So Islamic Jihad or some other faith-based organization decides to build a Fat Boy. Let assume for the sake of discussion they can buy all the uranium they want from the Russian mob. Or Spectre. Whatever.
Can they do it? Are they more likely to make a glowing crater in the godforsaken desert? Or wouldn’t they even get that far?
Let us further assume that faith, though it will move mountains, will not split nucleii.
This seems like it was answered pretty well in this current thread: Atomic Bombs - why are they so hard to make?
But the most likely outcome would be that they would make a mistake in the explosive charge designed to make the uranium reach critical mass. Assuming they have the fissionable materials, that’s the toughest part. The result of this failure would not be fission, just a whole lot of radioctive material blown all over the place. You’d have the fallout without the massive destruction.
Read Tom Clancy’s, “The Sum of All Fears” if you would like a good overview of the difficulties involved in making an H-bomb.
I have heard a few times that you could make an atomic bomb (if you had weapons-grade plutonium) by dropping half of the critical mass app. 30 feet onto the other half. Does this have any basis on truth?
elucidator: No “Fat Boy” - the bombs were called “Little Boy” and “Fat Man”.
I guess a “Little Boy” design should be achievable - it’s more or less the design that badtz maru describes, with a few tweaks, see below.
Constructing a “Fat Man” takes some people who are very good indeed with explosives, as it’s dependent on compressing the fissible material by a more or less spherical charge.
The problem for a terrorist organizaion is, among other things, that they can’t test. And if the conventional explosives go off, but the chain reaction doesn’t start, they’re in trouble. Deeply.
I’ll second Zenster’s recommendation of “The sum of all fears” for an idea of how it could be done and what problems must be overcome. IMHO, it’s the last readable novel of Clancy’s, anyway.
badtz maru:
Replace “drop” with “shoot” and plutonium with U-235, and you’ve just described the Hiroshima bomb. Well, more or less:
I am not a Nuclear Scientist (IANANS ?), but I think the problem is: You might or might not get a chain reaction going. If you want to make sure thet the reaction starts, add a neutron source to your setup. The problem is, of course, that as energy levels rise, the explosion tears apart your expensive plutonium into a lot of subcritical masses. This makes for a lot of contamination with very little yield. Technically speaking, it’s a nuke, but if you could’ve achieved the same effect with 5 tons of Sempex, why bother ?
If you’re going to make a nuke, you want a ultrarapid change from subcritical to supercritical, you want to make sure that there’s an abundance of neutrons to start and boost the reaction (get some tritium in there), wou want to contain (if at all possible) the critical mass during the first reactions to expose as many nuclei to neutrons as possible.
The Hiroshima bomb was contained in a heavy steel canister to prevent the “nuclear firecracker” phenomenon, it did have a neutron source and it used an explosive charge to collide two subcritical masses to one supercritical.
S. Norman
Also, don’t think of “weapons-grade” as being anything special. All weapons-grade means is that they dope it with other stuff so that it is stable enough to not blow up during handling, but still volatile enough to go boom when it’s supposed to. Get pure enough fuel, and you can set it off by droping it a lot less than 30 feet.
“Weapons grade” is special, since it is highly enriched, pure U-235.
However, any body with access to a howitzer or cannon barrel can probably make a bomb. Simply reduce the charge on the shell somewhat and place 1/2 the critical mass in the shell. Use the other half of the critical mass and create rings that mate with the U-235 on the shell.
When you want the bomb to go off, fire them towards each other. You can test it with U-238 just to make sure that everything works. If you do not have a neutron souce –not tritium btw – you must make sure that the shell “sticks” into the rings and does not blow apart, then you can wait a few milliseconds for a random neutron to start the thing off.
Read “The Making of the Atomic Bomb” for more details. Note that the Little Boy bomb was not tested either. They knew it was going to work.
Sorry, my bad.
The benefit of having tritum at the core of the chain reaction supposedly was to have a lot of energized neutrons (tritium isn’t a neutron source, but it has a lot of not-too-well-attached neutrons) around - but apparently, I must have dreamt reading about that, because I can’t find a reference anywhere.
S. Norman
Lots of interesting resources on nuclear and other weapons of mass destruction on the Federation of American Scientists web site, including an Introduction to Nuclear Weapon Physics and Design FAQ.
So, is Islamic Jihad eligible for federal funding now? (“Yes, our organization is interested in receiving funds for, um, ‘urban renewal’ projects.”)
As I hope is clear by now the answer to the OP is “Yes, any Bozo can build an A-bomb, but it won’t be a very good one.”
Part of the difficulty, described above, is getting the critical mass close enough together fast enough. Too slow and the “bomb” will just melt and emit a lot of radiation but no explosion. The opposite problem is keeping the pieces together long enough for the chain reaction to release a significant fraction of the available (E=mc2) energy. That’s one of the tricks of the “implosion” bomb – the hollow, sub-critical sphere of fissile material is imploded and the momentum of the implosion keeps the mass together for a while until it can rebound. By then the reaction has had time to run for a while – lots of energy is released. That’s also why the neutron source, mentioned above, is so important – it starts the reaction ASAP.
In fact, containing the explosion until the reaction has had time to complete is the trick to making any sort of bomb at all. It’s the difference between burning a pile of gunpowder and lighting a firecraker. That’s why they use a pipe when they build a pipe bomb.
So if your goal is to make an efficient bomb, giving maximum yield for the available fissile material – no, you can’t do that in your backyard. But if you just want to create a terrorist nuclear threat, then yes, you can do enough damage to kill a few people and get everyone’s attention.
If they are bozos, they would probably irradiate themselves quite soon handling that radioactive stuff.
Just look out for a jump in sales of lead based clown make-up.
The steps are:
First, get a lot of plutonium.
Second, get a lot of explosive explosive.
Third, find a sucker to shape the plutonium into two pieces, cone and sphere, with the sphere containing a concavity the exact inverse of the cone. If extreme measures are not taken, the sucker will likely be dead of cancer before the bomb is detonated.
Fourth, get a cannon barrel. Line the cone up so that it will fire into the sphere at the end of the cannon. Techincal details omitted for reasons obvious to all non-clowns.
Fifth, get the bomb, which probably weighs at least a ton, to your intended destination. Don’t even try places like DC or New York–they have a small chance of discovering you. You’re much better off targeting another non-strategic landmark like Poughkeepsie or Provo.
Sixth, find another sucker to pull the lanyard.
actually sofa king, you cant make a “little boy” style bomb (bring two sub-crtitcal masses together) with plutonium, only uranium. plutonium will pre-detonate and you don’t get a very big BOOM (i.e. the two pieces are blown apart before they have had a chance to do much fission). that’s why they had to use the explosive compression trick for “fat man”.
-luckie
Hmmm. I thought the compression trick was for the U-235, while the plutonium was a sure thing. Eh, someone will set me straight if it weren’t you.