It seems reasonable, but "seems reasonable" isn't good enough. It also seems reasonable that we could see it in maps of the magnetic fields, but there are no guarantees. How is this related to confinement factors? Any other ideas? Anyone?I am not getting how this related to confinement factors. Is the confinement factor Gmj somehow related to sphericity? That seems to be his reason to expect improved performance.
Dodec Magnetic field?
Aero
Assuming that we are maxing out on SC magnets it should be a strictly volumetric relationship. 3X should give 70% the linear size (for the core).Aero wrote:The question of this thread now becomes, given 3-5x better confinement of the dodec, what is the reduction in radius of a break-even dodec compared to the radius of a break-even truncube?
5X about 60%. And that is just the core. The size of the DC collector is what it is. Every bit helps though.
And then there is the minimum size for the SC coils. Depending on field rqmts. SC wire is really a paradox. The higher the field the less current it can carry. So low field coils are small and high field coils are big. Relatively.
Engineering is the art of making what you want from what you can get at a profit.
Assuming it has to do with sphericity and all else remains consistant, the R for 5x improvment would be ~.8RCubOct while with 3x improvement, the R ~ .85RCubOct.Aero wrote:The question of this thread now becomes, given 3-5x better confinement of the dodec, what is the reduction in radius of a break-even dodec compared to the radius of a break-even truncube?
Assuming the cost scales ~ with R^3 and directly with complexity, the cost would be pretty much a wash; ~0.5 for size, 2 for complexity.
OK! That answers the fundamental question, (if the assumptions are valid).KitemanSA wrote:Assuming it has to do with sphericity and all else remains consistent, the R for 5x improvement would be ~.8RCubOct while with 3x improvement, the R ~ .85RCubOct.Aero wrote:The question of this thread now becomes, given 3-5x better confinement of the dodec, what is the reduction in radius of a break-even dodec compared to the radius of a break-even truncube?
Assuming the cost scales ~ with R^3 and directly with complexity, the cost would be pretty much a wash; ~0.5 for size, 2 for complexity.
Now, for one more assumption. Assume a 100 MW truncube BFR has a 2 meter radius. Does that mean a 100 MW dodec would have about 0.82 * 2 = 1.64 meter radius. Or does the R^5 power scaling factor in non-linearly?
If the BFR radius is like 1.6 meters, then the dodec coil radii are like 0.8 meters. That’s small, but still seems doable.
Maybe the dodec configuration is reserved for smaller ships, air and space craft, and for larger power generating plants, 500 MW, for example.
I calculate a coil radius of 1.1 meter for a 500 MW dodec?
Aero
Speaking of power density. With the WB 6 magnetic fields ~ 1000 G (0.1 Tesla), how much stronger could the magnetic field be in cooled copper coils, superconducters? What magnetic fields were used in WB 7? A strength of 1 T should give ~ 10,000 fold increase in fusion, a 10 T field would give 100,000,000 fold increase if the magnetic scaling laws hold. A ten fold increase in linier size (3 meters) would multiply the fusion by a thousand. Increasing the well depth could result in another 10-30 (in D-D fusion ?) fold increase.
If the generous estimations are acurate, then the thermal and radiation loads on the machine may be the limiting factors. In otherwords, a compromise of larger size with weaker magnets may be more managable. Given the history of fusion efforts, this would be remarkable! All of this , of course, is predicated on the darn thing working as advertised.
Dan Tibbets
If the generous estimations are acurate, then the thermal and radiation loads on the machine may be the limiting factors. In otherwords, a compromise of larger size with weaker magnets may be more managable. Given the history of fusion efforts, this would be remarkable! All of this , of course, is predicated on the darn thing working as advertised.
Dan Tibbets
To error is human... and I'm very human.
Yes, the confinement referred to is of electrons, which leads to more confinement of ions. It's about half an order of magnitude, so it reduces the size of a machine that can reach net power quite a bit.Ok. So given that the plasma is quasi neutral, does that also mean 3-5x more electron density? And how far to the left does that shift the break-even radius of the BFR.
Bussard is a little vague on that. It appears to have to do with well geometry at the edge.i am not getting how this related to confinement factors. Is the confinement factor Gmj somehow related to sphericity? That seems to be his reason to expect improved performance.
Keep in mind though, design performance improvements are critical right now because there are currently so many unknowns in terms of how losses will scale; it's a very, very long way from .001W to 100MW. It may turn out only a dodec can reach net power at a reasonable size.This will also
incorporate another feature found useful, that is to go to a
higher order polyhedron, in order to retain good Child-
Langmuir extraction by the machine itself (which is more
straightforward than relying on stand-alone e-guns for the
cusp-axis, very-high-B-field environment), while not giving
excessive electrostatic droop in the well edges.
