FACTOID # 27: If you're itching to live in a trailer park, hitch up your home and head to South Carolina, where a whopping 18% of residences are mobile homes.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Little Boy
Little Boy

A post-war "Little Boy" model.
Type Nuclear weapon
Place of origin United States
Specifications
Weight 4,000 kg
Length 3.0 m
Diameter 0.7 m

Blast yield 13 to16 kilotons

Little Boy was the codename of the atomic bomb which was dropped on Hiroshima, on August 6, 1945 by the 12-man crew of the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets (Tibbets, age 92, died Nov. 1, 2007) of the United States Army Air Forces.[1] It was the first atomic bomb ever used as a weapon and was dropped three days before the "Fat Man" bomb was used against Nagasaki. A mockup of the Little Boy nuclear device, public domain photo from http://www. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Unit of energy commonly used to quantify laerge amounts of energy. ... A code name or cryptonym is a word or name used clandestinely to refer to another name or word. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... Main keep of Hiroshima Castle The city of Hiroshima (広島市; -shi) is the capital of Hiroshima Prefecture, and the largest city in the Chugoku region of western Honshu, the largest of Japans islands. ... is the 218th day of the year (219th in leap years) in the Gregorian calendar. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ... The Boeing B-29 Superfortress was a four-engine heavy bomber propeller aircraft flown by the United States Army Air Forces in World War II and other military organizations afterwards. ... Colonel Paul Tibbets waving from Enola Gays cockpit before the bombing of Hiroshima. ... Please see Colonel for other countries which use this rank Insignia of a United States Colonel Colonel is a rank of the United States armed forces. ... Colonel Paul Tibbets Jr. ... The United States Army Air Forces (USAAF) was the aviation component of the United States Army primarily during World War II. The title of Army Air Forces succeeded the prior name of Army Air Corps in June 1941 during preparation for expected combat in what came to be known as... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... Nagasaki ) ( ) is the capital and the largest city of Nagasaki Prefecture in Japan. ...


The weapon was developed during the Manhattan Project during World War II. It derived its explosive power from the nuclear fissioning of enriched uranium. The Hiroshima bombing was the second man-made nuclear explosion in history (the first was the "Trinity" test), and it was the first uranium-based detonation ever. Approximately 600 milligrams of mass were converted into energy. It exploded with a destructive power equivalent to between 13 and 16 kilotons of TNT (estimates vary) and killed approximately 140,000 people including associated effects. This article is about the World War II nuclear project. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... For the generation of electrical power by fission, see Nuclear power plant. ... These pie-graphs showing the relative proportions of uranium-238 (blue) and uranium-235 (red) at different levels of enrichment. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... It has been suggested that Nuclear explosive be merged into this article or section. ... The Trinity test was the first test of a nuclear weapon, conducted by the United States on July 16, 1945 at , thirty miles (48 km) southeast of Socorro on what is now White Sands Missile Range, headquartered near Alamogordo, New Mexico. ... This article is about the chemical element. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ...

Contents

Basic weapon design

Main articles: Gun-type fission weapon and Nuclear weapon design
The "gun" assembly method. When the hollow uranium projectile was driven onto the target spike, a nuclear explosion resulted.

The Mk I "Little Boy" was 10 feet (3 m) in length, 28 inches (71 cm) in diameter and weighed 8,900 lb (4000 kg). The design used the gun method to explosively force a hollow sub-critical mass of uranium-235 and a solid target spike together into a super-critical mass, initiating a nuclear chain reaction. This was accomplished by shooting one piece of the uranium onto the other by means of chemical explosives. It contained 64 kg of uranium, of which 0.7 kg underwent nuclear fission, and of this mass only 0.6 g became energy. Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the gun method: shooting one piece of sub-critical material into another. ... The first nuclear weapons, though large, cumbersome and inefficient, provided the basic design building blocks of all future weapons. ... Image File history File links Size of this preview: 730 × 350 pixelsFull resolution (730 × 350 pixel, file size: 33 KB, MIME type: image/gif) This drawing is a modification of the one uploaded by FastFission with URL http://commons. ... Image File history File links Size of this preview: 730 × 350 pixelsFull resolution (730 × 350 pixel, file size: 33 KB, MIME type: image/gif) This drawing is a modification of the one uploaded by FastFission with URL http://commons. ... Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the gun method: shooting one piece of sub-critical material into another. ... A sphere of plutonium surrounded by neutron-reflecting blocks of tungsten carbide. ... This article is about the chemical element. ... A schematic nuclear fission chain reaction. ... For the generation of electrical power by fission, see Nuclear power plant. ...


