Orange Herald

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Orange Herald was the name of a British nuclear weapon of the 1950s.

[edit] Technical

Orange Herald was a fusion boosted British fission nuclear weapon, comprising of a U-235 primary surrounded by Lithium deuteride. 'Herald' was suitable for mounting on a missile, utilizing 117 kg of U-235. However, Britain's annual production of U-235 was only 120 kg at this time, which would have made such weapons rare and very expensive.

This device yielded 720 kT of explosive power in the Grapple 2/Orange Herald tests on Malden Island in the Pacific, and remains the largest fission device ever tested. It is thought that the fusion boosting failed to increase the yield.

Britain rushed the development of these predicted-megaton class weapons as in 1955 it seemed that atmospheric testing could soon be outlawed by treaty, and it wanted to demonstrate its capability before it wouldn't be able to do so legally.