Final answer:
The GBU-39 variant named Focused Lethality Munition is a precision-guided bomb designed to reduce collateral damage. The Little Boy atomic bomb used uranium-235, detonated by bringing subcritical masses together, causing significant immediate and long-term casualties upon its use in Hiroshima.
Step-by-step explanation:
The GBU-39 Small Diameter Bomb variant named the Focused Lethality Munition is designed to minimize collateral damage in military operations. When constructing bombs like the atomic bombs used in World War II, different methods and materials were used. The Little Boy bomb was a gun-type fission bomb that used uranium-235 as its fissile material. It utilized a gun-type assembly method where two subcritical pieces of uranium-235 were forced together by explosive charges inside a cannon barrel to achieve a critical mass and subsequent detonation. The immediate impact of the Little Boy, dropped on Hiroshima, caused immense devastation and loss of life, with estimates of 70,000 killed upon detonation and thousands more from after-effects.
The FLM is a separate munition developed by the United States military for enhancing the lethality of bombs. Its design incorporates advanced technologies and targeting systems to provide more precise and effective strikes. The FLM is intended to minimize collateral damage by focusing its explosive power on a specific target.