Nuclear depth bomb

Nuclear depth bombs are designed to be dropped from aircraft or launched from surface ships, detonating at a preset depth to maximize the shock wave's effect on a submerged submarine. The underwater explosion generates a powerful pressure wave that can crush the hull of a submarine even at considerable distances, and the resulting bubble pulse and surface effects can also damage surface vessels. Early designs, such as the US Mark 90 Betty, were unguided and relied on a time or pressure fuse, while later models like the B57 incorporated more reliable detonation mechanisms and variable yield options. The Soviet Union developed similar weapons, including the 8F-5 and RN-28, and the United Kingdom fielded the WE.177A, which could be used in a nuclear depth bomb role. These weapons were typically stored on aircraft carriers and patrol aircraft, ready for rapid deployment against detected submarine contacts.

The first nuclear depth bomb, the US Mark 90 Betty, entered service in the early 1950s, followed by the more advanced Mark 101 Lulu and the B57, which became the standard US weapon until the end of the Cold War. The Soviet Union developed its own nuclear depth bombs, such as the 8F-5, which was deployed on Tu-95 Bear aircraft and later on surface ships. The United Kingdom's WE.177A, introduced in the 1960s, was designed for both anti-submarine and tactical strike roles. These weapons were integrated into naval doctrine as a means to counter the growing threat of fast, deep-diving nuclear submarines. However, their use was never authorized in combat, and by the 1990s, most nuclear depth bombs were retired or converted to conventional roles, partly due to arms control agreements and the changing strategic environment.

The primary tactical advantage of a nuclear depth bomb was its ability to destroy a submarine with a single shot, even if the exact position was uncertain, due to the large lethal radius of the nuclear explosion. However, this came with significant drawbacks: the detonation would also endanger friendly forces in the area, cause radioactive contamination of the ocean, and potentially escalate a conflict to the nuclear level. As a result, rules of engagement for nuclear depth bombs were extremely restrictive, often requiring high-level authorization. The development of accurate, long-range conventional torpedoes and standoff weapons gradually reduced the perceived need for nuclear ASW weapons, leading to their phase-out. The environmental impact of underwater nuclear tests, such as those conducted at the Pacific Proving Grounds, also drew international criticism and contributed to the Limited Test Ban Treaty of 1963, which prohibited nuclear tests in the atmosphere, outer space, and underwater.

One lesser-known fact is that the US Navy also developed a nuclear-armed rocket-assisted depth bomb, the RUR-5 ASROC, which could deliver a nuclear depth charge to a range of several miles, allowing a ship to attack a submarine without being directly overhead. Another obscure detail is that the Soviet Union's nuclear depth bombs were often carried by anti-submarine helicopters, such as the Ka-25 Hormone, which could hover and drop the weapon precisely. The UK's WE.177A was notable for its dual capability, being used both as a depth bomb and as a tactical nuclear bomb for land attack. Additionally, the development of nuclear depth bombs spurred research into the effects of underwater nuclear explosions, including the phenomenon of the 'base surge' — a cloud of radioactive water that can spread over a wide area. These weapons were also a factor in the development of submarine quieting technologies, as submarines sought to avoid detection and thus the threat of a nuclear depth bomb attack.

Depth charge

A conventional anti-submarine weapon that detonates at a preset depth.

Yield

The explosive energy of a nuclear weapon, typically measured in kilotons (kt) or megatons (Mt).

Base surge

A cloud of radioactive water and debris that forms after an underwater nuclear explosion.