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

[Elmar Moelzer]

Anybody else excited about John Slough's work and the fact that he got a NIAC phase 2 award?
To bad we will have to wait for two years to see the final results.
In case you dont know what I am talking about, here is a recent paper on the topic:
http://msnwllc.com/Papers/FDR_JPC_2012.pdf
This thing should have a pretty decent thrust too, a 30 day trip to mars sure sounds exciting!
Been a long time admirer of Sloughs work, also in the area of fusion for power generation (fusion engine). So the more publicity and traction his work gets, the better.

[RobLynn]

I am also a big fan of his FRC Fusion engine at Helion http://helionenergy.com/?page_id=164
Has some great attributes for an aerospace fusion power source, avoiding many first wall problems due to pulsed and rapidly translating plasma toroids with a very elegant method for efficient heating/compression and ignition by accelerating plasma rings through a constricting section.  It also provides a potential means for inductively extracting some power in an efficient and compact direct conversion system as the plasma rings re-expands through the tapered sections.

His fusion engine is long and slender and would fit well into rockets for launch into space, and has potential to fire the resulting plasma out of a magnetic nozzle at one end to operate as a fusion rocket.  It would also fit into a plane fuselage nicely.

It's a real pity that it isn't funded to the tune of a few million per year (like Polywell) instead of the multi billion dollar fusion white elephants like ITER and NIF that have no hope of ever being economic.  Seems that the collected influence of backers of big fusion projects prevent public funds from going to novel and potentially more economic alternatives, though a few like General Fusion and Tri-Alpha have managed to get private backing.

[Elmar Moelzer]

Yeah, totally agree. Tri Alpha recently released some encouraging results and some of their plans. We will see how well these work out. They are a lot more ambitious than Slough, since they want to got for PB11.

[Elmar Moelzer]

Here is a video capture of the NIAC 2012 Fall conference with some more info on the fusion driven rocket.

Btw, the live stream question was asked by me
Wished I had seen John Slough speak, been a long time admirier. I think that Anthony Pancotti was an excellent presenter though, very eloquent speaker, very clear, especially compared to some of the other presenters that day.

[AnimatorRob]

I'll attempt to ask an intelligent question but the particulars of fusion physics is well outside my areas of expertise. Anyway, having read the above paper and watched the video I understand that the reaction and therefor the thrust, is non-continuous i.e. pulses. This leads me to two related questions: How are the lithium liners replaced after each pulse, and how rapidly could these pulses be fired?
Assuming I am correct that this engine produces thrust in pulses, wont it vibrate the bejesus out of the vehicle and everyone in it? 

[Elmar Moelzer]

That is the same question that I asked during the session. They answer it towards the end of the video.
They say that they are aiming for .1 Hz repetition rate (one shot every 10 secs). With that much time, there are various ways to replace the liners, e.g. via spraying them on. We are not talking a lot of thrust here, so the pulse wont shake things up that much. The Isp is very high though and the thrust is high compared to SEP.

[john smith 19]

That is the same question that I asked during the session. They answer it towards the end of the video.
They say that they are aiming for .1 Hz repetition rate (one shot every 10 secs). With that much time, there are various ways to replace the liners, e.g. via spraying them on. We are not talking a lot of thrust here, so the pulse wont shake things up that much. The Isp is very high though and the thrust is high compared to SEP.

So what are the deliverables on this funding? Personally a unit that sat on a desk top and fired into a vacuum chamber with measurable results would beat the pants off another report.

[Elmar Moelzer]

That is the same question that I asked during the session. They answer it towards the end of the video.
They say that they are aiming for .1 Hz repetition rate (one shot every 10 secs). With that much time, there are various ways to replace the liners, e.g. via spraying them on. We are not talking a lot of thrust here, so the pulse wont shake things up that much. The Isp is very high though and the thrust is high compared to SEP.

So what are the deliverables on this funding? Personally a unit that sat on a desk top and fired into a vacuum chamber with measurable results would beat the pants off another report.

According to the video, they will build a even technology demonstrator engine (single shot operation only, IIRC).
That is break even fusion!
Their ETA for that is 1.5 years. The final report on their results from the tests with this device is planned for two years from now, IIRC.

