Using gravity to create a self sustaining thermonuclear reaction

Discuss how polywell fusion works; share theoretical questions and answers.

Moderators: tonybarry, MSimon

Post Reply
ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

I’ve been informed by a mad scientist that there is simply no way that high explosives could achieve thermonuclear fusion. I kind of wish I got a better analysis but I understand the skepticism. The only way it could be worse is if I proposed using tiny piezo electric ceramics as the driving mechanism.

We could play with all kinds of forces. Magnetic forces for making particles travel in loopty loos (this is the scientific term of course). And shoving them around with electrostatic forces. But it’s getting to the point that no matter how hard you squeeze an energetic plasma this way it just leaks all over the place sooner than later.

The mantis reactor can’t work because the energy isn’t quite good enough, an expert mad scientist says with hundreds of thousands of dollars worth of education. Besides, It would be loud, fatalistic and obnoxious, at best an experiment for the maddest types, weapons experts.

The elements of fusion energy: Lots of energy in a little space, for a long enough time to be interesting.

The NIF focuses about 2.15 mega joules of highly refined energy to a target about the size of a grain of sand. That isn’t even a kilogram worth of TNT going boom. But a laser has a far faster rise time and a terrific focus. I can see the appeal of giant lasers. I just don’t find the complexity and cost that appealing. Not to mention the near impossibility of harnessing the energy for anything useful. And the economics of it.. dang..

Mantis is not practical. The materials are wrong. It has a deeply antisocial aspect. And over all even if it worked, it’s pretty useless.
There is a force which works well without question and that is gravity. We have no way to magically create a gravity well. But that doesn’t mean we can’t borrow one we already have, the Earth’s.

Introducing Mantis II: a self sustaining fusion chain reactor
The receiver sphere has got to go. Resetting the machine like that is not going to be fun. The shrapnel is course and rough and gets everywhere. Instead, along with the bottom solid parabolic reflector, the top has one too. The wave travels back and forth between the mirrors. The driver of this machine is a dead drop solid iron weight about 100 meters in the air that weighs 268 metric tons. It falls on the piston and when it strikes it it is going 44.29 meters per second. To keep it from bouncing around a bit too much add a several ton neodymium or electromagnet below the structure. The piston, cylinder, parabolas, and linings are all made of non ferris materials (titanium and tungsten carbide preferably) The sudden stop transfers 263 megajoules to the top parabolic reflector. 263 mega joules are then focused with a gain of 10,000x to the focus where after considerable thermal losses (lets just for the sake of a story make the efficiency only 18%), the focus is only a little over a millimeter in diameter. That’s 46 mega joules in a volume of about 4 cubic mm. The specific heat of heavy water is 4.219 joules per gram. Using hyperphysics’ website and plugging 46 mega joules into this 46 milligrams of heavy water will raise it’s temperature to 238.8 million K. Add a little more weight, or make the tower a little higher to get the temperatures and densities you’d like. The first set of numbers I got were a little over a billion K which is probably overkill. I have no idea how dense the focus would be. It probably doesn’t hurt to have more rather than less.

The reason tritium is used in ITER and most other reactors is because its a lot easier to get anything to happen. I don’t have the reference handy but temperatures really need to be 2.5 times higher to get D+D reactions going at a rate high enough to be interesting.

So some of these nuclei will fuse and produce quite a bit of heat. One of the problems of D+T reactions is the most energetic products are neutrons which don’t easily interact with the fuel ingredients. It makes it incredibly tough to create a self sustaining reaction without extremely efficient secondary energy harvesting. Doing it thermally is a pure non starter. And always will be. But this is not entirely true of pure D+D reactions which produce quite a lot of helium 4 reactions (not purely so, as you know). So some of the products in this reactor will heat the core of the reactor producing secondary thermonuclear shockwaves which rattle around a few times before either 1. It dies out, or 2. it destroys the facility. For safety reasons it can only be partially self sustaining. But even if we only get 5 repeats within the shot the total energy release could be as high as 256 kilowatt hours. I’d suggest the way to harness this is to run it to a point where a pressure relief value blasts the core fuel into a turbine or heat exchanger. This is the Otto cylinder gone bonkers you see. It burns the fabric of the universe :mrgreen:

I don’t have the talent to design it. The numbers are soft and foggy, like any fusion experiment until it runs.

Costs would probably be reasonable besides hiring a dozen Phds and Masters level engineers. It would have similar costs and complications as making a high rise structure. You need turbines and heat exchangers and operators just like any other kind of stationary large scale engine. But you don’t need: Bleeding edge mega magnets, billion dollar lasers, 23 nations worth of cooperation, or petawatts worth of capacitor discharge banks.
The little green men are right. Use the force. The force of 268 tons of iron smashing a cylinder from 100 meters in the air. This is the most extreme you could ever get with any kind of cavitation scheme. If this can’t work absolutely no other device similar to it could ever work. So then, we may finally be able to shut this whole enterprise down with 1 or two decent counter arguments. I’m game for any you’d have.

As for investment I’d put a dollar into this. One out of about 600 million of them. I have a hunch it might be more interesting than doggy coins.

That’s all for this episode of fatalistic thought. Tune in next time when I think of something just slight better than terrible. :mrgreen:

ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

After consulting with others I have found that:

1. The engineering difficulty is too high.
2. Even if it did work as planned, the energy release would probably tear the whole thing to smithereens. (200 KG TNT equivalent after 5 productive reflective shockwaves)
3. Gravity is a ruse here I have to admit. It is the sudden stop that makes it work. It is inertia and acceleration that is the driver here.

ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

But a bad mind is a terrible thing to waste. I'm still on the case. Tomorrow I'll have the final answer.

ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

I just realized how stupid this approach is. 256 KG of TNT is easy to find in an old A bomb arsenal. And it is a heck of a lot harder to compress solid plutonium than it is water. And with a piston, well you'd need a pyrophyllite (pipestone) gasket and that is going to absorb a lot of the impact energy and slow it way way down. So the temperature is not there, nor is pressure, nor is confinement time. :(

Maybe there is something interesting in magnetic recombination. Lots of new stuff going on with it.

Oh well at least I didn't make a career or lose one over it.

Ivy Matt
Posts: 701
Joined: Sat May 01, 2010 6:43 am

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by Ivy Matt »

Interesting. Could this be interpreted as a refinement of the "elephant" idea?
Temperature, density, confinement time: pick any two.

ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

Ivy Matt wrote:
Fri Mar 19, 2021 6:40 am
Interesting. Could this be interpreted as a refinement of the "elephant" idea?
Certainly think so, after all the machine costs a lot more and is much more dangerous than an elephant.

Might need to get Lockheed on it.

ohiovr
Posts: 428
Joined: Mon Mar 02, 2009 6:36 pm
Contact:

Re: Using gravity to create a self sustaining thermonuclear reaction

Post by ohiovr »

Looks like radiation pressure for squeezing fuel is the way to go. I forgot about the supreme difficulty of keeping this kind of pressure under wraps with an open container. Albert Einstein might find the circulating fusion plasma enterprise an example of his pop psychology in action for much of the fusion research on going “Insanity is doing the same thing over and over and expecting different results.”. While I wonder if people like Stan Ulam would have cracked this nut by now. Radiation pressure is quite interesting (for some reason it hasn't been applied to thin plasmas). NIF is a valid approach (if a gigantic laser won't work perhaps a colossal one will). Others may be too I guess I'm a little jaded because I don't have a physics education good enough to appreciate some of the other ideas that have been floated and tried.

Sonofusion is a head scratcher now that I've looked into it more..

Post Reply