woman holding a book
The smallest nuclear weapon known to the public was the W54, a 10.6″ x 15.7″ (27.3 x 40 cm) cylinder that weighed just 51 pounds (23 kg). The W54 was used in both the Davy Crockett recoilless rifle (a nuclear mortar for ground troops) and the Mk-54 SADM (Special Atomic Demolition Munition), a hand-held nuclear time bomb for attacking enemy ports. The W54 prototype, tested during Operation Hardtack in 1954, was even smaller, at just 10.6″ x 11.8″ (27 x 30 cm), close to what many nuclear scientists believe to be the smallest nuclear weapon. in theory. The Davy Crockett had a yield of 10 to 20 tons, intentionally kept low to be safe for those who shot it, while the SADM had a yield that varied between 10 tons and 1 kiloton.
To create a nuclear weapon, you need a critical mass of fissile material and a chassis for a gun-like trigger or explosive lenses. A critical mass of plutonium is about 10.5 kg (23 pounds), 10.1 cm (4 inches) in diameter. This isn’t enough to start a multiplicative chain reaction, but it does produce enough radiation to be deadly if you hold it.
To produce a chain reaction it is necessary to increase the plutonium, just a little: just 10% over the critical mass is enough to create a nuclear weapon with a yield of 10-20 tons, already within the range of Davy Crockett’s warhead . 20% above the critical mass gives a yield of 100 tons, while 35% above the critical mass can reach 250 tons. Smaller nukes would have a yield somewhere in this range.
The public can’t know for sure what the smallest nuclear weapon is, because it’s probably classified. The Soviet Union has worked on a variety of nuclear weapons that remain completely secret, as has the US, although there is more transparency in the latter case. A former Soviet general, Alexander Lebed, claimed the existence of “nuclear suitcases” at a press conference in September 1997, sparking speculation as to whether the smallest nuclear weapon would fit into a 60 x 40 x 20 cm suitcase. cm. The general consensus is that there would be plenty of room to create a nuclear weapon, especially for a technologically sophisticated country. However, there is little concrete evidence for this.