Sea Wolf (missile)

Sea Wolf is a naval guided missile system designed and built by BAC, later to become British Aerospace (BAe) Dynamics (now MBDA). It is an automated point-defence weapon system designed as a final line of defence against both sea-skimming and high angle anti-ship missiles and aircraft. The Royal Navy has fielded two versions, the GWS-25 Conventionally Launched Sea Wolf (CLSW) and the GWS-26 Vertically Launched Sea Wolf (VLSW) forms.

History


The system was developed by the British Aircraft Corporation (BAC) from a 1964 requirement for a replacement for the Sea Cat missile system to give small warships protection against anti-ship missiles and aircraft. A contract was awarded in 1967 to BAC, Vickers and Bristol Aerojet. Testing lasted from 1970 until 1977, with shipborne trials on a modified Leander class frigate, HMS Penelope (F127), from 1976 onwards. Sea Wolf was tested with a vertical launch system early in the missile's development on a modified Loch class frigate, HMS Loch Fada (K390), but for unclear reasons work did not continue in this direction: the GWS-26 "VL Seawolf (VLS)" being a much later (1980s) development. During trials, the missile performed impressively, successfully intercepting a 114 mm shell on one occasion.

The first deployment, in the GWS-25 form, was on the Type 22 frigate (2 systems) and later on modified Leander class frigates (1 system) in six-round, manually loaded, trainable launchers.

It entered service with the Royal Navy in 1979 and was fired in anger during the Falklands War. Current deployment is the GWS-26 Mod 1 system on Type 23 frigates, fielding 32 vertical launch missiles (VL Sea Wolf) in its missile silo. It is expected to remain in service until 2020.

Description
Sea Wolf is powered by the Blackcap solid-fuel rocket to a maximum velocity of Mach 2, and can intercept targets at ranges between 1000 & and altitudes between 10 &. The warhead weighs 14 kg and is a proximity fused HE-fragmenting type. In the manually loaded form, the missiles are stored on board in individual maintenance-free canisters, sealed until use and handled like a round of ammunition.

Fire control
The system's standard mode is fully automated and uses radar tracking. Target detection is carried out using the parent ship's surveillance radars. Originally, in the Type 22 and Sea Wolf equipped Leander class, this was the radar Type 967 / 968 combination; the D-band Type 967 providing long range surveillance and the E-band Type 968 providing short range target indication. On the Type 23 frigates, these functions have been taken over by the Type 996 3D surveillance radar. Target data is processed by the ship's computers and when the system is live, targets are automatically assigned and engaged without the need for human intervention (although this can be over-ridden by the Missile Director (MD) in the Operations Room).

When a target is to be engaged, the ship's computer slews one of the two Sea Wolf trackers onto the target (there was a single tracker on a Sea Wolf Leander). Originally the Type 910, with an I-band radar, was used but this suffered from poor performance locking onto low-altitude targets hidden in the background sea clutter in the Falklands War. Low-level targets had to be engaged using the 910's secondary TV mode to manually track the target. Subsequently, the lighter Type 911 supplanted the Type 910, adding a second radar (a K-band set based on the Blindfire tracker of the Rapier missile, to control engagements at low level) and was fitted in the 7th Type 22 Frigate onwards. Unlike Type 910, Type 911 does not have any TV function; the TV camera is retained only to allow the Missile Director to visually confirm targets, and to provide a record of engagements.

When lock has been achieved with the missile tracker a round is fired, and is tracked by a pair of radio beacons in the missile's tail. The ship-board system constantly measures the angle differences between the target and the missile and issues the relevant guidance commands to the missile through an Automatic Command to Line of Sight (ACLOS) device transmitting on a microwave link and controlling the rear fins of the missile. It is possible for a single tracker to control a salvo of two missiles.

The radar and CCTV guidance system were developed by Marconi Radar at Great Baddow, Essex.

Combat performance


During the Falklands War, Sea Wolf was the Royal Navy's only modern point-defence weapon. It equipped the Type 22 frigates HMS Brilliant, HMS Broadsword (F88) and the Batch 2 Leander class frigate, HMS Andromeda (F57) which were assigned "goalkeeper" duties, to provide close anti-aircraft defence of the carrier task force. Sea Wolf lived up to expectations and performed well in combat.

