[Maury Markowitz]

I hope it’s ok to reply to old threads here.

Stienhaus’s “concept” is pants. Come on, the guy can’t even figure out how to center one circle inside another in his presentation graphics, and we’re supposed to believe he has some idea how to build a working fusion machine?

Let’s start with the obvious issue that all he’s done is drawn a diagram of a two-stage thermonuke. A thermonuke works by capturing the x-ray output of the primary in a radiation channel, which then compresses a cylindrical secondary to fusion conditions. This relies on geometry; the collapse of the cylinder results in the pressure/density in the center being very high due to the shock wave converging.

Now let us consider Stienhaus’s diagram (posted above). In it, we have a D-T primary on the left, and a secondary on the right. Apparently, the primary is supposed to be ignited by a driver, and the energy of the resulting reaction is supposed to cause fusion in the secondary. Ok, so…

1) how are we going to cause the symmetrical collapse of the primary with the secondary in the way? We can’t get symmetrical collapse under perfect conditions in NIF, and in this design, one entire side of the primary is shadowed and cannot be “hit”. Good luck with that.

2) fusion burning in a D-T or D-D fuel occurs when the alphas deposit their energy back into the fuel. In order for this to occur you either need a very large volume, like ITER, or very high density, like NIF (NIF is 100x lead). You also need geometry on your side – the alphas are isotropic. The secondary in Stienhaus’s design is cylindrical meaning that the majority of the alphas will be lost from the fuel for purely geometric reasons. Its also only mechanically compressed, meaning the chance the alpha will be captured is very low even if it just happens to be going the right direction.

3) what exactly is the mechanism that starts fusion in the secondary? The diagrams say something about a “shock detonation wave”… is he actually claiming that a shock wave is going to do this end-on in a mechanically compressed fuel mass?! He also seems to be proposing this is the mechanism that causes the continued burn down the cylinder. Is he not aware that the alphas and neutrons are moving orders of magnitude faster than a detonation wave and will thus carry away all the energy before it can heat the adjacent fuel mass?

4) then there’s the problem that the diagram shows the primary “burning” at the size of the original sphere. After compression, it would be a sphere about the width of one of the lines around the secondary. That means it is separated from the secondary by a relatively large distance, about half the diameter of the secondary. Which means that whatever magical process he claims will start the fusion in the secondary is geometrically limited to the solid angle of the internal fuel plug, what, 10% of the energy released?

5) anyone even passingly familiar with ICF will know that the primary problem with achieving ignition is Rayleigh–Taylor instabilities. These are created when you have fluid movement in areas with different densities. In the case of NIF, that’s the difference between the pusher shell, the fusion fuel, and the empty space in the center and outside. In this design, the secondary consists of a cylinder with fuel in the center and some sort of shell on the outside, surrounded by nothing. Better yet, it’s long and skinny. This is the sort of design you make when you want to demonstrate R-T effects (and Richtmyer–Meshkov). The density difference also means that the shock wave will not travel linearly down the secondary, it will be refracted into or away from the shell depending on the relative densities (this is the basis for shaped charges). There is exactly zero chance that the fuel mass will remain stable.

6) and finally, think about this dynamically as the primary completes the fusion process (assuming it could, which it can’t). Under perfect theory this creates a spherically expanding mass of a bunch of different things – first you’d get some x-rays, then the relativistic neutrons, then alphas and other fusion products, and then a mix of ablator and other junk. Now zoom in on the end of the secondary when any one of these expanding shells reaches it… the first point to be hit is the center of the fuel, and then as the sphere continues to expand, a circular contact patch that expands across the end of the fuel. Do you see why that is? Ok, so basically *whatever* magical process is supposed to start the fusion in the secondary *isn’t symmetrical across the fuel* for *purely geometrical* reasons. Good luck with that too.

Basically, there is no way this will work. To borrow a phrase from the SDI era, this proposal is “one view-graph deep”.

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