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-> ⟨.popvapor⟩ Does principia block you from switching between vessels in the map view?
<queqiao-> ⟨captainswag101⟩ I can't even target vessels or celestial bodies by clicking them any more. My guess is it's changing how that works or something.
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ yeah you have to use the menu to pick target
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ install it again I think
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ like anything else you install manually
<queqiao-> ⟨ezsnack⟩ i mean fine to overwrite or deleting first is a must?
<queqiao-> ⟨captainswag101⟩ Well, I just tried to update by overwriting, so we'll see how that goes!
<queqiao-> ⟨captainswag101⟩ I also have a big question: how do I know how close my approach is to a target planet, for interplanetary transfers? I've followed the instructions in the pinned message of this channel, but I've yet to successfully figure out how I'm actually supposed to tune my ejection burn to get particularly close to my target planet. There doesn't seem to be any way to get a reference frame where the target planet is stationary:...
<queqiao-> ... something similar to the MEO reference frame. Is there some special way to access such a reference frame, because I can't find one.
<queqiao-> ⟨nazfib⟩ That would be the Planet-Sun-Orbit reference frame
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ that doesn't fix the Earth and the planet, but the sun and the planet. Which I guess is good enough
<queqiao-> ⟨captainswag101⟩ Is there any way to make it show my periapsis for the target body rather than the sun? I have no clue how close I'm getting aside from seeing that the two trajectory lines are visually somewhat close.
<queqiao-> ⟨.popvapor⟩ But I can't switch vessels from map view?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ it should show you the periapsis to the target, the way it shows you your perilune in MEO? But I haven't actually done interplanetary flights with Principia
<queqiao-> ⟨captainswag101⟩ It does not, even if I use the "select target celestial" button in the Principia window. It only shows me my perihelion
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Huh
<queqiao-> ⟨nazfib⟩ The Planet-Sun-Orbit reference frame shows you your apsides relative to the planet; however, if your planned trajectory is too short, you may not have a periapsis within the trajectory.
<queqiao-> ⟨nazfib⟩ +target
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ actually yeah try increasing your plan length
<queqiao-> ⟨captainswag101⟩ Sure thing, let me re-sim the thing again. It'll take a few minutes to get the sim to load at the transfer window.
<queqiao-> ⟨captainswag101⟩ Actually speaking of that, is there a way to calculate an optimal launch inclination for an interplanetary transfer? Or should I just put my default inclination into TWP and not worry about it?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ that's what I do, yeah
<queqiao-> ⟨nazfib⟩ TWP always gives you the lowest possible inclination (which is the inclination you've given it, if possible)
<queqiao-> ⟨nazfib⟩ * inclination that will work
<queqiao-> ⟨captainswag101⟩ The pinned message suggested using the TWP transfer time plus a few weeks, last time I tried this I added about 20 days. Should I add more?
<queqiao-> ⟨nazfib⟩ Probably? If no periapsis shows up, the trajectory is too short.
<queqiao-> ⟨captainswag101⟩ By this, do you mean the GSE frame? There is no PSO or ESO frame.
<queqiao-> ⟨nazfib⟩ Earth-Sun-Orbit (this one is called GSE) when planning to go to Earth, Venus-Sun-Orbit when going to Venus, Mars-Sun-Orbit when going to Mars, etc.
<queqiao-> ⟨captainswag101⟩ I do not have such an option available to me...
<queqiao-> ⟨nazfib⟩ Click the "+" in front of "Sun"
<queqiao-> ⟨captainswag101⟩ Aha! Thank you so much, I didn't think to try that
<queqiao-> ⟨captainswag101⟩ One more question, how do I know what the minimum safe orbital distance is for a planet? I'm not sure how low I can safely insert a satellite into orbit around, for instance, Venus.
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Venus's atmosphere iirc ends at 145km. Principia may perturb your orbit so put your periapsis quite a bit above that
<queqiao-> ⟨captainswag101⟩ Okay, I'm going to target around 360 km, thank you!
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ assuming you're just doing a flyby, yeah that should be ok
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ you can actually dip a few kilometers into the atmosphere during a flyby and get a few science points that way, if you like living dangerously
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ but for an orbiter yeah you'd probably want around 300km
<queqiao-> ⟨captainswag101⟩ I'm aiming for an orbit, but probably an elliptical one so I can gather high and low science. Trying to get both flyby and orbit contracts in one go.
