Z-Pinch Renaissance

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Tue Oct 15, 2019 8:48 am

paperburn1 wrote:there are a lot of ideas out there
http://www.projectrho.com/public_html/r ... #radiators


Yes, but most of those ideas are just marginal improvements in respect of the needs of a human rated ship.
I believe that the field needs a radical change of approach to the issue to the point where radiators could be eliminated or integrated in the body of the ship itself with multiple redundant system.
They are after all the principal point of failure on any machine/system/spaceship that requires getting rid of huge amounts of heat to actually perform some work. Just imagine what few micrometeorites could cause to a traditional array of radiators traveling toward one of the outer planets, and imagine the extra weight of the spare parts/components/fluids that should be accounted to enable a safe bidirectional trip.
A society of dogmas is a dead society.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Tue Oct 15, 2019 9:08 am

Skipjack wrote:Looks like ZAP is hiring, some of the jobs mention their next generation (scientific break even) device:
https://careers.aps.org/jobs/?keywords= ... 0Inc%2E%22


I have seen your exchange of messages at NBF. I plaud your efforts to actually explain them what the ZAP Z-pinch is trying to prove, but some people are just too narrow minded and self referential to actually be able to accept that the knowledge they have cannot be used to explain something that science didn't explore yet.
Nevertheless, GG has a point about the AMP, but I am confident that it could easily be overcome if ZAP releases some new experimental data that could clarify where their aim and target really is going to be. Until then I am afraid you will not be able to get much of a meaningful discussion form the people there :mrgreen:.
A society of dogmas is a dead society.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Tue Oct 15, 2019 1:48 pm

Giorgio wrote:
Skipjack wrote:Looks like ZAP is hiring, some of the jobs mention their next generation (scientific break even) device:
https://careers.aps.org/jobs/?keywords= ... 0Inc%2E%22


I have seen your exchange of messages at NBF. I plaud your efforts to actually explain them what the ZAP Z-pinch is trying to prove, but some people are just too narrow minded and self referential to actually be able to accept that the knowledge they have cannot be used to explain something that science didn't explore yet.
Nevertheless, GG has a point about the AMP, but I am confident that it could easily be overcome if ZAP releases some new experimental data that could clarify where their aim and target really is going to be. Until then I am afraid you will not be able to get much of a meaningful discussion form the people there :mrgreen:.

ZAP needs currents orders of magnitude below what MIFTI does. It is a completely different league. That said, I am still happy for the MIFTI people. They have been working hard on progressing their design and deserve the recognition. Whether it will lead to a practical reactor is a different issue, though.
In any case, many of the design lessons learned from MIFTI could help ZAP as well.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Tue Oct 15, 2019 2:27 pm

Indeed, but they don't seem to care about the differences there, they tend to generalize all the issues too much for my taste.

.
A society of dogmas is a dead society.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Tue Oct 15, 2019 3:30 pm

Giorgio wrote:Indeed, but they don't seem to care about the differences there, they tend to generalize all the issues too much for my taste.

.

I agree. Well, we will see if they put on a different tune in a few years from now.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Tue Oct 15, 2019 9:17 pm

Just noticed that GG made a mistake in his calculations. He assumed a neutron yield per second. I am pretty sure that they are talking about a neutron yield per shot. One of their shots lasts a few nanoseconds...

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Wed Oct 16, 2019 1:53 am

Skipjack wrote:Just noticed that GG made a mistake in his calculations. He assumed a neutron yield per second. I am pretty sure that they are talking about a neutron yield per shot. One of their shots lasts a few nanoseconds...

Exactly. Even with revised math he still has a good point when he mention MAP requirements, but again, he is trying to study new science with old theories and math developed on older researches.
People should be waiting to get actual experimental data and see if/how they will fit into the new model before jumping to conclusions.

Just my 0.02 $.
A society of dogmas is a dead society.

williatw
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Re: Z-Pinch Renaissance

Postby williatw » Wed Oct 16, 2019 10:21 am

Third-generation fusion fuels

3He + 3He → 4He+ 211p 12.86 MeV 0

https://en.wikipedia.org/wiki/Helium-3

What about this reaction mixture? I remember hearing about it but it isn't talked about much. You could get the He3 from the decay of Tritium bred from Lithium as has been discussed, or from the atmospheres of the gas giants Saturn, Uranus, Neptune (likely not Jupiter too much radiation belts). Given the advanced fusion drives being discussed the outer solar system is obviously reachable.

