Absolutely wild and related story from The Making of the Atomic Bomb by Richard Rhodes. As of a week before Trinity, there were not enough quality lens castings on hand to make a complete charge. Oppenheimer also insisted on firing a “copy” of the gadget before Trinity to test the high-explosive design at full scale without the Plutonium. Each unit required ninety-six blocks of explosive. A PhD physical chemist on the Manhattan project (George Kistiakowsky) recalled his solution: “In some desperation, I got hold of a dental drill and, not wishing to ask others to do an untried job, spent most of one night, the week before the Trinity test, drilling holes in some faulty castings so as to reach the air cavities. indicated on our x-ray inspection films. That done, I filled the cavities by pouring molten explosive slurry into them, and thus made the castings acceptable. Overnight, enough castings were added to our stores by my labors to make more than two spheres.” “You don't worry about it," he added, "I mean, if fifty pounds of explosives goes in your lap, you won't know it."
That's one of my favorite non-fiction books. He really describes how the run up to fission came about, and how Oppenheimer, Kistiakowsky, Teller, Bethe came up with the design. How Seaborg synthesized/created/bombarded U238 to make Plutonium. How Fermi's "Pile" went critical. How Groves built cities of factories. But also how the physics of the early 20th century involved the Cavendish with Rutherford. Chadwich and the neutron. It's a fantastic read, and really describes how the 20th century came to be, as well as America's hegemony. He won the Pulitzer for it.
As a modern age scientist with all computer power on his side I cannot say how I admire these scientist to get it done by their own brains and hands and based on the minimal amount of empirical data available.
von Neumann was literally coming up with the von Neumann architecture and pioneering the modern computer at this time. I’ve read that nukes and computers basically arrived as technologies at around the same time, as early computers were needed to solve all the mathematical and numerical problems on the Manhattan Project. (Edit) Correction, not on the Manhattan Project, but after for making all the other nukes that were made after the war.
@@topdog5252 The ENIAC, von Neumann's first general-purpose computer, went operational in December 1945. It was originally designed to calculate ballistic trajectories of artillery. It was used for the nuclear program after the war, as there was no need to calculate ballistic trajectories in December 1945. The Manhattan Project relied on IBM punch card systems that were originally designed for business purposes. After the war, the US nuclear program and the development of more and more powerful computers was highly interlinked. Even to this day! Guess who has the largest supercomputers in the world: The US Department of Energy.
And with a timeline that would cause me to go bald within months. Urgency seems to be a paradoxical source of success for the government, as seen during the Apollo program as well. Give them an open ended goal, and they’ll take their sweet time.
I've never seen a youtuber end a video like that. Thanks. No shameless plugging. No feeling the need to rehash what we just saw. Just a few seconds of a blank screen to give the viewer a brief uninterrupted moment to let the point sink in.
I worked on Cuba District Wildland Fire and talked to some folks who worked containing the Los Alamos Fire and they said that many places were still closed off and they saw some very strange colored flames from. The ground fires.
Yes indeed, especially when it was human “computer” power too! Humans and slide-rules and adding machines. That’s how iterative simulation processes were often done well into the 1950s. And apparently some early models of IBM mechanical computers and card punch and sorting machine. The US was desperate to get this weapon first, so any amount of effort was deemed appropriate. The US was rightly scared sh**less. Because even if such a weapon was never directly deployed against the US, if Nazi Germany developed it first and simply held it as a threat, America also feared a total loss of Europe as a trading partner to a new fully “autarkic” Nazi-German ruled Europe which would have been disastrous for the future of the US. It should be noted too that the Nazis ALSO had full access to proprietary (often custome designed) IBM computers and card punch and card sorting technology … and even clandestine technical support for this equipment throughout the war from IBM employees itself. This should have been a scandal, and still to this day few people know much about it. I’m unaware if, or how much Germany and the Nazi scientists chose to use their proprietary IBM equipment in this way, to aid in physics, or bomb or rocket or aircraft design. The Nazis have been documented to have used their IBM equipment to aid in their efforts to keep track of and to purge “undesirable” people of all kinds in the German state, and to organize the surveillance, detention, and shipment of these unfortunate people in a highly efficient manner to the “appropriate” work or death camp. Terrible. Scandalous. To my knowledge IBM still hasn’t made a full accounting of this German activity themselves during WWII and has left it to independent historians and journalists to reveal how the company aided the Nazis and even took great pains to circumvent the slow-to-come US government regulatory efforts to stop their support of or doing business with an enemy combatant state that IBM executives were aware were using their equipment to design and enforce social policies that what would eventually come to be called genocidal. I’ve not encountered any historian’s work on the amount of computing power supplied to Los Alamos and the Manhattan Project by IBM; it would no doubt have been quite helpful and much faster to run complex mathematical simulations of implosion on their proprietary equipment!
People seem to forget that machines replace simple tedious tasks, think of a bottle opener, could you imagine a factory opening and closing a million bottles in the 1800? I can, just take 100 people in a factory line doing 10.000 tasks a month, 333 a day, 26.smt a hour, for 12 hours everyday
My neighbor was an EE who worked at Oak Ridge. He could only tell me a little of the work he did, but he got a secret $1 award for detecting pipe weld issues (and photo with a general). Lol. After he passed, he left his utility room open outside where he stored tools and old books. I went in to find a rasp tool he had and saw a book called Nuclear Reactor Design. I’m a pretty decent scientist, but I was lost after page 4. So complex and I admire the folks who developed those technologies.
I was a Naval Nuke. The heat transfer problems are intense. The cladding problems are intense. The radiation problems are intense. And I barely got a taste of that (enough to be an operator).
Even the teaching of the theory necessary to learn the methods needed to discover the means to success is still classified. Their path to success, to this day, is only guessed at.
@@canberradogfarts After a few beers, he told me a little more about strange lights in the sky and some other oddities. He would always stop himself and say “that’s all I can say about that “. I didn’t press him, he was so sweet.
He was a good mathematician, for sure. Not sure about his intuition as a physicist. Maybe he was misunderstood at the time, but the way we teach QM today (poorly) might have something to do with von Neumann's own misunderstanding of the physics behind the theory.
As a nuclear specimen collector and history enthusiasts.....and someone who works in photonics, I've always been stunned at the optical lens principles utilized in the explosive lense tech. Super cool shit
That's far out that matter and light both can use similar lens logic. Makes you wonder if that is a coincidence or if it tells us matter is maybe not so different than light after all.
@@brokentombot I don't think it points to a relation between matter and light. We see this type of thing all over the place when we are dealing with what I believe are typically called emergent behaviors/properties, when complex small scale interactions give rise to more generalized large scale phenomena. I think it points more to the incredible power of mathematics (specifically calculus) and our ability to build models from approximations. For example the equations that are used to model viscous fluid flow can also be used to model the movement of large crowds or traffic through highway systems. This doesn't mean that humans and cars are related to fluids in some way. The small scale interactions that are occurring between the molecules in a fluid, the people in a crowd or the cars on a highway are all obviously very different. To get the most accurate prediction of a fluid or crowds behavior we would need to be able to simulate each interaction between every particle/person, which would be incredibly complicated and is impossible for systems with a large number of particles. However we can make abstractions that can be used to approximate the large scale behavior such as how rapidly a disturbance (like someone getting shoved) will pass from person to person through a crowd, or how easy/difficult it is for people or cars to move past each other. These would be equivalent to the speed of sound in a fluid and the fluids viscosity respectively. By observing crowd behavior and traffic data we can make these abstractions and apply the same types of equations we use to model fluid and get very good approximations of a crowds behavior or traffic flow. So it's not that light and matter are in some way similar to each other, rather the emergent behavior of light wave propagation through different mediums and the emergent behavior of sound wave propagation through different materials both fall under the same problem type and can be modeled with the same category of equations. What causes these behaviors though is vastly different. Sorry for the obnoxiously long reply, numerical methods (computational modeling, or just using math to simulate complex system behavior) is a passion of mine, it was hands down my favorite subject when getting my engineering degree.
The irony is that newer ones use a small q-switched neodymium yag laser to trigger the implosion. The laser is made by Kigre corporation and is the same one used in eye surgery lasers for treatment of glaucoma. The laser pulse is delivered to the explosive directly that detonates as an acoustic wave shaper converts it into a structured force pattern, as you said is very similar to optics. The beam is split to 3 beams. 2 hit the implosion mechanism while the third one hits the explosive on the back of the neutron generation module. The design is 💯 percent fail safe, no risk of mistake. Security on the other hand. I truly hope they do not lose one of them. In theory it could be hot wired using the guts from a cheap camera flash unit.
@@WelchLabsVideoDo any of you productive people ever have to struggle to develop any memorizing methods (like zettelkasten or some other fancy note-taking system) or is accurate memory as natural as breathing to you? Furthermore, do you ever struggle to understand something for a longer time or is clarity and sharpness of thought also natural and effortless?
Correction for 4:51 In the second equation, b + r should equal √ (x²+(r+y-h)²) instead of √ (x²+(y-h)²) The fourth equation would also need correcting to: √(h²+x²)/v_f + (√(x²+(y-h)²)-r)/v_s
That is the best explanation of the Pu implosion problem I have ever seen -- the visual elements you used to explain the problem and it's eventual resolution made it clear and easy to understand.
The detonators had to go off within about a microsecond of each other. That explains all the coax swarming around Fatman. Very impressive for 1945 tube technology.
Yeah, that feels like a trivial problem to me ... until, ... wait, what do you mean I can't use a transistor? Those aren't invented yet? So what the hell do we switch with? Glass tubes? Uhhh.
Yup they were fired by 4uF 5.2kV capacitors each piped into that coax by a KN-6 switching tube that was originally designed to be used in a strobe lamp. Now they have them with two laser pulses triggering a couple very well made shaped charges that compress a double paraboloid core into a sphere. Let us pray control over one is never lost. 🙏
Today, about 8 hours ago, I saw the film "Oppenheimer" in IMAX 70mm. There's a lot to say about the movie, but this post is about the video above, "Oppenheimer's Gamble - The Plutonium Crisis". I can't thank you enough, Welch Labs, for adding so significantly to my understanding of what the Los Alamos team was doing. Well done!
