Blue Danube (nuclear weapon)
Blue Danube was the designation of the first U.K. nuclear weapon, a implosion gravity bomb carried by V-bomber aircraft. It was first deployed in 1953 and retired in 1962. 58 were built, but probably never all operational at the same time. It was replaced by the smaller Red Beard.
The design derived both from the British Hurricane physics package and the U.S. Mark 4 Blue Danube free-fall bomb, in November 1953. Much like the Mark 4, it had a "32 lens implosion system with a levitated core suspended within a natural uranium tamper. The warhead was contained within a bomb casing measuring 62 inches (1.6 m) diameter and 24 feet (7.3 m) long", which could fit only in a heavy bomber. Aerodynamics of the bomb casing were considerably different from U.S. practice; the case was longer and heavier, but more stable.
Blue Danube was adapted, with varying success, to other nuclear weapons. The British Army attempted to deploy a truck-carried atomic demolition munition, with code names that changed when compromised: first Brown Bunny, then Blue Bunny, then Blue Peacock. Blue Peacock was the best-known name. A somewhat more powerful version was too heavy for field use; the trucks could not get off paved roads. There were also problems in maintaining a stable temperature inside the casing, with one rather unusual solution.
In 2002, attention was called to the detailed design being available in the Public Records Office. The Ministry of Defence said it had been declassified seven years earlier. An Opposition spokesman said
a monstrous free gift to terrorists...The fact that this information has been lying in the public records office is extraordinary. Such information about may already be in the public domain, but why needlessly help rogue states and terrorist organisations with such comprehensive instructions on how to make an atom bomb? 
The U.S. has not released comparable detail. Still, it would require weapons-grade plutonium and other specialized materials to make from the plans, and first-generation implosion device technology is reasonably well-known.
- , Blue Danube (Mark 1), Britain's Nuclear Weapons: History of the British Nuclear Arsenal, Nuclear Weapons Archive, 30 April 2002
- Richard Moore, The Real Meaning of the Words: a Pedantic Glossary of British Nuclear Weapons, Mountbatten Center for International Studies, UK Nuclear History Working Paper Number: 1
- "UK reveals nuclear bomb plans", CNN, 15 April 2002