![Armstrong Whitworth Seaslug missile](https://upload.wikimedia.org/wikipedia/commons/5/5c/Armstrong_Whitworth_Seaslug_missile.jpg)
Seaslug was a first-generation
surface-to-air missile
A surface-to-air missile (SAM), also known as a ground-to-air missile (GTAM) or surface-to-air guided weapon (SAGW), is a missile designed to be launched from the ground to destroy aircraft or other missiles. It is one type of anti-aircraft syst ...
designed by
Armstrong Whitworth
Sir W G Armstrong Whitworth & Co Ltd was a major British manufacturing company of the early years of the 20th century. With headquarters in Elswick, Newcastle upon Tyne, Armstrong Whitworth built armaments, ships, locomotives, automobiles and a ...
(later part of the
Hawker Siddeley
Hawker Siddeley was a group of British manufacturing companies engaged in aircraft production. Hawker Siddeley combined the legacies of several British aircraft manufacturers, emerging through a series of mergers and acquisitions as one of onl ...
group) for use by the
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
. Tracing its history as far back as 1943's LOPGAP design, it came into operational service in 1961 and was still in use at the time of the
Falklands War
The Falklands War ( es, link=no, Guerra de las Malvinas) was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British dependent territories in the South Atlantic: the Falkland Islands and its territorial de ...
in 1982.
Seaslug was intended to engage high-flying targets such as reconnaissance aircraft or bombers before they could launch stand-off weapons. It was only fitted to the Royal Navy's eight
County-class destroyer
The County class was a class of British guided missile destroyers, the first such warships built by the Royal Navy. Designed specifically around the Seaslug anti-aircraft missile system, the primary role of these ships was area air defence aro ...
s which were designed around the missile system. Seaslug was only fired in anger once as an anti-aircraft missile, from during the Falklands War, but missed its target. Later improvements meant that it could also be used against ships and ground targets.
It was planned that Seaslug's medium-range role was to be supplanted by a very long-range missile known as
Blue Envoy
Blue Envoy (a Rainbow Code name) was a British project to develop a ramjet-powered surface-to-air missile. It was tasked with countering supersonic bomber aircraft launching stand-off missiles, and thus had to have very long range and high-speed ...
, but this was passed over in favour of a new medium-range system,
Sea Dart
Sea Dart, or GWS.30 was a Royal Navy surface-to-air missile system designed in the 1960s and entering service in 1973. It was fitted to the Type 42 destroyers (United Kingdom and Argentina), Type 82 destroyer and s of the Royal Navy. Originally ...
. Sea Dart entered service in 1973 on the
Type 82 destroyer
The Type 82 or ''Bristol''-class destroyer was a 1960s Guided-missile destroyer, guided missile destroyer design intended to replace s in the Royal Navy. Originally eight warships were planned to provide area air-defence for the planned CVA-0 ...
s and replaced Seaslug during the 1980s as the s were removed from service.
Development
Initial concept
In 1943, the German ''
Luftwaffe
The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...
'' began the use of
anti-shipping missile
An anti-ship missile (AShM) is a guided missile that is designed for use against ships and large boats. Most anti-ship missiles are of the sea skimming variety, and many use a combination of inertial guidance and active radar homing. A good nu ...
s and guided bombs in the Mediterranean Sea during Allied operations against Italy. These weapons were released outside of
anti-aircraft gun
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
range, which meant that naval operations lacking complete
air superiority
Aerial supremacy (also air superiority) is the degree to which a side in a conflict holds control of air power over opposing forces. There are levels of control of the air in aerial warfare. Control of the air is the aerial equivalent of c ...
would be open to attack with no effective response from the ships. A solution for long-range anti-aircraft was required. On 16 March 1944 the first meeting of the "Guided Anti-Aircraft Projectile Committee", or GAP Committee, was held.
The
Admiralty Signals Establishment
Admiralty most often refers to:
*Admiralty, Hong Kong
*Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964
*The rank of admiral
*Admiralty law
Admiralty can also refer to:
Buildings
*Admiralty, Trafa ...
