How does an Atomic Bomb work?
Little Boy
The Little Boy was 300 cm in length, 71 cm in diameter and weighed approximately 4,400 kg. The design used the gun method to explosively force the uranium-235 and a solid target cylinder together initiating a nuclear chain reaction. This was accomplished by shooting one piece of the uranium onto the other by means of four cylindrical silk bags of nitrocellulose powder. The bomb contained 64 kg of enriched uranium. Less than a kilogram of uranium underwent nuclear fission, and of this mass only 0.6 g was transformed into a different type of energy, initially kinetic energy, then heat and radiation.
The bomb was set to detonate at a certain altitude. When the altitude got low enough, there would be a small explosion inside, causing the Uranium "Bullet" to fly towards the target at a great speed, causing Nuclear Fission to happen. This causes a chain reaction, creating an immense force that is the nuclear bombexplosion.
Inside the weapon, the uranium-235 material was divided into two parts, following the gun principle: the "projectile" and the "target". The projectile was a hollow cylinder with 60% of the total mass 38.5 kg. It consisted of a stack of 9 uranium rings, each 159 mm in diameter with a 100 mm bore in the center, and a total length of 180 mm, pressed together into the front end of a thin-walled projectile 413 mm long. Filling in the remainder of the space behind these rings in the projectile was a tungsten carbide disc with a steel back. At ignition, the projectile slug was pushed 1,100 mm along the 1,800 mm long, 170 mm smooth-bore gun barrel. The slug "insert" was a 100 mm cylinder, 180 mm in length with a 25 mm axial hole. The slug comprised 40% of the total fissile mass (25.6 kg). The insert was a stack of 6 washer-like uranium discs somewhat thicker than the projectile rings that were slid over a 25 mm rod. This rod then extended forward through the tungsten carbide tamper plug, impact-absorbing anvil, and nose plug backstop eventually protruding out the front of the bomb casing.
Fat Man
"Fat Man" was the second plutonium, implosion-type bomb. The first was the "Gadget" detonated at the Trinity site on July 16, 1945. In the implosion-type device, a core of sub-critical plutonium is surrounded by several thousand pounds of high-explosive designed in such a way that the explosive force of the He is directed inwards thereby crushing the plutonium core into a super-critical state. Dropped on the Japanese city of Nagasaki on August 9, 1945, it was the second nuclear weapon used in a war.
This bomb had a core of plutonium 239, was 3.5 meters in length by 1.5 meters in diameter, and it weighed 4.5 tons. Its plutonium core was surrounded by 64 explosive charges arranged in an inner and outer shell. The explosive charges were fabricated in a sphereical shape—an extremely difficult and demanding procedure. When the two shells were detonated, the shock wave slammed into a tamper surrounding the plutonium nucleus, causing a rapid increase in density that compressed the slightly sub-critical plutonium core, rapidly increasing its density, making it super-critical, thus exploding in a nuclear chain reaction.
What isNuclearFission
The isotopes uranium-235 and plutonium-239 were selected by the atomic scientists because they readily undergo fission. Fission occurs when a neutron strikes the nucleus of either isotope, splitting the nucleus into fragments and releasing a tremendous amount of energy. The fission process becomes self-sustaining as neutrons produced by the splitting of atom strike nearby nuclei and produce more fission. This is known as a chain reaction and is what causes an atomic explosion.
When a uranium-235 atom absorbs a neutron and splits into two new atoms, releasing three new neutrons and great amounts of energy. These new neutrons then collide with an atom of uranium-235, which then splits and releases two neutrons and some binding energy. Both of those neutrons collide with uranium-235 atoms, each of which fission and release between one and three neutrons, and so on. This causes a nuclear chain reaction.
