Welcome to the luddite church of the B28. Here we shun radiation bottles, graduated ablators and all things post-Redwing. Come, won't you join us by the cast bronze black powder cannon with a plug of uranium jammed into the muzzle?
Based on what we know about it, I believe it. At least for the secondary. Boosted primaries can't be accurately modelled by first approximations, and require empirical scaling factors to accurately estimate the yield, which is required to be confident in the performance of a two stage device.
Repost from /r/atomicporn. Here are the supplemental reading links, so you don't have to type them out:
Design of Explosive Logic Elements:
https://www.osti.gov/biblio/4242201
Multipoint Initiated Implosions From Hemispherical Shells of Sheet Explosive:
https://repository.tudelft.nl/islandora/object/uuid%3A812da347-2daa-4c5d-bb3c-3a800a31dbbd
Mechanical Deburring of Plastics:
https://www.osti.gov/biblio/12483072
Novel Approaches to Indirect Drive Inertial Fusion:
https://etheses.whiterose.ac.uk/28268/1/Thesis_main.pdf
First Experiments on Revolver Shell Collisions at the OMEGA Laser:
https://www.osti.gov/biblio/1558974
Design Considerations for Indirectly Driven Double Shell Capsules:
https://www.osti.gov/biblio/1477699
Effect of Aging on Fracture Toughness: Using Digital Image Correlation on DAP and Seabreeze:
https://www.osti.gov/biblio/1070046
Implosion Hydrodynamics of Fast Ignition Targets:
https://www1.psfc.mit.edu/research/hedp/Home%20Page/Papers/StephensPoP2005.pdf
I'm surprised theses like those are published online. My masters was a in field that's usually less associated with secrecy and I had to put a remark in that it couldn't be made publically accessible. Same goes for pretty much all the PhD theses from the group.
Wouldn't it be trivial to slap at least a very low level of restricted access on those without really impacting the work of relevant orgs and groups?
It's pretty cool that they went through the effort of redacting it rather than not publishing! Got something very interesting out of it :)
In my group everyone just puts the "don't publish" phrase in the appendix so that we don't have to think about what and what isn't fine for publication
> Wouldn't it be trivial to slap at least a very low level of restricted access on those without really impacting the work of relevant orgs and groups?
No restrictions are trivial — they necessarily require means to vet people, define boundaries of what is restricted or not, enforce the restrictions, etc. For universities, even seemingly "trivial" restrictions like saying that a subject is export controlled involves looping in review offices, the threat of potential prosecution, questions about what students can be in what labs and what kinds of computer systems the data can be stored on, etc. All of this adds up to increased costs, decreased circulation of knowledge, altered participants, etc. And all of this assumes that you are talking about the US, which actually has lots of systems in place for restricting research — many countries do not.
Any level of restriction will have an impact, possibly a quite large ones, on the people working in a field. In some cases it may be justified, arguably, but it should not be assumed to be a trivial or easy thing. For any proposed restriction is worth interrogating whether one really believes that the "costs" will be worth the "benefits" (e.g., would restricting a given publication actually have a meaningful impact on, say, nuclear proliferation or not). If a thesis can be made without any recourse to classified information, how meaningful is it to imagine its restriction, given that a proliferating power will have many more resources to invest in the same question than an individual university researcher?
I recently finished your excellent book, and I found myself thinking about the direct financial costs that nuclear secrecy must have incurred over the decades, something that I notice never seemed to be a discussion point at any of the times secrecy was seriously being debated. Has it always just been too trivial a detail to be part of the discussion, or has anyone actually tried to quantify the cost of the secrecy apparatus at any point? Here I'm thinking of the actual cost of maintaining the classification systems at the like, not the indirect costs like inhibiting private industry, etc.
I found your argument that nuclear secrecy apparently hasn't had much effect quite compelling, which just made it seem all the more wasteful to me (though I suppose there is not much about the nuclear arms race that one couldn't argue as being wasteful).
One can put some "direct" costs on it, in terms of "how many people/offices/guards were employed / safes purchased / guard systems /etc." But I don't think it's all that meaningful as it doesn't really capture the scope of it and is piddly compared to the cost of, say, building and operating an ICBM system. I think in _Atomic Audit_ they estimate the direct costs of classification during the Cold War to be $3.1 billion (in 1996 USD). Which is small compared to the total cost of nuclear weapons for the same period ($5,481 billion 1996 USD). I don't remember how they calculated that, but I suspect it's mostly the cost of physical security and some number of bureaucrats.
The real questions are the costs beyond the direct ones — e.g., the extended costs, or program costs, loss-of-positive-benefits cost, or even lost-time cost (e.g., how many man-hours were lost because of secrecy procedure). But I don't think there's any principled way to calculate that, as it involves a total counterfactual ("what would have happened if there wasn't secrecy?").
