Advanced Electric Propulsion System successfullu ttested.

kbd512 · 2017-07-19 11:27:18

Oldfart1939,

We're nowhere close to having a workable fusion reaction system to produce electrical power, but the FDR does not produce a single kilowatt of electrical power from the fusion reaction and the process is an incredibly brief pulse versus continuous operation. For all intents and purposes, the FDR is a fusion powered pulse jet system.

MSNW LLC has already generated thrust by collapsing an aluminum foil liner around a D-T pellet. The neutron radiation is a problem, but the liner captures most of the neutron radiation produced and the Lithium fuel is a pretty good neutron absorber. The supersonic foil liner compression was proven to produce jet power from D-T fusion back in 2013. I guess we can pretend that the results that Dr. Slough's team obtained through actual experimentation weren't what they were, but NASA has provided funding for this project every year since 2012, IIRC.

The FDR is mostly an engineering problem at this point, meaning integration of the chamber / nozzle / foil extruder, how many kW/kg for the solar arrays, and how many kJ/kg for the super capacitors.

Antius · 2017-07-19 14:30:01

Even if it works, fusion is unlikely to be economic here on Earth. Power density would be about an order of magnitude lower than a PWR. The device is basically a shell of rare Earth superconducting magnets. Most of the energy comes out as fast neutrons, which irradiate the reactor walls, superconductors and everything else, requiring that the whole thing be stripped down by robots every 18 months. To generate fresh fuel, cooling must be accomplished using a liquid lithium blanket. Radioactive tritium must then be chemically separated from the molten lithium. Does this sound like a device that will ever provide cheap and abundant energy?

Last edited by Antius (2017-07-19 14:32:32)

kbd512 · 2017-07-20 01:16:24

Antius,

As it turns out, replicating what goes on in a star without replicating the conditions inside a star is really difficult. Who knew? Fortunately, FDR isn't trying to achieve any sort of continuous fusion reaction and that's a good thing (in this case). As previously stated, it's just a powerful pulse jet system that uses super-heated plasma to produce thrust. No electrical power generation from fusion whatsoever, just thrust.

Incidentally, some smart kids (actually, they're my age or a little younger) from MIT figured out how to absorb neutrons without killing the containment. REBCO is seriously strong stuff (for dealing with mechanical loads and neutron radiation, that is), as most high grade stainless steels generally are. ITER doesn't use REBCO, so I foresee coil / containment longevity problems, but there's no chance of a redesign at this point.

ITER's design will never be practical for electrical power production, but MIT's device should be since it solves the electromagnet power / longevity, fuel blanket, and magnetic field stability problems (with substantially high electromagnetic pressures with lower input power). It would seem that plasma stability is the most intractable problem that all previous experiments had. The electromagnets are just not powerful / efficient enough, thus the very large minimum size required to get more power out than was put in. Like fission reactors, fusion reactors are subject to process-specific scaling laws and steady state operational issues.

SpaceNut · 2017-07-20 17:22:12

So this is a regenerative magnetic field bubble...
THRESHOLD BUBBLE CHAMBER FOR MEASUREMENT OF KNOCK-ON DT NEUTRON TAILS FROM MAGNETIC AND INERTIAL CONFINEMENT EXPERIMENTS

Dynamo design with regenerative back mmf

So Lockheed Martin Says It's Made a Big Advance in Nuclear Fusion...

Antius · 2017-07-21 05:50:12

I will believe it when I see it:
https://www.nextbigfuture.com/2017/05/l … plans.html

Oldfart1939 · 2017-07-21 07:22:32

I am highly skeptical of all these "advanced propulsion systems." Yes, they indicate some promise, but certainly not in my lifetime or even the lifetimes of our younger participants in this forum. I'm just guessing, but until compact nuclear space rated reactors become available, this remains science fiction to me...

GW Johnson · 2017-07-21 09:45:08

As I have said before, there's light years of distance to cover between a successful feasibility demonstration test of a new concept, and having something actually ready for general application. Ugly (and very unpopular) little fact of life, but there it is.

The way to deal successfully with it is to split your R&D efforts into two types. One pursues these ideas, trying to cover those light years between feasibility and practicality. The other is to pull only ready-to-apply items together into a vehicle design and check that out; that's how you go fly.

Mix the supporting technology development with the vehicle design/checkout activity on the same contract, and the odds are heavily in favor of you never flying anything. US DOD gave up on ramjet and tried to leapfrog to scramjet, but scramjet wasn't, and still isn't, ready to apply.

That's why the US is still flying subsonic cruise missiles, while most of its adversaries now have supersonic ramjet cruise missile anti-ship weapons. Stupidity incarnate.

You have to do both types of R&D or you never get any progress. But dare not to mix them!

