Why did they make the sleeve the "bullet" of the mechanism? It seems counterintuitive. The sleeve does not have a solid base, so it's less efficient to be pushed against by the explosive vs the solid rod component, it weighed more meaning more explosive force was required to accelerate it, it requires a heavier and larger diameter tube(barrel) for the same firing performance, it requires the target end to be aligned more meticulous, a potential failure point in the case of internal damage, whereas having the cylinder be the target could be better supported and stay concentric, the larger mass also makes it more likely to fizzle or predetonate as for the same size of all other components it should be easier to send the rod faster to get it closer before criticality.I know that implosion has its advantages but it seems like even a first time around for the gun type they could've done better.
>>64475808wow, i'm sure you're way smarter than the literal smartest fucks that walked the earth at that time periodyou should build yourself a time machine & go tell them how stupid they are
>>64475808it had something to do with the geometry of criticality, i THINK it was to make more efficient use of the material but its been a long time since i read about it
>>64475808It sucked. That's why the next iteration fired two projectiles, one from either end of the barrel. As it turned out, that sucked too, and then they moved on to implosion, which also sucked but for completely different reasons, and not because of performance.You're complaining about which horse is the best one for pulling a cart. The correct answer is a car, unless you live in the third world. Then it might make sense to speculate about horses. Do you live in the third world? What sort of horse do you favor?
The inefficiency was likely offset by a mechanism so reliable that no explosion tests were necessary.
>>64475808Reliability and ease of production took priority than making the biggest boom.
The "bullet" is a lighter object than the target so therefore will get accelerated faster meaning that overall trigger time is lower.
>>64475874>You're complaining about which horse is the best one for pulling a cart. The correct answer is a car,you have a strange definition of correct
>>64475808>Why did they make the sleeve the "bullet" of the mechanism? It seems counterintuitive.when something complicated seems counterintuitive, it's often because there is an unsatisfying answer based on some manufacturing requirement or engineering characteristic. in this case, they probably had just one big tube to put both parts in. so, the smaller part can't be used because it wouldn't touch the sides.
>>64475808There's actually a very simple, if slightly counterintuitive reason behind it. It has to do with how the reaction begins when the "bullet" reaches the "target. If you shoot the cylinder at a hollow target, the bomb tends to blow itself apart before the cylinder can get all the way inside, meaning fewer atoms get a chance to split. If you shoot the hollow bullet at the cylinder, then the shielding wrapped around the exterior of the bullet helps keep everything together (and also reflects neutrons) for a few more nanoseconds, which gives more atoms a chance to get hit by neutrons and split, which increases your yield for a given warhead mass.
>>64475808Wikipedia has good explanation for this design https://en.wikipedia.org/wiki/Little_Boy
The question is not how it works. The question is why it's not the small cylinder being fired into the outer ring, and the answer is to use the larger barrel's explosive force to compress BOTH the target AND the projectile against the end of the barrel. I hope you understand.
>>64475874implosion didnt work too well, neither did bullet; but what does that make of designs after those. what happened? t. doesnt know
>>64475808the more inertia it has the longer it will be able to hold the assembly at supercriticalitythe smaller piece was bolted to a heavy tungsten carbide reflector
>>64476144...so to be clear, the barrel cannot be any thinner if you want this compression effect. I doubt it makes a difference which shape you fire into which, there may not be much of a weight difference, but the outer ring seems easier to keep aligned as the projectile.
>>64476205>I doubt it makes a difference which shape you fire into whichA bit like adding hot water to milk in tea, it makes a difference.The nuclear reaction begins the instant both masses are brought together but it takes some small amount of time for the sleeve and cylinder to come together.It literally can't happen quickly enough for no reaction to occur before the sleeve is fully in place over the bullet so it's about minimising the effects in that brief window and also about accelerating the bullet to as high a speed as possible.As other anons have said, a hollow cylinder has a higher "muzzle velocity" than the solid core, due to lighter mass.It also helps shield and contain the reaction for a brief moment which gives more time for the mating to occur.tl:dr; sleeves go hard and fast a bit better than the core>>64475993>the smaller part can't be used because it wouldn't touch the sidesYou could just use a narrower barrel that ends at the sleeve, I don't think that would be a design problem, that barrel would be stronger and lighter too so if they could do it that way, I imagine they would.
>>64476231you cannot use a narrower barrel. compressing both parts seems very important.
>>64476309The narrow portion of the barrel only needs to extend to the entry into the sleeve, the sleeve itself could be contained within a larger chamber/barrel/vessel.Though this is all so academic because gun style bombs are obsolete for loads of reasons and the sleeve-as-bullet is the better option for unrelated reasons.
>>64476419>The narrow portion of the barrel only needs to extend to the entry into the sleeve, the sleeve itself could be contained within a larger chamber/barrel/vessel.If you do this, the gun only compresses the projectile and not the sleeve. Compression is beneficial to the nuclear reaction.
>>64476034>Only one anon actually understood my question Grim. Thanks for the answer though, and it does make sense now, the moving sleeve's angular momentum would give it slightly longer to move forward before blowing apart. Like how a soft lead bullet with enough angular momentum can penetrate steel. I feel like a dumbass for not remembering it's literally the first law of physics.On an unrelated note, to everyone else in this thread, how would you feel if you had not eaten breakfast yesterday?
>>64475808I think it having the larger diameter allowing a lower pressure explosive to accelerate it was the main factor.