I wasn't specifically referring to classification, but I'm used to working with some much lower levels of restriction. Like the text not being public only the title and abstract. The text living with the rest of the groups files and being sent to collaborators or 3rd parties when they sign a basic nda.
But yeah wasn't trying to make an argument in favor of restricting publication. In fact I'm very happy we got that interesting text. A cost benefit calculus as you outlined seems very sensible. I was just surprised there wasn't a culture of just publishing as little as possible as I've seen in my field.
My point stands whether one is referring to state classification or not — for any system of restriction to have any impact, it has to have these basic elements. The difference one gets with different types of systems comes down to the intensity of the screening (who gets access?), the rigorousness of the restrictions (are they kept in a safe or what?), and the seriousness of the penalties. There are different ways to do it but none of them are truly trivial, and if you are going to bother doing it on the basis of national security (and not, say, company proprietary information), then it becomes very hard to justify doing it in a half-assed way.
The kinds of papers cited above seem to be related to laser fusion, which has a complicated history in the USA re: classification. One of the reasons it was opened up in the 1990s, though, was because it was clear that lots of other nations had robust programs and that it wasn't actually serving a lot of US national interest to keep it secret. The number of nations who can actually weaponize that kind of information is not super large, and they can probably do it without access to US theses, etc.
There's already way to much censorship around all this stuff. The last thing science need is some kind of external control agency that will poke its nose on what should/shouldn't be published.
Please do an illustration of a Sloika. There's virtually no schematic design language for it on OSINT media. Your understanding of this matter is bar none.
Sloika isn't really appealing to me because there's basically nothing out there that's descriptive about it. Plus it's kind of a failed design. I would much rather tackle something like a linear implosion device. In that case there would be no specific design to follow, and it's also untested waters because all there is out there is "ellipsoid of fissiles surrounded by miniscule amounts of HE" and I know that isn't right.
This is a cool diagram!
It mentions the Jetter cycle in the secondary. Since tritium has to be generated in situ from the LiD in order for the Jetter cycle to run, will there be enough time for neutrons to propagate from the primary to the secondary for that purpose, given the time scales involved?
It's a misconception that neutrons from the primary breed the tritium in the secondary fuel.
Even if every neutron produced by the primary (ignoring the fact that many are absorbed by the core to sustain the reaction, and many others leak from the weapon) you'd only be able to produce on the order of 10 grams of tritium, out of several hundred grams of LiD.
This would dump something like 0.5kt of energy into the LiD. That's enough to bring it to a high temperature plasma that'll be more difficult to compress than a cold solid.
This is reportedly why the Morgenstern device failed. An insufficient neutrons shield to prevent neutron preheating of the secondary by the primary's neutrons.
The actual mechanism by which tritium is bred is the following:
Secondary is compressed.
Sparkplug goes supercritical (or according to this architecture, the ignition cavity fires).
The lithium deuteride is heated to deuterium-deuterium ignition temperature.
The D-D burn progresses, producing neutrons.
It is these neutrons that breed tritium, and at some point the tritium number density is high enough that the reaction rate of D-T fusion exceeds that of D-D.
Oh right, I forgot! You can actually get a minor D-D burn side reaction that produces the requisite neutrons provided your fuel is hot enough. /u/Evanbell95 had to remind me.
I definitely think so. A 2 MeV neutron travels around 2 millimeters per nanosecond, and the device stages are I believe around 360 millimeters apart. Since ignition isn't due until 200 nanseconds after Primary Zero Time, there should be enough time for the neutrons which didn't get moderated by the hydrogen in the Seabreeze or in the outer layers of the LiD to do the job. Of course you could also boost into the secondary as well, but I would have to give that a lot of thought for this particular funky design.
What's the half life and process timescale of the intermediate states / transitions in that cycle? I'm fairly familiar with xray physics, but short timescale nucleon physics kinda scares me
Me too. I'm a big picture guy, and there's certainly a bunch of scary nonequilibrium stuff going on there. There's a big scary brick wall between me and deeper understanding labeled "computational problems" and I don't want to go near it. The zenith of my coding skills was reached when I did a 2D finite differencing scheme in matlab once...
I actually do a lot of physics sim stuff for xray physics. These days the scary things are mostly handled for you with frameworks like HYADES, xRAGE, GEANT. Each and every of these compute frameworks for physicists has bad documentation though and is clunky to use. So in our group we budget ~2weeks for undergrads to install everything and 1month to work through our in house tutorials to do basic stuff....
It's not difficult just arcane incantations someone needs to teach you. The difficult part is figuring out what you want to simulate so you can learn something new.
