about 1,880 lbs. (853 kg) with about a 1,110 lbs. (499 kg) minor charge. Production was stopped in November 1942 but resumed in September 1945. Post-war, further development led to a 1,930 lbs. (875 kg) mine with a 1,030 lbs. (467 kg) charge with magnetic, acoustic or combinational fuzing which could be laid by submarines or coastal forces in 6.5 to 20 fathoms. Redesignated as "Mark 5" in the 1950s. Aircraft-launched Mines A Mark I Originally designed to fit the same dropping gear as the 18 inch (45 cm) Mark XI torpedo. First used magnetic only triggering but later versions incorporated acoustic, acoustic-magnetic and magnetic-pressure triggering, although the last one was not used in service. Weight was about 1,500 lbs. (680 kg) with a 750 lbs. (340 kg) charge. A Mark II Similar to A Mark I but with less use of scarce material. A Mark III Similar to Mark I but with less use of scarce material. Some were fitted for impact firing. Mark III*** was for dropping from Mosquitos at 260 knots from 300 feet (90 m) into inland waterways. Designed to be dropped from 4,000 lbs. (1,814 kg) bomb gear. A Mark IV Similar to A Mark III but built by Pressed Steel Co. http://www.navweaps.com/Weapons/WAMBR_Mines.htm (7 of 10)7/20/2006 16:53:56 British Mines A Mark V A parachute mine with magnetic firing dropped from 1,000 lbs. (454 kg) bomb racks. Production started in August 1940. Weight 1,080 lbs. (490 kg) with a 700 lbs. (318 kg) minol charge. A Mark VI Production started in 1944 for this parachute mine intended to replace A Marks I-IV. Used an acoustic-magnetic trigger and was the dimensions of a 2,000 lbs. (907 kg) blast bomb. Charge was 1,000 lbs. (454 kg) amatol or 1,100 lbs. (499 kg) minol. Without parachute could also be laid by MTBs or from low altitude. In 1949, some 5,707 were in storage. A Mark VII An improved version of the A Mark VI introduced in 1944. Had only magnetic triggering as originally deployed, but acoustic sensors were added sometime later, possibly post- war. Weight of 1,100 lbs. (499 kg) with a 555 or 610 lbs. (252 or 277 kg) charge. Minimum case depth was 40 feet (12 m). Dimensions were 18.5 in x 7.5 feet (47 cm x 2.3 m) or 6.9 feet (2.1 m) without parachute. In 1949, 4,502 were in storage. Redesignated as "Mark 7" in the 1950s. A Mark VIII A small magnetic mine for rivers and designed to fit 500 lbs. (227 kg) GP bomb gear. An acoustic version, A Mark VIII* was apparently not used during the war. Weight of 500 lbs. (227 kg) with a 180 lbs. (82 kg) amatol or 200 lbs. (91 kg) minol charge. A Mark IX Similar to A Mark VI but designed to fit newer aircraft. Could use a pressure trigger as well as magnetic. Post-war modifications added acoustic sensors. Weight 1,775-1,845 lbs. (805-837 kg) with a 1,045 (474 kg) minol charge. Minimum case depth was 40 feet (12 m). Dimensions were 18.5 in x 9.33 feet (47 cm x 2.8 m) or 8.5 feet (2.6 m) without parachute. In 1949, 1,427 were in storage and 400 were on order. A Mark X A moored mine designed to fit 1,000 lbs. (454 kg) GP bomb gear. Had a very small charge of 100 lbs. (45 kg). Used inertia switches for firing and could be laid in 10-40 fathoms (18-73 m). There was little use for this mine and it was not in service. A Mark XI Intended for underwater attack on capital ships, particularly in anchorages where torpedoes and conventional bombs could not be employed. Some 400 were built from A Mark III but the order was cancelled in 1945. Charges for Midget Submarines http://www.navweaps.com/Weapons/WAMBR_Mines.htm (8 of 10)7/20/2006 16:53:56 British Mines Chariot Weight about 590 lbs. (268 kg) with a 590 lbs. (268 kg) Torpex charge. Time fuzed. X-Craft Mark XX charge case. Weight 5.5 tons (5.59 