Yes, M Simon did a calc on that a while back. This is bad news because it limits power to growing at r^2 (while costs rise at about r^3) once the limit of materials to stand the radiation is reached, probably around 100MW. Of course, in many ways too much power density is a nice problem to have.If the generous estimations are acurate, then the thermal and radiation loads on the machine may be the limiting factors.
Well yeah. But that is not the immediate problem. The immediate problem is finding out the rules. And for that a continuation along the cube lines is probably best. We don't even know if offsetting the coils will improve results. For experiments like that it is best for apples to apples comparisons for one and the minimum number of coils to minimize the effort in moving them around for another.KitemanSA wrote:Please note that we can't just scale the WB6 machine and reach 100MW. If my calcs were right, R^7 scaling on the WB6 > WB100 yields about one kW power. One NEEDS to go higher B, better sphericity, etc to get to 100MW. The question should be, how best to do it at the lowest cost.
Break even is good. Knowing the scaling laws is better. (for now)
Engineering is the art of making what you want from what you can get at a profit.
Let us look at the scaling. From .15 m radius to 2 m radius gives a volume multiplication of around 2,500.
An increase in the field from .1T to 10T gives 100,000,000 multiplication.
If you assume a 1 mW starting point that gets you to 100 MW. Roughly.
An increase in the field from .1T to 10T gives 100,000,000 multiplication.
If you assume a 1 mW starting point that gets you to 100 MW. Roughly.
Engineering is the art of making what you want from what you can get at a profit.
MSimon wrote:Let us look at the scaling. From .15 m radius to 2 m radius gives a volume multiplication of around 2,500.
An increase in the field from .1T to 10T gives 100,000,000 multiplication.
If you assume a 1 mW starting point that gets you to 100 MW. Roughly.
And, don't forget the increased reaction probability as drive energy (KeV) goes up. Looking at the the cross section charts, I'm estimating the cross section goes up ~ 30 fold from 10 KeV to 100 KeV for deuterum. If you are limited to deuterium- tritium reactions, the rate could be a couple of hundred fold above this. P-B11 might be similar to the D-D rate at appropiate voltages...
Dan Tibbets
To error is human... and I'm very human.
Provided that we are talking another scale model, and that we are talking cuboctohedron rather than truncube, I would agree. We should know which (cuboct or icosedodec) before starting in on the full scale unit. At least that was DrB's plan.MSimon wrote: The immediate problem is finding out the rules. And for that a continuation along the cube lines is probably best.
The thing is Art does not dispute the scaling laws - if the device works. The scaling laws are standard physics. What ART disputes is net power from Polywell.Aero wrote:So were done. The polywell model is linear and it predicts across a range of 11 orders of magnitude! Wonderful! Somebody tell Art! :lol:
Engineering is the art of making what you want from what you can get at a profit.
I agree that gross scaling = B^4 * R^3 and is solidly founded in physics, most do. WB-100 sized as quoted above targets break-even.
We hope that loss scales at R^2 or lower, but that is in dispute. Using R^2 losses gives B^4 * R, and your numbers, gives net power = 1 mW * 100,000,000 * (2/.15) = 1.3 MW That is to close to hang my hat on. Using a dodec configuration with the same parameters gives 3-5x 1.3 MW, = 4 MW - 6.7 MW. That is still not a very comfortable margin. there are a bunch of limitations in our knowledge of loss scaling, and then there is the potential of heat overload on the coils. (Not to mention that it is all based on 3 neutrons.)
I argued on another thread that we were not planning on a large enough machine, and I am still of that opinion. If we are not careful, we will have a "Jet" on our hands if we are so lucky. Then the net power BFR will be designed by committee, if the program survives.
We hope that loss scales at R^2 or lower, but that is in dispute. Using R^2 losses gives B^4 * R, and your numbers, gives net power = 1 mW * 100,000,000 * (2/.15) = 1.3 MW That is to close to hang my hat on. Using a dodec configuration with the same parameters gives 3-5x 1.3 MW, = 4 MW - 6.7 MW. That is still not a very comfortable margin. there are a bunch of limitations in our knowledge of loss scaling, and then there is the potential of heat overload on the coils. (Not to mention that it is all based on 3 neutrons.)
I argued on another thread that we were not planning on a large enough machine, and I am still of that opinion. If we are not careful, we will have a "Jet" on our hands if we are so lucky. Then the net power BFR will be designed by committee, if the program survives.
Aero