Awesome! I've read Rhodes' "The Making of the Atomic Bomb" (1986). I think it was Oppenheimer and a few of his students that figured out that the "gun type" bomb would have worked even before they got to Los Alamos.
Was there any provision to vent the compressed air in the gun tube that might have retarded the acceleration of the uranium projectile after the cordite charge detonated? ? Or was the cordite charge so powerful that this effect was not an issue?
No venting that I'm aware of. I would highly doubt there was. The cordite charge was indeed very powerful for maximum velocity. It was all over in milliseconds, so no need to ease the strain on the gun barrel.
The time for which the reaction proceeded in the little boy weapon was around 1.85 microseconds. The efficiency was between 1.14 & 1.58%. A few other minor issues not worth raising. Good vid.
What does critical mass mean? It was a nice video but, it didn't explain the core mechanism that I wanted to know: why do you need to shoot the 2 sets of rings to start the explosion. I used to think that you smash the two blobs together, but in this explanation it seems that instead you just line up the two blobs to make a bigger blob. How does that start the explosion?
Critical mass is the critical minimum amount of fuel required for a self sustaining reaction. When a nucleus fission, it releases neutrons. The chance of these neutrons interacting with another uranium nucleus is quite small, it can pass right though. If you have a larger block of material, there are more nuclei between where the neutron originated and the air (or whatever other material) outside the fuel. If you're in a room, and you close your eyes and throw a ball in a random direction, the bigger that room, with more people in it, the higher the chances of you hitting someone compared to hitting the wall. If we suppose the room needs to be 10,000 square feet and contain 3000 people (made up numbers) for you to have a 50% chance of hitting a person and 50% chance of hitting the wall, you could say that size and number of people is the critical size for you to be equally likely to hit and miss. Now if the rules are that anyone who is hit with the ball has to throw their own ball in a random direction, then if your number of people is the critical number, this chain reaction of people throwing balls at each other will be self sustaining. Obviously an inaccurate analogy, but it gets the point across. As for why the two rings were separated initially (to prevent any chain reaction) imagine you divide this critical number of people into two rooms, a mile apart. If you throw your ball, the chances of hitting people a mile away are low, and there aren't enough people close to you for you to have a 50% chance of hitting someone. So chances are your ball will hit the wall, and the game ends. Bring the people in the other room closer, and the odds begin to shift on your favour.
They didn't perform a test detonation of the fuel used in little boy. They tested exploded a plutonium bomb. They also performed tests on the fuel to be used in little boy, but with experiments that didn't destroy it.
I only have one question about this bomb after watching this excellent series. Why does bringing the two masses of Uranium 235 together rapidly cause the reaction? You explained how the reactions happen nicely, but I am a bit confused about how the supercriticality happens when it is just bringing together atoms which are existing alongside each other in the rings already. Yes, I can go research it and I will, but it would have been nice to include the mechanism's reaction dynamics here. Thanks for the great video regardless of my critique. I just hope it helps your channel a bit.
The chain reaction happens whether the pieces are brought together quickly or slowly. The need for speed is to maximize the explosive yield of the chain reaction, which happens so fast, in just millionths of a second. If the uranium projectile is not moving fast enough, the bomb will blow itself apart (and scatter the uranium) before the two pieces have fully come together, hence the explosion will be a “fizzle.”
@@realsamuelhawley Thanks for the reply. That clears up part of it, and I did look into it a bit as well. So, the gun is for building the supercritical block quickly for maximum neutron carnage before lesser reactions can "jump the gun"(pun intended). It seems that slowly putting them together would be like throwing a firecracker into a small pile of firecrackers. There may be some ignited after the first blast, but mostly they'll be unlit and blown away from the source of ignition. Do I understand correctly that the two pieces (when apart) aren't enough mass individually to trigger a reaction, but the quick combination of them in a tight space is the tipping point to optimal supercriticality?
