The ATOMIC Bombing of Hiroshima & Nagasaki Detailed 3D Model Breakdown!

The ATOMIC Bombing of Hiroshima & Nagasaki Detailed 3D Model Breakdown!

With the defeat of Germany on May 8th of 1945, the United States was in a precarious situation. Even with the steady destruction of its empire, Japan simply wouldn’t surrender. The United States had two options. Mobilize over 2 million men and invade the Japanese home islands, incurring nearly 1 million casualties and adding two years to the war, or use one of the most destructive, technologically sophisticated weapons known to man. America chose the latter. On August 6th of 1945, the Anola Gay left the northern Mariana Islands. Inside was a 15 kiloton guntype fusion weapon loaded with over 145 pounds of highly radioactive uranium. Its name was Little Boy. 6 hours later at the height of 31,000 ft, the first atomic bomb was dropped over the city of Hroshima with catastrophic consequences. But how exactly did the Little Boy atomic bomb work? What were the parts and mechanisms of the first nuclear bomb? What processes did it undergo during its detonation? Why was Hiroshima targeted? How big was the blast zone? How much of the city was destroyed? And most importantly, how many Japanese casualties were incurred when the first American atomic bomb reached its destination? Why was Hiroshima targeted? The target selection was subject to the following criteria. Number one, the target had to be larger than 4.8 km or 3 mi in diameter and was an important target in a large city. Number two, the target would have to allow the blast wave to create effective damage. Number three, the target was unlikely to be attacked by August 1945. When deciding which Japanese cities US war planners would target, there were five options. Kukura, the site of one of Japan’s largest munitions plants. Hiroshima, an imarctation port and industrial center that was a site of a major military headquarters. Yokohama, an urban center for aircraft manufacturing, machine tools, docks, electrical equipment, and oil refineries. Nagata, a port with industrial facilities, including steel and aluminum plants, and Coyoto, a major industrial center. These cities were largely untouched during nightly bombing raids, and the Air Force agreed to leave him off the target list so an accurate assessment of the damage caused by the atomic bombs could be made. [Music] Hiroshima was ultimately chosen for the following reasons. Number one, it was an important army depot and port of impartation in the middle of an urban industrial area. Number two, it was a good radar target and it was such a size that a large part of the city could be extensively damaged. There were adjacent hills around the city which would considerably increase the blast damage. But if you’re interested in blast The mission begins at 5:55 a.m. Tennant in time with the Anola arriving over the island of Euima, circling at 8,000 ft while waiting for two escorting super fortresses to catch up. Each aircraft has a critical role to play in the mission. The Anola Gay will deliver the weapon while the Great Artiste piloted by Major Charles Sweeney is carrying blast measurement instrumentation to determine the yield of the explosion. Necessary evil piloted by Captain George Marque will observe and photograph the results of the mission when all three aircrafts have renoved over Evoima. The superfortresses continue towards Japan while awaiting the weather report. An hour and 20 minutes later, at 7:15 a.m., second Lieutenant Morals Jeepson climbs into the Inola Gay’s bomb bay and pulls three green safety plugs out of the bomb, which have been put there to prevent straight electrical current from prematurely detonating the weapon. He replaces the plugs with new red ones to arm the bomb before informing Colonel Tippets that Little Boy is ready for deployment. Tippets pressurizes the aircraft and begins a slow climb to 32,700 ft while the crew put on flex suits and parachutes. All three reconnaissance aircraft arrive over their targets precisely at 809 a.m. 15 minutes later straight flush circling over Hiroshima is the first to report back sending a coded message to the Yola gay which reads cloud cover less than 3/10 at all altitudes advice bomb primary. Tibbitz once again turns on the intercom and informs his crew that it’s Hiroshima. A one-word message is sent back to the squadron security chief on Iima primary. The Japanese defenses in the city sound an air raid warning, but the residents on the ground are hardly concerned about a single B29. American aircraft have overflown the city plenty of times without attacking. The warning is lifted soon after and life in Hroshima goes on as normal. At 9:05 a.m., the Nola’s navigator, Major Theodore Vancerk, informs Colonel Tippets that they’re 10 minutes from the target. The aircraft is flying at 31,000 ft when the city comes into view, and Tippets prepares for his bombing run. Cloud cover is just 10%, far better than the minimum visibility of 30% required for the mission. At 9:12 a.m., control over the aircraft is handed over to Bombadier Major Thomas Farbee, and Tibbitz orders his crew to dawn dark Polaroid glasses to protect their eyes from the flash of the explosion. A radio Hiroshima operator reports three aircraft in the skies above the city. Another air raid warning goes out. However, the warning is too late to allow any Japanese interceptors to scramble and Japanese anti-aircraft batteries can hit the super fortresses to such high altitudes. The aiming point for the bomb, the Iowa Bridge, comes into view at 9:14 a.m. The bomader calls out, “I’ve got it.” Little boy has been said to air burst over the aim point to cause as much damage as possible. The bomber continues to advance on his target. 