Sea Slug (missile)

Seaslug
Seaslug Mk. II missile
Type	surface-to-air missile
Place of origin	UK
Service history
In service	1961 - 1991
Used by	UK (Royal Navy), Chile
Wars	Falklands War
Production history
Designed	Mark 1; 1961 Mark 2; 1965
Manufacturer	Armstrong Whitworth
Variants	Mark 1, Mark 2
Specifications
Weight	Mk.1; 2,080 kg Mk.2; 2,384 kg
Length	Mk.1; 6.0 m Mk.2; 6.1 m
Diameter	Mk.1; 0.42 m Mk.2; 0.41 m
Warhead	Mk.1; 200 lb (91 kg) blast Mk.2; continuous-rod warhead
Engine	4 solid fuel jettisoned boosters & liquid fuel sustainer
Wingspan	1.44 m
Operational range	Mk.1; 30,000 yards (27,000 m) Mk.2; 35,000 yards (32,000 m)
Flight ceiling	Mk.1; 55,000 feet (17,000 m) Mk.2; 65,000 feet (20,000 m)
Speed	Mk.1; 685 mph (1,102 km/h) Mk.2; 1,370 mph (2,200 km/h)
Guidance system	Beam riding
Steering system	control surface
Launch platform	Ship

Seaslug was a first generation surface-to-air missile designed by Armstrong Whitworth (later part of the Hawker Siddeley group) for use by the Royal Navy. It came into operational service in the 1960s and was still in use at the time of the Falklands War.

Seaslug was intended to engage high-flying targets such as reconnaissance aircraft or bombers before they could launch stand-off weapons. Later improvements meant that it could also be used against ships.

Work on what became Seaslug began in 1949 under 'Stage 1' of the Royal Navy's post-war missile program. The weapon was intended to counter high-altitude nuclear-armed bombers before they could release their weapons. Development made use of on an earlier programme by the Fairey Aviation Company known as "LOPGAP" (Liquid oxygen / petrol guided anti-aircraft projectile), the Clausen Rolling Platform at RAE Aberporth and a Victory Ship specially converted into prototype escort ship, HMS Girdle Ness, was procured. The original system differed in having a triple launcher. The Seaslug Mark 1 finally entered service in 1961 on County class destroyers, each fitted with a single twin missile launcher.

The missile had four wrap-around booster motors which separated after launch. After separation the main motor ignited to power the missile to the target. The booster motors were positioned at the front of the missile, but this unusual arrangement gave acceleration, and, with the motor nozzles angled outwards at 45°, the missile entered a gentle roll at launch, evening out differences in the thrusts of the boosters. This meant that large stabilising fins as used on contemporary missiles in service with the Royal Air Force (Bristol Bloodhound) and the British Army (English Electric Thunderbird) were not required. Once the boosters were clear the control surfaces became active.