In an attempt to overcome the fleet's overall air defence deficiency following the loss of HMS Sheffield (D80), a new tactic was devised, which saw the two Type 22 frigates each teamed with one of the remaining pair of Type 42 destroyers (unofficially termed Type 64, the sum of both classes numbers); these were deployed together some distance from the main fleet, covering likely attack routes, in an attempt to draw attacking aircraft into a "missile trap". On 12 May 1982, Brilliant and HMS Glasgow (D88) were in combination. The ships were attacked by a flight of four Argentine A-4 Skyhawk aircraft. Brilliant was able to shoot down two of these and cause a third to crash trying to avoid the missile. A second wave of aircraft attacked during a failure of the missile system, which led to Glasgow suffering heavy damage. Broadsword however was unable to successfully defend HMS Coventry (D118) when the pair were attacked on 25 May. The latter, moving evasively, crossed in front of Broadsword and broke the Sea Wolf's lock on the attacking aircraft. Sea Wolf also suffered from problems with hardware failure causing launches to fail, and broken lock resulting from the extreme sea conditions and the Argentines' low altitude hit-and-run tactics, and multiple targets and crossing targets - neither of which it was designed to intercept. Sea Wolf accounted for two confirmed "kills" and three further possible successes from eight launches.

Vertical launch (VL) Sea Wolf
Instead of a launcher that is aimed at the target by the fire-control system, VL Sea Wolf uses a vertical launch system (VLS). Missiles are launched vertically by a Cadiz booster motor and turnover pack, to clear the ship's super-structure and rapidly flipped onto their flight path by thrust vector control. The booster motor, which also increases the range of VL Sea Wolf from 6.5 km to 10 km, then separates from the missile, which flies on to engage the target.

Although vertical launch had been explored much earlier in Sea Wolf's development, it was not until the 1980s that a production design was undertaken. VLS went into service, using the GWS-26 system, on the Type 23 frigate HMS Norfolk (F230). Type 23 frigates have a 32-cell VLS, each cell holding one VL Sea Wolf for a total of 32 missiles. The cells, or canisters, are housed vertically in the ship's magazine such that the top of the canisters protrude from the magazine.

Block 2
Block 2 Sea Wolf is a replenishment upgrade to the existing stocks of Sea Wolf missiles. Block 2 missiles have replaced all Sea Wolf missiles, both on Type 22 and Type 23 frigates, as part of normal ammunition replenishment operations. In a parallel programme (Sea Wolf Mid Life Update) the associated Type 911 tracker is being upgraded by the addition of an infra-red camera, enhanced tracking software and new operator's consoles.

GWS-27
Sea Wolf is not a "fire-and-forget" missile; it relies on target data from the parent ship all the way to intercept. A variant with a fire-and-forget capability, GWS-27, was cancelled in 1987.

Lightweight Sea Wolf
Sea Wolf was not designed as a particularly lightweight system, the original GWS-25 variant with Type 910 tracking required 13.5 t of tracking and below decks fire control equipments, reduced to 5 t with the upgraded Type 911 tracker. The "broad-beam" Leander class frigate of 2,500 t (standard displacement) could carry only a single missile system, and required some significant structural "surgery" of the upperworks to counteract the weight of the new missile system. Sea Wolf in its original guise cannot therefore be easily added to existing vessels. For this reason, the Lightweight Sea Wolf variant was designed to use a four-missile launcher, similar in form to that of the obsolete Sea Cat system. It was intended to equip the Royal Navy's Invincible class carriers and Type 42 destroyers to supplement the medium range Sea Dart system, which was not as capable of intercepting sea-skimming missiles. However, it was cancelled before it entered service.

Replacement
At the DSEi conference in September 2007 it was announced the UK MoD was funding a study by MBDA to investigate a replacement for Sea Wolf which is scheduled to leave service about 2018. MBDA was later contracted to replace the Vertical Launch Sea Wolf weapons system on the Royal Navy's Type 23 frigates as part of the Future Local Anti-air Defence System (Maritime) or FLAADS(M). The system chosen is the CAMM which will be known within the Royal Navy as Sea Ceptor. It will enter service on all of the Type 23 frigate from around 2016 onwards and will be migrated in time to the Type 26 global combat ships early in the next decade, providing a Local Area Air Defence capability for the Royal Navy for the next 30 years or so.

The CAMM will share components with the ASRAAM missile in service with the RAF.