Engineering:Sea Dart

Sea Dart
Sea Dart drill missiles on HMS Edinburgh in 2012
Type	Surface-to-air, surface-to-surface
Place of origin	United Kingdom
Service history
In service	1973–2012
Used by	See § Operators
Wars	Falklands War Gulf 1991
Production history
Designer	Hawker Siddeley Dynamics
Designed	1963
Manufacturer	Hawker Siddeley Dynamics (1963–1977) BAe Dynamics (1977–1999) MBDA UK (since 1999)
Produced	1970-2012
No. built	2,000+
Specifications
Mass	550 kg (1,210 lb)
Length	4.4 m (14 ft)
Diameter	0.42 m (17 in)
Warhead	11 kg (24 lb) HE blast-fragmentation
Detonation mechanism	Proximity fuze and contact
Engine	Chow solid-fuel booster motor Bristol Siddeley Odin ramjet cruise motor
Wingspan	0.9 m (3.0 ft)
Operational range	Mod 0 (basic): 40 nmi (46 mi; 74 km) Mod 2 (upgrade): 80 nmi (92 mi; 150 km)
Speed	Mach 3.0+
Guidance system	Semi-active radar illuminated by radar Type 909 (J-band)
Steering system	Control surfaces
Launch platform	Ship

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 Invincible-class aircraft carriers of the Royal Navy. Originally developed by Hawker Siddeley, the missile was built by British Aerospace after 1977. It was withdrawn from service in 2012.

Britain's first naval surface-to-air missile was GWS1 Seaslug, which entered service in 1963. This used beam riding guidance which offered limited accuracy and was useful only against slower targets. The need for a higher performance system was seen even as it entered service.

Bristol Aerospace, which had recently introduced the ramjet-powered Bloodhound missile for the RAF, won the ensuing competition with another ramjet design. Compared to Seaslug, Sea Dart was faster, had much greater range, and its semi-active radar homing guidance was much more accurate and allowed attacks against supersonic targets.

The system had nine confirmed successful engagements in combat, including six aircraft, a helicopter and two anti-ship missiles. An additional helicopter was shot down in a 'friendly fire' incident during the Falklands War.

History

From the immediate post-WWII era, the Royal Navy had been looking for a general-purpose weapon to arm small ships. After the experience with German glide bombs during the war, the primary concern was the development of a medium-range surface-to-air missile able to shoot down the carrier bombers before they could approach the ships. The secondary anti-ship role was later reduced in importance.

Early experiments during the 1950s lead to the development of the Seaslug system. Seaslug was useful against first-generation strike aircraft but had limited performance against faster aircraft or anti-ship missiles. Seaslug was also too large to be carried by a frigate-sized ship, leaving smaller ships with little air defence. Some consideration was given to a high-performance gun system for these ships, the DACR (direct-action, close-range), but calculations showed it would ultimately be useless against future anti-ship missiles that would manoeuvre on the approach.

In October 1960, the Navy launched the Small Ship Integrated Guided Weapon project to fill this need, SIGS for short. This called for a weapon small enough to be carried on a 3,000 ton frigate and able to attack bombers, anti-shipping missiles, and other ships up to frigate size. Seaslug had taken much longer to develop than expected and was a very costly, ongoing program. There was some concern that development of new system should not commence before Seaslug was in service. A review by the Defence Research Policy Committee agreed with the Navy that the new design represented an entirely new class of weapon and that development should be undertaken.

Two systems were considered for the role, Bristol's CF.299 design using a ramjet with a small rocket booster launching it up to speed, and an adaptation of the Army's Sightline project, which would later emerge as Rapier. CF.299 was ultimately chosen. A 1966 report estimated that CF.299 would have a two-shot kill probability (Pk) against an AS-2 Kipper missile of 0.8–0.9, whereas Seaslug II would manage only 0.35–0.55. Against a supersonic "Blinder" bomber, Pk was 0.5–0.8, compared to 0.3–0.5 for Seaslug. Additionally, because it flew faster than Seaslug, the total engagement time was shorter, and this meant the battery could salvo more rapidly. Finally, its ability to lead the target, compared to Seaslug's beam riding pursuit course, allowed it to attack targets with much higher crossing speeds. A 1968 study suggested Sea Dart would have the same capability as eight F-4 Phantoms on patrol.

By this time many foreign navies had chosen the US RIM-24 Tartar surface-to-air missiles, but the Dutch Navy remained interested in the design. They envisioned it being used with a new dedicated air-defence ship, controlled by a significantly more powerful radar, which the British referred to as the Type 988 "Broomstick". This was a 3D radar similar to the US AN/SPY-1 that was under development at the same time. Both the radar and missiles would be controlled by a new combat direction system being developed by both navies.

