Here lies the critical path!

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

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Billy Catringer
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Here lies the critical path!

Post by Billy Catringer »

Assuming we want to use the p-11B reaction, boys and girls, someone needs to be working on a way to adapt this to a BFR, right now, not tomorrow or the next day.

http://www.askmar.com/Fusion_files/Prel ... 0Blind.pdf

Golly gee! This is a big son-of-a-gun! Oh, and on the ribbons, don't talk to me about anything other than stainless steel or woven graphite. Also, think MINERAL OIL, not water for a coolant. Also think, "Small is beautiful. Small is beautiful. Small is beautiful. Small is beautiful."

Holy Brobdingnag, Laputa!

MSimon
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Re: Here lies the critical path!

Post by MSimon »

Billy Catringer wrote:Assuming we want to use the p-11B reaction, boys and girls, someone needs to be working on a way to adapt this to a BFR, right now, not tomorrow or the next day.

http://www.askmar.com/Fusion_files/Prel ... 0Blind.pdf

Golly gee! This is a big son-of-a-gun! Oh, and on the ribbons, don't talk to me about anything other than stainless steel or woven graphite. Also, think MINERAL OIL, not water for a coolant. Also think, "Small is beautiful. Small is beautiful. Small is beautiful. Small is beautiful."

Holy Brobdingnag, Laputa!
There is a lot of time to work this out. We don't even have anything close to a net power machine yet.
Engineering is the art of making what you want from what you can get at a profit.

KitemanSA
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Post by KitemanSA »

If a 4m diameter BFR makes 100MW at 100% efficiency with a direct conversion (not possible, but I can dream), then to get 100MW with a high temperature thermal cycle (850C) it would have to be all of ~4.5m diameter. Let us get it working first, then worry about direct conversion.

choff
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dumb question

Post by choff »

Have dumb question. I recall being told way back when that when you super cool hydrogen to near absolute zero it becomes liquid and superconductive. If a coolant existed that was superconductive, wouldn't it be possible to form the magrid coils out of the coolant pipe itself, reducing complexity within the casing.
CHoff

hanelyp
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Re: dumb question

Post by hanelyp »

choff wrote:I recall being told way back when that when you super cool hydrogen to near absolute zero it becomes liquid and superconductive.
How close to absolute zero? If less than liquid helium temperatures the hydrogen would be frozen solid. And the colder you have to run the more refrigeration is a problem. But a liquid phase superconductor would have some possibilities.

Billy Catringer
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Re: Here lies the critical path!

Post by Billy Catringer »

MSimon wrote: There is a lot of time to work this out. We don't even have anything close to a net power machine yet.

Chief, we'll have the magnets done and we'll be waiting on the Brogdingnag. Without the Brobdingnag, we will be little more than a glorified steam generator. Making steam is fine for the recovery of waste heat, but it is not the way this beast should work. Mind you, direct conversion is the way to go with the D-D or the D-T reactions as well.

I won't be that much longer on these magnets and then it will be time to start work on the structure that holds them in place. That means we'll be wanting to size the vacuum vessel in the not-to-distant future. The Brobdingnag will have to tie into the vacuum vessel and we need to know how to install concrete around the vacuum vessel. All that will be on hold if we don't have any idea about how that thing will tie-in to the rest of the system.

MSimon
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Re: Here lies the critical path!

Post by MSimon »

Billy Catringer wrote:
MSimon wrote: There is a lot of time to work this out. We don't even have anything close to a net power machine yet.

Chief, we'll have the magnets done and we'll be waiting on the Brogdingnag. Without the Brobdingnag, we will be little more than a glorified steam generator. Making steam is fine for the recovery of waste heat, but it is not the way this beast should work. Mind you, direct conversion is the way to go with the D-D or the D-T reactions as well.