No full test of a gun-type nuclear weapon had occurred before the "Little Boy" device was dropped over Hiroshima. The only test explosion of a nuclear weapon had been of an implosion-type weapon using plutonium as its fissionable material, on July 16, 1945 at the Trinity test. There were several reasons for not testing the "Little Boy" device. Primarily, scarcity of uranium-235 compared with the relatively large amount of plutonium which, it was expected, could be produced monthly from the Hanford reactors. Additionally, the weapon design was conceptually simple enough that it was only deemed necessary to do laboratory tests with the gun-type assembly (known during the war as "tickling the dragon's tail"). Unlike the implosion design, which required very sophisticated coordination of shaped explosive charges, the gun-type design was considered almost certain to work without full testing. For other uses, see Hiroshima (disambiguation). ... Preparation for an underground nuclear test at the Nevada Test Site in the 1980s. ... This article is about the radioactive element. ... is the 197th day of the year (198th in leap years) in the Gregorian calendar. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ... The Trinity test was the first test of a nuclear weapon, conducted by the United States on July 16, 1945 at , thirty miles (48 km) southeast of Socorro on what is now White Sands Missile Range, headquartered near Alamogordo, New Mexico. ... Hanford Site plutonium production reactors along the Columbia River during the Manhattan Project. ... A sketch used by doctors to determine the amount of radiation to which each person in the room had been exposed during the excursion. ...


Although occasionally used in later experimental devices, the design was only used once as a weapon because of the extreme danger of accidental detonation. Little Boy's design was highly unsafe when compared to modern nuclear weapons, which incorporate many safety features, designed to anticipate various accident scenarios. The main design objectives of Little Boy were to create a nuclear weapon that was absolutely guaranteed to work. As a result, Little Boy incorporated only the most basic safety mechanisms, so an accidental detonation could easily occur during one or more of the following scenarios:

  • a simple crash could drive the "bullet" onto the "target" resulting in a massive release of radiation, or possibly nuclear detonation.
  • an electrical short circuit of some sort.
  • the danger of misfire was even greater over water. Even if the force of a crash did not trigger the bomb, the resulting leakage of water into the unprotected system could short it out, again possibly leading to accidental detonation. The British Red Beard nuclear weapon also suffered from this design flaw.
  • Fire.
  • Lightning strike.

None of the other five Mark I bombs built on the model of Little Boy were used by the U.S. Army. Ground out To make an electrical short-circuit to earth. ... A Red Beard weapon on its bomb trolley, fitted with a bomb-carrier prior to loading into a Canberra bomber. ... For other uses, see Fire (disambiguation). ... Not to be confused with lighting. ...


Assembly details

The exact specifications of the "Little Boy" bomb remain classified because they could still be used to create a viable nuclear weapon. Even so, many sources have speculated as to the design, relying on limited photographic evidence, interviews with former Manhattan Project personnel, and piecing together information from declassified sources to reconstruct its internal dimensions. A typical classified document. ...


According to the website Nuclear Weapon Archive,[2][3] 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 6.25 inches in diameter with a 4-inch-diameter hole in the middle, pressed together into a thin-walled canister 7 inches long. At detonation, it would be pushed down a short section of smooth-bore gun barrel by a tungsten carbide and steel plug. The target was a 4-inch-diameter solid spike, 7 inches long, with 40% of the total mass (25.6 kg). Made of a stack of 6 washer-like uranium rings somewhat thicker than the projectile rings, it was held in place by a 1-inch-diameter steel bolt that ran through the rings and out the front end of the bomb casing.


When the projectile and plug reached the target, the assembled super-critical mass of uranium would be completely surrounded by a tamper and neutron reflector of tungsten carbide and steel. Neutron generators at the base of the spike would be activated by the impact.


The projectile rings were delivered to Tinian Island on July 26, 1945, by the cruiser USS Indianapolis. The target rings arrived two days later by air. is the 207th day of the year (208th in leap years) in the Gregorian calendar. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ... USS Indianapolis (CA-35) was a Portland-class heavy cruiser of the United States Navy. ...

