WE.177
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WE.177 was the last air-launched nuclear bomb of the British Armed Forces. There were three versions, all free-fall and parachute-retarded. Two of these versions, WE.177B and WE.177C were thermonuclear weapons. The remaining version, WE.177A was a boosted fission weapon.
The first version to be deployed, the thermonuclear WE.177B, was delivered to the Royal Air Force in September 1966 followed by deliveries of WE.177A to the Royal Navy beginning in 1969,[1] and the RAF in 1971, after a delay caused by the need to produce the ET.317 warhead for the UK Polaris A3T first; and was followed by WE.177C deliveries to the RAF. The Navy weapons were retired by 1992 and all other weapons with the RAF were retired by 1998.[2]
The WE.177A boosted fission weapon, deployed in 1971, was originally conceived as an Improved Kiloton Weapon to replace Red Beard, a tactical kiloton-range bomb. WE.177A was a dual-purpose weapon, being used by RAF and Royal Navy fixed-wing aircraft as a surface attack tactical bomb against land and sea surface targets. It could be delivered by several methods including low-level loft bombing. Forty-three were also deployed aboard Royal Navy surface vessels of frigate size and larger for use by embarked helicopters as an anti-submarine NDB (Nuclear Depth Bomb). WE.177B was originally intended for a strategic role as described below, and WE.177C was added later as a high-yield tactical bomb, also described in more detail below.
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[edit] WE.177A
WE.177A weighed 272kg (600lb), with a selectable yield of 10kT and 0.5kT. This was a boosted fission weapon. The 0.5kT yield was used only in the NDB role for detonation above 130ft (40m) in shallow coastal waters or in oceanic deep waters to limit damage to nearby shipping. The full 10kT yield was used below 130ft (40m) in deep oceanic waters where no shipping was at risk. The full 10kT yield was used by fixed wing aircraft for surface attack. It had airburst, ground burst or laydown options. Although this variant matched the original concept with an added NDB function, and was identified as the 'A' model, it was not the first to be deployed. Development was purposely delayed when the Skybolt ALBM was cancelled. Revised priority was then given to a bomb intended to extend the life (in a strategic role) of the Vulcan force. This stopgap weapon was WE.177B a thermonuclear parachute-retarded free-fall bomb based on a lengthened WE.177A casing, using as a thermonuclear primary the intended warhead for WE.177A. This was known as KATIE in WE.177B. and as KATIE A in WE.177A. Twenty WE.177A bombs were transferred to the RAF from the Royal Navy when the large carriers were decommissioned, and the remaining 43 that were assigned to the Navy's helicopters were retired in 1992. These were also capable of use by Sea Harriers. It was known to the Armed Services as 'Bomb, Aircraft, HE 600lb MC'. In this service jargon MC (Medium Capacity) referred to a nuclear weapon in the kiloton range. The suffix HC High Capacity referred to a weapon in the megaton range, although there were some anomalies.
[edit] WE.177B
WE.177B weighed 431kg (950lb), with a single yield of 450kT This was a thermonuclear bomb, comprising two parts. The primary was KATIE referred to above, but without the variable yield facility or the NDB's hydrostatic fusing. KATIE was based on a British design known as CLEO, earlier known as Super Octopus, intended as the thermonuclear primary for RE.179, a British warhead for the British version of the cancelled Skybolt air-launched ballistic missile. The secondary (or fusion elements) of RE.179 were based on the US W-59 warhead and were known as SIMON. However, the W-59 primary used PBX-9404 and was considered by the British to be unsafe. The United States' W-44 primary was replaced with a British primary developed from CLEO that evolved into KATIE, that did not use the shock-sensitive PBX-9404. When Skybolt was cancelled RE.179 was adapted to become WE.177B (also referred to as Weapon X) and in a smaller form, the British warhead for Polaris. As WE.177B it had airburst, impact, or laydown options. Roughly, 'laydown' can be taken to mean a ground burst with a time delay enabling the bomber to escape the detonation. Numbers built are still uncertain but reliable sources put the figure at 53, and all were retired by August 1998. When Polaris became operational the Vulcan force continued in a tactical role with these and other bombs. With the retirement of the Vulcans, WE.177B was carried by successor aircraft, including Tornado.
