Hedgehog (weapon)

Last updated

Hedgehog
Hedgehog anti-submarine mortar.jpg
On HMS Westcott, November 1945
TypeAnti-submarine mortar
Place of originUnited Kingdom
Service history
In service1942–?
Used by Royal Navy
United States Navy
United States Coast Guard
Royal Canadian Navy
Production history
Designer Directorate of Miscellaneous Weapons Development
Designed1941 [1]
Specifications
Shell 65 lb (29 kg) [1]
Calibre 7 in (178 mm) [1]
Barrels24 [1]
Effective firing range200–259 m (656–850 ft)
Filling30 lb (14 kg) TNT or 35 lb (16 kg) Torpex [1]
Detonation
mechanism
Contact

The Hedgehog (also known as an Anti-Submarine Projector) was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. [2] It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.

Contents

As the mortar projectiles employed contact fuzes rather than time or barometric (depth) fuzes, detonation occurred directly against a hard surface such as the hull of a submarine making it more deadly than depth charges, which relied on damage caused by hydrostatic shockwaves. During WWII out of 5,174 British depth charge attacks there were 85.5 kills, a ratio of 60.5 to 1. In comparison, the Hedgehog made 268 attacks for 47 kills, a ratio of 5.7 to 1. [3]

Development

The "Hedgehog", so named because the empty rows of its launcher spigots resembled the spines of a hedgehog, was a replacement for the unsuccessful Fairlie Mortar that was trialled aboard HMS Whitehall in 1941. The Fairlie was designed to fire depth charges ahead of a ship when attacking a submarine. The principle of firing projectiles forwards, instead of dropping depth charges over the stern, was considered viable, despite the failure of the Fairlie. This secret research by the Directorate of Miscellaneous Weapons Development (DMWD) led to the development of the Hedgehog. [4]

The weapon was a multiple 'spigot mortar' or spigot discharger, a type of weapon developed between the wars by Lieutenant Colonel Stewart Blacker, RA. The spigot mortar was based on early infantry trench mortars. The spigot design allowed a single device to fire warheads of different sizes. The propelling charge was part of the main weapon and worked against a rod (the spigot) set in the baseplate which fitted inside a tubular tail of the 'bomb'. This principle was first used on the Blacker Bombard 29 mm Spigot Mortar and the later PIAT anti-tank weapon.

The adaptation of the bombard for naval use was made in partnership with MIR(c) under Major Millis Jefferis who had taken Blacker's design and brought it into use with the Army. The weapon fires a salvo of 24 bombs in an arc, aimed to land in a circular or elliptical area about 100 feet (30 m) in diameter at a fixed point about 250 yards (230 m) directly ahead of the attacking ship. The mounting initially was fixed, but was later replaced by a gyro-stabilised one to allow for the rolling and pitching of the attacking ship.

The system was developed to solve the problem of the target submarine disappearing from the attacking ship's ASDIC when closer than the sonar's minimum range. Due to the speed of sound in water, the time taken for the 'ping' echo to return to the attacking ship from the target submarine became too short to allow the human operator to distinguish the returning audible echo from the initial sound pulse emitted by the sonar – the so-called "instantaneous echo", where the output sound pulse and returning echo merge, with the submarine still out of depth charge range. This "blind spot" made the submarine effectively invisible to the sonar, allowing it to make evasive manoeuvres undetected. The solution was a weapon mounted on the foredeck that discharged the projectiles up and over the ship's bow while the submarine was still detectable by the sonar, entering the water some distance in front of the ship.

History

The Hedgehog entered service in 1942. Carrying a 16 kg (35 lb) Torpex charge, each mortar projectile had a diameter of 18 cm (7.1 in) and weighed about 29.5 kg (65 lb). The spigots were angled so the projectiles would land in a circular pattern with a diameter of 40 m (130 ft), about 180 m (590 ft) ahead of the ship's position. The projectiles would then sink at about 7 m/s (23 ft/s). [1] They would reach a submerged U-boat, for example at 200 ft (61 m) in under 9 seconds. Sympathetic detonation of projectiles near those contacting hard surfaces was a possibility, but the number of explosions counted was usually fewer than the number of projectiles launched. [5]