<queqiao-> ⟨captainswag101⟩ +space
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ nice
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ the boundary iirc is 5 Mm?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ you could do the dip-in thing and then capture, and then do an apoapsis kick into your final orbit
<queqiao-> ⟨captainswag101⟩ Wouldn't I need some dedicated thermal protection for that?
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ for only five kilometers in, no
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ like on Earth, you need to dive in 40km or so to start burning up
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ you can get a solid minute or two of high-atmosphere science with no consequence except a small RCS boost at apoapsis
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ the middle 'border' column there is the top of the atmosphere
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<queqiao-> ⟨.popvapor⟩ I think not being able to switch between vessels in the map view breaks some missions, unless I'm missing something
<queqiao-> ⟨captainswag101⟩ You can use the Kerbalism menu to switch between vessels if you need to. That's the only way I know how to do it since Principia prevents the usual method
<queqiao-> ⟨egg⟩ Be careful with eccentric orbits: they tend to be affected by the Лидов–古在 mechanism (periodic inclination-eccentricity exchange resulting from perturbations by the sun).
<queqiao-> ⟨egg⟩ 👆
<queqiao-> ⟨Damien⟩ egg am I right in thinking you're based in Zurich?
<queqiao-> ⟨.popvapor⟩ How do I do this?
<queqiao-> ⟨.popvapor⟩ I can't find this menu anywhere
<queqiao-> ⟨.popvapor⟩ I've gone through every button on my toolbar, none are kerbalism
<queqiao-> ⟨ezsnack⟩ well that sends the wrong link lol
<queqiao-> ⟨.popvapor⟩ I've gone through this wiki and I cannot find any place that details how to switch between vessels while flying
<queqiao-> ⟨.popvapor⟩ I even tried searching through this https://kerbalism.readthedocs.io/en/latest/gui.html
<queqiao-> ⟨ezsnack⟩ you asked how to open kerbalism tho?
<queqiao-> ⟨.popvapor⟩ I asked how to use the kerbalism menu to switch between vessels
<queqiao-> ⟨.popvapor⟩ I cannot find any part of the kerbalism menu that allows you to do this
<queqiao-> ⟨.popvapor⟩ The only menu i see related to kerbalism are:
<queqiao-> ⟨ezsnack⟩ in the craft list just click on its icon
<queqiao-> ⟨.popvapor⟩ FINALLY!, the mission was completed after switching to each of the vessels using kerbalism
<queqiao-> ⟨Damien⟩ sichelgaita in in Zurich at the moment. 3rd time here
<queqiao-> ⟨Damien⟩ * I'm
<queqiao-> ⟨egg⟩ But we are not there at the moment.
<queqiao-> ⟨egg⟩ you can also target a vessel and then switch to it via the Principia UI.
<queqiao-> ⟨Damien⟩ Damn. A wasted trip then
<queqiao-> ⟨Damien⟩ My kidnap plans ruined
<queqiao-> ⟨Damien⟩ Did find a nice flavour of redbull though
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<_whitenotifier-bad2> [OSACA] pleroy opened pull request #12: Preparatory changes for semantics suppor - https://github.com/mockingbirdnest/OSACA/pull/12
<queqiao-> ⟨.popvapor⟩ Does principia's flight path take air restistance into account?
<queqiao-> ⟨.popvapor⟩ * resistance
<queqiao-> ⟨siimav⟩ No
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<queqiao-> ⟨.popvapor⟩ Is principia using random numbers for it's calculations at all?
<queqiao-> ⟨.popvapor⟩ I just did the moonimpact mission but had to load save because I forgot to do something else, and I crashed in a different spot the same time around even though I had imparted no force on the craft after loading the save
<queqiao-> ⟨.popvapor⟩ * second
<raptop> It *should* be deterministic, is this replicable?
<queqiao-> ⟨.popvapor⟩ I'll try it again and try to take a video
<queqiao-> ⟨.popvapor⟩ Is there a good guide somewhere on how to get free return trajectories with principia? I can get encounters no problem, but all my moon encounters just fling my craft out into space unless i burn to circularize
<queqiao-> ⟨.popvapor⟩ Would i need to come in retrograde for the moon's gravity to slow me down?