Image File history File links Size of this preview: 653 × 600 pixelsFull resolution (735 × 675 pixel, file size: 51 KB, MIME type: image/gif) This drawing is a modification of the one uploaded by FastFission with URL http://commons. ...

Counter-intuitive design

For the first fifty years after 1945, every published description and drawing of the Little Boy mechanism assumed that a small, solid projectile was fired into the center of a larger target.[3]


Critical mass considerations dictated that in Little Boy the larger, hollow piece would be the projectile. For the assembled fissile core to have more than two critical masses of U-235, one of the two pieces would need to have more than one critical mass, and to avoid criticality by means of shape, namely a hole in the middle. The larger (outer) surface area allows more fission neutrons to escape and hence not cause a new fission.


It was also important for the larger piece to have minimal contact with the tamper of neutron-reflecting tungsten carbide until the moment of detonation. As the projectile, it would have only its back end in contact with tungsten carbide (see drawing above). The rest of the tungsten carbide could be installed around the target spike, called the "insert" by designers, where an air space would keep it away from the sides of the insert. This is the only way to pack the maximum amount of fissile material into a gun-assembly design.[4]


Physical effects of the bomb

Hiroshima was spared conventional bombing in order to serve as a pristine target, one where the effects of a nuclear bomb on a previously undamaged city could be observed. While damage could be studied later, the energy yield of the untested Little Boy design could be determined only at the moment of detonation, using instruments dropped by parachute from a plane flying in formation with the one that dropped the bomb. Radio-transmitted data from these falling instruments indicated a yield of about a dozen kilotons.


Comparing this yield to the observed damage produced a rule of thumb called the 5 psi (pounds per square inch) lethal area rule. The number of prompt fatalities will approximately equal the number of people inside the lethal area.


The damage came from three main effects: blast, fire, and radiation.[5]


Blast

The blast from a nuclear bomb is the result of x-ray-heated air (the fireball) sending a shock/pressure wave in all directions at the speed of sound, analogous to thunder generated by a bolt of lightning. Studies of Little Boy at Hiroshima have given us most of what we know about urban blast destruction from nuclear weapons. Nagasaki was less useful in that respect because hilly terrain deflected the blast and generated a more complicated pattern of destruction.

Frame house in 1953 nuclear test, 5 psi overpressure.
Frame house in 1953 nuclear test, 5 psi overpressure.

At Hiroshima, severe structural damage to buildings extended about one mile in every direction from ground zero, making a circle of destruction two miles in diameter. There was little or no structural damage outside a two-mile radius. At one mile, the force of the blast wave was 5 psi, with enough duration to implode houses and reduce them to kindling as it passed. 5 psi is 720 pounds per square foot. Image File history File links Size of this preview: 800 × 600 pixelsFull resolution‎ (1,024 × 768 pixels, file size: 308 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 800 × 600 pixelsFull resolution‎ (1,024 × 768 pixels, file size: 308 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ...


Later test explosions of nuclear weapons, with houses and other test structures placed nearby, confirmed that 5 psi is an important threshold figure. Ordinary urban buildings close enough to experience it will be crushed, toppled, or gutted by the force of air pressure. The picture at right shows the effects of a nuclear-bomb-generated 5 psi pressure wave on a test structure in Nevada in 1953.


The most important effect of this kind of structural damage was that it created fuel for a firestorm. For this reason, the 5 psi contour defines the lethal area for blast and fire.


Fire

The first effect of a nuclear explosion is blinding light, accompanied by radiant heat from the fireball. (The Hiroshima fireball was 1200 feet in diameter.) Near ground zero, everything flammable burst into flame, including human flesh. One famous, anonymous Hiroshima victim left only a shadow, permanently etched into stone steps near a bank building.[6]

Hiroshima blast and fire damage, U.S. Strategic Bombing Survey map.

Some of the fires started by the fireball's heat were probably blown out by the following blast wave. The blast wave would have started additional fires through overturned stoves, wrecked vehicles, electrical shorts, etc. These numerous small fires quickly merged into a single firestorm which consumed everything inside the 5 psi lethal area. Image File history File links Size of this preview: 629 × 600 pixelsFull resolution‎ (1,024 × 976 pixels, file size: 449 KB, MIME type: image/gif) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 629 × 600 pixelsFull resolution‎ (1,024 × 976 pixels, file size: 449 KB, MIME type: image/gif) File historyClick on a date/time to view the file as it appeared at that time. ...


