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Ion Thrust

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#1 Brother Orpheo

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Posted 01 March 2014 - 04:25 AM

Out of curiosity, I decided to do some investigation into the properties and function of ions and ion thrusters. In simple terms, ion thrusters are employed for low power course corrections and orbit maintenance for satelites.


One thing that stood out was that ion thrusters function best in ion-free environments, such as the void of space. So I started (brief) research into ion saturation in earth-like atmospheres, and stumbled upon greenhouse gasses. Greenhouse gasses, particularly the water vapor within them, are saturated with ions. This would suggest ion thrusters would function sub-optimally on "jungle" worlds. 


EDIT- Mercury, Venus, and Titan also have ion-saturated atmospheres.


Now I know SW is science-fantasy, and I'm perfectly within GM fiat to say (or assume) ion thrusters simply function as a matter of course, but I'm looking for an alternative thrust option for ships while in atmosphere.


Examples of ion fuel are:

  • Propellants

    Ionization energy represents a very large percentage of the energy needed to run ion drives. The ideal propellant for ion drives is thus a propellant molecule or atom that is easy to ionize, that has a high mass/ionization energy ratio. In addition, the propellant should not cause erosion of the thruster to any great degree to permit long life; and should not contaminate the vehicle.

    Many current designs use xenon gas, as it is easy to ionize, has a reasonably high atomic number, an inert nature, and low erosion. However, xenon is globally in short supply and very expensive.

    Older designs used mercury, but this is toxic and expensive, tended to contaminate the vehicle with the metal and was difficult to feed accurately.

    Other propellants, such as bismuth, show promise and are areas of research.


Anyone have some suggestions for liquid/solid fuels for mass reaction, for thrust within an atmosphere's envelope? I think it's worth considering, given some GMs/play groups track fuel (at least for refueling costs), and it can add a level of technical gizmoism to tech-minded characters.


Electrostatic Ion Thruster: http://en.wikipedia....:Ion_engine.svg


Electromagnetic Ion Thruster: http://en.wikipedia....ll_thruster.svg


EDIT- Mercury as an ion fuel puts me in mind of the possibility of some alien cultures utilizing "dirty" ion engines. Basically toxic-emissions thrusters that might result in higher docking fees/taxes.

Edited by Brother Orpheo, 01 March 2014 - 05:10 AM.

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#2 MKX



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Posted 01 March 2014 - 08:16 AM

While in its current development, the Ion engine doesn't look that exceptional on paper but most of the engines developed so far aren't much more powerful than a large sports motorcycle in terms of their output. Around 75kw, which is not very much at all.

What would make a difference is ramping that power output up by a factor of x1000 in a technology level much higher than ours and then you've got a serious bit of propulsion with a big reactor behind it to deliver the power.


As far as fuel goes, the simplest way of producing a rare gas like xenon could be done as part of the fission process of the reactor, like stripping a variety of Xenon isotopes out of Iodine, that would also have a relatively short half life in minutes, seconds or miliseconds depending on how you want them to be used. A few like Xenon-135 is also a fairly important isotope in a reactor anyway to retard it from going boom.

That I guess could be tuned to produce a surplus amount of isotopes for fueling the engines with some higher technology levels.


Atmospheric, I'd imagine a lot of what a vehicle does there would be down to its repulsors to help it move around inside a gravity well. Plus depending on the 'ion engine' a few are capable of essentially being more of a 'plasma' engine as well, so heat is a good form of propulsion there for them.


Just a few thoughts on the idea.

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#3 kinnison



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Posted 01 March 2014 - 08:44 AM

I always thought most engines in the Star wars universe were reactionless.  But it seems the Hoersch-Kessel Ion Drive, they covert "Fuel" in a fusion reaction to create the necessary Charged particles to propel the ship.  the Fuel could be anything even Uranium.


I guess if you smash things together, you create something with a high enough Specific impulse that it really doesn't matter if you are in Atmosphere or not

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#4 2P51



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Posted 01 March 2014 - 08:53 AM

You're right about space fantasy and all because if their tech can overcome the tech hurdles in creating a planetary sized vessel that can move through hyperspace, ion fuel would not be a big deal.


Honestly fuel really would not and won't be a big deal once you're really out in space.  There are a host of useful goodies typically readily available in a gas giant's atmosphere and the moons have things like lakes of hydrocarbons.  Given the fact in the Star Wars universe power doesn't seem to be an issue really just about anything could be used for fuel.

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#5 UHF



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Posted 01 March 2014 - 09:43 AM

Reducing this back to story... You could toss black dice at piloting rolls for conditions as you describe....

However, as MKK pointed out ion drives would need to be like 1000X stronger to be of any use. So it would drown out any weak ionization in the area. If you were to use such a drive in an ion rich environment, I can't think of a reason why it wouldn't work. Heck... Reverse the polarity if necessary.