Ultimately, the Dutch also chose Tartar for their missile component, leaving the Royal Navy as the Sea Dart's only initial user. Sea Dart entered service in 1973 on the sole Type 82 destroyer HMS Bristol before widespread deployment on the Type 42 destroyer commencing with HMS Sheffield in 1976. The missile system was also fitted to Invincible-class aircraft carriers but was removed during refits between 1998 and 2000 to increase the area of the flight deck and below-decks stowage associated with the operation of Royal Air Force Harrier GR9 aircraft.

In 1982, Margaret Thatcher was involved in a £100m deal to sell the Sea Dart system to China , but this fell through in 1983, with Chinese minister Chen Muhua explaining that China was "not satisfied with the price, technology or production".

Design

Sea Dart missile illustration. The Chow booster is on the extreme right. The four small receiver antennas for the semi-active radar homing are visible on the left. The antennas are arranged to provide phase-comparison to improve accuracy.

Pink ramjet air intake

Sea Dart is a two-stage, 4.4-metre (14 ft) long missile weighing 550 kilograms (1,210 lb). It is launched using a drop-off Chow solid-fuel booster that accelerates it to the supersonic speed necessary for the operation of the cruise motor, a Rolls-Royce /Bristol Siddeley kerosene-fuelled Odin ramjet. This gives a cruise speed of over Mach 2.5, and unlike many rocket-powered designs, the cruise engine burns for the entire flight, giving excellent terminal manoeuvrability at extreme range.

It is capable of engaging targets out to at least 30 nautical miles (35 mi; 56 km) over a wide range of altitudes. It has a secondary capability against small surface vessels, tested against a Brave-class patrol boat, although in surface mode the warhead safety arming unit does not arm, and thus damage inflicted is restricted to the physical impact of the half-ton missile body and the unspent proportion of the 46 litres (10 imp gal; 12 US gal) of kerosene fuel.

Guidance is by proportional navigation and a semi-active radar homing system using the nose intake cone and four aerials around the intake as an interferometer aerial, with targets being identified by a Type 1022 surveillance radar (originally radar Type 965) and illuminated by one of a pair of radar Type 909. This allows two targets to be engaged simultaneously in initial versions, with later variants able to engage more. Firing is from a twin-arm trainable launcher that is loaded automatically from below decks. The original launcher seen on HMS Bristol was significantly larger than that which appeared on Type 42 and Invincible classes. Initial difficulties with launcher reliability were resolved.

Combat service

Falklands War

Sea Dart on Cardiff in 1982 (taken after the Falklands War had ended)

Sea Dart was used during the Falklands War (1982) and is credited with seven confirmed kills (plus one British Aérospatiale Gazelle helicopter downed by friendly fire). Kills were made against a high-flying aircraft beyond the missile's stated technical envelope and low-flying attack aircraft.

The net effect of Sea Dart was to deny the higher altitudes to enemy aircraft. This was important because Argentine aircraft such as the Mirage III had better straight line performance than the Sea Harriers, which were unlikely to successfully intercept them.

The first Sea Dart engagement was against an Aérospatiale Puma, on 9 May 1982 near Stanley by HMS Coventry, with the loss of the three men aboard.

On 25 May 1982 an A-4C Skyhawk of Grupo 5 was shot down north of Pebble Island, again by Coventry. The pilot, Capitán Hugo Angel del Valle Palaver, was killed. Later, Coventry shot down another Skyhawk of Grupo 4 while it was returning from a mission to San Carlos Water. Capitán Jorge Osvaldo García successfully ejected but was not recovered. The next Argentine action that day sank Coventry. An unguided Sea Dart was launched in an effort to disrupt the attack but missed, and the destroyer was struck by two iron bombs and sank.

The same day a Super Étendard strike fighter sought to attack the British carrier group with Exocet missiles, but instead struck the cargo ship MV Atlantic Conveyor. Invincible fired six Sea Darts in less than two minutes, but all missed.

Canberra bomber B-108 of Grupo de Bombardeo 2. This Argentine aircraft was shot down by a Sea Dart on 13 June 1982.

On 30 May 1982, during the last Exocet air attacks against the British fleet, HMS Exeter shot down two Skyhawks (out of four), despite their flying only 10–15 metres (33–49 ft) above the sea (theoretically below Sea Dart's minimum engagement altitude of 30 metres (98 ft)). On 6 June Exeter shot down a Learjet 35A being used for reconnaissance at 12,000 metres (39,000 ft).

On 6 June 1982, Cardiff fired a Sea Dart missile at an aircraft believed to be an Argentine C-130 Hercules. The missile destroyed the aircraft, which was in fact a British Army helicopter. All four occupants were killed in this "friendly-fire" incident.

Finally, on 13 June 1982, an English Electric Canberra flying at 12,000 metres (39,000 ft) en route to bomb British troops near Port Harriet House was destroyed by a Sea Dart fired from Cardiff.

