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Aerospace Dauterium engines?

  1. May 13, 2010 #1
    Hello all,
    I am an amateur science fiction writer and am currently working on a novel. I am exploring the possibility of deuterium engines and am having a bit of a difficult time understanding some of the research that I have been coming across, as I do not have a very large science background.

    Could anyone take a few minutes to help me out with any of the theory of how this might be possible?

    I appreciate the help.

    C

    Sorry for typo in title.
     
  2. jcsd
  3. May 13, 2010 #2

    FlexGunship

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    Are you talking about a fusion reaction based on deuterium?

    D = H with a neutron

    D + D = He + n + ENERGY

    It's not fundamentally different than any other fusion reaction. Problems with it include the large starting energy. That is to say: you must have a huge reserve of energy in order to just start a fusion reaction.

    The most common is actually deuterium and tritium fusion.

    There are two ways to start a reaction: containment pressure and excitement.

    Containment pressure: by using either inertia containment or magnetic containment, you force deuterium and tritium so close together that the strong nuclear force overpowers the electromagnetic repulsion thus fusing the atoms together.

    Excitement: usually a laser is used to excite an already hot plasma cloud. This causes "incidental" fusion. The fusing of atoms simply by bumping into each other at super high speeds. After that point only containment is needed to continue the reaction.

    Pick your poison... neither is very reasonable. Current research is going in both directions with magnetic containment and laser excitement being used together. Laser to start and containment to sustain the reaction.
     
  4. May 14, 2010 #3
    Thanks very much FlexGunship!
     
  5. May 14, 2010 #4
    In what context do you want to use deuterium engines? For spaceship engines or on the ground?
     
  6. May 14, 2010 #5
    the initial thought was for spaceship engines, but I am intrigued by your idea for ground vehicles.
     
  7. May 14, 2010 #6
    That's based on the latest Cold Fusion battery concept developed by George Miley, a fusion physics & engineering professor who isn't afraid of the 'stigma' around cold fusion. If he's correct a Cold Fusion battery could produce energy for years from the cold fusion effect without recharging with deuterium. Low-energy nuclear reactions, "cold fusion", seem to be produced by deuterium undergoing an inverse into a ultra-dense Rydberg atom form while trapped in a metallic or oxide lattice. The rate of fusion is proportional to the square of its density and ultra-dense deuterium seems to be ~10^6 (a million) times denser than solid deuterium, thus making the fusion rate ~10^12 (a trillion) times higher. At low temperatures the rate is very low, so a trillion times higher isn't a huge improvement BUT the extra-energy needed to initiate fusion also declines with the density, thus the needed energy can be inputted merely by some electric current.

    The very fine details are still vague, but that might be enough for a story. Look up Miley's work online for more.
     
  8. May 17, 2010 #7

    FlexGunship

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    George Miley, although an excellent speaker, is a largely discredited physicist. To his credit, he has at least gone through the trouble of deluding himself before attempting to delude others.

    The problem with cold fusion (as a raw concept, not even discussing the details) is that it requires an atomic change where the strong nuclear force can overcome the electromagnetic force. There are no other mechanisms for fusion. In fact, that is what "fusion" means: "the fusing of two atom nuclei into one." The only force in the universe that holds atoms together is the strong force through the carrier particle called the "gluon."

    So, if you want to bring two atom nuclei close enough to fuse, you have to invest enough energy to "bypass" the electromagnetic repulsion that protons from each nuclei exhibit against each other. Given that energy dissipates in a medium and approached equilibrium, there is a nearly zero chance that suddenly one atom will fuse with another and those chances decrease over time. You'll notice that most of his research requires the use of platinum. If I were to tell you that I could create free energy if you would just give me a pile of diamonds, would you be skeptical?

    Now: here's how you could use a fusion engine in either case (but I want a credit in your story).

    Micro-gravity vacuum: the best thing a fusion engine has going for it is its specific impulse. "Specific impulse" is the amount of fuel that is consumed for a given amount of thrust. This is hugely important for space vehicles since you need to take all of your fuel with you; the more fuel you need, the larger the space ship; the larger the ship, the more launch fuel you need.

    Fusion engines (driven by exhaust) have a very high specific impulse. However, they do not have a very high net thrust. So they are efficient but not powerful. This is the same drawback to the ion engines used by some space probes. Given that it is theoretically possible to create a self-sustaining fusion reaction, the input energy would be a one time investment per firing of the engine. By turning the kinetic energy of the exhaust into electrical energy it is possible to store excess thrust in a battery for starting the next fusion reaction. Please understand: this is the goal of all modern fusion research and it has NOT been achieved reliably.

    Ground vehicles: This application is almost un-usable. In the case of a space ship you have the ability to exhaust your fusion reaction where ever you like to provide propulsion. In a ground vehicle, it's likely that you are not afforded that luxury. The solve this problem you need to find a way to turn the kinetic energy created by a fusion reaction into either electric energy or at least electromotive energy. Given the high investment of energy required to start a reaction, the likelihood of create a vehicle that has so many parasitic losses but is still self-sustaining is very low.
     
  9. May 17, 2010 #8
    Heck, this is Science fiction.

    Back on earth, bombard some atoms. Use lasers to cool some of the fragments, (the free Gluons) and trap them in a Miley Bottle. On your spaceship, when you're ready for some energy, put deuterium into your reaction chamber and introduce a few gluons. They act catalyically, meaning the gluons are released after the fusion reaction so they can cause another pair of deuterium atoms to react. When you slow or stop the reaction by trapping the gluons (with lead nuclei) they are lost. When you run out of gluons inyour Miley Bottle you can keep going until you stop the reaction. Then you can't restart it until you get a fill-up. Like Sandra Bullock in "Speed"... don't stop the bus!

