tombo wrote:I can't imagine how you could avoid cutting B lines.
Some of the induced currents are what you want because they smooth out the lumps. (???) But too much would be problematical.
Why prolate? Why not keep it spherical?
Is that to bring it back to spherical from the oblate-ness caused by the centrifugal force? (tidal bulge) (Is this even an effect in plasmas? The mass is so low and the fields are so high.)
It might not have to spin. It could oscillate rotationally along with the pops.
Sort of a shimmying dance.
I could see making it rotate by phasing the POPS drive to the various grids.
You might want to look up the Phasotron Tube (sp?) for a look at how something like that might be done. Do a search here or over at NASA SF. It has been discussed.
Simon
Hi Simon
Just re-read your post.
I too am interested in combined/hybrid approaches and effects.
i am also quite interested in the Betatron configuratyion and it properties - here http://en.wikipedia.org/wiki/Betatron - not unlike the Polywell in some ways.
angular momentum vs electro-magnetic - by-the-by, i was also trying to work out a way of harnessing the 'spinning skater' effect to to translate further acceleration.
There is also the question of whether the inner and outer of the Wiffleball/plasma field, should be spinning in opposite directions or the same direction or just different directions (eg 90 degrees at variance). What effects might we expect to see in such modes - most particularly on ion density vs velocity?
A general comment: the reactors Dolan describes will have thin boundary sheaths due to the anode intersection of the field lines at the cusps. The presence of those anodes acts as a nice boundary condition on the plasma that makes it easy to understand the sheath behavior, I think. With polywell, I'm not sure what acts to bound the sheath, so I've no idea how thick or what shape it might be. I suspect that the magnetic and electric potential gradients will be more gradual than for tightly limited systems.
I think we may have carried the qualitative arguements about this machine as far as they can go. I think that's why it's gotten so quite here in the theory forum.
Actually there was a vacuum tube called the Phasotron. It was used for FM modulation and depended on phased fields to the grid structure. I worked on a transmitter that had one (or it was described in a transmitter manual as one way to make FM).
A quick Google search turned up nothing and my memory is hazy.
It was fairly specialized and I'd be surprised if more than 10,000 ever got made.
Engineering is the art of making what you want from what you can get at a profit.
A general comment: the reactors Dolan describes will have thin boundary sheaths due to the anode intersection of the field lines at the cusps. The presence of those anodes acts as a nice boundary condition on the plasma that makes it easy to understand the sheath behavior, I think. With polywell, I'm not sure what acts to bound the sheath, so I've no idea how thick or what shape it might be. I suspect that the magnetic and electric potential gradients will be more gradual than for tightly limited systems.
I think we may have carried the qualitative arguements about this machine as far as they can go. I think that's why it's gotten so quite here in the theory forum.
Solo: certainly is.
Dolan seems to estimate around 10mm boundary thickness for his well trap - with B=1.3T and Electron Larmor radius=3.8E-4m at the boundary/sheath - if I'm reading it right.
In the BFR I'm visualizing that the boundary sheath is produced by magnetic reflection of the Wiffleball.
How do you mean 'tightly limited systems'?
By you last point, I'm supposing you refer to this unbearable wait for experimental results? Or are you just fed up with hypothetical conjectures?
By sheath, I mean the area where the electron and ion density drop off toward nothing, but the electron density is slightly greater, causing the space charge that produces the potential well.
By tightly limited, I mean that there is an anode which intercepts the flux lines around the cusp throat. With the polywell, Dr. Bussard wanted to minimize the flux intercepted by the magrid (equivalent to Dolan's 'anode' merged with the field coils) so that fewer electrons would be lost (by diffusion across the field and then transport along the field to the magrid/anode). This means, in effect, that electrons could diffuse across the magnetic field into 'orbits' very close to the grid coils, which means that the sheath may also come very close to the grid. Or, it may mean that the sheath is thicker, with a more gradual change in densities of ions/electrons.
With the machines Dolan describes, the anode presence at the cusp tells us what flux surface is the farthest out the sheath can go. With the polywell, we don't know. That makes it hard to say what the plasma will do.
I was refering to both the waiting and the fact that we seem not to be making much progress in understanding during the wait. But, I think we all (naively) expected to hear the results about this time, and so we didn't feel like conjecturing. Discussion (or WAG-ing) may pick up again now that we seem to have concluded it might be a while before we hear anything of substance.
MSimon wrote:Actually there was a vacuum tube called the Phasotron. It was used for FM modulation and depended on phased fields to the grid structure. I worked on a transmitter that had one (or it was described in a transmitter manual as one way to make FM).
A quick Google search turned up nothing and my memory is hazy.