The prototype launcher was tested aboard HMS Westcott in 1941, but there were no submarine kills until November 1942, after it had been installed aboard one hundred ships. [1] Initial success rates, of about 5%, were only slightly better than depth charges. Swells and spray frequently covered the launcher during heavy North Atlantic weather, [6] and subsequent attempts to launch from the soaked launcher were often hindered by firing circuit problems, launching an incomplete pattern. [7] A depth charge total miss would still produce an explosion, leading crews to think that they might have damaged their target or at least demoralised its personnel; a Hedgehog miss was discouragingly quiet. The Royal Navy launched Hedgehog so seldom in early 1943 that a directive was issued ordering captains of ships equipped with Hedgehog to report why they had not used Hedgehog on an underwater contact. [8] The results were blamed on crew inexperience and low confidence in the weapon. However, after an officer from the DMWD was sent to Londonderry Port, where the convoy crews were based, with better training and shipwide talks on examples of successful Hedgehog attacks, the kill rate improved considerably. [9] By the end of the war, statistics showed that on average, one in every five attacks made by Hedgehog resulted in a kill (compared to less than one in 80 with depth charges). [3]

In response to this new deadly threat to its U-boats, the Kriegsmarine brought forward its programme of acoustic torpedoes in 1943, beginning with the Falke . These new "homing" acoustic torpedoes could be employed effectively without the use of a periscope, providing submarines a better chance to remain undetected and evade counterattack.

In the Pacific Theatre, USS England sank six Japanese submarines in two-week period with Hedgehog in May 1944. [5]

In 1946, USS Solar was destroyed after a crewman accidentally dropped a Hedgehog charge near one of her main turret ammunition rooms, triggering three subsequent and devastating explosions.

Operational usage

The launcher had four "cradles", each with six launcher spigots. The firing sequence was staggered so all the bombs would land at about the same time. This had the added advantage of minimising the stress on the weapon's mounting, so that deck reinforcement was not needed, and the weapon could easily be retrofitted to any convenient place on a ship. Reloading took about three minutes. [1]

The Hedgehog had four key advantages over the depth charge:

  1. An unsuccessful attack does not hide the submarine from sonar.
    When a depth charge explodes it can take 15 minutes before the disturbance can settle down enough that sonar becomes effective. Many submarines escaped during the time after an unsuccessful depth charge attack. Since Hedgehog charges only explode on contact, sonar tracking of the submarine is less likely to be disrupted by an unsuccessful Hedgehog attack.
  2. Although knowledge of target depth was less important; the Hedgehog was less successful against deep targets. Doctrine based on combat experience discouraged use on targets deeper than 400 feet (120 m). [1]
    Proximity weapons (such as depth charges) need to be set for the target's correct depth to be effective. Contact-fuzed charges do not have that limitation, and an explosion at the time predicted for the contact-fuzed projectile to reach the target depth may indicate a "hit". [10]
  3. There is no "blind period" allowing the submarine to escape undetected.
    Until depth-finding sonar became available (the first was the Royal Navy's "Q" attachment in 1943), there was a "dead period" during the final moments of a depth-charge attack when the attacker had no knowledge of what the target was doing. U-boat commanders became adept at sharp changes of direction and speed at these moments, avoiding the attack. Weapons such as Hedgehog usable while the submarine was detectable by sonar did not give the submarine a period of invisibility in which to dodge.
  4. A direct hit by one or two Hedgehog bombs was usually sufficient to sink a submarine.[ citation needed ]
    Many depth charges were required to inflict enough cumulative damage to sink a submarine; even then, many U-boats survived hundreds of detonations over a period of many hours—678 depth charges were dropped against U-427 in April 1945. The depth charge, usually exploding at a distance from the submarine, had a cushion of water between it and the target which rapidly dissipated the explosive shock. The Hedgehog's charge, on the other hand, exploded in direct contact with the hull. However, near misses with the Hedgehog were silent and did not cause any damage, unlike the cumulative damage caused by several depth charge near misses; nor did it have the same psychological effect as a depth charge attack.

Derivatives and successors

A Hedgehog launcher on display at the USS Silversides museum in Muskegon, Michigan A hedgehog launcher on display.jpg
A Hedgehog launcher on display at the USS Silversides museum in Muskegon, Michigan

In late 1943 the Royal Navy introduced Squid. This was a three-tubed mortar that launched depth charges. Initially it was used as a single weapon, but when this failed to be successful, it was upgraded to the "double squid" that consisted of two launchers placed in parallel. In 1955 this system was upgraded to the three-barreled Limbo that launched 400 lb (180 kg) Minol charges.

The United States produced a rocket version of Hedgehog called Mousetrap, then Weapon Alpha as a replacement for both. Still, Hedgehog remained in service with the United States Navy into the Cold War until both Hedgehog and the less satisfactory Weapon Alpha were replaced by ASROC. [12]

Three "Hedgerow" flotillas of specialized Landing Craft Assault boats carrying the Hedgehog instead of troops were used during the Normandy landings. [13] An addition of impact fuse extensions in the projectile noses enabled detonating the warheads above ground. The bombs were used to clear 100-yard-wide paths through mines and barbed wire obstacles on the beach. [14] [15]

The Australian Army adapted the marine Hedgehog into a land-based seven-shot launcher that could be mounted on the back of Matilda tanks.

