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RobusEtCeleritas t1_izopyu6 wrote

Reply to comment by zerda_EB in What is the difference between atomic, nuclear and hydrogen bombs? by something-stupid2134

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.

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bmyst70 t1_izotmhi wrote

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.

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ChemicalRain5513 t1_izoxpk0 wrote

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.

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Abdiel_Kavash t1_izp2uhh wrote

If it can penetrate through buildings or armor, what makes it "stop" inside of a human?

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Ishana92 t1_izp3wmh wrote

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.

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Abdiel_Kavash t1_izp49gc wrote

Ah, I see. I interpreted "penetrating" as "passing through with relatively little interaction", not as "bullet penetrates a window".

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mfb- t1_izoy1pu wrote

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.

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KauaiCat t1_izr2m74 wrote

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.

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