It was fairly specialized and I'd be surprised if more than 10,000 ever got made.
ah, perhaps a frequency modulated Polywell in a phase-locked-loop?
or are you imagining a 1GW FM Transmitter?
very interesting design certainly - electron disks, slotted masks and magnetic transduction - l like the hybrid ani-digital approach, i can imagine implementing pipe-lined CPU register arithmetic on such devices.
i recall clearing my father attic years ago, and having to dispose of some fascinating looking vacuum tubes, mostly from Radar, TV transmission etc. Some of them real works of art and ingenuity. We donated them to a local technical college. Goodness knows what they made of them.
Mike Holmes wrote:
Another geometry that occurs to me is to simply use two tetrahedrons made of rings. Each has four sides, and four vertices. The outer is aranged so it's rings are over the inner tetrahedron's vertices.
i think this is a most interesting conjecture. did anyone follow it up?
apparently it is cited by Bussard as 'conformal' with the WB regime. and a lot simpler to both analyse and build i think.
as it is, i believe such an analysis might easily provide optimal phase diagrams for our coil current drivers.
Mike Holmes wrote: Another geometry that occurs to me is to simply use two tetrahedrons made of rings. Each has four sides, and four vertices. The outer is aranged so it's rings are over the inner tetrahedron's vertices.
i think this is a most interesting conjecture. did anyone follow it up?
apparently it is cited by Bussard as 'conformal' with the WB regime. and a lot simpler to both analyse and build i think.
as it is, i believe such an analysis might easily provide optimal phase diagrams for our coil current drivers.
what do you think?
A rectified tetrahedron is an octahdron, and octahedra have been discussed ad-nauseum.
Mike Holmes wrote: Another geometry that occurs to me is to simply use two tetrahedrons made of rings. Each has four sides, and four vertices. The outer is aranged so it's rings are over the inner tetrahedron's vertices.
i think this is a most interesting conjecture. did anyone follow it up?
apparently it is cited by Bussard as 'conformal' with the WB regime. and a lot simpler to both analyse and build i think.
as it is, i believe such an analysis might easily provide optimal phase diagrams for our coil current drivers.
what do you think?
A rectified tetrahedron is an octahdron, and octahedra have been discussed ad-nauseum.
That will depend on who you ask. I would be interested in trying some of the Octahedral options, especially some of tombo's variations on a theme. If you do a search on author=tombo and search for posts (not topics), then look on about page 17 of the results, you will find a fascinating set of octahedral designs that are much like Dr. Bussard's MPG designs.
One of them is like a fractle extension of the simple octahedral MPG. But it has metal in the path of the funny cusps. I think that properly done, the design could be modified to produce a good open vertex (holey X cusp) varient of his design that might be just about perfect.
MSimon on the other hand seems to think that nothing need be done other than the toroid faced quasi cuboctahedron that was WB6 and 7.
That will depend on who you ask. I would be interested in trying some of the Octahedral options, especially some of tombo's variations on a theme. If you do a search on author=tombo and search for posts (not topics), then look on about page 17 of the results, you will find a fascinating set of octahedral designs that are much like Dr. Bussard's MPG designs.
One of them is like a fractle extension of the simple octahedral MPG. But it has metal in the path of the funny cusps. I think that properly done, the design could be modified to produce a good open vertex (holey X cusp) varient of his design that might be just about perfect.
MSimon on the other hand seems to think that nothing need be done other than the toroid faced quasi cuboctahedron that was WB6 and 7.
Not exactly my viewpoint. I believe that a machine with stronger magnets will negate the advantages of other geometries in terms of cost. i.e. my position is based on economics rather than science. Which of course fits with my engineering background.
Engineering is the art of making what you want from what you can get at a profit.
Not exactly my viewpoint. I believe that a machine with stronger magnets will negate the advantages of other geometries in terms of cost. i.e. my position is based on economics rather than science. Which of course fits with my engineering background.
I agree with MSimon, though my reasoning is not all the same. Economics is important, but not necessarily first. I come from the engineering school of, "If it ain't broken, don't fix it!" And since follow on contracts more or less prove that it ain't broken, it seems smart to avoid the cost, uncertainty and plain old risk of "Fixing" it at this stage.
After the BFR is proven to work at any level, in any configuration, money will become available to fit it onto smaller and smaller platforms, driving efficiencies higher and higher to achieve the smaller footprint needed. Of course the technological advances made to achieve these higher efficiencies will be designed into the then currently new model BFRs for all applications.
Aero wrote: I come from the engineering school of, "If it ain't broken, don't fix it!"
Whereas my school taught that if the guy that designed and built it thought it might be broken and that fixes should be investigated, I figure it may be wise to investigate. Three engineers, three schools. Interesting.
Aero wrote: I come from the engineering school of, "If it ain't broken, don't fix it!"
Whereas my school taught that if the guy that designed and built it thought it might be broken and that fixes should be investigated, I figure it may be wise to investigate. Three engineers, three schools. Interesting.
Well sure. Once it is proven work on improvements. Once it is working it will also be easier to determine if improvements are worth the effort.
Engineering is the art of making what you want from what you can get at a profit.