Is there any aspect of an Explosion resulting from a nuclear weapon test that cannot be simulated using super computers?

Question

This Washington Post news article states that with the advent of computer simulation of nuclear tests, live tests are no longer needed.

Generally speaking there are 3 aspects of an Explosion resulting from a nuclear weapon test that are tested:

(a) effectiveness, (b) yield, and (c) explosive capability.

Russia carried out its last nuclear test in 1990, UK in 1991,the US in 1992, France and China in 1996, India & Pakistan in 1998.

List Of Nuclear Weapon Tests

Therefore, does this mean that all aspects of a Nuclear Explosion can be simulated using Super computers or is there any aspect of a Nuclear Explosion that cannot be simulated by Super Computers?

Answer 1

The type of machine that runs the simulation (e.g. super computer, slide rule, pen and paper, etc.) is less important than the physical and mathematical models that describe the process being simulated. Throwing more computing resources at a simulation whose fundamental equations are flawed will not improve the accuracy of the solution.

To answer your question, there are very likely some aspects of a nuclear explosion that currently cannot be simulated (at least not accurately) with a super computer, or any computer for that matter. But, the reason is not the lack of computational power, it's a lack of complete understanding of the fundamental physics. Without periodic testing to verify and improve the models, we don't know how valid the simulation results are.

Answer 2

The accuracy of a simulation depends more on how well your equations and assumptions model reality, than the resolution of the simulation (computing power, as Carlton has stated). More computing power does let you have your solution in much less time however.

A model, by definition, is not the real thing. No model can be trusted unless it is tested in the real world. This is why we still have wind tunnels even though we extensively use computation fluid dynamics(CFD) for flow modeling. Its just numbers until you have validated the model. Once the model is validated you can extend it or extrapolate it to predict conditions that you can not test. For example testing a small bomb to predict the outcome of a large bomb.

In this case future prediction may very well be restricted to modeling only; leveraging past tests. Nuclear bomb testing today has a way of impeding world peace (oh, we arent building nuclear weapons, we are just testing them) ;-)

There have been lots of test in the past to validate the models they are likely using now. So for the United States at least, I wager their models are highly accurate, even including weather and GIS data.

I just skimmed the article, but they refer to the model as a "tool", not a replacement for testing. Dont let yourself reverse causation and correlation in your thinking. They dont only model with super computers because "there is no reason to test". They only model with super computers because there is no way any (sane) government will allow them to test.