The X-ray pics are new to me. I've never seen them in all the documentaries on the building of the plutonium bomb that I have watched and rewatched. Thanks for including them.
Actually, when the calculations became too complicated for von Neumann, he called in Stan Ulam. At that time Feynmann was a prodigy but not anywhere near the level of either von Neumann or Ulam. Ulam invented the Monte Carlo method of analysis. He was also the person that found the flaw in Edward Teller's design of the hydrogen bomb which is why it became the Teller - Ulam design.
Amazing video. Your channel is quickly becoming one of my favorites. As an engineer this is exactly what I had been looking for. Absolutely loved that you didn't shy away from math. People don't realise that engineering problems are actually just applied math problems. Wish they had done this in the movie, too.
I'm not STEM oriented at all, but was able to get the gist here, and found it way more interesting that the middle :45 of Oppenheimer. Not sure why Nolan opted to brush over so many of the tech obstacles the team faced. The film made it seem like it was mostly politics. Thanks for sharing. And for torching a nice piece of wood.
I think it was because he wanted to make it about Oppenheimer and his internal struggles mentally instead of the technical marvel he created, and probably for the better because it is some pretty advanced stuff even today.
Klaus Fuchs , who was passing on information as a Soviet spy was also an important contributor to solving this problem. He published still classified papers on the theory of jets and explosive waves. He also held patents with Von Neumann, Teller and others.
What a wonderful explanation. Many thanks. I remember working with engineers at Los Alamos back in the early 90s. They explained that they needed to CNC machine pieces to a tight tolerance and to a specific spline geometry. Now I have a much better understanding of why they needed this.
This is easily one of the most phenomenal RUclips videos I've ever watched! Excellent writing & clear narration explained complex ideas extremely well. This video gives even more perspective into the astonishing brilliance of the minds behind the Manhattan Project. Thank you for this clip!
Nice video! However, I would push back on your claim at @1:20 that once you reach critical mass "it is basically impossible to keep it from exploding." This isn't true. If it were that easy, there would have been no need for the massive amount of scientists, money, and time for the MP to produce a bomb. A supercritical piece of fissile material itself will almost certainly fizzle out before exploding, releasing a massive amount of ionizing radiation and heat but not exploding. Once a lump of fissile material goes supercritical, the temperature of the fuel increases drastically, which actually buffers the reaction before it can explode. Almost always, the nuclear reactivity of a fuel will be inversely proportional to the temperature. The reason is two-fold: 1) faster moving neutrons associated with increased temperature are less likely to initiate fission before it exits the material altogether, and 2) thermal expansion of the hot fuel will reduce the density of the material and thus the reactivity. This will usually cause the fission events to slow to an equilibrium in a critical state or to go subcritical altogether. To get an explosion from a supercritical piece of fissile material, you have to ensure that many generations of fissile events are able to occur very quickly before these natural buffering factors cause it to fizzle. This is where things like implosion hydrodynamics, neutron initiators, and tampers had to be leveraged to actually cause an explosion. All that to say, it's actually quite difficult for a supercritical material to explode.
You seem to be educated on the topic. Is what you describe the reason why nuclear reactors improbable to explode and the worst case scenario is a meltdown instead of explosion? I believe this has something to do with the isotopes as well. If so can you elaborate what actually makes certain isotopes favorable to explosion/meltdown (bomb/not bomb). For example certain isotopes are best for bombs and certain are for nuclear reactions
@@rinkashikachi Yes, nuclear reactors are susceptible to meltdowns, which may lead to other types of explosions, such as the steam explosion at Chernobyl. However, they are not going to explode like a nuclear weapon because of some of those reasons I mentioned. That does not mean that there won't be any explosions from a reactor or that a massive amount of radiation won't be released in the event of a meltdown. I only mean that true nuclear explosions do not happen unless the supercritical mass is weaponized. A lot has to go right for a true nuclear explosion to happen, which is not really possible in the configuration of a reactor. There just isn't enough time before the core comes apart for enough fission generations to proceed in order for all that energy to be released as an explosion. Your question about isotopes is a pretty complex question. I probably have an above average knowledge of nuclear physics than the general public(I have a PhD in a somewhat related field), but I am by no means an expert, so take this with a grain salt. Generally, both fission reactors and weapons still use the same isotopes (U-235 or Pu-239) for their fissile fuel. However, weapons grade U-235 is highly enriched, meaning there are very few of any other isotopes present in the material. On the other hand, reactors use the same U-235 isotopes but the fuel is not enriched to nearly the same degree. Since there are other isotopes still present in reactor fuel (primarily U-238), these will absorb neutrons without fissioning and thus slow the overall reaction. Generally, I believe they want the core of a reactor to be oscillating back and forth between criticality. Whereas for a weapon, you have to have the reaction go as quickly as possible. Even with highly enriched U-235, this most certainly won't happen on its own. That is why the MP had to use things like tamper, which kept the core together for a split second longer using its own inertia before the reaction blew it apart (it also reflected neutrons that would otherwise be ejected from the core). Using Pu-239 is more complicated since it does not exist in nature, and is either synthesized from Uranium beforehand or in real time within a reactor. Finally, I should mention that fusion reactors are sort of the desired future technology, as they do not release fission products and can produce a lot more energy efficiently. These will use different fuels altogether, usually light isotopes like those of hydrogen. To my knowledge, these are still a long way off. Again, I am no expert. I am happy for anyone to correct any error I may have made.
The sentence you quote is taken out of context and is also badly worded in the first place The issue was the Plutonium-240 impurity in Plutonium-239. The supercritical configuration needs to be assembled extremely fast to prevent a pre-detonation caused by the Plutonium-240 impurity before the assembly is finished. This made the gun-type design infeasible.
I was born in Los Alamos in May 1944, where my parents were both employed on the Manhattan Project. I have read and studied extensively what happened there; while I understood the theoretical problem inherent in plutonium and how they solved it, I never understood how technically they got from the theory to the engineered solution. This is easily the best video I have seen on this subject. Great job!😂
@@personanongrata987 No. My birth certificate lists as my place of birth as 1Sandoval County Rural.” I think I may have been born too early for the famous 1663 designation. There are a couple of birth certificates in the small Fuller Lodge museum at Los Alamos, and both have birthdates after mine. Several years ago I had to obtain a birth certificate from the State of New Mexico for f a claim my brother, sister and I filed against the federal government for our mothers death from radiation exposure. That certificate simply states my place of birth as Los Alamos.
Wow! Your lecture made my brain glaze over. My knowledge of nuclear physics would barely gotten me a passing grade in a 2nd year of college. But you made it very understandable. This was a well-made explanation and educational to the learned and the layman.
I believe the electric device developed is called an SCR. Simular to a transistor and kinda like a switch. Very heavy duty and durable as well as Ultra reliable. The SCR currently is the heart of modern high efficiency electric systems. Inverters are made using them. Just incredible that all this crap was done long hand.
I suspect the fast electric switching device was the thyratron / krytron. SCRs emerged in the late 1950s. I have a 1960 inverter which I believe uses SCRs. In the 1970s bipolar transistors took over, devices like the 2N3055 not being uncommon. Then FETs, and now IGBTs.
This is the clearest explanation I have seen of the Manhatten Project engineering, particularly the explosive lenses piece - and you have incidentally illustrated why the cost was so high. Very well done indeed. Many thanks.
@@mickeyhage Nope. He glossed over the technicalities and focused more on Oppenheimer himself. If you haven't seen it it's actually a rather good biography.
At least 5 or 6 other YT''ers did., even theGrahamNortonShow ..also an interesting long-form take from U_Minnesota ruclips.net/video/_TQJEMC6mkk/видео.html (thank me later). Too much of a coincidence for this to be unrelated to the movie-launch; but did the movie-studio ask these science-influencers to create the videos, or is it just the zeitgeist? We shall never know ;)
I don't know what was cooler - learning about the RaLa experiment setting the forest on fire (I didn't know that happened), the kitty in the background at 7:19, or the tiny fire extinguisher. Great video!
In his auto biography Feynman writes about being sent to oak ridge to inspect how the uranium was being stored, they kinda forgot about ataining a critical mass he speaks about how they narrowly escaped a disaster, the inspection was very timely the book is titled " surely your joking Mr. Feynman it's an easy read not at all dry fascinating the man was amazingly down to earth given his status.
Wasn't it that there were two vats of liquid uranium solution and people put them on their side of a wall, not realizing that neutrons can go through walls. I seem to remember something like that, perhaps from Rhodes' book.
Nice video! I have seen the "implosion" method being talked about in many video but never a detail description of what it is. I assumed it was just a big circular TNT wrap around a core. It turns out the method is way more complicated than expected.
When Manhattan project scientists started to work on the bomb, they also thought that it would be as easy as wrapping some explosives around a shell of nuclear material. The idea was to collapse a tube of plutonium into a ball and make it super-critical. All this stuff with compressing plutonium, explosive lenses etc took enormous effort to figure out -- it was not obvious at all even to a bunch of these best in the world scientists.
Check this one out, it's much better and quite a bit more historically correct (I'm a physics prof). I'm getting sick of everyone on youtube over-crediting Oppenheimer: ruclips.net/video/H1QuZ6nsC68/видео.html
@@cogoid yes, absolutely. People really underestimate how many scientists actually worked on Trinity, and the interesting thing is that so many people made necessary contributions to the function of the bomb.
Richard Feynman was a genius. He discovered the cause of the Challenger accident on live TV all while he was dying from cancer. He was also a great safe cracker and musical bongo player.
