Are they trying to model every single atom?
Is this a case where the physicists in charge get away with programming the most inefficient models possible and then the administration simply replies "oh I guess we'll need a bigger supercomputer"
The alternative is to literally build and detonate a bomb to get empirical data on given design, which might have problems with replicability (important when applying the results to rest of the stockpile) or how exact the data is.
And remember that there is more than one user of every supercomputer deployed at such labs, whether it be multiple "paying" jobs like research simulations, smaller jobs run to educate, test, and optimize before running full scale work, etc.
AFAIK for considerable amount of time, supercomputers run more than one job at a time, too.
Citation needed.
1 gram of Uranium 235 contains 2e21 atoms, which would take 15 minutes for this supercomputer to count.
"nuclear bomb simulations" do not need to simulate every atom.
I speculate that there will be some simulations at the subatomic scale, and they will be used to inform other simulations of larger quantities at lower resolutions.
https://www.wolframalpha.com/input?i=atoms+in+1+gram+of+uran...
I would like a citation for this.
> Hypersonics do however end up dealing with simulating subatomic particle behaviours
And this.
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For example, you could choose to cite "A Study on Plasma Formation on Hypersonic Vehicles using Computational Fluid Dynamics" DOI: 10.13009/EUCASS2023-492 Aerospace Europe Conference 2023 – 10ᵀᴴ EUCASS – 9ᵀᴴ CEAS
At sub-orbital altitudes, air can be modelled as a continuous flow governed by the Navier-Stokes equations for a multicomponent gas mixture. At hypersonic speeds, however, this physical model must account for various non-equilibrium phenomena, including vibrational and electronic energy relaxation, dissociation and ionization.
(younger generations are worse at it, because the problems that forced elder ones into more complex approaches can now be an overnight job on their laptop in ANSYS CFX)
So unfortunately my only source on that is bitching of post-docs and professors, with and without tenure (or rather its equivalent here), at premier such institutions in Poland.