UGM-27 Polaris

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Polaris A-3 on launch pad in Cape Canaveral
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Polaris A-3 on launch pad in Cape Canaveral

The Polaris missile was a submarine-launched, two-stage solid-fuel nuclear-armed ballistic missile (SLBM) built during the Cold War by Lockheed for the United States Navy. It was designed to be used as part of the US Navy's contribution to the United States' nuclear deterrent, replacing the Regulus cruise missile. Known as a Fleet Ballistic Missile (FBM), it first flew from Cape Canaveral on January 7, 1960.

Following the Polaris Sales Agreement in 1963 Polaris missiles were also carried on UK submarines between 1968 and the mid 1990s.

Polaris began to be replaced in the US Navy by Poseidon beginning in 1972. In the 1980s both were replaced by Trident I.

Contents

[edit] History and Development

Polaris was originally developed from a plan to create a submarine-based missile force based on a Jupiter missile (see sketch) which was to have been carried horizontally and launched from a surfaced submarine. This is not to be confused with the U.S. Army (later USAF) Jupiter IRBM. At Edward Teller's prompting the Navy plans were abandoned for the much smaller, solid-propellant Polaris.

Originally, the Navy favored cruise missile systems in a strategic role as deployed on the earlier USS Greyback, but a major drawback of those early cruise missile launch systems (and the Jupiter proposals) was that to launch, the submarine would need to surface and remain surfaced for some time. They were very vulnerable to attack during launch, and a fully or partially fuelled missile on deck was a serious hazard to the submarine in that situation. Rough weather was another major drawback for these designs, although rough sea conditions did not unduly affect Polaris launches.

It quickly became apparent that solid-fuelled ballistic missile systems had advantages over cruise missiles in range and accuracy; and unlike both Jupiter and cruise they were able to be launched from a submerged submarine, improving submarine survivability.

The prime contractor for all three versions of Polaris was Lockheed, now Lockheed-Martin.

The Polaris program started development in 1956, with its first flight test in 1958. In 1962, the USS Ethan Allen successfully fired a Polaris A-1 missile equipped with a W-47 nuclear warhead against a test target. The missile entered service onboard the USS George Washington, the first US missile submarine, in 1960. The Polaris A-2 was essentially an upgraded A-1 and entered service in late 1961. The A-2 was fitted on a total of 13 submarines and served until June 1974.(1). Ongoing problems with the W-47 warhead, especially with its mechanical arming and safing equipment led to large numbers being recalled for modifications, and the U.S. Navy sought a replacement that could offer either a larger yield or equivalent destructive power. The result was the W-58 warhead used as a 'cluster' of three for Polaris A-3, the final model. This replaced the earlier A-1 and A-2 in the US Navy and equipped the British Polaris force. The A-3 had a range extended to 2,500 nautical miles (4,630 km) and a new weapon bay housing three Mk 2 re-entry vehicles (ReB or Re-Entry Body in US Navy and British usage); and the new W-58 warhead of 200 kT yield. This arrangement was originally described as a 'cluster warhead' but was replaced with the term Multiple-Re-Entry-Vehicle (MRV). The three warheads were spread about a common target and were not independently targeted. The three 200 kT warheads were stated to be equivalent in destructive power to a single one megaton warhead. Later A-3 missiles (but not the ReBs) were also given limited hardening to protect the missile electronics against electromagnetic pulse effects while in the boost phase. This was known as the A-3T (T for Topsy) and was the final production model.

[edit] Polaris A-1

Polaris A-1 on launch pad in Cape Canaveral
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Polaris A-1 on launch pad in Cape Canaveral

The first version of Polaris, the Polaris A-1, had a range of 1,000 nautical miles (1,853 km) and a single Mk 1 re-entry vehicle, carrying a single W-47-Y1 600 kT nuclear warhead, which was guided by an inertial guidance system which provided an accuracy of 1,800 m CEP. The missile had a length of 28.5 ft (8.69 m), a body diameter of 54 in (1.37 m) and a launch weight of 28,800 lbs (13,090 kg). It used a two-stage solid propellant design.

A test launch from a submarine on July 20, 1960, was the first underwater guided-missile launch. The USS George Washington was the first fleet ballistic missile submarine (SSBN in US naval terminology) and carried 16 missiles. Forty more SSBNs were launched in 1960-66.

Work on its W47 nuclear warhead began in 1957 at the facility now called the Lawrence Livermore National Laboratory by a team headed by Edward Teller and Harold Brown. The Navy accepted delivery of the first 16 warheads in July 1960, and first launched one from a submarine on November 15 1960. On May 6, 1962, a Polaris missile with a live W47 warhead was tested in Operation Dominic I, in the Pacific Ocean the only U.S. test of a live strategic nuclear missile. (Tactical surface-to-air and air-to-air missiles with nuclear warheads were also tested in the atmosphere, usually over the Nevada Test Site.)

