Cold fusion, Would this work?

[Pigbear]

Theoretically if you had enough pressure, the atoms would still compress together right? Eventually, one of them would collide into another and fuse, yes? Well. If that is the case then cold fusion is as simple as pressure, once one fuses a chain reaction would happen. Correct me if I am wrong.

[Genius Evil]

It's theoretically possible, but you need a ridiculous amount of pressure. 10,000+ atmospheres IIRC. Not to mention that whatever you're compressing would become plasma before fusing, so it would have to be done magnetically. Several attempts have been made; they all failed. Force would have to be applied in a perfectly uniform manner, or the plasma would escape.

[Awaras]

Theoretically if you had enough pressure, the atoms would still compress together right? Eventually, one of them would collide into another and fuse, yes? Well. If that is the case then cold fusion is as simple as pressure, once one fuses a chain reaction would happen. Correct me if I am wrong.

That's what happens in the cores of stars basically... If you compress something to the pressures required for fusion, it WILL heat up, so all you get is plain old regular fusion, not cold fusion.

[Pigbear]

But you don't need the heat in the first place do you?

[Stochasty]

Heat makes fusion easier, because the faster the nuclei are moving with respect to each other the easier it is to overcome the potential barrier, but it is not per se necessary. That said, if your intended fusion mechanism is simply "increase pressure until fusion," bleeding the heat out of the system as the pressure increases (because it will heat up as you pressurize it) is silly and counter-productive.

The point of "cold" fusion is not (necessarily) that the fusion itself takes place at low temperatures. It's that the medium in which the fusion reaction happens is low energy/low pressure (and therefore does not require exotic confinement mechanisms).

[lajoswinkler]

Pressures of more than 300 gigapascals (101325 pascals is one atmosphere) have been made in laboratories without any fusion happening so the answer is "might needs moar boosterz", and it indeed does, but ridiculous, humongous amounts of pressure at room temperature, such pressures that we will never ever recreate them.

Instead you can actually use much lower pressures if you simply heat the atoms to rip them off their electron clouds which are really great when it comes to keeping nuclei from joining together.

Edited October 2, 2013 by lajoswinkler

[WestAir]

Can't you just use a fission explosion to compress the atoms you want to undergo cold fusion?

[Stochasty]

That's how fusion bombs work, westair, so the answer is "yes." However, I question your definition of "cold" if the process involves a fission bomb.

[WestAir]

That's how fusion bombs work, westair, so the answer is "yes." However, I question your definition of "cold" if the process involves a fission bomb.

Well, it started off cold.

[lajoswinkler]

Dying in a house fire is also dying of cold... it started as cold.

Why are people not using the search engine? We've had the very same discussion few days ago. Gaah, I pity the poor mods who have to deal with this every day.

[Seret]

(because it will heat up as you pressurize it)

I think this is the point the OP is missing. Pressure and temperature are related. Compressing something enough to achieve fusion implies also raising the temperature above what could be considered "cold" fusion.

[jwenting]

But you don't need the heat in the first place do you?

pressure is heat, heat is pressure. The fallacy in your assumption is that one can exist without the other.

[jwenting]

Can't you just use a fission explosion to compress the atoms you want to undergo cold fusion?

They'd no longer be cold

And yes, that's how a fusion bomb works, basically.

[magnemoe]

A lot of fission tries are ongoing, using things as shock waves or having two beams of atoms intercept. The beam method is cold in a sense however the atoms contains a lot of kinetic energy.

[-Velocity-]

pressure is heat, heat is pressure. The fallacy in your assumption is that one can exist without the other.

Wow, no, heat is not pressure! Heat is GENERATED by putting things under pressure, but that heat could be bled away. But as already stated in the thread, if your goal is nuclear fusion, then removing the heat from the system is counter-productive.

To slowly increase pressure on something, while keeping it at room temperature, and have it eventually undergo nuclear fusion... wouldn't that material have to approach neutron star densities? A big part of what allows high temperature fusion to take place is that the atomic nuclei are very hot, moving around at very high velocities, and when two of them come close together, the velocities are so high that electrostatic repulsion cannot slow the nuclei down or deflect them away fast enough before they get close enough for the strong nuclear force to overcome electrostatic repulsion. I think I also heard that quantum tunnelling plays a role too- the nuclei don't have to be as close to each other, as they can tunnel past the electrostatic barrier and into the small region where the strong nuclear force takes over.