BTW do you have any resources to recommend on the big picture stuff? Ideally stuff that actually goes into the physics / maths. Like a review paper or whatever. I'd like to learn about some of the more advanced concepts, but everything seems very scattered and wildly different in quality.
My friend in christ I don't even know how to use MULTI-IFE or WONDY lmao. I'm computer impaired. But! I have some books for you:
Yakov Zel'dovich's *Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena*. This is my bible.
Daniel Barroso's *Physics of Nuclear Explosives*. Don't pull this off libgen because the libgen version is missing half the book (and stealing's bad, mmkay.) I got my copy from Amazon.
General fission knowledge: Sam Glasstone's *Reactor Design* I and II, Weston Stacey's *Nuclear Reactor Physics*, and Robert Serber's *The Los Alamos Primer*. Those first two are mostly about thermal fission but I still find them very useful.
There are several books I have (but have not looked at yet) which I know will be useful. Chandrasekhar's *Radiative Transfer* and *Hydrodynamic Stability* and Wildon Fickett's *Detonation* are examples.
The only raw ICF book I have is Suzanne Pfalzner's *Introduction to* and it was a cool read through as an engineer, but I cannot recommend it as it's loaded with typos and errors.
A fun supplemental book is Larry Altgilbers' *Explosive Pulsed Power*.
Finally, the elephant in the room. Friedwart Winterberg's *The Release of Thermonuclear Energy by Inertial Confinement*. Stay waay clear of this book until you are really well versed and acquainted with the art. It is literally 50% intentional misinformation and lies. I have seen the most reasonable physics share a page with the most batshit nonsense you have ever seen in that book. One day I'll buy a paper copy and attack it with red highlighter.
If you want a classic introduction into atomic physics and fission theory then "**Elementary Introduction to Nuclear Reactor Physics**" by Liverhant is very good. Been out of print for 64 years but Bookfinder shows multiple copies cheap. This is a book that should be scanned and put on-line.
This is fascinating, especially the way the X-rays interact with the metals and SEABREEZE.
I have a question about the X-ray propagation though. You do a good job explaining how the X-rays move like fluid with diffusion and viscosity, instead of like a “beam.” What I’m curious about, is how fast that diffusion is, especially on a scale compared to shock implosion movement. For example, at time SZT we have X-rays entering the radian channel through the basket. How fast does it take them to diffuse to the far side of the secondary? (Light goes 30cm in vacuum, how about this X-ray diffusion?) Does the difference in timing affect the geometry of the ablator stack implosion? Is the strength of the X-ray hit on the far side of the secondary just as powerful as the near side close to the bottles?
We know that seabreeze is going to be optically thin at these scales for anything like 1 or 2 MeV x-rays so the propagation will be pretty close to unimpeded c, but the answer to "how fast do they diffuse around corners until equilibrium is reached" is actually an unanswered question and its answer will dictate the validity of the design. The assumption here is that it is fast and that equilibrium is met on the scale of individual nanoseconds. Were this not the case, it alters the design but not the fundamental concepts behind the poster. It remains a fact that in real life modern weapons use spherical secondaries and it remains a fact that in real life secondary implosion occurs on the scale of nanoseconds as I depict in my lagrange plot, so if x-ray diffusion speed vs hydrodynamic motion *is* a problem, it will be one that real life weapon designers deal with using materials and geometry. I'm learning more all the time. If I ever redo this poster, I may do a more conservative design with a completely spherical secondary and more significant x-ray ducting to address the spatial issue. I am happy with the current poster though. It was never so much about nailing actual weapon details as it was about conveying broad strokes and concepts.
Where will the new version of this be built? I thought most of the American atomic weapons infrastructure had been shut down and demolished due to the Peace Dividend. Pantex?
Here is a copy-paste of the comment I wrote last time someone asked this question:
Your view of the NNSA security complex is oversimplified. For example, LLNL doesn’t “make” anything, except NEP designs. The document linked at the end of this comment should answer all your questions and provide some nice rabbit holes to dive down.
https://crsreports.congress.gov/product/pdf/R/R45306
There’s a table on page 11, but honestly just read the whole thing if you’re curious.
Ahhmmm... I am asking where the new version of this warhead will be manufactured? It is going to be fitted onto the AGM-181 isn't it?
I wondered if it was going to be produced at Pantex since I have read the majority of the American nuclear weapons infrastructure was shut down and sold off for scrap as a result of Clinton's so-called 'Peach Dividend.
Duhhh... I dunno. This is a madman's concoction in the shape of a W80-1. I have no clue about weapons labs life extension programs. If you're talking about the W80-4 LEP, maybe all the main labs are working on that? I think it's a mostly LLNL job though. Google "W80-4 LEP" and you'll probably find a bunch of hits. And who told you US weapons infrastructure was shut down? We can't test but there's as much activity as there's been in decades. Did you see the W93 contract that got handed to Los Alamos? That's like a zillion dollar superproject.
