page_title: Polaris (UK nuclear programme)
section_title: Design
hierarchical_section_title: Polaris (UK nuclear programme) / Design, development and construction / Design
caption_attribution_description: Honolulu, HI, USA
context_page_description: The United Kingdom's Polaris programme, officially named the British Naval Ballistic Missile System, provided its first submarine-based nuclear weapons system. Polaris was in service from 1968 to 1996.
  Polaris itself was an operational system of four Resolution-class ballistic missile submarines, each armed with 16 Polaris A-3 ballistic missiles. Each missile was able to deliver three ET.317 thermonuclear warheads. This configuration was later upgraded to carry two warheads hardened against the effects of radiation and nuclear electromagnetic pulse, along with a range of decoys.
  The British Polaris programme was announced in December 1962 following the Nassau Agreement between the US and the UK. The Polaris Sales Agreement provided the formal framework for cooperation. Construction of the submarines began in 1964, and the first patrol took place in June 1968. All four boats were operational in December 1969. They were operated by the Royal Navy, and based at Clyde Naval Base on Scotland's west coast, a few miles from Glasgow. At least one submarine was always on patrol to provide a continuous at-sea deterrent.
context_section_description: The first decision required was how many Polaris boats should be built. While the Avro Vulcans to carry Skybolt were already in service, the submarines to carry Polaris were not, and there was no provision in the defence budget for them. Some naval officers feared that their construction would adversely impact the hunter-killer submarine programme. The number of missiles required was the same as the number of Skybolt missiles, which were considered sufficient to devastate forty cities. To achieve this capability, the BNDSG calculated that this would require eight Polaris submarines, each with 16 missiles with one-megaton warheads. It was subsequently  decided to halve the number of missiles, and therefore submarines, based on a decision that the ability to destroy twenty Soviet cities would have nearly as great a deterrent effect as the ability to destroy forty. The Admiralty considered the possibility of hybrid submarines that could operate as hunter-killers while carrying eight Polaris missiles, but McNamara noted that this would be inefficient, as twice as many submarines would need to be on station to maintain the deterrent, and cautioned that the effect of tinkering with the US Navy's 16-missile layout was unpredictable. The Treasury costed a four-boat Polaris fleet at £314 million by 1972–1973. A Cabinet Defence Committee meeting on 23 January 1963 approved the plan for four boats, with the Minister of Defence, Peter Thorneycroft noting that four boats would be cheaper and faster to build than eight.
  A mission led by Sir Solly Zuckerman, the Chief Scientific Adviser to the Ministry of Defence, left for the United States to discuss Polaris on 8 January 1963. It included the Vice Chief of the Naval Staff, Vice Admiral Sir Varyl Begg; the Deputy Secretary of the Admiralty, James Mackay; Rear Admiral Hugh Mackenzie; physicist Sir Robert Cockburn; and F. J. Doggett from the Ministry of Aviation. Its principal finding was that the Americans had developed a new version of the Polaris missile, the A-3. With a range of 2,500 nautical miles (4,600 km), it had a new weapons bay housing three re-entry vehicles (REBs or Re-Entry Bodies in US Navy parlance) and a new 200-kilotonne-of-TNT (840 TJ) W58 warhead expected to become available around 1970. A decision was urgently required on whether to purchase the old A-2 missile or the new A-3, as the A-2 production lines would shut down within two years. The Zuckerman mission came out strongly in favour of the latter, although it was still under development and not expected to enter service until August 1964, as the deterrent would remain credible for much longer. The decision was endorsed by the First Lord of the Admiralty, Lord Carrington, in May 1963, and was officially made by Thorneycroft on 10 June 1963.
  While the Zuckerman mission was in Washington, R. J. Daniel of the Royal Corps of Naval Constructors led a deep technical mission to the United States to study the latest developments in the design of ballistic missile submarines. They met with Rear Admiral Pete Galantin, Raborn's successor as the head of SPO, and executives at the Electric Boat Company, which was building the American Polaris boats. While it was desirable to hew closely to the American design, this would involve retooling the British shipyards and purchasing American equipment. An alternative proposal was to take the incomplete nuclear-powered hunter-killer submarine HMS Valiant, cut it in half, and insert the Polaris missile compartment in its midsection. This was a path that the Americans had taken with the George Washington class in order to build ships as quickly as possible in order to address the missile gap, the purported numerical superiority of the Soviet Union's missile force, which turned out to be illusory.
  Daniel was opposed to this on the grounds that it would unduly disrupt the hunter-killer submarine programme, and it would add more new features to a design that already had enough. The chosen design was suggested by Daniel's superior, Sidney Palmer. The reactor section would be similar to that
caption: A Polaris A-1 missile (left) and a Polaris A-3 missile (right) at the USS Bowfin Submarine Museum in Honolulu, Hawaii
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