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<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ Yeah, come in on the front side
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<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ I’ve gotten several FRTs accidentally while throwing darts at the moon, it isn’t too difficult. The real hard part is getting one with a reasonable perilune for orbit insertion
<raptop> While the exact positions are different, it should still be very roughly similar to getting FRTs with patched conics
<queqiao-> ⟨egg⟩ That guide is from 2016 so some things have changed, but the gist of it should still be sound.
<queqiao-> ⟨.popvapor⟩ This guide leaves out actually getting to that orbit
<queqiao-> ⟨Joshua Wood⟩ FRT with patched conics is generally much much easier, since you just launch into the plane of the moon and you can just fiddle with the node till it works, with principia you have to launch etc.
<queqiao-> ⟨egg⟩ (Looks like that is from NASA TN D-1833 https://ntrs.nasa.gov/api/citations/19630007117/downloads/19630007117.pdf, for anyone wondering.)
<queqiao-> ⟨.popvapor⟩ I'm using lunar transfer window planner to give me my launch inclination maybe i'm using it wrong
<queqiao-> ⟨Joshua Wood⟩ I used LTP with a 3day transfer time and it gave me good free returns <100km from the surface
<queqiao-> ⟨Joshua Wood⟩ +(letting it autowarp me till i launched at current inclination)
<queqiao-> ⟨.popvapor⟩ So i launch here to a parking orbit of ~200km
<queqiao-> ⟨.popvapor⟩ So i launch here to a parking orbit of ~200km inclination of ~36*
<queqiao-> ⟨Joshua Wood⟩ yup!
<queqiao-> ⟨.popvapor⟩ So i launch here to a parking orbit of ~200km inclination of ~37*
<queqiao-> ⟨.popvapor⟩ Okay but when I do that, I can't get a free return trajectory. Everything just flings me out into a bigger orbit once I'm away from the moon
<queqiao-> ⟨egg⟩ +Schwaniger, A. J. Trajectories in the Earth-Moon Space with Symmetrical Free Return Properties. In: _Lunar Flight Study Series_. Volume 5. 1963.
<queqiao-> ⟨Joshua Wood⟩ then you fiddle with the nodes swapping back and forth between MEO reference and earth centric till you are both close to the moon and return close to the earth, having some generics or something for mid-course corrections makes it a LOT easier :p
<queqiao-> ⟨Joshua Wood⟩ your inclination around the moon matters a LOT so does several other things, you wand to eject "backwards" in the moons orbit
<queqiao-> ⟨Joshua Wood⟩ * want
<queqiao-> ⟨.popvapor⟩ Yeah but is a free return only possible if I'm at the same inclination as the moon?
<queqiao-> ⟨Joshua Wood⟩ no, i was launching brom baikonour (can't spell)
<queqiao-> ⟨Joshua Wood⟩ * from
<queqiao-> ⟨Joshua Wood⟩ Apollo did it :p
<queqiao-> ⟨.popvapor⟩ Yeah but I'm just not getting the trajectory, no matter what angle I come towards the moon it's just giving me extra deltav instead of taking some away
<queqiao-> ⟨Joshua Wood⟩ you are going for a 3 day transfer time i assume? your lunar peri should be just over 3 days from your burn
<queqiao-> ⟨Joshua Wood⟩ You then need to get your inclination right
<queqiao-> you'll have to work it out, it is very much possible
<queqiao-> ⟨.popvapor⟩ Here i am matched up exactly with the timing of the LTP and it's nowhere close:
<queqiao-> ⟨Joshua Wood⟩ your moon peri is completely wrong, LTP only gives you when you launch from the ground not the TLI burn
<queqiao-> ⟨.popvapor⟩ I don't know what this sentance means
<queqiao-> ⟨Joshua Wood⟩ the TLI burn timing you need to figure out on your own
<queqiao-> ⟨Joshua Wood⟩ lunar transfer planner ONLY gives you what time you click spacebar for mechjeb to launch, literally everything else you figure out
<queqiao-> ⟨Joshua Wood⟩ this should be <2h here, use the little bar to figure out what time gets you closest to the moon
<queqiao-> ⟨.popvapor⟩ My issue isn't getting a moon encounter -- i can get one no problem i've already done 3 impacts
<queqiao-> ⟨.popvapor⟩ I just can't figure out what i need to do to get a free return
<queqiao-> ⟨Joshua Wood⟩ i'm literally telling you?