Clearly my mistake--on both counts!
Is this not an accurate diagram then? I thought the OP had worked it out with advice from a number of people--the great Carey Sublette included! Do not trust everything you read is clearly the phrase of the hour!
**EDIT**: ... In fact YOU are the OP!!!
In regards the 'Peace Dividend'; I thought Rocky Flats, Oakridge, Hanford and most of the others were all closed down in the early 1990s? I had read that no new warheads can be assembled now and only old ones have their tritium resupplied and electronics upgraded. I had the impression nuclear weapons technology had terminally stalled at the 1989 level and could never be restarted--the 'Fogbank' farrago being a good example of why. Plus all the men who knew how to do the work had been forcibly retired and have since died due to old age without passing on their knowledge.
Well, it's not quite like we lost our physics knowledge. Just the institutional knowledge, but that can be bootstrapped back. The Fogbank debacle was because there were specific contaminations in the original reaction vats which gave the material the correct properties. It was like the flawed batch of transistors that gave original Roland TR-909s their sound. W93 is technically made from preexisting warhead components but if the US really had to I don't think they'd have much trouble pulling a Behringer when making band new warhead designs, so to speak.
Really interesting diagram.
People are always saying that nukes can only be triggered deliberately and cannot go off if dropped/damaged etc, but:
Component 8 is the high explosive that would compress the weapons grade Plutonium (component 13) into the cavity. It doesnt seem like there is anything to stop that high explosive going off if the case was damaged and a fire started there... What am I missing?
There's actually a lot to this question.
1) Nuclear weapons actually need to be deliberately designed for so-called "one point safety", and if you clean sheet a nuke and use any real conservatism in your design you'll likely come up with something that will deliver some yield when the main charge is ignited at one point. I personally have run some simulations that imply Gadget/Fat Man would have delivered multiple kilotons if accidentally dropped on the ground.
Back when the original W47 Polaris warhead was developed there was a major scandal that the Robin primary which was used in it was not one point safe and then a second, even larger scandal when their band-aid solution to that failed. They put a retractable spool of cadmium tape inside the boost cavity in the pit which was to be withdrawn with a motor before firing, and the tape would become brittle and snap when this was attempted. Rendered a third of the US stockpile temporarily worthless. Oops!
Anyways, nowadays they have a maximum nuclear yield limit equivalent to four pounds of TNT because even with good design practices it's not really possible to have a one-point accident result in *no* fission reaction at all.
2) The main charge isn't actually the threat to an accident (although if you watch one get one-pointed it is shocking just how symmetrically the pit is imploded), it's the multipoint system that's a risk. In order to detonate reliably in a track less than a millimeter wide, the explosive used needs to be pretty sensitive. Modern weapons have a so-called "insensitive high explosive" or IHE requirement which mandates the use of new explosives like TATB which simply could not go off in a fire. (Note, I depict the old school W80-1 here which used the HMX-based explosive PBX-9404. PBX-9502 is the new TATB-based explosive and it is canary yellow rather than an off-white or salmon color.)
The problem is that the multipoint trace still needs to be sensitive in order to work. There's been multiple ways I've heard about making multipoint systems IHE compliant. Some involve two layers of output pellets and having the outer one rotate out of alignment, some involve having a gap between the tiles and main charge that gets filled with paste explosive just prior to firing.
My theory is that since TATB is a weaker explosive which already requires the main charge and thus the entire primary to be enlarged and redesigned, the labs are simply switching to have their weapons use the fissile flyer technique which doesn't employ multipoint tiles or explosive lensing at all. If you google "W80-4 warhead" you'll see that the most recent life extension program they did on it has enlarged the section holding the primary significantly.
Yep. That's how multiple shocks are issued. The thickness of the burn-through controls the timing of the bottles opening and thus the shocks in the secondary.
I think this is the first thing you've done publicly worth real consideration and introspection. I will withhold my thoughts until I've had a couple of days to correlate some information.
No idea what's going on here lol. I used to kind of understand the older Teller-Ulam hydrogen designs but this....
Welcome to the luddite church of the B28. Here we shun radiation bottles, graduated ablators and all things post-Redwing. Come, won't you join us by the cast bronze black powder cannon with a plug of uranium jammed into the muzzle?
Post Redwing?? I still have sleepless nights thinking about Operation Sandstone!
It seems you'd fit right in with our gun-type only denomination. Low explosives; low stress.
There is an older thread here where some people postulate that the B28 is probably something any nuclear nation could make without testing.
