Submitted by something-stupid2134 t3_zhmf26 in askscience
Most sites are giving me mixed answers. I know some of it does overlap, but I can't find a clear answer. Moreover, is hydrogen bomb more powerful and destructive than a nuclear bomb? I'd like to learn more clear distinctions between these weapons and how destructive they can be as a comparison in terms of, say, size/weight/amount of material in the bomb vs size/area covered/extent of explosion, if that makes sense. Thanks in advance!
Sorry, but quick question, why is nuclear fusion said to be 4x more powerful than nuclear fission but H bombs are 1,000x more powerful than atomic bombs? Is it because the fuel can be more compact
Because fission bombs tend to blow themselves apart so even with a kg of material, barely any is fissioned
So if they didnt, they’d be much closer to being 4x less powerful, instead of 1000x
Meanwhile hydrogen bombs keep together better.
[removed]
Moreover by design the hydrogen fusing under certain geometries enhances the fission by a large factor.
[deleted]
In terms of the relevant reaction Q-values (the amount of energy released by one single reaction), fission does on the order of 10 times better than fusion.
But if you divide the Q-value by the mass of the fuel particles, fusion does better than fission.
People often get that confusion, because they've heard that fusion releases more energy per unit fuel mass, and are then surprised to find out that fission releases much more energy per reaction.
And then in a weapon, the crucially important role that fusion fuel plays is that it produces fast neutrons that can induce more fission in an already supercritically-multiplying system of fission reactions. Each additional neutron produced by fission therefore has the chance to cause many more fission reactions, each of which comes with on the order of ten times more energy than the initial fusion reaction.
So thermonuclear weapons are able to much much more yield for a given total fuel mass.
A related question:
What is a neutron bomb? I've heard the term and from what I recall, it was supposed to be a bomb that destroyed people but left buildings intact.
A neutron bomb is a type of nuclear bomb designed to generate a high neutron flux, rather than a high explosive power. Since neutrons don't carry an electric charge, they can penetrate many materials more effectively than charged particles, which are slowed down by all the electrons. This means a neutron bomb produces a lot of radiation that can effectively penetrate buildings and even tank armour, killing many people from radiation poisoning while creating a relatively small explosive yield. This would make it suitable as a tactical nuclear weapon, meant to eliminate armoured divisions while limiting infrastructural damage.
If it can penetrate through buildings or armor, what makes it "stop" inside of a human?
It doesnt stop inside a human. It mostly passes through you the same as through a wall.The difference being that damage in a wall or armor is likely nothing worth writing about, while passing through living tissue neutrons break DNA and disrupt cells.
Ah, I see. I interpreted "penetrating" as "passing through with relatively little interaction", not as "bullet penetrates a window".
[removed]
[removed]
It's a bomb that releases unusually many neutrons for its yield - you remove as much material around the fusion stage as possible. It's still pretty destructive to non-living things, but it's more dangerous to life than a normal bomb with the same yield.
conventional thermonuclear is like fission-fusion-fission
a neutron bomb is more like fission-fusion
Instead of using the high speed fusion neutrons to induce more fission, you just let them escape.
[removed]
This is a great explanation
You could build a giant pure fission weapon, but why would you? Fusion makes it much easier to reach megaton yields - fusion itself releases more energy per mass, and it also makes it easier to fission a lot of uranium.
For very small weapons the simplicity of a pure fission weapon can be more important.
A fission bomb must start with a subcritical assembly and detonates by making it become supercritical. If you want a large amount of fission fuel, making a shape that's not already supercritical is a significant design constraint.
Economics is also a factor. A pure fission or boosted fission weapon gets most of its yield from the fission of either highly-enriched uranium or weapons-grade plutonium. Those are expensive.
(Boosted fission = you put a little bit of fusion fuel in the middle. It doesn't make much yield directly but it makes lots of neutrons to cause more fission in the plutonium. Without boosting only a small percentage of the fuel actually fissions.)
