A Lunar Colony

[chriscdc]

I just read an interesting article on the space review.<br /><br />http://www.thespacereview.com/article/536/1<br /><br />The most interesting point is the sheer quantity of He3 on the moon. Over its life it would have been hit by over 500million metric tons. Only 40 metric tons of which would have provided enough energy to power the US for all of 2005. Considering how easy it is to get the He3 out of the regolith (heat to 700 degrees C, collect gas and then cool and collect the last gas to condense) this cold be a real alternative.

 

[mlorrey]

He^3 is overhyped. While it is true that it would be a clean form of fusion, the heat and pressure needed for that form of fusion is many times greater than anything we are capable of now or will be some time into the future. Think about it: stars do not start fusing Helium until after they've burned up their hydrogen, contracted their cores, and heated up many millions of degrees hotter than before. This automatically means that He fusion of any kind is much harder than H fusion. He^3 may be easier than other forms of Helium, but it cannot be easier in any way than any form of Hydrogen fusion.<br /><br />We ought to be focusing on deuterium fusion exclusively. It is the easiest, and happens in simple brown dwarfs.

 

[chriscdc]

While D-D fusion does produce protons, they have far lower energy than the protons emitted by D-He3 fusion. It is not actually that difficult to accelerate ions to the required energy levels for fusion. If the equipment required to accelerate the particles becomes more efficient, and the ability to get energy out of the protons improves, then it should be rather easy to fuse anything that releases protons considering the huge differences between the energy input and output.<br /><br />Of course you still need a way to make sure the accelerated ions hits a target ion.<br /><br />Actually how can you get energy out of a proton generating reaction in a torus reactor? I can understand the neutrons passing through the reactor wall to a lithium blanket and heating up, but won't a proton just hit the wall and stop? Wouldn't any devices to absorb the energy be damaged by the conditions inside the torus.

 

[mlorrey]

What is a proton? It is a hydrogen ion. D-D fusion should produce He ions. When a neutron strikes the lithium blanket, how does it generate heat? From the impact, right? A proton impact will not only generate heat, it will generate charge in the wall of the reactor, the right charge needed to repel D ions and keep them concentrated in the plasma core.

 

[chriscdc]

Actually the neutrons cause the lithium to undergo fission. One advantage of this is that is produces tritium, it also produces another neutron that can go on to hit another lithium atom etc. So in reality the torus is just one great big neutron source rather than being a break even reactor in itself. Don't get me wrong, I fully support ITER and wish the politicians would give it the resources that it needs.<br /><br />Now neutrons will cause physical damage over time to the reactor walls, but so will protons flying everywhere. The protons have enough energy to fuse with the atoms in the walls. Also the protons electric field will damage the reactor walls anyway. Imagine what would happen to a metal if a proton with several MeV passes through it.<br /><br />Also as it would be stopped by the walls of the reactor, the walls of the reactor will get hot rather than a lithium blanket, which would cause a lot of problems. For example the protons could cause ions to be emitted from the wall and so poisoning the plasma. <br /><br />The behaviour of plasmas are not as simple as giving the walls a positive charge. The Plasma is kept compressed due to magnetic fields interacting with an induced current running through it. Adding a positive charge to the walls would probably have little effect.

 

[mystex]

For those of us who aren't to well versed in nuclear physics could you list a resource that we could go to to beef up our understanding?

 

[chriscdc]

I'm not hugely versed in nuclear physics (don't ask me to do the maths for one of these things), but what I do know I've picked up over time. <br /><br />However you could look up ITER, which is one of those international projects that would be a huge benefit for the country that builds it, but no one country is willing to pay the price (grumble, short sighted politicians, grumble).<br /><br />Wikipedia is normally a good starting off point.

 

[mystex]

Thanks for the info I'll definetly check into it. As for the politicians well unfortunately we haven't had any lately with the long sighted vision of our founders. More is the pity. Reading a great sci fi book along those lines called Fallen Angels you might like. Anyways thanks for the pointer.

 

[spacester]

How much do you think a lunar version of that reactor would mass? IOW, what do we launch it on? <div class="Discussion_UserSignature"> </div>