Is There an Optimal Size for Magrid Casings?

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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KitemanSA
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Postby KitemanSA » Sun Mar 15, 2009 3:17 pm

MSimon wrote: You ought to get to know Murphy. Because Murphy definitely wants to know you.
Do you mean Dr. Murphy who observed after a massive experiment where they got no data because some technician installed the accelerometers upside-down that "In any situation where there are two or more possible ways to do something, someone will inevidably do it in the way that produces the most harm or least good"? Or do you mean that application of Finagins second law "the perversion of the universe tends toward the maximum" to Murphy wherein folks say "if it can go wrong it will"?
Last edited by KitemanSA on Sun Mar 15, 2009 9:32 pm, edited 1 time in total.

KitemanSA
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Postby KitemanSA » Sun Mar 15, 2009 4:15 pm

Billy Catringer wrote:
KitemanSA wrote:Conversely to your last statement, I am concerned that you are trying to react loads inefficiently. It is bad enough that the gravity loads on the SC core need to be carried past the thermal barriers to ground. But it seems that you want to carry the magnetic ones too. This seems unwise if there is an alternative, and there is.
Okay, what do you propose as an alternative? So far, you have not explained what you see as an alternative means of dealing with all the loads. Mind you, we are talking about some pretty big loads, even if we go back to magnets 2 meters in diameter. I am ready, Kiteman. I am all eyes, waiting willing to read what you have in mind.
When I started to reply to this yesterday, I was about to just tell you to read what I had already posted. But then Tom Boydston "tombo" did that really nice graphic that I used in my reply to him a few posts back. So I will use it again by reference here. Now I am going to plead with you to read this with a desire to understand, not a desire to find fault. Please.
Take the first picture of the two that tombo did above, the one that shows the interconnected piping. Now, in your mind, bow it to a spherical shape. I ask you to imagine that inside those pipes are a system not unlike yours, multi-layers of insulating and heat removing stuff. At the core is a core pretty much just like yours, EXCEPT that it is laid up over a sphere and because all the coils are interconnected it can have a continuous piece of metal within the core that can take a good deal of membrane loads. (I also prefer a rounder x-section to MSimon's square one, but I can see some benefits either way). The magnet coils are attached to and supported to that continuous backbone of high strength steel. it is also encased in a pipe of high strength steel.
All the magnetic loads resolve to radial outward loads, and they are supported by the equivilent of hoop stresses in that backbone and pipe. NONE of the magnetic stresses need be reacted outside the core container. The core container need only be supported against gravitational loads by the outside members. A now very light weight TPS (thermal protection system) can be connected to a similar design of neutron protection system and only supported against gravity loads. Said loads will be quite within the reach of thin section typical metals.

Billy Catringer wrote:
KitemanSA wrote:I dont understand how this answers the question. To a first order, the heat that must be extracted by the second (the LN, LO, LNLO, whichever) course of HEX is a function of how much radiates to it from the outside. That amount can be GREATLY reduced by multiple standoff layers of foil.
I am going to assume that what you mean with the extemporaneous use of the acronym "HEX" is heat exchange. As it happens, I agree with you that layers of foil could cast a useful shade. Now, how do you propose to one, suspend these layers of foil, and two, cool these layers of foil?
1) Staggered buttons of aerogel or the like. 2) Why in the world would you think I want to cool them? The foil will naturally take on the temperature ~1/2 way between the two radient surfaces on either side. In doing so, it cuts energy transmission MARKEDLY. I think it is a 4th power rule.

Billy Catringer wrote:
KitemanSA wrote:Finally, look up truss core. This is a very light weight, pyramidal truss core panel that makes an excellent and extremely light weight heat exchanger. It is also reasonable easy to manufacture in tubular shapes using metal glass brazing.
Billy Catringer wrote:I have already advised MSimon that we should consult with All-Clad about having them make the outermost jacket.
That is good, but I was talking about it for the LN and first water courses. I believe it would result in a MUCH thinner, lighter structure
Just nesting one piece of pipe inside the other is not what I am doing. As I explained before, every jacket must have a set of shoes inside. Those shoes transfer the mechanical loads imposed by the magnets to the rest of the structure. The Cool Water Jacket will be the jacket that transfers all of those loads to the supports holding the entire thing up. Honeycomb or pyramidal truss core materials might work for the inner jackets, but they will be thicker than the solid 316 I am proposing to use in the cryogenic layers. Sandwich materials will not work at all for the Cool Water Jacket. We need it to absorb heat very quickly AND be the strongest part of our structure.

The outer jacket, the Hot Water jacket, will be dealing only with the water pressure induced by heating. That pressure will be quite high and we will have to put a lot of water through that jacket. Using the materials All-Clad uses to make skillets might, MAYBE, let us get a way with a much thinner jacket than the one I have drawn. Right now, it is 1.9cm of copper and I am not at all sure that 1.9cm of copper would endure under these temperatures and pressures.

Now, there are two problems with this thick outer jacket. The obvious one is the surprising amount of weight it adds to the structure. The other one though, has to do with same problem your foils have. The surface of it will start turning to vapor before the water can cool it. Honeycomb materials for this jacket would fail almost as quickly as fusion began.
Which, if you reacted the magnetic loads out as I have suggested, this thick pipe and shoes and all that complexity becomes needless. PLEASE, react the loads out efficiently.

I was going to wait to bring this up, but I also think we should rethink the outer water course and use some other material like eutectic NaK or other liguid metal. True we would need some rplacement for the H in the water to moderate the neutrons, but... This is still up for discussion as I am not wed to anything on this now.

