The temperatures required for the reaction are produced by the detonation of an atomic bomb. Thermonuclear bomb, weapon whose explosive power results from an uncontrolled self-sustaining chain reaction in which isotopes of hydrogen combine under high temperatures to form helium in a process known as nuclear fusion. A nuclear weapon (also called an atom bomb, nuke, atomic bomb, nuclear warhead, A-bomb, or nuclear bomb) is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or from a combination of fission and fusion reactions (thermonuclear bomb).Both bomb types release large quantities of energy from relatively small amounts of matter. This silent footage, in both color and black and white, shows the preparation of the “Little Boy” and “Fat Man” atomic bombs on Tinian Island. Or small as is explosive yield? If less than critical mass is present, nuclear explosion cannot occur. Nuclear weapons are far more destructive than any conventional (non-nuclear) weapon. Little Boy, the nuclear bomb that U.S. forces dropped on the Japanese city of Hiroshima on August 6th, 1945, leveled a two-mile radius of the city, killing an estimated 80,000 people. Scientists and engineers have found many uses for this energy from the production of electricity to the destructive power of nuclear weapons. The first atomic bombs were detonated during World War II. NUKEMAP is a mapping mash-up that calculates the effects of the detonation of a nuclear bomb. North Korea has made a nuclear weapon small enough to fit on a missile. Interest in small nuclear reactor designs has grown steadily in recent years, as technology advances to create more power from less fuel. The footage … ... less than one-tenth the weight of the first atomic bomb… They are often called atomic bombs or hydrogen bombs. The Little Boy weapon which was the first of the atomic bombs that was deployed (and was dropped on Hiroshima) weighed some 8,818.49 pounds, or 4,000 kilograms. Update: I am writing a paper on the changes to nuclear weapons from 1940 to today. It includes the takeoff and return of the Enola Gay, which dropped "Little Boy" on Hiroshima on August 6, 1945. Power-technology.com lists the world's 10 smallest commercial nuclear reactors, either in operation or under construction. The determining factor in both cases is critical mass of the fissile material (Plutonium). What does a government made nuclear warhead weigh, and cost to make? How much does a standard, modern, nuclear warhead weigh? Small as in physical size. A link is provided below. First, a test bomb exploded in the New Mexican desert. Nuclear energy results from changes in the nucleus of atoms. And how much does it cost to make one? How worried should the world be? Then, bombs were dropped on two unsuspecting Japanese cities.