(ASE), in charge of the Navy's
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
development, was working on new radars featuring
radar lock-on
Lock-on is a feature of many radar systems that allow it to automatically follow a selected target. Lock-on was first designed for the AI Mk. IX radar in the UK, where it was known as lock-follow or auto-follow. Its first operational use was in t ...
that allowed them to accurately track aircraft at long range. This was part of the LRS.1
fire-control system
A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a ...
that allowed large dual-purpose guns to attack bombers at long range. A contemporary
British Army
The British Army is the principal land warfare force of the United Kingdom, a part of the British Armed Forces along with the Royal Navy and the Royal Air Force. , the British Army comprises 79,380 regular full-time personnel, 4,090 Gurk ...
project at Cossors,
Brakemine Brakemine was an early surface-to-air missile (SAM) development project carried out in the United Kingdom during World War II. Brakemine used a beam riding guidance system developed at A.C. Cossor, while REME designed the testbed airframes. Trial la ...
, was working on a system to allow a missile to keep itself centred within a radar beam, a concept known today as
beam riding
Beam-riding, also known as Line-Of-Sight Beam Riding (LOSBR) or beam guidance, is a technique of directing a missile to its target by means of radar or a laser beam. The name refers to the way the missile flies down the guidance beam, which is ai ...
. The Navy decided to combine the two concepts, using the LRS.1's Type 909 radar with a new missile that differed from Brakemine primarily in requiring longer range and being more robust for shipborne use.
In December 1944, GAP put out a Naval Staff Target for a new anti-aircraft weapon, capable of attacking targets at altitudes up to and speeds of up to . This project was briefly known as LOPGAP, short for "Liquid Oxygen and Petrol Guided Anti-aircraft Projectile", but soon moved from petrol to
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
which made the "LOP" inaccurate.
LOPGAP
The
Fairey Aviation Company
The Fairey Aviation Company Limited was a British aircraft manufacturer of the first half of the 20th century based in Hayes in Middlesex and Heaton Chapel and RAF Ringway in Cheshire. Notable for the design of a number of important military a ...
was at this time working on a missile project for the Ministry of Supply,
Stooge
A stooge or stooges may refer to:
* Straight man (stock character), a comedian who feeds lines to another
* Shill, a confederate or performer who acts as if they're a spectator
* ''The Stooge'', a 1952 American film
* The Three Stooges, a comedy g ...
. Stooge was more like an armed drone aircraft than a missile. It was flown to a location in front of the target and then cruised toward it until its warhead was triggered by the operator. Its low speed and manual guidance meant it was not useful for interceptions outside the immediate area of the ship, and thus did not meet the need for a longer-ranged missile capable of dealing with stand-off weapons. Accordingly, Fairey was ordered to stop work on Stooge in favour of LOPGAP. Development was slowed by the
Air Ministry
The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964. It was under the political authority of the Secretary of State ...
who were opposed to the project as it might take resources away from jet fighter production and a lack of urgency on the part of both the Admiralty and
Ministry of Supply
The Ministry of Supply (MoS) was a department of the UK government formed in 1939 to co-ordinate the supply of equipment to all three British armed forces, headed by the Minister of Supply. A separate ministry, however, was responsible for aircr ...
.
A March 1945 report called for the first test launches of LOPGAP from converted
QF 3.7-inch air-aircraft gun mounts within two months. The same mounts had also been used, with other modifications, for Stooge and Brakemine. They predicted the final system would be about long and a twin-launcher would take up about the same room as a twin 5.25-inch gun turret. An April Staff Target called for the system to be able to engage an aircraft flying at at altitudes up to with a maximum weight of .
Move to RAE
In 1945 a new Guided Projectiles Establishment was set up under the Controller of Supplies (Air) and in 1946 development of all ongoing missile projects moved to the
Royal Aircraft Establishment
The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the Ministry of Defence (United Kingdom), UK Ministry of Defence (MoD), bef ...
's (RAE) new Controlled Weapons Department, soon to become the Guided Weapons Department. They began considering the beam riding concept in partnership with the
Telecommunications Research Establishment
The Telecommunications Research Establishment (TRE) was the main United Kingdom research and development organization for radio navigation, radar, infra-red detection for heat seeking missiles, and related work for the Royal Air Force (RAF) d ...
(TRE), the deliberately oddly-named department of the
Air Ministry
The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964. It was under the political authority of the Secretary of State ...
responsible for
radar
Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...
development. Over the next year, first Brakemine and then Stooge were moved to the RAE.
In a January 1947 Navy review, the program was given the name Seaslug. This called for a significantly larger weapon than initially envisioned, capable of single-stage vertical launch, a warhead (and guidance) of and an all-up weight of . Development continued as before but was significantly hampered by the post-war exodus of engineering talent. Shortly after the new definition was produced, this project also moved to the RAE. Efforts by the Navy to change the name from Seaslug to the more ominous-sounding "Triumph" failed.