@@nobonespurs Factually, it was Donald J. Kutyna and Roger Boisjoly who steered Feynman towards the faulty clevis design. Sally Ride gave Feynman a peice of the O-Ring. He was the one who masterfully managed the ice water and C-Clamp demonstration so a non-technical person could understand what happened in the cold weather.
@@retiredbore378 Am I correct to say that a similar problem was found at Boeing after a couple of newer model planes crashed? Management and sales had promoted a product (to the delight of executives and shareholders) that engineers had serious doubts about. Serious enough that internal document trails revealed quite a dark streak of gallows humour concerning the safety of the aircraft, concerns that were shown to be well founded.
@@drn.o.thunderfinger9738 this is why engineers need to be in the C-suite of any company that makes a physical product. The more high risk the product is to human life if it fails, more engineers should sit on the boards.
I'd love to see a sequel about Ivy-Mike. There are so many documentaries and movies about the Manhattan project, and rightfully so. But, in the midst of the hype, people forget that bombs which are tens of thousands of times more powerful were developed in the 50's thanks to the similarly fervent engineering efforts to build a hydrogen bomb. And I'm curious what Oppenheimer thought about hydrogen bombs. Or that particular test.
Oppenheimer feared the creation of a US hydrogen bomb would encourage a more feverent and dangerous arms race. Despite initially supporting the development (or rather not being opposed) he thought about the trinity test and the subsequent deployment against Japan, and thought something like a bomb 1000x bigger than that would destroy the world
See, I went to Oppenheimer expecting more detailed information like this but it really came up short. I didn't realize it was based on a biography and as such was literally just about his life, warts and all, rather than the process by which the bomb was built and how a nuclear weapon operates.
Yes, I've watched several RUclips videos which have clearly explained stuff that the movie I watched on Monday, glossed over. And when they did explain in the movie, it was basic, GCE O-level physics I did 50 years ago. Thank you RUclipsrs for your videos
As I understand it, the explosive lens design was invented in the UK, where HM Government was expecting some quid Quo Pro, but did not get any. So the UK developed the Blue Danube free fall bomb to be carried by the RAF's V-Bomber force. There is a very interesting document that explains this:- "first-waltz_UK_A-bomb project" which can be found with google. I am not sure if the original idea came from James Leslie Tuck OBE, (9 January 1910 - 15 December 1980) but I am pretty sure the explosive lens was a UK thing. The wartime UK A Bomb project research and the code 'Tube Alloys Ltd' and had succeeded in solving a lot of the theoretical work by 1943. Watch:- Equinox. A Very British Bomb
James Tuck was a British physicist assigned to the Manhattan Project at Los Alamos. Tuck knew von Neumann was working on shaped charges for the implosion design, and is the person that suggested the explosive lens design to von Neumann.
@@buckhorncortez The French went on to develop their own independent A-bomb program- but they didn't have anyone at Los Alamos, did they? (or any spies like the Russians to pilfer the data)- how did they do it?
The UK had a significant role in the shaped charges, explosive lenses, and micro switches to exactly time each detonator. It was recognised (lightly) in the 'Fat man and Little boy' (aka 'Shadow makers') 1989 film. My dad worked on the micro-switches, and like any good engineer, guessed what they must have been for from the specs. Thank you for this wonderful summary
They are tubes called krytrons and sprytrons. They can hold off a lot of voltage and can turn on very quickly. The krytrons are krypton and hydrogen filled devices that create an arc like a thyratron but quickly. The sprytrons are similar but have a vacuum inside. When fired a fine plasma is created from the two trigger electrode pins and it causes a vacuum arc inside. These are quicker than krytrons but are one shot devices.
@retiredbore378 sounds like EG&G part number KN-22. Krytron tube. Had a similar issue with them for a holographic laser service set. Was used to fire off the electro optic q switch module in it. Were irreplaceable for the application too. Two shots user determined of 4nS pulse duration by up to 1mS separation.
Many says he was the smartest man ever walked on this planet. When Nobel prize winner Jenő Wigner was asked how it felt to work with so many genius like Einstein, Heisenberg, Fermi, Bohr.. His reply was epic: I only knew one genius: Naumann
The high spontaneous fission rate resulted only from the Plutonium 240 contamination in the reactor bred samples, Pu-239 itself could work in a assembly type bomb.
What a superb ending to video , poignant music gradually fading in during the outro narration followed by a simple fade to black and 5 second reflective moment. Like.
As a retired commercial system software developer, John von Neumann authorship of the stored-program concept makes him my hero. Having a mathematics degree, I also respect that he, along with Osar Morgenstern, created a new branch in mathematics called game theory. So his contribution to the hydrodynamics of the implosion bomb is just another way in which the man changed the course of history, he dying 37-days after I was born.
The mathematician who invented the Monte Carlo method was Stan Ulam. Ulam was also the person von Neumann requested to be assigned to the Manhattan Project when the calculations became too difficult for von Neumann.
Excellent video that was super interesting and cool to watch! Im a 1st year applied physics major and the Manhattan Project is initially what fascinated me about the field! Thanks for uploading!
Man this was interesting. I knew about the implosion method and how difficult it is to implement, but I wasn't aware of details of design and measurements methods.
I'm with everything except the part about "you see that solid metal ball? It's made of some of the densest material known to man... And we're gonna squeeze it perfectly to a fraction of it's size"... The water in the hand thing was good but I think a little short ended - would have been useful to remind there that water is deemed incompressible... And something even *less* forgiving is in play. Obviously that shit works because that's the only thing that changes to set the damn thing off... And they definitely go off 🤣
7:00 How did they stored the captured data from the sensors to analyze the implosion coherency? This is a high speed signal, and puts instantaneous glitches on the Oscilloscope CRT. As far as I get it from the depiction from the video, they were using vacuum tube analog oscilloscopes. Thanks for the answers in advance...
Analog storage oscilloscopes are a thing. They use a special CRT that can first write a trace on the screen (one-shot), then refresh it with a low-power "flood gun". The display can't be maintained for very long, but long enough to get a photograph for later analysis. That said, I don't know whether they were available in the early 1940s, nor how they could have displayed traces from multiple sensors at the same time, so perhaps some other technology was used.
@@DonDueed Thanks for sharing your knowledge. It seems the devil hides in the details. What these scientists achieved in the 40's is remarkable....There are a lot of things to be learnt from them.
Phantastic. I saw Oppenheimer the movie and would rate it 1/10. Like it literally doesn't go any lower. The director is proud of 100% no CGI and used a chemical explosion and some overexposure to capture the moment of the bomb. I wonder what kind of people are content with this movie. I guess the kind that never watched youtube on that subject. Also highly recommend Veritasium and a bunch of others channels who showed various facets of the bomb.
I could never understand why it would be hard to design a bomb once you've made material that wants so badly to explode. Now I'm amazed they managed at all especially upon first dress rehearsal.
The problem is that the fissile material, whether uranium or plutonium, doesn't really want to explode. It wants to undergo fission reactions, but only so long as it remains a critical mass. The only way to get it to explode is to reach a supercritical state so that the number of fissions increase exponentially. If it's not held in that state long enough, it begins to undergo thermal expansion and blow apart before enough material reacts to get that big blast and mushroom cloud. Even when done right, at least in those early devices, most of the material did not fission. Something like 2 out of 141 pounds of uranium in the gun design and a bit more than 2 out of 14 pounds in Fat Man. It is truly amazing they managed to pull it off back then. The reason we did and the Germans didn't is that they didn't pour the massive resources into the problem early on enough. It required enormous infrastructure to produce those small bomb cores and armies more to sort out the technical problems of explosives and detonators etc.
@@kenofken9458 ah I didn't know that either. I read a kid's simplified science book when I was 7 which said that the hard part is making the material but once you put enough together in one blob it will be a massive chain reaction unless you slow it down with graphite. One of those pieces of grown-up knowledge that upon examination, turn out to belong to a child. e.g. how it was extremely important not to walk into mummy and daddy's room without knocking on Saturday morning because they need their extra sleep
A very good explanation. Especially about the Lanthanum testing. I'd been puzzled by that for ages. Other source mention the Lanthanum tests, but don't make any attempt to explain it. One question. Are you sure the alpha particle count was being measured when comparing the Pu samples? Surely the natural decay of Pu would be releasing lots of alpha particles irrespective of spontaneous fission. I thought it was the neutron count that was the problem. Spontaneous fission releases neutrons not alpha particles.
A factor not mentioned here in Pu has a huge number of possible crystalline configurations at room temperature. This makes it's material properties really hard to predict. Oh, and as it degrades it changes as well. So a functional mass doesn't stay functional. Good times.
I already knew most of the information in this video. But the way everything was covered in one video has put a bunch of pieces into place for me. Thank you
You do a great job of affirming Feynman's ""If you cannot explain something in simple terms, you don't understand it". Maybe this video could run before the Oppenheimer movie :)
A person might not know how to speak and still can intuitively understand many many different concepts. Ive heard that quote and variations credited to various people but it's just stupid
The gamble was the plutonium core bomb. The enriched uranium core bomb was known to be functional, so much so that it was never tested and the first time an enriched uranium core bomb was set off it was on a military target. The issue with the uranium bomb was the difficulty enriching (e.g. separating enough Uranium 235 from the Uranium 238 it's mixed with) enough uranium to make the 50+kg of material needed for a critical mass. Plutonium, on the other hand, is created in a breeder reactor and is much easier to obtain once a functional reactor is in operation. So, the plutonium is a lot easier to obtain but the design of the bomb that can use that plutonium is a lot more complicated. Turns out we're really good a figuring out ways to kill each other so they figured out how to make both options work...
At 10:06, the narrator says "Now humanity had the power to annihilate itself" -- but first we would defeat Japan in the Pacific Theater of World War II, and shorten it's devastating effects. And had we not pursued every means of winning WWII, we could be speaking Japanese, or German today. The bomb wasn't responsible for *gaining the power of self-annihilation* - No, no, no - Only the unbridled ambition of slighted Japanese and German national pride, decades earlier, followed by the inevitable campaigns of rebirth via conquest were responsible.