58 seconds later, he shouts, “Bomb away, and the 9700lb little boy atomic bomb drops free to the target. To understand how little boy works, we first need to understand the parts of the nuclear weapon. Located at the back of the weapon are the boxtail fins that stabilize the bomb when dropped from the air. Inside are three electric gun primers which are the devices responsible for initiating the conventional charge that will push this projectile with an explosive force. Located here is the projectile tungsten carbide disc. And the most important part is the uranium 235 hollow projectile rings. The projectile ring slugs are hollowed and designed for the target rings to enter. They weigh around 89 lb while the front uranium target rings weigh around 56 lb. Altogether the bomb contains around 145 lbs of highly radioactive uranium. All these mechanisms and parts are encased in a 6.5 in smooth boore gun barrel. At the nose of the bomb is the impact absorbing anvil and just above it sits the tungsten carbide plug which contains four pelonium initiators. The palonium initiators ensure a nuclear chain reaction occurs when the bomb is dropped. On the surface of the atomic bomb or barometric sensing ports and manifolds. The barometer identifies the precise altitude for detonation. Once the required altitude is reached, the barometer activates Archie fusing radar altimeters, which are these curvylooking objects that prime the bomb for detonation. Now, let’s take a look at how this nuclear bomb works in basic step-by-step format. Step number one, before the bomb is dropped, all three arming plugs are pulled one after another. Step number two, the Bombay doors open and the bomb falls due to gravity. When released, its internal 24volt battery starts a timer. After 15 seconds, the bomb will be approximately 3600 ft from the aircraft. Step number three, multiple radar altimeters are activated located at the front of the bomb. The barometric stage was added because of a worry that external radar signals might detonate the weapon too early. After activation, the barometer senses the desired height of around 580 m or,900 ft as the Little Boy bomb was designed to be an air burst. Step number four, to ensure accurate detection of the bomb’s final altitude, multiple radar altimeters were utilized. This process involves measuring the altitude above the ground and beneath the bomb through the timing of radio wave travel and reflection. Once the correct height was sensed, the firing switch activates. Step number five, the firing switch ignites three Navy gun primers in the brereech plug. Step number six, the three Navy gun primers set off an explosive charge consisting of four silk powder bags, each containing 2 lb of cordite. Step number seven, the explosive charge launches the uranium projectile at 300 m/s. Step number eight, four palonium initiators placed on tungsten carbide initiate nuclear reactions. Step number nine, this is where nuclear fision happens. An airburst detonation delivered from a single little boy atomic warhead with a yield of 15 kilotons over the city of Hiroshima had catastrophic consequences. [Music] Upon detonation, an immensely hot and luminous fireball was formed, expanding to a radius of 200 m, vaporizing everything in its path. Those near the blast were evaporated and within a 340 m radius, all buildings were destroyed, killing 16,000 Japanese civilians in a matter of seconds. Very soon after detonation, multiple destructive blast waves developed, moving rapidly away from the fireball. The extreme radiation zone had a radius of 1.2 km. Here, Japanese civilians received a 500 rim ionizing radiation dose, which was likely fatal in around 1 month’s time. 15% of survivors would eventually die of cancer due to radiation exposure. Within a 1.7 km radius, the shock wave emitted was measured at 5 psi, also known as a moderate damage blast zone. Here, most residential buildings collapsed, injuries were universal, and fatalities were widespread. Most commercial and residential fires started within this area with damaged buildings spreading fire throughout the city. Within a 1.9 km radius, due to the bomb’s extremely high temperature, the shock wave emitted contained high levels of thermal radiation, causing thirdderee burns and clothing to instantly ignite into flames. Thirdderee burns extended throughout the layers of skin and were often painless due to the destruction of pain nerves. This left many with severe scarring or disablement and in severe cases often required amputation to burn limbs. As a result, around half the people between 340 m and 2 km from the blast were killed from debris, smoke collapsed buildings and radiation sickness, which translated roughly to an additional 67,000 Japanese fatalities over a period of 60 seconds. Within a 1.9 km radius, was the light blast damage zone. Here, damage was caused by shocks similar to those produced by a thunderclap or a sonic boom, but with much more force. Although some windows were broken over 10 miles away, the injuries associated with flying glass generally occurred at over pressures of around 1 PSI. This damage corresponded to a distance of around 3 mi or 4.8 km from ground zero for a 15 koton nuclear explosion. The damage in this area of Hiroshima vary widely as shock waves were bounded multiple times off buildings, terrain, and even atmosphere. As first responders moved inward, windows and doors were blown in and gutters, window shutters, roofs, and lightly constructed buildings had increasing damage. Litter and rubble increased moving towards ground zero. And there was increasing numbers of stalled and crashed automobiles that made emergency vehicle passage difficult, raising the total death tally to 97,000 over a period of 60 seconds with an additional 155,000 injured as well. [Music] [Music] Heat [Music] [Music] up here. Though many military analysts believe that one nuclear detonation over a large populated area would be enough to bring a swift end to the Second World War, Japan was determined to fight on. Meanwhile, a second atomic bomb cenamed Fat Man was ready for use. With no sign from the Japanese government, the decision has been made to attack another city. This time, the primary targets will be Kakura and the secondary target will be Nagasaki. The mission begins similarly to the attack on Hiroshima as two weather reconnaissance B29s were sent out to scout the targets early in the morning. The Anola Gay is back in the air to gauge conditions over Kakura while Major Charles Sweeney will poll the delivery aircraft, a B29 called Boxcar. However, during pre-flight checks, it had been discovered that the fuel pump for one of the reserve tanks had malfunctioned, which significantly cut the amount of time the B29 can remain in the air. After a short discussion, the decision was made to continue with the mission. At 3:47 a.m., Boxcar and its support aircraft, the Great Artis and Big Stink, lifted off Tenin Island and made their way toward the Rhonda View point at Yakushima Island. Unlike the mission 3 days prior, this operation was far from smooth. 