Original sentence: It was the first atomic bomb ever used as a weapon, and was dropped three days before the "Fat Man" bomb was used against Nagasaki.Its design was never tested, unlike the more complex plutonium bomb (Fat Man), which was detonated at the Trinity test site.Little Boy was the codename of the atomic bomb that was dropped on Hiroshima on August 6, 1945 by the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets in the 393d Bombardment Squadron, Heavy of the United States Army Air Forces.The Hiroshima bombing was the second artificial nuclear explosion in history (the first was the "Trinity" test), and it was the first uranium-based detonation.The available supply of enriched uranium was very small at that time, and it was felt that the simple design of a uranium "gun" type bomb was so sure to work that there was no need to test it at the full scale (small-scale experiments were used to determine the critical mass and other properties)
Edited sentence: (Small-scale experiments were used to determine the critical mass and other properties).It was the first atomic bomb to be used as a weapon.Its design was not tested in advance, unlike the more complex plutonium bomb (Fat Man).Little Boy was the codename of the atomic bomb dropped on Hiroshima on August 6, 1945 by the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets of the 393d Bombardment Squadron, Heavy, of the United States Army Air Forces.The Hiroshima bombing was the second artificial nuclear explosion in history, after the Trinity test, and the first uranium-based detonation.The available supply of enriched uranium was very small at that time, and it was felt that the simple design of a uranium "gun" type bomb was so sure to work that there was no need to test it at full scale.The second, the "Fat Man", was dropped three days later on Nagasaki