@@Feinrizulwur Notwithstanding the vagueness (of who "we" refers-to in your reply, especially since your screen-name kinda seems Germanic), your post seems quite dark, as in "Film-Noir'.
This is the kind of stuff I wanted to see in the oppenheimer film. The scientists running into problems and then solving them. I'm sure there were thousands of problems like this that they had to solve. Instead it was a movie about the morality of using an A bomb. Oh well.
That's because the movie, "Oppenheimer" was based on one of the biographies of Oppenheimer, "American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer." It's Oppenheimer's story within the Manhattan Project and his later life. If you want to learn about the entire Project and the development of the atomic bomb, two books are very good. The first is the classic by Richard Rhodes, "The Making of the Atomic Bomb." The second is more focused on science, "Manhattan Project: The Story of the Century," by Bruce Cameron Reed. A third is "Racing for the Bomb," by Robert S. Norris is also very good.
John Von Neumann might have been the smartest person to have ever lived. SPOILERS: . . . . . that he isn't featured in the Oppenheimer film is the only disappointment.
The 7 hour 1980 (I think) BBC MOVIE (ONE HOUR PER NIGHT FOR 7 WEEKS) WAS absolutely mesmerizing and went into immense detail ….I still recall the British scientist bring up “shaped charges” as the solution to the plutonium bomb and I recall Edward Teller explaining to Oppenheimer his solution for the “super” as he described it. ….it was a wonderful series and I didn’t miss a minute of it.
This is always done. The MASS does not change. You are not compressing it to a critical MASS. If you start with 2kg of mass and compress it to a critical density you still have the same 2kg of mass.
Critical mass is the MASS NEEDED to sustain a nuclear chain reaction. You can lower the critical mass needed by condensing the material, increasing its density. So you basically are compressing it to a critical mass because by compressing it, the critical mass needed is lower. Critical mass in and of itself is not a unit of measure.
You are compressing it to a critical density in a bomb which is a relationship of the surface area to the mass of the nuclear material. This is to reduce the number of neutrons that escape through the surface and thus allow them to engage in sufficient numbers in fast fission chains to allow a nuclear detonation. During the compression the mass does not change, just the shape and the density.@@aarong8457
Thank you for that very enjoyable and immersive tale. Your story telling skills, and smooth presentation, and background info, synergizes so well with recently watching the Oppenheimer movie.
Shaped charges were used in Britain from at least as far back as the first world war. The BBC Oppenheimer series of the 1980s suggested that it was a British contribution to suggest using shaped charges, which were unknown to Seth Neddermeyer.
The British physicist who suggested the shaped charges (lenses) to Kistiakowsy and von Neumann was James Tuck. He had specialized in explosives and shaped charges while working in Britain and was part of the British group sent to Los Alamos along with Rudolph Peierls who asked that Klaus Fuchs also be sent as he needed an assistant.
I saw that entires 1980 bbc series and remember very when the British scientist suggested “shaped charges” as the solution …..it was a wonderful series
@@WelchLabsVideo the bulk modulus of Pu is around 30GPa, so IIRC a 1% change in volume requires a pressure of 0.3GPa. If conventional explosives have a detonation pressure of 5-10 GPa, then up to 30% volume compression is plausible (assuming linearity) Question: do you know how much they compressed the Pu to make it critical? Note: Pu is soft!
Scientists of the Manhattan project did not know, or rather, did not think, that metal could be compressed in an explosion. They started using explosives simply as an alternative to using a gun for throwing initially separated pieces of plutonium into one compact mass. It took five months before a few of them realized that pressures during these collisions were so high that it caused metal to be compressed non-negligibly. This was a huge surprise to everybody, and once Oppenheimer was told about it, the whole program pivoted to working in this direction. It took another whole year before they figured out that it was not even necessary to slam the pieces together, and that merely setting the explosives off around a solid piece of plutonium was sufficient to increase its density *enough* for exploding the bomb. This became the final design, because it was the easiest to get right, and also to understand and to do calculations for it. This may seem simple in retrospect, but in reality it was not at all obvious even to a bunch of Nobel prize winning physicists. It took them quite some time and some luck to figure all this out. Regarding the actual pressures -- since it was not a plane shock, but a converging one, the pressures were way higher, in the 500-1000 GPa range. But you cannot use bulk modulus at room temperature and small pressure to calculate compression of plutonium in these conditions. It was still considerable, of course, more than doubling the density of the metal.
Awesome video! I left the Oppenheimer movie with an itch for more technical explanations, and this definitely scratches that itch. Also, sorry if this was already brought up, but at 9:25 you say "[...] and by December of 1945, the Los Alamos scientists had a design [...]", did you mean "December of 1944"? It seems like the satisfactory design would have to be ready before the July 1945 test.
The picture at 1:20 is correct, the voice-over wrong: the moving part in the gun design, Little Boy, was the female part, which envelooped the stationary, projecting one. This is because to be stable down the barrel it was helpful to be in circumferential contact with it.
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
Absolutely wild and related story from The Making of the Atomic Bomb by Richard Rhodes. As of a week before Trinity, there were not enough quality lens castings on hand to make a complete charge. Oppenheimer also insisted on firing a “copy” of the gadget before Trinity to test the high-explosive design at full scale without the Plutonium. Each unit required ninety-six blocks of explosive. A PhD physical chemist on the Manhattan project (George Kistiakowsky) recalled his solution:
“In some desperation, I got hold of a dental drill and, not wishing to ask others to do an untried job, spent most of one night, the week before the Trinity test, drilling holes in some faulty castings so as to reach the air cavities. indicated on our x-ray inspection films. That done, I filled the cavities by pouring molten explosive slurry into them, and thus made the castings acceptable. Overnight, enough castings were added to our stores by my labors to make more than two spheres.”
“You don't worry about it," he added, "I mean, if fifty pounds of explosives goes in your lap, you won't know it."
lol that's biggest "Either I'm right or it's no longer my problem" in history
That's one of my favorite non-fiction books. He really describes how the run up to fission came about, and how Oppenheimer, Kistiakowsky, Teller, Bethe came up with the design. How Seaborg synthesized/created/bombarded U238 to make Plutonium. How Fermi's "Pile" went critical. How Groves built cities of factories. But also how the physics of the early 20th century involved the Cavendish with Rutherford. Chadwich and the neutron. It's a fantastic read, and really describes how the 20th century came to be, as well as America's hegemony. He won the Pulitzer for it.
One of the best quotes!
Even the brightest minds have their YOLO moments.
@@321sandspur3
😊😊😊I
Nomoo niloop
😅 0:15 ni
Mop mop ml
As a modern age scientist with all computer power on his side I cannot say how I admire these scientist to get it done by their own brains and hands and based on the minimal amount of empirical data available.
von Neumann was literally coming up with the von Neumann architecture and pioneering the modern computer at this time. I’ve read that nukes and computers basically arrived as technologies at around the same time, as early computers were needed to solve all the mathematical and numerical problems on the Manhattan Project.
(Edit) Correction, not on the Manhattan Project, but after for making all the other nukes that were made after the war.
@@topdog5252 The ENIAC, von Neumann's first general-purpose computer, went operational in December 1945. It was originally designed to calculate ballistic trajectories of artillery. It was used for the nuclear program after the war, as there was no need to calculate ballistic trajectories in December 1945. The Manhattan Project relied on IBM punch card systems that were originally designed for business purposes.
After the war, the US nuclear program and the development of more and more powerful computers was highly interlinked. Even to this day! Guess who has the largest supercomputers in the world: The US Department of Energy.
Truly groundbreaking. ( no pun intended).
And with a timeline that would cause me to go bald within months. Urgency seems to be a paradoxical source of success for the government, as seen during the Apollo program as well. Give them an open ended goal, and they’ll take their sweet time.
People were so excited. They could kill hundreds of thousands of people with one device. What an accomplishment, they thought. People were impressed.
I've never seen a youtuber end a video like that. Thanks. No shameless plugging. No feeling the need to rehash what we just saw. Just a few seconds of a blank screen to give the viewer a brief uninterrupted moment to let the point sink in.
True
When nothing else works, create a model based on small masses and springs. Everything is a simple harmonic oscillator at small enough scales.
That is not a comforting thought
string theory go brr
@@trevordillon1921 lolll
“Assuming a spherical cow…” 😂
Well said.
"The scientists had to flee the scene in their tanks" is an amazing sentence
I worked on Cuba District Wildland Fire and talked to some folks who worked containing the Los Alamos Fire and they said that many places were still closed off and they saw some very strange colored flames from. The ground fires.
Ironically, a run away reaction. ;)
@@rogerkearns8094nice
You know a problem is difficult when even in the 40's they resorted to brute-forcing it with computing power
Haha true!
Yes indeed, especially when it was human “computer” power too! Humans and slide-rules and adding machines. That’s how iterative simulation processes were often done well into the 1950s. And apparently some early models of IBM mechanical computers and card punch and sorting machine.
The US was desperate to get this weapon first, so any amount of effort was deemed appropriate.
The US was rightly scared sh**less. Because even if such a weapon was never directly deployed against the US, if Nazi Germany developed it first and simply held it as a threat, America also feared a total loss of Europe as a trading partner to a new fully “autarkic” Nazi-German ruled Europe which would have been disastrous for the future of the US.
It should be noted too that the Nazis ALSO had full access to proprietary (often custome designed) IBM computers and card punch and card sorting technology … and even clandestine technical support for this equipment throughout the war from IBM employees itself. This should have been a scandal, and still to this day few people know much about it.
I’m unaware if, or how much Germany and the Nazi scientists chose to use their proprietary IBM equipment in this way, to aid in physics, or bomb or rocket or aircraft design.