Development slowed, and in July 1947 the Admiralty approached
Henry Tizard
Sir Henry Thomas Tizard (23 August 1885 – 9 October 1959) was an English chemist, inventor and Rector of Imperial College, who developed the modern "octane rating" used to classify petrol, helped develop radar in World War II, and led the fir ...
to argue for a more "virile leadership" of the program. Tizard called a meeting of the
Defence Research Policy Committee The Defence Research Policy Committee, or DRPC, was a British Cabinet-level standing committee formed in 1947 that advised and directed military research in the United Kingdom. It was the equivalent of the US's National Defense Research Committee or ...
(DRPC) and started a process of pushing through four key missile programs that were intended to enter service in 1957, Seaslug, a corresponding Army/Air Force missile known as
Red Heathen, the
Blue Boar television guided glide bomb
A glide bomb or stand-off bomb is a standoff weapon with flight control surfaces to give it a flatter, gliding flight path than that of a conventional bomb without such surfaces. This allows it to be released at a distance from the target rat ...
, and the
Red Hawk air-to-air missile
The newest and the oldest member of Rafael's Python family of AAM for comparisons, Python-5 (displayed lower-front) and Shafrir-1 (upper-back)
An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying a ...
.
In March 1948 a new report from the DRPC noted there was not enough manpower for all four projects, and put Seaslug at the bottom of the priority list, claiming air attack would be less likely than submarine in the event of war. They suggested the much longer ranged Red Heathen was more important in the short term. The Admiralty was of another opinion on the matter and argued against the change in priority.
The Navy found an unlikely ally in the Army, who were concerned that Red Heathen was too difficult to move to in a single stage and suggested that Seaslug might be the basis for a more immediate medium-range weapon that could be used both on land and sea. The DPRC also began to have concerns about guiding Red Heathen at its maximum range. In September 1948 they agreed to develop Seaslug "as a matter of insurance", before further upgrading it in 1949 to "top priority". As a result of these changes, the program was seen as having two stages, Stage 1 would deliver missiles in the mid-1950s with roughly range with capability mostly against subsonic targets, and a Stage 2 of the early 1960s would have a greatly extended range on the order of and able to attack supersonic aircraft.
Experimental systems
Two test systems emerged from this centralization. The CTV.1 was a small unpowered Brakemine-like system devoted to the development of the guidance systems, launched using three
RP-3
The RP-3 (from Rocket Projectile 3 inch) was a British air to ground rocket projectile introduced during the Second World War. The "3 inch" designation referred to the nominal diameter of the rocket motor tube. The use of a warhead gave rise to ...
rocket motors and controlled through the coast phase. A series of CTV designs followed, providing ever-increasing amounts of
telemetry
Telemetry is the in situ data collection, collection of measurements or other data at remote points and their automatic data transmission, transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Gr ...
for the guidance and control systems work. GAP became a purely research-oriented system, RTV.1 (rocket test vehicle), as opposed to a prototype missile design, and was used primarily as a platform for testing the rocket motors. The GAP/RTV.1 efforts would be directed at the Stage 1 design, which would essentially be the Seaslug requirement.
The relatively small CTV could safely be launched at the Larkhill Range, part of the
Royal School of Artillery
The Royal School of Artillery (RSA) is the principal training establishment for artillery warfare in the British Army. Established in 1915, it is located at Larkhill, Wiltshire, on the south edge of Salisbury Plain in the United Kingdom. The Schoo ...
. It was equipped with a parachute that allowed it to be recovered. This was not possible for the much longer-ranged RTV, which was fired from
RAF Aberporth
Aberporth is a seaside village, community and electoral ward in Ceredigion, Wales. The population at the 2001 Census, was 2,485, of whom 49 per cent could speak the Welsh language. At the 2011 Census, the population of the community was 2,374 a ...
out over
Cardigan Bay
Cardigan Bay ( cy, Bae Ceredigion) is a large inlet of the Irish Sea, indenting the west coast of Wales between Bardsey Island, Gwynedd in the north, and Strumble Head, Pembrokeshire at its southern end. It is the largest bay in Wales.