[john smith 19]

According to the video, they will build a even technology demonstrator engine (single shot operation only, IIRC).
That is break even fusion!
Their ETA for that is 1.5 years. The final report on their results from the tests with this device is planned for two years from now, IIRC.

Now that is exciting. This should be very instructive. Break even in one step is bold.

[simonbp]

Yes, but remember that's a thermal engine, so they only need to reach thermal break even to produce usable thrust. An electrical generating station needs electrical break even, which is the tricky part, as a lot of the fusion energy can't easily be converted to electrical power.

JET (next door to Reaction Engines, IIRC) did get very close to thermal break even (Q~0.7) back in the 1990s, and that was with constant power rather than pulsed. So, it's not ridiculous that Slough could get to thermal break even without too complicated a setup.

http://en.wikipedia.org/wiki/Joint_European_Torus

Note that Slough's concepts tend to still have solar arrays on them to provide the ignition energy for the fusion rocket.

[Elmar Moelzer]

Yes, but remember that's a thermal engine, so they only need to reach thermal break even to produce usable thrust. An electrical generating station needs electrical break even, which is the tricky part, as a lot of the fusion energy can't easily be converted to electrical power.

JET (next door to Reaction Engines, IIRC) did get very close to thermal break even (Q~0.7) back in the 1990s, and that was with constant power rather than pulsed. So, it's not ridiculous that Slough could get to thermal break even without too complicated a setup.

http://en.wikipedia.org/wiki/Joint_European_Torus

Note that Slough's concepts tend to still have solar arrays on them to provide the ignition energy for the fusion rocket.

Yes it is thermal break even, which has not been achieved yet by any other device either. They are planning to get quite a bit over break even with their engine, but the initial test article funded with the phase 2 money will only try for break even. They would indeed still need solar panels to power that engine, though I think that they were planning to generate just enough electricity from it to self power the vehicle at some point in the future.
Yes, I do remember JET very well. I was still a teenager, when a friend and hiking comrade of mine who was working there told me about their achievement. He is now the leader of the design team at ITER.

[john smith 19]

Yes it is thermal break even, which has not been achieved yet by any other device either. They are planning to get quite a bit over break even with their engine, but the initial test article funded with the phase 2 money will only try for break even.

I think it's important to keep in mind that for this application if that's sufficient to get the job done then that's fine. I'll hope they are careful in setting their margins for the various elements of their system so they have a high probability of success.

They would indeed still need solar panels to power that engine, though I think that they were planning to generate just enough electricity from it to self power the vehicle at some point in the future.
Yes, I do remember JET very well. I was still a teenager, when a friend and hiking comrade of mine who was working there told me about their achievement. He is now the leader of the design team at ITER.

PV arrays appear to be the pragmatic solution to generating the "firing pulse" needed to give the thrust. Following the REL model I'd hope they would design in the elements needed to run power collection into the test machine, ready for the next phase of testing, but they concentrate on the core task. As always time will tell.

[Elmar Moelzer]

They have actually designed the entire vehicle too (focusing on propulsion elements with generic "payload" and "structure").
They are quite considerate.

[john smith 19]

They have actually designed the entire vehicle too (focusing on propulsion elements with generic "payload" and "structure").
They are quite considerate.

It's good to have an overall goal so that when you come to a tricky choice you can ask "Which option gets me to my end goal better?" But with the timescale and what looks to be limited funds I hope they focus on the core essentials.

Sometimes one sub unit at full size is better than trying to scale down the whole system (some of whose parts might be quite small to begin with). That's just an observation from the REL pre-cooler development work, but it did eliminate scaling effects and lets you use the data to drive the next stage of design directly.

I think this could be as big as the first time something close to an Xray laser was demonstrated on a laboratory table top without a nuclear bomb to trigger it.

[Elmar Moelzer]

They have actually designed the entire vehicle too (focusing on propulsion elements with generic "payload" and "structure").
They are quite considerate.

It's good to have an overall goal so that when you come to a tricky choice you can ask "Which option gets me to my end goal better?" But with the timescale and what looks to be limited funds I hope they focus on the core essentials.

