It’s not real clear what the OP meant. First is he asking about theory or engineering? And if we’re engineering, are we engineering an explosive weapon, or a long-running not-self-damaging powerplant?
But IMO @Chronos pretty well nailed it as I snipped it.
E=MC^2 defines the upper limit of what energy could be produced by fission or fusion if every bit of mass was converted to energy. Whether quickly or slowly.
The problem is we aren’t going to invent a machine that can convert every single subatomic particle of the “fuel” into energy. So efficiency matters hugely, like multiple orders of magnitude hugely.
One hell of a lot of engineering has gone into weapons. And lots into powerplants. Each still have really shitty efficiencies albeit in very different ways for very different reasons. The shitty efficiency percentages are tolerable only because E=MC^2 gives a very big number for total potential conversion, so even grabbing a couple percent of that is still a big number.
Well, that depends on what you mean by “efficiency”. Is a fully-efficient nuclear reaction one where every uranium atom splits? Even if you do that, you lose only a small fraction of the mass of the uranium: The products have well over 99% of the mass of the original.
My point only was that E=mc^2 is a very loose upper bound for any practical bomb/reactor. Precisely because, as you say, even reacting 100% of the uranium atoms once each is still only converting a trivial fraction of the available m into E.
I think you need an antimatter reaction to pull off 100% conversion.
We have some antimatter on earth but not a lot. Often cited as the most expensive “thing” measured by mass on earth…by a long shot. We won’t be making antimatter bombs any time soon (thankfully).
Even at that, ~50% is lost to neutrinos. Even by the standards of sci-fi engineering magic, that energy is lost for good. It wouldn’t meaningfully add to a bomb’s explosive power, let alone a reactor’s efficiency.
Oh, it’s still a lot of energy, no doubt. It just means that you need perhaps a gram of antimatter to equal Hiroshima rather than half a gram. Gamma rays carry away a significant amount of energy as well, but I don’t know how well their spectrum gets absorbed by typical matter. Probably some is lost to space or heats things deep underground.
And a small older sports car to carry the flux capacitor (and its cooling system) that provides the containment for that gram of antimatter inside the pen.
Answering myself: none at all. Now I remember that particle energy is linearly related to absolute temperature by Bolzmann’s constant, we see that even at 10,000K we get only on the order of 10 electronvolts for each particle. At least 3 orders of magnitude below the energy needed to overcome the coulomb repulsion between charged nucleons. And even considering that this is an average & there is a small tail of energies at the high end, there would not possibly be enough high energy ones to cause any significant fusion.
So, no low-tech H-bombs for the terrorists! It was just an anxiety thought I had during a sleepless night…
Nah, it works fine, except it is not exactly “low-tech”, which is why to achieve those temperatures they utilise those neutral-beam accelerators and cyclotron heating.
Given the heroic measures heavily funded experimentalists have to resort to in order to generate even a bit of fusion, I don’t think we need to worry about home-made H-bombs soon.
Unless of course some demented genius comes up with something that knocks a lot of current physics into a cocked hat…?
Again, if you don’t care about sustaining the reaction, it’s easy, as with a Farnsworth fusor (the same inventor as the television tube, and after whom the Futurama character is named).
Muon catalyzed fusion is another long known method of inducing nuclear fusion, the idea originating in the 1950s. The problem isn’t doing it, the problem is figuring out a way to do so that exceeds breakeven.
You certainly aren’t getting a bomb out of it, though.
Or a micro black hole undergoing evaporation via Hawking radiation. Of course much like antimatter first you need to somehow make it, then somehow survive being near it…and by “near it”, I mean “being in the same solar system”.
Damn, we really need to find a way to harvest the energy from all those wasteful neutrinos.
Some material which will stop them. Where is scrith when we need it? Paging the protectors…
I wonder what the neutrino energy flux from the sun is at earth orbit radius (I recall the electromagnetic energy flux is on the order of 1 KW per square meter)…
OK, I could probably look up the data and calculate it myself but I’m lazy…
Where you see only problems, perhaps there is opportunity. Can we design a “neutrino diet” weight loss program around this, where most of the energy goes to neutrinos rather than your belly and thighs?