By the way, I think what you are thinking through is valuable. It helps to BS your players when you describe what is happening. I've been struggling with how to describe stasis fields. I'm thinking they appear to radiate cold, and are pitch black regions (because light shouldn't be able to move). If you touch them... Well, you stick... (I plan to use that property to trash the players' space ship.). You cannot move into or out of one.
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#6 Brother Orpheo

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Posted 01 March 2014 - 02:23 PM

1- By the way, I think what you are thinking through is valuable. It helps to BS your players when you describe what is happening.


2- I've been struggling with how to describe stasis fields. I'm thinking they appear to radiate cold, and are pitch black regions (because light shouldn't be able to move). If you touch them... Well, you stick... (I plan to use that property to trash the players' space ship.). You cannot move into or out of one.

1- I find ten to fifteen minutes of Google-fu puts a little more "oomph" into a session. Using the jungle world as an example, I'd simply describe how the PCs' ship maneuvers become "cumbersome" or "respond sluggishly" within the atmosphere, not require any dice rolling, rather just "...and when you cross the threshold from the mesosphere to the stratosphere you have to haul pretty hard on the controls to get them responding..." It's importance would come later, if and when they engage in ship combat, throwing in two black dice at lower altitudes and reducing that number if they break for the mesosphere.


It could make for an interesting "race" scenario challenge, where local inhabitants are largely unaffected by the phenomenon, but a newcomer finds it to be a handicap.


I'll probably do a wee bit more research into fission reactors, plasma reactions, etc. An interesting thing about plasma is its containment- modern-day plasma cutters utilize disposable "jet" tips, which need periodic replacement due to flash debris resulting from the surface being pierced. One could say that part of the maintenance cost of owning a ship is engine ignition parts- ignition tips become fouled... "I stopped and picked up a new set of points, so we shouldn't have any more problems for a while." Sans despair results, that is.


2- Regarding stasis fields: Once, quite a while back, I thought to myself "Is the field a barrier, or is it an area of effect?" Let's say you want to preserve a body; a barrier traps some extremely limited atmosphere, the body asphyxiates, there is some decomposition, and preservation fails. An area of effect, on the other hand, preserves everything within it. Not that I'm a qualified stasis engineer...


However, the distinction could be used as very subtle terminology in-game- stasis "barrier" is used to denote just that, a barrier. Prison ship cells, the barrier that divided Obi-Wan from Qui-Gon and Darth Maul, etc. A stasis "field" denotes an area of effect, and everything within that AoE is subjected to stasis effects.


EDIT- An interesting thought just occurred to me: If a stasis barrier/field prevents light motion through it, then you wouldn't be able to see through it. And I'm not saying that's a bad thing.

Edited by Brother Orpheo, 01 March 2014 - 02:36 PM.


#7 UHF



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Posted 02 March 2014 - 11:59 AM

Regarding Ion Engines...  Locals would most definitely have their vehicles adjusted to local conditions.  It probably takes a few hours and an average Mechanics check... "Duh!  Reverse the polarity, change the fuel, and run it for 10 minutes till its clean."  On a bad day it needs parts and a fuel change.


Another observation about that, is that your players could probably look it up on the GGG and figure out what the locals do.


I live in a high altitude environment. My projector runs for a while, flutters, and gives an overheating warning.... unless i set 'High Altitude: On' in the menus.  (True story!)



Regarding Stasis...  Its not defined as a barrier but nothing can get in or out.  So it would most definitely would work that way.  Its a perfect immovable object for space ships to clip. I plan to have the players' ship get hit by a spike from a failing stasis field.  This should have the effect of a massive massive collision, and trash the ship.  (Imagine if your car suddenly had a telephone pole appear in the middle of it.)

#8 korjik



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Posted 02 March 2014 - 01:46 PM

When you get into atmo, you are using repusorlifts, not the main ion drive, for thrust.


Plus, if you want to put realism into Star Wars tech, then it wont be SW tech. Modern ion drives do not work like drives do in SW. Even really powerful ion drives give very small thrusts. An ion drive's strength is fuel efficiency. Even the 100 kW VASIMR I was working on only did a few 10s of Newtons of thrust. Even upping the power to terawatts would still give you small accelerations.


The biggest reason that ion drives dont work in atmo is more that the drive has a vacuum inside. In atmo, the atmo would backwash into the engine and thermalize the ions before they got out of the thrust nozzle. In English, the atmo would deflect the ions from going out the back of the rocket before they got out of the rocket. Also, depending on if it is a true ion drive or a plasma rocket, the ion drive would lead to some really spectacular lightning strikes into the thrust plume, then up into the enging.

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#9 cvtheoman



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Posted 03 March 2014 - 01:57 PM

Plus, if you want to put realism into Star Wars tech, then it wont be SW tech.  


To some extent that's true, but you don't need to rain on their parade.


It shouldn't really hang up the game (because who would rather argue when you can play Star Wars?), but if you want to make something a plot point, and you can use real-world tech knowledge to make it sound more reasonable (and thereby maintain suspension of disbelief more easily), then by all means use it.


The math, the tech, the lore: everything in this game should serve the players/GM in having fun, because that's the whole point.

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#10 Orjo Creld

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Posted 05 March 2014 - 09:44 AM

Mr. Shatner, how does it feel to be transported?

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