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->
⟨Jason Kerman⟩ Hi! I'm trying to test my planet mod under principia. The orbit stability is fine, but the only issue is for tidally locked planets. After a longer time they no longer have the right side facing their parent body. Is there a way to solve this issue?
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<queqiao->
⟨clayel⟩ id imagine the problem is due to orbital perturbations, as i wouldnt imagine that principia doesnt simulate tidal mechanics
<queqiao->
so overtime, the rotation of the planet will stay the same but the orbital period will slightly change, so itll be in the wrong spot
<queqiao->
⟨thunkii⟩ ⟪clayel⟫ lifting re-entry usually only prolongs […] ⮪ spiro agnews speech for when apollo 11 lands on top of uss hornet, crushing nixon
<queqiao->
⟨clayel⟩ lmao
<queqiao->
⟨Jason Kerman⟩ May I suggest a feature to keep tidally locked bodies facing the correct direction? Since any tiny perturbations in the orbit period can accumulate over time.
<queqiao->
⟨Al₂Me₆⟩ > The way to do it is to run you system for a long time (tens to hundreds of revolutions of the planet) and set the rotation period to match the (average) revolution period.
<queqiao->
Celestial analyser when 🥺
<queqiao->
⟨sichelgaita⟩ ⟪Al₂Me₆⟫ > The way to do it is to run you system […] ⮪ We have it already, to detect that your orbit is heliosynchronous. But we don't show it. Just play Principia the way it's intended to be played, in C++.
<raptop>
Instructions unclear; installed a FORTRAN development environment
<queqiao->
⟨aebestach⟩ Hi all, I'm using Principia in the stock game and want to plot a sun-synchronous orbit on kerbin.
<queqiao->
I set this parameter in the game. In addition, through the calculation of the above formula, I set my eccentricity, inclination and semi-major axis.But the trajectory results provided by Principia is not sun-synchronous orbit and his NodalPrecession is 0, not (360/426d ≈ 0.85°/d)
<queqiao->
I would like to ask, do I need to use other parameters when I set it up?
<queqiao->
⟨aebestach⟩ And I fill in according to the data in the chart and enter the orbit.
<queqiao->
⟨sichelgaita⟩ You should check the INFO log corresponding to the creation of the new save. It will contain a list of all the parameters used by Principia. If this doesn't mention "j2" then your game is somehow misconfigured.
<queqiao->
⟨aebestach⟩ Thank you for your advice. I'll check it right away.
<queqiao->
⟨nazfib⟩ ⟪aebestach⟫ And I fill in according to the data in […] ⮪ I'd take a closer look at the units. Especially the value of ω looks wrong: you calculated it in radians per second, while all the other values are using degrees. I also wonder if somewhere in the derivation of the formula, the assumption that units are in radians was used (but not explicitly mentioned).
<queqiao->
In any case, I whipped up a quick plot of the inclination for various altitudes [(semi-major axis) - (Kerbin's radius) for eccentric orbits] and eccentricities, with the given J2 value of 0.002. This is, of course, untested in-game - but I checked the code against Earth values, where it produces correct results.
<queqiao->
⟨sichelgaita⟩ ⟪aebestach⟫ ```make_optional_c_string(body_parameter[…] ⮪ So your configuration looks fine, the problem is elsewhere. "j2" is all you need, that's what we use for the Sun. Don't go messing with the geopotential.
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<queqiao->
⟨Jason Kerman⟩ Could anyone tell me how much the error will be if I use the highest timewarp speed with BetterTimeWarp?
<queqiao->
⟨Jason Kerman⟩ * maximum
<queqiao->
⟨egg⟩ ⟪Jason Kerman⟫ Could anyone tell me how much the error […] ⮪ What do you mean? If you mean the motion of planets or vessels with engines off, the precision does not depend on timewarp with Principia.
<queqiao->
⟨Jason Kerman⟩ ah that's what I mean. thanks!