The second possibility, fusing 3He with itself (3He + 3He), requires even higher temperatures (since now both reactants have a +2 charge), and thus is even more difficult than the D-3He reaction. However, it does offer a possible reaction that produces no neutrons; the charged protons produced can be contained using electric and magnetic fields, which in turn results in direct electricity generation. 3He + 3He fusion is feasible as demonstrated in the laboratory and has immense advantages, but commercial viability is many years in the future

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Wed Oct 16, 2019 11:56 am

williatw wrote:Third-generation fusion fuels

3He + 3He → 4He+ 211p 12.86 MeV 0

https://en.wikipedia.org/wiki/Helium-3

What about this reaction mixture? I remember hearing about it but it isn't talked about much. You could get the He3 from the decay of Tritium bred from Lithium as has been discussed, or from the atmospheres of the gas giants Saturn, Uranus, Neptune (likely not Jupiter too much radiation belts). Given the advanced fusion drives being discussed the outer solar system is obviously reachable.

The second possibility, fusing 3He with itself (3He + 3He), requires even higher temperatures (since now both reactants have a +2 charge), and thus is even more difficult than the D-3He reaction. However, it does offer a possible reaction that produces no neutrons; the charged protons produced can be contained using electric and magnetic fields, which in turn results in direct electricity generation. 3He + 3He fusion is feasible as demonstrated in the laboratory and has immense advantages, but commercial viability is many years in the future

I presume you are thinking of this for the SFS Z- Pinch and not for the Staged Z- Pinch, Giorgio and I were just talking about.
Like for D+He3 fusion, they would probably make the He3 in dedicated fusion reactors: D+D -> He3 + n (and T + p in the other branch with half the T decaying to more He3 after 12 years). I presume that the neutron from D+D->He3 could be used to breed even more T in a lithium blanket.
I see little advantage for He3 + He3 over D+He3. The cross section is smaller than for D+He3. So the gain would be lower. For a space drive, it would mean more expensive fuel. Plus, the capacitors to drive the higher current would be larger and the Z- Pinch would have to be longer. Not sure how exactly it would compare to their proposed PB11 space drive version, but that could be a useful baseline for comparisons. There would probably be some advantages in regards to less neutron shielding and the exhaust would not contain any Tritium from D+D side reactions. But I am not sure how well all that would make up for the mass gain in the other areas. Maybe some time in the far future, this would be feasible, but I would not hold my breath for the near future.
Last edited by Skipjack on Wed Oct 16, 2019 2:30 pm, edited 1 time in total.

Giorgio
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Re: Z-Pinch Renaissance

Postby Giorgio » Wed Oct 16, 2019 2:23 pm

williatw wrote:Third-generation fusion fuels

3He + 3He → 4He+ 211p 12.86 MeV 0

https://en.wikipedia.org/wiki/Helium-3

What about this reaction mixture? I remember hearing about it but it isn't talked about much.


Skipjack already gave you good indication.

I want to add that is not talked much also because it has the highest temperature requirements of all potential fuels (more than 900keV, against the 300keV of a pB11 or the 50keV of a D-T), and it has (at least in theory) Bremsstrahlung losses that are much greater than the fusion gain.
These 2 issues makes it the worst among the fuels for any type of application, and that's why is not much researched at the moment.
A society of dogmas is a dead society.

williatw
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Re: Z-Pinch Renaissance

Postby williatw » Wed Oct 16, 2019 2:32 pm

Skipjack wrote:I presume you are thinking of this for the SFS Z- Pinch and not for the Staged Z- Pinch Giorgio and I were just talking about.
Like for D+He3 fusion, they would probably make the He3 in dedicated fusion reactors: D+D -> He3 + n (and T + p in the other branch with half the T decaying to more He3 after 12 years). I presume that the neutron from D+D->He3 could be used to breed even more T in a lithium blanket.
I see little advantage for He3 + He3 over D+He3. The cross section is smaller than for D+He3. So the gain would be lower. For a space drive, it would mean more expensive fuel. Plus, the capacitors to drive the higher current would be larger and the Z- Pinch would have to be longer. Not sure how exactly it would compare to their proposed PB11 space drive version, but that could be a useful baseline for comparisons. There would probably be some advantages in regards to less neutron shielding and the exhaust would not contain any Tritium from D+D side reactions. But I am not sure how well all that would make up for the mass gain in the other areas. Maybe some time in the far future, this would be feasible, but I would not hold my breath for the near future.


