billeinstein
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Everything posted by billeinstein
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Sorry for the mistake of G, I used E-10. It shall be E-11. -
And this is why I point out the SOI in Orbiter is not the same one in KSP.
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This is not the gravity between Sun and Moon, but the Tidal force(axial). And it should be about ~E+19 at the distance of the moon. http://en.wikipedia.org/wiki/Tidal_force#Mathematical_treatment
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Earth-Moon gravity is about 2.0E+21N, and Sun-Moon gravity is about 4.4E+21N.
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Just try and calculate it.
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Additionally, the SOI in Orbiter (where the reference body is changed) is not the same SOI in astrodynamics and in KSP. http://en.wikipedia.org/wiki/Sphere_of_influence_(astrodynamics) Actually, the moon get more gravity from the sun than the earth. But it's still in the earth's SOI. The SOI problems in KSP can be something like an Elliptical orbit with its Apoapsis just outside the SOI (an elliptical escape trajectory). But this is not important in interplanetary transfer.
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When calculating the transfer trajectory, the gravity of source and target planets are ignored. Only the central body(sun) counts. With this transfer trajectory, we can get the difference of V between it and the source or target planet orbit. That's the V(infinity) of the escape or insert trajectory. That's the way KSPTOT and some MFDs(IMFD, TransX) in orbiter work. SOI radius shall be large enough, or it will become a Rendezvous and docking problem. It's some difference between ksp and real world physics in calculating the Multibody gravity. So does this conic path method. That's why we need mcc during the transfer.
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Off-plane trajectories (two impulse Lambert solutions) sometimes may not be good enough. The calculation can get a high inclination eject trajectory which needs more dv. It will be better if it can optimize the transfer trajectories with DSM (Deep Space Maneuvers) sometimes. Such as source plane transfer in the IMFD of Orbiter. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940010378_1994010378.pdf Another example is this web planner (transfer type)： http://alexmoon.github.io/ksp/
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I want to use this tool for RealSolarSystem mod. Then I should build a new bodies.ini file. But I need some help. For Example [Kerbin] epoch = 0 sma = 13599840.256 ecc = 0 inc = 0 raan = 0 arg = 0 mean = 179.908747671079 gm = 3531.6 radius = 600 atmoHgt = 69.077553 bodycolor = winter canBeCentral = 1 canBeArriveDepart = 1 parent = Sun name = Kerbin id = 1 Kerbin { SSTScale = 1 Radius = 6371000 rotationPeriod = 86164.0916 tidallyLocked = false axialTilt = 23.44 atmosphereScaleHeight = 7.5 maxAtmosphereAltitude = 104000 Orbit { semiMajorAxis = 149598261000 eccentricity = 0.01671123 inclination = 0 meanAnomalyAtEpochD = 357.51716 period = 31558149.7635456 LAN = 348.73936 argumentOfPeriapsis = 114.20783 } ...... How to apply this "axialTilt = 23.44" in bodies.ini? Or shall I ignore it？