FRC + Imploding Plasma Liner Fusion for the Fusion Rocket (NIAC2)

[Elmar Moelzer]

I think that any radioactive lithium, Tritium, helium or other isotopes that might eventually make it to earth will be spread over such a large area during reentry that the radioactivity would completely go under in the background radiation.

[aero]

I'm not convinced that the exhaust products would return to earth, except of course when the exhaust is pointed directly toward earth. But that is an uncommon situation.

The exhaust velocity is much, much higher than earth escape velocity and even when the rocket is traveling outward at escape velocity, the exhaust will be traveling in the other direction at much higher than escape velocity. Why would the exhaust products, radioactive or not, stop at earth?

Remember, these products must be electrically neutral, else the whole scheme fails.

[eriblo]

Remember, these products must be electrically neutral, else the whole scheme fails.

Well, the exhaust is certainly neutral but I highly doubt that the products in the plasma are - would be hard to use a magnetic nozzle in that case

Regarding the fallout: If only D, T, Li and neutrons are involved I don't think there will be much long-lived radioactivity to consider. Most of the isotopes produced are either stable or have half-lives < 1s. My layman guess is that unburnt tritium would be a large (the largest?) contributor and the total amount is still in the noise compared to the "natural" amount (mostly from nuclear testing).
If anybody feels competent to put numbers on this please do 

Another thing to remember: while most of their energy is deposited in the lithium only a small portion of the neutrons produced are absorbed by it, further reducing the amount of radioactivity in the exhaust.

[MP99]

boron-11 is apparently a pretty good neutron multiplier

Hmm, aren't the wiffle-ball guys hoping that p-b11 will be essentially aneutronic?

Is that just because there are no neutrons to be multiplied in the first place?

cheers, Martin

[Elmar Moelzer]

I get the feeling that this is only being pimped out as a propulsion concept to get funding earmarked for space technology.

IIRC, he has tried in the past to get space money for just the plasmoid generator as a sort of pulsed ion engine, though obviously he was more interested in developing it for fusion.

In the initially linked paper ( http://msnwllc.com/Papers/FDR_JPC_2012.pdf ), it talks about an "expected gain of 40" and "an extremely low gain estimate of 20".  So they're talking about a net energy fusion system getting at least 20 times more energy out than the energy they're putting in.

If this works, a somewhat-lower-Isp, somewhat-higher-thrust ion engine is just about the least significant and most challenging application of the technology.  It would be a revolutionary clean energy source or at least a weapons proliferation horror long before it could be made light and reliable enough to be flyable.

I have talked to David Kirtley and I do not think they are being dishonest at all. MSNW has a long history of space propulsion research as well as fusion research. Just look at their ELF thruster!
On the application of the technology for energy:
This has been discussed before and if you read my earlier post, where I quoted from a conversation I had with David Kirtley, you will see that they do not consider this as good a choice for that. They would rather see funding for their Helion fusion reactor, which uses a different, much simpler principle that is more more likely to result in an economic reactor for power generation. Finally, they are hoping to use just Deuterium in the FDR, which should reduce the neutrons quite a bit (but probably also the gain). Anyway, we probably wont have to wait too long for results from them.

[Elmar Moelzer]

That is essentially correct, but from what I understand, there will also be side reactions of fusion products also undergoing fusion and that will produce additional neutrons. You will probably get some D+D side reactions as well, resulting in more neutrons and also more Tritium which will also result in more neutrons. All of that will most likely contribute to your neutron budget.

The reaction rate of D+D will be very small compared to D+T and will not help the neutron economy in any meaningful way. My understanding is that something like Lead will be used as a neutron multiplier. The high energy neutrons will collide with lead nuclei and kick out multiple neutrons.

 Even so making enough tritium to replace that which is burned or lost is problematic even in a ground based fusion machine because of neutron losses in non-breeding parts of the machine. If the neutrons are slowed down before they hit the lead the neutron amplification will drop off, and below a certain energy go to 0.

Other options are beryllium, isotopically-tailored boron (boron-10 is a notorious neutron gobbler, boron-11 is apparently a pretty good neutron multiplier), isotopically-tailored lithium (lithium-7 doesn't really multiply neutrons, but can give you tritium from high-energy neutrons without consuming the neutron, so it can help bias things toward net tritium production).

But the absolute best multiplier would be uranium.  Fusion neutrons are great for inducing U238 to fission, and even thermal neutrons can be multiplied with U235.  Even when it absorbs neutrons, that just makes it a better multiplier in the future due to plutonium content.  On top of that, it gives you oodles of extra energy, making far easier to achieve breakeven.