Billy Catringer wrote:
KitemanSA wrote:I suspect you might be able to get the heat control system much smaller than it is now. For one thing, you are working with evacuated systems in a vacuum chamber. Not a lot of external, buckling type, pressure loads.
Yes, there is. We have six 10Tesla solenoids that will be compressing the fields together in a rather small space for such intensities. Can you show me what the magnitude of the resultants will be? Have you done the math? I've been digging and have yet to get an answer that I think is reliable.
The magnet does not induce loads on the stainless or the copper or the water or the..., at least not to any significant degree. If your react the MAGNET's magnetic loads out as I have described, the TPS becomes a light add on, probably supported independantly by the outermost course, not touching the inner most course at all. This would actually allow more slop in construction tolerances.

Billy Catringer wrote:
KitemanSA wrote:I think that the magnet's magnetic loads should be reacted out within the inner-most course and be done with.
Really? How?
See above. If you still don't get it, I will take the time to draft up more crude graphics.

Billy Catringer wrote:
KitemanSA wrote:Then, the structural loads should be reacted out directly to ground with a high strength, low conductivity material (perhaps SiC?).
Silicone carbide holds up wonderfully well to high temperatures and abrasion. That is why we use it for the teeth, mind you, just the teeth of saw blades. It is brittle. It will not do for a material used in structural members unless those members are stacked up like bricks so that they never see anything but compression loads that are spread out evenly.
Then please explain why the strongest high temperature fiber known to man is beta SiC? Gee this tensile structure I have described may have to be made with woven fiber, perhaps potted in other ceramic, perhaps just properly wound around the piping providing the LHe. Mayhaps the pipe carrying the LHe would be strong enough to carry the loads and the SiC would just be an insulator.

Billy Catringer wrote:
KitemanSA wrote:The thermal protection and neutron conversion/protection system should be made as light and thin as possible and reacted out thru one of the layers of that system.

Okay, again, explain to me how you propose to do this? Simply asserting that we should do thus and so is not good enough. You have to give me some idea of how you think that this can be done.
IBID.

Billy Catringer
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Postby Billy Catringer » Sun Mar 15, 2009 5:28 pm

tombo wrote:I need an approximate model that is simple enough for me to solve.
To calculate (estimate) the forces on the bottom coil (Antarctica) I chose to substitute 2 concentric coils (tropic of cancer and tropic of capricorn) for the 4 coils on edge by reconnecting the corners at the equator (in my imagination) then including the top (arctic circle) as a third coil. The diameter is the one that will give the same area as the square coil. The spacing is some kind of average between the min and max of the actual coil.

BUT I stumbled over a problem: The load is not evenly distributed along the beam (of the coil supported by the legs).
The distance between the coil and the adjacent coil at the corner is 0.5 meter or less and in the middle it is 2 meters. Since the effect varies as 1/R the force varies by a factor of 8 or so.
This means that THE LEGS CANNOT BE ANYWHERE EXCEPT VERY CLOSE TO THE CORNERS for structural stress reasons. (I apologize for shouting but this is an important point.)


You are saying the same thing Ed Kribbs said. Hollow tubes with shoes in them will not work. The loads must be distributed over the entire tube. I"m on it.

Billy Catringer
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Postby Billy Catringer » Sun Mar 15, 2009 6:49 pm

KitemanSA wrote:When I started to reply to this yesterday, I was about to just tell you to read what I had already posted. But then Tom Boydston "tombo" did that really nice graphic that I used in my reply to him a few posts back. So I will use it again by reference here. Now I am going to plead with you to read this with a desire to understand, not a desire to find fault. Please.

Yes, yes I have read all of that. I really am trying to understand what you are on about. So far, though, I haven't been able to picture what you want to do.
KitemanSA wrote:Take the first picture of the two that tombo did above, the one that shows the interconnected piping. Now, in your mind, bow it to a spherical shape. I ask you to imagine that inside those pipes are a system not unlike yours, multi-layers of insulating and heat removing stuff.

Okay, so far, so good. This much I can understand. I keep telling you that it is damnably difficult to do, but you do not seem to want to hear that. Believe me when I tell you that this will result in skyrocketing costs and lengthy delays.
KitemanSA wrote:At the core is a core pretty much just like yours, EXCEPT that it is laid up over a sphere and because all the coils are interconnected it can have a continuous piece of metal within the core that can take a good deal of membrane loads.

I am not at all sure what you mean by "membrane loads". You are not describing a monocoque structure. Let's say we use a good grade of stainless steel cable to try holding the coil together in this configuration. It would be in the center of the winding. The strands of the coil would simply slide past the cable because of the magnetic field, resulting in a rapidly expanding cloud of coruscating spaghetti.

Having beat up on you, I think you might have the germ of a good idea here. A tubular net cradling the core might, I emphasize "might", work. The strands of the net would have to be made from flat strips. Mind you, this would lack the rigidity necessary to keep the coils from flapping around like flag. It would not free us from the need for a surrounding jacket to supply that rigidity AND to circulate coolant/moderator. You have to remember that the core will not be in anyway flexible. Think of it as being made of glass.
KitemanSA wrote:(I also prefer a rounder x-section to MSimon's square one, but I can see some benefits either way). The magnet coils are attached to and supported to that continuous backbone of high strength steel. it is also encased in a pipe of high strength steel.

I have been laboring under the assumption that we cannot use ferromagnetic materials. That is why I...would you please get a Yahoo mail account under an assumed name? Then I could e-mail you some numbers. It isn't that hard to set up and I am not going to hunt you down or blow your cover. Maraging steel might do the job, but I was unable to find out if it is ferromagnetic or not.

KitemanSA wrote:All the magnetic loads resolve to radial outward loads, and they are supported by the equivalent of hoop stresses in that backbone and pipe.


