egg changed the topic of #principia to: Logs: https://esper.irclog.whitequark.org/principia | <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/ | <egg> calculating the influence of lamont on Pluto is a bit silly…
<queqiao--> <E​mi​l.​za​07​> how did that happened? my pe was about 210 and about 2 seconds before end of burn it became negative https://media.discordapp.net/attachments/480397772248580098/1412801906824450239/image.png?ex=68b99dcf&is=68b84c4f&hm=617acf54fe33fc083ec0c1fd6123267d81bc3a06a46bfdea9314f1315b450e86&
<queqiao--> <e​gg​> Well, you are playing with Principia, so you are not alone with the Earth in this solar system. you have an eccentric orbit, and the Moon is going to alter your orbit (there is a mechanism by which eccentricity gets exchanged for inclination, the Лидов-古在 mechanism).
<queqiao--> <e​gg​> See the graphs in https://github.com/mockingbirdnest/Principia/pull/3113 (that is a Mercury orbiter being perturbed by the Sun, but same principle.)
<queqiao--> <E​mi​l.​za​07​> but my inclination almost not changing...
<queqiao--> <e​gg​> Can you open the Principia orbit analyser?
<queqiao--> <E​mi​l.​za​07​> (another launch but I'm colliding with earth after few orbits
<queqiao--> <e​gg​> Try analysing for more than 4 days, so we can see what happens in the long run?
<queqiao--> <V​ec​to​r ​(A​no​th​er​ L​R-​87​ f​an​)> you're probably on a non stable orbit
<queqiao--> <E​mi​l.​za​07​> what do I see here?
<queqiao--> <e​gg​> Here is the documentation of the analyser https://github.com/mockingbirdnest/Principia/wiki/Orbit-analysis
<queqiao--> <e​gg​> That doesn’t seem incompatible with Лидов-古在. (Maybe the analyser should show some information that would allow us to tell that the Лидов-古在 mechanism is dominant.)
<queqiao--> <k​uz​in​at​0r​> The main takeaway there is high elliptical orbits are not stable. Orbital analyzer can tell you for how long your satellite is going to stay in orbit. If you see your lowest point getting lower and lower when you increase the time period, it means it's not gonna stay here for long.
<queqiao--> Reply to "e​gg​: That doesn’t seem incompatible with Лидов-古在. (Maybe the analyser should show some inform..."
<queqiao--> <E​mi​l.​za​07​> didn't understand anything🥲
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> Orbits like that don’t like existing because of something apparently named after someone Russian and someone Chinese
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> The moon and sun screw them up very quickly
<queqiao--> Reply to "k​uz​in​at​0r​: The main takeaway there is high elliptical orbits are not stable. Orbital analyzer can te..."
<queqiao--> <E​mi​l.​za​07​> and how can I calculate a more stable elliptical orbit? just trial and error?
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> Flight plan and the orbit analyzer
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> If you do it right, you can find an orbit that’s pretty stable. 63.4 inclination is a good start, and apogee far away from the moon
<queqiao--> <e​gg​> The practical advice here is « plan with some margins, eccentric orbits will get more eccentric »
<queqiao--> Reply to "E​mi​l.​za​07​: and how can I calculate a more stable elliptical orbit? just trial and error?"
<queqiao--> <k​uz​in​at​0r​> Higher periapsis would definitely help
<queqiao--> <e​gg​> Why this specific orbit is doing what it is doing is not completely clear (the two possibilities are that the Earth is not a spherical cow and that the moon exists, the latter leads to the Лидов-古在 mechanism, but the former can have a periodic influence on eccentricity too).
<queqiao--> <e​gg​> But that doesn’t really matter to you, especially as a beginner.
<queqiao--> <e​gg​> Just plan with margins, learn what works and what doesn’t.
<queqiao--> Reply to "k​uz​in​at​0r​: Higher periapsis would definitely help"
<queqiao--> <E​mi​l.​za​07​> okay, but I want to do it smart, not :caveman: :) https://cdn.discordapp.com/emojis/836199374694514708.png
<queqiao--> <e​gg​> I think the inclination of 63.4° mentioned above isn’t relevant here. That is to deal with eliminating the precession of the argument of the periapsis arising from oblateness, but it has nothing to do with eccentricity.
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> precession of AOP does bring the apoapsis closer to the moon though?
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> Which is the real problem
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> at least in my limited experience
<queqiao--> <e​gg​> That orbit is basically equatorial, so the moon will bring itself closer no matter where the periapsis is.
<queqiao--> Reply to "E​mi​l.​za​07​: okay, but I want to do it smart, not :caveman: :)"
<queqiao--> <e​gg​> Well, you can learn a lot of fancy equations for perturbations (see the Лидов paper on Лидов-古在, or the Capderou book on the perturbations from oblateness), but while that is funs can help design some very specific orbits, it’s not quite the same thing as experience of what works and what doesn’t. In practice, my gut feeling is that an eccentric orbit with a period of one day is asking for trouble, and so is an
<queqiao--> equatorial eccentric orbit.
<queqiao--> Reply to "G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​): Flight plan and the orbit analyzer"
<queqiao--> <E​mi​l.​za​07​> does flight plan work for launching into orbit? it looks like it's better for some in-orbit maneuvers, no?
<queqiao--> <E​mi​l.​za​07​> btw, will a polar orbit be more stable? and why?
<queqiao--> <e​gg​> I’m not sure.
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<queqiao--> Reply to "E​mi​l.​za​07​: "
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> You need a higher pe, most perturbation are cyclic so if you survive once to your pe dropping you probabily will survive for the near future too
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> *most Earth orbit perturbations. Lunar orbits tend to diverge instead of moving cyclically, at least low ones
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<queqiao--> <C​la​ye​l> i wonder how hard it would be to display the current sum of forces in the map view in principia
<raptop> things principia can't do: https://arxiv.org/abs/2509.01672
<raptop> Ways to get up to very low Δv grand tour shenanigans? https://arxiv.org/abs/2509.00518
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