mt) with a charge of 3,700 lbs. (1,678 kg) minol with the addition of 5-10% cyclonite to improve total combustion. Time fuzed. . Post-World War II . A Type S Developed in 1953-56 as air-launched ASW ground mine. Weight 1,000 lbs. (454 kg). Used combination acoustic-magnetic-pressure triggers. At the time of development, the standard air-drop requirments were 450 knots/5,000 feet (1,500 m) and 12 foot (3.7 m) depth for RN aircraft and 35,000 feet (10,700 m) and 40 foot (12 m) depth for RAF aircraft. A Mark XII Air-launched ASW ground mine developed in 1953-56 as a heavier companion to the A Type S. Weight 2,000 lbs. (908 kg). Used combination acoustic-magnetic-pressure triggers. At the time of development, the standard air-drop requirments were 450 knots/5,000 feet (1,500 m) and 12 foot (3.7 m) depth for RN aircraft and 35,000 feet (10,700 m) and 40 foot (12 m) depth for RAF aircraft. Redesignated as "Mark 12" in the 1950s. Mark 10 Aircraft laid buoyant mine. Used a contact trigger and the cable length had to be adjusted before flight. This mine was intended to be as simple and inexpensive as possible and was the only weapon capable of being used in waters not accessible to submarines and surface ships. Weight of 810 lbs. (367 kg) with a 100 lbs. (45 kg) minol charge. Dragonfish Small anti-invasion mine of about 187 lbs. (85 kg) intended for use in shallow waters of 100 feet (30 m) or less. The technology is similar to that in the Marconi Stonefish, which is intended to be used in deeper waters. Uses two types of influence (magnetic) sensors and has a 200 day operational lifetime. Produced only for export. http://www.navweaps.com/Weapons/WAMBR_Mines.htm (9 of 10)7/20/2006 16:53:56 British Mines Stonefish Uses a combination acoustic/magnetic/pressure trigger and replaces earlier British mines. Can be launched by plane, ship or submarine for use in depths of 100-660 feet (30-200 m). Weight of 2,180 lbs. (990 kg) with a 1,320 lbs. (600 kg) Torpex warhead. Shelf life is 20 years with a 700 day operational lifetime. The Mark 2 is shorter and lighter with a 1,100 lbs. (500 kg) charge of PBX and a much simpler firing circuit (over 30 components were eliminated). Never purchased by the Royal Navy, this mine has only been produced for export. .. Current Usage . As of the early 1990s, only three types of mines were in service use: Mark 5 - See M Mark V for details Mark 12 - See A Mark XII for details Mark 17 - See Mark XVII for details The Mark 17 appears to have been withdrawn from service sometime in the mid to late 1990s. Britain has not manufactured mines for some years, probably since the 1950s. In 1982, a modernization program was announced for about 1,500 mines, some of them dating back to World War II. In 1984 it was reported that the entire program might have to be abandoned as inspection showed that the TNT or RDF fillings had crystallized, causing at least two mines to explode prematurely. The solution was to X-ray each mine and discard those that showed cracks or crystallization. As of 1994, only Mark 12 mines had been modernized, mainly by adding the British Aerospace microprocessor sensor and processing unit (SAP) described above. . Data from "Naval Weapons of World War Two" by John Campbell "America's Use of Sea Mines" by Robert C. Duncan, Ph.D. "US Naval Weapons", "The Naval Institute Guide to World Naval Weapon Systems 1991/92" and "The Naval Institute Guide to World Naval Weapon Systems 1994 Update" all by Norman Friedman "Find and Destroy: Antisubmarine Warfare in World War I" by Dwight R. Messimer http://www.navweaps.com/Weapons/WAMBR_Mines.htm (10 of 10)7/20/2006 16:53:56
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