Fat Man
A post-war "Fat Man" model.
Type	Nuclear weapon
Place of origin	United States
Specifications
Weight	10,200 lbs (4,630 kg)
Length	10. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. The United States of America —commonly referred to as the 6 Feet (3. 25m)
Diameter	5 Feet (1. 52m)
Blast yield	21 kilotons

"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. ( is the Capital and the largest city of Nagasaki Prefecture in Japan. For a topic outline on this subject see List of basic Japan topics. The United States of America —commonly referred to as the Events 48 BC - Caesar's civil war: Battle of Pharsalus - Julius Caesar decisively defeats Pompey at Pharsalus Year 1945 ( MCMXLV) was a Common year starting on Monday (link will display the full calendar It was the second of the two nuclear weapons to be used in warfare and was the third man-made nuclear explosion at that time. War is an international relations Dispute, characterized by organized Violence between National Military units The name also refers more generically to the early nuclear weapon designs of U. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate S. weapons based on the "Fat Man" model. It was an implosion-type weapon with a plutonium core. Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate ^[1]

Fat Man was possibly named after Winston Churchill^[2], though Robert Serber said in his memoirs that as the "Fat Man" bomb was round and fat, he named it after Sidney Greenstreet's character in The Maltese Falcon. Sir Winston Leonard Spencer-Churchill, KG, OM, CH, TD, FRS, PC, PC (Can ( 30 November 1874 Robert Serber ( March 14 1909 - June 1 1997) was an American physicist who participated in the Manhattan Project. Sydney Hughes Greenstreet ( December 27 1879 &ndash January 18 1954) was an English Actor, best known for his work with The Maltese Falcon is a 1941 Warner Bros film written and directed by John Huston, based on the novel of the same name During development, however, there was little uniformity, and both it and the shotgun design, now commonly known as Little Boy, were variously called Fat Boy, Thin Man (allegedly after FDR), S-1, and "the gadget". Gun-type fission weapons are fission -based Nuclear weapons whose design assembles their fissile material into a supercritical mass by the Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the " The gadget " was the code-name given to the first nuclear explosive developed under the Manhattan Project during World War II, which was ^[3]

"Fat Man" was detonated at an altitude of about 1,800 feet (550 m) over the city, and was dropped from a B-29 bomber Bockscar, piloted by Major Charles Sweeney of the 393d Bombardment Squadron, Heavy. Bockscar, sometimes called Bock's Car or Bocks Car, is the name of the United States Army Air Forces B-29 Bomber that Major General Charles W Sweeney (27 December 1919 - 16 July 2004 was an officer in the U The 393d Bomb Squadron ( 393 BS) is part of the 509th Bomb Wing at Whiteman Air Force Base, Missouri. The bomb had a yield of about 21 kilotons of TNT, or 8. Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 78×10¹³ joules = 88 TJ (terajoules). The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity TERA is a shielded Twisted pair connector for use with Category 7 twisted-pair data cables developed by The Siemon Company and standardized in 2003 by ^[4] Because of Nagasaki's hilly terrain, the damage was somewhat less extensive than that in relatively flat Hiroshima. The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's An estimated 39,000 people were killed outright by the bombing at Nagasaki, and about 25,000 were injured. ^[5] Thousands more would die later from related blast and burn injuries, and hundreds more from radiation illnesses from exposure to the bomb's initial radiations. Radiation poisoning, also called " radiation sickness " or a " creeping dose " is a form of damage to organ tissue due to excessive exposure to The aerial bombing raid on Nagasaki had the third highest fatality rate^[6] in World War II after the nuclear strike on Hiroshima^{[7][8][9][10]} and the March 9/10 1945 fire bombing raid on Tokyo^[11]. ( is the Capital and the largest city of Nagasaki Prefecture in Japan. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at

Technology

The weapon was 10 feet 8 inches (3. 25 m) long, five feet (1. 52 m) in diameter, and weighed 10,200 pounds (4,630 kg). In accordance with the name, it was more than twice as wide as Little Boy, which was dropped on Hiroshima three days earlier; however, the mass was only 10% more than that of Little Boy. Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's

