Little Boy - The Bombing of Hiroshima

The Bombing of Hiroshima

The bomb was armed in flight 31,000 feet (9,400 m) above the city, then dropped at approximately 08:15 (JST) August 6, 1945. After falling for 44.4 seconds, the time and barometric triggers started the firing mechanism. The detonation happened at an altitude of 1,968 feet (600 m). The official yield estimate of "Little Boy" was about 13 kilotons of TNT equivalent in explosive force, i.e. 6.3 × 1013 joules = 63 TJ (tera-joules). The actual yield estimated after an analysis of blast damage was about 13 kilotons. It was less powerful than "Fat Man", which was dropped on Nagasaki (21–23 kt).However, the damage and the number of victims at Hiroshima were much higher, as Hiroshima was on flat terrain, while the hypocenter of Nagasaki lay in a small valley. According to figures published in 1945, 66,000 people were killed as a direct result of the Hiroshima blast, and 69,000 were injured to varying degrees.

The U.S. Department of Energy gives this account of the death toll of the bombing of Hiroshima:

"By the end of 1945, because of the lingering effects of radioactive fallout and other after effects, the Hiroshima death toll was probably over 100,000. The five-year death total may have reached or even exceeded 200,000, as cancer and other long-term effects took hold."

The success of the bombing was reported with great enthusiasm in the United States in the days following the attacks. See Atomic bombings of Hiroshima and Nagasaki for discussion of contemporary support vs. opposition to the bombings, on both moral and military grounds.