Pretty much any fusion concept will be easier to make work with D-T fusion, any D-T fusion system will be easier to make work with uranium blankets, and with uranium blankets, it breeds plutonium.

Which is something to bear in mind the next time someone tells you how wonderful and peaceful and harmless fusion power technology is.

Read a few pages back, I quoted David Kirtley on his thoughts about fusion fission hybrids. He would rather suggest thorium than uranium.
Proliferation is a non issue now anyway, since they can do enrichments much cheaper with lasers now. Besides, I would not sacrifice the energy future of mankind for a non issue like proliferation.

[Elmar Moelzer]

Their ELF thruster was what I was referring to as their "sort of pulsed ion engine".  They wanted to research plasmoids for fusion, so they pimped it out as a propulsion system by itself to divert funding earmarked for propulsion into their fusion research.

I'm not sure I'd go so far as to call it "dishonest", but it isn't something you can simply take at face value, either.  Their net power fusion aspirations are much more significant than this specific application (the fusion drive, not the ELF) which requires net power fusion to matter.

Incidentally, affordable net power D-D fusion would be an absolute proliferation nightmare.  No neutrons required, many neutrons put out.  A perfect bomb factory.

Nonsense, they ELF thruster development has been ongoing for quite a while. They have built several devices and tested them in a wide range of environments and fuels. The device is actually performing really well and they can handle a lot more power than ion engines and even than VASIMIR. They are now working on making them smaller and work with less input power.
They have also done research in the electromagnetic plasmoid thruster and this year on magnetoshells for aerocapture. Claiming that they are not serious about their propulsion research contradicts the number of researchers working on this at MSNW LLC and the sginificant amount of publications they have released on the topic.

Again, the fusion driven rocket is not an ideal device for net power generation. Their Helion fusion engine is much better suited for that. This is quite obvious and David Kirtley from MSNW recently confirmed that to me.
So I dont know what you are getting at. And please leave me allone with the nuclear bomb boogey man. It is completely irrelevant.

[Elmar Moelzer]

the fusion driven rocket is not an ideal device for net power generation

It requires a large net power output to meaningfully function, not just a thin margin, but many times more power out than in.  Perhaps this is not electrical power, but it's in hot, fast-moving plasma, and with the gain range they're talking about, it would be utterly trivial to adapt to highly efficient electrical power generation.

In any case, the fact of net fusion power is obviously far more significant than this application which presupposes it.

And nuclear weapon proliferation is not a "boogey man", it is an existential threat and a key consideration for any nuclear technology, and to casually dismiss it is grossly irresponsible.

Again, dont take my word for it, take theirs! I posted an excerpt of a conversation I had with David Kirtley a few pages back.

And I refuse to let minor concerns like proliferation to stand in the way of progress. In fact, I believe, that if we do not manage to solve the energy problem (to which nuclear fusion is the best solution), a lot more people will die than what could be killed by some rogue state with a nuke or two. It is a virtual problem, not even a real one. Fusion or not, those countries that really want to have a nuke, will find a way. Luckily these crazies are few. The lack of energy is the real problem. People die because of it every day, right now.
Unlimited clean and cheap energy is the requirement for unlimited economic growth. Now the first fusion reactors might not quite provide us with that, but they will bring us closer.
Wealth is also a good way to reduce the power of insane leaders over their people. People that are well fed, well educated and well situated are less likely to follow some (luckily rare) insane leader into a suicidal nuclear war. They have too much to loose.

[Elmar Moelzer]

Again, dont take my word for it, take theirs! I posted an excerpt of a conversation I had with David Kirtley a few pages back.

Okay, sure.

In our view, the most realistic concept is to enrich thorium with a G<1 fusion neutron source and then move it next door to the thorium reactor for startup.

Roving bomb factory.  Splendid.

The magnetic compression method is the primary technical difference; in the rocket it is accomplished with the liner, which becomes the propellant, coolant, and neutron blanket.  In Helion’s Fusion Engine it is done with magnetic fields which allows for direct electrical energy recovery and non-destructive, higher rep rate, operation.  Also, where lithium plasma is an advantage in the rocket, handling that exhaust in an energy reactor (and the reprocessing) would be quite difficult, expensive, and a major engineering challenge.

Okay, so extracting electrical power from a lithium plasma jet is "a major engineering challenge", but developing a second net power fusion reactor to operate on different principles is not?