[edit] WE.177C
WE.177C weighed 431kg (950lb), with a single yield of 200kT. It was deployed only by RAF Germany in the tactical strike role, and used by Tornadoes and other strike aircraft. It was deployed probably from the early 1980s after deployment of Chevaline had begun. The history of both are intertwined. The primary of the first Polaris warhead (ET.317) was scrapped and not re-used on Chevaline. The secondary, known as REGGIE, was re-used in the Chevaline warhead with a new design of super-hardened primary. However, there were two warheads per Chevaline and three on the original Polaris. The one-in-three spare secondaries were then re-used as the secondaries of WE.177C matched with a 'converted' KATIE A as the primary. The 'conversion' (Ministry of Defence description) probably entailed removal of the variable yield equipment and hydrostatic fusing. This primary and secondary were then installed in a casing identical to the WE.177B casing and ballasted to have similar weight and ballistic properties intended to minimise development time and cost. WE.177C was retired by August 1998. Numbers are speculative but based on hard evidence in declassified files of the number of Polaris ET.317 warheads and spares, a figure of between 48 and 60 is likely.
Type A, B and C weapons were carried by strike aircraft, including the Avro Vulcan, Blackburn Buccaneer, SEPECAT Jaguar, Panavia Tornado, and RAF Harrier. The Royal Navy Sea Harrier carried only WE.177A, slung beneath the starboard wing. At one time, eight Tornado squadrons were nuclear capable.
Two paint-schemes are known to have been used on WE.177:- overall white with orange and green bands (early paint-scheme from the 1960s) and overall green with red details (later paint-scheme from the mid-1970s onwards). Most of the examples of WE.177 training rounds in museums are of the green-painted variety.
All versions of WE.177 had air-burst capability, as evidenced by the white translucent window in the nose of the bomb which housed a radar altimeter.
As with all British thermonuclear weapons, the tritium gas used in the bomb core was purchased from the United States as part of the Anglo-US Barter Agreements that permitted the US to obtain UK weapons-grade plutonium in exchange for enriched uranium, tritium and other specialised material uneconomical to produce in the UK in the very small quantities required. A plant codenamed CANDLE located adjacent to the Chapelcross nuclear power station, near the town of Annan, Scotland, was built to recover tritium from time-expired service weapons returned for servicing. It was then re-cycled after re-lifing. All boosted fission weapons use tritium (which decays with time) gradually reducing the designed fission yield by approx 4.4% per year. Reduction in the fission yield of a primary will reduce the thermonuclear yield by a similar proportion, or even lead to the thermonuclear fusion stage failing to ignite. To maintain optimum yield all versions of WE.177 required servicing at intervals of three years or slightly more. The fully-sealed weapon was not designed to be serviced in-the-field by the user and was the first British-designed weapon to adopt the US practice of returning the weapon to the manufacturer for service.
The safety and arming systems on the WE.177 series (Permissive Action Links) were probably similar to those used on comparable American nuclear weapons eg. B61 since most RAF strike aircraft were also able to deploy US-supplied dual-key nuclear weapons supplied under Project E terms from the 1950s to the early 1990s. Systems would need to be similar or compatible to US systems. The physical safety characteristics of WE.177 were probably comparable eg. using the concept of being 'one-point-safe' [1], plus the ability to activate its thermal batteries and fry the circuitry if it detected unauthorised interference, although there is no hard evidence or published sources that can positively confirm this.
[edit] Further development proposals
There were several proposals to adapt WE.177A for other delivery systems. One was to use the WE.177A NDB as a complete unit, as the standard issue in place of the Mk-44 or Mk.46 homing torpedo carried by the Ikara anti-submarine missile that armed some frigates of the Leander class.[3] Ikara performed a similar function to the U.S. Navy's Asroc missile which could also carry a nuclear warhead. The addition of a nuclear option to Ikara was intended to significantly improve its kill probability, while providing the escort commander with an instant-response, all-weather, all-conditions weapon to deploy against time-urgent targets. Helicopter-delivered NDBs were not always immediately available due to fuel-state, other taskings, or expended weapons load. Recently declassified archives disclose that the Ikara/WE.177A proposal received serious attention for some years, although there is no evidence of actual deployment. Other proposals to re-engineer the WE.177A warhead into two submarine-launched heavyweight torpedoes also received some attention. The Mk.24N Tigerfish nuclear-armed torpedo had approved project status for some years but was eventually shelved. Its raison d'être was to overcome the performance shortcomings of the Tigerfish torpedo, and especially its failure to meet the dive-depth requirements needed to counter deep-diving Soviet SSNs and SSBNs that had outstripped western torpedo performance.[4] There was also a proposal endorsed by Flag Officer Submarines (FOSM), the Royal Navy's professional head of the Submarine Service, to use the WE.177A warhead in another torpedo, the shallow-running unguided Mk.8 torpedo of World War II vintage.[5] A Mk.8 torpedo was chosen to sink the Argentinian warship Belgrano because it was of proven reliability, unlike the unreliable Tigerfish. This proposal did not gain approved project status although its raison d'être was similar to that for Tigerfish, and intended to counter extended delays in Tigerfish development. FOSM's proposal stated that a 10 kt nuclear detonation at the Mk.8 torpedo's running depth of approximately 40 ft (12 m) would destroy a deep-diving SSN at 2,000 ft (610 m) depth.
