Operation Grapple (nonfiction)

Operation Grapple was the name 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 Christmas Island 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 with 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 British contribution to 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 in nuclear weapons technology. In July 1954, Cabinet decided to develop the hydrogen bomb. The United Kingdom Atomic Energy Authority Atomic Weapons 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 first test series consisted of three tests in May and June 1957. In the first, 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 300 kilotonnes of TNT (1,300 TJ), far below its designed capability. Despite its failure, 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 was Grapple 2, of Orange Herald. Its 720-to-800-kilotonne-of-TNT (3,000 to 3,300 TJ) yield made it technically a megaton weapon. It was the largest ever achieved by a single stage device. Grapple 3 tested Purple Granite, a Short Granite with some fixes. Its yield was a very disappointing 300 kilotonnes of TNT (1,300 TJ).

A second test series was required. This consisted of a single test, known as Grapple X, in November 1957. This time the yield of 1.8 megatonnes of TNT (7.5 PJ) exceeded expectations. This was a true hydrogen bomb, but most of the yield came from nuclear fission rather than nuclear fusion. In a third series with a single test, known as Grapple Y, in April 1958, another design was tested. With an explosive yield of about 3 megatonnes of TNT (13 PJ), 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 reaction instead of fission of a heavy uranium-238 tamper, making it a true hydrogen bomb, and because its yield had been closely predicted—indicating that its designers understood what they were doing. 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; another was a blind radar test drop. A moratorium on testing came into effect in October 1958, and Britain never resumed atmospheric testing.