The Nazis have been documented to have used their IBM equipment to aid in their efforts to keep track of and to purge “undesirable” people of all kinds in the German state, and to organize the surveillance, detention, and shipment of these unfortunate people in a highly efficient manner to the “appropriate” work or death camp. Terrible. Scandalous.
To my knowledge IBM still hasn’t made a full accounting of this German activity themselves during WWII and has left it to independent historians and journalists to reveal how the company aided the Nazis and even took great pains to circumvent the slow-to-come US government regulatory efforts to stop their support of or doing business with an enemy combatant state that IBM executives were aware were using their equipment to design and enforce social policies that what would eventually come to be called genocidal.
I’ve not encountered any historian’s work on the amount of computing power supplied to Los Alamos and the Manhattan Project by IBM; it would no doubt have been quite helpful and much faster to run complex mathematical simulations of implosion on their proprietary equipment!
Truely, we stand on the shoulders of giants!
idk if id quite consider mathematical optimization as brute force, but would of been tedious AF
@@WelchLabsVideo attack ad-eminem and tu-quoque fallatio, your video is wrong and your argument is exposed
Can you imagine figuring this out in the 30s and 40s with just basic photography, pen, and paper?
Well, 40s anyway
yes, considering chat gpt hasn't already made a new groundbreaking proof
People seem to forget that machines replace simple tedious tasks, think of a bottle opener, could you imagine a factory opening and closing a million bottles in the 1800? I can, just take 100 people in a factory line doing 10.000 tasks a month, 333 a day, 26.smt a hour, for 12 hours everyday
(yes, doing algebraic calculations guided by a scientist is simple)
Humans using their brains. Imagine if they just had Excel.
My neighbor was an EE who worked at Oak Ridge. He could only tell me a little of the work he did, but he got a secret $1 award for detecting pipe weld issues (and photo with a general). Lol. After he passed, he left his utility room open outside where he stored tools and old books. I went in to find a rasp tool he had and saw a book called Nuclear Reactor Design. I’m a pretty decent scientist, but I was lost after page 4. So complex and I admire the folks who developed those technologies.
I was a Naval Nuke. The heat transfer problems are intense. The cladding problems are intense. The radiation problems are intense. And I barely got a taste of that (enough to be an operator).
Even the teaching of the theory necessary to learn the methods needed to discover the means to success is still classified. Their path to success, to this day, is only guessed at.
@@msimon6808secure control rods, axe man. Every visit LR1?
@@canberradogfarts After a few beers, he told me a little more about strange lights in the sky and some other oddities. He would always stop himself and say “that’s all I can say about that “. I didn’t press him, he was so sweet.
What was your major?
Every time I hear about him I am more convinced that the US owes its political primacy in the late 20th century to Von Neumann. The man was a beast
He was a good mathematician, for sure. Not sure about his intuition as a physicist. Maybe he was misunderstood at the time, but the way we teach QM today (poorly) might have something to do with von Neumann's own misunderstanding of the physics behind the theory.
Good mathematician ? That qualifies as a supreme understatement . Who else but von Neumann had as much impact on so many fields as he did ?
@@michaelblankenau6598 Euler. Dudes... why do you have to prove that you don't know anything about the history of mathematics? ;-)
@@schmetterling4477 And why do you have to prove that you don’t know anything about Von Neumann ?
@@michaelblankenau6598 Awhh... Dude, now you are just feeling sorry for yourself. I will give you more attention anyway. You clearly need it. ;-)
Quite possible the most articulate and informative RUclips presentation on the Bomb and the Oppenheimer story.
Yes! I was thinking exactly the same thing!
100%
Yes. Now I dont have to watch the movie and give money to the leftist pedos in Hollywood.
As a nuclear specimen collector and history enthusiasts.....and someone who works in photonics, I've always been stunned at the optical lens principles utilized in the explosive lense tech. Super cool shit
I know right!?
Yeah, functionally it's the same type of math, just being applied to sound waves instead of light.
That's far out that matter and light both can use similar lens logic. Makes you wonder if that is a coincidence or if it tells us matter is maybe not so different than light after all.
@@brokentombot I don't think it points to a relation between matter and light. We see this type of thing all over the place when we are dealing with what I believe are typically called emergent behaviors/properties, when complex small scale interactions give rise to more generalized large scale phenomena. I think it points more to the incredible power of mathematics (specifically calculus) and our ability to build models from approximations.
For example the equations that are used to model viscous fluid flow can also be used to model the movement of large crowds or traffic through highway systems. This doesn't mean that humans and cars are related to fluids in some way. The small scale interactions that are occurring between the molecules in a fluid, the people in a crowd or the cars on a highway are all obviously very different. To get the most accurate prediction of a fluid or crowds behavior we would need to be able to simulate each interaction between every particle/person, which would be incredibly complicated and is impossible for systems with a large number of particles. However we can make abstractions that can be used to approximate the large scale behavior such as how rapidly a disturbance (like someone getting shoved) will pass from person to person through a crowd, or how easy/difficult it is for people or cars to move past each other. These would be equivalent to the speed of sound in a fluid and the fluids viscosity respectively. By observing crowd behavior and traffic data we can make these abstractions and apply the same types of equations we use to model fluid and get very good approximations of a crowds behavior or traffic flow.
So it's not that light and matter are in some way similar to each other, rather the emergent behavior of light wave propagation through different mediums and the emergent behavior of sound wave propagation through different materials both fall under the same problem type and can be modeled with the same category of equations. What causes these behaviors though is vastly different.
Sorry for the obnoxiously long reply, numerical methods (computational modeling, or just using math to simulate complex system behavior) is a passion of mine, it was hands down my favorite subject when getting my engineering degree.
The irony is that newer ones use a small q-switched neodymium yag laser to trigger the implosion. The laser is made by Kigre corporation and is the same one used in eye surgery lasers for treatment of glaucoma. The laser pulse is delivered to the explosive directly that detonates as an acoustic wave shaper converts it into a structured force pattern, as you said is very similar to optics. The beam is split to 3 beams. 2 hit the implosion mechanism while the third one hits the explosive on the back of the neutron generation module. The design is 💯 percent fail safe, no risk of mistake. Security on the other hand. I truly hope they do not lose one of them. In theory it could be hot wired using the guts from a cheap camera flash unit.
Just WOW!
This was great story telling, animations, stop motions, everything with enough scientific and mathematical explanations
Thanks Welsh labs
Glad you enjoyed it!
@@WelchLabsVideoDo any of you productive people ever have to struggle to develop any memorizing methods (like zettelkasten or some other fancy note-taking system) or is accurate memory as natural as breathing to you? Furthermore, do you ever struggle to understand something for a longer time or is clarity and sharpness of thought also natural and effortless?
Correction for 4:51
In the second equation, b + r should equal
√ (x²+(r+y-h)²)
instead of
√ (x²+(y-h)²)
The fourth equation would also need correcting to:
√(h²+x²)/v_f + (√(x²+(y-h)²)-r)/v_s
Came here for the same thing.. (also it was even worse, it was √ (x²+[y-h²(x)] ) not √ (x²+[y-h(x)] ² ) )
Didn't want to say anything. Glad, you said it bro. Right, guys?!?!
🤓
as a nuclear weapons tech/engr.... I love you math guys! It was always my weakest link.
🤓
That is the best explanation of the Pu implosion problem I have ever seen -- the visual elements you used to explain the problem and it's eventual resolution made it clear and easy to understand.
Indeed. Sub added.
This is a beautiful explanation in near laymans terms of how implosion resulted in atomic detonation. Very well done, and thank you.
The detonators had to go off within about a microsecond of each other. That explains all the coax swarming around Fatman. Very impressive for 1945 tube technology.
Yeah, that feels like a trivial problem to me ... until, ... wait, what do you mean I can't use a transistor? Those aren't invented yet? So what the hell do we switch with? Glass tubes? Uhhh.
Yup they were fired by 4uF 5.2kV capacitors each piped into that coax by a KN-6 switching tube that was originally designed to be used in a strobe lamp. Now they have them with two laser pulses triggering a couple very well made shaped charges that compress a double paraboloid core into a sphere. Let us pray control over one is never lost. 🙏
@@christopherleubner6633what?
@@Gmoney00718 He's very clear in what he said.
@@Gmoney00718 big bomb got better. scary.
Today, about 8 hours ago, I saw the film "Oppenheimer" in IMAX 70mm. There's a lot to say about the movie, but this post is about the video above, "Oppenheimer's Gamble - The Plutonium Crisis". I can't thank you enough, Welch Labs, for adding so significantly to my understanding of what the Los Alamos team was doing. Well done!
the story is the same even in digital cinemas
🤣😂🤣
The X-ray pics are new to me. I've never seen them in all the documentaries on the building of the plutonium bomb that I have watched and rewatched. Thanks for including them.
Clearest and richest discussion of the implosion problem and its solution I've seen. Thank you.
Wow, that was the most detailed and well explained process of the plutonium detonation that I have seen on RUclips. Bravo!
Thank you!
Hand calculated finite element analysis sounds like one heck of party. I like that they dumped it on Feynman.
Actually, when the calculations became too complicated for von Neumann, he called in Stan Ulam. At that time Feynmann was a prodigy but not anywhere near the level of either von Neumann or Ulam. Ulam invented the Monte Carlo method of analysis. He was also the person that found the flaw in Edward Teller's design of the hydrogen bomb which is why it became the Teller - Ulam design.
That was more common than you might think 40 years ago
They were called the greatest generation for many, many reasons. Ingenuity and genius under enormous pressure are just some of those reasons.
Amazing video. Your channel is quickly becoming one of my favorites. As an engineer this is exactly what I had been looking for. Absolutely loved that you didn't shy away from math. People don't realise that engineering problems are actually just applied math problems. Wish they had done this in the movie, too.
@@Jamey_ETHZurich_TUe_Rulez if AP levels of high schools then yeah
I'm not STEM oriented at all, but was able to get the gist here, and found it way more interesting that the middle :45 of Oppenheimer. Not sure why Nolan opted to brush over so many of the tech obstacles the team faced. The film made it seem like it was mostly politics. Thanks for sharing. And for torching a nice piece of wood.