Geograp ...
in Wales. The desire to reclaim the RTVs as well led to the opening of a parallel launch facility at the
RAAF Woomera Range Complex
The RAAF Woomera Range Complex (WRC) is a major Australian military and civil aerospace facility and operation located in South Australia, approximately north-west of Adelaide. The WRC is operated by the Royal Australian Air Force (RAAF), a di ...
and a program that led development of supersonic parachutes.
As RTV testing continued, the decision was made to build a larger version, RTV.2, which would be more typical of a production missile. During early testing, the design was further modified and renamed GPV, for General Purpose Test Vehicle. Several
liquid rocket
A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...
motors were tested as part of this program. Early tests demonstrated shifts in the
center of gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weight function, weighted relative position (vector), position of the distributed mass sums to zero. Thi ...
that required active damping, which in turn led to the lengthening of the overall fuselage to become the "long round". This version used forward-mounted boosters, which were mounted so their exhaust was just in front of the mid-mounted wings.
Project 502
As experimental work progressed, the Ministry of Supply began forming an industry team to build production systems. In 1949 this gave rise to the 'Project 502' group from industry, with
Armstrong Whitworth Aircraft
Sir W. G. Armstrong Whitworth Aircraft Company, or Armstrong Whitworth Aircraft, was a British aircraft manufacturer.
History
Armstrong Whitworth Aircraft was established as the Aerial Department of the Sir W. G. Armstrong Whitworth & Company e ...
and
Sperry Sperry may refer to:
Places
In the United States:
*Sperry, Iowa, community in Des Moines County
*Sperry, Missouri
*Sperry, Oklahoma, town in Tulsa County
*Sperry Chalet, historic backcountry chalet, Glacier National Park, Montana
*Sperry Glacier, ...
in March and
GEC in September.
The 29 July 1949 update of the Staff Target called for a maximum range of and a minimum of . Maximum altitude should be 55,000 ft, but 45,000 would be considered acceptable. A later updated pushed the range to against a , later , target. It was assumed the targets would "jink" at 1G, so the missile needed to maneuver at 4G at sea level and 2.5G at 40,000 ft. Additional requirements were the ability to switch between targets in 6 seconds.
The designers ultimately selected a maximum range of 30,000 yards, which included of coasting after motor burn-out. This was about 50% better than the contemporary US
Terrier
Terrier (from Latin ''terra'', 'earth') is a type of dog originally bred to hunt vermin. A terrier is a dog of any one of many breeds or landraces of the terrier type, which are typically small, wiry, game, and fearless. Terrier breeds vary ...
design. Hit probability was estimated to be 40% at maximum range, so salvos of three missiles would be fired at once, demanding a three-place launcher. This was later reduced back to a twin-launcher when it was realized accessing the missile in the middle launcher would make maintenance difficult.
Changing requirements
When the deployment of the Seaslug was first being considered, three classes of custom missile-firing ships were considered. The Task Force Ship would be capable of and would tasked with fleet air defence. The Ocean Convoy Escort was a vessel that would provide direct cover over seagoing convoys, while the Coastal Convoy Escort would do the same closer to shore. At that time it was believed that
aircraft carrier
An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a ...
s would be able to provide adequate cover over convoys or fleets in the ocean, so attention turned to the Coastal Convoy Escort. Beginning in May 1953 a
Beachy Head-class repair ship was converted into a prototype escort ship, , to test this fitting.
For this role, the densest possible storage was required, so the initial design of a single booster rocket at the base end of the missile. This led to a very long design, as was the case for most contemporary designs, this was abandoned in favour of four smaller boosters wrapped around the fuselage, giving shorter overall length of about . The boosters were positioned so they lay within the diameter defined by the missile's wings, so they did not make it any larger in diameter when stored. If one of the boosters did not fire the thrust would be significantly off-axis, a possibility which was later addressed by moving the boosters forward so their exhaust was near the centre of gravity of the missile, allowing the missile's small control surfaces to remain effective. In contrast, the American Terrier missile was somewhat shorter at , but this required an additional tandem booster which took the overall length to .
In 1954, during another review of the Navy's future operations, consideration turned from a "hot war" against the Soviets to a series of "warm wars" in the
third world
The term "Third World" arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada, Japan, South Korea, Western European nations and their allies represented the " First ...