The two stages (or boosters) were both steered by thrust vectoring. An inertial navigation system could guide the missile to about a 900 m (3,000 feet) circular error probability. This made them unsuitable for use against hardened targets. They were mostly useful for attacking dispersed military surface targets, eg. airfields, radar sites; thus clearing a pathway for heavy bombers. Non-nuclear cruise missiles were used for similar purposes in both Gulf Wars; although in the general public perception Polaris was a strategic second-strike retaliatory weapon.

[edit] Strategic Role

The Polaris A-1 missile served as a strategic asset. The missile was developed to complement the limited number of medium-range systems deployed throughout Europe. As those systems lacked the range to attack major Russian targets, Polaris was developed to increase the level of nuclear deterrence. At this time there was little threat of counterforce strikes, as few systems had the accuracy to destroy missile systems. The primary advantages of ballistic missile submarines was their ability to launch missiles while submerged, and that offered improved survivability for the submarine while also (like their Regulus predecessors) move shorter ranged systems to within range . The USN had forward-basing arrangements for its Atlantic-based Polaris fleet with both the United Kingdom and Spain permitting the use of bases at the Holy Loch in Scotland and at Rota in the Bay of Cadiz that were much closer to the Polaris submarine's patrol areas, and avoiding the necessity for lengthy transit times from U.S. East Coast bases. This forward-basing arrangement was continued when Poseidon missiles replaced Polaris. The Polaris missile was not accurate enough to destroy hardened targets but would have been effective against dispersed surface targets, eg. airfields, radar and SAM missile sites, as well as military and industrial centers of strategic importance. The military authorities however regarded Polaris as but one of a team of players, each with its own function. The task allotted to Polaris of 'taking-out' or destroying the peripheral defences was well-suited to its characteristics and limitations.

[edit] Later Versions

The later versions (the A-2, A-3, and B-3) were larger, weighed more, and had longer ranges than the A-1. The range increase was most important: The A-2 range was 1,500 nautical miles (2,779 km), the A-3 2,500 nautical miles (4,631 km), and the B-3 2,000 nautical miles (3,705 km). The A-3 featured multiple re-entry vehicles (MRVs) which spread the warheads about a common target, and the B-3 was to have penetration aids to counter Soviet Anti-Ballistic Missile defenses. The B-3 missile evolved into the C-3 Poseidon missile, which abandoned the decoy concept in favour of using the C3's greater throw-weight for larger numbers (10-14) of new hardened high-re-entry-speed reentry vehicles that could overwhelm Soviet defences by sheer weight of numbers, and its high speed after re-entry. The abandoned decoy system for the B-3 (Antelope) was known to the UK where it was adopted and evolved into Super Antelope, KH.793 and later re-labelled Chevaline.

[edit] British Polaris

The British became interested in Polaris after the cancellations of the Blue Streak and Skybolt missiles in the 1950s. Under the Nassau agreement that emerged from the 1962 Nassau Conference between Harold Macmillan and John F. Kennedy, the United States would supply Britain with Polaris missiles, launch tubes, ReBs and the fire control system. Britain would make the warheads and submarines. In return, the British agreed to assign control over missile targeting to SACEUR (Supreme Allied Commander, Europe) with the proviso that in a national emergency when unsupported by NATO allies, the targeting, permission to fire, and use of the missiles would reside with the UK national authorities. Nevertheless, the consent of the British Prime Minister was always required for the use of British nuclear weapons, including Polaris. Confusingly, the operational control of the Polaris submarines was assigned to another NATO Supreme Commander, SACLANT, based at Norfolk, Virginia, although SACLANT routinely delegated control to his deputy commander in the Eastern Atlantic area, COMEASTLANT; always a British admiral. The Polaris Sales Agreement was signed on April 6, 1963.

British Polaris submarines were the Resolution-class ballistic missile submarines. Although one boat of the four was always in refit, recent declassifications of archived files disclose that the Royal Navy deployed four boatloads of RVs and warheads plus spare warheads for Polaris A3T, retaining a limited ability to arm and put to sea the boat that was in refit. When replaced by Chevaline, the deployed RVs/warheads reduced to three boatloads.

The original U.S.Navy Polaris had not been designed to penetrate ABM defences, but the British had to ensure that their small Polaris force operating alone and often with only one submarine on station, could penetrate the ABM screen around Moscow; British strategy being based on a decapitation model. Even before the UK Polaris entered service it was understood that it was vulnerable to the Moscow ABM defence, with intelligence reports stating that a single well-placed ABM detonation could destroy all three warheads from a Polaris A3T missile.