"Fat Man" was an implosion-type weapon using plutonium 239. Implosion is a process in which objects are destroyed by collapsing in on themselves Plutonium-239 is an Isotope of Plutonium. Plutonium-239 is the primary Fissile isotope used for the production of Nuclear weapons although A subcritical sphere of plutonium was placed in the center of a hollow sphere of high explosive. A critical mass is the smallest amount of Fissile material needed for a sustained Nuclear chain reaction. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Numerous detonators located on the surface of the high explosive were fired simultaneously to produce a powerful inward pressure on the core, squeezing it and increasing its density, resulting in a supercritical condition and a nuclear explosion. The exploding-bridgewire detonator ( EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnson for the Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different

The difficulty in the design lay primarily in properly compressing the plutonium core into a near-perfect sphere; if the compression was not symmetrical it would cause the plutonium to be ejected from the weapon, making it an inefficient "dirty bomb". The term dirty bomb is primarily used to refer to a radiological dispersal device ( RDD) a speculative Radiological weapon which combines Radioactive In order to accomplish the compression, the high explosive system had to be carefully designed as a series of explosive lenses which used alternating fast- and slow-burning explosives to shape the explosive shockwave into the desired spherical shape. An explosive lens —as used for example in Nuclear weapons ��is a highly specialized explosive charge An early idea of this sort had been raised by physicist Richard Tolman during early discussions of possible bomb designs, specifically in having many pieces of fissile material attached to explosives that would then assemble them in a spherical fashion. A physicist is a Scientist who studies or practices Physics. Physicists study a wide range of physical phenomena in many branches of physics spanning Richard Chace Tolman ( March 4 1881 &ndash September 5 1948) was an American mathematical physicist and Physical chemist This idea was further developed by Seth Neddermeyer, who attempted to find a way to collapse a hollow sphere of plutonium onto a solid sphere of it inside itself. Seth Henry Neddermeyer ( 16 September 1907, Richmond Michigan - 29 January 1988, Seattle Washington) was an Neither of these ideas relied on compression of the plutonium, and neither would assemble the device fast enough to avoid predetonation (see discussion below). ^[12]

The idea of using shaped charges came from James L. Tuck^[13] and was developed by mathematician John von Neumann^[14], and the idea that under such pressures the plutonium metal itself would be compressed may have come about from conversations with Edward Teller, whose knowledge of how dense metals behaved under heavy pressure was influenced by his theoretical studies of the Earth's core with George Gamov. A shaped charge is an Explosive charge shaped to focus the effect of the explosive's energy James Leslie Tuck OBE, ( January 9, 1910 – December 15, 1980) was a British Physicist. Edward Teller (original Hungarian name Teller Ede) (January 15 1908 &ndash September 9 2003 was a Hungarian -American theoretical Physicist George Gamow (pronounced as ˈgamof ( March 4, 1904 &ndash August 19, 1968), born Georgiy Antonovich Gamov (Георгий Антонович ^[12] Von Neumann and George Kistiakowsky eventually became the principal architects behind the lens system. George Bogdan Kistiakowsky ( November 18, 1900 &ndash December 7, 1982) (Георгий Богданович Кистяковский was a Robert Christy is generally credited with the insight that a solid subcritical sphere of plutonium could be compressed to a critical state greatly simplifying the task since earlier efforts had attempted the more difficult compression of 3d shapes like spherical shells. Robert F Christy (born 1916 in Vancouver is an American Theoretical physicist and later Astrophysicist who worked on the Manhattan Project. Because Christy's insight made the feasibility of a plutonium bomb much more likely, the weapon tested at Alamogordo and used at Nagasaki is sometimes referred to as the "Christy Gadget. Alamogordo is a city in Otero County, New Mexico, United States of America. "

The "Trinity" device was similar to the "Fat Man" bomb. Trinity was the first test of technology for a Nuclear weapon.

