Quote:
Originally Posted by DataPacRat
By the by, does anyone know offhand how much conventional explosive is used in a typical A-bomb, to compress the fissionables to criticality?
Also, while I'm thinking about it, how about how much gamma-emitting metastable isomer do you need to have before throwing in some tritium or other fusables would start adding to the explosive force?
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The thing with TL7-8 plutonium core bombs is that what you're doing with the explosives is changing the shape of the plutonium from a hollow sphere to a non-hollow sphere as quickly as possible. The average density of the hollow spehre wasn't high enough for neutron chain reactions but the non-hollow sphere is-until the energy released blows the sphere apart.
I'm being very cautious about using the word "solid" because after the explosives go off the sphere is a liquid metal until it's a rapidly spreading plasma. Indeed, I think the last componets of a nuclear bomb to do their job in a solid form are the wires that lead to the detonating caps.
In Gurps terms the explosion probably does more damage than the plutonium's HP but less than -10 x that HP. It's my interpretation that at -10xHP you've pslattered the plutonium rather than neatly compressed it. For the masses traditionally used for critical mass of Plutonium (5 to 6 kilos or 11 to 13 lbs) that's 18-20 HP. That would mean we''re talking about the equivalents of 0.75 lbs of TNT something around 25 lbs.
I warn you that this is all Gurps theory. No real nuclear secrets were divulged.
That's fission but you need neutrons to initiate fission. That's why you had to use plutonium which is a natural source of neutron radiation. To intiate fusion you have to have heat. So schemes to initiate fusion with gamma (or even x-rays) have problems. You need that high energy EM radiation to be absorbed by something and turned into heat that way.
The reason contemporary fission-fusion-fission bombs work as well as they do is that neutrons->fission->heat->fusion thing and the fact fusion (the D--T and De-De reactions specifically) puts out 80% of its' energy in the form of neutrons and those neutrons then ignite another fission stage.
Pure fusion devices.with no fission have problems. see the "National Ignition facility" for an example of the scale you have to work on.