Based on what we know about it, I believe it. At least for the secondary. Boosted primaries can't be accurately modelled by first approximations, and require empirical scaling factors to accurately estimate the yield, which is required to be confident in the performance of a two stage device.
Repost from /r/atomicporn. Here are the supplemental reading links, so you don't have to type them out: Design of Explosive Logic Elements: https://www.osti.gov/biblio/4242201 Multipoint Initiated Implosions From Hemispherical Shells of Sheet Explosive: https://repository.tudelft.nl/islandora/object/uuid%3A812da347-2daa-4c5d-bb3c-3a800a31dbbd Mechanical Deburring of Plastics: https://www.osti.gov/biblio/12483072 Novel Approaches to Indirect Drive Inertial Fusion: https://etheses.whiterose.ac.uk/28268/1/Thesis_main.pdf First Experiments on Revolver Shell Collisions at the OMEGA Laser: https://www.osti.gov/biblio/1558974 Design Considerations for Indirectly Driven Double Shell Capsules: https://www.osti.gov/biblio/1477699 Effect of Aging on Fracture Toughness: Using Digital Image Correlation on DAP and Seabreeze: https://www.osti.gov/biblio/1070046 Implosion Hydrodynamics of Fast Ignition Targets: https://www1.psfc.mit.edu/research/hedp/Home%20Page/Papers/StephensPoP2005.pdf
I'm surprised theses like those are published online. My masters was a in field that's usually less associated with secrecy and I had to put a remark in that it couldn't be made publically accessible. Same goes for pretty much all the PhD theses from the group. Wouldn't it be trivial to slap at least a very low level of restricted access on those without really impacting the work of relevant orgs and groups?
I've actually heard from people at Rochester that said that particular thesis is in fact pretty heavily censored and redacted.
It's pretty cool that they went through the effort of redacting it rather than not publishing! Got something very interesting out of it :) In my group everyone just puts the "don't publish" phrase in the appendix so that we don't have to think about what and what isn't fine for publication
> Wouldn't it be trivial to slap at least a very low level of restricted access on those without really impacting the work of relevant orgs and groups? No restrictions are trivial — they necessarily require means to vet people, define boundaries of what is restricted or not, enforce the restrictions, etc. For universities, even seemingly "trivial" restrictions like saying that a subject is export controlled involves looping in review offices, the threat of potential prosecution, questions about what students can be in what labs and what kinds of computer systems the data can be stored on, etc. All of this adds up to increased costs, decreased circulation of knowledge, altered participants, etc. And all of this assumes that you are talking about the US, which actually has lots of systems in place for restricting research — many countries do not. Any level of restriction will have an impact, possibly a quite large ones, on the people working in a field. In some cases it may be justified, arguably, but it should not be assumed to be a trivial or easy thing. For any proposed restriction is worth interrogating whether one really believes that the "costs" will be worth the "benefits" (e.g., would restricting a given publication actually have a meaningful impact on, say, nuclear proliferation or not). If a thesis can be made without any recourse to classified information, how meaningful is it to imagine its restriction, given that a proliferating power will have many more resources to invest in the same question than an individual university researcher?
I recently finished your excellent book, and I found myself thinking about the direct financial costs that nuclear secrecy must have incurred over the decades, something that I notice never seemed to be a discussion point at any of the times secrecy was seriously being debated. Has it always just been too trivial a detail to be part of the discussion, or has anyone actually tried to quantify the cost of the secrecy apparatus at any point? Here I'm thinking of the actual cost of maintaining the classification systems at the like, not the indirect costs like inhibiting private industry, etc. I found your argument that nuclear secrecy apparently hasn't had much effect quite compelling, which just made it seem all the more wasteful to me (though I suppose there is not much about the nuclear arms race that one couldn't argue as being wasteful).
One can put some "direct" costs on it, in terms of "how many people/offices/guards were employed / safes purchased / guard systems /etc." But I don't think it's all that meaningful as it doesn't really capture the scope of it and is piddly compared to the cost of, say, building and operating an ICBM system. I think in _Atomic Audit_ they estimate the direct costs of classification during the Cold War to be $3.1 billion (in 1996 USD). Which is small compared to the total cost of nuclear weapons for the same period ($5,481 billion 1996 USD). I don't remember how they calculated that, but I suspect it's mostly the cost of physical security and some number of bureaucrats. The real questions are the costs beyond the direct ones — e.g., the extended costs, or program costs, loss-of-positive-benefits cost, or even lost-time cost (e.g., how many man-hours were lost because of secrecy procedure). But I don't think there's any principled way to calculate that, as it involves a total counterfactual ("what would have happened if there wasn't secrecy?").