. Among other changes brought about by this review, including the cancellation of a future all-gun cruiser class and ending further conversion of WWII-era destroyers to
Type 15 frigate
The Type 15 frigate was a class of United Kingdom, British anti-submarine warfare, anti-submarine frigates of the Royal Navy. They were conversions based on the hulls of World War II-era destroyers built to the standard War Emergency Programme d ...
s, the new environment meant that air cover by carriers could not be guaranteed, and the need for air defence for task-force sized groups became the primary concern. A cut to carrier construction, capping the fleet at four, released funds for missile ship construction. In October 1954, a new design emerged that demanded the speed to keep up with a fleet in combat, have guns limited to self-defence, and carrying a single twin-missile launcher.
The designs were continually modified in order to find a suitable arrangement. They started as early as 1953 with a mid-sized cruiser of carrying 60 to 90 missiles and a crew of 900. Admiral
Ralph Edwards
Ralph Livingstone Edwards (June 13, 1913DeLong, Thomas A. (1996). ''Radio Stars: An Illustrated Biographical Dictionary of 953 Performers, 1920 through 1960''. McFarland & Company, Inc. . Pp. 86-87. – November 16, 2005) was an American radio ...
pointed out it would be more useful to have a larger number of small ships with 10 to 20 missiles than one larger one, but attempts to design such a ship resulted in one with room for the weapons but not the crew needed to operate them. In May 1955 a wide variety of plans for designs between the two extremes were compared, ranging from 9,850 tons down to 4,550. After continual comparison and revision, these plans finally gelled around what became the
County-class destroyer
The County class was a class of British guided missile destroyers, the first such warships built by the Royal Navy. Designed specifically around the Seaslug anti-aircraft missile system, the primary role of these ships was area air defence aro ...
.
Testing
![Sea Slug missile launch from HMS Girdle Ness (A387) c1961](https://upload.wikimedia.org/wikipedia/commons/6/67/Sea_Slug_missile_launch_from_HMS_Girdle_Ness_%28A387%29_c1961.jpg)
Test firings of the GAP-based examples, now known as Rocket Test Vehicle 1, or RTV.1, demonstrated beam riding in October 1956. The Navy had set a date of 1957 for a broad modernization of the fleet, so they desired Seaslug to be cleared for service in 1956. To this end, they accepted the use of liquid fuels in spite of the Navy's concerns with these fuels on ships. However, by 1956 a new
solid fuel rocket
A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persians ...
had been developed at the
Summerfield Research Station
The Summerfield Research Station is a development and production site for solid rocket motors in the United Kingdom officially formed on 1 September 1951 by the Ministry of Supply. It was set up on the grounds of a former World War II munitions fa ...
which provided the desired range.
Continual tests took place over the next four years using both the
Clausen Rolling Platform
The Clausen Rolling Platform was a missile launching platform, built at the coastal missile test range of RAE Aberporth, West Wales, in the 1950s. It used a floating platform in a pool of water to simulate the rolling of a ship at sea, without t ...
at
RAE Aberporth and the ''Girdle Ness''. A final series of tests at sea, which culminated in sixteen successful firings, finally cleared the missile for service in 1961. After more than 250 launches, the Seaslug Mark 1, also known as Guided Weapon System 1, or GWS.1, finally entered service in 1962 on County-class, each fitted with a single twin missile launcher and a complete weapon system with one fire control set and 30 missiles. The Seaslug-armed cruisers were cancelled in 1957.
Seaslug needed height, range and bearing information for targets. By 1955 the Royal Navy considered using the
Type 984 radar
Type 984 was a Royal Navy radar system introduced in the mid-1950s, designed by the Admiralty Signals and Radar Establishment. Type 984 was a 3D S band system used for both ground controlled interception (GCI) and as a secondary early warning ...
on Seaslug-armed cruisers and destroyers to provide this. During development, the projected weight of the radar doubled, to the point where it could still potentially be mounted on cruisers, but was rejected for destroyers because it would have meant sacrificing their 4.5 in gun armament. The gun armament was regarded as essential for the navy's wider role outside the hot war mission. The solution adopted with the first batch of the County-class destroyers was to network them with ships carrying Type 984. The destroyers were given a reduced version of the
Comprehensive Display System
The Comprehensive Display System (CDS) was a command, control, and coordination system of the British Royal Navy (RN) that worked with the detection/search Type 984 radar. The system was installed on a total of six ships starting in 1957. The US ...
(CDS), which was fed by a
CDS-link receiver called DPD (Digital Picture Transmission or Translation).
