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…
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<discord-> l​amont. — looks like that'd be interesting to replicate in julia -- although it sounds like the accuracy is highly dependent on the way autodiff is implemented
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<discord-> J​ustMozzie. — does anyone have a good tutorial on how to get to the moon with principia?
<discord-> J​ustMozzie. — im kind of struggling
<discord-> P​aculino (ŝi/ri/she/they). — Are you referring to n-body specific transfers or destinations?
<discord-> B​utcher. — For a normal hohmann transfer its similar to without principia.
<discord-> J​ustMozzie. — how do i get on a similar or same plane as the moon from launch?
<discord-> J​ustMozzie. — basically is what i want to know
<discord-> J​ustMozzie. — i have a rocket that is capable but i just dont know when to launch to get the right plane
<raptop> I recommend launching from Kourou
<raptop> That is, the moon's relative inclination varies, and is usually lower than eg: KSC
<raptop> Baikonur or Plesetsk means dealing with off-plane intercepts
<discord-> J​ustMozzie. — how would i go about launching from kourou in RP-1 without a lot of cost
<discord-> M​arsh. — Just launch to target plane. From the cape it’s a lot harder with principia, because you don’t always have the perfect launch site inclination anymore
<discord-> J​ustMozzie. — got it
<discord-> R​urouniDonut. — What I do, is I sim the launches to see when my AP or PE intercept the moons plane
<discord-> R​urouniDonut. — I just eyeball it at this point
<discord-> l​amont. — don't launch to plane
<discord-> M​arsh. — Basically you launch to LAN. Find what lan works best by simming and then launch to that, flying east
<discord-> J​ustMozzie. — when i launch to lan do i have to set the degree box or is 0 correct?
<discord-> R​urouniDonut. — Or you can launch polar from the cape and try to intercept there
<discord-> M​arsh. — You would type in the degree you wanted
<discord-> l​amont. — does KER give you the LAN of the moon in the tracking station?
<discord-> R​urouniDonut. — You can launch into higher or lower inclinations or change your launch time if needed
<discord-> J​ustMozzie. — does launching to LAN 0 degrees put me into an orbit on the ecliptic
<discord-> J​ustMozzie. — im not quite sure what LAN is
<discord-> J​ustMozzie. — and how do i determine what degree i want to intercept the moon
<raptop> LAN is Longitude of Ascending Node -- where on the reference plane your ascending node is https://upload.wikimedia.org/wikipedia/commons/e/eb/Orbit1.svg
<discord-> l​amont. — you need to find the LAN of the moon and use that
<discord-> J​ustMozzie. — got it that was my next question
<discord-> J​ustMozzie. — how do i find that..?
<discord-> l​amont. — 0 degrees is probably close but with principia wobblineess you should find the actual right value
<discord-> l​amont. — that's why i was suggesting using KER and looking in the tracking station
<discord-> l​amont. — i don't think the standard tracking station data has LAN in stock
<discord-> J​ustMozzie. — oh i should probably download KER
<raptop> well, for the moon, the nodes precess... >_>;;
<discord-> l​amont. — i'm not sure KER does either
<discord-> J​ustMozzie. — one thing though, when i download KER is there any way that i can change when theyre up on screen, because i dont want them to always be there at the top
<discord-> l​amont. — "principia wobbliness" => precession and all that jazz
<discord-> l​amont. — i'm sure there is but IDK
<discord-> J​ustMozzie. — agh :/
<discord-> J​ustMozzie. — ill go through the wiki for it later
<raptop> "Because the orbital plane of the Moon precesses in space, the lunar nodes also precess around the ecliptic, completing one revolution (called a draconic or nodal period) in 18.612958 years (6,798.383 days). (This is not the same length as a saros.) The same cycle measured against an inertial frame of reference, such as International Celestial Reference System (ICRS), a coordinate system relative to the
<raptop> fixed stars, is 18.599525 years."
* raptop assumes that relevant ephemeris are available from JPL Horizons or something
<discord-> M​arsh. — What I do is on launch day hyper edit a craft in orbit and adjust its values (using hack gravity) to get the most optimal transfer, then I right down that LAN and launch close to that. Might have to adjust the lan by a few degrees in the hours waiting for launch, but trial and error gets you pretty close
<discord-> J​ustMozzie. — aight cool
<discord-> J​ustMozzie. — i still have to edit launch profile and do a little more tweaking but ill let yall know what happens!
<discord-> l​eudaimon. — Saying without experience here (I launch from a low inclination site) but can't you just launch into target LAN?
<discord-> M​arsh. — From a low inclination site yes
<discord-> l​eudaimon. — why not from higher inclination? target LAN will not be the correct LAN?