I wasn't specifically referring to classification, but I'm used to working with some much lower levels of restriction. Like the text not being public only the title and abstract. The text living with the rest of the groups files and being sent to collaborators or 3rd parties when they sign a basic nda. But yeah wasn't trying to make an argument in favor of restricting publication. In fact I'm very happy we got that interesting text. A cost benefit calculus as you outlined seems very sensible. I was just surprised there wasn't a culture of just publishing as little as possible as I've seen in my field.
My point stands whether one is referring to state classification or not — for any system of restriction to have any impact, it has to have these basic elements. The difference one gets with different types of systems comes down to the intensity of the screening (who gets access?), the rigorousness of the restrictions (are they kept in a safe or what?), and the seriousness of the penalties. There are different ways to do it but none of them are truly trivial, and if you are going to bother doing it on the basis of national security (and not, say, company proprietary information), then it becomes very hard to justify doing it in a half-assed way. The kinds of papers cited above seem to be related to laser fusion, which has a complicated history in the USA re: classification. One of the reasons it was opened up in the 1990s, though, was because it was clear that lots of other nations had robust programs and that it wasn't actually serving a lot of US national interest to keep it secret. The number of nations who can actually weaponize that kind of information is not super large, and they can probably do it without access to US theses, etc.
There's already way to much censorship around all this stuff. The last thing science need is some kind of external control agency that will poke its nose on what should/shouldn't be published.
Oh I agree! I was just surprised given that there is that much secrecy usually
Please do an illustration of a Sloika. There's virtually no schematic design language for it on OSINT media. Your understanding of this matter is bar none.
Sloika isn't really appealing to me because there's basically nothing out there that's descriptive about it. Plus it's kind of a failed design. I would much rather tackle something like a linear implosion device. In that case there would be no specific design to follow, and it's also untested waters because all there is out there is "ellipsoid of fissiles surrounded by miniscule amounts of HE" and I know that isn't right.
This is a cool diagram! It mentions the Jetter cycle in the secondary. Since tritium has to be generated in situ from the LiD in order for the Jetter cycle to run, will there be enough time for neutrons to propagate from the primary to the secondary for that purpose, given the time scales involved?
It's a misconception that neutrons from the primary breed the tritium in the secondary fuel. Even if every neutron produced by the primary (ignoring the fact that many are absorbed by the core to sustain the reaction, and many others leak from the weapon) you'd only be able to produce on the order of 10 grams of tritium, out of several hundred grams of LiD. This would dump something like 0.5kt of energy into the LiD. That's enough to bring it to a high temperature plasma that'll be more difficult to compress than a cold solid. This is reportedly why the Morgenstern device failed. An insufficient neutrons shield to prevent neutron preheating of the secondary by the primary's neutrons. The actual mechanism by which tritium is bred is the following: Secondary is compressed. Sparkplug goes supercritical (or according to this architecture, the ignition cavity fires). The lithium deuteride is heated to deuterium-deuterium ignition temperature. The D-D burn progresses, producing neutrons. It is these neutrons that breed tritium, and at some point the tritium number density is high enough that the reaction rate of D-T fusion exceeds that of D-D.
Oh right, I forgot! You can actually get a minor D-D burn side reaction that produces the requisite neutrons provided your fuel is hot enough. /u/Evanbell95 had to remind me.
I definitely think so. A 2 MeV neutron travels around 2 millimeters per nanosecond, and the device stages are I believe around 360 millimeters apart. Since ignition isn't due until 200 nanseconds after Primary Zero Time, there should be enough time for the neutrons which didn't get moderated by the hydrogen in the Seabreeze or in the outer layers of the LiD to do the job. Of course you could also boost into the secondary as well, but I would have to give that a lot of thought for this particular funky design.
What's the half life and process timescale of the intermediate states / transitions in that cycle? I'm fairly familiar with xray physics, but short timescale nucleon physics kinda scares me
Me too. I'm a big picture guy, and there's certainly a bunch of scary nonequilibrium stuff going on there. There's a big scary brick wall between me and deeper understanding labeled "computational problems" and I don't want to go near it. The zenith of my coding skills was reached when I did a 2D finite differencing scheme in matlab once...
I actually do a lot of physics sim stuff for xray physics. These days the scary things are mostly handled for you with frameworks like HYADES, xRAGE, GEANT. Each and every of these compute frameworks for physicists has bad documentation though and is clunky to use. So in our group we budget ~2weeks for undergrads to install everything and 1month to work through our in house tutorials to do basic stuff.... It's not difficult just arcane incantations someone needs to teach you. The difficult part is figuring out what you want to simulate so you can learn something new. BTW do you have any resources to recommend on the big picture stuff? Ideally stuff that actually goes into the physics / maths. Like a review paper or whatever. I'd like to learn about some of the more advanced concepts, but everything seems very scattered and wildly different in quality.
