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Atmo/Ion thruster efficiency, new formula wanted

Discussion in 'Survival' started by domingo, Sep 19, 2018.

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This last post in this thread was made more than 31 days old.
  1. domingo Trainee Engineer

    Messages:
    46
    I've trying to find out the Atmospheric (and Ion) Thruster efficiency in Atmosphere.
    I've found some info here: https://spaceengineerswiki.com/Planet#Atmosphere (same on Moon page)

    However it provides outdated information.
    There is no longer 'Hills' or 'LimitAltitude' parameter in .sbs files, nor anything resembling atmospheric density (if it is still a factor).

    Does someone know a current formula ?
     
  2. mojomann71 Senior Engineer

    Messages:
    1,840
    I could be wrong but I think if there is any hint of an atmosphere ion efficiency is 0.
    As the atmosphere gets thinner the atmospheric thrusters weaken.
    Again I am not 100% certain but I think a good "guesstimate" would be for every 10 meters from the surface of the planet your atmospherics would be 0.6% less effective.
    Again this is just a good guesstimate from my time playing on surfaces.

    I am sure planet radius still plays a factor in the formula. I usually play with 120K radius. So my results could vary.

    I am not aware of a published official formula that Keen currently uses.
     
  3. NoThanks Apprentice Engineer

    Messages:
    458
    Just a bit of semi helpful info, Ions are always working, even in full atmosphere, their efficiency is greatly reduced the closer you get to a planet surface. Atmospherics start working around 6 or 7 km up if I recall. (Set override and wait for it to start reading a number while you plummet). I do not not the formula though so that's the end of my semi useful information.
     
  4. domingo Trainee Engineer

    Messages:
    46
    It is not in Scenario*.sbs, but in PlanetGeneratorDefinitions.sbc -> so these variables are still in use.
    I am using formulas from git, thought it might be outdated ... however it is enough for my purposes.



    First you have to compute atmospheric influence (terms might differ from variables in actual code, I have them in excel table formula):
    Code:
    AtmosphericInfluence = Atmosphere.Density * CLAMP( Altitude_SeaLevel / (Planet.Radius * HillParams.Max * Atmosphere.Limit), 0, 1 )
    Then formula for (vanilla) Ion thrusters is:
    Code:
    1 - 0.7 * CLAMP( AtmosphericInfluence, 0, 1)
    For (vanilla) Atmospheric:
    Code:
    CLAMP( ( AtmosphericInfluence - 0.3) / 0.7, 0, 1 )
    In fact in code it is a little bit more general, because the efficiency is computed from thruster definition values NeedsAtmosphereForInfluence, MinPlanetaryInfluence, MaxPlanetaryInfluence, EffectivenessAtMaxInfluence and EffectivenessAtMinInfluence.
     
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