Blue Danube

The Blue Danube was the first operational British nuclear weapon, developed to fill an Operational Requirement under the designation OR.1001. It was also known as Smallboy, the Mk.1 Atom Bomb, and Special Bomb. British military planning initially anticipated a stockpile of up to 800 bombs based on the assumption that an atomic conflict could be conducted using weapons of similar yield to the Hiroshima bomb. The bomb bays of the Royal Air Force V-bomber force were designed specifically to accommodate this weapon.

The weapon's physics package was derived from research on the Hurricane fission device, tested in 1952. The Blue Danube utilized a ballistically shaped casing equipped with four flip-out fins to stabilize its trajectory during high-altitude release. The warhead initially employed a plutonium core, but operational versions were modified to use a composite plutonium and uranium-235 core to minimize the risk of predetonation and conserve fissile material. A uranium-only core was also tested. Firing circuits and radar altimeters were powered by lead-acid accumulators, which proved unreliable during its service life.

The United Kingdom was the sole operator of the Blue Danube. The first weapons were delivered to RAF Wittering in November 1953, with No. 1321 Flight RAF established in April 1954 to integrate the weapon into service. The bomb was designed for carriage by Valiant and Sperrin aircraft. The warhead underwent proof-testing in autumn 1956 during Operation Buffalo at Maralinga, Australia. On 11 October 1956, during the Kite test, a Valiant conducted the first live drop of a British atomic bomb. A total of 58 Blue Danube bombs were produced before production transitioned to the Red Beard weapon in 1958. The Blue Danube was retired from service in 1962. Dedicated storage facilities were constructed at RAF Barnham and RAF Faldingworth to house the weapon's components.