From 1949, a copy of Hedgehog was produced in the USSR as MBU-200, developed in 1956 into MBU-600 (also known as RBU-6000) with increased range of 600 metres (2,000 ft).

Weapons derived from the Hedgehog have been largely phased out from Western navies in favor of homing torpedoes. MBU-600 and its derivatives remain an important part of the Russian Navy's (as well as Russia's allies, such as India) anti-submarine arsenal to this day.

Former operators

General characteristics

Live and practice projectiles - note the protective fuze caps (22) shown removed in the picture at the top of page. Hedgehog ASW projectile diagram.jpg
Live and practice projectiles – note the protective fuze caps (22) shown removed in the picture at the top of page.

For a single bomb

Variants

Related Research Articles

RUR-5 ASROC Anti-submarine missile system

The RUR-5 ASROC was an all-weather, all sea-conditions anti-submarine missile system. Developed by the United States Navy in the 1950s, it was deployed in the 1960s, updated in the 1990s, and eventually installed on over 200 USN surface ships, specifically cruisers, destroyers, and frigates. The ASROC has been deployed on scores of warships of many other navies, including Canada, Germany, Italy, Japan, the Republic of China, Greece, Pakistan and others.

Naval mine Explosive weapon for use in seas and waterways, triggered by the targets approach

A naval mine is a self-contained explosive device placed in water to damage or 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, any vessel. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake an expensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered.

Depth charge Anti-submarine weapon

A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge, typically at a specific depth. Depth charges can be dropped by ships, patrol aircraft, and helicopters.

Mortar (weapon) Artillery weapon that launches explosive projectiles at high angles

A mortar is usually a simple, lightweight, man-portable, muzzle-loaded weapon, consisting of a smooth-bore metal tube fixed to a base plate with a lightweight bipod mount and a sight. They launch explosive shells in high-arcing ballistic trajectories. Mortars are typically used as indirect fire weapons for close fire support with a variety of ammunition.

<i>Kaiten</i> Manned torpedoes and suicide craft, used by the Imperial Japanese Navy in the final stages of World War II

Kaiten were manned torpedoes and suicide craft, used by the Imperial Japanese Navy in the final stages of World War II.

Squid (weapon) Depth charge mortar

Squid was a British World War II ship-mounted anti-submarine weapon. It consisted of a three-barrelled mortar which launched depth charges. It replaced the Hedgehog system, and was in turn replaced by the Limbo system.

Anti-submarine weapon

An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.

Limbo (weapon) Type of anti-submarine mortar

Limbo, or Anti Submarine Mortar Mark 10, was the final development of the forward-throwing anti-submarine weapon Squid designed during the Second World War and was developed by the Admiralty Underwater Weapons Establishment in the 1950s.

Anti-submarine mortars are artillery pieces deployed on ships for the purpose of sinking submarines by a direct hit with a small explosive charge. They are often larger versions of the mortar used by infantry and fire a projectile in relatively the same manner. They were created during World War II as a development of the depth charge and work on the same principle.

Mousetrap (weapon)

Mousetrap was an anti-submarine rocket used mainly during the Second World War by the U.S. Navy and the U.S. Coast Guard. Its development was begun in 1941 as a replacement for Hedgehog, a British-made projector, which was the first ahead-throwing ASW weapon. These, however, were spigot-launched, placing considerable strain on the launching vessel's deck, whereas Mousetrap was rocket-propelled. As a result, Mousetrap's four or eight rails for 7.2-inch (183 mm) rockets saved weight and were easier to install.

Anti-submarine warfare Branch of naval warfare

Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, or other submarines to find, track, and deter, damage, or destroy enemy submarines.

USS <i>England</i> (DE-635) Buckley-class destroyer escort of the United States Navy in service 1943-1945

USS England (DE-635), a Buckley-class destroyer escort of the United States Navy, was named in honor of Ensign John C. England (1920–1941), who was killed in action aboard the battleship Oklahoma during the Japanese attack on Pearl Harbor on 7 December 1941. Her sinking of six Japanese submarines in twelve days is a feat unparalleled in the history of antisubmarine warfare.

Anti-submarine missile type of weapon used against submarines

An anti-submarine missile is a standoff anti-submarine weapon. Often a variant of anti-ship missile designs an anti-submarine systems typically use a jet or rocket engine, to deliver: an explosive warhead aimed directly at a submarine; a depth charge, or; a homing torpedo that is carried from a launch ship, or other platform, to the vicinity of a target.

