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
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.