The final set for the County ships, actually more a cruiser type than a destroyer, was quite complex: a
Type 965 radar for early warning (P-band, 450 kW peak power, range over 175 km), in the County Batch 2 the double antenna AKE-2 had two different frequency settings; a Type 992Q target indicator radar (3 GHz, 1.75 MW peak power, 90 km range); a Type 278 height finding set (80–90 km); a Type 901 missile guidance radar (X band, 70 km range), that in the Sea Slug Mk 2 had a continuous wave signal (but it was still a beam riding designation radar); a Type 904 fire control radar (used in the MRS-3 system, X-band, 50 kW, 35 km range) for surface targeting.
Description
The missile had four wrap-around booster motors that separated after launch. After separation, the main motor ignited to power the missile to the target. The booster motors were positioned at the side of the missile, but this unusual arrangement with the motor nozzles both angled outwards at 22.5° and 22.5° to the left, 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
The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...
(
Bloodhound
The bloodhound is a large scent hound, originally bred for hunting deer, wild boar and, since the Middle Ages, for tracking people. Believed to be descended from hounds once kept at the Abbey of Saint-Hubert, Belgium, in French it is called, ''l ...
) and the
British Army
The British Army is the principal land warfare force of the United Kingdom, a part of the British Armed Forces along with the Royal Navy and the Royal Air Force. , the British Army comprises 79,380 regular full-time personnel, 4,090 Gurk ...
(
Thunderbird
Thunderbird, thunder bird or thunderbirds may refer to:
* Thunderbird (mythology), a legendary creature in certain North American indigenous peoples' history and culture
* Ford Thunderbird, a car
Birds
* Dromornithidae, extinct flightless birds k ...
) were not required. Once the boosters were jettisoned the control surfaces became active.
Guidance was by radar beam-riding, the beam to be provided by
Type 901 fire-control radar. There were four flight modes:
* LOSBR (Line Of Sight, Beam Riding), in which the missile flew up a beam that tracked the target
* CASWTD (Constant Angle of Sight With Terminal Dive), with the missile climbing at a low angle and then diving onto a low-altitude target at 45°, used against low flying targets at over 12,000 yards away
* MICAWBER (Missile In Constant Altitude While BEam Riding), used against low level target approaching at 500–800 feet, it allows switching from CASWTD to LOSBR when the target is closing at the ship
* Up and over: the standard surface attack mode, using the Type 901 radar slaved to the Type 903 in bearing; the missile is fired at high elevation and then depressed in order to strike the vessel with a steep dive, without arming the fuse.
Electrical power when the missile was in flight was provided by a
flux switching alternator
A flux switching alternator is a form of high-speed alternator, an AC electrical generator, intended for direct drive by a turbine. They are simple in design with the rotor containing no coils or magnets, making them rugged and capable of high rot ...
with a six tooth rotor. "The 1.5 kVA Seaslug generator ran at 24,000 rev/min with a frequency of 2,400 Hz."
Service performance
![HMS Glamorgan (9674967754)](https://upload.wikimedia.org/wikipedia/commons/5/58/HMS_Glamorgan_%289674967754%29.jpg)
Seaslug was a high-performance weapon in the 1960s, with a single-shot kill probability of 92%, although other sources give lower kill probabilities: 75% for the Mk 1 and 65% for the Mk 2. The first four ships of the ''County''-class (Batch 1) operated the Seaslug Mk 1, while the final four (Batch 2) were fitted with the ADAWS command and control system which enabled them to carry the more capable Mk 2 version. A proposal to refit the Batch 1 ships with ADAWS was dropped in 1968.
During the
Falklands War
The Falklands War ( es, link=no, Guerra de las Malvinas) was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British dependent territories in the South Atlantic: the Falkland Islands and its territorial de ...
Seaslug was only launched once against an aircraft target, by , and without success. On 21 May 1982 in
Falkland Sound
The Falkland Sound ( es, Estrecho de San Carlos) is a sea strait in the Falkland Islands. Running southwest-northeast, it separates West and East Falkland.
Name
The sound was named by John Strong in 1690 for Viscount Falkland, the name only l ...
, the ''Antrim'' which had already had an unexploded 1,000 lb bomb pass through the Seaslug magazine, fired a single missile (some sources say two
) at one of a second wave of attacking
IAI Dagger
The Israel Aircraft Industries Nesher (Hebrew: נשר, 'griffon vulture', often mistranslated as 'eagle') was the Israeli version of the French Dassault Mirage 5 multirole fighter.Gupta 1997, p. 105.
