Operation Grapple
Operation Grapple was a set of four series of British nuclear weapons tests of early atomic bombs and hydrogen bombs carried out in 1957 and 1958 at Malden Island and Kiritimati in the Gilbert and Ellice Islands in the Pacific Ocean as part of the British hydrogen bomb programme. Nine nuclear explosions were initiated, culminating in the United Kingdom becoming the third recognised possessor of thermonuclear weapons, and the restoration of the nuclear Special Relationship with the United States in the form of the 1958 US–UK Mutual Defence Agreement.
During the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys, which was merged with the American Manhattan Project in August 1943. Many of Britain's top scientists participated in the Manhattan Project. After the war, fearing that Britain would lose its great power status, the British government resumed the atomic bomb development effort, now codenamed High Explosive Research.
The successful test of an atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement, but Britain was still several years behind the United States, which had developed the more powerful thermonuclear weapons in the meantime. In July 1954, the Cabinet agreed that the maintenance of great power status required that Britain also develop thermonuclear weapons.
The United Kingdom Atomic Energy Authority Atomic Weapons Research Establishment at Aldermaston produced three designs: Orange Herald, a large boosted fission weapon; Green Bamboo, an interim thermonuclear design; and Green Granite, a true thermonuclear weapon. The new designs had to be tested to demonstrate that they worked, hence Operation Grapple. The first series consisted of three tests in May and June 1957. In the first test, Grapple 1, a version of Green Granite known as Short Granite was dropped from a Vickers Valiant bomber flown by Wing Commander Kenneth Hubbard. The bomb's yield was estimated at, far below its designed capability. Despite this, the test was hailed as a successful thermonuclear explosion, and the government did not confirm or deny reports that the UK had become a third thermonuclear power. The second test, Grapple 2, was of Orange Herald; its yield made it technically a megaton-range weapon, and the largest ever achieved by a single stage nuclear device. Grapple 3 tested Purple Granite, a version of Short Granite with some fixes; its yield was only.
A second test series was required, which consisted of a single test, Grapple X, in November 1957. This time the yield of exceeded expectations. It was a true hydrogen bomb, but most of its yield came from nuclear fission rather than nuclear fusion. In a third series with a single test, Grapple Y, in April 1958, another design was trialled. With an explosive yield of about, it remains the largest British nuclear weapon ever tested. The design of Grapple Y was notably successful because much of its yield came from its thermonuclear fusion reaction instead of fission of a heavy uranium-238 tamper—the dense material surrounding the core that kept the reacting mass together to increase its efficiency. Its yield had been closely predicted, indicating that its designers understood the process. A final series of four tests in August and September 1958, known as Grapple Z, tested techniques for boosting and making bombs immune to predetonation caused by nearby nuclear explosions. Two of these tests were detonations from balloons. A moratorium on testing came into effect in October 1958, and Britain never resumed atmospheric nuclear testing.
Background
During the early part of the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys. At the Quebec Conference in August 1943, Prime Minister Winston Churchill and US President Franklin Roosevelt signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The September 1944 Hyde Park Aide-Mémoire extended both commercial and military cooperation into the post-war period. Many of Britain's top scientists participated in the Manhattan Project.The British government had trusted that America would continue to share nuclear technology, which it considered to be a joint discovery. On 16 November 1945, Churchill and Roosevelt's successors, Clement Attlee and Harry S. Truman, signed a new agreement that replaced the Quebec Agreement's requirement for "mutual consent" before using nuclear weapons with one for "prior consultation", and there was to be "full and effective cooperation in the field of atomic energy", but this was only "in the field of basic scientific research". The United States Atomic Energy Act of 1946 ended technical cooperation. The revelation of a Canadian spy ring that included British physicist Alan Nunn May while the bill was being prepared caused the United States Congress to add the death penalty for sharing "restricted data" with foreign nations. Efforts to restore the nuclear Special Relationship with the United States over the following decade were dogged by repeated spy scandals, including the arrest of Klaus Fuchs in 1950, and the defection of Guy Burgess and Donald Maclean in 1951. Fearing a resurgence of American isolationism and Britain losing its great power status, the British government restarted its own development effort, now codenamed High Explosive Research.
The successful test of an atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement. Britain became the world's third nuclear power, reaffirming the country's status as a great power, but hopes that the United States would be sufficiently impressed to restore the Special Relationship were soon dashed. In November 1952, the United States conducted Ivy Mike, the first successful test of a true thermonuclear device or hydrogen bomb, a far more powerful form of nuclear weapons. Britain was therefore still several years behind in nuclear weapons technology. The Defence Policy Committee, chaired by Churchill and consisting of the senior Cabinet members, considered the political and strategic implications in June 1954, and concluded that "we must maintain and strengthen our position as a world power so that Her Majesty's Government can exercise a powerful influence in the counsels of the world." A Cabinet meeting on 27 July accepted this argument, and directed the Lord President to proceed with the development of thermonuclear weapons.
