[djyaz1200]

I wonder if many of the stars in the sky are from groups that almost nailed containment and stability on their Tokamak.

[zamadatix]

The Sun consumes a mass equivalent of a mount Everest worth of hydrogen via fusion to shine for just an hour (or thereabouts, if I did my math right :)). For perspective, this amount of energy is more than enough to power the Earth's current electrical usage for over a billion years.

That's all before getting into how a containment failure doesn't imply "and then everything nearby just started a self sustaining fusion reaction". The confinement itself is a key part of what enables the conditions for the fusion to continue.

[bezmiran]

I am a plasma researcher, though not in the fusion field. Containment and stability are required on tokamaks to keep a plasma burning. Losing either of these will quench the reaction. The best way to control a plasma - magnetic fields, also causes significant instabilities, which is why fusion is so difficult.

[slavik81]

Could you elaborate on how magnetic fields cause instabilities? As a layman, it's not immediately obvious to me why that would be the case.

[cladopa]

No. It just does not make sense from physical rules. Fusion only happens in a very high vacuum, at ridiculous temperatures, with very specific fuel, in the confined space. Just the cooling effect of having oxygen atoms there(in the plasma) stops the reaction, let alone touching anything so cold(millions of times colder and denser) as the walls or the outside gas.

Also stops immediately if no fuel is given.

[thetoon]

Naive question here : how do we expect to collect thermal energy from it if we can't allow it to cool even a little ?

[drdeca]

Seems implausible. The fusion presumably wouldn’t keep going if it breached the walls.

Also, to be bright enough that we would see it from here as a star, I imagine it would require enough material that one might as well just let gravity do the job rather that use a Tokamak?

Maybe there are efficiency gains that are large enough that it wouldn’t actually require as much material as a star? I wouldn’t guess so though.

[JumpCrisscross]

> wonder if many of the stars in the sky are from groups that almost nailed containment and stability on their Tokamak

Different fusion systems. Stars fuse, in general, by statistically overloading the weak force. (The Sun is volumetrically about an order of magnitude less powerful than a human being. Like 200 to 1,110 W/m^3.)

In smaller volumes, e.g. on Earth, we have to break the strong force. This releases more energy, I think. But it also requires temperatures and energy densities far higher than that which stars produce.

Not sure if that strengthens or weakens your hypothesis...

[XorNot]

Strong and weak force don't come into it in either case. Fusion requires overcoming electrostatic repulsion, that's about it. The problem is the Sun is gigantic but it's fusion process is actually very inefficient. To make it practical on Earth we need more particle interactions, and thus higher temperatures, to make it Q>1