The Hiroshima firestorm was thus two miles in diameter, corresponding closely to the severe blast damage zone. (See the USSBS[7] map, right.) Blast-damaged buildings provided ideal fuel for the fire. Structural lumber and furniture were splintered and scattered about. Debris-choked roads prevented entry by fire fighters. Broken gas pipes fueled the fire, and broken water pipes rendered hydrants useless.


As the map shows, the firestorm easily jumped the natural firebreaks (river channels) as well as prepared firebreaks. The spread of fire stopped only when it reached the edge of the blast-damaged area and ran out of easily available fuel.


Accurate casualty figures are impossible because so many victims were cremated by the firestorm. For the same reason, the portion of firestorm victims who survived the blast and died of fire can never be known. Casualty figures are based on estimates of how many people were inside the lethal area when the bomb went off.


Radiation

Because Little Boy was detonated 1900 feet above the ground, as an air burst, there was no bomb crater and no local radioactive fallout.[8] Local Fallout is dust and ash from a bomb crater, contaminated with radioactive fission products. It falls back to the ground downwind of the crater and can easily produce, with radiation alone, a lethal area much larger than that from blast and fire. With an air burst, the fission products remain in aerosol form until they rise into the stratosphere, where they dissipate and become part of the global, rather than the local, environment.


However, an intense flux of neutron and gamma radiation came directly from the fireball. Most people close enough to receive lethal doses of that direct radiation died in the firestorm before their radiation injuries could become apparent. But survivors on the edge of the lethal area and beyond suffered injuries from radiation as well as from blast and fire.


Some temporary survivors died soon afterward of acute radiation illness, but most of the radiation effects show up statistically, as increases in cancer rates, birth defects, etc., over the lifetimes of the survivors and their descendants.


Development of the bomb

Uranium for "Little Boy" was enriched in calutrons and by gaseous diffusion at Oak Ridge, Tennessee.
Uranium for "Little Boy" was enriched in calutrons and by gaseous diffusion at Oak Ridge, Tennessee.
Main article: Manhattan Project

The "Little Boy" bomb was constructed through the Manhattan Project during World War II. Because enriched uranium was known to be fissionable, it was the first approach to bomb development pursued. The vast majority of the work in constructing "Little Boy" came in the form of the isotope enrichment of the uranium necessary for the weapon. Enrichment at Oak Ridge, Tennessee began in February 1943, after many years of research. Download high resolution version (1417x1087, 847 KB)Alpha Track Calutron at the Y-12 Plant at Oak Ridge, Tennessee from the Manhattan Project, used for uranium enrichment. ... Download high resolution version (1417x1087, 847 KB)Alpha Track Calutron at the Y-12 Plant at Oak Ridge, Tennessee from the Manhattan Project, used for uranium enrichment. ... Schematic diagram of uranium isotope separation in the calutron. ... Oak Ridge is an incorporated city in Anderson and Roane Counties in East Tennessee, about 25 miles northwest of Knoxville. ... This article is about the World War II nuclear project. ... This article is about the World War II nuclear project. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... // Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. ... Oak Ridge is an incorporated city in Anderson and Roane Counties in East Tennessee, about 25 miles northwest of Knoxville. ...


The development of the first prototypes and the experimental work started in early 1943, at the time when the Los Alamos Design Laboratory became operational in the framework of the Manhattan Project. Originally gun-type designs were pursued for both a uranium and plutonium weapon (the "Thin Man" design), but in April 1944 it was discovered that the spontaneous fission rate for plutonium from the Hanford enrichment plant was too high to use in a gun-type weapon. In July 1944, almost all research at Los Alamos re-oriented around the development of the implosion plutonium weapon. In contrast, the uranium bomb was almost trivial to design. Los Alamos National Laboratory, aerial view from 1995. ... The Thin Man (formally, Mark 2) nuclear bomb was a proposed plutonium gun-type nuclear bomb which the United States was developing during the Manhattan Project. ...

As part of Project Alberta, Commander A. Francis Birch (left) numbers the bomb while physicist Norman Ramsey watches. This is one of the rare photos where the inside of the bomb can be seen.
As part of Project Alberta, Commander A. Francis Birch (left) numbers the bomb while physicist Norman Ramsey watches. This is one of the rare photos where the inside of the bomb can be seen.

