It doesn’t have to be carried on a B-52. It can just sit there in the warehouse where it was assembled.
Rob
Well, that was the largest ever detonated. What’s the largest that could be built assuming that the size was limited only by materials available. Of course, we don’t know what FOGBANK is nor how much you would need.
Rob
Basically, it’s only limited by raw materials.
That’s my premise. Given that, how big a bomb can be built?
Rob
One of Richard Rhodes’ excellent books about nuclear weapons quoted a scientist (Teller?) saying that at a certain point, I think above 100 megatons, you hit a sort of limit. Above that, you end up merely lifting a larger chunk of atmosphere without making much other use of the increased enegy. Which is to say that I’m not sure of the theoretical limit, but that there is a practical limit of how much energy can be extracted from a nuclear weapon.
But I may be remembering this wrong - will try to look it up later.
However, I do think I recall corectly that though the Tsar Bomba Was detonated at 50 megatons, it was downrated from 100 to prevent blowback.
In our solar system: the sun
IIRC, the sun is a fusion reaction whereas nuclear bombs are fissile.
Well, both are nuclear, just one is fission and one is fusion. So, depending on your definition, I’d say that kanicbird has it…the largest explosions (leaving aside the Big Bang) come from really really large stars blowing up . That would be the largest theoretical bomb.
As for fission, I’ve never heard there is an upper limit, though from a practical perspective there certainly is. But if you could get an infinite amount of fissile materials (well, I suppose fissionable is more accurate) I don’t see why you couldn’t make a bomb out of it that would simply take a long (infinite) amount of time to propagate the explosion through it. But I’m no physicist, so just my WAG (I DID actually stay at a Holiday Express last week though…)
I was after how large a bomb could be built limited by materials alone. Practicality doesn’t matter. I understand that the Tsar Bomba wasn’t really practical either. Could we build a gigaton-class device if we wanted to? How about a tera-ton?
Thanks,
Rob
I could be wrong about this, but I believe the structure of the material is important for it to detonate properly. At some point gravity itself will limit how large that structure can be without deforming, right?
Do you mean materials easily available on Earth now? Or do you mean total amount of materials in the universe?
There will be lots of practical issues. One that strikes me is the difficultly of assembly whilst getting an increasing yield. By assembly, here we mean the action of assembling the separate lumps of less than critical mass fissile material into one larger than critical mass lump. In order to get a really good yield, explosive assembly is used, with enough force that it actually compresses the metal to about double its normal density before the lump has a chance to go critical. Just at the moment when it reaches maximum density an initiator is used to flood the mass with neutrons to start the reaction. The big problem is random neutrons from the fissile mass. One of these wondering about before the system has reached maximum density will cause a chain reaction before you want it - and it will just blow the mass apart again with very low yield. (This sort of problem is probably why the North Koreans have so much trouble making a weapon do anything more than make some noise - even though it did technically go critical.) A really large fission bomb is going to become harder and harder to make work, and at some point the amount of fissile material involved will reach a size were there will always be a random neutron that comes along and spoils the process. So for a simple fission weapon there will be a maximum size. The size depends upon the fissile material used, since that determines the rate of neutron production.
For a fusion device it is harder to say. However one notes that fusion bombs (aka Hydrogen bombs) get less than half their yield from the hydrogen fusion, and the remainder is due to much more efficient fission of the fission stage, due to the much higher neutron flux generated by the fusion reaction, which floods the fissioning mass whilst it is still dense enough to make use of the neutrons.
So one suspects that both simple fission devices, and hydrogen bombs both have limits where it is impossible to get them to reliably ignite at a point where their yield is useful.
We’ve had fusion bombs since 1951. Granted, they also use fission reactions, but that’s because we don’t have the convenience of using gravity to push the hydrogen together.
Did someone not pay the gravity bill?
Hydrogen aka thermonuclear bombs are fission/fusion; we have yet to invent pure fusion bombs.
True, but scaling up a hydrogen bomb requires only adding more hydrogen, not adding more fissile material. You need the fission bomb to start the fusion, but once started, it’s self-sustaining.
I’m glad you cleared that up. I have no idea what you cleared up, or what I am supposed to make of this information of your whereabouts, but I appreciate your obvious candor.
Never knew that (of the million other things I don’t know about nukes). It does go against the fission:trigger-to-bigger-and-better fusion result, which is the commonly said process. So in the bomb as an effective device (ie what we want a bomb to do, go boom big), the initial fission is the “pre-trigger” to the real (contextual) trigger, the fusion, and the subsequent flood of super fuel.
::sorry, didn’t get the prompting pull-cite for the following from upthread::
Is gravity truly out of the picture as a limiting factor, as a matter of first principles? For example, ignoring macroscopic mechanical forces to build the damn thing, on Earth or in microgravity, what shapes are optimal, that is, do the masses change their initial and dynamically changing sequence of subsequent shapes as those initial masses (and supporting systems) are ramped up?
[self-hijack]
A related thought, trying to articulate what i’m getting at: do all stars start out spherical? The “gadget” (non fusion) was spherical. In what way does explosive nuclear material change shape as they are doing their nuclear thing?
[/self-hijack]
Frankly, I don’t know if all of this is even pertinent to the OP, but it might be, so what the hell, what else is new?
Is there a back-of-the-envelope estimate of the amount of weapons-grade fissile material there is in the world and what the accumulated yield would be if detonated all at once?
Stars (as best we can tell) start out as big irregular blobs of gas, which slowly collapse due to gravitational attraction. This will soon take on a spherical shape, slightly oblate due to rotation. (In space, everything rotates!) Spheres are simply the shape of minimum gravitational energy (known to Aristotle, although not in quite the way we know it today.)
A Plutonium bomb in a spherical shape is simply the best way to minimize the distance from any part of the Pu to any other part. It isn’t mandatory. You could easily build a fission bomb out of two half-cubes which are slapped together (very fast) into a full cube. Or two half-pyramids. Or a “cup and sphere.”
A really big bomb could be made of a large number of flat plates of Pu, one above the other, as high as you want, which, at a signal, would be arranged to collapse upon each other – think of squeezing a really big Dagwood Sandwich. This could work all the way up to, say, a compressed mass of Pu as big as Scrooge McDuck’s money bin. Uncompressed, with the necessary spacing to prevent premature fission, it would be much taller; when you remove the spacing and force the plates into contact, you have a supercritical mass.
There would be some tendency for the mass to blow itself to bits; however, nuclear reactions happen extremely fast, so, once you get the chain reaction started, it will go like mad – come un pipistrello furoi dall’ inferno – like a little mad bat out of hell – and much of the Pu will go boom.
(To use some very highly technical terms…)