Having sustained aircraft losses during the S ...
fighters. It was unguided because the aircraft was too low to be acquired; the launch was intended to deter the pilot and to remove the exposed missile from the ship because it posed a fire hazard. The first combat use in the surface-to-surface role was during a shore bombardment on 26 May, when fired Seaslugs at
Port Stanley Airport
Port Stanley Airport is an airport in the Falkland Islands, outside the capital, Stanley. The airport is the only civilian airport in the islands with a paved runway. However, RAF Mount Pleasant, located to the west of Stanley, functions a ...
claiming the destruction of a number of helicopters and a radar installation.
A total of eight Seaslug Mk 2 missiles were launched in theatre by the two ships armed with them, including two missiles jettisoned by ''Glamorgan'' after she was hit by a land-launched
Exocet missile
The Exocet () is a French-built anti-ship missile whose various versions can be launched from surface vessels, submarines, helicopters and fixed-wing aircraft.
Etymology
The missile's name was given by M. Guillot, then the technical director ...
on 12 June. Also during 1982, the Mk2 was used as a trials target for Seadart, but there were reliability problems with both systems.
The last firing of the Seaslug Mk 1 was in December 1981 by , the final GWS1 (or Batch 1) ship in active service.
was converted to a training ship, and had her Seaslug systems removed, freeing up large spaces for classrooms and was completed in June 1986. ''Fife'' and the remaining GWS2 ships were sold to Chile between 1982 and 1987. Initially, the British government had hoped that the Chileans would accept a package to upgrade the ships to operate Seadart, but this was not taken up and they were transferred complete with Seaslug. The Chilean ships were later refitted with an extended flight deck in place of the Seaslug launcher.
Variants
![Sea Slug trials](https://upload.wikimedia.org/wikipedia/commons/f/fe/Sea_Slug_trials.jpg)
There were two main variants of the Seaslug:
Mark 1 (GWS.1)
The Seaslug Mark 1 was powered by the solid-fuel ''Foxhound'' (390 kg fuel) sustainer motor and ''Gosling''(145 kg) booster motors. It had a radio
proximity fuze
A proximity fuze (or fuse) is a Fuze (munitions), fuze that detonates an Explosive material, explosive device automatically when the distance to the target becomes smaller than a predetermined value. Proximity fuzes are designed for targets such ...
and blast warhead.
The Mark 1 was a
beam rider missile, meaning the target had to be continually illuminated by the directing radar, so the system was limited to engaging only the number of targets that there were radars to track and lock on.
* Attack Velocity:
* Range:
* Ceiling:
Mark 2 (GWS.2)
The Seaslug Mark 2 was based on the aborted
Blue Slug
Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when ob ...
programme to develop an anti-ship missile using the Seaslug missile and guidance system. The project was cancelled in favour of the
"Green Cheese" missile, a tactical nuclear anti-ship weapon, but other project developments were incorporated into what became the Mark 2. It had improved low altitude performance and a limited anti-ship capability and entered service in 1971. The Mark 2 utilized an improved
beam-riding guidance
Beam-riding, also known as Line-Of-Sight Beam Riding (LOSBR) or beam guidance, is a technique of directing a missile to its target by means of radar or a laser beam. The name refers to the way the missile flies down the guidance beam, which is ai ...
system. and solid-state electronics. It was powered by the ''Deerhound'' sustainer motor, with ''Retriever'' boosters. Control was by a modified Type 901M radar and it had an improved infra-red proximity fuze and a
continuous-rod warhead
A continuous-rod warhead is a specialized munition exhibiting an annular blast fragmentation pattern, thus when exploding it spreads into a large circle cutting through target. It is used in anti-aircraft and anti-missile missiles.
Early anti-a ...
with a smaller, , explosive charge (RDX-TNT) and an unfold diameter of about 70 feet (10 mm steel rods were used)
* Attack velocity:
* Range:
* Ceiling:
The capabilities of the new Sea Slug Mk 2, an almost 2.5 ton missile, were much improved compared to the previous Mk 1. The boosters gave a total of about 60 tons-force, with fuel for each one (145 kg in the Mk 1), accelerating it to over Mach 2. When they separated because the extreme drag made by the rings all around the missile, the solid fuel sustainer ''Deerhound'' started to burn its of propellant (390 kg for the Mk 1) and gave about for 38 seconds. The slender missile remained at over Mach 2-2.5 until the flameout. The missile was made fully controllable about ten seconds after firing, followed by a radio-beacon while it was centered in the radar beam; and armed the proxy fuse (infra-red) at about from the target, if 'hot', while if 'cold' the missile was detonated by command sent from the ship.