This is just silly.  Squirt it into water.  Bam!  Boiling water, right there.  Inefficient?  Sure, relatively speaking, but with 20+ gain from your fusion system (which is a bare minimum for it to be useful), it would have to be less than 5% efficient to fail to provide net electrical power.  And getting lithium out of water is just not that hard.  (digging your tritium out among all that protium would be slightly more inconvenient, but still nothing which poses any dramatic difficulty, and this is just a trivial existence proof for power generation anyway)

If you say:

1) Fund me.
2)
3) Here's your neat deep space propulsion, so you can fly to Mars or something.

...and step 2 is "net power fusion", step 3 doesn't matter.  It's really:

1) Fund me.
2) Net power fusion.
3) Who cares?  I've done net power fusion!  I'm a billionaire with a Nobel Prize and I can do whatever I want.

Whatever he says, I doubt this has escaped his notice.

They already have a quite well developed research reactor for their second concept that is intended for terretrial power. They are currently trying to get the funding for the full scale version via their spin off, Helion.
The matter is not to create A fusion reactor for power generation, but a reactor for ECONOMIC power generation. It has to be simple and cheap enough to compete with coal. Otherwise it is maybe good science, but wont solve the worlds energy problems.
The fact that it has to be economical is why ITER and NIF are IMHO dead ends. Even ITERs proponents say that "it might never lead to economic fusion reactors for power generation, but it is really good science"
The NIF will most likely not result in anything and was IMHO never meant to be anything else than a defense program.

[Elmar Moelzer]

They already have a quite well developed research reactor for their second concept that is intended for terretrial power. They are currently trying to get the funding for the full scale version via their spin off, Helion.

A "quite well developed research reactor" is one thing.  We've had fusors for decades.  Net power is another thing entirely.

Likewise, "trying to get the funding" is very different from "has the funding".  The first means "money-hungry" and "time on their hands", which explains why they are digging for space program money, instead of being fully occupied building their net power fusion reactor.

The fusion driven rocket does not have the funding to be fully developed either. They are doing a proof of concept, break even test series starting this summer.
Again, if you read my earlier post, you would see that they are still doing research on their net power reactor as well. The full scale reactor would need more funding, however. They are a research company with a focus on plasma science and fusion devices in two main areas of expertise. It is obviously not easy to get several 10s of millions of funding for a full scale reactor project. Sp they do whatever research projects in those areas that they can get funding for. Doing anything else would be stupid.
I do not quite get the attitude that you are expressing towards MSNW.  How can you have such a strong opinion about their intentions while (obviously) knowing so little about them and the work they are doing?

[Elmar Moelzer]

Well, I have been following their work for a very long time as well. Also, I do think that there was quite a bit of previously unpublished information in my earlier post. I still dont get what causes you to make the claims you are making about their intentions. It seems pretty baseless to me.

[Elmar Moelzer]

Well, I have been following their work for a very long time as well. Also, I do think that there was quite a bit of previously unpublished information in my earlier post. I still dont get what causes you to make the claims you are making about their intentions. It seems pretty baseless to me.

It's not really about their intentions.

If one step in the plan is, "develop net-power fusion", the following steps don't matter.  You're doing fusion research.

It's like saying you're working on human-equivalent AI for space probes, or a way to stop aging for interstellar voyages.  You can stop reading before you get to "for", what comes after the "for" is science fiction.

I dont see it that way. They do plasma physics. All of their projects are related to that. I dont see the contradiction.

[93143]

It's like saying you're working on human-equivalent AI for space probes, or a way to stop aging for interstellar voyages.  You can stop reading before you get to "for", what comes after the "for" is science fiction.

No, you can't, because this fusion drive is only good "for" space propulsion; it's not easy to make an economically viable power plant with.  It's not as bad as a bomb (though you can do that too, with underground detonations, some water, and a steam turbine - maybe get a giant magnetic nozzle involved somewhere?), but it's still a mess.  Essentially it is a bomb drive; the bombs aren't preassembled or self-contained (or fission-triggered), but they still make enough of a mess that the system is far from ideal for a power plant.

No one who knows what he's talking about questions the fact that net power can in principle be had from fusion.  It's not a Nobel-prize-in-physics achievement in itself; it doesn't prove anything fundamental.  And it certainly doesn't usher in a post-scarcity golden age all by itself.  What's important is the ability to do it at least as cheaply as existing forms of power generation.  Tokamak may never do that; certainly not for a while.  Laser inertial probably won't do that.  Polywell, Focus Fusion, that Skunk Works project, or various forms of FRC including General Fusion, Tri-Alpha and Helion's approaches are less certain (from my perspective) to achieve net power at all, but if they do they very well might do it cheaply enough to be useful.