Okay, NOW I can see what you meant by "hoop stress". I'm a petrochem guy. When you say "hoop stress" to me, I think you mean the stresses resulting from pressure in a pipe or a vessel.

KitemanSA wrote:NONE of the magnetic stresses need be reacted outside the core container. The core container need only be supported against gravitational loads by the outside members.

I don't agree with this because my experience with magnets suggests that bad things will happen. Perhaps if we were in freefall things would be different, but this thing will not be built in freefall anytime soon. If the magnetic fields were perfectly aligned and were never perturbed by anything, your idea might hold water. We ain't that lucky. The problem becomes even more troublesome when you start thinking about putting one of these things into a moving vehicle.

KitemanSA wrote:A now very light weight TPS (thermal protection system) can be connected to a similar design of neutron protection system and only supported against gravity loads. Said loads will be quite within the reach of thin section typical metals.


Don't I just wish. I'll need a lot more detail before I buy into this one. The coolants are fluids that have to be pumped through the system fast enough that these light metals will not see too much pressure and rupture. Just as importantly, the coolants will have to pumped through the system fast enough to avoid having the heat reach the SC core. Out of that comes a lot of vibration. Vibration will cause the SC cores to move around which will in turn perturb the magnetic fields, which would, sooner or later, result in cracks in the SC coil and we have our rapidly expanding cloud of coruscating spaghetti.

KitemanSA wrote:1) Staggered buttons of aerogel or the like. 2) Why in the world would you think I want to cool them? The foil will naturally take on the temperature ~1/2 way between the two radient surfaces on either side. In doing so, it cuts energy transmission MARKEDLY. I think it is a 4th power rule.


And after the outermost layer of foil evaporates? The innermost layers will not protect the outermost one.

KitemanSA wrote:I was going to wait to bring this up, but I also think we should rethink the outer water course and use some other material like eutectic NaK or other liguid metal. True we would need some replacement for the H in the water to moderate the neutrons, but... This is still up for discussion as I am not wed to anything on this now.

What is the ratio of potassium to sodium in this solution you are championing? Have you calculated what it will weigh? Have you thought about the vibration that pumping it around in your lightweight structure will cause? You do realize that molten alkali metals are one of the major drawbacks to the ITER design, right? Mineral oil would be a safer and far less troublesome replacement for water, but both of the real-live Nuke-E's we have on this board have both rejected mineral oil as well.
KitemanSA wrote:The magnet does not induce loads on the stainless or the copper or the water or the..., at least not to any significant degree. If your react the MAGNET's magnetic loads out as I have described, the TPS becomes a light add on, probably supported independantly by the outermost course, not touching the inner most course at all. This would actually allow more slop in construction tolerances.

If, IF, we could do what you describe, maybe. What you want to do is to cancel the loads from the magnetic fields by using internal tension members. Bucky Fuller would be proud of you. Convince me that perturbations will not suddenly eat us alive in such a system. I don't think there are any metals that can be used for that kind of load at LHe temperatures. Do you have one in mind? Carbon fiber might do the job, I don't know, but then you will have to show me that there is a combination of supplier/shop that can figure out how to build within a year and at less than astronomical costs.
KitemanSA wrote:I think that the magnet's magnetic loads should be reacted out within the inner-most course and be done with. See above. If you still don't get it, I will take the time to draft up more crude graphics.

If you want me to model it, you gotta send me a sketch and wait while I finish sorting out how to use this program. You would likely get faster results from Tombo because he is obviously a talented draftsman and is already in full command of his software.

At any rate, I would very much like to see a picture of what you have in mind. And, I must add, the finished drawings should be done to scale. We need to be doing more than brochure grade stuff at this point.
KitemanSA wrote:Then please explain why the strongest high temperature fiber known to man is beta SiC? Gee this tensile structure I have described may have to be made with woven fiber, perhaps potted in other ceramic, perhaps just properly wound around the piping providing the LHe. Mayhaps the pipe carrying the LHe would be strong enough to carry the loads and the SiC would just be an insulator.

Okay, you are talking about FIBROUS, not solid SiC. That is a very different beast. I assume you intend to use this material for your structural cables. I won't argue with you about that, but I do suggest that you check to be certain of its behavior at temperatures in the low Kelvins. While you are about it, you need to be thinking about who we would buy this stuff from and who we could contract to fabricate it.

I read about these wizzy-bangy materials all the time, but I damned seldom read of anyone who is actually using them for anything very large if anything at all. You might want to think about tungsten core boron fiber while you are at it. Also, remember that nearly all of these fiber composite materials rely on epoxies to hold them together.
KitemanSA wrote:The thermal protection and neutron conversion/protection system should be made as light and thin as possible and reacted out thru one of the layers of that system.

Again, you are not being clear about what you mean. Could and should I already know about. What I need to know from you is HOW. I am not trying to be an egotistical prig here. Investors and the experts they hire will be demanding to know the same things.

tombo
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Postby tombo » Sun Mar 15, 2009 9:33 pm

Yes, stainless steel is probably a 2nd choice but it has its issues.

The bowed coil segments are MUCH harder for me to draw.

Vertex count: the square planform truncube has 12 vertexes. When you add the cross connects it essentially adds 8 triangular coils (at the cube vertexes) and it converts each of those 8 four sided vertexes into 4 three sided vertexes. It essentially adds 12 more (square-ish) faces to the polygon which are located at the funny cusps which are at the middles of the original edges.

To make them square-ish I had to fiddle with the bend radii. The first time it was so tall and skinny that the opposite bends overlapped with each other closing the hole off altogether. I can make them any aspect ratio you want. As one pair of sides move in the other 2 need to move out there is no way around that.

