Red Beard was an unboosted fission weapon that used a composite core (mixed core in British terminology of the time). The composite core used both weapons-grade plutonium and weapons-grade uranium-235, and was intended to minimise the risk of pre-detonation that was a feature of all-plutonium designs of that period with yields larger than 10 kilotons (kt). An added benefit of the composite core was a more economical use of fissile material. The design was tested twice during the Operation Buffalo series of nuclear trials at Maralinga in Australia – first on 27 September 1956: a 15 kt explosion, after which the resulting mushroom cloud rose to a height of , and again on 22 October 1956. Although the design concept of Red Beard was similar to that of the Blue Danube warhead, an innovative means of implosion meant that its overall size could be significantly reduced.