GW

Last edited by GW Johnson (2017-07-21 09:50:56)

Oldfart1939 · 2017-07-21 11:52:05

GW Johnson wrote:

As I have said before, there's light years of distance to cover between a successful feasibility demonstration test of a new concept, and having something actually ready for general application. Ugly (and very unpopular) little fact of life, but there it is.
The way to deal successfully with it is to split your R&D efforts into two types. One pursues these ideas, trying to cover those light years between feasibility and practicality. The other is to pull only ready-to-apply items together into a vehicle design and check that out; that's how you go fly.
You have to do both types of R&D or you never get any progress. But dare not to mix them!
GW

That seems the be the NASA model, though!

kbd512 · 2017-07-21 15:46:07

Oldfart1939 and GW,

I realize that a successful concept demonstration and working propulsion unit are two different animals entirely, but if the basic concept was proven to work as intended years ago, is there any reason to not move forward with it?

Everyone wants high payload mass fraction, high speciic impulse, and high thrust. You're never going to get all three with chemical (ever), nuclear thermal (at least not until you get into exotic liquid or gas core technologies), or ion (unless someone out there has a GW class reactor that produces 1kW/kg that they'd like to sell to us) propulsion. This is the only system I've seen that stays within the realm of conventional physics and provides all three "nice to have's" from the rocket scientist's wish list.

In order to get something better than what we have, you have to try something new. That's all there is to it. If we did have it, there's no reason why we couldn't mount a mission in ten years time.

Oldfart1939 · 2017-07-21 17:20:25

GW Johnson wrote:

The way to deal successfully with it is to split your R&D efforts into two types. One pursues these ideas, trying to cover those light years between feasibility and practicality. The other is to pull only ready-to-apply items together into a vehicle design and check that out; that's how you go fly.
Mix the supporting technology development with the vehicle design/checkout activity on the same contract, and the odds are heavily in favor of you never flying anything. US DOD gave up on ramjet and tried to leapfrog to scramjet, but scramjet wasn't, and still isn't, ready to apply.
GW

I never suggested we should not do the research--it should be done separate from the hardware boys.

Last edited by Oldfart1939 (2017-07-21 17:21:34)

knightdepaix · 2017-07-29 10:35:33

Maybe I am asking non-sensible question... Why can't a D-D fusion be used so neutrons emission is eliminated?

RobertDyck · 2017-07-29 13:16:58

D-D fusion requires higher energy to get fusion to happen. That means more pressure and heat. And D-D releases less energy than D-T or D-He3. And roughly 40% of the time, D-D becomes T plus a proton, the rest of time it becomes He3 plus a neutron. So one point is that with D-D, neutrons emissions are not eliminated. In a nuclear reactor, fusion products will be contained, so D-D fusion produces T and He3 for the other two reactions. In a D-D reactor, D-D is the primary reaction, D-T and D-He3 are secondary, but more energy is produced from these secondary reactions than the primary. Total of all reactions produces between 90% and 91% as much energy per mass of fuel as D-He3. Considering D occurs in every drop of water on Earth, but He3 is so rare it would have to be mined on the Moon, a commercial power plan would never use D-He3. A commercial power plant on Earth would use D-D. Initiating fusion is difficult because it requires so much heat and pressure. However, in a D-D reactor, since D-T reaction is one of the secondary reactions, and since that reaction has the lowest ignition energy, you would start with that. So a reactor would use D-T to initiate fusion, then use energy from fusion to raise heat and pressure to the point where D-D can ignite. A heavy water fission power plant produces T as a waste product; that could be used to initiate fusion. But once started, a fusion power plant will produce all it's own T and He3. If when shut down, it will retain some T and He3 so they can be used to restart.

For a fusion thruster, expansion of fusion products is directly used for thrust. Fusion products don't stick around long enough for a second reaction.

D-D → T + p+ (50%)
D-D → He3 + n° (50%)
D-T → He4 + n°
D-He3 → He4 + p+

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#26 2017-07-19 11:27:18

Re: Advanced Electric Propulsion System successfullu ttested.

#27 2017-07-19 14:30:01

Re: Advanced Electric Propulsion System successfullu ttested.

#28 2017-07-20 01:16:24

Re: Advanced Electric Propulsion System successfullu ttested.

#29 2017-07-20 17:22:12

Re: Advanced Electric Propulsion System successfullu ttested.

#30 2017-07-21 05:50:12

Re: Advanced Electric Propulsion System successfullu ttested.

#31 2017-07-21 07:22:32

Re: Advanced Electric Propulsion System successfullu ttested.

#32 2017-07-21 09:45:08

Re: Advanced Electric Propulsion System successfullu ttested.

#33 2017-07-21 11:52:05

Re: Advanced Electric Propulsion System successfullu ttested.

#34 2017-07-21 15:46:07

Re: Advanced Electric Propulsion System successfullu ttested.

#35 2017-07-21 17:20:25

Re: Advanced Electric Propulsion System successfullu ttested.

#36 2017-07-29 10:35:33

Re: Advanced Electric Propulsion System successfullu ttested.

#37 2017-07-29 13:16:58

Re: Advanced Electric Propulsion System successfullu ttested.

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