So yea, wouldn't you need like nearly neutron star densities to make stuff under pressure but at room temperature to undergo fusion?

Edited October 2, 2013 by |Velocity|

[rkman]

cold fusion is as simple as pressure

Stars do fusion by means of pressure. But getting enough pressure is not simple, nor will it be cold.

[-Velocity-]

Stars do fusion by means of pressure. But getting enough pressure is not simple, nor will it be cold.

No, heat plays a major role too.

[GJames]

No, heat plays a major role too.

But that heat comes about from nuclear fusion, which was started by the massive pressures that you get in a star.

IIRC, originally cold fusion was about fusion at normal-ish temperatures and pressures, as soon as you introduce either one of them you start affecting the other (higher temperatures = higher pressures).

[lajoswinkler]

So yea, wouldn't you need like nearly neutron star densities to make stuff under pressure but at room temperature to undergo fusion?

Yes. Remember white dwarfs? No fusion happens despite incredible pressures, and the temperatures aren't that bad, either.

[-Velocity-]

But that heat comes about from nuclear fusion, which was started by the massive pressures that you get in a star.

IIRC, originally cold fusion was about fusion at normal-ish temperatures and pressures, as soon as you introduce either one of them you start affecting the other (higher temperatures = higher pressures).

No! The heat initially comes from compressing the gas down to extremely high pressures and densities (Charle's Law), and gravitational accretion. Without the heat, the fusion would never start up when it does, and probably not happen in the manner we are familiar with (maybe, the star would just explode when it reached a critical density and the first fusion reactions started, creating heat for more fusion reactions, creating yet more fusion reactions from the heat, etc, in a runaway reaction that would destroy the star).

The heat in the interior of a protostar is VERY critical to getting the first fusion reactions going.

[Ralathon]

No! The heat initially comes from compressing the gas down to extremely high pressures and densities (Charle's Law), and gravitational accretion. Without the heat, the fusion would never start up when it does, and probably not happen in the manner we are familiar with (maybe, the star would just explode when it reached a critical density and the first fusion reactions started, creating heat for more fusion reactions, creating yet more fusion reactions from the heat, etc, in a runaway reaction that would destroy the star).

The heat in the interior of a protostar is VERY critical to getting the first fusion reactions going.

What you describe reminds me of a Helium Flash You get some ridiculous numbers when that happens. The star fuses about 4% of its core helium supply in a matter of minutes. Surprisingly enough this doesn't destroy the star.

[-Velocity-]

What you describe reminds me of a Helium Flash You get some ridiculous numbers when that happens. The star fuses about 4% of its core helium supply in a matter of minutes. Surprisingly enough this doesn't destroy the star.

From what I remember about helium flashes though, I thought I remember reading somewhere that the helium flashes can help contribute to the loss of the outer layers of the red giant and ultimately the formation of a planetary nebula? Honestly, I'm not sure, the end stages of intermediate mass stars are very complex and I have a hard time getting it all straight in my head. The end of supermassive stars are so much easier to understand, in comparison.

[DerekL1963]

Yes. Remember white dwarfs? No fusion happens despite incredible pressures, and the temperatures aren't that bad, either.

That's because white dwarfs don't produce sufficient pressure and temperature to kick off fusion in the materials it's core is composed of.... they're too small. However, those same materials are happily fused in the cores of larger stars, until you reach iron. When iron starts fusing, the real fun begins.

[lajoswinkler]

That's because white dwarfs don't produce sufficient pressure and temperature to kick off fusion in the materials it's core is composed of.... they're too small. However, those same materials are happily fused in the cores of larger stars, until you reach iron. When iron starts fusing, the real fun begins.

Yes, but we're talking about room temperature. You'd need stupendous pressures to overcome the "electron pressure" at low temperatures.

[magnemoe]

Yes, but we're talking about room temperature. You'd need stupendous pressures to overcome the "electron pressure" at low temperatures.

Now add that if you managed to get an huge mass of degenerated hydrogen and fusion starts you have an problem, as the fusion increases temperature you will get more and more fusion until the thing rip it self apart or explode, pretty much like an critical mass of plutonium.

Fusion is actually pretty rare in stars or more precise: the number of fusion reactions for cubic meter/second is surprisingly low. the huge size of the stars make up for it.