With plutonium found unsuitable for the gun-type design, the team working on the gun weapon (led by A. Francis Birch), faced another problem: the bomb was simple, but they lacked the quantity of uranium-235 necessary for its production. Enough fissile material was not going to be available before mid-1945. Despite this, Birch managed to convince others that this concept was worth pursuing, and that in case of a failure of the plutonium bomb, it would still be possible to use the gun principle. His team had heavy responsibilities and even though the technology was less complex than for the other project, a lot of rigorous work was still needed. In February 1945, the specifications were completed (model 1850). The bomb, except for the uranium payload, was ready at the beginning of May 1945. Image File history File links Atombombe_Little_Boy. ... Image File history File links Atombombe_Little_Boy. ... Project Alberta was a section of the U.S. Army Air Force and Manhattan Project which developed the actual combat delivery of the first atomic bombs onto the Empire of Japan during World War II. Much of its work consisted in training a crew for preparation of the atomic bombing... Norman Foster Ramsey, Jr. ...


Most of the uranium necessary for the production of the bomb came from the Shinkolobwe mine and was made available thanks to the foresight of the CEO of the High Katanga Mining Union, Edgar Sengier, who had 1000 tons of uranium ore transported to a New York warehouse in 1939. A small amount may have come from a captured German submarine, U-234, after the German surrender in May 1945. The majority of the uranium for Little Boy was enriched in Oak Ridge, Tennessee, primarily by means of electromagnetic separation in calutrons and through gaseous diffusion plants, with a small amount contributed by the cyclotrons at Ernest O. Lawrence's Radiation Laboratory. The core of Little Boy contained 64 kg of uranium, of which 50 kg were enriched to 89%, and the remaining 14 kg at 50%. With enrichment averaging 80%, it could reach about 2.5 critical masses. "Fat Man" and the Trinity "gadget", by way of comparison, had five critical masses. Shinkolobwe mine Shinkolobwe is the name of a town and a mine in the Katanga province of the Democratic Republic of the Congo, located near the larger town of Likasi. ... This article needs to be wikified. ... Edgar Sengier (1879—July 26, 1963) was the director of the Belgian Union Minière du Haut Katanga during World War II. Sengier is credited with giving the American government access to the uranium necessary for the Manhattan Project. ... Unterseeboot 234 (U-234) was a WWII German Type X submarine (U-boat), designed as a mine-layer, whose first and only mission into enemy territory consisted of the attempted delivery of uranium and other German advanced weapons technology to the Empire of Japan. ... Schematic diagram of uranium isotope separation in the calutron. ... A pair of Dee electrodes with loops of coolant pipes on their surface at the Lawrence Hall of Science. ... Ernest Orlando Lawrence (August 8, 1901 - August 27, 1958) was an American physicist and Nobel laureate best known for his invention of the cyclotron. ... The Berkeley Lab is perched on a hill overlooking the Berkeley central campus and San Francisco Bay. ... For other uses of critical mass, see critical mass (disambiguation). ... The gadget, partially assembled on the shot tower for the Trinity test. ...


Construction and delivery

Little Boy in the bomb pit on Tinian, before being loaded into Enola Gay's bomb bay. A section of the bomb bay door is visible on the top right
Little Boy in the bomb pit on Tinian, before being loaded into Enola Gay's bomb bay. A section of the bomb bay door is visible on the top right

