This bomb was dropped by a B-29 bomber called “Enola Gay”. The first atomic bomb was to be used as a weapon. "Little Boy" was her code name, she was dropped on the flat terrain of Hiroshima. The bomb vaporized buildings and killed thousands of people. The bomb was detonated 580 meters above the center of Hiroshima at 8:15 am local time with an estimated yield of 15 kilotons. The height of the explosion was chosen to maximize the magnitude of the immediate effects and to minimize residual radiation fallout. Individuals at the zero point received combined neutron and gamma doses of about 80,000 rads, which are used to measure radiation. Immediately fatal, the thermal flash produced wildfires that coalesced into a firestorm, razing much of of the city, and the immediate radiation killed most people within 0.8 miles of the ground