2 hours into the flight, a red warning light on Fatman’s fuse monitor unexpectedly starts flashing, which indicates that some of the bomb’s fuses have been activated. Fearing the bomb is about to detonate on its own, weapon specialist Frederick Asworth goes to investigate and discovers that ground technicians accidentally misaligned two circuit switches. Ashworth quickly resolves the issue and every man on the aircraft breathes a sigh of relief. When Boxcar arrives at Yakushima Island at 9:10 a.m., the great artist soon joins, but not the Big Stink. Despite being told to wait no longer than 15 minutes, Major Sweeney circles for another 40 minutes, waiting for the final B29. Unfortunately, the Big Stink got lost in dense clouds and won’t make it to the rende viewpoint. After receiving word from the Inola Gay that weather above Kakura offers enough visibility for a bomb run, Sweenie decides to proceed with the mission and sets course for Kakura. At 9:50 a.m., Batman is armed and the crew prepares themselves for the climactic moment ahead. Meanwhile, weather conditions begin to deteriorate over Kakura just as the Enola Gay has left the area. Worse yet, Japanese offenses are put on high alert after the departure of the weather aircraft, which will make the mission more difficult. Box car and the great Artis arrive over Kakura at 9:44 a.m. to find the city shrouded in clouds and dense dark smoke. The aircraft initiate a bombing run, but the bomader, Captain Kermit, reports to Sweeney that he can’t find the aim point through the clouds and dense smoke. Sweeney has been strictly ordered to bomb visually rather than using unreliable radar guidance so the placement could be as close to the target as possible. Both aircraft break off the bombing run and try again, but Kermit again can’t find the aim point. Smoke from an American firebombing attack on the nearby city of Yata is obscuring the target and the Japanese industrial factories in the area producing thick black smoke. the commander of the US Air Force’s 21st bomber command, Major General Curtis Lame has escalated the firebombing campaign of Japanese cities following the attack on Hiroshima. Although the new strategic bombing campaign is intended to budge the enemy into surrendering, it is now working against this mission. By the third bombing run, box car is running out of fuel after spending 45 minutes above and enemy fighters have been detected on radar. The third bombing run also fails and Captain Sweeney has a decision to make. If he continues to wait for conditions to improve over Kakura, he rises a run in with Japanese interceptors, he could cancel the mission and make an emergency landing in Okinawa with Fatman still aboard, or he could continue to the secondary target of Nagasaki, which is 95 mi away. At 11:32 a.m., Sweeney decides to make for Nagasaki along with the great Artis. The city of Kokura has been spared from destruction, thanks in part to the delay over Yakushima Island, spawning the Japanese expression, Gakura luck, to describe the lucky avoidance of great misfortune. Now, the city of Nagasaki is in danger. The city of Nagasaki is one of the most important industrial centers in the Japanese Empire. Two Mitsubishi factories operate within the city’s limits, including the Mitsubishi torpedo plant, which mass-produces the infamous Longance Torpedo. Additionally, the city of 286,000 people is home to a major port area with shipyards vital to the Japanese war effort. It takes just 34 minutes for the Superfortress to arrive at Nagasaki, but Major Sweeney is disappointed to see that weather conditions have deteriorated here as well. After deliberating with the crew for 2 minutes, Sweeney decides to take one more pass over the target. If the bombader can’t find the target, the bombing will be aborted. At 11:58 a.m., Boxcar begins his final bombing run. At this precise moment, the Japanese Imperial Supreme War Council is meeting in Tokyo to discuss a conditional surrender to the Allies. The cloud cover is still too thick over Nagasaki, forcing Captain Kermit to navigate using radar. He scans the city through the bomb site before spotting a small break in the clouds 2 mi north of the ideal aim point. Knowing it’s now or never, Kermit calls out, “Bombs away!” before immediately correcting himself, “bomb away.” Fat Man falls free and Box Car along with the great artist flee from the target. To understand how Fat Man works, we first need to understand the parts of the nuclear weapon. Starting from the back, we have the California parachute tail, which is meant to stabilize the weapon when dropped from an altitude of 9,000 m. Next, we have the bar tube collector, which helps measure the altitude of the bomb. This section contains the bar tube switches, radar, and timers. Moving further ahead are the 32 detonator wires connected to the firing set, also known as the X unit, placed near the charge. On the opposite end of the weapon are 24volt batteries required to detonate the weapon. Moving to the exterior are three arming plugs that are removed before the bomb is dropped. These are the four Archie radar antenna that activate where the bomb reaches its detonation altitude. Finally, at the front of the bomb, we have four A self-destruct fuses. These devices were made to self-destruct the weapon if the bomb failed to detonate after being dropped, ensuring that the weapon wouldn’t fall into the hands of the enemy. [Music] [Applause] Located at the heart of the weapon is the internal neutron generator. This component is responsible for emitting