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Hedgehog (weapon)

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From Wikipedia, the free encyclopedia

1940s shipboard multi-barrel anti-submarine mortar weapon of British origin

For the anti-tank obstacle, see Czech hedgehog.

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Production historyDesignerDirectorate of Miscellaneous Weapons DevelopmentDesigned1941[1]SpecificationsShell65 lb (29 kg)[1]Calibre7 in (178 mm)[1]Barrels24[1]Effective firing range656–850 ft (200–259 m)Filling30 lb (14 kg) TNT or 35 lb (16 kg) Torpex[1]Detonation<br>mechanism<br>Contact

The Hedgehog (also known as an Anti-Submarine Projector) was a forward-throwing anti-submarine mortar 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.

As the mortar projectiles employed contact fuzes rather than time or bathymetric (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 World War II out of 5,174 British depth charge attacks there were 85.5 kills,[a] 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<br>[edit]

The Hedgehog, so named because the empty rows of its launcher spigots resembled the spines on the back of a hedgehog, was a replacement for the unsuccessful Fairlie Mortar, which was secretly tested 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 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 a baseplate which fitted inside the tubular tail of the bomb. This principle was first used in the Blacker Bombard 1.1-inch (29 mm) Spigot Mortar, and it was also used in 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 relative location about 250 yards (230 m) directly ahead of the attacking ship. The mounting initially was fixed, but it 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...