This
is Violet Club, the interim megaton weapon that was briefly deployed
in the late 1950s. The casing was a Blue Danube. The Blue Danube centre
section was modified to carry a .5MT Green Grass U235 fission warhead
— one of the largest pure-fission warheads ever constructed. Because
Violet Club fell short of OR1136, the operational requirement for a
megaton weapon, it had some severe handling restrictions. The few that
were assembled were allocated to Vulcans at RAF Finningley and RAF Scampton.
Subsequently, the Green Grass warheads were removed from Violet Clubs
and incorporated into more-developed Yellow
Sun Mk1s. The Green Grass warhead was never tested. Externally it
was similar to Green Bamboo, a boosted fission device that was not tested
either. Scientists based their calculations on the successful detonation
of a warhead called Orange Herald (small), shown (lower) in a Blue Danube
centre section, a lightweight warhead designed for the Blue Streak Missile.