neutrons essential for the nuclear chain reaction. Inside is a burillium pallet and a burillium shell with inward pointing spikes encased in pelonium, a radioactive substance that emits alpha particles. The entire neutron generator assembly is 2 cm in diameter. Surrounding the neutron generator is the main fision material, a highly radioactive 6 kg plutonium sphere measuring around 9 cm in diameter encased within another concentric sphere of highly radioactive uranium 238. This deadly combination acts as a neutron reflector increasing fision efficiency required for detonation. Surrounding the uranium sphere lies a thin layer plastic shell made of acrylic thermoplastic enriched with boron. This component absorbs slowmoving neutrons preventing predetonation. The critical components for the fizzen reaction are encased in a thick layer of aluminum known as the aluminum pusher which uniformly transfers shock waves from the explosives to the uranium core. The aluminum sphere are surrounded by 32 blocks of faster explosives consisting of 61% RDX and 39% TNT. An additional layer of 32 explosive blocks comprised of 70% bomb nitrate and 30% of TNT lies outside forming an explosive lens to shape the detonation wave. Each explosive block contains a detonator for initiation. This assembly is referred to as the physics package which is encased in a fixed steel case to contain the explosion of fast and slow explosives. Precise and simultaneous detonation of all explosive blocks is critical for a symmetric detonation, ensuring a nuclear chain reaction. Lastly, the X unit, an electric component with capacitors, produces electric current, distributing it simultaneously to all 32 detonators. [Music] [Music] Now, let’s take a look at how this nuclear bomb works in basic step-by-step format. Step number one, before the bomb is dropped, all three arming plugs are pulled one after another. Step number two, the Bombay doors open and the bomb falls due to gravity. When released, its internal 24volt battery starts a timer. After 15 seconds, the barometer senses the desired height, activating multiple radar altimeters located at the front of the bomb. The barometric stage was added because of a worry that external radar signals might detonate the weapon too early. Step number three, to ensure accurate detection of the bomb’s final altitude, multiple radar altimeters were utilized. This process involves measuring the altitude above the ground and beneath the bomb through the timing of radio wave travel and reflection. Step number four, once the correct height was sensed, the X firing switch activates, sending signals through the 32 wires to the explosive detonators. Step number five, the outer faster charge explodes inward, followed by the inner ring of explosives, creating a concave shock wave. Step number six, the explosion travels to the aluminum pusher, breaking the buron plastic sphere. Step number seven, the shock waves travel towards the uranium 238 sphere. This makes the plutonium sphere denser, compressing it further. In the process, the extreme forces crush the burillium shell and the palonium, releasing neutrons required for efficient reaction. An airburst detonation delivered from a single fat man atomic warhead with a yield of 21 kotons over the city of Nagasaki had catastrophic consequences. [Music] Upon detonation, an immensely hot and luminous fireball was formed, expanding to a radius of 222 m, vaporizing everything in its path. Those near the blast were evaporated and within a 760 meter radius, all buildings were destroyed, killing 16,000 Japanese civilians in a matter of seconds. Very soon after detonation, multiple destructive blast waves developed, moving rapidly away from the fireball. The extreme radiation zone had a radius of 1.31 km. Here, Japanese civilians received a 500 rim ionizing radiation dose, which was likely fatal in around 1 month’s time. 15% of survivors would eventually die of cancer due to radiation exposure. Within a 1.72 km radius, the shock wave emitted was measured at 5 psi, also known as a moderate damage blast zone. Here, most residential buildings collapsed. Injuries are universal, and fatalities are widespread. Most commercial and residential fires started within this area with damaged buildings spreading fire throughout the city within a 2.21 km radius. Due to the bomb’s extremely high temperature, the shock wave emitted contained high levels of thermal radiation causing thirdderee burns and clothing to instantly ignite into flames. Thirdderee burns extended throughout the layers of skin and were often painless due to destruction of pain nerves. This left many with severe scarring or disablement and in severe cases often required amputation of burnt limbs. As a result, around half the people between 760 m and 2.21 km from the blast were killed from burns, debris, smoke, collapsed buildings and radiation sickness, which translated roughly to an additional 69,000 Japanese fatalities over a period of 60 seconds. Within a 4.59 km radius, was a light blast damage zone. Here damage was caused by shocks similar to those produced by thunderclap or a sonic boom, but with much more force. Although some windows were broken over 10 miles away, the injury associated with flying glass generally occurred at over pressures of around 1 PSI. This damage corresponded to a distance of around 3 mi or 4.8 km from ground zero from a 21 kiloton nuclear explosion. The damage in this area of Nagasaki varied widely as shock waves were beded multiple times off buildings, terrain, and even the atmosphere. As first responders moved inward, windows and doors were blown in, and gutters, window shutters, roofs, and lightly constructed buildings had increasing damage. litter and rubble increased moving towards ground zero and there was increasing numbers of stalled and crashed automobiles that made emergency vehicle passage difficult in all around 15,000 civilians were killed in the light blast damage zone raising the total death tally to around 100,000 over a period of 60 seconds with an additional 86,000 injured as Oh, [Music] [Music] [Music] heat Heat. [Music] Heat.

