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-> ⟨Infernal⟩ does the mechjeb landing guidance work with principia?
<queqiao-> ⟨Soviet Onion⟩ it should
<queqiao-> ⟨Soviet Onion⟩ when you are landing, you are close to the body's surface, so n-body doesn't really matter as much as it does elsewhere, does it ?
<queqiao-> ⟨Soviet Onion⟩ unless you are talking about landing from orbit 😏
<queqiao-> ⟨Oslov⟩ ⟪sichelgaita⟫ (Tempted to kill the hack gravity hack.) ⮪ If EL works now I'd be fine with it, but otherwise... nooooooo
<queqiao-> ⟨Oslov⟩ I had some Principia fun today, forgot about debri and had nearly 100 pieces of low orbit debri in my save, and surprisingly, was still doing around 30FPS. Was trying to figure out why my game was slow though and that was it
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<queqiao-> ⟨zephyr⟩ Ok, I've been working on timing tli's for a while now and was wondering why I keep getting this trajectory? Is it a known one/does anyone have a paper on this that I could read?
<queqiao-> ⟨von Kerman⟩ This trajectory apparently goes outside the Moon's orbit
<queqiao-> ⟨zephyr⟩ Yeah, I don't know how I keep finding it
<queqiao-> ⟨zephyr⟩ Like I don't know if I'm just picking the worst possible day and this is the best transfer I have or if I'm just mis-timing my ascent
<queqiao-> ⟨PlasticGuy⟩ i _think_ if you have launched at the wrong time, a higher orbit that goes past the moon's before returning to it ends up with that sort of trajectory
<queqiao-> ⟨von Kerman⟩ are you launching roughly in plane of the moon?
<queqiao-> ⟨zephyr⟩ nah, pretty sure my relative inclination pre launch was like 22 degrees
<queqiao-> ⟨zephyr⟩ ⟪PlasticGuy⟫ i *think* if you have launched at the […] ⮪ Ok, good to know that this isn't just the worst case on some days
<queqiao-> ⟨PlasticGuy⟩ yeah, the trip ends up being a few days longer, but the overall dV change isnt much
<queqiao-> ⟨zephyr⟩ but not 12 days right?
<queqiao-> ⟨von Kerman⟩ Could it be that this kind of trajectory is _always_ possible? No matter when you launch, you can still find something like that
<queqiao-> ⟨PlasticGuy⟩ 12 days sounds about right to me
<queqiao-> ⟨PlasticGuy⟩ as in overall, not 12 more days
<queqiao-> ⟨zephyr⟩ Yeah, this trajectory is about 12 days long
<queqiao-> ⟨zephyr⟩ so a "wrong time" launch not a "wrong day" launch?
<queqiao-> ⟨von Kerman⟩ wrong datetime launch
<queqiao-> ⟨von Kerman⟩ can't separate one from the other
<queqiao-> ⟨zephyr⟩ I was under the assumption that you always get at least 1 launch per day
<queqiao-> ⟨zephyr⟩ with some days being better than others
<queqiao-> ⟨zephyr⟩ +when perfectly timed
<queqiao-> ⟨von Kerman⟩ yes, in this case there no wrong day launches, only wrong time
<queqiao-> ⟨von Kerman⟩ but I don't think trajectories going past the moon's orbit are even considererd
<queqiao-> ⟨von Kerman⟩ * considered
<queqiao-> ⟨von Kerman⟩ there are windows each day for direct transfers not going past the orbit of the moon
<queqiao-> ⟨zephyr⟩ i mean there's the free return but that's not that much past the moon i don't think
<queqiao-> ⟨von Kerman⟩ well, free return doesn't take you on that long loop
<queqiao-> ⟨zephyr⟩ ok, time to actually read that atlas-surveyor paper I found
<queqiao-> ⟨zephyr⟩ before I have to start my run over again due to poor launch timings
<queqiao-> ⟨von Kerman⟩ i just keep using my method of catching the moon at the node, it works
<queqiao-> ⟨PlasticGuy⟩ im pretty sure there are only perfect moon transfers each day if you can reach the same orbital plane
<queqiao-> ⟨von Kerman⟩ what does perfect mean?