The range could be even more than 35,000 yards, especially at high altitude, with head-on supersonic targets. One of the longest shots recorded was made by HMS ''Antrim'' against a target over away, with an impact at 34.500 with about 46 seconds flight time. The missile was capable to reach potentially aven higher altitude and longer range than nominally assested: even after the engine flameout (over 40 seconds after launch), it retained very high speeds, and one of them even surpassed before being self-destructed, about one minute after the firing
For both Mark 1 and Mark 2 Sea Slug there were
drill rounds (painted blue) for the purpose of training and display rounds (painted red) which could be loaded onto the launcher for port visits and public relations.
Nuclear variant (not built)
In addition, a
nuclear-armed variant was planned using a low-yield
fission warhead code-named ''Winkle''. ''Winkle'' was never built as it was quickly supplanted by ''Pixie'', a very small
unboosted warhead with an all-plutonium fissile core
tested
''Tested'' is a live album by punk rock band Bad Religion. It was recorded in the USA, Canada, Germany, Estonia, Denmark, Italy and Austria, in 1996, and released in 1997. It is Bad Religion's second live album. Instead of using crowd microphone ...
at
Maralinga
Maralinga, in the remote western areas of South Australia, was the site, measuring about in area, of British nuclear tests in the mid-1950s.
In January 1985 native title was granted to the Maralinga Tjarutja, a southern Pitjantjatjara Aborigi ...
, which was, in turn, replaced by ''Gwen'' — a British version of the US
W54
The W54 (also known as the Mark 54 or B54) was a tactical nuclear warhead developed by the United States in the late 1950s. The weapon is notable for being the smallest nuclear weapon in both weight and yield to have entered US service. It was ...
''Gnat'' unboosted warhead of approximate yield 0.5–2
kiloton
TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a t ...
of TNT-equivalent. The final warhead choice was ''Tony'' - a UK version of the
W44
The RUR-5 ASROC (for "Anti-Submarine Rocket") is 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 ...
''
Tsetse
Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies), are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Glo ...
''
boosted warhead, but all nuclear options for Seaslug were subsequently abandoned, and no nuclear-armed variant of Seaslug was ever deployed.
Operators
Royal Navy
The County-class destroyers were specifically built to carry Seaslug and its associated control equipment. The magazine was positioned amidships and missiles were assembled in a central gallery forward of the magazine before being passed to the launcher on the quarterdeck. The handling arrangements were designed with a nuclear-war environment in mind and were therefore entirely under cover.
Chilean Navy
Some of the County-class destroyers were sold to Chile for the
Chilean Navy
The Chilean Navy ( es, Armada de Chile) is the naval warfare service branch of the Chilean Armed Forces. It is under the Ministry of National Defense. Its headquarters are at Edificio Armada de Chile, Valparaiso.
History
Origins and the Wars ...
. The system was decommissioned after the rebuild of the four ships purchased by Chile in the early 1990s.
Former operators
* :
Chilean Navy
The Chilean Navy ( es, Armada de Chile) is the naval warfare service branch of the Chilean Armed Forces. It is under the Ministry of National Defense. Its headquarters are at Edificio Armada de Chile, Valparaiso.
History
Origins and the Wars ...
* :
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
Notes
References
Bibliography
*
*
*
*
*
Bibliography
* ''Naval Armament'', Doug Richardson, Jane's Publishing, 1981,
External links
Sea Slug Videoa 1958 ''Flight'' article by
Bill Gunston
Bill Gunston (1 March 1927 – 1 June 2013) was a British aviation and military author. He flew with Britain's Royal Air Force from 1945 to 1948, and after pilot training became a flying instructor. He spent most of his adult life doing research ...
"Shell for the Seaslug"a 1959 article on Seaslug in
''Flight'' magazine
"Seaslug Story"a 1962 ''Flight'' article on the Seaslug
*
ttp://www.nuclear-weapons.info/vw.htm#Winkle ''Winkle'' - warhead for the planned nuclear variant
{{UKmissiles
Naval weapons of the United Kingdom
Naval surface-to-air missiles
Surface-to-air missiles of the United Kingdom
Military equipment introduced in the 1960s