WE.177

The WE.177 was a series of tactical and strategic nuclear weapons operated by the United Kingdom's Royal Air Force (RAF) and Royal Navy. The design originated from the American W59 warhead, acquired during the GAM-87 Skybolt program. Due to concerns regarding the sensitivity of the W59's primary stage to mechanical shock, a development program codenamed "Cleo" was initiated to create a shock-insensitive primary using alternative explosives. Following the cancellation of the Skybolt program, the design was adapted to replace the Red Beard weapon, eventually leading to the development of three distinct service variants: A, B, and C.

The weapon was designed for delivery by fixed-wing aircraft and could be parachute-retarded. The WE.177 featured a robust casing engineered to withstand high-velocity, low-altitude deployment and the physical forces of impact. The arming and safety system utilized a key-operated Strike Enable Facility with unique cylindrical barrel keys and multiple safety breaks in the arming chain. The physics package employed a boosted fission design using tritium gas.

The WE.177A was a variable-yield weapon configured for surface attack or as a nuclear depth bomb. In the anti-submarine role, it could be deployed by helicopters in addition to fixed-wing aircraft, utilizing a lower yield for shallow waters to limit damage to nearby shipping and a higher yield for deep ocean environments. The WE.177B and WE.177C were fixed-yield weapons designed for strategic and tactical strike roles, respectively. These heavier variants utilized larger casings and were configured for airburst, impact, or laydown delivery options.

The WE.177 was widely deployed across multiple Royal Navy and RAF platforms, including the Avro Vulcan, de Havilland Sea Vixen, Blackburn Buccaneer, SEPECAT Jaguar, Panavia Tornado, and Sea Harrier. During the 1982 Falklands War, WE.177A weapons routinely carried on Royal Navy vessels were transported south with the Naval Task Force. To ensure safety and treaty compliance, the weapons were transferred from escort frigates to the deep magazines of aircraft carriers and fleet replenishment ships, remaining outside of Falkland Islands territorial waters and the Latin America Nuclear Weapons Free Zone before being returned to the United Kingdom.

The Royal Navy retired its WE.177 weapons in 1992, followed by the RAF in 1998, marking the retirement of the United Kingdom's last tactical nuclear weapon and the RAF's final nuclear bomb.