On July 14, 1945 a train left Los Alamos carrying several "bomb units" (the major non-nuclear parts of a gun-type bomb) together with a single completed uranium projectile; the uranium target was still incomplete. The consignment was delivered to the San Francisco Naval Shipyard at Hunters Point in San Francisco, California[2]. There, two hours before the successful test of Little Boy's plutonium-implosion brother at the Trinity test in New Mexico, the bomb units and the projectile were loaded aboard the heavy cruiser USS Indianapolis. Indianapolis steamed, at a record pace, to the airbase at Tinian island in the Mariana Islands, delivering them ten days later on the 26th. While returning from this mission Indianapolis was sunk by a Japanese submarine, with great loss of life due to shark attacks. Also on the 26th the three sections of the uranium target assembly were shipped from Kirtland Air Force Base[2] near Albuquerque, New Mexico in three C-54 Skymaster aircraft operated by the 509th Composite Group's Green Hornet squadron[9] [10]. With all the necessary components delivered to Tinian, bomb unit L11 was chosen, and the final Little Boy weapon was assembled and ready by August 1[2]. Image File history File links Atombombe_Little_Boy_2. ... Image File history File links Atombombe_Little_Boy_2. ... is the 195th day of the year (196th in leap years) in the Gregorian calendar. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ... The San Francisco Naval Shipyard was a United States Navy shipyard in San Francisco, California, located on 638 acres (2. ... Hunters Point or Bayview-Hunters Point is a neighborhood in the southeastern portion of San Francisco, California. ... San Francisco redirects here. ... The Trinity test was the first test of a nuclear weapon, conducted by the United States on July 16, 1945 at , thirty miles (48 km) southeast of Socorro on what is now White Sands Missile Range, headquartered near Alamogordo, New Mexico. ... USS Indianapolis (CA-35) was a Portland-class heavy cruiser of the United States Navy. ... Saipan, Tinian & Aguiguan The atom bomb pit on Tinians North Field, where Little Boy was loaded aboard the Enola Gay Tinian Shinto shrine. ... The Mariana Islands (also the Marianas; up to the early 20th century sometimes called Ladrones Islands, from Spanish Islas de los Ladrones meaning Islands of Thieves) are an archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels... Kirtland Air Force Base is located in the southeast quadrant of Albuquerque, New Mexico, adjacent to the Albuquerque International Sunport. ... “Albuquerque” redirects here. ... The Douglas C-54 Skymaster was a four-engined transport aircraft used by the United States Army Air Force in World War II. Like the C-47 Skytrain, the C-54 Skymaster was derived from a civilian airliner (the DC-4). ... The 509th Composite Group was an air combat unit of the United States Army Air Forces during the Second World War and as the 509th Operations Group, is a current unit of the United States Air Force. ... is the 213th day of the year (214th in leap years) in the Gregorian calendar. ...


Handling the completed Little Boy was particularly dangerous. Once cordite was loaded in the breech, any firing of the explosive would at worst cause a nuclear chain reaction and at best a contamination of the explosion zone. The mere contact of the two uranium masses could have caused an explosion with dire consequences, from a simple "fizzle" explosion to an explosion large enough to destroy Tinian (including the 500 B-29s based there, and their supporting infrastructure and personnel). Water was also a risk, since it could serve as a moderator between the fissile materials and cause a violent dispersal of the nuclear material. The uranium projectile could only be inserted with an apparatus that produced a force of 300,000 newtons (67,000 lbf, over 30 tons). For safety reasons, the weaponeer, Captain William Sterling Parsons, decided to load the bags of cordite only after take-off. A schematic nuclear fission chain reaction. ... Captain Parsons in 1945 Rear Admiral William Sterling Deak Parsons (November 26, 1901 - December 5, 1953) was an American military engineer, best known for being the weaponeer on the Enola Gay (at the time, he had the rank of Captain) which dropped the first atomic bomb on the Hiroshima, Japan...


Fuse system

The bomb employed a fuse system worthy of a device whose total development cost was approximately $1,000,000,000 ($11 billion in 2006 dollars) to build, and was designed to detonate at the most destructive altitude. Calculations showed that for the largest destructive effect, the bomb should explode at an altitude of 580 meters. The resultant fuse design was a three-stage interlock system:

  • A timer ensured that the bomb would not explode until at least fifteen seconds after release, one-quarter of the predicted fall rate, to ensure safety of the aircraft. The timer was activated when the electrical pullout plugs connecting it to the airplane were pulled loose by the drop of the bomb, switching it to internal (24V battery) power and starting the timer. At the end of the 15 seconds the batteries then powered the radar system and passed on responsibility to a barometric stage.
  • The purpose of the barometric stage was to delay activating the final radar altimeter firing command circuit until near detonation altitude. A thin metallic membrane was gradually deformed as ambient air pressure increased during descent. The barometric fuse was not in itself considered accurate enough to be used to detonate the bomb at the precise ignition height, because air pressure varies with local weather conditions. When the bomb reached the design height for this stage (reportedly 2,000 meters) the membrane closed a circuit, activating the circuit between the radar altimeter and the projectile gun. The barometric stage was added because of a worry that radar signals from external sources might detonate the bomb too early to be effective.
  • The doubly-redundant radar system employed four radar altimeters that independently detected altitude directly from radar reflections off the ground. When any two of the four altimeters sensed the correct height, the firing switch closed, igniting the cordite charge. This launched the uranium projectile towards the other end of the gun barrel at an eventual muzzle velocity of ~300 meters per second. Approximately 10 milliseconds later the chain reaction took place, lasting less than 1 μs.