>>64476231>As other anons have said, a hollow cylinder has a higher "muzzle velocity" than the solid core, due to lighter mass.the sleeve had more mass than the target spike. It weighed 86lbs to the spike's 57lbs. Please don't write lectures when you don't know what you're talking about.
>>64477028Do you have the diameter of each? I'm betting the the sleeve had lower mass per square inch of rear surface area. See >>64477020
>>64477047No, when a piston is acted on by a pressure the cross sectional area of the piston is all that matters when calculating force from pressure.>The piston force formula is F=P*A, where F is the force, P is the pressure, and A is the piston's area.
>>64475993>>64476231>in this case, they probably had just one big tube to put both parts in. so, the smaller part can't be used because it wouldn't touch the sides.I looked it up and this is probably the real answer to OP's question. They didn't make their own barrels, they just cut artillery barrels to length. It was probably a bored-out 6" coastal defense gun barrel if I had to guess. https://en.wikipedia.org/wiki/Little_Boy#Development
>>64477056NTA but that doesn't apply here. The bullet was being accelerated from behind by a flat tungsten disc.
>>64477065It does because the diamter of the projectile is the same as the diameter of the pusher plate.
>>64477056>>64477065As anons say, a larger piston means you get higher force with lower pressure, lower pressure means you can have a thinner barrel without bursting -> less weight for the overall bomb, Little Boy was already pushing it for Silverplate to carry that range.>>64475874Gun-type is very uranium-inefficient, uranium enrichment was a huge cost for the project which is why everyone wanted the implosion bomb to succeed as it's much cheaper. Modern nuke primaries are still implosion based but with some quirks about the fuzing.
>>64475808How would you keep the bullet in the centre of the barrel then? The advantage of the sleave is that it touches the barrel in some way. The barrel makes sure it stays in the right position parralel to the barrel and keeps the same orientation.The bullet would need a mechanism to also keep it on the centreline of the barrel and angled perfectly straight. This mechanism is probably heavy / unreliable / undesigned or whatever, giving the designers enough reason to opt for the other, perhaps less efficient, method.
Almost everyone here needs to refer to this post >>64476095andthe image here >>64477065for the love of god someone summon the tripfag oppenheimer in here to explain it perfectly.>THE MATERIAL WAS SPLIT ALMOST IN HALF, WITH AT ONE END A GROUP OF RINGS OF HIGHLY ENRICHED URANIUM WITH 40% OF THE SUPERCRITICAL MASS, AND AT THE OTHER END ANOTHER GROUP OF SLIGHTLY LARGER RINGS WITH 60% OF THE SUPERCRITICAL MASS, WHICH WAS FIRED ONTO THE SMALLER GROUP, WITH FOUR POLONIUM-BERYLLIUM NEUTRON INITIATORS TO MAKE THE SUPERCRITICAL MASS EXPLODE.>A HOLE IN THE CENTER OF THE LARGER PIECE DISPERSED THE MASS AND INCREASED THE SURFACE AREA, ALLOWING MORE FISSION NEUTRONS TO ESCAPE, THUS PREVENTING A PREMATURE CHAIN REACTION. BUT, FOR THIS LARGER, HOLLOW PIECE TO HAVE MINIMAL CONTACT WITH THE TUNGSTEN CARBIDE TAMPER, IT MUST BE THE PROJECTILE, SINCE ONLY THE PROJECTILE'S BACK END WAS IN CONTACT WITH THE TAMPER PRIOR TO DETONATION. THE REST OF THE TUNGSTEN CARBIDE TAMPER SURROUNDED THE SUB-CRITICAL MASS TARGET CYLINDER (CALLED THE "INSERT" BY THE DESIGNERS) WITH AIR SPACE BETWEEN IT AND THE INSERT. THIS ARRANGEMENT PACKS THE MAXIMUM AMOUNT OF FISSILE MATERIAL INTO A GUN-ASSEMBLY DESIGN.
>>64477201so... it was safer and more stable since the larger mass was outside of the reaction chamber?
>>64475808Did they? There's a lot of intentional obfuscation and misdirection around nukes, I've seen sources ALSO claim that gun-type nukes work with hollow targets and cylinder bullets.
>>64477302Popsci journalist tend to misinterpret descriptions. "Thin Man" used that design.All gun-type variants were developed: moving 'bullet', moving rings, and double gun.
>>64476751but I had breakfast yesterday, what do you mean?
>>64475808>Why did they make the sleeve the "bullet"they needed to accelerate the bullet as fast as possible to it would fit onto the target before the fission rate accelerated too much to cause a fizzle. Having the bullet the shape it is allowed them to blast the shit out of it and it would not tilt as it traveled down the barrel. The reason the plutonium bomb was an imploded sphere is because the high rate of fission - they could not shoot a plutonium bullet down the barrel fast enough to achieve full assembly because the acceleration of the fission rate was too high and the it would always fizzle.
>>64475831Yes you can launch a smaller hollow object faster onto the larger cylinder so that the whole assembly doesn't have enough time to fart itself loose when the two get close and criticality is approached
>>64477141The exception appears to be artillery delivered nuclear shells, a special case likely due to diameter requirements
>>64477201> WITH 60% OF THE SUPERCRITICAL MASSHold the fuck on. Unless you do some extra fuckery, all you can really do is 1.5-2x of supercritical mass "payload"? How the other designs achieve much higher yield while maintaining low supercritical mass of "parts" I guess?