A thermonuclear weapon, AKA hydrogen bomb, uses a (nowadays always boosted) fission primary to cause a larger fusion reaction. Typically, but not always, the fusion then creates additional fission in a natural or depleted uranium tamper, much cheaper per kg than highly-enriched uranium. The yield is predominantly from the fusion and the tamper fission, and a relatively small amount of expensive material is needed for the primary.
Almost all current nuclear weapons are thermonuclear. It's considered to be the best design even for relatively low-yields of a few tens of kilotons. I think North Korea and possibly Pakistan are the only states using pure or boosted fission weapons.
[removed]
[removed]
I'd argue that boosted fission bombs don't count as 'a-bombs' since they use physics only understood because of huge thermonuclear tests in the 'h-bomb' era. And they use fusion, of literal hydrogen isotopes, even if it isn't a major contributor to the explosive yield.
Yes, I agree that boosted weapons are technically "thermonuclear" too, just with a much smaller amount of fusion fuel. I don't think the common terminology is good, but this is what it is.
And don't boosted weapons use fusion mostly just to generate neutrons to cause fission fast enough before the device blows itself apart?
Yes, but the same could be said of many "true thermonuclear" weapons too. The main contribution of the fusion fuel to the yield is due to the high-energy fusion neutrons inducing more fission, rather than the fusion reaction Q-values, which are on the order of 10 times lower than the relevant fission Q-values.
Q-value, explain it like I’m 5.
Amount of energy released by a single reaction.
[removed]
Modern designs are all thermonuclear (fully thermonuclear, not just boosted fission). But not all countries have modern stockpiles. So we still need words to refer to old designs and differentiate them from modern ones.
[removed]
All nuclear weapons use fission in some way. Even "pure fusion" weapons are not really pure fusion.
Reaching a state where a thermonuclear burn can take place, outside of stars and certain scientific research devices, requires fission.
Correct me if i am wrong but there aren't any "pure fusion" bombs, to achieve that you'd need to somehow use conventional explosives to heat deuterium and tritium to a couple hundred million degrees and ridiculous unachievable bar.
Yes, that's what I was saying. There are weapons that are loosely referred to as "pure fusion", but they don't actually purely consist of fusion fuel. Some amount of fission fuel is needed to ignite the thermonuclear burn of the fusion fuel.
[removed]
According to your definitions then, all nuclear weapons would be called "nuclear" (great, this is right), but then all chemical explosives could be called "atomic" (highly confusing, given that the term "atomic bomb" usually refers to a subset of nuclear weapons).
Curious: if atomic bomb is a subset of nuclear bomb, then some nuclear bombs are not atomic bombs. Which are those?
Like my comments above say, "atomic bomb" is usually used to refer to fairly primitive designs that don't make much, or any, use of fusion fuel.
[removed]
Can someone update this question with a proper answer? It’s one of the first google results when trying to find out how much hydrogen is actually used in a hydrogen bomb and the answers are so wildly different that I don’t know which is right.
We got 17kg, 771kg and 10,000 kg!
>The simple relationship E=mc2 tells us that 2.3 kg mass was converted to energy in the bomb, but a hydrogen fusion reaction only converts about 0.7% of the starting mass to energy. So they would have had to burn through at least 330 kg of hydrogen, and they probably started with much more since the efficiency of fusion won't be 100%.
>According to wikipedia, high yield nuclear weapons produce something like 5 megatons per metric ton of material, which would mean the Tsar Bomba had about 10,000 kg of hydrogen.
Just to interpret the comment:
2.3 kg is the mass of hydrogen which is converted to pure energy in a 50 MT bomb (which is roughly the yield of the Tsar Bomba, the largest bomb ever detonated). Eg. the total mass of bomb material after detonation is 2.3 kg less than the starting mass.
330 kg is the absolute minimum amount of hydrogen which would have been present in the above bomb based on 0.7% of it being converted to energy. But a real bomb would likely contain significantly more due to other inefficiencies.
