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Post by omnipotentvoid on Jun 30, 2017 9:52:13 GMT
I was having some fun with 10mg core mass nukes, getting prices down to less than a credit and mass to less than 50g (I'll post designs when I have time). So I decided to read up on how small implosion nukes can get. As far as I can tell, nuclear weapons need a minimum critical mass, so milligram scale nukes may not be possible. Can anyone confirm or deny?
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Post by dragonkid11 on Jun 30, 2017 11:36:30 GMT
...I fairly sure you have the change the limit just to get that low as my smallest nuke still has 10g of fissile.
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Post by omnipotentvoid on Jun 30, 2017 11:50:29 GMT
...I fairly sure you have the change the limit just to get that low as my smallest nuke still has 10g of fissile. I did change the limit in game, what I want to know is if there is a lower limit to mass capable of going supercritical in nukes in reality.
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Post by shiolle on Jun 30, 2017 11:54:30 GMT
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Post by Durandal on Jun 30, 2017 12:30:51 GMT
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Post by omnipotentvoid on Jun 30, 2017 14:13:44 GMT
So this rifle caliber nuke is actually possible?
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Post by Durandal on Jun 30, 2017 14:16:46 GMT
So this rifle caliber nuke is actually possible? Damn, beat me to it. Is Ca-252 availabe? If only I didn't have work today... How's that puppy handle btw?
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Post by Enderminion on Jun 30, 2017 14:47:38 GMT
Ca-252 is not in game, yet
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Post by ross128 on Jun 30, 2017 15:27:02 GMT
There generally is a minimum mass below which a nuke cannot (or I suppose more accurately, is extremely unlikely to) detonate, but this does vary based on what the fissile material is and what conditions it's under.
It's basically a race to release neutrons faster than they can escape, combined with a probability game of getting those neutrons to hit and split atoms. So for example, if you had a theoretical 100% efficient neutron reflector, you could shrink the critical mass significantly because neutrons would just build up endlessly until they reach the critical neutron flux, at which point it would go boom if there's enough unsplit fissiles left to do so.
If you had an extremely unstable isotope that was easily split by low-energy neutrons, and released tons of neutrons when it did split, that would also have a very low critical mass. It would also be highly radioactive, so your scientists would probably be a little reluctant to work with it and it would have a very short shelf life, which would cause logistical problems.
Of course, since safe handling and shelf life are not a concern in CoaDE we could probably use artificial superheavy elements whose half-lives are measured in miliseconds such as Oganesson (atomic number 118) or the hypothetical Ununennium (number 119). Though since these elements can only be made in particle accelerators and they decay almost instantly, I'm sure assembling even a few grams of those would be quite a tricky proposition. I'm sure a softer sci-fi setting could do funny things with stasis fields though.
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Post by omnipotentvoid on Jun 30, 2017 16:09:48 GMT
Damn, beat me to it. Is Ca-252 availabe? If only I didn't have work today... How's that puppy handle btw? I've only used it as a submunition for blaster based multi warhead missiles. They can be quite effective. May be of use as coil/railgun munitions as well.
EDIT: Heres a spray of mini nukes inside a gunship
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Post by vegemeister on Jun 30, 2017 23:41:32 GMT
My understanding is that IRL it's very difficult to get densification ratios better than 1/3 or so ( source, ctrl-f "achievable factors range", see also, ctrl-f "extreme compression"). Mass and volume-minimized bombs take advantage of low-pressure compression mechanisms like squashing subcritical geometries (hollow, oblong, etc.) into supercritical spheres and maybe that convenient plutonium phase transition. That minimizes the amount of explosive required and the size of the lens system, but gives poor efficiency and requires a lot of fissile material per warhead. Our ability to make ridiculously high compression ratio bombs is somewhat counteracted by the much greater critical masses (60 kg for Pu-239 in CoaDE, 10 kg IRL). It actually helps for high-yield bombs, since you can pack a lot more fissiles in before encountering criticality problems, but I've found the combat effectiveness of high-yield bombs to be very underwhelming. Several low-yield devices detonated together does more damage and is far cheaper. It also seems seems like the explosive is used as reaction mass for the bomb, so a 50 kt bomb does more damage than a 1.35 Mt bomb, at less than half the mass and way lower cost.
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Post by someusername6 on Jul 1, 2017 1:48:28 GMT
Damn, beat me to it. Is Ca-252 availabe? If only I didn't have work today... This motivated me to do some looking around for Cf-252. There are a couple issues modeling it: 1. I can't find data for neutron-induced fission energies. 2. I can find data for *spontaneous* fission, but I don't know how to model it into game. One study hilariously discard their data on measuring neutron-induced fission on Cf-251 because Cf-252 impurities cause too much background neutron radiation. Here's the information I collected for the element so far anyhow -- without the data on spontaneous fission. Element Californium-252 Symbol Cf-252 AtomicMass 252 AtomicNumber 98 MolarMass_g__mol 252 FirstIonizationEnergy_kJ__mol 608 HalfLife_s 83081592 MicroscopicThermalNeutronCaptureCrossSection_b 20.71 MicroscopicThermalNeutronScatteringCrossSection_b 11.1 MicroscopicThermalNeutronFissionCrossSection_b 33.03 MicroscopicFastNeutronCaptureCrossSection_b 1.489e-1 MicroscopicFastNeutronScatteringCrossSection_b 1.429e1 MicroscopicFastNeutronFissionCrossSection_b 1.075 MicroscopicResonanceIntegralCaptureCrossSection_b 44.62 MicroscopicResonanceIntegralScatteringCrossSection_b 2.238e2 MicroscopicResonanceIntegralFissionCrossSection_b 1.113e2 AverageNeutronsProducedPerThermalFission ??? AverageNeutronsProducedPerFastFission ??? FissionEnergy_MeV ??? MeanGammaRayMassAbsorptionCoefficient_cm2__g 8.703E-02 SolarAbundance 0 TransmutationParents Pu-239
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Post by dragonkid11 on Jul 1, 2017 3:28:03 GMT
So this rifle caliber nuke is actually possible? Fuck. Now I want to lower the limit.txt and shove these mini nuke into my cannons and EM guns because holy shit what 1 ton of TNT in less than 15 gram package.
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Post by omnipotentvoid on Jul 1, 2017 8:15:40 GMT
Here you go: a micro nuke with the explosive power of 9.5kg of tnt small enough to fit inside 5.56x45mm NATO bullets.
Edit: and heres a mock up of an m4 firing mininukes:
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Post by Durandal on Jul 2, 2017 0:46:47 GMT
So this rifle caliber nuke is actually possible? Fuck. Now I want to lower the limit.txt and shove these mini nuke into my cannons and EM guns because holy shit what 1 ton of TNT in less than 15 gram package. So...I hate to ask, but does anyone have a quick and dirty guide to modding the limit.txt on nuclear cores? I've been trying to avoid going down the mod rabbit hole but this is just too fun looking to pass up.
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