To make the experiment easy, let’s assume I have a device that can, like in some Science Fiction stories I’ve read, create a fied that flips everything within it to antimiatter. So we don’t have to worry about storage, and can use any material in any configuration we desire.
What I’m curious about and can’t really get my mind around is which type of design would be best to avoid this situation:
Suppose we had a kilo (let’s thing BIG) of lead within the field generator, surrounded by a shell of lead (or steel, or whatever). It seems to me that when the “core” was turned into antimatter, 2 things would happen:
The outer layer of the core would contact the enclosing metal and turn to pure energy, creating a huge detonation outwards;
But it would also cause an implosion inwards, thus keeping the rest of the inner layers from initially contacting normal matter.
I know we’re probably talking microseconds here, but it looks like this would produce an initial bang followed by a longer but less intense “bloom” as the vaporized antimatter came out of the energy-rich vacuum and started contacting normal matter.
Is this correct, do you think? If so, then might we instead want a large but thin antimatter core, or maybe a thin disk fired through the field to impact with a normatter target?
Or would the time span be so short for total conversion that this is trivial?
I don’t think it matters. It’s not like an atomic bomb, where you need to keep the fissile material supercritical for long enough to produce a substantial yield. Each anti-atom will annihilate a normal atom without needing any neutrons or other external inputs. For a practical design, you’d just want to get the anti-matter into the smallest possible volume so that the bomb itself is as small as possible; but, as soon as you release the containment, you’ll get all the energy released as quickly as the anti-matter can vapourize.
Incidentally, 1kg of anti-matter will only give a yield of about 20 MT (1MT = 4.2E15 J, 1kg = 1 * (3E8)^2 = 9E16 J) - probably cheaper to do it with hydrogen.
First, thanks for the equation. Is that in joules, yes? I always wondered how to figure this, seriously.
Second, I am not thinking big enough, obviously. Let’s substitute the kilo of lead for a Hummer H1. Yeah, now let me try to figure out the equation. This may take a few days, I fear…
Actually, make it 40 MT, not 20 - each kg of anti-matter will annihilate 1 kg of normal matter, so the total mass involved is 2kg, not 1. Still only equivalent to a medium-sized H-Bomb.
Wouldn’t a 3D grid of antimatter balls, enclosed by a lattice of normal matter be more effective? With a sphere enclosed by a shell, it seems to me that you’re taking a chance of having the sphere get rocketed off in some random direction. A grid would actually take advantage of that effect- at detonation, the antimatter balls would shoot off in all directions, leading to a much bigger ESK*.
You could just use Google’s built in calculator, to get the energy. A Hummer masses ~4600 kilograms - type in “4600 kilograms in joules” and google will give you the answer.
Huh? 40 megatons would be a frickin’ huge hydrogen bomb, as in the second largest ever tested or developed.
I still think you’d want to react the anti-matter & matter as quickly as you could- you’d get a bigger bang that way.
My concept would be something like a h-bomb, except instead of lithium deuteride, you’d have the antimatter in the secondary, possibly even with the conversion device triggered by the primary detonation.
I speculate that in the interest of getting the biggest bang possible, you’d want to compress and contain the matter/antimatter as rapidly as you could, and as much as you could. I can’t help but think that the second stage of a thermonuclear weapon would be as good as you’re likely to get.
Secondary effects might be very important. Since your CPT * inverter can turn any material into antimatter, probably the antimatter would be some handy solid composed of fairly heavy nuclei. First, the positrons surrounding the nuclei would annihilate the electrons of adjacent matter. Then you’d have a plasma of matter and antimatter nuclei. When these collided, you’d get very complex reactions because hadrons (protons and neutrons) and antihadrons don’t immediately convert into pure energy- typically they create some gamma and various pions that decay into energy. Meanwhile, the energy released would be more than enough to overcome the binding energy of the nuclei, so they would be blown into loose fragments of every conceivable composition. Depending on the details of the reacting materials there could be significant residual fallout from surrounding matter radioactived by bombardment of high-energy particles. (So much for the science-fiction idea of antimatter bombs being “clean”).