On the other hand, it is true that net power from fusion has an image of unattainability.  If MSNW manage to blow past the threshold as easily as they claim they should be able to, it should shake up a lot of "savvy" investors and jaded naysayers.  So there's that...

It occurs to me that General Fusion is doing almost exactly the same thing as MSNW's fusion drive, except in a power-plant-friendly fashion.  Helion is doing almost exactly the same thing as General Fusion, but without the mechanical compression.  We shall see...

...

Please note that this fusion drive is actually vastly superior to an electric drive with equivalent performance for a very simple reason - its power requirements are far, far lower.  Even if you had a fusion reactor to put on board and power a VASIMR or ELF thruster, you wouldn't necessarily want to if this were available.  Even using a small (thermal) power plant to power a fusion thruster wouldn't be as good as just using an MHD power tap in the exhaust, because the latter doesn't require substantial radiators.

[cordwainer]

Talking about Polywell concepts has anything new regarding University of Illinois's concept for a "leaky polywell" helicon injection plasma rocket come up? I looks very promising in regards to creating a more energy efficient form of high thrust plasma propulsion. Even if Polywell never works as a fusion concept it seems like it may have use in other areas like particle colliders and electron beams.

Could you apply a liner approach to fission-fusion energy? Instead of using fusion reactions as a neutron amplifier for fission reactions could you use a fissionable liner around a fusionable core to create micro-fusion explosions?

[QuantumG]

Why not start a new thread.. preferably with links.

[Elmar Moelzer]

NextBigFuture has an update on the progress of MNSW LLC.
http://nextbigfuture.com/2013/09/roadmap-to-fusion-driven-rocket-with-90.html

I also got word from David Kirtley that they will present the results of the tests that are currently under way at MSNW LLC at the coming IEPC this October:
http://www.iepc2013.org/agenda
http://www.iepc2013.org/get?id=372
From all I have heard that is going to be quite interesting

[adrianwyard]

Here's a new animation from MSNW showing the whole spacecraft:



Some initial observations:

They appear to depict the liners being ejected from a dispenser toward the coils as one unit, which then somehow splits into three with each one ending up attached to the correct coil, which then collapses it. I'm scratching my head on the details here...

It shows 'propellant' storage in the form of spools of Lithium. Perhaps the raw liner material is cut and then welded to form continuous liners of the correct dimensions? For more see page 16 of the following:

www.iepc2013.org/get?id=372

It's a cool video, but to be honest it just makes the liner loading aspect seem even more troublesome than when we were guessing how it would work.

Edit: added reference to paper just presented at IEPC 2013.

[Elmar Moelzer]

Thanks for posting the update! I had not seen that yet!
I would not put too much emphasis on the liner loading problem. AFAIK, they are still evaluating several options and the animation may not be 100% exact on that aspect. They are still working on the fusion aspect. Once that is solved, the liner feeding should be trivial in comparison.

[adrianwyard]

I certainly agree the priority has to be demonstrating a successful single-shot ignition in lab conditions. Until that milestone is passed everything else is irrelevant.

But for that accomplishment to have relevance for in space propulsion they will also have to come up with a super-reliable loading mechanism. I worry all mechanisms will be prone to catastrophic failure due to the forces involved. e.g. Asymmetric liner compression could shred the engine (this might be caused by compression magnet timing/power failure or liner misalignment.) A failure on the plasmoid injector side would likely result in it being caked in vaporised Lithium if the liner compression was not stopped in time.

And if the failure were not catastrophic, but just a jam in the mechanism that unwinds the spools and assembles the liners, that could mean the end of the engine.

All that to say, qualifying this engine (principally the loading mechanism) will be trickier than other engines. I think you'd need to do it in space, and run a full mission duration or two. You could just fight all this with redundancy, i.e. have two or three engines, each with their own loading mechanism, but that's a hefty weight penalty.

[Elmar Moelzer]

Don't forget that the loading mechanism is not going to perform at insane repetition rates. We are talking one re -loading every 10 seconds here. So this is not a high performance part in any way. It seems that they have updated the layout of the driver coils to be more cylindrical. This makes the loading even simpler. If we cant make a mechanism like to work reliably, then it might be better to just quit that space business all together.