<discord-> M​arsh. — You’ll have to dogleg
<discord-> l​eudaimon. — I'm talking about LAN, not inclination. You can reach any LAN from any inclination
<discord-> l​eudaimon. — I'm talking about LAN, not inclination. You can reach any LAN from any latitude (edited)
<discord-> M​arsh. — Right. I mean, it won’t be a good orbit for transfer. Tangential
<discord-> l​eudaimon. — yeah, so the correct LAN for the transfer is not the target LAN... I wasn't sure about that
<discord-> M​arsh. — This is where the trial and error comes in, there’s always an ideal LAN, since you’re not on the same plane. If the planes match, then it’s simple. If not, launch LAN is required
<discord-> M​arsh. — Doing a lunar impactor is good practice for this, when you’ve got it figured out, it’ll just be prograde from your orbit for an impact
<discord-> l​eudaimon. — haha not sure I'll ever go for a higher inclination launch site before there is some practical tool within MJ to figure out launch LAN from the ground for this kind of stuff
<discord-> M​arsh. — I wish there was. Dealing with LAN scared me away from principia the first time. I heard lpg said he used hyperedit on crafts in orbit to trial and error the ideal lan and that works pretty well. If you hack gravity then mechjebs plotter works correctly. Just edit the orbit to have your launch site inclination and adjust the lan until the delta v is lowest
<discord-> M​arsh. — You’ll need to calculate how much the LAN changes as the moon moves while your wait for your window. A few degrees if you did this same day of launch
<_whitenotifier-edb> [Principia] vSebas starred Principia - https://git.io/J3iQq
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<discord-> e​gg. — I believe @Butcher has a magical script that does the appropriate calculation for you
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<discord-> S​tonesmile. — Yeah, Butcher has a Lambert solver in his kOS scripts I think
<discord-> l​pg. — the limitation of that script is that it's only something you can use at launch time, not rocket-design time
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<discord-> B​utcher. — That's not really an issue for the Moon.
<discord-> B​utcher. — Also I use the lambert solver for interplanetary only.
<discord-> B​utcher. — The Moon script works based on the current time at launch, so there's not really any need to pre-plan.
<discord-> l​pg. — interplanetry seemed to be what the conversation was about. I wouldn't do the hyperedit dance for going to the moon
<discord-> B​utcher. — I preplan with TWP for interplanetary, it's close enough.
<discord-> M​arsu. — TWP seems totally off in my install. When i launch on the day it tells me I have noway to reach the planet I was aiming... Mechjeb gives me another window between 20 and 60 days after and seems more reasonable (I can reach the planet but have huge dV requirements). Have tried for Venus and Mars. But I’m at the very beginning of understanding interplanetary in Principia 🙂
<discord-> l​eudaimon. — MJ advanced transfer porkchops in a simulation at 0°LAN have worked fine for me to plan windows... I don't know how much that is generally reliable though
<discord-> l​pg. — it isn't. there's nothing special about 0°LAN
<discord-> l​eudaimon. — That's funny, because for Venus I consistently managed transfers with virtually no normal/radial components when launching at 0 LAN
<discord-> B​utcher. — Launching at the twp window with my lambert script gives very good results for me.
<discord-> M​arsu. — I’m not smart enough to understand your script 🙂
<_whitenotifier-edb> [Principia] eggrobin synchronize pull request #2973: Documentation for a correctly-rounded cube root - https://git.io/J3BRj
<discord-> l​pg. — anyone familiar with this one?
<discord-> l​pg. — ```
<discord-> l​pg. — F0506 13:47:52.563467 14048 interface_flight_plan.cpp:74] Check failed: vessel.has_flight_plan() 529b28bd-3565-4316-b883-9c791ccec905
<discord-> l​pg. — ```
<discord-> l​pg. — ahah. seems caused by ]-switching vessels while the 'analyze orbit at end of flight plan' window is up (going from a vessel with a flight plan to a vessel without)
<_whitenotifier-edb> [Principia] lpgagnon opened issue #2974: Crash when switching to a vessel without a flight plan - https://git.io/J31YE
<_whitenotifier-edb> [Principia] lpgagnon edited issue #2974: Crash when switching to a vessel without a flight plan - https://git.io/J31YE
<_whitenotifier-edb> [Principia] lpgagnon edited issue #2974: Crash when switching to a vessel without a flight plan - https://git.io/J31YE
<discord-> e​gg. — that is probably an easy fix C#-side. Can you file a bug?
<discord-> e​gg. — oh, you did it already, nice
<discord-> R​urouniDonut. — I use Mechjeb with a dummy craft in orbit for the launch window for interplanetary
<discord-> R​urouniDonut. — And then just sim the hell out of the launch until I get what I want and write down all the numbers
<discord-> R​urouniDonut. — It is a little bit tedious though
<_whitenotifier-edb> [Principia] pleroy labeled issue #2974: Crash when switching to a vessel without a flight plan - https://git.io/J31YE
<discord-> B​utcher. — I'm not 100% sure I am.
<discord-> e​gg. — which one of your cats wrote the script
* raptop meows at the cats
<discord-> B​utcher. — Angry cat is unamused.
<raptop> Butcher: will angry cat accept pets?
<discord-> B​utcher. — If she is in the mood.
<discord-> B​utcher. — She's my cat rather than a foster cat, a bit touchy at times. 😆
<raptop> fair enough
<discord-> P​aculino (ŝi/ri/she/they). — Your cat has big ears
<discord-> s​iimav. — Nono, this is what you call big ears:
<discord-> s​iimav. — https://i.imgur.com/RSuP4aZ.mp4
<discord-> l​pg. — those ears have a small head
<_whitenotifier-edb> [Principia] eggrobin synchronize pull request #2973: Documentation for a correctly-rounded cube root - https://git.io/J3BRj
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