The most interesting possibility is that the configuration of the reacting materials could yield significant “shaped charge” concentrations of force. Or that a relatively small amount of antimatter detonated in hydrogen-rich surroundings could yield large secondary thermonuclear reactions. The details probably have been worked out in classified studies as a thought experiment by nuclear weapons designers.
I don’t really see the implosion effect being significant unless your core was spherically symmetrical, and even then it’s not clear how big a problem it would be.
For a non-symmetrical core, the “shell” of reacting matter/antimatter won’t generate pressure evenly, and will blurge jets of antimatter plasma outwards all over the place. These will mix nicely with any surrounding matter and release the rest of your anihilation energy in short order. As Lumpy pointed out, this could give you an asymmetric or even a deliberately shaped explosion geometry.
If you wanted a symmetrical explosion, I’d suggest a hollow antimatter sphere filled with liquid, surrounded by gas (or even vacuum) and held away from the bomb walls on little pins. When you turn the hollow sphere to antimatter, there will be an intimate, high-density matter-antimatter contact on the inside of the sphere, and a low density matter-antimatter contact on the outside of the sphere (neglecting the little stand-off pins). So the antimatter gets blown outwards symmetrically at the start, and if you get it right it’ll all react before the implosion effect overcomes the internal driving pressure.
No matter hou you arrange the fuel, it seems to me that a purely antimatter bomb is going to give a slower reaction than a fission or fusion bomb. The reaction in a conventional nuclear bomb is a self-reinforcing chain reaction; the byproducts of the fission and fusion are neutrons which trigger more fission and fusion to occur. The reaction takes microseconds to run to completion. The energy released by the matter/antimatter reaction doesn’t do anything to speed up the reaction of the remaining antimatter, and may actually slow it down by pushing the matter and antimatter away from each other. Even clever mixing arrangements don’t overcome the limitation that the time needed for every atom of antimatter to find and react with matter will take a lot longer than the microseconds-long chain reaction in a fission bomb. On the other hand, a fission bomb needs to get the reaction over with fast because the chain reaction only happens when the fuel is at a critical density; once the fuel is dispersed, the reaction stops. Assuming you’re detonating it in an atmosphere, the antimatter in that bomb is going to continue reacting with surrounding matter even if it’s been scattered by the released energy. The only real problem will be if the reaction takes long enough that the antimatter is actually hurled completely off the planet.
So you’d expect that an antimatter bomb will take longer to burn, and release its energy over a larger area, than a fission weapon. Depending on the nature of your target this could be a good thing or a bad thing. As an airburst against an unhardened city, might be a good thing. Against a hardened underground bunker, might be better off with the nuke.
Oh, cool, Google does matter-energy conversions now? It used to be that you had to explicitly include the c^2. I also noticed earlier today that the Google calculator now recognizes “radius of the Sun” as a constant, whereas it didn’t before… I wonder when they upgraded it?
To avoid taking up bandwidth, I have not included AndrewL’s post here. Please reference it above…
But I would like to say, that this is pretty much exactly the kind of stuff I was wondering about, and thank you, sir, for your input…
Although I did not say it, your comments on the speed of the reaction was also something I was concerned about: Near-c reaction with respect to neutons and all, versus the necessity of the antimatter having to contact normal matter all on its own.
That was helpful in convincing me I am not (yet) completely insane, thanks.
Yeah, and it works with all sorts of goofy units - if you need to know how much energy 3 slugs are in horsepower-hours or rod-newtons, it can tell you.
How about you suspend a rod in a vacuum and then turn the surface of the rod into antimatter. The antimatter surface would interact with the matter core at the interface between them and trigger an initial explosion. The force of the initial explosion would then propel the rest of the antimatter outward in a dispersal pattern that should direct most of the force of the main explosion outward.
