UK Polaris programme

The United Kingdom's Polaris programme provided the first submarine-based British nuclear weapons system.

"Polaris" itself was an operational system of four Resolution-class submarines, each armed with 16 UGM-27 Polaris A-3 ballistic missiles, with each missile able to deliver three ET.317 thermonuclear warheads around a single target. This configuration was later upgraded to carry two hardened warheads along with a range of decoys.

Operated by the Royal Navy and based at Clyde Naval Base on Scotland's west coast, at least one submarine was always on patrol to provide a continuous at-sea deterrent.

The British Polaris programme was announced in December 1962 following the Nassau Agreement between the US and the UK. Construction of the submarines began in 1964, and the first patrol took place in June 1968.

In the 1970s it was determined that the re-entry vehicles were vulnerable to a Soviet anti-ballistic missile screen concentrated around Moscow. To ensure that a credible and independent nuclear deterrent was maintained, the UK developed an improved front-end named Chevaline. There was huge controversy when this project became public knowledge in 1980, as it had been kept secret by four successive governments while incurring huge expenditure.

Polaris patrols continued until May 1996, by which time the phased handover to the replacement Trident system had been completed.

History
The Royal Navy began seeking a role in the United Kingdom's nuclear weapons program after World War II. In 1948 it proposed carrier-based aircraft for nuclear weapons delivery, although bombs small enough to be carried on such craft did not yet exist. Its "carriers versus bombers" debate with the Royal Air Force for funding and support resembled the similar interservice dispute in the United States at this time that led to the "Revolt of the Admirals". In 1956 Britain began participating in United States Navy admiral Hyman Rickover's nuclear navy program, including both nuclear marine propulsion and the development of a solid-fuel submarine rocket. During the 1950s and early 1960s, Britain's nuclear deterrent was based around the Air Force's V-bombers. But in the early 1960s developments in radar and surface-to-air missiles made it clear that bombers were becoming vulnerable, and would be unlikely to penetrate Soviet airspace. Free-fall nuclear weapons would no longer be a credible deterrent.

To address this problem, in May 1960 the British Prime Minister, Harold Macmillan arranged with US President Eisenhower to equip the V-bombers with the US-designed GAM-87 Skybolt. Skybolt was a 1000 mi range ballistic missile that allowed the launching bombers to remain well away from Soviet defences, and launch attacks that would be difficult or impossible to stop. With this range, the V bombers would have to fly only a few hundred miles from their bases before being in range for an attack on Moscow.

Under the agreement the UK's contribution to the program was limited to developing suitable mounting points on the Avro Vulcan bomber, installing the required guidance systems that fed the missiles updated positioning information, and development of their own version of the US W47 warhead to arm it, the RE.179.

The subsequent Kennedy administration expressed serious doubts of both Skybolt and the US deterrent force in general. Robert McNamara was highly critical of the US bomber fleet, which he saw as obsolete in an age of Intercontinental ballistic missiles. McNamara was equally concerned about the UK retaining an independent nuclear force, and worried that the US could be drawn into a war by the UK, or that the Soviets could use the UK as a proxy hostage. He wanted to bring the UK into a dual-key arrangement.

McNamara first broached the idea of cancelling Skybolt with the British in November 1962. When this was reported in the House of Commons, a storm of protest broke out. At a conference in the Caribbean, Macmillan insisted that the UK would be retaining an independent deterrent capability, no matter what the cost of developing an independent launch platform. Kennedy backed down and abandoned his attempts to persuade the UK to accept a dual-key arrangement. The two leaders concluded the Nassau Agreement which would see the purchase of US missiles to serve aboard UK-built submarines. This statement was later formalised as the Polaris Sales Agreement, which is still in force today having been extended to cover the Trident programme.

Design, development and construction
The opportunity to purchase state-of-the-art American technology at a moderate cost was so remarkable that British officials refused to believe the offer had been made, and a scholar later described it as "amazing". What the Defence Council later described as "special measures" were used to ensure that the Polaris system could be operational in just six years, and by purchasing a proven system the Polaris' actual cost was very close to the estimate made at the signing of the Nassau Agreement. The Resolution-class submarines would be designed and built in the UK, with the Polaris A-3 missiles bought from the United States. The warheads were designed and assembled at the British Atomic Weapons Establishment using some elements of US warhead design. Maintenance and other shore facilities were constructed in Scotland.

