page_title: Seaslug (missile)
section_title: Testing
hierarchical_section_title: Seaslug (missile) / Development / Testing
caption_attribution_description: Launch of a Sea Slug missile from the Royal Navy missile trials ship HMS Girdle Ness (A387), circa 1961. Girdle Ness was used for missile tests from 1958 to 1961.
context_page_description: Seaslug was a first-generation surface-to-air missile designed by Armstrong Whitworth for use by the Royal Navy. 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 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 destroyers which were designed around the missile system. Seaslug was only fired in anger once as an anti-aircraft missile, from HMS Antrim 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, but this was passed over in favour of a new medium-range system, Sea Dart. Sea Dart entered service in 1973 on the Type 82 destroyers and replaced Seaslug during the 1980s as the County-class destroyers were removed from service.
context_section_description: 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 had been developed by IMI Summerfield which provided the desired range.
  Continual tests took place over the next four years using both the Clausen Rolling Platform 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 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 (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.
caption: Test firing from the trials ship HMS Girdle Ness (A387), circa 1961.
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