    The equipment required to generate and collect free gluons is too large to fit into a spaceship, and is the first thing a colony builds if it wants to remain civilized.

    You can collect more hydrogen as you go using a magnetic scoop, especially if you're near a sun, but the gluons... You have to stop to get more, but to stop you have to decide Waaaay before you get there. Can you collect enough hydrogen to accellerate at 1 gravity the entire time? That depends on the size of your scoop (so YES!) and how fast you expel the helium nuclei (so YES). Your characters might actually arrive at another star within their lifetime. How much deuterium is there in a vacuum. ZOW! Hardly any I bet. Better make it work on regular as well as premium gas. Good thing it's fiction because I'm having trouble with the neutron count.

    What's that you say? Gluons have wave properties? Trap them with platinum electrons as surface plasmons. That's how a Miley Bottle works, duh! Miley worked for decades before he hit on the idea of using single-crystal platinum electrodes. Everyone learns that in High School.
     
    Last edited: May 17, 2010
  10. May 17, 2010 #9

    FlexGunship

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    Gluons are not colorless particles. They operate under the same rules as quarks. As such, you can never have a free gluon (and certainly not a gluon bottle... though that does sound like something Miley would say).

    Good science fiction is "fiction about science", not "fictitious science".
     
  11. May 17, 2010 #10
    Add some lasers and railguns and call it a "Flex-Fuel Gunship"
     
  12. May 17, 2010 #11

    Borek

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    Not disagreeing with you in general, but I think this statement is not exactly true. In muon-catalyzed fusion nuclei get close enough because their charges are screened by muons. You need energy to create muons, but once you have them they are able to bring nuclei together without any additional energy input.
     
  13. May 17, 2010 #12

    FlexGunship

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    The principle problem with muon-catalyzed fusion is that you need to replace the electron cloud with these matched-charged muons. There's a reason you don't find this arrangement in nature; there aren't angular spin values low enough (they are only available in half-integers) to keep muons at a low enough energy to remain stable in s-orbitals. This is known as the "alpha-sticking" problem. To add to the issue of muons not residing in their orbitals, muons decay after only a few microseconds (yes, long in quantum time... but very very short in practical time).
     
  14. May 17, 2010 #13

    FlexGunship

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    trademarked!!
     
  15. May 17, 2010 #14

    Borek

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    Honestly, I don't get your explanation of "alpha-sticking". My understanding is that it has nothing to do with the spin (after all, muons have exactly the same spin as electrons do), problem is some muons end attached to fusion products - once they do, they are "lost" and they no longer can't catalyze fusion. There is more - fusion is not catalyzed by muons on s orbitals, but by muons on the bonding σ oribitals. But I must admit I am beyond the ground where I feel safe, so I can be wrong.
     
  16. May 18, 2010 #15

    FlexGunship

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    Muons are considerably more massive than electrons. Spin is kind of a misnomer, it is a measurement of angular momentum not of some "spinning speed." As such, a muon with the same spin as an electron has much more energy than that electron. As such, they cannot get to a low enough energy to stay as part of an orbital ("s" is just the easier way of writing sigma since most of us don't have a "sigma" key on our Dvorak-commemorative keyboards). When you solve the eigenvectors for muonic energy you find that you are well outside of common orbitals.

    "Alpha-sticking" refers to the ability of the muon to be retained by the helium nucleus that is generated after the initial fusion event. "Alpha" refers to the helium nucleus (i.e. alpha particle). Where one muon in a hydrogen atom was questionable, two in a helium atom is out of the question.

    Muon-catalyzed fusion is one of those grand voyages the human mind has taken into new areas of physics. But, by the rules that we ise to describe our universe now, it looks more like fantasy than fact.
     
  17. May 28, 2010 #16
    Followed this topic over from the chemistry sub-forum. Just had one comment to make.

    Out of all of the reasons to be skeptical of Miley, the fact he uses platinum in his experiments is the most specious of reasons. Using platinum as a catalyst in a reaction for cold fusion is not the same as using diamonds in generating free energy.

    Platinum is a common metal for capturing hydrogen for use in various organometallic catalytic cycles, as it's good at attaching hydrogen to its surface. Deuterium is similarly able to attach to the surface of the platinum. The idea here is trying to increase the deuterium density on the surface of the metal high enough that it is able to trigger a fusion reaction between the deuterium.

    The trick is how to alter the geometry of the metal surface enough to pack the hydrogen in more densely. One method that's been attempted was pitting the surface of the metal, in the case of that experiment I believe gold was used instead, thus creating small cavities just capable of packing a few dozen atoms of deuterium into it. Pack them in there, dump your starting energy into the system, and hopefully you'll trigger the deuterium in those cavities to fuse.

    So platinum and gold are two good metals for doing this with, because of their affinity for binding hydrogen/deuterium to their surfaces.

    I haven't seen the results yet, but at the March conference for the American Chemical Society, there was a series of lectures on cold fusion, and progress made in the field in the last 20 years (mostly done in secret by well established scientists, as the whole Fleischmann and Pons scandal made it untouchable to funding agencies in the last 20 years).

    So yeah, being skeptical of George Miley is fine, being skeptical because he uses platinum was a catalyst is silly--it's a good starting point when the goal of your experiment is to pack hydrogen/deuterium together as tightly as possible.
     
  18. May 28, 2010 #17

    FlexGunship

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    Hah, wow. I'm really sorry. I didn't mean to imply that was a valid reason for doubting anything. I was actually just trying to make a "cynical joke." You know, like the investment banker's joke: "if you give me one billion dollars I'll make you a very rich man, indeed."
     
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