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Hi Bullfrog, regarding the halt order I'm sorry because I cannot help you. Regarding the Axis I think that they had the same potential of USA in terms of resources/money and I think that the Axis was in a much better position to get the nuke a couple of years before USA (leaving aside the "bad things" that we cannot mention) .
A kiloton of TNT is ~4*10^12 Joules. A single gram of mass could theoretically equal ~9*10^13 Joules. (E=MC^2) So only about 5-10 grams or so of that nuke was converted to energy. So why not just drop the 10 grams of nuke that gets converted to energy?
Because nuclear physics doesn't allow for that kind of shortcut.
The same principle, in adapted form, holds for why the USA didn't just drop the gadget part of the nuke on Hiroshima from a fighter plane. You don't want the plutonium or uranium, you want the explosion. And to do that in 1945, you need to compress your core to a fraction of its size within milliseconds, requiring either half of a small cannon and explosives (Little Boy), or about a ton of high explosive, which is carefully shaped, confined, and focused on your plutonium core.(Fat Man) If you improve your hydrodynamic calculations, you can reduce the amount of explosives and such, but we're talking 1945, when Computer was a job description. Not today, when our equipment eats differential equations for breakfast...
If you're really interested in nukes, try tracking down a copy of Richard Rhodes' The Making of the Atomic Bomb. It won a Pulitzer Prize in Nonfiction, a National Book Award and a National Book Critics Circle Award when it came out.
Jonathan Fisher
I think he means pointless on the overall outcome of the war, and that all the investment into subwarfare would have been better off invested elsewhere.
I guess that this point is not clear: the nuke part should be still 5 grams. Is not one gram more or less that it makes the difference. What it does, for example, is the conventional explosive that you should add. I was wondering if less conventional explosive still starts the nuke reaction.
Counter-argument: This type of argument though assumes because X amount of research failed X+anything would also fail, which is not necessarily the case (not that it is provable 1 way or the other) I.E. Had Doenitz had his way, more money would have gone into R&D and construction and the war in the atlantic turn out different.
EDIT: And this applies to nuclear or any other research, you just can't ACTUALLY know, just pretend and simulate
Depends on what kind of nuke you're going for: a 'simple' nuclear device (which the first examples were extremely inefficient at using their energy envelope because of the experimental nature of the weapons) or a thermonuclear device capable of several... 'layers' of detonation would be the best way to simply describe it (a primary and secondary reaction enhanced with tritium or palladium).
Anyways, the general response is that 5 grams of fissonable material is rather small; the expense in developing the appropriate detonation proceedure for something that small would be better spend in delivering conventional munitions.
Nitpick- AFAIK, the most common thermonuke material used for delivery-capable weapons would be a compound of lithium deuteride. The lithium is Li-6, chosen to emit deuterium upon fusion, thus getting your fusion material in a nice, stable form suitable for long-term storage.
I think I confused Cardus(the guy you replied to) even further. You got ~1 gram of energy out of a 4 kilograms of fissionable material with Little Boy,(rechecked my numbers) and physics makes it unlikely you could reduce that ratio to anything close to 1:1, or even 1:10. (without 'cheating' and going thermo-nuclear; the reaction material in that case is not the fissionable material, anyways) Anti-matter would get perfect efficiency, of course, but that stuff is ridiculously expensive and tough to contain, anyways. For the foreseeable future, nukes and thermo-nukes are the cheapest way to level a city, and the ongoing argument is that it is *tough* to miniaturize that stuff to fit on a V2, even, in the WW2 timeframe.
If I were to look at how fast you *could* miniaturize warheads, I'd look into when the first sub-launched stuff started showing up. Here's a few links...
http://en.wikipedia.org/wiki/Regulus_missile
http://en.wikipedia.org/wiki/Mark_5_nuclear_bomb
So...the first system proposed used a warhead just a little too big for a V2, and a cruise missile with almost three times the range, but they didn't show up until 1952 and 1951, respectively. You might argue that there was no 'push' to miniaturize, but think for a minute: SOV first demonstrated nuclear capabilities in 1949. Even with the threat of a 'decapitation strike', it takes another 3 years to miniaturize enough to fit on a V2-type weapon, and this is with 4 extra years of experience since Hiroshima.
Paradox is being *generous* when they gave Miniaturized Fission bomb a 1948 tech date. They basically assumed nuclear research came to a halt between 1945 and 1949, when SOV catches up to USA. Reality would probably give it a later tech date, but gameplay considerations make it much earlier than it should be...
Jonathan Fisher
Oh, I thought that he was trying to detonate *only* 5 grams of fissionable material... to which I thought "how silly" but now I'm the dunce.
I'm sorry Jonathan if I continue to bother you. In my understanding of early nuke weapons one matter is the fissile material and one other is the conventional explosive. To start a nuke reaction you need some of the latter. I guess (because I don't know really) that fat man had about 2 tons of conventional explosive. This explosive gives to a few gram of plutonium a detonating power of about 200,000 kilotons.
My question is: if the conventional explosive is dropped to 1 ton is the blast reduced by the half?
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given the relatively weak nature of the dropped nukes, and their dirty/inneficient nature, im inclined to believe that much more than a few percentage points of decrease and you might not even get a reaction, just a conventional bang and a rather radioactive mess.
