Proposed focus on space propulsion research - why and how?

[Art Carlson]

When comparing the fuels you can make assumptions (not very reasonable ones, if you ask me) such that p-B11 and D-T have comparable reaction rates. For the present discussion it is sufficient to note that these assumptions make the fusion power density at a given pressure worse for D-T, rather than better for p-B11. D-T at the optimum temperature gives you a minimum value for the power density at a given pressure that cannot be topped by any fuel at any temperature.

[chrismb]

D-T at the optimum temperature gives you a minimum value for the power density at a given pressure that cannot be topped by any fuel at any temperature.

(don't you mean "maximum power density?")

applicable to two-body fusion...and mediated by the strong nuclear force...

..and excepting D+3He, maybe??...

[KitemanSA]

What do you think about retargeting polywell fusion research towards such objective? The article I linked above is just a concept introduction, obviously without scientific details. I am not sure where would be a good place to send it for publication, suggestions are appreciated!

As has been pointed out by others, the particular configuration would not work. However, there is a simple variation that might and that is an octagon rather than a cube. An octagon is actually the only pure Platonic solid that meets DrB's condition for an even number of magnetic faces at each vertex, no need to rectify like the others.

From a VERY brief perusal of your document, I get the impression that flow thru is an important feature (an "out" magnet opposite an "in" magnet). An octagon is also the only figure that comes to mind that has THAT feature while meeting DrB's condition.

Good luck.

[ankovacs]

The most obvious is that your coils won't make a polywell.

As has been pointed out by others, the particular configuration would not work.

I attach here the drawing of the grid with, current flows shown. The incoming current on thick input is 3 times the incoming current on thinner inputs. Actually, best way to imagine an input line is that each is composed of 6 wires, tracing out 3 edges each on the way to opposite vertex. When you run the numbers, you find same net current on each edge, and magnetic field in the center going to zero:


One problem with this arrangement is that there will be along each edge one / two wires carrying opposite current than the other three / four wires, so the resulting magnetic repulsion will be difficult to contain mechanically.
KitemanSA: can you please explain why there needs to be even number of magnetic faces at each vertex, if not rectified?
I guess you meant octahedron grid. I will think about an octahedron-based design.

Back to the rounded cube, the magnetic field simulation gives this picture of field lines along the axes:

To me these seem to curve the proper way along each axis for polywell formation. What am I missing? Here is the picture of field lines that originate near the center:

The plasma pressure gets transmitted to the grid through the magnetic fields, which means a flimsy "wireframe" isn't going to hold together.

Here my estimation for this aspect. If the wire has tensile strength 1 Gpa, the arc segment can withstand around 6 Gpa radial pressure. In terms of outward - inward pressures we have:
electric repulsion - magnetic attraction between grid edges (because of parallel currents) + plasma pressure.

Since the first two terms counterbalance, let's say the plasma pressure induced component can go up to 2 GPa. For the order of magnitude estimation, if we take the grid radius as 10 meters, having 1 cm2 cross section. The exposed grid area is around 2 m2. Perhaps it's not unreasonable to polywell surface area to be 4m2. So the possible plasma pressure is then in the 1 GPa range, with larger polywell sphere it is less. Is it too small plasma pressure to be in the 0.1 GPa - 1 GPa range?

[ankovacs]

Here my estimation for this aspect. If the wire has tensile strength 1 Gpa, the arc segment can withstand around 6 Gpa radial pressure. ... Is it too small plasma pressure to be in the 0.1 GPa - 1 GPa range?

Sorry, I forgot to divide by 100 for the radial dimension of the 1cm2 wire. So the estimation is then 1 MPa - 10 MPa feasible plasma pressure. Is that enough?

[KitemanSA]

Looks like a 3D funny cusp to me. Your cube is faced with non-magnetic regions. Not sure what that might be good for. Doesn't make much sense to me but maybe it will for someone else.

[ankovacs]

The setup is such that straight edges just show the simulation area. My rounded cubical grid is aligned such that two of its edges go across x axis, and two go across z axis. So the picture you see along x and z is edge-to-edge. The y axis goes through the middle of top/bottom faces.
This perhaps is not obvious in the picture, I could not make the wireframe also appear in non-disturbing way.