At first it was thought that two pieces of subcritical plutonium (Pu-239) could simply be shot into one another to create a nuclear explosion, and a plutonium gun-type design of this sort (known as the "Thin Man" bomb) was worked on for some time during the Manhattan Project. The "Thin Man" (formally Mark 2) nuclear bomb was a proposed Plutonium gun-type nuclear bomb which the United States was However in April 1944 it was discovered by Emilio Segrè that plutonium created for the bomb in the nuclear reactors at Hanford, Washington—even though it was supergrade weapon plutonium containing only about 0. Emilio Gino Segrè ( February 1, 1905 – April 22, 1989) was an Italian Physicist and Nobel laureate in This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled The Hanford Site is a decommissioned nuclear production complex on the Columbia River in south-central Washington operated by the United States government 9% Pu-240—was not as pure as the initial samples of plutonium developed at the cyclotrons at Ernest O. Lawrence's Radiation Laboratory in Berkeley, California. A cyclotron is a type of Particle accelerator. Cyclotrons accelerate Charged particles using a high- Frequency, alternating Voltage (potential Ernest Orlando Lawrence ( August 8, 1901 – August 27, 1958) was an American physicist and Nobel Laureate best known for his The Ernest Orlando Lawrence Berkeley National Laboratory ( LBNL) is a U Berkeley is a city on the east shore of San Francisco Bay in Northern California, in the United States. Because of the presence of the Pu-240 isotope, reactor-bred plutonium had a much higher rate of spontaneous neutron emission than was previously thought, and if a gun-type device was used it would most likely pre-detonate and result in a messy and costly "fizzle. Neutron emission is a type of Radioactive decay of atoms containing excess Neutrons in which a neutron is simply ejected from the nucleus " The spontaneous fission rate of Pu-240 is 40,000 times greater than that of Pu-239, so that in a gun-type plutonium device of the sort planned during the Manhattan Project, the last few centimeters would have to be traveled in less than 40 microseconds. Spontaneous fission (SF is a form of Radioactive decay characteristic of very heavy Isotopes and is theoretically possible for any atomic nucleus whose mass is greater

After this problem was realized, the entire Los Alamos laboratory re-organized around the problem of the implosion bomb, the "Fat Man" starting in June 1944. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a

The gun-type method could still be used for highly enriched uranium, though, and was employed in the "Little Boy" weapon, which was used against Hiroshima. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Little Boy was the Codename of the Atomic bomb, developed via the "Manhattan Project" which was dropped on Hiroshima, on August 6 1945 by the The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's The implosion method is more efficient than the gun-type method, and also far safer, as a perfect synchronization of the explosion lenses is required for the core to properly detonate, greatly reducing the chances of an accidental nuclear detonation.

As a result of espionage information procured by Klaus Fuchs, the first Soviet bomb, "RDS–1" (above) closely resembled Fat Man, even in its external shape. Klaus Emil Julius Fuchs ( December 29, 1911 &ndash January 28, 1988) was a German -born theoretical physicist and The RDS-1 (РДС-1 also Joe-1, was the USSR's first Nuclear weapon test, named in reference to Joseph Stalin.

Because of its complicated firing mechanism, and the need for previously untested synchronization of explosives and precision design, it was felt that a full test of the concept was needed before the scientists and military representatives could be confident it would perform correctly under combat conditions. On July 16, 1945, a device utilizing a similar mechanism (called the "gadget" for security reasons) detonated in a test explosion at a remote site in New Mexico, known as the "Trinity" test. Events 622 - The beginning of the Islamic calendar. 1054 - Three Roman legates fractured relations between the Western and Year 1945 ( MCMXLV) was a Common year starting on Monday (link will display the full calendar " The gadget " was the code-name given to the first nuclear explosive developed under the Manhattan Project during World War II, which was Nuclear weapons tests are experiments carried out to determine the effectiveness yield and explosive capability of Nuclear weapons Throughout the twentieth century most nations New Mexico ( is a state located in the southwestern region of the United States of America. Trinity was the first test of technology for a Nuclear weapon. It gave somewhere around 20 kt (80 TJ), 2 to 4 times the expected yield.