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With the defeat Germany on May 8th 1945, the United States was an in a precarious situation. Even with the steady destruction of its empire, Japan simply wouldn’t surrender. The United States had two options: mobilize over 2 million men and invade the Japanese home islands incurring nearly 1 million causalities and adding two years to the war
or use one of the most destructive technologically sophisticated weapons known to man.

America choose the latter; on August 6th 1945, the Enola Gay left the Northern Mariana Islands. Inside was a 15 kiloton, gun-type fission weapon loaded with over 145 pounds of highly radioactive uranium, its name was Little Boy. Six hours later, at the height of 31,000 ft, the first atomic bomb was dropped over the city of Hiroshima, with catastrophic consequences.

But how exactly did the Little Boy Atomic Bomb work?
What were the parts and mechanisms of the first nuclear bomb?
What processes did it undergo during its detonation?
Why was Hiroshima targeted?
How big was the blast zone?
How much of the city was destroyed and most importantly how many Japanese casualties were incurred when the first American atomic bomb reached its destination?

Sources:

Little Boy Bomb: https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196219/little-boy-atomic-bomb/

US Firebombing Campaign: https://www.britannica.com/event/strategic-bombing-during-World-War-II

Little Boy Blast Zones: https://www.nps.gov/articles/000/the-atomic-bombings-of-hiroshima-and-nagasaki.htm

Fatman Bomb: https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196220/fat-man-atomic-bomb/

Fatman Blast Zones: https://www.osti.gov/opennet/manhattan-project-history/Events/1945/nagasaki.htm

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