Schematic drawing of a simple mercury barometer with vertical mercury column and reservoir at base A barometer is an instrument used to measure atmospheric pressure. ... In engineering, the duplication of critical components of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe, is called redundancy. ... A guns muzzle velocity is the speed at which the projectile leaves the muzzle of the gun. ...

The bombing of Hiroshima

The mushroom cloud over Hiroshima after the dropping of "Little Boy".
The mushroom cloud over Hiroshima after the dropping of "Little Boy".

The bomb was armed in flight 9600 m (31,000 feet) above the city, then dropped at approximately 8:15 a.m. (JST). The detonation happened at an altitude of 580 m (1900 feet). With a power of 13 to 16 kilotons, it was less powerful than "Fat Man," which was dropped on Nagasaki (21–23 kt). The official yield estimate of "Little Boy" was about 15 kilotons of TNT equivalent in explosive force, i.e. 6.3 × 1013 joules = 63 TJ (terajoules)[11]. However, the damage and the number of victims at Hiroshima were much higher, as Hiroshima was on flat terrain, while the hypocenter of Nagasaki lay in a small valley. Image File history File links Description: At the time this photo was made, smoke billowed 20,000 feet above Hiroshima while smoke from the burst of the first atomic bomb had spread over 10,000 feet on the target at the base of the rising column. ... Image File history File links Description: At the time this photo was made, smoke billowed 20,000 feet above Hiroshima while smoke from the burst of the first atomic bomb had spread over 10,000 feet on the target at the base of the rising column. ... The atomic bombing of Nagasaki, Japan on August 9, 1945 A mushroom cloud is a distinctive mushroom-shaped cloud of smoke, flame, or debris resulting from a very large explosion. ... For other uses, see Hiroshima (disambiguation). ... Colonel Paul Tibbets waving from Enola Gays cockpit before the bombing of Hiroshima. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... // The explosive yield of a nuclear weapon is the amount of energy discharged when the weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene (TNT), either in kilotons (thousands of tons of TNT) or megatons (million of tons of TNT), but sometimes also in terajoules (1 kiloton of... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ... The joule (IPA: or ) (symbol: J) is the SI unit of energy. ... tera- (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000. ... The hypocenter or hypocentre (literally: below the center from the Greek υπόκεντρον), may refer to the site of an earthquake or to that of a nuclear explosion. ...


Approximately 70,000 people were killed as a direct result of the blast, and a similar number were injured. A great number more later died as a result of nuclear fallout and cancer.[12] Unborn babies died or were born with deformities.[13] Fallout is the residual radiation hazard from a nuclear explosion, so named because it falls out of the atmosphere into which it is spread during the explosion. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...


Recent studies point to different conclusions, based on results of studies conducted by American and Japanese researchers since the war. Data collected for over 86,000 people suggests that roughly 700 people died from long-term effects of radiation in Hiroshima, significantly less than the over 100,000 cited in numerous previously published sources.Spiegel


The success of the bombing was reported with great enthusiasm in the United States. See Atomic bombings of Hiroshima and Nagasaki for discussion of contemporary opposition to the bombings, on both moral and military grounds. The mushroom cloud over Hiroshima after the dropping of Little Boy. ...


See also

Colonel Paul Tibbets waving from Enola Gays cockpit before the bombing of Hiroshima. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... This article is about the World War II nuclear project. ... The Trinity test was the first test of a nuclear weapon, conducted by the United States on July 16, 1945 at , thirty miles (48 km) southeast of Socorro on what is now White Sands Missile Range, headquartered near Alamogordo, New Mexico. ... The gadget, partially assembled on the shot tower for the Trinity test. ... The mushroom cloud over Hiroshima after the dropping of Little Boy. ... This is a list of nuclear weapons ordered by state and then type within the states. ... The mushroom cloud from Upshot-Knothole Grable, with the cannon it was fired from in the foreground. ...