[edit] Falklands War
During the Falklands war of 1982, some Royal Navy ships were said in newspaper reports to have WE.177A bombs on board as they headed south. Warships and replenishment ships normally deployed with their assigned nuclear weapons during the Cold War. However, all bombs in their floatable containers were stated by the Ministry of Defence to have been off-loaded from the escort vessels HMS Broadsword, HMS Brilliant, HMS Coventry (sunk in action), and HMS Sheffield (sunk in action), for storage in the better-protected deep magazines aboard HMS Hermes, HMS Invincible and the Fleet Replenishment ships RFA Fort Austin and RFA Resource, accompanying the Task Force. HMS Hermes and HMS Invincible then had aboard 40% and 25% respectively of the entire Royal Navy stockpile of WE.177A NDBs[6] and there was concern at their possible loss in action, and at the consequences if a military emergency should develop simultaneously in the NATO area, where these weapons were intended for use. It is not clear if the weapons were removed from deep storage on these vessels, before the Task Force engaged in action around the Falklands Islands, although the MoD assert that these ships did not enter Falklands Islands territorial waters or any other areas subject to the Treaty of Tlatelolco (that established the Latin America Nuclear Weapons Free Zone) that the UK was a signatory to. The MoD assert that the Task Force Commander-in-Chief was given instructions on deployment of his forces to avoid any breach of the treaty. They also state that all the nuclear weapons were returned to the UK aboard RFA Fort Austin and RFA Resource on 29 June and 20 July 1982 respectively, after the end of the Falklands War.[7]
[edit] Retirement
Reliable, recently published sources based upon recent research in declassified files in the National Archives, put eventual total numbers of all versions of WE.177 at between 200-250. All Royal Navy WE.177A weapons were retired in 1992. By August 1998 all RAF stock of all versions, had been withdrawn and dismantled. In the early 1990s the US withdrew all nuclear weapons in Europe that were assigned to British and all other NATO allies. Although RAF aircraft remain nuclear-capable, or could quickly revert to being so, the stocks of weapons no longer exist in Europe, although suitable bombs remain in the US active and inactive stockpiles.
Trident D5 is the UK's sole remaining nuclear weapons delivery system (see Vanguard class submarine), believed armed with a strategic warhead also usable in the sub-strategic role formerly performed by WE.177. Various projects to produce a successor to WE.177 were abandoned.
[edit] Table of WE.177 variants
| Variant | Weight | Est. Yield | Operational |
|---|---|---|---|
| WE.177B | 431 kg | 450 kT | 1966 - 1995 |
| WE.177C | 431 kg | 200 kT | ~1980 - 1998 |
| WE.177A | 272 kg | 10½ kT | 1969 - 1992 |
[edit] References
- Cocroft, W; Thomas, R. Cold War, Building for Nuclear Confrontation 1946-1989, English Heritage, 2003. ISBN 1-873592-69-8, Outdated and accuracy now suspect.
- nuclearweaponarchive.org - Outdated and accuracy now suspect.
- Moore, R; A Glossary of Nuclear Weapons, 'Prospero' Journal of the BROHP Spring 2004, a Visiting Fellow at the University of Southampton.
- [http://www.mcis.soton.ac.uk/Site_Files/pdf/nuclear_history/glossary.pdf
- Site of University of Southampton, Mountbatten Centre for International Studies.
- Various declassified files available at The National Archives, London
[edit] Footnotes
- ^ Public Record Office, London. (PRO) DEFE 24/389 E 42 Annex Appendix 1, June 1969
- ^ WE.177 Free-Fall Bomb Enters Service, AWE timeline
- ^ PRO. AIR 2/13755 and others.
- ^ PRO. DEFE 24/389 E42
- ^ PRO. DEFE 24/389 E42
- ^ PRO. DEFE 32/18 E25.3.e. Handwritten note in red ink in the margin states that "the NDB would be available for issue to approx forty (40) frigates in certain circumstances." (dated March 1969). Using that figure as a benchmark HMS Hermes and HMS Invincible together were likely to have a total of twentysix (26) WE.177A bombs aboard, and the RFA vessels were likely to have more based on MoD statements.
- ^ http://www.mod.uk/NR/rdonlyres/4625B8A4-C533-4DAD-9FA5-0BFEE58F8D69/0/op_corporate1982_nuclear_weapons.pdf