Full command of my software hah! It took me 10+ hours just to add those jumpers and get everything to line up correctly. Now it would have been faster if I had been less picky about alignment and about trying to keep the link to my structural spreadsheet intact. I’m still in learning mode on this one but it thinks a lot more like me than blender does.

The recently posted link to SC properties says that SC fibers are usually bonded together and to their supports using epoxies to hold them together and used in 4K helium. So I think we can include epoxy as a possible material.

Speaking of whizbang materials even a good grade Stainless like 316 is tough to work with, especially in large complicated weldments and with leak tightness, and it is not all that strong compared to the really good grades of steel, and it warps if you cycle the heat too much, like every time you do a weld. The whole thing will have to be annealed in a jig to hold it in alignment. The size is not a problem. “Cooper Heat” will come to you site and heat treat any thing. 40 foot long structures were not a problem. BUT what does it do to all the fancy cryogenic stuff we just welded it up around? Also there is the little problem of welding each layer tightly over the previous layer without damaging the inner layer. Maybe developing some repair procedures along the way will make it possible.
Billy mentioned casting which is a serious possibility but creates even harder thermal issues during construction..
Materials selection is going to be a tough nut to crack. And we can’t really dig into it seriously until we get some believable numbers for the magnetic force required.

Example of large whizbang structure: My uncle worked on the space shuttle frame.
It is made from titanium welded in a stainless steel vacuum bag under very high pressures. I think either explosive or HIP. That kind of thing is doable but only with immense budgets. Maybe for production models once the utilities can justify sinking billions into a plant.

I think we all know the value of making each layer and system as stout and light as possible. And what we are doing here is hammering out how.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

Billy Catringer
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Postby Billy Catringer » Sun Mar 15, 2009 10:06 pm

tombo wrote:Yes, stainless steel is probably a 2nd choice but it has its issues.


It is the obvious choice for the cryogenics.

tombo wrote:Full command of my software hah! It took me 10+ hours just to add those jumpers and get everything to line up correctly. Now it would have been faster if I had been less picky about alignment and about trying to keep the link to my structural spreadsheet intact. I’m still in learning mode on this one but it thinks a lot more like me than blender does.


I don't think anyone expects what they find in Blender. Once you start working with it, though, you decide it's not at all bad. OTOH, it was never intended to serve an engineering department. It's greatest virtues are that it is a very powerful piece of software that costs nothing but the time needed to install it and learn to use it.

tombo wrote:The recently posted link to SC properties says that SC fibers are usually bonded together and to their supports using epoxies to hold them together and used in 4K helium. So I think we can include epoxy as a possible material.


Well, that's good news for Kiteman. Anything about costs and who is fabricating with it?

tombo wrote:Speaking of whizbang materials even a good grade Stainless like 316 is tough to work with, especially in large complicated weldments and with leak tightness, and it is not all that strong compared to the really good grades of steel, and it warps if you cycle the heat too much, like every time you do a weld. The whole thing will have to be annealed in a jig to hold it in alignment.


Not if you use the right welding procedures. We fabricate stainless down here all the time and very seldom have to put anything in an oven or even use a rosebud on it. Oh, and the larger the tube or pipe, the easier it is to deal with stainless.

tombo wrote: Billy mentioned casting which is a serious possibility but creates even harder thermal issues during construction.


Not really.

tombo wrote:Materials selection is going to be a tough nut to crack. And we can’t really dig into it seriously until we get some believable numbers for the magnetic force required.


I chose Inconel 690 for the Cool Water jacket because it is high strength and is well behaved in nuclear environments. The real booger-bear is the Hot Water Jacket. Not only is it the largest jacket, it it has to take the most internal pressure and it has to absorb heat fast. I'm pretty sure we will be using a Inconel 690-aluminum-copper-aluminum-Inconel 690 laminate for that bloody thing. Pure copper just ain't gonna cut it.

tombo wrote:Example of large whizbang structure: My uncle worked on the space shuttle frame. It is made from titanium welded in a stainless steel vacuum bag under very high pressures. I think either explosive or HIP. That kind of thing is doable but only with immense budgets. Maybe for production models once the utilities can justify sinking billions into a plant.


Welding titanium for us would not be nearly so problematical as it was for the shuttle team. The key concern when welding titanium is to keep both the parent metal and the filler metals completely free of contamination, particularly any kind of oils. Everyone in the shop must wear white cotton gloves and paper masks to keep the materials clean. Everyone must change their gloves for fresh ones after wearing them for about three hours. The gloves get dry cleaned rather than laundered prior to re-use. The parts must be washed in the proper solvent and allowed to dry prior to welding. The other thing is how you handle your inert gases, argon in this case. You have to be extra careful building your purge dams and in some cases you have to use trailing shields. Working with titanium eats manhours, but it is not the bear it is often made out to be.

I worked on Oxyrane's Monoethylene Glycol Unit. It used a truly hairy process called "acetyl-oxilation. It mixed ethylene and oxygen together two big reactors surrounded by blast bunkers. Fun place to work. I made lots and lots of money. Arco bought them out while I was there and they eventually shut the unit down and sold it for scrap. We had used up about 1/10 the world's annual output in titanium in that one plant.

tombo wrote:I think we all know the value of making each layer and system as stout and light as possible. And what we are doing here is hammering out how.


Yep. The HOW is proving to be wee bit elusive, but we'll catch it sooner or later.

KitemanSA
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Postby KitemanSA » Sun Mar 15, 2009 10:27 pm

Billy Catringer wrote:
KitemanSA wrote:When I started to reply to this yesterday, I was about to just tell you to read what I had already posted. But then Tom Boydston "tombo" did that really nice graphic that I used in my reply to him a few posts back. So I will use it again by reference here. Now I am going to plead with you to read this with a desire to understand, not a desire to find fault. Please.