Thanks for watching!
I think it was because he wanted to make it about Oppenheimer and his internal struggles mentally instead of the technical marvel he created, and probably for the better because it is some pretty advanced stuff even today.
You all are producing some high quality stuff here. Wish YT would have reccomended earlier.
Thank you!
This might be one of the most educating 10 minute videos I've seen well done, the ending was cold!
Klaus Fuchs , who was passing on information as a Soviet spy was also an important contributor to solving this problem. He published still classified papers on the theory of jets and explosive waves. He also held patents with Von Neumann, Teller and others.
What a wonderful explanation. Many thanks. I remember working with engineers at Los Alamos back in the early 90s. They explained that they needed to CNC machine pieces to a tight tolerance and to a specific spline geometry. Now I have a much better understanding of why they needed this.
This is easily one of the most phenomenal RUclips videos I've ever watched! Excellent writing & clear narration explained complex ideas extremely well. This video gives even more perspective into the astonishing brilliance of the minds behind the Manhattan Project. Thank you for this clip!
Awesome thanks for watching!!
Nice video! However, I would push back on your claim at @1:20 that once you reach critical mass "it is basically impossible to keep it from exploding." This isn't true. If it were that easy, there would have been no need for the massive amount of scientists, money, and time for the MP to produce a bomb. A supercritical piece of fissile material itself will almost certainly fizzle out before exploding, releasing a massive amount of ionizing radiation and heat but not exploding. Once a lump of fissile material goes supercritical, the temperature of the fuel increases drastically, which actually buffers the reaction before it can explode. Almost always, the nuclear reactivity of a fuel will be inversely proportional to the temperature. The reason is two-fold: 1) faster moving neutrons associated with increased temperature are less likely to initiate fission before it exits the material altogether, and 2) thermal expansion of the hot fuel will reduce the density of the material and thus the reactivity. This will usually cause the fission events to slow to an equilibrium in a critical state or to go subcritical altogether. To get an explosion from a supercritical piece of fissile material, you have to ensure that many generations of fissile events are able to occur very quickly before these natural buffering factors cause it to fizzle. This is where things like implosion hydrodynamics, neutron initiators, and tampers had to be leveraged to actually cause an explosion. All that to say, it's actually quite difficult for a supercritical material to explode.
You seem to be educated on the topic. Is what you describe the reason why nuclear reactors improbable to explode and the worst case scenario is a meltdown instead of explosion?
I believe this has something to do with the isotopes as well. If so can you elaborate what actually makes certain isotopes favorable to explosion/meltdown (bomb/not bomb). For example certain isotopes are best for bombs and certain are for nuclear reactions
@@rinkashikachi Yes, nuclear reactors are susceptible to meltdowns, which may lead to other types of explosions, such as the steam explosion at Chernobyl. However, they are not going to explode like a nuclear weapon because of some of those reasons I mentioned. That does not mean that there won't be any explosions from a reactor or that a massive amount of radiation won't be released in the event of a meltdown. I only mean that true nuclear explosions do not happen unless the supercritical mass is weaponized. A lot has to go right for a true nuclear explosion to happen, which is not really possible in the configuration of a reactor. There just isn't enough time before the core comes apart for enough fission generations to proceed in order for all that energy to be released as an explosion.
Your question about isotopes is a pretty complex question. I probably have an above average knowledge of nuclear physics than the general public(I have a PhD in a somewhat related field), but I am by no means an expert, so take this with a grain salt. Generally, both fission reactors and weapons still use the same isotopes (U-235 or Pu-239) for their fissile fuel. However, weapons grade U-235 is highly enriched, meaning there are very few of any other isotopes present in the material. On the other hand, reactors use the same U-235 isotopes but the fuel is not enriched to nearly the same degree. Since there are other isotopes still present in reactor fuel (primarily U-238), these will absorb neutrons without fissioning and thus slow the overall reaction. Generally, I believe they want the core of a reactor to be oscillating back and forth between criticality. Whereas for a weapon, you have to have the reaction go as quickly as possible. Even with highly enriched U-235, this most certainly won't happen on its own. That is why the MP had to use things like tamper, which kept the core together for a split second longer using its own inertia before the reaction blew it apart (it also reflected neutrons that would otherwise be ejected from the core).
Using Pu-239 is more complicated since it does not exist in nature, and is either synthesized from Uranium beforehand or in real time within a reactor.
Finally, I should mention that fusion reactors are sort of the desired future technology, as they do not release fission products and can produce a lot more energy efficiently. These will use different fuels altogether, usually light isotopes like those of hydrogen. To my knowledge, these are still a long way off.
Again, I am no expert. I am happy for anyone to correct any error I may have made.
The sentence you quote is taken out of context and is also badly worded in the first place The issue was the Plutonium-240 impurity in Plutonium-239. The supercritical configuration needs to be assembled extremely fast to prevent a pre-detonation caused by the Plutonium-240 impurity before the assembly is finished. This made the gun-type design infeasible.
what an amazing set of videos you have just put out. Really well done, unique, informative, and highly digestable. Great job!
I was born in Los Alamos in May 1944, where my parents were both employed on the Manhattan Project. I have read and studied extensively what happened there; while I understood the theoretical problem inherent in plutonium and how they solved it, I never understood how technically they got from the theory to the engineered solution. This is easily the best video I have seen on this subject. Great job!😂
Happy 80th birthday when it comes. It was Mick Jagger's this week.
Does your birth certificate list "P.O. Box 1663"?
--
@@personanongrata987 No. My birth certificate lists as my place of birth as 1Sandoval County Rural.” I think I may have been born too early for the famous 1663 designation. There are a couple of birth certificates in the small Fuller Lodge museum at Los Alamos, and both have birthdates after mine. Several years ago I had to obtain a birth certificate from the State of New Mexico for f a claim my brother, sister and I filed against the federal government for our mothers death from radiation exposure. That certificate simply states my place of birth as Los Alamos.
They jad bennn developing explosive lenses for other uses e.g. armour piercing shells.
The UK team contributed much of this from theur naval programs.
Wow fantastic post. Clear no BS explanation of the problem of implosion
Wow! Your lecture made my brain glaze over. My knowledge of nuclear physics would barely gotten me a passing grade in a 2nd year of college. But you made it very understandable. This was a well-made explanation and educational to the learned and the layman.
Excellent video. Very interesting, informative and worthwhile video.
He also talk with John Von Neumann to about this. Got your facts straight, ok
This level of theoretical detail doesn’t exist anywhere on RUclips. Well done!
my videos have more detail i bet
Just watched Oppenheimer and this was a palate cleanser for actually mentioning von Neumann
I believe the electric device developed is called an SCR. Simular to a transistor and kinda like a switch. Very heavy duty and durable as well as Ultra reliable. The SCR currently is the heart of modern high efficiency electric systems. Inverters are made using them. Just incredible that all this crap was done long hand.
I suspect the fast electric switching device was the thyratron / krytron. SCRs emerged in the late 1950s. I have a 1960 inverter which I believe uses SCRs. In the 1970s bipolar transistors took over, devices like the 2N3055 not being uncommon. Then FETs, and now IGBTs.
Thanks for the informative video. [One correction: @9:27 obviously must mean "by December 1944" not "by December 1945."]
he said "by the summer" , not "by December", I think
@@hobbycatkid I think you're right as this happens right before the Potsdam conference of 17 July 1945
it sounds a lot like "December", but I'm pretty sure he's saying "the summer"
This is the clearest explanation I have seen of the Manhatten Project engineering, particularly the explosive lenses piece - and you have incidentally illustrated why the cost was so high. Very well done indeed. Many thanks.
Never was and never will be a higher concentration of the world’s intellect than lived together at Los Alamos at this time.
Damn, Scott Manley and you made a video on the same topic within days. It's fascinating to see different perspectives on the same idea.
Veritasium too, my guess is all of them are trying to capitalize on the release of the Oppenheimer Movie
@@jamcdonald120 I was specifically talking about the explosive lenses. Did Veritasium make one about this too?
@@mickeyhage Nope. He glossed over the technicalities and focused more on Oppenheimer himself. If you haven't seen it it's actually a rather good biography.
At least 5 or 6 other YT''ers did., even theGrahamNortonShow ..also an interesting long-form take from U_Minnesota ruclips.net/video/_TQJEMC6mkk/видео.html (thank me later). Too much of a coincidence for this to be unrelated to the movie-launch; but did the movie-studio ask these science-influencers to create the videos, or is it just the zeitgeist? We shall never know ;)
This is the kind of detail i have been looking for for years. Thank you for spelling this out so well.
I don't know what was cooler - learning about the RaLa experiment setting the forest on fire (I didn't know that happened), the kitty in the background at 7:19, or the tiny fire extinguisher. Great video!
The squished plutonium cutouts were really well done!
Thanks!
3:07 - LOVE the little fire extinguisher!! AND love the fact that you answered all of my unanswered questions on how the bomb was designed!
In his auto biography Feynman writes about being sent to oak ridge to inspect how the uranium was being stored, they kinda forgot about ataining a critical mass he speaks about how they narrowly escaped a disaster, the inspection was very timely the book is titled " surely your joking Mr. Feynman it's an easy read not at all dry fascinating the man was amazingly down to earth given his status.
Wasn't it that there were two vats of liquid uranium solution and people put them on their side of a wall, not realizing that neutrons can go through walls. I seem to remember something like that, perhaps from Rhodes' book.
Nice video! I have seen the "implosion" method being talked about in many video but never a detail description of what it is. I assumed it was just a big circular TNT wrap around a core. It turns out the method is way more complicated than expected.