10,000 kg is the estimate of the actual quantity of hydrogen in the Tsar Bomba.
Also keep in mind just asking how much material is used in a bomb is like asking how long a piece of string is. The above discussion was about a 50 MT bomb, but the largest weapon currently in the US arsenal, the B83, has a maximum yield of 1.2 MT and a total mass of 1100kg (not just hydrogen). Most are smaller than that. The W76, used on submarine missiles, is only 95 kg total with a 0.1 MT max yield.
[removed]
Anyone with half a brain can figure out that Tsar Bomba probably does NOT have 10,000kg of Hydrogen. It doesn't exactly store well..
Someone just pulled a number out of their ass by misinterpreting another statistic, because that doesn't NOT mean you get 5 megatons per 1 metric ton of hydrogen. It means material as a whole...
It wouldn't be hydrogen gas, it would be a solid compound, probably Lithium-6 Deuteride. I think the questioner really wanted to know the total amount of fusion fuel so the estimate seems plausible for that (the whole bomb weighed 27,000 kg).
If they truly only cared about hydrogen atoms it would be less, but it's hard to imagine why someone would care about that specifically.
>how much hydrogen is actually used in a hydrogen bomb
That's not going to be public knowledge, and a lot of those back-of-the-envelope sort of calculations end up making unfounded assumptions, so i's not a surprise that answers differ so wildly.
[removed]
[removed]
[removed]
[removed]
So does all the energy come from the bomb alone. Or is it once the chain reaction starts, does it start to turn other forms of matter into energy as well, eg ( trees houses cars ECT ) been curious about this for a while, thought I'd ask here while on the subject
It almost entirely comes from the weapon itself.
Wow ok, thanks for that
i see, thanks for the clarification!
[removed]
[removed]
The thing is, there isn't really a scientific delineation. Atomic is a historical term that generally referred to fission-only devices, but that was mostly a consequence of fusion having not yet been achieved rather than any technical meaning. Hydrogen bombs generate energy from fusion of hydrogen, hence the name. Pretty much all modern weapons except for some janky 3rd world attempt will contain hydrogen, so that's not really a meaningful term anymore either. A nuclear weapon is anything that uses nuclear (rather than chemical) process to generate energy.
Fat Man was nearly the size of a Smart Car and delivered O(10 kt), while modern weapons are much smaller and with higher yield (though that yield is really more driven by military strategy and availability of materials than it is the ability to get more yield. The truly gargantuan bombs of the 60s have gone out of style because for a variety of reasons.) You could comfortably cradle a modern weapon in your arms, if it wasn't absurdly heavy due to the density of materials used.
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
[removed]
That's typical, but it depends on the design. The Tsar Bomba got over 95% of its 50 MT yield from fusion.
Oh really? That’s neat, I remember going into my nuclear weapons classes with the idea that thermonuclear bombs used fusion as their main energy source, and then quickly learning otherwise so that lesson stuck with me, from what I understood, while fusion is more energy dense, it’s way easier to pack a bunch of fissile material together than it is to get a bunch of fusion material, and to increase yield they just made bigger cores or warheads with more cores, how did they manage it with Tsar Bomba?
A three-stage design: fission -> fusion -> fusion.
The original design had an uranium tamper which would have added another 50 MT from fission, but vastly increased fallout (and likely killed the crew dropping the weapon).
RobusEtCeleritas t1_iznofmg wrote
"Atomic bomb" and "hydrogen bomb" are not really modern terminology, but they're both subsets of nuclear weapons.
But generally speaking, "atomic bomb" refers to nuclear weapon designs which are either fission-only, or boosted fission.
And then "hydrogen bomb" (also known as thermonuclear) refers to weapons which derive a significant amount of their yield from fusion reactions, in addition to fission.
>Moreover, is hydrogen bomb more powerful and destructive than a nuclear bomb?
"Hydrogen bombs" are a type of nuclear weapon. And generally higher yields can be achieved with them than with "atomic bombs" (fission-only or boosted fission), for a given mass of fuel.