Yes, yes I have read all of that. I really am trying to understand what you are on about. So far, though, I haven't been able to picture what you want to do.
My graphics capability is limited and it seems my verbal capability is not so good either. I am not real sure how to make it clearer.

Billy Catringer wrote:
KitemanSA wrote:Take the first picture of the two that tombo did above, the one that shows the interconnected piping. Now, in your mind, bow it to a spherical shape. I ask you to imagine that inside those pipes are a system not unlike yours, multi-layers of insulating and heat removing stuff.

Okay, so far, so good. This much I can understand. I keep telling you that it is damnably difficult to do, but you do not seem to want to hear that. Believe me when I tell you that this will result in skyrocketing costs and lengthy delays.
Perhaps I hear it but don't agree. Yes a 4 meter monolithic coil will be a task, but I don't believe it will be as bad as you seem to think.

Billy Catringer wrote:
KitemanSA wrote:At the core is a core pretty much just like yours, EXCEPT that it is laid up over a sphere and because all the coils are interconnected it can have a continuous piece of metal within the core that can take a good deal of membrane loads.

I am not at all sure what you mean by "membrane loads". You are not describing a monocoque structure. Let's say we use a good grade of stainless steel cable to try holding the coil together in this configuration. It would be in the center of the winding. The strands of the coil would simply slide past the cable because of the magnetic field, resulting in a rapidly expanding cloud of coruscating spaghetti.
This is a sketch I did of the basic cross section showing a small scale unit with cryo copper tubing (square tubing). I am in the s l o w process of building this now. I don't expect to be done any time soon.
ImageThis is set up to be the 4 ply dual loop MPG machine that tombo and I have been batting around. Me, mainly but he has provided most of the graphics. This shows 4 layers of coils, individually canned, and attached via themselves and side supports to the main horizontal strength member thru the middle. The pipe is attached around it.

Billy Catringer wrote:Having beat up on you, I think you might have the germ of a good idea here. A tubular net cradling the core might, I emphasize "might", work. The strands of the net would have to be made from flat strips. Mind you, this would lack the rigidity necessary to keep the coils from flapping around like flag. It would not free us from the need for a surrounding jacket to supply that rigidity AND to circulate coolant/moderator. You have to remember that the core will not be in anyway flexible. Think of it as being made of glass.
I don't understand why you say that. If you Google stainless steel and cryogenics and you will find MANY kinds of stainless that retain strength AND ductility to those kinds of temperatures. At least I did.

Billy Catringer wrote:
KitemanSA wrote:(I also prefer a rounder x-section to MSimon's square one, but I can see some benefits either way). The magnet coils are attached to and supported to that continuous backbone of high strength steel. it is also encased in a pipe of high strength steel.

I have been laboring under the assumption that we cannot use ferromagnetic materials. That is why I...would you please get a Yahoo mail account under an assumed name? Then I could e-mail you some numbers. It isn't that hard to set up and I am not going to hunt you down or blow your cover. Maraging steel might do the job, but I was unable to find out if it is ferromagnetic or not.
Mea culpa. I should have specified STAINLESS steel, but I assumed that was understood.

Billy Catringer wrote:
KitemanSA wrote:All the magnetic loads resolve to radial outward loads, and they are supported by the equivalent of hoop stresses in that backbone and pipe.

Okay, NOW I can see what you meant by "hoop stress". I'm a petrochem guy. When you say "hoop stress" to me, I think you mean the stresses resulting from pressure in a pipe or a vessel.
Effectively, that is exactly what I AM saying, only the pressure is on the hoop of magnet, not the pipe, and it gets transfered into the backbone..

Billy Catringer wrote:
KitemanSA wrote:NONE of the magnetic stresses need be reacted outside the core container. The core container need only be supported against gravitational loads by the outside members.

I don't agree with this because my experience with magnets suggests that bad things will happen. Perhaps if we were in freefall things would be different, but this thing will not be built in freefall anytime soon. If the magnetic fields were perfectly aligned and were never perturbed by anything, your idea might hold water. We ain't that lucky. The problem becomes even more troublesome when you start thinking about putting one of these things into a moving vehicle.
Since everything in my concept is at the lowest potential energy, magnet wise, I am not sure what could happen. The round torii that you are now proposing on the other hand will have all SORTS of weird and troublesome torques and forces.

Billy Catringer wrote:
KitemanSA wrote:A now very light weight TPS (thermal protection system) can be connected to a similar design of neutron protection system and only supported against gravity loads. Said loads will be quite within the reach of thin section typical metals.


Don't I just wish. I'll need a lot more detail before I buy into this one. The coolants are fluids that have to be pumped through the system fast enough that these light metals will not see too much pressure and rupture. Just as importantly, the coolants will have to pumped through the system fast enough to avoid having the heat reach the SC core. Out of that comes a lot of vibration. Vibration will cause the SC cores to move around which will in turn perturb the magnetic fields, which would, sooner or later, result in cracks in the SC coil and we have our rapidly expanding cloud of coruscating spaghetti.
I guess you didn't notice that my core is not connected in any way to the N&TPS. No vibration path between them. Neat, no?
Billy Catringer wrote:
KitemanSA wrote:1) Staggered buttons of aerogel or the like. 2) Why in the world would you think I want to cool them? The foil will naturally take on the temperature ~1/2 way between the two radient surfaces on either side. In doing so, it cuts energy transmission MARKEDLY. I think it is a 4th power rule.