Im not certain of the specifics, but alot of the purpose behind the explosives was to drive the material into a superdense state, forcing the atoms closer together, making it aqs likely as possible that emitted particles will collide at least once on the way out, and with that, really go bang. while i won't argue that decreasing the conventional explosives will result in no reaction occuring, as i just don't know neough to say, i will say i'd find it somewhat unlikely.
think of it like starting a cranky lawnmower, you could pull half as hard, and it just might still start, but its gonna take a second or two longer to reach full power, on the other hand, if you didn't pull hard enough, its gonna turn over a couple times and quit, thats it. find the happy medium and not only do you not work too hard, but you aren't waiting for it to get going either.
Im not certain of the specifics, but alot of the purpose behind the explosives was to drive the material into a superdense state, forcing the atoms closer together, making it aqs likely as possible that emitted particles will collide at least once on the way out, and with that, really go bang. while i won't argue that decreasing the conventional explosives will result in no reaction occuring, as i just don't know neough to say, i will say i'd find it somewhat unlikely.
think of it like starting a cranky lawnmower, you could pull half as hard, and it just might still start, but its gonna take a second or two longer to reach full power, on the other hand, if you didn't pull hard enough, its gonna turn over a couple times and quit, thats it. find the happy medium and not only do you not work too hard, but you aren't waiting for it to get going either.
does anybody know it for sure? if the conventional explosive is dropped to 1 ton is the blast reduced by the half?
The conventional explosive does not affect the end reaction. I'd suggest reading "Sum of All Fears" (Tom Clancy) for anyone who would like to know more. While not entirely accurate, it does give an adequate description of how the bomb works.
True enough. Mind you, it would certainly have been better if Harrison Ford had reprised the role (even if he was getting on a bit...)
Hi Wraith11B, as it seems that you know something about could you please explain what accounts for in terms of weight?
We know that the fissile part is few grams, but the total weight was about 4 tons so do you know the difference by material/component? For example:
plutonium 8 g
case 1 t
conventional explosive 500 kg
etc
This is true, as the saying goes we have the benefit of looking back in hindsight, but at the time the submarine war was very damaging to Britain and at least in theory it could have capitulated. It's those chances that grand strategies are made against other powers.
It isn't a linear scale, as far as I know. There is a certain amount you *must* compress the core to get any reaction whatsoever, and any further compression increases yield. If you only hit the bare minimum, you only add a small amount to the conventional explosion, which is called a 'fizzle'...
Better compression means the core stays compressed at critical mass for a longer period before flying apart. More importantly, better compression decreases the amount of empty space between atoms, increasing the number of neutron-nucleus collisions. Think of the latter as shooting an arrow randomly at a herd of deer in your kitchen versus shooting at the same herd spread across a football field.
The relation between critical mass and density is apparently M ~=C / (density^2), going by wikipedia.(where C is a constant determined by the material used, geometry, etc) However, to get a nuclear explosion, you need to go supercritical. Here things get complicated as related to yield, as going only a tiny bit supercritical in an experiment means you die from radiation poisoning, you have a fraction of a second to keep your colleagues alive, and you have probably a full second or ten before the core melts; however, going highly supercritical means you're standing next to the Trinity test and things assume an air of inevitability.
Now, what is the relation between amount of supercriticality, density, mass, and yield? I dunno. And what's the relation between amount of conventional explosives and density? I dunno. But it feels unlikely that you'd get half the yield from half the amount of conventional explosives, using the same design. I'd guess at one-quarter, or one-eighth, or less. You might go down from a city-killer to a neighborhood-killer, or, worse case, just another 'dirty bomb'.
Better designs mean you can get the same amount of compression out of less explosives, but as I keep pointing out, better designs take time to make. And the most relevant part of comparing nukes to V2's is that we didn't have a roughly V2 sized warhead until 1952, three years after SOV demonstrated their first nuke.
Actually, the relationship between mass, energy and fissionable portion is more complicated- sorry for confusing you.
In a nuclear reaction, some proportion of your plutonium/uranium is fissioned into 'waste products'.
In the same reaction, some smaller proportion of mass is converted totally into energy.
The amount of mass converted to energy is the difference between the mass of plutonium and the mass of the 'waste products.'
Even if you cause fission in all your plutonium, you won't convert all of it into energy.
Also, if this site is correct, roughly half of the weight of Fat Man was conventional explosives.(5300 lbs)
They also make the mistake of confusing amount fissioned with the amount converted to energy, so you're in good company.
Actually, the relationship between mass, energy and fissionable portion is more complicated- sorry for confusing you.
In a nuclear reaction, some proportion of your plutonium/uranium is fissioned into 'waste products'.
In the same reaction, some smaller proportion of mass is converted totally into energy.
The amount of mass converted to energy is the difference between the mass of plutonium and the mass of the 'waste products.'
Even if you cause fission in all your plutonium, you won't convert all of it into energy.
Also, if this site is correct, roughly half of the weight of Fat Man was conventional explosives.(5300 lbs)
They also make the mistake of confusing amount fissioned with the amount converted to energy, so you're in good company.
So the point is that to have 200,000 kilotons with that early technology it was required about 2 tons of conventional explosive + some gram of plutonium. My next question is: does anybody has any idea how many kilotons (if any) will be produced with about 1 ton of conventional explosive?
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