References

  1. ^ The name Little Boy is alleged on a BBC web site to be a reference to former President Roosevelt.
  2. ^ a b c d Much of this account is taken from the description of the "Little Boy" by Carey Sublette in Section 8 of his "Nuclear Weapons Frequently Asked Questions", available online at http://nuclearweaponarchive.org/Nwfaq/Nfaq8.html.
  3. ^ a b The most recent updates come from John Coster-Mullen's Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man, 2003 (first printed in 1996), a self-published account based largely on oral histories but which contains, in its extensive appendix, a declassified U.S. government document detailing the exact mass and configuration of the U-235 rings.
  4. ^ This information appeared in 2002 in Racing for the Bomb, by Robert S. Norris, Steerforce Press, p. 409, with the 2001 printing of John Coster-Mullen's Atom Bombs, p. 24, cited as its source.
  5. ^ Samuel Glasstone and Philip Dolan, The Effects of Nuclear Weapons, Third Edition, 1977, U.S. Dept of Defense and U.S. Dept of Energy.
  6. ^ Photograph in the Hiroshima Peace Memorial Museum."Photo"
  7. ^ http://www.anesi.com/ussbs01.htm United States Strategic Bombing Survey (Pacific War), 1 July 1946, pp. 22-25.
  8. ^ Glasstone and Dolan, The Effects of Nuclear Weapons, p. 409. "An air burst, by definition, is one taking place at such a height above the earth that no appreciable quantities of surface material are taken up into the fireball. . . the deposition of early fallout from an air burst will generally not be significant. An air burst, however, may produce some induced radioactive contamination in the general vicinity of ground zero as a result of neutron capture by elements in the soil."
  9. ^ "Victory", Los Alamos National Laboratory's history of the atomic bomb project
  10. ^ "The Story of the Atomic Bomb", USAF Historical Studies Office
  11. ^ Los Alamos National Laboratory report LA-8819, The yields of the Hiroshima and Nagasaki nuclear explosions by John Malik, September 1985. Available online at http://www.mbe.doe.gov/me70/manhattan/publications/LANLHiroshimaNagasakiYields.pdf
  12. ^ The Manhattan Engineer District, United States Army (1946-06-29). Chapter 10 - Total Casualties. The Atomic Bombings of Hiroshima and Nagasaki. The Avalon Project at Yale Law School. Retrieved on 2007-03-19. This is a 1946 U.S. Army report of unclassified information, republished by the Avalon project of the Yale Law School, USA.
  13. ^ Centers for Disease Control and Prevention (2005-03-23). Prenatal Radiation Exposure: A Fact Sheet for Physicians. CDC Emergency Preparedness & Response web site. Retrieved on 2007-03-19. This document gives information about likely injury from prenatal radiation exposure. It does not include any information about injuries at Hiroshima directly. It does cite two report on Hiroshima injuries.

Hiroshima Peace Memorial Museum is located in Hiroshima Peace Memorial Park, in central Hiroshima. ... is the 182nd day of the year (183rd in leap years) in the Gregorian calendar. ... Year 1946 (MCMXLVI) was a common year starting on Tuesday (link will display full 1946 calendar) of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 78th day of the year (79th in leap years) in the Gregorian calendar. ... The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, is recognized as the leading United States agency for protecting the public health and safety of people. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 82nd day of the year (83rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 78th day of the year (79th in leap years) in the Gregorian calendar. ...

External links

Wikimedia Commons has media related to:


Image File history File links Commons-logo. ... Hiroshima Peace Memorial Museum is located in Hiroshima Peace Memorial Park, in central Hiroshima. ...


  Results from FactBites:
 
Little Boy and Fat Man nuclear weapons (181 words)
Little Boy was the first nuclear weapon used in warfare.
Little Boy was dropped from a B-29 bomber piloted by U.S. Army Air Force Col. Paul W. Tibbets.
While Little Boy was a uranium gun-type device, Fat Man was a more complicated and powerful plutonium implosion weapon that exploded with a force equal to 20 kilotons of TNT.
Little Boy: The Arts of Japan's Exploding Subculture (kottke.org) (227 words)
Some friends and I recently went and checked out the Little Boy exhibit at the Japan Society.
Little Boy: The Arts of Japan's Exploding Subculture explores the culture of postwar Japan through its arts and popular visual media, from the perspective of one of Japan's most celebrated artists.
Focusing on the phenomenally influential subcultures of otaku (roughly translated as "pop cult fanaticism") and its relationships to Japan's artistic vanguard, Takashi Murakami explores the historical influences that shape Japanese contemporary art and its distinct graphic idioms.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m