Cold Fusion -- It's BaaaAAAaaack...

[BlackCat]

What's your assessment on fusion bombs for earth clearing, Kitty? Cut a hole through Nicaragua?

It would make more sense to cut a hole in the Atlas Mountains.

[TCO]

porquoi?

[BlackCat]

Why cut a hole through Nicaragua ? Panama is just a little to the south.

Cutting a hole in the Atlas would turn sahara into what it was before Atlas rised.

[TCO]

I think the Sahara is above sea level?

[TCO]

But we could do some changes in Imperial County...

[BlackCat]

I think the Sahara is above sea level?

Yeah, it is , but a hole in the Atlas will let atlantic moisture get into sahara wich will seriously alter the climate

[Kuciwalker]

So are we talking core-of-the-Sun type temperatures, or is there any hope of achieving fusion at something a little more attainable?

Note that positive-energy fusion reactions (i.e. ones that got more energy out than was put in) have been repeatedly demonstrated in controlled conditions.

[dannubis]

but unfortunately only for a few milli seconds... stupid plasma and its stupid physical properties

[Kuciwalker]

Actually, in these reactions those properties are considered extremely useful.

[Elok]

? I thought the Sahara was formed by massive overgrazing? Or at least, that's how it supposedly got to its present size.

[KrazyHorse]

So are we talking core-of-the-Sun type temperatures, or is there any hope of achieving fusion at something a little more attainable?

D-D fusion has to overcome a barrier of 40 keV

Room temperature (300K or so) is ~1/40 eV and it scales linearly with temp so the naive estimate for D-D fusion is 300K * (40000/(1/40)) = 480 million degrees

D-T fusion is about 10 times lower (50 million degrees)

Now, both of these numbers overstate the problem by at least an order of magnitude. I'm not going to bother running through the calc myself, but there are two effects which would lower the required temperature:

1) At a given temperature there is a range of particle energies, with decreasing numbers the further away from the peak that you get. So at 5 million degrees the peak may be at 400 eV (note that this is only an estimate; what matters is the average center of mass energy of two colliding particles and this will be some order one multiple of 400 eV) but there will be particles with energy 40 eV and particles with energy 4 keV, only less of them

2) There will be some quantum tunnelling by particles which naively have less than the required energy to cross the coulomb barrier

So, even if the average collision does not have enough energy to overcome the coulomb barrier, some smaller fraction of collisions WILL. Even at room temperature, SOME fusion will happen, only at a ridiculously low rate.

[KrazyHorse]

What's your assessment on fusion bombs for earth clearing, Kitty? Cut a hole through Nicaragua?

Why? You don't like Panama?

[dannubis]

Actually, in these reactions those properties are considered extremely useful.

Yes, for the reaction itself... However, it is notoriously difficult to stabilize the plasma ring.

[The Mad Monk]

Where does He3 fit into all this?

[KrazyHorse]

It's one of the possible products of D+D fusion, as well as being a possible reagent for other fusion processes.