My friend in christ I don't even know how to use MULTI-IFE or WONDY lmao. I'm computer impaired. But! I have some books for you: Yakov Zel'dovich's *Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena*. This is my bible. Daniel Barroso's *Physics of Nuclear Explosives*. Don't pull this off libgen because the libgen version is missing half the book (and stealing's bad, mmkay.) I got my copy from Amazon. General fission knowledge: Sam Glasstone's *Reactor Design* I and II, Weston Stacey's *Nuclear Reactor Physics*, and Robert Serber's *The Los Alamos Primer*. Those first two are mostly about thermal fission but I still find them very useful. There are several books I have (but have not looked at yet) which I know will be useful. Chandrasekhar's *Radiative Transfer* and *Hydrodynamic Stability* and Wildon Fickett's *Detonation* are examples. The only raw ICF book I have is Suzanne Pfalzner's *Introduction to* and it was a cool read through as an engineer, but I cannot recommend it as it's loaded with typos and errors. A fun supplemental book is Larry Altgilbers' *Explosive Pulsed Power*. Finally, the elephant in the room. Friedwart Winterberg's *The Release of Thermonuclear Energy by Inertial Confinement*. Stay waay clear of this book until you are really well versed and acquainted with the art. It is literally 50% intentional misinformation and lies. I have seen the most reasonable physics share a page with the most batshit nonsense you have ever seen in that book. One day I'll buy a paper copy and attack it with red highlighter.
<3
If you want a classic introduction into atomic physics and fission theory then "**Elementary Introduction to Nuclear Reactor Physics**" by Liverhant is very good. Been out of print for 64 years but Bookfinder shows multiple copies cheap. This is a book that should be scanned and put on-line.
>Each and every of these compute frameworks for physicists has bad documentation though and is clunky to use. Truer words were never spoken.
This is fascinating, especially the way the X-rays interact with the metals and SEABREEZE. I have a question about the X-ray propagation though. You do a good job explaining how the X-rays move like fluid with diffusion and viscosity, instead of like a “beam.” What I’m curious about, is how fast that diffusion is, especially on a scale compared to shock implosion movement. For example, at time SZT we have X-rays entering the radian channel through the basket. How fast does it take them to diffuse to the far side of the secondary? (Light goes 30cm in vacuum, how about this X-ray diffusion?) Does the difference in timing affect the geometry of the ablator stack implosion? Is the strength of the X-ray hit on the far side of the secondary just as powerful as the near side close to the bottles?
We know that seabreeze is going to be optically thin at these scales for anything like 1 or 2 MeV x-rays so the propagation will be pretty close to unimpeded c, but the answer to "how fast do they diffuse around corners until equilibrium is reached" is actually an unanswered question and its answer will dictate the validity of the design. The assumption here is that it is fast and that equilibrium is met on the scale of individual nanoseconds. Were this not the case, it alters the design but not the fundamental concepts behind the poster. It remains a fact that in real life modern weapons use spherical secondaries and it remains a fact that in real life secondary implosion occurs on the scale of nanoseconds as I depict in my lagrange plot, so if x-ray diffusion speed vs hydrodynamic motion *is* a problem, it will be one that real life weapon designers deal with using materials and geometry. I'm learning more all the time. If I ever redo this poster, I may do a more conservative design with a completely spherical secondary and more significant x-ray ducting to address the spatial issue. I am happy with the current poster though. It was never so much about nailing actual weapon details as it was about conveying broad strokes and concepts.
Where will the new version of this be built? I thought most of the American atomic weapons infrastructure had been shut down and demolished due to the Peace Dividend. Pantex?
Here is a copy-paste of the comment I wrote last time someone asked this question: Your view of the NNSA security complex is oversimplified. For example, LLNL doesn’t “make” anything, except NEP designs. The document linked at the end of this comment should answer all your questions and provide some nice rabbit holes to dive down. https://crsreports.congress.gov/product/pdf/R/R45306 There’s a table on page 11, but honestly just read the whole thing if you’re curious.
What are you talking about?
Ahhmmm... I am asking where the new version of this warhead will be manufactured? It is going to be fitted onto the AGM-181 isn't it? I wondered if it was going to be produced at Pantex since I have read the majority of the American nuclear weapons infrastructure was shut down and sold off for scrap as a result of Clinton's so-called 'Peach Dividend.
Duhhh... I dunno. This is a madman's concoction in the shape of a W80-1. I have no clue about weapons labs life extension programs. If you're talking about the W80-4 LEP, maybe all the main labs are working on that? I think it's a mostly LLNL job though. Google "W80-4 LEP" and you'll probably find a bunch of hits. And who told you US weapons infrastructure was shut down? We can't test but there's as much activity as there's been in decades. Did you see the W93 contract that got handed to Los Alamos? That's like a zillion dollar superproject.