And after the outermost layer of foil evaporates? The innermost layers will not protect the outermost one.
Seems you missed the "between courses" statement. I don't envision any foil on the outside. As you say, that would soon melt (unless it were somethying like Thorium perhaps, but why?) No, foil between the #1&2, 2&3, and 3&4 vacuum spaces will suffice.
More later. Dinner time.

Billy Catringer
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Postby Billy Catringer » Mon Mar 16, 2009 12:02 am

For someone who has poor graphic capabilit8ies, you did pretty good job there, Kite. Maraging steel is out. It is ferromagnetic. I'll wait until after your next post to offer comment.

KitemanSA
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Postby KitemanSA » Mon Mar 16, 2009 12:30 am

tombo wrote: The bowed coil segments are MUCH harder for me to draw.
I am assuming the pipes you have in this model are actually conformal to a sphere.
Image
Take this model. Orient it so that the pipes are coming in at the 45 degree angle (near Bourdeaux, 0,45 long-lat) and the first two tangential legs of the inlet and last two tang legs of the outlet top form a "square" around the "North Pole". Copy this model and paste it back into your model. Rotate it 90 degrees around the north pole. Do that twice more with 180 and 270 degree rotations. Show us. It SHOULD be the drawing I want.

tombo wrote:Vertex count: the square planform truncube has 12 vertexes. When you add the cross connects it essentially adds 8 triangular coils (at the cube vertexes) and it converts each of those 8 four sided vertexes into 4 three sided vertexes. It essentially adds 12 more (square-ish) faces to the polygon which are located at the funny cusps which are at the middles of the original edges.
Each connection of the 4 magnets yields one vertex. Like this.
Image

KitemanSA
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Postby KitemanSA » Mon Mar 16, 2009 1:13 am

Ok. Dinner is done, now on with the show!
Billy Catringer wrote:
KitemanSA wrote:I was going to wait to bring this up, but I also think we should rethink the outer water course and use some other material like eutectic NaK or other liguid metal. True we would need some replacement for the H in the water to moderate the neutrons, but... This is still up for discussion as I am not wed to anything on this now.

What is the ratio of potassium to sodium in this solution you are championing? Have you calculated what it will weigh? Have you thought about the vibration that pumping it around in your lightweight structure will cause? You do realize that molten alkali metals are one of the major drawbacks to the ITER design, right? Mineral oil would be a safer and far less troublesome replacement for water, but both of the real-live Nuke-E's we have on this board have both rejected mineral oil as well.
I don't know the exact ratios, it is the eutectic mixture. That is a specific combination. I suppose you could call it a solution, but with metals it is usually called an alloy. As to ITER, they are using tonnes and tonnes of Lithium to breed more Tritium. I am proposing to use a much smaller amount as a heat transfer fluid. Others may work, but I dislike having to restrain water at the 600C I've been hearing bandied about. Most nukes are restricted to MUCH less than that for strength concerns and other reasons. Unless of course I missed something and the intent is to let this boil. Talk about vibration!

Billy Catringer wrote:
KitemanSA wrote:The magnet does not induce loads on the stainless or the copper or the water or the..., at least not to any significant degree. If your react the MAGNET's magnetic loads out as I have described, the TPS becomes a light add on, probably supported independantly by the outermost course, not touching the inner most course at all. This would actually allow more slop in construction tolerances.

If, IF, we could do what you describe, maybe. What you want to do is to cancel the loads from the magnetic fields by using internal tension members. Bucky Fuller would be proud of you. Convince me that perturbations will not suddenly eat us alive in such a system. I don't think there are any metals that can be used for that kind of load at LHe temperatures. Do you have one in mind? Carbon fiber might do the job, I don't know, but then you will have to show me that there is a combination of supplier/shop that can figure out how to build within a year and at less than astronomical costs.
I recently read an article about a wide range of stainless steels that could take those temperatures and retain much of its strength and toughness. Since the YBCO HTS tape and some versions of the MgB tape use stainless as a strength member, I figure we can use a similar metal.

Re Bucky, I think he would be disgusted with anything less than an icosadodec, these cuboctos are WAY too simple for him!

Billy Catringer wrote:
KitemanSA wrote:I think that the magnet's magnetic loads should be reacted out within the inner-most course and be done with. See above. If you still don't get it, I will take the time to draft up more crude graphics.

If you want me to model it, you gotta send me a sketch and wait while I finish sorting out how to use this program. You would likely get faster results from Tombo because he is obviously a talented draftsman and is already in full command of his software.

To model this thing, follow the following algorythm.
Select an expected core diameter and sphere size.
Model a torus around the sphere, north to south, thru the 0 degree longitude line.
Rotate that torus around the 0,0 point, 35.2644 degrees clockwise.
Copy that torus and paste it back into the model overlaying the original.
Rotate that torus 90 degrees about the north pole.
Repeat 2 more times with 180 and 270 degree rotations.
At each intersection, replace the piping with a holey X like I drew above for tombo (only pipe). Ta-daa.
The angle I provide is for plane geometry. With spherical, that may change a tad. The angle should be chosen to make that rotated torus overlay the -45, 45 degree point.

Billy Catringer wrote:At any rate, I would very much like to see a picture of what you have in mind. And, I must add, the finished drawings should be done to scale. We need to be doing more than brochure grade stuff at this point.

I am still trying to get tombo to create the basic shape. The cross-section (one notional) is also shown above. If there is an issue with the stability of this item, then the backbone can be moved inward and more of the magnet could be "suspended" by it rather than "supported" by it.
Billy Catringer wrote:
KitemanSA wrote:Then please explain why the strongest high temperature fiber known to man is beta SiC? Gee this tensile structure I have described may have to be made with woven fiber, perhaps potted in other ceramic, perhaps just properly wound around the piping providing the LHe. Mayhaps the pipe carrying the LHe would be strong enough to carry the loads and the SiC would just be an insulator.