I believe that the PB11 reaction according to one of your posted sources has a couple of nasty side reactions; don't think the He3 + He3 reaction does. Presumably the 2 lighter protons in addition to the He4 product would be easier to steer to generate thrust; and likely have a higher SI than the He4 +P product of the D-He3 does. It is described in my posted source along with the PB11 as a "Third-generation fusion fuels" as opposed to the described "Second-generation" for the D+He3 reaction; so obviously not initially useful but worth a look. As for the greater fuel cost yes; but I was assuming the afore mentioned gas giant sources for the He3. Assuming several dozen or eventually hundred(s) of the Z-pinch 33TW propulsion system rockets demand for fuel would go way up; probably more than Earth would be inclined to want to export. Besides our hypothetical "spacers" would probably be an independent breed who wouldn't want to be solely dependent on Earth for their fuel even if initially it was cheaper. I have heard figures of trillions of tons of recoverable He3 in the atmospheres of the gas giants at many orders of magnitude greater concentration than say lunar regolith.

paperburn1
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Re: Z-Pinch Renaissance

Postby paperburn1 » Wed Oct 16, 2019 3:08 pm

Pardon the platitude but
I think we need t dance with the girl we brought to the dance.
He3 is not available or a ready source available.
IMHO we should strive for PB11 or D-D
I am not a nuclear physicist, but play one on the internet.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Wed Oct 16, 2019 3:20 pm

paperburn1 wrote:Pardon the platitude but
I think we need t dance with the girl we brought to the dance.
He3 is not available or a ready source available.
IMHO we should strive for PB11 or D-D

Well, if you can do D+D, then you can make He3 as a fusion product. That is what Helion is doing with their reactor. First fuse D+D, then fuse the He3 which is a product of the reaction with more Deuterium. The reaction is a lot more energetic than D+D.
PB11 was investigated by Uri Shumlak for the SFS Z- Pinch space drive and it was inferior to D+He3. That said, right now I would be happy to see them reach scientific break even (for D+T)... Though it _is_ fun to speculate a little ;)

williatw
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Re: Z-Pinch Renaissance

Postby williatw » Thu Oct 31, 2019 8:21 pm

Skipjack wrote:
paperburn1 wrote:Pardon the platitude but
I think we need t dance with the girl we brought to the dance.
He3 is not available or a ready source available.
IMHO we should strive for PB11 or D-D

Well, if you can do D+D, then you can make He3 as a fusion product. That is what Helion is doing with their reactor. First fuse D+D, then fuse the He3 which is a product of the reaction with more Deuterium. The reaction is a lot more energetic than D+D.
PB11 was investigated by Uri Shumlak for the SFS Z- Pinch space drive and it was inferior to D+He3. That said, right now I would be happy to see them reach scientific break even (for D+T)... Though it _is_ fun to speculate a little ;)



Liquid Helium (4) has a density of "The density of liquid helium-4 at its boiling point and a pressure of one atmosphere (101.3 kilopascals) is about 0.125 grams per cm3, or about 1/8th the density of liquid water." I will assume that the density of He3 is 3/4X.125g/cm3=.09375g/cm3. About 94KG per cubic meter

https://en.wikipedia.org/wiki/Helium-3

Boron 11has a density of "2.34 g/cm3 (25 °C)".

https://www.americanelements.com/boron- ... 14798-13-1

Works about to be about 2340KG per cubic meter. So a storage container of one cubic meter would contain (2340/.011) = 213K moles of B11. For Helium 3 that works out to be 94kg/.003=31K moles of He3. So B11 has more reactant moles 213K vs 31K for the He3. Of course the reactions energies are different 8.68 MeV for B11/H vs 18.354 MeV for the He3/De burns. So (213/31) X (8.68/18.354) = 3.2 times more energy from the same sized fuel storage tank of the B11 vs He3. Not even counting the fact that B11 could be stored as a solid at room temperature vs the bulkier cryogenic storage He3 would need even in space. I am ignoring the Hydrogen reactant for B11 vs the De reactant of He3 since both could be stored as water/ammonia/methane etc and recovered from such in metered amounts as needed. Difference in effective energy for the same sized storage container might prove significant at some point in space drive applications; of course a tank filled with B11 would be heavier than the same sized tank full of He3.

Skipjack
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Re: Z-Pinch Renaissance

Postby Skipjack » Fri Nov 01, 2019 1:19 am

At the amounts of fuel that we are talking about here, tankage mass is of secondary concern, I think. For a mass mission at 0.1g (near) constant acceleration/deceleration, I calculated 70 tonnes, though actually it would be less since you lose fuel mass over time. So probably more like 50 tonnes. Tankage mass for this is really small. Maybe 4 tonnes, or so. Trip times would be so short that worries about keeping the fuels cool is IMHO not really necessary. We are talking trip times of days to Mars.
However, Q and the resulting Isp and engine mass do matter. Also a PB11 reactor would have to run even hotter than the D+He3 version and power supplies would have to be much bigger. The latter by itself (not even counting the bigger reactor core and lower engine efficiency) would probably already outweigh the benefits from the more dense Boron.


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