<i>Commandant Rivière</i>-class frigate

The Commandant Rivière class was a class of frigates built for the French Navy in the late 1950s and early 1960s. Labeled "aviso-escorteur", they were designed to perform the role of overseas patrol in peacetime and anti-submarine escort in wartime.

USS <i>Wyman</i> (DE-38)

USS Wyman (DE-38) was an Evarts-class destroyer escort of the United States Navy during World War II. She was promptly sent off into the Pacific Ocean to protect convoys and other ships from Japanese submarines and fighter aircraft. She performed dangerous work, including participating in the sinking of two Japanese submarines, and sailed home proudly with six battle stars.

RUR-4 Weapon Alpha Type of standoff anti-submarine rocket

The RUR-4 "Weapon Alpha" was an American naval ahead-throwing antisubmarine warfare (ASW) rocket launcher. It was designed between 1946 and 1949 and was installed on warships from 1951 to 1969. Unlike depth charges, it was designed to attack enemy submarines without requiring the attacking ship to be located directly above the submarine being attacked.

When the United States entered World War II at the end of 1941, the United States Navy found itself deficient in ocean escort-type vessels. A crash building program was instituted; but, to meet more immediate needs, the government contracted with shipbuilding firms in England and Canada to build Flower-class corvettes. Vim (PG-99) was one of those British-type escorts. She was launched on 1 April 1943 at the Collingwood Shipyard in Collingwood, Ontario. Nine days later, however, she was transferred to the Royal Navy under the terms of the lend-lease agreement in return for another Flower-class corvette then under construction in Canada. The British renamed her HMS Statice, and she served the Royal Navy under the name through World War II. On 21 June 1946, she was returned to the United States Navy. Though carried on the Navy list as PG-99, the corvette never saw active service with the United States Navy. She was sold on 7 May 1947. To whom she was sold and to what purpose she was put is unknown.

The submarine I-12 was a Japanese A2 type long-range fleet submarine. She was built at the Kawasaki's shipyard in Kobe.

<i>Dealey</i>-class destroyer escort ship class

The Dealey-class destroyer escorts were the first post-World War II escort ships built for the United States Navy.

The Fairlie Mortar was an unsuccessful British anti-submarine mortar design of early World War II. It projected multiple small anti-submarine bombs simultaneously, 10 from each side of the ship's forecastle, each containing 20 pounds of explosive. The Fairlie Mortar was not a success and 'Hedgehog', a spigot mortar projecting 24 small bombs from a single platform, eventually became the predominant British ship-borne anti-submarine weapon in the war.

References

  1. 1 2 3 4 5 6 7 8 9 Campbell, John (1985). Naval Weapons of World War Two . Annapolis, Maryland: Naval Institute Press. pp.  91&166. ISBN   978-0-87021-459-2.
  2. Keegan, John (1989). The Price of Admiralty . New York: Viking. p.  278. ISBN   978-0-670-81416-9.
  3. 1 2 "Britain ASW Weapons". www.navweaps.com. Retrieved 28 May 2015.
  4. Fitzsimons, Bernard, ed. (1977). "Illustrated Encyclopedia of 20th Century Weapons & Warfare". 12. London: Phoebus: 1283.Cite journal requires |journal= (help)
  5. 1 2 Lanier, William D. and Williamson, John A., CAPT USN. "The Twelve Days of the England". United States Naval Institute Proceedings, March 1980, pp. 76–83.
  6. Morison, Samuel Eliot (1975). The Battle of the Atlantic. I. Boston: Little, Brown and Company. p. 212.
  7. Middlebrook, Martin (1976). Convoy. New York: William Morrow and Company. p. 165.
  8. Milner, Marc (1985). North Atlantic Run. Annapolis, Maryland: Naval Institute Press. p. 266. ISBN   978-0-87021-450-9.
  9. Pawle, G (2009). The Wheezer and Dodgers. The inside story of clandestine weapon development in World War II. Seaforth Publishing. ISBN   978-1848320260.
  10. Gretton, Peter (1974). Crisis Convoy. Annapolis, Maryland: Naval Institute Press. p. 42. ISBN   978-0-87021-925-2.
  11. USS Moberly, PF-63 , U.S. Coast Guard, p. 4
  12. Albrecht, Gerhard. Weyer's Warship of the World 1969. (Annapolis, MD: United States Naval Institute Press, 1969), pp. 325-328 & 340
  13. "Major Landing Craft of World War II". The Royal Marines Museum. 6 October 2011. Archived from the original on 9 June 2014. Retrieved 21 December 2016.
  14. "Royal Marines & Landing Craft" (PDF). Royal Marine Museum. Archived from the original (PDF) on 7 October 2009.