[edit] Chevaline

The UK Polaris was subsequently updated with an 'Improved-Front-End' (IFE) added to replace the unhardened warheads and ReBs of the original in a programme to ensure that the Moscow defences could be penetrated with warheads that were not MIRVed. American strategy was different, being to 'drench' or 'swamp' the defences of 64-100 ABMs with large quantities of MIRVed warheads. With their large stocks of warheads they eschewed decoys or penaids.

The result was a programme called Chevaline that reduced the number of new super-hardened warheads and ReBs to two, and added multiple decoys, chaff, and other defensive countermeasures. Its genesis was in part, a similar programme in the United States called Antelope which the British knew of and adopted, adding other features to become Super Antelope and later KH.793; later relabelled Chevaline. Although Chevaline was designed in Britain it was heavily dependent on U.S. government and industry assistance and approximately half the Chevaline programme costs were spent in the United States.

The Chevaline project was kept secret by four successive British governments, and its existence was only revealed in 1980 by Margaret Thatcher's then defence minister Francis Pym, partly because cost over-runs of the project which had almost quadrupled the original estimate given when the project was finally approved in January 1975. The system became operational in mid-1982 on HMS Renown and the last British SSBN submarines was equipped with it in mid-1987.[1]

Although planning for a successor-system to Chevaline began in 1969, the British rationale for pursuing the expensive Chevaline programme was part-based on the expected lifetime of the submarine hulls. When the decision was taken in January 1975, to opt for Chevaline, the hulls were less than ten years old, with an expected life of thirty years. The improvements to Polaris extended the missile life to almost match the life of the submarines, while meeting the essential requirement of the British military planners; that Chevaline could penetrate the Moscow defences.

The 'unimproved' British Polaris A3T carried three 200kt warheads[2] designated ET.317 in U.S. Mk-2 RVs, comprised of a primary known as Jennie and a thermonuclear secondary known as Reggie.[3] The integrated upgraded Polaris and Chevaline system was known as A3TK and carried two warheads in upgraded British-designed RVs. These warheads used the new Harriet primary[4] with the Reggie thermonuclear secondary re-used from the ET.317 warhead,[5] and their nuclear yield increased to 225kt.[6] This system was deployed from 1982 to 1996, when it was gradually replaced by Trident D5.

[edit] Replacement

The British upgraded to the Trident missile after much political wrangling within the Callaghan Labour government over the cost and necessity. Unusually, after a General Election, and in the interests of national security, the outgoing Prime Minister James Callaghan made his government's papers on Trident available to Margaret Thatcher's incoming Conservative government who promptly took the decision to acquire Trident C4, later upgraded to Trident D5.

A subsequent decision to upgrade to the larger, longer-ranged Trident D5 was probably taken to ensure that there was commonality between the United States Navy and the Royal Navy; which was especially important when they were to use common repair and maintenance facilities at King's Bay, Georgia.

A recurring problem with the British Polaris force had been that it remained in service long after Polaris was retired by the United States Navy; consequently many spare parts and repair facilities in the U.S. ceased to be available. The British had to have production lines re-opened at considerable expense, for example to extend the life of their solid fuel propellant motors. This had been a strongly argued part of the UK naval preference for choosing the Poseidon system as an alternative to the earlier decision to choose Chevaline. In hindsight, Poseidon would have been a cheaper and militarily more effective successor to the original Polaris system than Chevaline, that was chosen after much dissent amongst the military planners, the defence scientific and engineering community, and the defence procurement agencies. Chevaline was not the best military option, a view now acknowledged by senior proponents of it at the time. But it was chosen to keep alive British hopes of retaining a capability to design and build advanced warhead and re-entry vehicle systems that a purchase of Poseidon from the United States would not require. A subsidiary purpose (especially of the Heath government) was to have 'something to bring to the bargaining table' in a hoped for deal to develop an Anglo-French alternative for a Chevaline successor system, although that eventually foundered, and the Thatcher government chose Trident.

Commonality of the Trident D5 missiles means that a missile can be issued by King's Bay to either a British or a U.S. SSBN. Only the warheads, installed later, are different.

See also: Program Evaluation and Review Technique, List of missiles

[edit] References

  1. ^ History of the British Nuclear Arsenal, Nuclear Weapons Archive website
  2. ^ http://www.britannica.com/eb/article-9060595
  3. ^ http://mcis.soton.ac.uk/Site_Files/pdf/nuclear_history/glossary.pdf
  4. ^ http://www.mcis.soton.ac.uk/Site_Files/pdf/nuclear_history/glossary.pdf
  5. ^ Public Record Office, London. DEFE 19/191 E4 Sect 2.3
  6. ^ http://www.mod.uk/NR/rdonlyres/65F3D7AC-4340-4119-93A2-20825848E50E/0/sdr1998_complete.pdf

[edit] External links

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