The Soviet Union's first nuclear weapon detonated at Operation First Lightning (known as "Joe 1" in the West) was closely based on the "Fat Man" device, on which they had obtained detailed information from the spy Klaus Fuchs. The Soviet project to develop an atomic bomb began during World War II in the Soviet Union. The RDS-1 (РДС-1 also Joe-1, was the USSR's first Nuclear weapon test, named in reference to Joseph Stalin. Klaus Emil Julius Fuchs ( December 29, 1911 &ndash January 28, 1988) was a German -born theoretical physicist and

The names for all three projects ("Fat Man", "Thin Man", and "Little Boy") were created by Robert Serber, a former student of Los Alamos director Robert Oppenheimer's who worked on the project. Robert Serber ( March 14 1909 - June 1 1997) was an American physicist who participated in the Manhattan Project. According to his later memoirs, he chose them based on their design shapes; the "Thin Man" would be a very long device, and the name came from the Dashiell Hammett detective novel and series of movies by the same name; the "Fat Man" bomb would be round and fat and was named after Sidney Greenstreet's character in The Maltese Falcon. Samuel Dashiell Hammett ( May 27, 1894 — January 10, 1961) was an American Author of Hardboiled detective The Thin Man (1934 is a Hardboiled detective novel by Dashiell Hammett. The Thin Man was the first of six comic detective Films starring William Powell and Myrna Loy as Nick and Nora Charles, a hard-drinking Sydney Hughes Greenstreet ( December 27 1879 &ndash January 18 1954) was an English Actor, best known for his work with The Maltese Falcon is a 1930 Detective novel by Dashiell Hammett, originally serialized in the magazine " Black Mask " "Little Boy" would come last and be named only to contrast to the "Thin Man" bomb. ^[15]

Interior of bomb

The original blueprints of the interior of both Fat Man and Little Boy are still classified. However, much information about the main parts is available in the unclassified public literature. Of particular interest is a description of Fat Man sent to Moscow by Soviet spies at Los Alamos in 1945. It was released by the Russian government in 1992. ^[16]

Below is a diagram of the main parts of the "Fat Man" bomb itself, followed by a more detailed look at the different materials used in the physics package of the bomb (the part responsible for the nuclear detonation). Nuclear weapon designs are physical chemical and engineering arrangements that cause the physics package of a nuclear weapon to detonate

AN 219 contact fuse (four) Archie radar antenna Plate with batteries (to detonate charge surrounding nuclear components) X-Unit, a firing set placed near the charge Hinge fixing the two ellipsoidal parts of the bomb Physics package (see details below) Plate with instruments (radars, baroswitches and timers) Barotube collector California Parachute tail assembly (. 20-inch aluminium sheet)

Physics package

Assembly

Jim Sanborn's "Critical Assembly. " The bottom hemisphere of the pusher, with pieces of the boron shell, tamper, pit, and urchin.

The physics package getting its shell.

Fat Man on its transport carriage.

To allow insertion of the plutonium pit as late as possible in the bomb's assembly, the spherical U-238 tamper had a 4" diameter cylindrical hole running through it, like the hole in a cored apple. The missing cylinder, containing the plutonium pit, could be slipped in through a hole in the surrounding aluminium pusher. In August 1945, it was assembled on Tinian Island. When the physics package was fully assembled and wired, it was placed inside its ellipsoidal aerodynamic bombshell and wheeled to the bomb bay of a B-29 named "Bockscar" for its flight to Nagasaki on August 9. Events 48 BC - Caesar's civil war: Battle of Pharsalus - Julius Caesar decisively defeats Pompey at Pharsalus

In 2003, these concentric spheres and cylinder were recreated as the centerpiece of an art installation called "Critical Assembly" by sculptor Jim Sanborn. Using non-nuclear materials, he replicated the internal components of the "Trinity" bomb, which had the same design as Fat Man. Critical Assembly was first displayed at the Corcoran Gallery of Art, in Washington, DC. ^[17]

Detonation sequence

The plutonium must be compressed to twice its normal density before free neutrons are added to start the fission chain reaction:

•      An exploding-bridgewire detonator simultaneously starts a detonation wave in each of the 32 tapered high explosive columns (pentagons and hexagons arranged as on a soccer ball - in a truncated icosahedron). The exploding-bridgewire detonator ( EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnson for the The truncated icosahedron is an Archimedean solid. It comprises 12 regular pentagonal faces 20 regular hexagonal faces 60 vertices and 90 edges
•      The detonation wave (arrows) is initially convex in the
•      faster explosive, Composition B: 60% RDX, 39% TNT, 1% wax. Composition B is an Explosive consisting of castable mixtures of RDX and TNT as well as in some instances additional desensitizing agents Cyclotrimethylenetrinitramine, also known as RDX, cyclonite, hexogen, and T4, is an Explosive Nitroamine widely used Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 Its shape becomes concave in the
•      slower explosive (Baratol). Baratol is an Explosive made of a mixture of TNT and Barium nitrate, with a small quantity (about 1% of wax used as a binder The 32 waves merge into a single spherical implosive wave before they hit the
•      faster explosive, Composition B, of the inner charges. Composition B is an Explosive consisting of castable mixtures of RDX and TNT as well as in some instances additional desensitizing agents
•      The medium-density aluminum "pusher" transfers the imploding shock wave from low-density explosive to high-density uranium, minimizing undesirable turbulence; the shock wave then compresses the inner components. WikipediaNaming At the very center, the

•      beryllium–polonium-210 "initiator" (the "urchin") is crushed, bringing the two metals in contact to release a burst of neutrons into the compressed
•      "pit" of plutonium-239–plutonium-240–gallium delta-phase alloy (96%–1%–3% by molarity). Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance A fission chain reaction starts. The tendency of the fissioning pit to prematurely blow itself apart is retarded by the inward momentum of the
•      natural-uranium "tamper" (inertial containment). Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the The tamper also reflects neutrons back into the pit, speeding up the chain reaction.
•      The boron plastic shell was intended to protect the pit from stray neutrons, but was later deemed unnecessary.

The result is the fissioning of about two and a half of the thirteen pounds of plutonium in the pit, and the release of twenty-one kilotons of energy (21,000 tons of TNT).

Nagasaki casualties

According to published US Army figures 39,000 people were killed as a direct result of the Nagasaki blast, and 25,000 were injured to varying degrees. ^[18] Most sources refer to a great number more later dying as a result of radiation sickness and cancer or unborn babies that died before birth or were born with deformities ^[19] but this appears to be just commonly accepted urban myth and unsupported by the actual events and studies. Radiation poisoning, also called " radiation sickness " or a " creeping dose " is a form of damage to organ tissue due to excessive exposure to Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled

The survivors of both the Hiroshima and Nagasaki nuclear explosions have subsequently been some of the closest monitored survivors of the Second World War. Both Japanese and American medical institutes launched a massive and thorough epidemiological study after the war. The study included ALL residents of both Hiroshima and Nagasaki who had survived the atomic explosion within a 10 kilometre (6. 2 mile) radius. As previously noted the bombs were exploded as airbursts and there was no residual radioactive fallout, so anyone outside of 10 kilometres would have received no radioactive contamination.

Investigators questioned the residents to identify their precise locations when the bombs exploded, and used this information to calculate a personal radiation dose for each resident. Data was collected for all 86,572 survivors of the two bursts.

Sixty three years later the results from the extensive study are clear. The post event deaths from nuclear effects are not the alarmist tens of thousands up to 105,000 claimed in several sources. The subsequent deaths are actually less than 1,000 from the combined cities. In fact, in the years since 1945 just 777 eventually died as a result of radiation received from the atomic attacks:

87 have died from leukemia

440 died of radiation induced tumors;

and 250 died of radiation induced heart attacks.

In addition it should be noted that from the pregnant women irradiated by the Hiroshima and Nagasaki bursts only 30 fetuses subsequently developed mental disabilities after they were born and no physical deformities were noted. There have also been no significant birth problems in the years following the explosions as there was no residual radiation at either site, the initial radiations dissipating and decaying in the days and weeks following the bursts. ^[20]

See also

• Atomic bombings of Hiroshima and Nagasaki
• Little Boy
• The gadget
• Trinity test
• Thin Man nuclear bomb
• Fat Man and Little Boy, a 1989 film that reenacts the Manhattan Project
• List of nuclear weapons
• Manhattan Project

References

External links

• thorough descriptions of Gadget ("a great deal of tissue paper and Scotch tape were used to make everything fit snugly") and Fat Man at Nuclear Weapons Archive
• The Design of Gadget, Fat Man, and "Joe 1" (RDS-1)
• Fat Man Model in QuickTime VR format
• Naming of "Fat Man" & "Thin Man" after Churchill, Roosevelt
• The final bomb design, with pictures