The Harpoon surface to surface missile is described by the Royal Navy as;
It is currently only fitted to the Type 23 Frigate although provision has been made on the Type 45 Destroyer.
Harpoon is unlikely to be transferred to the Type 26 or Type 31 Frigates
Development of the Harpoon missile for the US Navy goes back to the mid-sixties as a counter to surfaced submarines but for the Royal Navy, it first came into service as a submarine-launched weapon in the mid-seventies.
The Royal Navy had a requirement for an Under Surface Guided Weapon (UGSW). Choices were a new development from Hawker Siddeley, designated CR137, the McDonnell Douglas Astronautics Harpoon and an Anglo-French development called Sub Martel. Sub Martel was a modification of the already in service Matra Martel air to ground missile but compared to the already in service Harpoon, would require significant development funding.
Although Exocet was in service with both the UK and France, a submarine-launched development project was not considered for UGSW.
In September 1975, the MoD selected the Harpoon missile, the French went on to develop SM39 Exocet, the submarine launched variant. A $6m pre-development contract was awarded to McDonnell Douglas to investigate modifications to enable use by Royal navy submarines. Part of the deal was that British companies would design and develop the torpedo tube launch capsule
Whilst this was ongoing, Norway, the UK, USA, Germany and the Netherlands had embarked upon the Anti-Ship Supersonic Missile study that would eventually go nowhere.
For the next year or so there was a great deal of negotiation on UK subcontract components and other industrial issues. By 1981, the Royal Navy had commenced firing trials of UGM-84B Sub Harpoon from Trafalgar and Swiftsure attack submarines. Sub Harpoon was first deployed on HMS Courageous at the end of the Falklands Conflict in 1982. Also a short time after the conflict, some RAF Nimrod MR.2 aircraft were fitted with air launched Harpoon missiles. A small number were subsequently purchased.
In 1983, McDonnell Douglas offered the 120nm range RGM-84 Harpoon Block 1C for use on the Royal Navy’s Type 22 and Type 23 frigates. Block 1C offered various improvements including increased range (80nm), waypoint navigation and lower altitude flight. The surface-launched storage and launching canister was originally developed for hydrofoil deployment.
In competition with Harpoon was a surface-launched variant of Sea Eagle, the P5T. Sea Eagle was by then entering service with the RAF and Fleet Air Arm. The launch canister for Sea Eagle SL was adapted from a lightweight Sea Dart canister.
Whichever missile won, it was intended to equip the first Type 22 Batch III Frigates. Exocet was not considered suitable and neither was Otomat.
In 1984, Harpoon Block 1C won and a contract for £200 million was placed with McDonnell Douglas, to be designated GWS.60.
Sub Harpoon was withdrawn from Royal Navy service in 2003 with no direct replacement but a surface launched Harpoon Sustainment Programme was initiated to maintain Harpoon to its OSD.
Harpoon equipped Type 22 and now equips Type 23 Frigates. A small number of Type 45 Destroyers have also received the launching system from withdrawn Type 22 Frigates.
Current Out of Service Date (OSD) for Harpoon is planned to be 2018, the In-Service Support contract with Devonport Royal Dockyard Ltd run to November 2018. Like all planned OSD’s though, this may change.
After being launched through a torpedo tube the sub harpoon capsule is activated by the snapping of a safety lanyard. Fins deploy to ensure the capsule assumes a vertical position and it then rises to the surface when the nose and tail caps blow off. The rocket booster ignites and the missile is propelled to a suitable altitude when the main propulsion motor fires.
For the surface-launched variant, currently in service, the missile is fired from an angled tube launcher with frangible front and base caps. The tubes are arranged in groups of four, with two groups arranged to fire port and starboard.
The missile is 4.6m long and weighs 691kg (with booster). The warhead weighs 221kg, approximately the same as a Paveway IV or half the weight of the Storm Shadow warhead. Maximum speed is 885kph.
Guidance for Harpoon is performed initially by information provided by the launch platform, waypoints and mid-course changes can also be programmed into the inertial guidance system. Terminal guidance is carried out using the integral radar seeker. The attack profile is also selectable at launch.
Because of the lack of a data link and the radar terminal guidance feature Royal Navy Harpoon’s are often considered to be obsolete in a contemporary operating environment. Future developments, not currently in service with the Royal Navy, are planned to incorporate improved target discrimination and data links to enable its deployment in complex environments with civilian and military vessels in the same area.