Critical mass for nuclear fusion

[Methavix]

Hello, can you please confirm this statement "Nuclear fusion does not require a minimum mass to occur (critical mass), which is instead a characteristic limit of fission. So you can make small fusion bombs as much as you want."?
Thanks!

 

[anorlunda]

It is true that there is no critical mass for fusion. But fusion bombs use fission bombs to trigger the reaction, so you need a cricitcal mass fission bomb anyhow.

https://en.wikipedia.org/wiki/Thermonuclear_weapon

 

[Methavix]

Thanks! In this case we are considering the ignition with a laser or relativistic electron beam, so is it true that we can have a micro-bomb according to you?

 

[anorlunda]

we are considering the ignition with a laser or relativistic electron

Who is we? It sounds like you're working on a SF story, is that right?

In theory, the answer to that question is yes. But in practice nobody has come even close to making that succeed.
One idea for a fusion power plant was to implode fuel pellets the size of a grain of a sesame seed. It is still a dream, not reality.

 

[Methavix]

Oh yes, I didn't mean that I'm working on this kind of fusion bomb :D I only meant that I am considering this system of ignition in the reasoning I am doing with other people.
Thanks for your help!

 

[berkeman]

So you can make small fusion bombs as much as you want

Have you read about Inertial Confinement Fusion with lasers? You should look at the size of the target spheres and read how much energy is released per shot. I don't know if that qualifies as your "bomb" or not. Also, I guess you need to include the size of the building housing the laser system in the "size" of the "bomb"...

https://cdn.arstechnica.net/wp-cont...plifier_at_the_National_Ignition_Facility.jpg

 

[Methavix]

Thank you! Actually, I'm considering this kind of bombs for advanced space propulsion systems, not on the Earth. Anyway thanks for your suggestion.

 

[anorlunda]

Thank you! Actually, I'm considering this kind of bombs for advanced space propulsion systems, not on the Earth. Anyway thanks for your suggestion.

Maybe you can modernize the concept of Project Orion. https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

 

[rootone]

For fusion reactions there has to be a sufficient quantity of very tightly confined plasma.
Not that much though, less than a gram will do the trick, IIRC

 

[Aufbauwerk 2045]

This is an interesting story about micro-scale fusion.

https://engr.source.colostate.edu/i...-scale-nuclear-fusion-with-record-efficiency/

 

[Aufbauwerk 2045]

Maybe you can modernize the concept of Project Orion. https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

Winterberg has done some work along these lines.

https://www.nextbigfuture.com/2014/01/winterberg-reinvents-project-orion.html

http://vixra.org/abs/1310.0225