When Manhattan project scientists started to work on the bomb, they also thought that it would be as easy as wrapping some explosives around a shell of nuclear material. The idea was to collapse a tube of plutonium into a ball and make it super-critical. All this stuff with compressing plutonium, explosive lenses etc took enormous effort to figure out -- it was not obvious at all even to a bunch of these best in the world scientists.
Check this one out, it's much better and quite a bit more historically correct (I'm a physics prof). I'm getting sick of everyone on youtube over-crediting Oppenheimer:
ruclips.net/video/H1QuZ6nsC68/видео.html
@@cogoid yes, absolutely. People really underestimate how many scientists actually worked on Trinity, and the interesting thing is that so many people made necessary contributions to the function of the bomb.
Richard Feynman was a genius. He discovered the cause of the Challenger accident on live TV all while he was dying from cancer. He was also a great safe cracker and musical bongo player.
He also learned "Game" from a Master. Before any but a few knew it was a thing.
he did NOT , the engineer mcdonald raised issue and RF just demonstrated it on TV
@@nobonespurs Factually, it was Donald J. Kutyna and Roger Boisjoly who steered Feynman towards the faulty clevis design. Sally Ride gave Feynman a peice of the O-Ring. He was the one who masterfully managed the ice water and C-Clamp demonstration so a non-technical person could understand what happened in the cold weather.
@@retiredbore378 Am I correct to say that a similar problem was found at Boeing after a couple of newer model planes crashed? Management and sales had promoted a product (to the delight of executives and shareholders) that engineers had serious doubts about. Serious enough that internal document trails revealed quite a dark streak of gallows humour concerning the safety of the aircraft, concerns that were shown to be well founded.
@@drn.o.thunderfinger9738 this is why engineers need to be in the C-suite of any company that makes a physical product. The more high risk the product is to human life if it fails, more engineers should sit on the boards.
I learned about implosion mechanism in the TV show Manhattan. Very good series
Best video yet in this series. great work
Thank you!
I'd love to see a sequel about Ivy-Mike. There are so many documentaries and movies about the Manhattan project, and rightfully so. But, in the midst of the hype, people forget that bombs which are tens of thousands of times more powerful were developed in the 50's thanks to the similarly fervent engineering efforts to build a hydrogen bomb. And I'm curious what Oppenheimer thought about hydrogen bombs. Or that particular test.
when you watch the movie you’ll know👍🏾
Oppenheimer was against the "Super". Teller pushed the idea after the war ended. I love the Teller interviews.
Oppenheimer feared the creation of a US hydrogen bomb would encourage a more feverent and dangerous arms race. Despite initially supporting the development (or rather not being opposed) he thought about the trinity test and the subsequent deployment against Japan, and thought something like a bomb 1000x bigger than that would destroy the world
@@maleprincess62 he might one day be proven right too.
Famously opposed the Super - he foresaw the Cold War arm's race that continues today.
See, I went to Oppenheimer expecting more detailed information like this but it really came up short. I didn't realize it was based on a biography and as such was literally just about his life, warts and all, rather than the process by which the bomb was built and how a nuclear weapon operates.
Yes, I've watched several RUclips videos which have clearly explained stuff that the movie I watched on Monday, glossed over. And when they did explain in the movie, it was basic, GCE O-level physics I did 50 years ago. Thank you RUclipsrs for your videos
I was disappointed that Apollo 13 never mentioned how hydrazine is made.
As I understand it, the explosive lens design was invented in the UK, where HM Government was expecting some quid Quo Pro, but did not get any. So the UK developed the Blue Danube free fall bomb to be carried by the RAF's V-Bomber force. There is a very interesting document that explains this:- "first-waltz_UK_A-bomb project" which can be found with google. I am not sure if the original idea came from James Leslie Tuck OBE, (9 January 1910 - 15 December 1980) but I am pretty sure the explosive lens was a UK thing. The wartime UK A Bomb project research and the code 'Tube Alloys Ltd' and had succeeded in solving a lot of the theoretical work by 1943. Watch:- Equinox. A Very British Bomb
James Tuck was a British physicist assigned to the Manhattan Project at Los Alamos. Tuck knew von Neumann was working on shaped charges for the implosion design, and is the person that suggested the explosive lens design to von Neumann.
@@buckhorncortez The French went on to develop their own independent A-bomb program- but they didn't have anyone at Los Alamos, did they? (or any spies like the Russians to pilfer the data)- how did they do it?
Yes all the Brits that helped the project gets airbrushed by US so it we're led to believe that the Brits contributed NOTHING to the bomb!
The UK had a significant role in the shaped charges, explosive lenses, and micro switches to exactly time each detonator. It was recognised (lightly) in the 'Fat man and Little boy' (aka 'Shadow makers') 1989 film. My dad worked on the micro-switches, and like any good engineer, guessed what they must have been for from the specs. Thank you for this wonderful summary
They are tubes called krytrons and sprytrons. They can hold off a lot of voltage and can turn on very quickly. The krytrons are krypton and hydrogen filled devices that create an arc like a thyratron but quickly. The sprytrons are similar but have a vacuum inside. When fired a fine plasma is created from the two trigger electrode pins and it causes a vacuum arc inside. These are quicker than krytrons but are one shot devices.
@retiredbore378 sounds like EG&G part number KN-22. Krytron tube. Had a similar issue with them for a holographic laser service set. Was used to fire off the electro optic q switch module in it. Were irreplaceable for the application too. Two shots user determined of 4nS pulse duration by up to 1mS separation.
A lot of that help came from Klaus Fuchs.
I'd argue the British magnetron was a bigger invention
@@kimziffer7259 In terms of return on investment, certainly!
Von Neumann, what a mind. Great book "The Man from the Future" about him.
Guy was such an absurd legend.
Many says he was the smartest man ever walked on this planet.
When Nobel prize winner Jenő Wigner was asked how it felt to work with so many genius like Einstein, Heisenberg, Fermi, Bohr.. His reply was epic: I only knew one genius: Naumann
Paul Dirac would argue with that
The high spontaneous fission rate resulted only from the Plutonium 240 contamination in the reactor bred samples, Pu-239 itself could work in a assembly type bomb.
they likely didn't learn that until later during the cold war, and if they did know they couldn't get the isotope purity they wanted.
Great video! Momopou's music at the end is a great finale.
Thanks!
What a superb ending to video , poignant music gradually fading in during the outro narration followed by a simple fade to black and 5 second reflective moment. Like.
Thanks! Yeah I love working on ending vibes.
As a retired commercial system software developer, John von Neumann authorship of the stored-program concept makes him my hero. Having a mathematics degree, I also respect that he, along with Osar Morgenstern, created a new branch in mathematics called game theory. So his contribution to the hydrodynamics of the implosion bomb is just another way in which the man changed the course of history, he dying 37-days after I was born.
The mathematician who invented the Monte Carlo method was Stan Ulam. Ulam was also the person von Neumann requested to be assigned to the Manhattan Project when the calculations became too difficult for von Neumann.
I learned to play Erik Satie's Gnossienne No. 1 on the piano, and now can't help but notice it everywhere in videos all over.
Nice! Hard to play?
@@WelchLabsVideo I think it's hard to get the subtleties right. I play it a lot more rubato than I usually hear it.
Excellent video that was super interesting and cool to watch! Im a 1st year applied physics major and the Manhattan Project is initially what fascinated me about the field! Thanks for uploading!
Astonishingly high quality presentation.
Thank you!
Narrator is excellent and very knowledgeable
Man this was interesting. I knew about the implosion method and how difficult it is to implement, but I wasn't aware of details of design and measurements methods.
I'm with everything except the part about "you see that solid metal ball? It's made of some of the densest material known to man... And we're gonna squeeze it perfectly to a fraction of it's size"...
The water in the hand thing was good but I think a little short ended - would have been useful to remind there that water is deemed incompressible... And something even *less* forgiving is in play.
Obviously that shit works because that's the only thing that changes to set the damn thing off... And they definitely go off 🤣
Thanks!
A brilliant explanation of an incredibly complex problem. I love this sort of content. Thank you for a perfectly sized video!
Love these videos, please don't stop making them :)
Will do my best
7:00 How did they stored the captured data from the sensors to analyze the implosion coherency? This is a high speed signal, and puts instantaneous glitches on the Oscilloscope CRT. As far as I get it from the depiction from the video, they were using vacuum tube analog oscilloscopes. Thanks for the answers in advance...
That’s a great question - I didn’t find a good answer in my reading - beat account I’ve found is I’m the book critical assembly.
Analog storage oscilloscopes are a thing. They use a special CRT that can first write a trace on the screen (one-shot), then refresh it with a low-power "flood gun". The display can't be maintained for very long, but long enough to get a photograph for later analysis.
That said, I don't know whether they were available in the early 1940s, nor how they could have displayed traces from multiple sensors at the same time, so perhaps some other technology was used.
@@DonDueed Thanks for sharing your knowledge. It seems the devil hides in the details. What these scientists achieved in the 40's is remarkable....There are a lot of things to be learnt from them.
SPOILER: I still wonder why Jon Von Neumann didn't appear in the film.
He was a Nazi
An absolutely beautiful explanation. Clearer than ANY I observed prior to this video. My sincere compliments!
Amazing video, very well explained and illustrate, really didactical.
Glad you liked it!
Pedantical, too.
--
Phantastic. I saw Oppenheimer the movie and would rate it 1/10. Like it literally doesn't go any lower. The director is proud of 100% no CGI and used a chemical explosion and some overexposure to capture the moment of the bomb. I wonder what kind of people are content with this movie. I guess the kind that never watched youtube on that subject.
Also highly recommend Veritasium and a bunch of others channels who showed various facets of the bomb.
I could never understand why it would be hard to design a bomb once you've made material that wants so badly to explode. Now I'm amazed they managed at all especially upon first dress rehearsal.