<queqiao-> ⟨Joshua Wood⟩ it's the same as impactor but with 3 days travel time and the correct inclination
<queqiao-> ⟨Joshua Wood⟩ i can't do it for you...
<queqiao-> ⟨.popvapor⟩ How do I figure out the correct inclination?
<queqiao-> ⟨Joshua Wood⟩ look at it :p
<queqiao-> ⟨.popvapor⟩ ...
<queqiao-> ⟨.popvapor⟩ Evidently not, because the impactor was easy I got in 3 seconds
<queqiao-> ⟨Joshua Wood⟩ correct inclination around the moon* it should be in line with the moons orbit
<queqiao-> ⟨Joshua Wood⟩ i said it's the same not that it's easy xd
<queqiao-> ⟨.popvapor⟩ Wait LTP gives you the time to LAUNCH?
<queqiao-> ⟨.popvapor⟩ Like, from the ground
<queqiao-> ⟨.popvapor⟩ * ground?
<queqiao-> ⟨Joshua Wood⟩ yes
<queqiao-> ⟨Joshua Wood⟩ that is IT, NOTHING else
<queqiao-> ⟨.popvapor⟩ I've been using it to give me the time to start my lunar insertion burn from a parking orbit -_-
<queqiao-> ⟨Joshua Wood⟩ no, that is different and you need to work that out yourself, which is super simples
<queqiao-> ⟨.popvapor⟩ That's why I was confused by youre box around tinital -- i matched it up exactly to LTP "first window"
<queqiao-> ⟨Joshua Wood⟩ +( getting to to get you back to earth is the tricky bit)
<queqiao-> ⟨.popvapor⟩ So what does LTP even do? I've apparantly been getting all of these encounters without even using it
<queqiao-> ⟨Joshua Wood⟩ yes that's why i said it should be <2h because that is around the orbital period of a 200x200 orbit aha
<queqiao-> ⟨Joshua Wood⟩ LTP gives you the time to launch so that the moon will be at the AN/DN of your orbit if you launched right now in the time you set
<queqiao-> ⟨Joshua Wood⟩ so for a free return you want the moon to be at your AN/DN 3 days after you launch right now :p that's all it does
<queqiao-> ⟨.popvapor⟩ And what I just need to launch with a window as close to 0* as possible for less deltav?
<queqiao-> ⟨Joshua Wood⟩ +(i don't want to hear any "um acktulies from anyone i can't think of another way to explain it lol)
<queqiao-> ⟨Joshua Wood⟩ youll want to set your dv to around 3200, then change your time till you fly close the moon
<queqiao-> Adjust your dv and timing of your burn so that your travel time is 3days (ish)
<queqiao-> then spend 20mins fiddling with the numbers till you get a free return xd
<queqiao-> ⟨.popvapor⟩ Ah wait I see, the launch window is when the launch now inclination is at the lowest possible launch inclination
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ yeah, and to make getting an encounter easier
<queqiao-> ⟨Joshua Wood⟩ once in orbit
<queqiao-> youll want to set your dv to around 3200, then change your time till you fly close the moon
<queqiao-> Adjust your dv and timing of your burn so that your travel time is 3days (ish)
<queqiao-> then spend 20mins fiddling with the numbers till you get a free return xd
<queqiao-> ⟨butcher6994⟩ Yes it's time to the next easterly launch
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ higher inclination means you have a shorter window in your orbit where burning would put your apogee in the plane of the moon
<queqiao-> ⟨butcher6994⟩ You can launch at any time but ascents are more expensive if you're not going east
<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ and yes take more delta v
<queqiao-> ⟨butcher6994⟩ From experience it's not much harder from any inclination. Just more expensive for the launch vehicle
<queqiao-> ⟨Joshua Wood⟩ things like 90deg can be fun though because it makes getting a polar orbit at the moon super easy :p
<queqiao-> ⟨butcher6994⟩ I just did polar from easterly launches, just need to tweak your TLI
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