If the Japanese used a stripped-down version of the bomb, as you suggest, then any suicide mission could’ve used a fighter aircraft, rather than a heavy bombers, Thereby increasing the chances of making it to the target.
Well after so many years 1988 to know i have understanding of the bomb, the internet was not around back then so public libraries and pure speculation was all that was available, the explanation conformes to the outside dimensions so i believe it.
The Hiroshima bomb must be the most inefficient A bomb ever built, when you consider the fact that if of a propper geometrical form it only requires about 26 lbs 95% pure U235 to produce the same effect. And a beryllium reflector can reduce that even more. Talk about crude
The Mk-I was not the most inefficient A bomb ever produced. I can think of at least one example with a lower efficiency: The W-54 mod 2, with an efficiency as low as 0.015%, compared to at least 1.14% for the Mk-I. That at least 76 times less efficient.
Awesome Videos! Would be interesting to know how they figured out it was barely 1%? ( th-cam.com/video/3iTr2W9p8TI/w-d-xo.html ) And since it was 1%, would it have been possible that the first 2 plates fissioned and exploded before the rest of the uranium plates could? Making the subsequent plates unnecessary.
We know the average energy released per fission event. We know the mass of a single nucleus. We know how much energy was produced by the weapon (approximately). Based on estimates of the yield of the explosion, we can calculate that the efficiency was between 1.14 and 1.58%. The central region of the core would have fissioned more efficiently, as the neutron flux was highest there, however material fissioned in all the rings and all were necessary to produce the explosion.
Wait a sec, I didn't know he made a new series after the one about the Imjin War.
What a nice surprise, a welcome one!
Thanks for dropping by, GS!
Awesome! I've read Rhodes' "The Making of the Atomic Bomb" (1986). I think it was Oppenheimer and a few of his students that figured out that the "gun type" bomb would have worked even before they got to Los Alamos.
Another amazing episode. Getting better and better! Keep it up =)
Was there any provision to vent the compressed air in the gun tube that might have retarded the acceleration of the uranium projectile after the cordite charge detonated? ? Or was the cordite charge so powerful that this effect was not an issue?
No venting that I'm aware of. I would highly doubt there was. The cordite charge was indeed very powerful for maximum velocity. It was all over in milliseconds, so no need to ease the strain on the gun barrel.
The time for which the reaction proceeded in the little boy weapon was around 1.85 microseconds.
The efficiency was between 1.14 & 1.58%.
A few other minor issues not worth raising.
Good vid.
What does critical mass mean? It was a nice video but, it didn't explain the core mechanism that I wanted to know: why do you need to shoot the 2 sets of rings to start the explosion. I used to think that you smash the two blobs together, but in this explanation it seems that instead you just line up the two blobs to make a bigger blob. How does that start the explosion?
Critical mass is the critical minimum amount of fuel required for a self sustaining reaction. When a nucleus fission, it releases neutrons. The chance of these neutrons interacting with another uranium nucleus is quite small, it can pass right though. If you have a larger block of material, there are more nuclei between where the neutron originated and the air (or whatever other material) outside the fuel.
If you're in a room, and you close your eyes and throw a ball in a random direction, the bigger that room, with more people in it, the higher the chances of you hitting someone compared to hitting the wall.
If we suppose the room needs to be 10,000 square feet and contain 3000 people (made up numbers) for you to have a 50% chance of hitting a person and 50% chance of hitting the wall, you could say that size and number of people is the critical size for you to be equally likely to hit and miss. Now if the rules are that anyone who is hit with the ball has to throw their own ball in a random direction, then if your number of people is the critical number, this chain reaction of people throwing balls at each other will be self sustaining. Obviously an inaccurate analogy, but it gets the point across.
