Author Topic: Advanced Ionisation-Methods  (Read 1939 times)

Offline Port

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Advanced Ionisation-Methods
« on: 01/03/2013 12:48 pm »
So i stumbled upon this
http://phys.org/news/2012-11-ionization-x-ray-laser-shells-electron.html

and while reading it i started to think about what charge the Argon-Atoms ionized in a Hall-Thruster usually have. Wiki states that they are most commonly (ofc depending on the voltage used) PLUS_1 (silly autocorrect) (or 20% +2) so statistically +ONE.4(silly autocorrect!!).
Since the forcce exhibited by a Hall-Thruster is Coulomb-correlated the thrust should scale linear with the ionisation of the fuel.

So of course +36 like the linked achievement is as unpractical as remakable but since it would "only" take a +10 Charge to 8-fold the thrust generated by a electromagnetic thruster at some point a downscaled approach could be feasable exploiting the new discovered resonance-effect.
I guess that the usual approach is to higher the charge of the kathode that accelarates the Argon-Kations but at some point this can't be practical anymore (discharges taking place at too high-volts etc.).

My question would be if there is a size of a thruster where a laser-driven fuel ionisation would make sense thrust/weight-wise.
My gut tells me yes, but this could be way beyong practical size..

Question would remain if it is a good idea to build a massive ion-drive or just cluster some small ones together, as it is today most opinions i've picked up in this forum tend to the cluster-method for redundancy.
But there has to be an upside of building bigger ion-drives and this could be one of them, at least it could be a way to considerably boost the thrust generated by ion-drives.

Offline simonbp

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Re: Advanced Ionisation-Methods
« Reply #1 on: 01/03/2013 07:13 pm »
Hmm.... If you can ionize a noble gas that well, you kinda don't need an EM field; just let it recombine in a combustion chamber with a standard physical nozzle and you've got a pretty good rocket.

But if you insist on a magnetic nozzle, something like what VASMIR uses would probably be more appropriate, just replacing the helicon RF generator with the X Ray laser setup.

http://en.wikipedia.org/wiki/Variable_Specific_Impulse_Magnetoplasma_Rocket
« Last Edit: 01/03/2013 07:13 pm by simonbp »

Offline BobCarver

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Re: Advanced Ionisation-Methods
« Reply #2 on: 01/04/2013 01:26 pm »
@simonbp How would you store this "fuel" in a rocket? Some kind of magnetic bottle?

Offline Enthalpy

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Re: Advanced Ionisation-Methods
« Reply #3 on: 01/06/2013 07:24 pm »
Ejection speed is already high with ion engines. If desired, it could be increased further just with a higher acceleration voltage. This is not generally sought, because electric power is the limit of these thrusters, more than the consumption of propellant.

More: the energy wasted in ionizing the propellant is a very serious limit, which explains why propellants are chosen heavy and easy to ionize. Removing more electrons would go in the wrong direction.

Offline BobCarver

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Re: Advanced Ionisation-Methods
« Reply #4 on: 01/06/2013 09:03 pm »
Ejection speed is already high with ion engines. If desired, it could be increased further just with a higher acceleration voltage. This is not generally sought, because electric power is the limit of these thrusters, more than the consumption of propellant.

More: the energy wasted in ionizing the propellant is a very serious limit, which explains why propellants are chosen heavy and easy to ionize. Removing more electrons would go in the wrong direction.

On the other hand, if you could store highly-ionized fuel, the recombination with electrons to produce a neutral atom should be highly energetic. If that energy could be directed, there's a potential thrust mechanism.

Offline simonbp

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Re: Advanced Ionisation-Methods
« Reply #5 on: 01/07/2013 04:00 am »
No, you wouldn't store it ionized, that would be silly. You ionize it (i.e. heat it up to be a plasma) and then immediately eject it out of the vehicle, cause it's a it's a rocket.

With a plasma so hot, I'd be wary of a grid-based ion engine, as it would erode fast. A "cleaner" design like VASMIR would have much less erosion, and a Hall thruster somewhere in between.

Offline Enthalpy

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Re: Advanced Ionisation-Methods
« Reply #6 on: 01/11/2013 02:57 am »
...on the other hand, if you could store highly-ionized fuel, the recombination with electrons... potential thrust mechanism.
How do you store them?

The most advanced research takes presently a big room to store a dozen ions. The apparatus that keeps them weighs 1028 times more than the ions and wastes like 1026 times more energy than the inital ionization.

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