I won't be that much longer on these magnets and then it will be time to start work on the structure that holds them in place. That means we'll be wanting to size the vacuum vessel in the not-to-distant future. The Brobdingnag will have to tie into the vacuum vessel and we need to know how to install concrete around the vacuum vessel. All that will be on hold if we don't have any idea about how that thing will tie-in to the rest of the system.
I expect the first unit will be strictly a thermal unit to prove net power is possible. Unit #2 - WB101 - will have the power conversion added. We take measurements on WB-100 and use those numbers for WB-101.
Engineering is the art of making what you want from what you can get at a profit.

chrismb
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Re: Here lies the critical path!

Post by chrismb »

Doesn't it look grand, on a piece of paper?!

So, just a couple of initial questions, a) isn't this presuming the dimensions of the paper, viz. 2-D? How do you take a 3D emission of particles and get them all streaming out in a plane? b) how do you get them streaming down those little tubes with the bending magnets and 'neutron absorber' in it, c) why bother absorbing neutrons? Something is going to get activated, why not the gubbins further out?
Billy Catringer wrote:Mind you, direct conversion is the way to go with the .... D-T reactions as well.
80% of the DT output is neutrons, not sure why you think think the DC fantasy conversion scheme is suitable.

MSimon
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Post by MSimon »

How do you take a 3D emission of particles and get them all streaming out in a plane?
From my reading of the paper the proposed collector is conical.
Engineering is the art of making what you want from what you can get at a profit.

Billy Catringer
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Re: Here lies the critical path!

Post by Billy Catringer »

chrismb wrote:Doesn't it look grand, on a piece of paper?!

Too grand by two orders of magnitude.
chrismb wrote:So, just a couple of initial questions, a) isn't this presuming the dimensions of the paper, viz. 2-D? How do you take a 3D emission of particles and get them all streaming out in a plane? b) how do you get them streaming down those little tubes with the bending magnets and 'neutron absorber' in it, c) why bother absorbing neutrons? Something is going to get activated, why not the gubbins further out?

The logical thing to do is build a collector of a suitable shape--and size. Absorbing the neutrons is a good idea if it
leads to more useful output.
chrismb wrote:80% of the DT output is neutrons, not sure why you think think the DC fantasy conversion scheme is suitable.

A number that falls somewhere between twenty and forty percent, assuming that a particle catcher of reasonable size can be built.

KitemanSA
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Post by KitemanSA »

REMEMBER, its a mezely 12% difference in MAGRID size between a 90% efficient direct conversion and a 45% thermal. Lets make it work FIRST, then argue generation.

MSimon
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Post by MSimon »

Consider the headlines you would like to see from the first prototype:

Fusion a success!

vs:


Fusion a success! Direct conversion fails.

There is also the question of keeping the initial prototypes as simple as possible.
Engineering is the art of making what you want from what you can get at a profit.

Billy Catringer
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Post by Billy Catringer »

Okay, Chief. I thought it over and decided I was wrong. I'm not far wrong, but I'm wrong. Nuff said.

MSimon
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Post by MSimon »

The question is important. It ought to be studied.

It is not currently on the critical path.

Look at it this way: if an operating prototype has a real Q of 2 then a 3X to 5X improvement is a big deal. If the Operating Q is 10 or above a Q improvement of 3X to 5X does not gain you much. OTOH reactor building size and cost is definitely helped by a smaller reactor.

In any case I am just a fiend about critical paths.
Engineering is the art of making what you want from what you can get at a profit.

Billy Catringer
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Joined: Mon Feb 02, 2009 2:32 pm
Location: Texas

Post by Billy Catringer »

MSimon wrote:The question is important. It ought to be studied.

It is not currently on the critical path.

Look at it this way: if an operating prototype has a real Q of 2 then a 3X to 5X improvement is a big deal. If the Operating Q is 10 or above a Q improvement of 3X to 5X does not gain you much. OTOH reactor building size and cost is definitely helped by a smaller reactor.

In any case I am just a fiend about critical paths.

We do need to hammer out a schedule of some kind. I don't have any scheduling software on my machine. That was a deliberate choice because somewhere along the way I got sick of scheduling and started turning down that kind of work. Geez! I'm thinking about doing a PERT chart in Blender. I think I'll take an aspirin and lie down for a little while.

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