Resolution-class submarines
Two pairs of the boats were ordered in May 1963 from Vickers Shipbuilding Ltd, Barrow in Furness and from Cammell Laird and Co. Ltd, Birkenhead. The option of buying a fifth unit, planned as Ramillies, was cancelled in February 1965. Traditional battleship names were used, signifying that they were the capital ships of their time.

Vickers Armstrong in Barrow-in-Furness constructed Resolution and Repulse and Cammell Laird in Birkenhead constructed Renown and Revenge. The construction was unusual in that the bow and stern were constructed separately before being assembled together with the American-designed missile compartment.

The design was a modification of the Valiant-class fleet submarine, but greatly extended to incorporate the missile compartment between the fin and the nuclear reactor. The length was 130 metres, breadth 10.1 metres, height 9 metres and the displacement 8400 LT submerged and 7600 LT surfaced. A Rolls-Royce pressurised water reactor and English Electric Company turbines gave them a speed of 25 kn and they could dive to depths of 275 m. Sixteen Polaris A3 missiles were carried, in two rows of eight. For emergencies there was a diesel generator and six 21-inch (533 mm) torpedo tubes located at the bow, firing the Tigerfish wire-guided homing torpedoes. The submarines put to sea with a crew of 143.

The first boat was laid down in February 1964, and the submarines had all been completed by December 1969.

UGM-27 Polaris missile


The Polaris missile was a two-stage solid-fuel nuclear-armed submarine-launched ballistic missile (SLBM) built by Lockheed Corporation of California (now Lockheed Martin). Its original user was the United States Navy. It was designed to be used as part of the Navy's contribution to the United States arsenal of nuclear weapons, replacing the SSM-N-8 Regulus cruise missile. Polaris was first launched from the Cape Canaveral, Florida, missile test base on January 7, 1960.

The version used by the Royal Navy was the third iteration, the A-3. The United Kingdom contributed 8% of research and development costs, and denied speculation that the Nassau Agreement permitted the addition of electronic mechanisms in the missile to give the United States a veto over its use. The missile replaced the earlier A-1 and A-2 models in the US Navy. The A-3 had a range extended to 2,500 nautical miles (4,630 km) and a new weapon bay housing three re-entry vehicles. 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 (such as a MIRV missile is). The three warheads were stated to be equivalent in destructive power to a single one-megaton warhead.

The Polaris missile was gradually replaced in the US Navy by the Poseidon missile, beginning in 1972, and then the Trident I missile in the 1980s.

ET.317 warhead
The warhead used on US Polaris A-3 missiles was the US W-58. Britain considered but never used the W-58 because the British safety authorities considered it unsafe in several respects. Instead they fitted a hybrid of a US W-59 fusion secondary, triggered by a new British primary based on a Cleo fission device tested in Nevada as PAMPAS and TENDRAC. Variants of this basic design were used or intended for several other delivery systems, including WE.177 range of free-fall bombs, GAM-87 Skybolt in British service, and the Blue Water battlefield nuclear missile.

Operations
In a 1996 speech to mark the retirement of the last Polaris submarine, John Major said that: "Each has made its own unique and invaluable contribution to the remarkable record of maintaining a Polaris submarine at sea, on deterrent patrol, undetected by friend or foe, every day, of every year, from 1969 until May this year."

Upgrades
The original U.S. Navy Polaris had not been designed to penetrate Anti-ballistic missile (ABM) defenses, but the Royal Navy had to ensure that its small Polaris force operating alone, and often with only one submarine on deterrent patrol, could penetrate the ABM screen around Moscow. The result was a programme called Chevaline that added multiple decoys, chaff, and other defensive countermeasures. Its existence was only revealed in 1980, partly because of the cost overruns 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 Resolution-class submarine was equipped with it in mid-1987.

Replacement
In 1980 the British government announced its intention to replace Polaris with a new independent nuclear deterrent, and formally sought permission to acquire the Trident I C-4 missile then in service with the US Navy.

Following the acceleration of the US UGM-133 Trident II D-5 programme, the Polaris Sales Agreement was modified in 1982 to permit the supply of the more advanced missiles. Under the agreement, the UK would lease 65 Trident II D-5 missiles from a larger pool of such weapons based at Naval Submarine Base Kings Bay in the United States. Like Polaris, the UK would manufacture its own warheads and Vanguard-class submarines in Britain, but unlike Polaris the US would retain full responsibility for the maintenance of the missiles.

The first Trident patrol took place in December 1994, and Trident had entirely replaced Polaris by December 1996.