The United Kingdom Atomic Energy Authority Atomic Weapons Research Establishment at Aldermaston in Berkshire was directed by William Penney, with William Cook as his deputy. The scientists at Aldermaston did not know how to build a hydrogen bomb, but produced three megaton-range designs that were named under the Rainbow code system: Orange Herald, a large nuclear fission weapon with an enriched uranium tamper; Green Bamboo, an interim thermonuclear design in which fusion occurred in layers of lithium-6 deuteride that alternated with layers of uranium-235; and Green Granite, a true thermonuclear design in which the majority of the yield came from thermonuclear burning. The British bomb designers used the terms "Tom" and "Dick" for the bomb's primary and secondary stages respectively. The Tom would be a fission bomb. It would produce radiation to implode the Dick. Implicit in the creation of a hydrogen bomb was that it would be tested. Anthony Eden, who replaced Churchill as prime minister after the latter's retirement on 5 April 1955, gave a radio broadcast in which he declared: "You cannot prove a bomb until it has exploded. Nobody can know whether it is effective or not until it has been tested."
Location
Preliminary testing of boosted fission weapons, in which the fission yield was increased through the addition of lithium-6 deuteride, was carried out in the Operation Mosaic tests in the Montebello Islands in May and June 1956. Orange Herald would also incorporate boosting. This was a sensitive matter; there was an agreement with Australia that no thermonuclear testing would be carried out there. The Australian Minister for Supply, Howard Beale, responding to rumours reported in the newspapers, asserted that "the Federal Government has no intention of allowing any hydrogen bomb tests to take place in Australia. Nor has it any intention of allowing any experiments connected with hydrogen bomb tests to take place here." Although the devices tested in Mosaic were not thermonuclear, the tests were connected with hydrogen bomb development, so this prompted Eden to cable the Prime Minister of Australia, Robert Menzies, detailing the nature and purpose of the tests. Eden promised that the yield of the second, larger test would not exceed two and a half times that of the Operation Hurricane test, which was. This was slightly higher than the limit previously agreed on tests in Australia. Menzies cabled his approval of the tests on 20 June 1955. In the event, the yield of the second test was.Another test site was therefore required. For safety and security reasons, in the light of the Lucky Dragon incident, in which the crew of a Japanese fishing boat were exposed to radioactive fallout from the American Castle Bravo nuclear test, a large site remote from population centres was required. Various islands in the South Pacific and Southern Oceans were considered, along with Antarctica. The Admiralty suggested the Antipodes Islands, which are about southeast of New Zealand. In May 1955, the Minister for Defence, Selwyn Lloyd, concluded that the Kermadec Islands, which lie about northeast of New Zealand, would be suitable.
The Kermadec Islands were part of New Zealand, so Eden wrote to the Prime Minister of New Zealand, Sidney Holland, to ask for permission to use the islands. Holland refused, fearing an adverse public reaction in the upcoming 1957 general election in New Zealand. Despite reassurances and pressure from the British government, Holland remained firm. The search for a location continued, with Malden Island and McKean Island being considered. These were uninhabited islands claimed by both Britain and the United States. The former island became the frontrunner. Three Avro Shackletons from No. 240 Squadron were sent to conduct an aerial reconnaissance from Canton Island. It too was claimed by both the United States and Britain, and was jointly administered, so the Americans had to be informed. Holland agreed to send the survey ship to conduct a maritime survey.
Kiritimati was chosen as a base. It too was claimed by both Britain and the United States. Lying just north of the equator, it was a tropical island, largely covered in grass, scrub and coconut plantations. Temperatures were high, averaging during the day and at night, and humidity was very high, usually around 98 per cent. It lay from Tahiti, from Honolulu, from San Francisco and from Sydney. Its remoteness would dominate the logistic preparations for Operation Grapple. It had no indigenous population, but about 260 Gilbertese civilians lived on the island, in a village near Port London. They came from the Gilbert and Ellice Islands, and worked the coconut plantations to produce copra. While most only stayed for a year or two, some had been on the island for a decade or more. Although Christmas Island was the main base, the area around Malden Island to the south was to be the site for the air-dropped tests, and Penrhyn Island, farther south was used as a technical monitoring site and as a weather station. A United States Air Force special weapons monitoring team was based there, and the airstrip was improved to allow its supporting Douglas C-124 Globemaster II to use it.
South Pacific Air Lines had been granted permission by the United States and British governments to operate a flying boat service from Christmas Island. Patrick Dean asked the British Ambassador to the United States, Sir Roger Makins, to sound out the US government about terminating the contract. Makins reported in March 1956 that Admiral Arthur W. Radford, the Chairman of the Joint Chiefs of Staff, was willing to help so long as the dormant American claim to the island was not prejudiced. The lease on the island facilities, including the airfield and the port, had been granted to SPAL with a clause in the contract that said it could be terminated if there was a military necessity to do so. The Americans proposed that the British tell SPAL that they were establishing an airbase on the island, and that the United States would support this so long as SPAL was paid fair compensation. An official letter was sent to the president of SPAL on 1 May 1956, withdrawing the permit to operate from Christmas Island, regretting any inconvenience, and offering to consider compensation.