The problem is that the fissile material, whether uranium or plutonium, doesn't really want to explode. It wants to undergo fission reactions, but only so long as it remains a critical mass. The only way to get it to explode is to reach a supercritical state so that the number of fissions increase exponentially. If it's not held in that state long enough, it begins to undergo thermal expansion and blow apart before enough material reacts to get that big blast and mushroom cloud. Even when done right, at least in those early devices, most of the material did not fission. Something like 2 out of 141 pounds of uranium in the gun design and a bit more than 2 out of 14 pounds in Fat Man. It is truly amazing they managed to pull it off back then.
The reason we did and the Germans didn't is that they didn't pour the massive resources into the problem early on enough. It required enormous infrastructure to produce those small bomb cores and armies more to sort out the technical problems of explosives and detonators etc.
@@kenofken9458 ah I didn't know that either. I read a kid's simplified science book when I was 7 which said that the hard part is making the material but once you put enough together in one blob it will be a massive chain reaction unless you slow it down with graphite. One of those pieces of grown-up knowledge that upon examination, turn out to belong to a child. e.g. how it was extremely important not to walk into mummy and daddy's room without knocking on Saturday morning because they need their extra sleep
This was fantastic. Good work, man!!
A very good explanation. Especially about the Lanthanum testing. I'd been puzzled by that for ages. Other source mention the Lanthanum tests, but don't make any attempt to explain it.
One question. Are you sure the alpha particle count was being measured when comparing the Pu samples? Surely the natural decay of Pu would be releasing lots of alpha particles irrespective of spontaneous fission. I thought it was the neutron count that was the problem. Spontaneous fission releases neutrons not alpha particles.
A factor not mentioned here in Pu has a huge number of possible crystalline configurations at room temperature. This makes it's material properties really hard to predict. Oh, and as it degrades it changes as well. So a functional mass doesn't stay functional. Good times.
I already knew most of the information in this video. But the way everything was covered in one video has put a bunch of pieces into place for me. Thank you
Awesome!
You do a great job of affirming Feynman's ""If you cannot explain something in simple terms, you don't understand it". Maybe this video could run before the Oppenheimer movie :)
A person might not know how to speak and still can intuitively understand many many different concepts.
Ive heard that quote and variations credited to various people but it's just stupid
That quote is due to Ernest Rutherford, and was originally, "An alleged scientific discovery has no merit unless it can be explained to a barmaid."
@@jsalsmansounds like the main goal of science is partly to impress the people of your preferred gender 😅
@@maticz3923it is indeed pretty stupid.
I know a lot of derps that can explain how something works without having the first clue 🤣🤷♂️
@@jsalsman That one i can get behind
Science communication is important and yet extremely hard.
The gamble was the plutonium core bomb. The enriched uranium core bomb was known to be functional, so much so that it was never tested and the first time an enriched uranium core bomb was set off it was on a military target.
The issue with the uranium bomb was the difficulty enriching (e.g. separating enough Uranium 235 from the Uranium 238 it's mixed with) enough uranium to make the 50+kg of material needed for a critical mass. Plutonium, on the other hand, is created in a breeder reactor and is much easier to obtain once a functional reactor is in operation.
So, the plutonium is a lot easier to obtain but the design of the bomb that can use that plutonium is a lot more complicated.
Turns out we're really good a figuring out ways to kill each other so they figured out how to make both options work...
"...now I am become death, destroyer of worlds..."
Very informative. Really interesting. And very well done video and narration of an extremely complex subject. These scientists were truly genius
Thank you!
At 10:06, the narrator says "Now humanity had the power to annihilate itself" -- but first we would defeat Japan in the Pacific Theater of World War II, and shorten it's devastating effects. And had we not pursued every means of winning WWII, we could be speaking Japanese, or German today.
The bomb wasn't responsible for *gaining the power of self-annihilation* - No, no, no - Only the unbridled ambition of slighted Japanese and German national pride, decades earlier, followed by the inevitable campaigns of rebirth via conquest were responsible.
No, we wouldn't speak at all.
The dead doesn't speak at all.
@@Feinrizulwur Notwithstanding the vagueness (of who "we" refers-to in your reply, especially since your screen-name kinda seems Germanic), your post seems quite dark, as in "Film-Noir'.
The little fire extinguisher made me roll on the floor. Miniature safety for miniature model xD
All of what I can think of during the video is the cat in the background haha! 7:19
Nice
Outstandingly clear and smoothly delivered presentation. I had no idea such information could be acquired by a novice like me. Thanks!
This is the kind of stuff I wanted to see in the oppenheimer film. The scientists running into problems and then solving them. I'm sure there were thousands of problems like this that they had to solve. Instead it was a movie about the morality of using an A bomb. Oh well.
There is nothing moral about using the A-bomb ... it is inherently an immoral device
That's because the movie, "Oppenheimer" was based on one of the biographies of Oppenheimer, "American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer." It's Oppenheimer's story within the Manhattan Project and his later life. If you want to learn about the entire Project and the development of the atomic bomb, two books are very good. The first is the classic by Richard Rhodes, "The Making of the Atomic Bomb." The second is more focused on science, "Manhattan Project: The Story of the Century," by Bruce Cameron Reed. A third is "Racing for the Bomb," by Robert S. Norris is also very good.
The fact that they were able to pull these precise measurements off almost 80 years ago is almost hard to believe.
John Von Neumann might have been the smartest person to have ever lived.
SPOILERS:
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that he isn't featured in the Oppenheimer film is the only disappointment.
The 7 hour 1980 (I think) BBC MOVIE (ONE HOUR PER NIGHT FOR 7 WEEKS) WAS absolutely mesmerizing and went into immense detail ….I still recall the British scientist bring up “shaped charges” as the solution to the plutonium bomb and I recall Edward Teller explaining to Oppenheimer his solution for the “super” as he described it. ….it was a wonderful series and I didn’t miss a minute of it.
This is always done. The MASS does not change. You are not compressing it to a critical MASS. If you start with 2kg of mass and compress it to a critical density you still have the same 2kg of mass.
I think most people understand this, although a lot of people still vote for Trump
Critical mass is the MASS NEEDED to sustain a nuclear chain reaction. You can lower the critical mass needed by condensing the material, increasing its density. So you basically are compressing it to a critical mass because by compressing it, the critical mass needed is lower. Critical mass in and of itself is not a unit of measure.
You are compressing it to a critical density in a bomb which is a relationship of the surface area to the mass of the nuclear material. This is to reduce the number of neutrons that escape through the surface and thus allow them to engage in sufficient numbers in fast fission chains to allow a nuclear detonation. During the compression the mass does not change, just the shape and the density.@@aarong8457
Excellent commentary, comprehensively researched and presented, well done!
Thank you for that very enjoyable and immersive tale. Your story telling skills, and smooth presentation, and background info, synergizes so well with recently watching the Oppenheimer movie.
excellent mini documentary, thanks.
So many nuclear scientists popping up on RUclips that have absolutely no idea what they are talking about . Last week they was submarine specialists
Shaped charges were used in Britain from at least as far back as the first world war. The BBC Oppenheimer series of the 1980s suggested that it was a British contribution to suggest using shaped charges, which were unknown to Seth Neddermeyer.
The British physicist who suggested the shaped charges (lenses) to Kistiakowsy and von Neumann was James Tuck. He had specialized in explosives and shaped charges while working in Britain and was part of the British group sent to Los Alamos along with Rudolph Peierls who asked that Klaus Fuchs also be sent as he needed an assistant.
I saw that entires 1980 bbc series and remember very when the British scientist suggested “shaped charges” as the solution …..it was a wonderful series
It's amazing to think that mere explosives could increase the density of a seemingly dense metal (!) like plutonium.
I know right!
@@WelchLabsVideo the bulk modulus of Pu is around 30GPa, so IIRC a 1% change in volume requires a pressure of 0.3GPa. If conventional explosives have a detonation pressure of 5-10 GPa, then up to 30% volume compression is plausible (assuming linearity)
Question: do you know how much they compressed the Pu to make it critical?
Note: Pu is soft!
Scientists of the Manhattan project did not know, or rather, did not think, that metal could be compressed in an explosion. They started using explosives simply as an alternative to using a gun for throwing initially separated pieces of plutonium into one compact mass. It took five months before a few of them realized that pressures during these collisions were so high that it caused metal to be compressed non-negligibly. This was a huge surprise to everybody, and once Oppenheimer was told about it, the whole program pivoted to working in this direction.
It took another whole year before they figured out that it was not even necessary to slam the pieces together, and that merely setting the explosives off around a solid piece of plutonium was sufficient to increase its density *enough* for exploding the bomb. This became the final design, because it was the easiest to get right, and also to understand and to do calculations for it.
This may seem simple in retrospect, but in reality it was not at all obvious even to a bunch of Nobel prize winning physicists. It took them quite some time and some luck to figure all this out.
Regarding the actual pressures -- since it was not a plane shock, but a converging one, the pressures were way higher, in the 500-1000 GPa range. But you cannot use bulk modulus at room temperature and small pressure to calculate compression of plutonium in these conditions. It was still considerable, of course, more than doubling the density of the metal.
@@cogoid wow thanks for the comprehensive explanation!
Awesome video! I left the Oppenheimer movie with an itch for more technical explanations, and this definitely scratches that itch.
Also, sorry if this was already brought up, but at 9:25 you say "[...] and by December of 1945, the Los Alamos scientists had a design [...]", did you mean "December of 1944"? It seems like the satisfactory design would have to be ready before the July 1945 test.
I picked that up too. I think he was off a year.
"By the summer" not "by december" - it does sound similar
@@jimmytehgeek Ah, I think you're right! Thanks!
And to think all these calculations were done on paper tabulators and slide rules....and maybe dice ;)
The picture at 1:20 is correct, the voice-over wrong: the moving part in the gun design, Little Boy, was the female part, which envelooped the stationary, projecting one. This is because to be stable down the barrel it was helpful to be in circumferential contact with it.
I am a physicist. You did a great job.
I almost spat my coffee when he got the tiny fire extinguisher out, the little demonstrations on the table are great.