Sea Dart on Invincible

In total at least eighteen missiles were launched by Type 42 destroyers, six by Invincible, and two by Bristol. Out of five missiles fired against helicopters or high flying aircraft, four were successful, but only two of nineteen fired at low level aircraft hit: just eleven per cent; however a number of missiles were fired without guidance to deter low level attacks. Exeter's success can be partially attributed to being equipped with the Type 1022 radar, which was designed for the system and provided greater capability than the old Type 965 fitted to the earlier Type 42s. The Type 965 was unable to cope with low level targets as it suffered multiple path crossings and targets became lost in radar clutter from the surface of the South Atlantic. This resulted in Sea Dart being unable to lock onto targets at distance obscured by land, or fast-moving low-level targets obscured in ground clutter or sea-returns.

The Argentine Navy was well aware of the Sea Dart's capabilities and limitations, having two Type 42s of its own. Consequently, Argentine planes, opting to fly below the Type 965 radar ("sea skimming"), frequently dropped bombs which failed to explode. The arming vane on the bomb had insufficient time to complete the number of revolutions required to arm the fuze.

Persian Gulf War (1991)

In February 1991 during the Persian Gulf War the battleship USS Missouri was operating in the Persian Gulf. Her battlegroup included a number of escorts, including the Type 42 destroyer HMS Gloucester. On 24 February, Missouri was fired on by a pair of Silkworm anti-ship missiles. Although one missed completely, the other was engaged and destroyed by a Sea Dart fired by HMS Gloucester after it had flown over the target, while another of the battleship's escorts, the frigate USS Jarrett, attempted to engage with its Phalanx CIWS, but succeeded only in firing at the chaff launched by Missouri.

Variants

The Sea Dart was upgraded over the years - notably its electronics - as technology advanced. The following modification standards have been fielded:

Mod 0

Basic 1960s version, used in the Falklands. valve technology. Range circa 40 nmi (46 mi; 74 km).

Mod 1

Improved Sea Dart. Upgraded version 1983–1986. Updated guidance systems possibly allowing some capability against sea-skimming targets and much greater reliability.

Mod 2

1989–1991. Upgrade included ADIMP (Air Defence IMProvement) which saw the replacement of six old circuit cards in the guidance system with one, allowing the spare volume to be used for an autopilot. Used alongside a command datalink (sited on the Type 909 pedestal) it allows several missiles to be 'in the air' at once, re-targeted during flight etc. and allows an initial ballistic trajectory, doubling range to 80 nmi (92 mi; 150 km) with the upgraded 909(I) radar for terminal illumination only.

Mod 3

Latest version with new infrared fuze. Delayed eight years from 1994 to 2002.

The Sea Dart Mark 2, GWS 31, (also known as Sea Dart II - not to be confused with Mod 2, above) development was cancelled in 1981. This was intended to allow 'off the rail' manoeuvres with additional controls added to the booster. The Mark 2 was reduced to Advanced Sea Dart, then Enhanced Sea Dart and finally Improved Sea Dart.

Lightweight Sea Dart was a version with minimal changes to the missile itself, but based in a new sealed box-launcher. A four-box trainable launcher was developed that allowed it to be mounted to ships as small as 300 tons displacement. The same box and launcher could also support the Sea Eagle SL, the proposed ship-launched version of Sea Eagle. Guardian was a proposed land-based system of radars, control stations and the Lightweight Sea Dart proposed in the 1980s for use as a land-based air defence system for the Falkland Islands. Neither system was put into production.

Withdrawal

HMS Edinburgh conducting the final Sea Dart missile firing at the north western Scottish range of Benbecula. The ship fired five missiles, three single missiles and a two-missile salvo at an unmanned drone target.

The Sea Dart-equipped Type 42s reached the end of their service lives, with all vessels already retired. They were replaced by the larger Type 45 which are armed with the Sea Viper missile system which is much more capable in the anti-air role. The first-of-class began sea trials in July 2007 and Daring entered service in 2009.

On 13 April 2012 HMS Edinburgh fired the last operational Sea Dart missiles after a thirty-year career. The last two remaining Type 42s, York and Edinburgh completed their careers without the system being operational.

A launcher with drill missiles has been preserved and is on display at Explosion! Museum of Naval Firepower, Gosport, Hampshire.

Operators

Map with former Sea Dart operators in red

Former operators

Argentina

• Argentine Navy: Purchased 60 missiles for their two Type 42 destroyers but retired them in 1987 due to lack of spares.

United Kingdom

• Royal Navy

References

Bibliography

• Friedman, Norman (2012). British Destroyers & Frigates: The Second World War & After. Seaforth Publishing. ISBN 9781848320154. https://books.google.com/books?id=5LLgAwAAQBAJ. 
• Britain's Modern Royal Navy, Paul Beaver, Patrick Stephens Limited, 1996 ISBN:1-85260-442-5
• Naval Armament, Doug Richardson, Jane's Publishing, 1981, ISBN:0-531-03738-X
• War Machines enciclopedy, Limited publishing, 1984 page 866 (Italian version printed by De Agostini) and page 1260-1268
• Enciclopedy War Machines, 1265–70 and 864-65 (Italian edition)