Sometimes one sub unit at full size is better than trying to scale down the whole system (some of whose parts might be quite small to begin with). That's just an observation from the REL pre-cooler development work, but it did eliminate scaling effects and lets you use the data to drive the next stage of design directly.

I think this could be as big as the first time something close to an Xray laser was demonstrated on a laboratory table top without a nuclear bomb to trigger it.

Oh, they are focusing on the essentials. E.g. from what I understand, they are currently not concerned with things like automated replacement of the plasma liner, pulse rate, compact, lightweight power supplies, etc. These things are part of their concept, but AFAIK they are not part of the work done with the phase 2 funding. The funding is not exactly huge.

[john smith 19]

Oh, they are focusing on the essentials. E.g. from what I understand, they are currently not concerned with things like automated replacement of the plasma liner, pulse rate, compact, lightweight power supplies, etc. These things are part of their concept, but AFAIK they are not part of the work done with the phase 2 funding.

That sounds very sensible and pragmatic.

The funding is not exactly huge.

And this is why it sounds very sensible and pragmatic.

If they can get the performance they are hoping for (and at this point I think hope is about as high as you can put it) 1 test firing a day would be impressive. In some ways this looks like pretty unknown territory to me and I think they'll be a lot of analysis between test runs, but that's just an impression.

[Elmar Moelzer]

From what I remember from the video, their main goal is to demonstrate that it can be done and that they can achieve break even. Basically a proof of concept. I think that even that would be quite ground breaking.

[adrianwyard]

I'm still unclear on one question of scale: How big are these Lithium liner components? They are sometimes referred to as foils, potentially 'painted' on to the driver coils for each pulse - a total of 370 g is referenced. That's quite a lot of paint. The papers go on to mention an ideal Li shell diameter of around 5 centimeters - that size being preferred for neutron absorption. If so, the liner pieces are quite large.

If I understand correctly, the resulting rocket needs to precisely assemble a thin 5 cm shell of Lithium, from these components it has accelerated toward the D-T plasmoid at 3 km/s. And do this every ten seconds... Isn't that very difficult to do with absolute precision and reliability? My guess is that if something in the setup of the pulse was not perfectly symmetrical you'd blow the nozzle to pieces as the liner pieces shot through it... Maybe the magnetic fields are strong enough to eject a misfire, assuming it is all plasma by that point...

But regardless, it's still very interesting work. (I've always had a soft spot for fusion projects - as a small boy I took a tour around the Joint European Torus facility when it was being constructed. Very impressive.)

I'm curious if the VASIMR critics think this is less or more realistic!

http://msnwllc.com/Papers/FDR_JPC_2012.pdf

[Elmar Moelzer]

I'm still unclear on one question of scale: How big are these Lithium liner components? They are sometimes referred to as foils, potentially 'painted' on to the driver coils for each pulse - a total of 370 g is referenced. That's quite a lot of paint. The papers go on to mention an ideal Li shell diameter of around 5 centimeters - that size being preferred for neutron absorption. If so, the liner pieces are quite large.

If I understand correctly, the resulting rocket needs to precisely assemble a thin 5 cm shell of Lithium, from these components it has accelerated toward the D-T plasmoid at 3 km/s. And do this every ten seconds... Isn't that very difficult to do with absolute precision and reliability? My guess is that if something in the setup of the pulse was not perfectly symmetrical you'd blow the nozzle to pieces as the liner pieces shot through it... Maybe the magnetic fields are strong enough to eject a misfire, assuming it is all plasma by that point...

But regardless, it's still very interesting work. (I've always had a soft spot for fusion projects - as a small boy I took a tour around the Joint European Torus facility when it was being constructed. Very impressive.)

I'm curious if the VASIMR critics think this is less or more realistic!

http://msnwllc.com/Papers/FDR_JPC_2012.pdf

I agree, assembling the lithium liner seems to be rather complex and I think they will have their share of fun with that. It seems to be trivial compared to achieving high fusion gains though.

[adrianwyard]

True enough. If they can actually get >breakeven fusion for ~300 kW (3x ISS), then that's quite an achievement regardless of specific rocket applications.