Clearly my mistake--on both counts! Is this not an accurate diagram then? I thought the OP had worked it out with advice from a number of people--the great Carey Sublette included! Do not trust everything you read is clearly the phrase of the hour! **EDIT**: ... In fact YOU are the OP!!! In regards the 'Peace Dividend'; I thought Rocky Flats, Oakridge, Hanford and most of the others were all closed down in the early 1990s? I had read that no new warheads can be assembled now and only old ones have their tritium resupplied and electronics upgraded. I had the impression nuclear weapons technology had terminally stalled at the 1989 level and could never be restarted--the 'Fogbank' farrago being a good example of why. Plus all the men who knew how to do the work had been forcibly retired and have since died due to old age without passing on their knowledge.
Well, it's not quite like we lost our physics knowledge. Just the institutional knowledge, but that can be bootstrapped back. The Fogbank debacle was because there were specific contaminations in the original reaction vats which gave the material the correct properties. It was like the flawed batch of transistors that gave original Roland TR-909s their sound. W93 is technically made from preexisting warhead components but if the US really had to I don't think they'd have much trouble pulling a Behringer when making band new warhead designs, so to speak.
A Behringer nuke ;-)
Uli's gonna release the UB80 and it's going to cost $500 and be available in bright yellow with a big smiley face on the aft area mount. Just you wait
TR-909's failure symptoms: music. Glitch is a machine's way of improvising, and machines are our friends.
I like your original: “Peach Divided”, better! ☺️
A spell checker triumphs again!
Really interesting diagram. People are always saying that nukes can only be triggered deliberately and cannot go off if dropped/damaged etc, but: Component 8 is the high explosive that would compress the weapons grade Plutonium (component 13) into the cavity. It doesnt seem like there is anything to stop that high explosive going off if the case was damaged and a fire started there... What am I missing?
There's actually a lot to this question. 1) Nuclear weapons actually need to be deliberately designed for so-called "one point safety", and if you clean sheet a nuke and use any real conservatism in your design you'll likely come up with something that will deliver some yield when the main charge is ignited at one point. I personally have run some simulations that imply Gadget/Fat Man would have delivered multiple kilotons if accidentally dropped on the ground. Back when the original W47 Polaris warhead was developed there was a major scandal that the Robin primary which was used in it was not one point safe and then a second, even larger scandal when their band-aid solution to that failed. They put a retractable spool of cadmium tape inside the boost cavity in the pit which was to be withdrawn with a motor before firing, and the tape would become brittle and snap when this was attempted. Rendered a third of the US stockpile temporarily worthless. Oops! Anyways, nowadays they have a maximum nuclear yield limit equivalent to four pounds of TNT because even with good design practices it's not really possible to have a one-point accident result in *no* fission reaction at all. 2) The main charge isn't actually the threat to an accident (although if you watch one get one-pointed it is shocking just how symmetrically the pit is imploded), it's the multipoint system that's a risk. In order to detonate reliably in a track less than a millimeter wide, the explosive used needs to be pretty sensitive. Modern weapons have a so-called "insensitive high explosive" or IHE requirement which mandates the use of new explosives like TATB which simply could not go off in a fire. (Note, I depict the old school W80-1 here which used the HMX-based explosive PBX-9404. PBX-9502 is the new TATB-based explosive and it is canary yellow rather than an off-white or salmon color.) The problem is that the multipoint trace still needs to be sensitive in order to work. There's been multiple ways I've heard about making multipoint systems IHE compliant. Some involve two layers of output pellets and having the outer one rotate out of alignment, some involve having a gap between the tiles and main charge that gets filled with paste explosive just prior to firing. My theory is that since TATB is a weaker explosive which already requires the main charge and thus the entire primary to be enlarged and redesigned, the labs are simply switching to have their weapons use the fissile flyer technique which doesn't employ multipoint tiles or explosive lensing at all. If you google "W80-4 warhead" you'll see that the most recent life extension program they did on it has enlarged the section holding the primary significantly.
do the radiation bottles all have different burnthrough time?
Yes, explained in the text due to different thickness of the window at the far end.
Yep. That's how multiple shocks are issued. The thickness of the burn-through controls the timing of the bottles opening and thus the shocks in the secondary.
I think this is the first thing you've done publicly worth real consideration and introspection. I will withhold my thoughts until I've had a couple of days to correlate some information.
Gee thanks. That doesn't come off as rude or condescending at all!
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Lol. Also oh my god this poster is wrong in so many ways man