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Ionisation rate

  1. Dec 25, 2015 #1
    I need to ionise lots of particles quickly. Upwards of 1kg /sec. What's the best way of doing this? I'd consider pre ionised solutions boiling etc.

    Thanks
     
  2. jcsd
  3. Dec 25, 2015 #2

    mfb

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    That needs megawatts of power...
    Where do you want that ionization rate, for how long, and why?
     
  4. Dec 25, 2015 #3

    jambaugh

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    What is the material you wish to ionize? (is it a metal? a gas? light element? heavy?) Do you care about temperature? Do you need to ionize and accelerate the ions or just generate a plasma? Or do you rather want to ionize it at room temp?

    In short what is your application?

    Doing the math you're talking 10 to 100 thousand amps of current to ionize 1kg/sec. You are also talking about ionization energy per sec of 100s of kilowatts to 1.3 megawatts depending on the element and assuming 100% efficiency. Multiply by at least 10 for even the most optimistic achievable efficiency levels.
     
  5. Dec 25, 2015 #4
    Thanks. I want a beefed up ion thruster. I don't understand why they're so low powered. Can't you just increase the mass flow rate and design it a bit more like a particle accelerator to increase the momentum generated?
     
  6. Dec 25, 2015 #5
    So basically I want 1 kg per sec coming through any way possible for a long period of time to launch vehicles into space
     
  7. Dec 25, 2015 #6

    jambaugh

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    The devil is in the word "just".... it is a major bit of engineering. Again you must appreciate the currents you must produce... and at the ionization voltage of the material this will be a lot of watts.

    Look at the current ion rocket designs in NASA's portfolio or just google the topic to see what's out there. If I could do better I'd be selling it to NASA now. If you want to scale it up, put two, four, 10, 1000, ... such engines on your vehicle and figure how to power them.
     
  8. Dec 25, 2015 #7

    mfb

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    Ion thrusters are limited by power. It is not that hard to design an ion thruster that uses 1 MW - but where do you get 1 MW of power from?
    Using 1kg/s of propellant with typical ion thruster Isp of 4000 s would need a power of 800 MW (at 100% efficiency). That is a full-scale nuclear reactor block on Earth. And it does not scale well: that ion thruster can only lift 4 tons to space, negligible compared to the weight of such a massive reactor.
     
  9. Dec 25, 2015 #8
    Ok. What about pre ionised fuel? Like a compressed gas of h+ ions etc. Can you make and store a few tons of the stuff in your rocket?
     
  10. Dec 25, 2015 #9

    Vanadium 50

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    Tons? Tons?

    I think this thread needs to become a B. One ton of ionized hydrogen has a charge of 50 billion coulombs. Putting this much charge in such a small space would take - and immediately release - the energy of a trillion nuclear bombs. This is pure fantasy.
     
  11. Dec 25, 2015 #10

    mfb

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    In addition, ionization doesn't solve the energy problem. Accelerating the stuff is the main point, and needs more energy than any non-nuclear fuel can store. Chemical rockets are quite efficient in converting chemical energy to thrust. To get higher exhaust velocities, you need a different power source - solar or nuclear power. And a lot of time, because both don't deliver the power densities a classical chemical rocket can give.
     
  12. Dec 25, 2015 #11

    ZapperZ

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    I think when people come up with these schemes, they often forget to evaluate this factor, i.e. the efficiency of the scheme. Accelerating particles using a conventional accelerator is not the most efficient thing in the world. Couple this with the inefficient ionization process, then one is burning up more fuel to do this than the tried and true propulsion that we have already.

    People forget that just because it is possible, it doesn't mean mean that it is the BEST thing to do. The economics and other factors are also involved.

    Zz.
     
  13. Dec 25, 2015 #12
    I got ideas about accelerating the stuff ;)
    My only issue is getting the rate of ionisation up to 1kg/sec
     
  14. Dec 25, 2015 #13

    ZapperZ

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    It appears as if all the stuff that was brought up about the efficiency (or lack of it) of the scheme just fell on deaf ears!

    Zz.
     
  15. Dec 25, 2015 #14
    Can anyone suggest, if you were to do it, what would be the best method for that many particles?
     
  16. Dec 25, 2015 #15

    Vanadium 50

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  17. Dec 25, 2015 #16

    Dale

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    The method is no mystery. Simply get a large anode, a large cathode, a very high voltage, and a lot of ionizable gas. The method is not mysterious, it just requires a lot of power as has been mentioned above.
     
  18. Dec 25, 2015 #17
    Ok cheers.
     
  19. Dec 25, 2015 #18
    I really had no idea about this, whether you should heat it or shoot it with electrons or photons so thanks
     
  20. Dec 26, 2015 #19
    What stops the ions reacting with the cathode?
     
  21. Dec 26, 2015 #20
    Can you coat it?
     
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