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Here's my idea:
You strip the electrons off of xenon, to get the same fuel used in most ion engines. You start the fission. You start with Xenon-129 You (hopefully) end up with tin-121, and some beta particles. The Beta particles start the fission in the other xenon molecules. The Xenon decays to tin-121, and two beta particles (helium nuclei). The heat is used to violently turn water into steam and expel it out the back. It would also be used for power generation.
:arrow: As for methods to start the fission, I was thinking lasers, which would heat them up so they hit each other and broke apart. Are there any other ways?
:arrow: There are two reasons why this is good for mars. 1) the two fuels, Xenon (atm.), and water (permafrost, n. pole, some in air, other plases of which I am unaware.) are available on mars. 2) One of the products is tin. I can imagine that this would be useful somehow. Also, there is the helium which would be good for dirgibles, or some sort of floating device.
-Josh
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This sounds like an interresting idea, but what advantage would it hold over a conventional nuclear reactor? Other than being easier to get the fuel for on mars? I doubt the ammount of tin produced would be significant.
As for starting the reaction, I think this would be very difficult if not impossible. I'm not a nuclear physicst, but in a conventionally fueled reactor a suffent mass has to be brought together for it to go supercritical. I suspect this has to do with density too, which isn't a problem if you are using a dense metal like urainum, but with a gas, the pressure would have to be enormous, no?
You mentioned using lasers to start fission, but I have a hard time seeing how that would work, a laser ciertenly is not going to have enough energy to break apart an atom's nucleus and release neutrons, unless we are talking fussion style pulsed lasers, in which case you might as well just do fusion. Probably some fast neutron sorce would be more practical- don't some radioactive isotopes emite neutrons.
here's something that may be of intresst as well- fision in a plasma
http://en.wikipedia.org/wiki/Plasma_focus
edit- sorry the link is a neutron source from fusion not nuclear fission
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I think this is a facinating idea, and I looked up a bit more on Wikipedia. I don't think that Xenon will work, as what you are discribing is alpha decay from Xe to Sn, which, while possible, will not happen very rapidly given the long half life of Xenon isotopes. I haven't seen anything to sugest that this can be sped up by adding energy or by any other means, but correct me if I'm wrong.
Fission of Xe isn't theoretically impossible as it is more than twice as heavy as Fe56 (the top of the binding energy curve, and most tightley bound element) so maybe it could be split, but I have no idea how this could be acomplished, obviously neutron bombardment isn't going to be enough as that only works for Uranium and heavier elements. Fusion takes huge temperatures and pressures to overcome the electrostatic repulsion between the nucluses, but I don't know the theory behind fission.
Perphaps there are some advantages to a uranium fission reactor based on the Dense plasma focus. Mined uranium could be converted to uranium hexeflorine and placed in a low pressure vessel with the plasma focus. The capasitors are discharged and it is ionized and compressed as a plasma so that at the focus it goes super critical. The amount of uranium needed would be very low, and it could be scaleable to any size, see the link in previous post. The main asset would be that the energy could be converted directly into electricity as the end product would be an ionized gas that could be fed though a MHD genorator as this group wants to do, though running as a fusion power sorce. http://focusfusion.org/log/index.php/site/toc/what/
Another possibility may be to use it in deep space as a mini orion drive since it should be scaleable, so no shock absorbers needed. Also, the uranium may not have to be enriched. I'm not sure this is possible, is the density great enough to go supercritical, will the uranium hexeflorine simply breack down, will it break even energy wise, but it dosen't seem totally impossible.
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Opps, I guess I was wrong, you can stimulate fission with external sources like lasers, but aparently it doesn't break even even when you use uranium.
google photofission
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Americium would work, but it goes super critical at a very small mass, has all the normal problems with radoactive waste, and won't genorate any net energy because it is produced from urainum with neutron bombardment, so it'd probably only be useful on some sort of exotic probe engine. http://en.wikipedia.org/wiki/Americium
Radon is an even numbered element, which if I remember correctly, makes it very hard to fission. It also would have the normal problems of radioactive decay with the products http://en.wikipedia.org/wiki/Radium
I think a better canidate might be the photofission of lithium, which does yield net energy because its protucts are helium-4 and hydrogen-3, helium-4 being more stable. From this chart http://en.wikipedia.org/wiki/Image:Bind … otopes.svg it looks like it might yield more energy per mass than uranium, so the whole process migh break even. Hygrogen -3 would be the only radoactive waste, which shouldn't be too bad as it has a half life of 12 years, and vented into the upper atmosphere it's not going to hurt anyone.
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That's a good idea. Also, if the H-3 is saved, it could surely be used for something. Fission? H-3+He-3 = Li-6 Here are some other ideas of mine.
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Maybe N-14? It's readily available, in large quantities on both earth and mars (more on earth). It decays into either Li-7 and Be-7, which undergoes electron capture and gamma decay, and ends up as li-7. It might also decay to Li-6, and Be-8, which I don't know how it decays. The only stable isotope of berillium is Be-9. ____________________________________________________________
Also, maybe Be-9 itself. It would probably decay to He-5 and He-4. He-5 decays by Alpha particle emission in a very short amount of time. The Neutron could be what is used to cause fission elsewhere. The Neutron will make be-9 into be-10, which will fission to He-5 and He-5, releasing more neutrons. Is it supposed to go like that? two neutrons released for every one that hits something? Control rods will be needed. Apparently the binding energy is ~6.5 MeV. I think Lasers (specifically HEX [high energy X-ray] lasers), can achieve that. If not, neutron bombardment will work, but maybe a particle accelerator, or chemical means. What do you think?
-Josh
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Americium would work, but it goes super critical at a very small mass, has all the normal problems with radoactive waste, and won't genorate any net energy because it is produced from urainum with neutron bombardment, so it'd probably only be useful on some sort of exotic probe engine. http://en.wikipedia.org/wiki/Americium
Carlo Rubbia advocated Americium for spacecraft.
His life:
http://en.wikipedia.org/wiki/Carlo_Rubbia
http://en.wikipedia.org/wiki/Energy_amplifier
http://www.spaceflightnow.com/news/n0101/19marsnuclear/
http://www.springerlink.com/content/l48936x64441n826/
http://www-istp.gsfc.nasa.gov/stargaze/StarFAQ10.htm
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