The United States of America became the first country in the world to use nuclear bombs against any country when it deployed atomic bombs named ‘Little Boy’ and ‘Fat Man’ on the Japanese cities of Hiroshima and Nagasaki during World War II. More than 1,40,000 people were killed in the attack. 

On the 76th anniversary of Hiroshima Day, let us have a quick look at the specifics of the two bombs.

The nuclear bomb code-named “Little Boy” was dropped on the Japanese city of Hiroshima by the United State of America on August 6, 1945. The bomb was the first of its kind to be used in warfare and weighed approximately 4,400 kilograms and was 10 feet in length. The bomb was created at the Los Alamos Laboratory as part of the Manhattan Project by Lieutenant Commander Francis Birch’s group according to AtomicHeritage.org.

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With a diameter of 28 inches, the bomb had a filling of Uranium-235 and a blast yield of 15 kilotons of TNT. The Uranium filling used in the bomb weighed around 63 kilograms.

The bomb was a gun-type device where the critical mass was achieved via the firing of a uranium projectile through a gun barrel at a uranium target as per AtomicHeritage.org. 

The target case of the bomb, its barrel, and other main parts were ferried to Tinian Island from where the it was dropped at Hiroshima by a B-29 Enola Gay jet which was piloted by Colonel Paul Tibbets.

The second bomb nicknamed “Fat-man” was dropped on the Japanese town of Nagasaki on August 9, 1945. The bomb was a second plutonium implosion-type bomb. In this bomb, the core of plutonium was surrounded by thousand pounds of high-explosives which when exploded would cause the plutonium into a supercritical state. With a weight of more than 4898 kgs the bomb was 10 feet in length and had a diameter of 60 inches, much larger than the first nuclear bomb ‘Little Boy.’

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Instead of a uranium filling like the ‘Little Boy’, the ‘Fat Man’ had highly enriched plutonium 239 as it’s core ingredient, and the Plutonium fuel used in the bomb measured around 6.2 kilograms, however, it’s core was surrounded by high explosives of around 2404 kilograms in weight according to the AtomicHeritage.org. The bomb had 10 times the efficiency of ‘Little Boy’ and used Beryllium-Polonium to initiate the core. The bomb had the explosive force of 21,000 tons of TNT and was dropped on the city of Nagasaki by a B-29 Bockscar which was piloted by Major Charles Sweeney.