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->
⟨pisslover72⟩ this is what's going on with mine
<queqiao->
⟨pisslover72⟩ thats why im wondering if my code's just messed up still
<queqiao->
⟨pisslover72⟩ * still, or if this is due to low max degree
<queqiao->
⟨pisslover72⟩ ++ floating point precision errors
<queqiao->
⟨pisslover72⟩ * underflow
<queqiao->
⟨pisslover72⟩ +(im using single precision vectors)
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<queqiao->
⟨sichelgaita⟩ Well, the geopotential introduces a torque, right? For simplicity, let's consider a circular orbit. If there is a big block of rock on one side of the planet (I'm looking at you, Olympus Mons) the force is not radial, so 𝒓⨯𝑭 is not null and that's exactly d𝑳/d𝘵. Thus, 𝑳 is not constant. The opposite torque appears when the mountain has moved to the other side of the planet, so 𝑳 oscillates at the period...
<queqiao->
... of the orbit.
<queqiao->
⟨sichelgaita⟩ Your graph also shows a drift, and that could be due the effect of distant celestials introducing their own torque. (It could also be that the integrator or numerics are faulty, we don't know what you are doing exactly.)
<queqiao->
⟨sichelgaita⟩ Finally, note that the degree of the approximation plays no role unless you are trying to reproduce a real trajectory: it is possible to construct a celestial with a mass distribution such that the spherical harmonics beyond, say, degree 10, are all exactly 0. For such a celestial, the degree-10 approximation would be exact.
<queqiao->
⟨kaborl⟩ In RSS stock, my parking orbit always was to circularize at 150km because it was more than enough.
<queqiao->
⟨kaborl⟩ However, that's not the case in Principia. I found that 150 results in Pe to change slowly below 140.
<queqiao->
⟨kaborl⟩ What altitude do you usually go to when playing Principia?
<queqiao->
⟨lpg4999⟩ I like 170. But there's a decent chance you're misunderstanding what you're looking at and the "real" Pe isn't actually going below 140
<queqiao->
⟨lpg4999⟩ e.g. the stock Pe indicator will fluctuate, but that's not telling the truth
<queqiao->
⟨kaborl⟩ It's possible I'm misunderstanding what I'm reading since I'm hours into Principia. However, in my first orbit my vessel successfully circularized at 150 km (150x147 km or something like that with PVG) and in 1 or 2 orbit or so the Pe went below 140 by a bit. Eventually the vessel went into the atmosphere (warp changed, etc) and did come out as well (waro and music restored).
<queqiao->
⟨kaborl⟩ My point is that it did go below 140km, which proved to be an unstable LEO orbit.
<queqiao->
⟨lpg4999⟩ yeah that's "real". and yes it happens
<queqiao->
⟨GoForPDI (less drag=more faster)⟩ Earth's oblateness does that to low orbits yes
<queqiao->
⟨lpg4999⟩ a "parking orbit" that goes for more than 1 orbit should be rate enough that the issue doesn't come up much, however
<queqiao->
⟨kaborl⟩ What do you mean by "it should be rate enough"?
<queqiao->
⟨lpg4999⟩ typo. "rare" (I just re-typoed it the same way, stupid fingers)
<queqiao->
⟨kaborl⟩ Do you think 170 km is high enough for a 99.9% stable LEO ? Also, do I have to worry about the 0.01% what about 0.10% or higher chances of being unstable? Thanks.
<queqiao->
⟨kaborl⟩ * 99.99%
<queqiao->
⟨kaborl⟩ +1%
<queqiao->
⟨qazerowl⟩ principia has an analyze orbit button that you can use to have it tell you the lowest you will get in a specified timeframe
<queqiao->
⟨mmeridian⟩ i use 185km circular 99% of the time
<queqiao->
⟨mmeridian⟩ i've done 165km for really low performance lvs