Okay, you are talking about FIBROUS, not solid SiC. That is a very different beast. I assume you intend to use this material for your structural cables. I won't argue with you about that, but I do suggest that you check to be certain of its behavior at temperatures in the low Kelvins. While you are about it, you need to be thinking about who we would buy this stuff from and who we could contract to fabricate it.
But of course!

Billy Catringer wrote:I read about these wizzy-bangy materials all the time, but I damned seldom read of anyone who is actually using them for anything very large if anything at all. You might want to think about tungsten core boron fiber while you are at it. Also, remember that nearly all of these fiber composite materials rely on epoxies to hold them together.
KitemanSA wrote:The thermal protection and neutron conversion/protection system should be made as light and thin as possible and reacted out thru one of the layers of that system.

Again, you are not being clear about what you mean. Could and should I already know about. What I need to know from you is HOW. I am not trying to be an egotistical prig here. Investors and the experts they hire will be demanding to know the same things.
It is my opinion that if you add up all the suggestions made so far, foil, truss core HEXs, different coolants, reacting the magnetic loads out thru the core directly (no heavy pipe with shoes to react those loads) and hanging the rest of the TPS by a different structure, we can achieve that much smaller, lighter TPS.

tombo
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Postby tombo » Mon Mar 16, 2009 5:25 am

In you x shaped picture I see 4 three sided vertexes.
One between 1 and 2 another between 2 and 3 another between 3 and 4 another between 4 and 1.
You sure have shown that opening small.
I thought we were trying to keep the metal out of the way of the cusp region.
It looks a lot cleaner in 2D that it works out in 3D.
But, like I said I can make it any aspect ratio and any width or height. Pick 2 of the 3.
I also assumed tangential connections.

Your algorithm is confusing:
To model this thing, follow the following algorythm.
Select an expected core diameter and sphere size.
Model a torus around the sphere, north to south, thru the 0 degree longitude line. [ok Greenwitch]
Rotate that torus around the 0,0 point [you mean the planet core? around which axis the planet rotation axis?], 35.2644 [where did this number come from?] degrees clockwise[around which axis? the planet rotation axis?].
Copy that torus and paste it back into the model overlaying the original.[if it overlays the original why not just say do the next step with the original and be done with it?]
Rotate that torus 90 degrees about the north pole.[ok so now we have rotated it 90+35.2644 degrees. but wait if we are now rotating around the north pole which axis were we rotating it about before?]
Repeat 2 more times with 180 and 270 degree rotations.
At each intersection, replace the piping with a holey X


I thought I knew what shape you meant. Now I don't know at all.
How do these tori fit onto the original cube of the W6 shaped device?
How many tori do you wind up with at the end?
-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

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Postby tombo » Mon Mar 16, 2009 5:52 am

Square loop & triangle loop fields.
From: http://www.tutorvista.com/content/physics/physics-iv/moving-charges-magnetism/numerical-02.php

Square loop B at the center of a square 1 turn coil B=(sqrt(2)*u0*I)/(pi*(side_of_square/2))
Similarly:
Triangle loop for 1 leg B=I*(u0/(4pi*(distance_to_center))*2*sin(60)=I*(u0/(4pi* distance_to_center))*2*SIN(Pi/3)=I*1e-7*2*SIN(Pi/3)/ distance_to_center
Triangle loop total B=3*2*I*1e-7*SIN(Pi/3)/(distance_to_center)=I*6*1e-7*SIN(Pi/3)/((side_length)/2)
Where “distance_to_center” is the perpendicular distance from center of the equilateral triangle to the middle of a side.
Putting these into a spreadsheet I get:

[Well, mostly I get garbage because the forum’s editor eats any spreadsheets, tables, tabs or spaces I use to line up the data columns. I’m afraid you will just have to count the 2 columns of Labels and the 3 columns of data]

Current I 2,721,655 13,608,276 27,216,553
Polywell "Radius" Rpw 2 2 2
Polywell CubeSide Sc 4 4 4
CoilSide (diamond shaped) Ss 2.828 2.828 2.828
permitivity of vacuum u0 1.257E-06 1.257E-06 1.257E-06
B at center of square coil Bsquare 1.09 5.44 10.89
B at center of Triangular coil Btriangle 1.00 5.00 10.00

The center of the (virtual) Triangular coil is the lower B field for a given current, so it is the controlling point that determines the coil current.

Blackbody Temperature
Find black body temperature of an uncooled part at the Magrid location.
Assuming 100MW 2m radius, outer wall at 648K = critical point of steam (boiler outer wall) Power Flux=emissivity*Stephan Boltzman constant*Area*T^4, reactor power flux is on ½ of the surface area, radiant heat from the wall and to the wall is from the whole surface area.

[Again Well, mostly I get garbage because the forum’s editor eats any spreadsheets, tables, tabs or spaces I use to line up the data columns. I’m afraid you will just have to count the 1 column of Labels and the 6 columns of data]

emissivity 0.05 0.2 0.5 0.7 1 0.9
Temp K 4,328 3,062 2,437 2,241 2,052 2,502
Temp C 4,055 2,789 2,164 1,968 1,779 2,229

The last column does not reduce thermal input but uses the full surface area for both absorption and radiation.
It models a graphite (3500C) surface facing toward the heat source. And it works. It needs no conduction across the part to work.

