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

[Elmar Moelzer]

Yes, to clarify: they do not expect breakeven in the next round of NIAC testing.

Is there something like a NIAC3? I thought that after NIAC2, concepts have to get picked up for a NASA project in order to get further funding. I might be remembering this wrong though.

[adrianwyard]

They'll be fine: at the 48:00 point Pancotti says they received $500 million from the DOE! Sadly, this was a slip: the slide said only $5M.

As one of the questioners asked "if you're so smart, how come you ain't rich?" If they do get neutrons that show fusion is happening as predicted, I think they'll be able to find backers to take the research forward.

[Elmar Moelzer]

They'll be fine: at the 48:00 point Pancotti says they received $500 million from the DOE! Sadly, this was a slip: the slide said only $5M.

As one of the questioners asked "if you're so smart, how come you ain't rich?" If they do get neutrons that show fusion is happening as predicted, I think they'll be able to find backers to take the research forward.

They have several other, connected areas of research, some of them with funding from the DOE. Plus they got a NIAC phase 1 for their magnetic reentry concept. So they have steady funding. 
Personally, I have always been more interested in their fusion power concept, that they are aiming to commercialize with the spin off company Helion. They recently unveiled a new prototype for that one too.
I am sure they will be fine

[alexterrell]

It's a good introduction to their plans: enabling a DRA5 type Mars mission with fast transit times on one SLS launch (~130mT). I didn't notice any substantially new information until the Q&A.

Here are a couple of things I noted. Other may have more:

+ Pulse time is every 13 seconds. Crew can probably be shielded from this by active shock absorber (with an additional energy requirement that's not factored in now?).
+ Plan is still to form the liners on demand from spools.
+ Thus far they've been focused on refining and verifying the mechanics of liner compression and magnetic characteristics.
+ They're now turning to the fusion side, notably the neutronics.
+ They do not expect to achieve breakeven, but do expect neutrons (i.e. fusion.)
+ There's a chance they will need more complex liners (than just Li) to capture the high-energy neutrons, i.e. an additional layer of Beryllium.

I think they needn't worry about pulse time and liners for now. The important bit is to demonstrate fusion. The rest, as they say, is "just engineering".

The shock absorbers only need be a few metres long and will absorb a trivial amount of energy. It complicates spacecraft design a bit.

Why do they need to capture the high-energy neutrons?

Once this thing is up and running, what is the limitation on pulse rate? Why not 1 per second or more?

[eriblo]

Why do they need to capture the high-energy neutrons?

Because most of the energy is carried by them. Any energy not captured in the liners (propellant) is wasted and, making things even worse, a lot of it is instead going to be deposited in the structure resulting in more waste heat and larger radiators as well as radiation damage. They started to discuss this during the presentation Q&A but did unfortunately not have time to go into detail

Although it is probably preferred I don't know if they need to actually capture the neutrons (as opposed to their energy) - thermal neutrons are a lot less damaging and might be absorbed in a thin coating of a suitable absorber (such as boron).

EDIT: On the other hand, thermal in this case might still be quite energetic (i.e. "slow" neutrons). I can definitely see why they are looking closer at the neutronics...

[adrianwyard]

It occurred to me that a pulsed thrust design like the one envisaged in this thread is conceptually compatible with spinning the whole craft to create artificial gravity for the crew. I did some basic calculations using from descriptions of the spacecraft upthread and you get about 0.8 g at the crew level if you spin it to fire every 10 seconds. (I’m assuming about 20 m to the center of mass, and 70 kg for the crew).

For more on the spun AG aspect of the discussion, see this thread: http://forum.nasaspaceflight.com/index.php?topic=34426.0;all

But, it also occurred to me that having the spacecraft operate while spinning (i.e. under ‘gravity’) would have another benefit: the liner assembly and loading mechanism could be tested exhaustively and refined here on Earth. Gravity - artificial or otherwise - can be your friend: it makes moving parts magically fall into place, and/or stay put depending on how you arrange your mechanism and parts.

[cordwainer]

Better idea would be to have two propulsion units. One providing end over end spin and the other used for linear thrust that would be fired occasionally whenever it reaches the correct attitude within the path of it's tumble. This would allow for increased momentum and course correction along the vessels flight path.

[adrianwyard]

Sure, that's what I was trying to depict (in crude graphics, I'm afraid).

Take the craft depicted here:

...and spin it.

That's why the period is 10 seconds - so it's pointing the right way again when it's ready to fire the next pulse. Obviously you need to be able to fire that pulse at exactly the right time in order to keep going in the right direction.

You wouldn't need much propulsion at all to maintain rotation/orientation once it's up to speed; perhaps control moment gyros could do it.

[alexterrell]

Not sure I'd want the spin rate varying throughout the flight.

And spinning a space craft requires such negligible amounts of power, I'd rather not deal with the complexity of spinning my fusion engine, especially when I'm tring to position a plasmoid to within sub millimetre level precision.

Remember also the engine needs a rather large spring and dampner to absorb the acceleration over the impulse period.

[adrianwyard]

Why would the spin rate vary during the flight?

[Elmar Moelzer]

I think I have not posted this paper here yet. It is their presentation from last years IEPC. Links directly to a PDF:
http://www.iepc2013.org/get?id=372

Looks like they made some good progress there!

[maitri982]

Any news on this project?  Always seemed to have the most promise for near term space transportation beyond chemical or ion thrusters.

[morganism]

Next Big Future did a update report a while ago...

http://nextbigfuture.com/2014/07/helion-energy-plans-to-enable.html

[Elmar Moelzer]

Next Big Future did a update report a while ago...

http://nextbigfuture.com/2014/07/helion-energy-plans-to-enable.html

This is not the same technology. Helion Energy is a spin off, of MSNW, the company behind the Fusion Driven Rocket and a lot of the same people are involved, but the fusion engine Helion Energy develops uses a very different principle from the Fusion Driven Rocket.

[alexterrell]

Next Big Future did a update report a while ago...

http://nextbigfuture.com/2014/07/helion-energy-plans-to-enable.html

The article says its the only "demonstrated" fusion concept that ........

Have they actually achieved fusion in their tests? And any gain of greater than 1?

[Elmar Moelzer]

Next Big Future did a update report a while ago...

http://nextbigfuture.com/2014/07/helion-energy-plans-to-enable.html

The article says its the only "demonstrated" fusion concept that ........

Have they actually achieved fusion in their tests? And any gain of greater than 1?

Not yet. They had several prototypes, each demonstrating different aspects of what is required and they know that their scaling laws are correct.

[Joris]

And any gain of greater than 1?

No need. They are not trying to generate electricity. 

[Elmar Moelzer]

And any gain of greater than 1?

No need. They are not trying to generate electricity. 

Helion is for electricity generation, actually. That said, the FDR also will have a gain of greater than 1 (up to 500 is deemed possible).

[alexterrell]

I wish both projects well and hope for their success - we do need them, but if they claim:

the only "demonstrated" fusion concept

but haven't yet achieved fusion, it doesn't sound good.

[Elmar Moelzer]

I wish both projects well and hope for their success - we do need them, but if they claim:

the only "demonstrated" fusion concept

but haven't yet achieved fusion, it doesn't sound good.

They have achieved fusion, but not break even. There is a big difference. They have demonstrated all the elements of the Lawson criterion and the scaling in various prototypes. Fusion reactions usually get more efficient with scale (which is why tokamaks have been getting bigger and bigger and why ITER is so big). This is why they are confident that they have demonstrated their fusion concept sufficiently at a small scale to be sure that a larger device will indeed achieve a positive gain.