As for why the two rings were separated initially (to prevent any chain reaction) imagine you divide this critical number of people into two rooms, a mile apart. If you throw your ball, the chances of hitting people a mile away are low, and there aren't enough people close to you for you to have a 50% chance of hitting someone. So chances are your ball will hit the wall, and the game ends. Bring the people in the other room closer, and the odds begin to shift on your favour.
how was they able to do a test run if all the uranium was used in little boy?
They didn't perform a test detonation of the fuel used in little boy. They tested exploded a plutonium bomb.
They also performed tests on the fuel to be used in little boy, but with experiments that didn't destroy it.
I only have one question about this bomb after watching this excellent series. Why does bringing the two masses of Uranium 235 together rapidly cause the reaction? You explained how the reactions happen nicely, but I am a bit confused about how the supercriticality happens when it is just bringing together atoms which are existing alongside each other in the rings already. Yes, I can go research it and I will, but it would have been nice to include the mechanism's reaction dynamics here. Thanks for the great video regardless of my critique. I just hope it helps your channel a bit.
The chain reaction happens whether the pieces are brought together quickly or slowly. The need for speed is to maximize the explosive yield of the chain reaction, which happens so fast, in just millionths of a second. If the uranium projectile is not moving fast enough, the bomb will blow itself apart (and scatter the uranium) before the two pieces have fully come together, hence the explosion will be a “fizzle.”
@@realsamuelhawley Thanks for the reply. That clears up part of it, and I did look into it a bit as well. So, the gun is for building the supercritical block quickly for maximum neutron carnage before lesser reactions can "jump the gun"(pun intended). It seems that slowly putting them together would be like throwing a firecracker into a small pile of firecrackers. There may be some ignited after the first blast, but mostly they'll be unlit and blown away from the source of ignition. Do I understand correctly that the two pieces (when apart) aren't enough mass individually to trigger a reaction, but the quick combination of them in a tight space is the tipping point to optimal supercriticality?
@@troys9222 Yes, that seems to be about right.
If the Japanese used a stripped-down version of the bomb, as you suggest, then any suicide mission could’ve used a fighter aircraft, rather than a heavy bombers, Thereby increasing the chances of making it to the target.
I have that can in my fridge. But as we saw in Indian Jones 4 I should be safe
Well after so many years 1988 to know i have understanding of the bomb, the internet was not around back then so public libraries and pure speculation was all that was available, the explanation conformes to the outside dimensions so i believe it.
Welcome to the FBI watch list.
Imagine if the scientists in North Korea were watching this. It would be the funniest thing in the world.
North Korea doesnt have the raw materials to build nukes.
They already know all of this and much more.
@@bruceli9094 Weird how they've somehow managed to detonate 6 of them in the last couple of decades then..
The Hiroshima bomb must be the most inefficient A bomb ever built, when you consider the fact that if of a propper geometrical form it only requires about 26 lbs 95% pure U235 to produce the same effect. And a beryllium reflector can reduce that even more. Talk about crude
The Mk-I was not the most inefficient A bomb ever produced. I can think of at least one example with a lower efficiency: The W-54 mod 2, with an efficiency as low as 0.015%, compared to at least 1.14% for the Mk-I. That at least 76 times less efficient.
Awesome Videos! Would be interesting to know how they figured out it was barely 1%? ( th-cam.com/video/3iTr2W9p8TI/w-d-xo.html ) And since it was 1%, would it have been possible that the first 2 plates fissioned and exploded before the rest of the uranium plates could? Making the subsequent plates unnecessary.
No. Then there wouldn’t of been enough material to form a critical mass.
@@wadeshort3 thanks for replying... Great work on the imjin series Btw! Amazing story telling and very engaging.
We know the average energy released per fission event. We know the mass of a single nucleus. We know how much energy was produced by the weapon (approximately).
Based on estimates of the yield of the explosion, we can calculate that the efficiency was between 1.14 and 1.58%.
The central region of the core would have fissioned more efficiently, as the neutron flux was highest there, however material fissioned in all the rings and all were necessary to produce the explosion.