If we can get the emissivity up then the temperatures are not too obscene.
But, Yes, they are very tough.
It would help a lot to orient any structural ties edge-on to the heat source.
I can get down to quite reasonable temperatures depending on the assumptions.
The radiation comes from an extended source, so this strategy has a limit.
Another help is the fact that a large part of the surface faces partly or wholly the nearby actively cooled Magrid itself which is at a cooler temperature.

But, this assumes the part conducts heat away from the surface facing the center to the re-radiating surfaces (not really a good assumption). Although it could have graphite (3500C) coating on the surface to shield the strength portion from the worst of the heat.

I’m not saying it is a done deal I’m saying it might be possible to use a few strategically placed, well designed, non cooled parts.
This analysis also suggests that coating the main Magrid with a layer of graphite might be a viable strategy to reduce heat load on the outer water jacket.

It might be especially viable for solving the problem of the superheated skin of the first wall layer.
A pyrolytic graphite coating should be deposit-able in situ after assembly.
Perhaps just a thin layer to protect the Boron (mp=2300C) layer on the outside of the Magrid.
-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

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Postby blaisepascal » Mon Mar 16, 2009 12:49 pm

tombo wrote:Your algorithm is confusing:
To model this thing, follow the following algorythm.
Select an expected core diameter and sphere size.
Model a torus around the sphere, north to south, thru the 0 degree longitude line. [ok Greenwitch]
Rotate that torus around the 0,0 point [you mean the planet core? around which axis the planet rotation axis?], 35.2644 [where did this number come from?] degrees clockwise[around which axis? the planet rotation axis?].
Copy that torus and paste it back into the model overlaying the original.[if it overlays the original why not just say do the next step with the original and be done with it?]
Rotate that torus 90 degrees about the north pole.[ok so now we have rotated it 90+35.2644 degrees. but wait if we are now rotating around the north pole which axis were we rotating it about before?]
Repeat 2 more times with 180 and 270 degree rotations.
At each intersection, replace the piping with a holey X


I thought I knew what shape you meant. Now I don't know at all.
How do these tori fit onto the original cube of the W6 shaped device?
How many tori do you wind up with at the end?


Let me try....

A cuboctahedron, standing on a triangular face, has a set of six edges which are horizontal and in the same equatorial plane. They form a regular hexagon girding the middle of the cuboctahedron, dividing it into two equal halves. There are four such hexagons on a cuboctahedron, neatly partitioning the 24 edges of the cuboctahedron.

Each of those hexagons corresponds to a torus in KitemanSA's algorithm.

On a cube with corners of (± 1, ± 1, ± 1), one hexagon connects the points at (0,1,1), (1,0,1), (1, -1, 0), (0,-1, -1), (-1, 0, -1), (-1, 1, 0), and back to (0,1,1). The other three can be gotten by rotating 90, 180, and 270 degrees about one of the x,y,and z axis.

The approximately 35 degree figure comes from the tilt of one of these hexagons from vertical.

Does that help?

KitemanSA
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Postby KitemanSA » Mon Mar 16, 2009 3:08 pm

Tombo;
To model this thing, follow the following algorythm.
Select an expected core diameter and sphere size.
Model a torus around the sphere, north to south, thru the 0 degree longitude line. [ok Greenwitch]
Yes.

Rotate that torus around the 0,0 point [you mean the planet core? around which axis the planet rotation axis?]
(0,0) - Greenwich at the equator, 0 lat, 0 long.
35.2644 [where did this number come from?]
It is the angle needed to turn the torus so that it overlays (0, 0) and the point at (45, -45) (the top of the "square" coil to the right of (0, 0) and with copying and rotation, all the other vertices of the "square" coils.

degrees clockwise[around which axis? the planet rotation axis?].
The one at the center of the "clock". The one thru (0,0), yes thru the center of the Earth. If you look at the holey X sketch I posted yesterday, the legs come in at an angle of 35.2644 degrees from the vertical (actually, I plotted them at 35.25, but don't tell anyone :wink: ).

Copy that torus and paste it back into the model overlaying the original.[if it overlays the original why not just say do the next step with the original and be done with it?]
Because the original needs to stay there. We need ANOTHER one (three actually) to rotate.

Rotate that torus 90 degrees about the north pole.[ok so now we have rotated it 90+35.2644 degrees.
Different axis of rotation. North pole this time.

but wait if we are now rotating around the north pole which axis were we rotating it about before?]
The one thru (0,0); the center of the "clock".

Repeat 2 more times with 180 and 270 degree rotations.
At each intersection, replace the piping with a holey X

I thought I knew what shape you meant. Now I don't know at all.
How do these tori fit onto the original cube of the W6 shaped device?
If you used pairs of curves rather than a holey X, you would get your marvelous bowed MPG, exactly. Indeed, I thought you had done it this way.
How many tori do you wind up with at the end?
Four; the original and 3 copies, each rotaed 90 degrees relative to the next.

tombo
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Postby tombo » Mon Mar 16, 2009 6:53 pm

Oh, You mean arrayed 4 times around the Z axis.

Image

Image

Image

Image

This looks just about like what I did before except for the extra copies of the feed lines.
This is inscribed in a 4m cube with 20" thick coils.
These parameters should be easy to change. (unless the model crashes again.)
Also what is your minimum bend radius? Notice that the square (90 deg bend) and triangle (60 deg bend) have different bend radii. I needed that flexibility because in the first version I wanted to make the metal to metal distance the same on the 2 different kinds of kissings. I did not optimize this version for that.

Looks like there will be voids inside the crossovers.
That might give much needed elbowroom for connecting to feed lines etc.
Although the feedlines would need to be repositioned to feed into the areas with voids. (That is easier said than done because of the way the model was put together.)
-Tom Boydston-

"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein


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