Hedgehog (weapon)

Hedgehog
On HMS Westcott, November 1945
Type	Anti-submarine Mortar
Place of origin	United Kingdom
Service history
In service	1942–?
Used by	Royal Navy  United States Navy  Royal Canadian Navy
Production history
Designer	Directorate of Miscellaneous Weapons Development
Designed	1941
Specifications
Shell	65 lb (29 kg)
Calibre	7 in
Barrels	24
Effective firing range	200 to 259 m
Filling	30 lb TNT or 35 lb (16 kg) Torpex
Detonation mechanism	Contact

The Hedgehog (also known as an Anti-Submarine Projector) was a forward-throwing anti-submarine weapon that was used during the Battle of the Atlantic in 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. 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 barometric (depth) fuzes, detonation occurred directly against a hard surface like the hull of a submarine making it more deadly than depth charges, which relied on damage caused by hydrostatic shockwaves. Statistics show that in the Second World War 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.

The "Hedgehog", so named because the empty rows of its launcher spigots resembled the spines of a hedgehog, was a replacement to the unsuccessful Fairlie Mortar that was trialled aboard HMS Whitehall (D94) in 1941. Although a failure, the Fairlie was designed to fire depth charges ahead of a ship when attacking a submarine. This principle of forward-firing projectiles was considered viable. It was from this, secret research undertaken by the Directorate of Miscellaneous Weapons Development (DMWD) led to the development of the Hedgehog.