<queqiao-> ⟨PlasticGuy⟩ as in minimal dV cost, all you have to do is raise the AP
<queqiao-> ⟨von Kerman⟩ well, dV cost varies, but don't think it will ever go above 3200
<queqiao-> ⟨von Kerman⟩ and yes, the burn is always directly prograde
<queqiao-> ⟨von Kerman⟩ and you don't need to be in the same plane, you need your orbital plane to intersect the moon's plane at some point and meet the moon at that point
<queqiao-> ⟨von Kerman⟩ but they always intersect at some time of the day, right?
<queqiao-> ⟨zephyr⟩ I've gotten that far, now I've just got to get to the point where I can get that intersection "asc/desc" nodes in the right spot
<queqiao-> ⟨von Kerman⟩ well, dV cost varies, but I don't think it will ever go above 3200
<queqiao-> ⟨zephyr⟩ Also, lost that paper now but my trajectory "looks like" (note: i suck at orbital mechanics and am new at this) a ballistic-lunar-transfer, a way to reduce the capture velocities for orbital insertion by the looks of it.
<queqiao-> ⟨pEdro⟩ look at it in into earth orbit first
<queqiao-> ⟨pEdro⟩ +frame
<queqiao-> ⟨zephyr⟩ will do, exited the game so I didn't just run the mission as is
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<queqiao-> ⟨zephyr⟩ so this is definitely an "overshot the moon" trajectory
<queqiao-> ⟨zephyr⟩ so launching when time till ascending node is 0 means that there isn't a good transfer but there is a weird one this time
<queqiao-> ⟨pEdro⟩ only slightly, ballistic transfers go much further out
<queqiao-> ⟨zephyr⟩ yeah, i figured that when the paper was talking about perturbations from the sun
<queqiao-> ⟨pEdro⟩ Theres a pdf floating about that has fancy graphs for ballistic and hohmann transfers
<queqiao-> ⟨pEdro⟩ ill post it if i can find it again
<queqiao-> ⟨zephyr⟩ currently working my way through this
<queqiao-> ⟨zephyr⟩ got a lot of details on most things, but nothing on actually predicting when the moon's antipode is
<queqiao-> ⟨zephyr⟩ hoping mechjeb's launch to target lan is good enough
<queqiao-> ⟨zephyr⟩ aaand it's trying to dogleg
<queqiao-> ⟨zephyr⟩ * dogleg, thanks mechjeb
<queqiao-> ⟨zephyr⟩ ok, doing some manual timing and I've managed to shave the transfer down to 8 days
<queqiao-> ⟨zephyr⟩ and the tli's on the right node now (the one closer to the launch and not the far one)
<queqiao-> ⟨Serina⟩ How do you save hack the orbits or cheat them
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<queqiao-> ⟨zephyr⟩ I'm just reverting to launch in a sim everytime
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<queqiao-> ⟨zephyr⟩ I'm hoping to figure out how to actually time these but I might just write down a launch time if it comes down to it
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<queqiao-> ⟨Serina⟩ Nvm
<queqiao-> ⟨pEdro⟩ you can just copy the kOS code and translate it into a excel sheet
<queqiao-> ⟨zephyr⟩ I'm trying not to use the kOS code, and learn the mechanics. Though I am holding "just reverse engineering the kOS script" as the last step
<queqiao-> ⟨pEdro⟩ what youre currently doing sounds like trial and error, which doesnt seem very productive
<queqiao-> ⟨pEdro⟩ if you want to figure it out yourself, coming at the problem from the coding side of things is advisable
<queqiao-> ⟨zephyr⟩ It's trial and error w/ research until I find a pattern
<queqiao-> ⟨pEdro⟩ you dont need a pattern, you need to define your goals with higher precision
<queqiao-> ⟨zephyr⟩ My goal is to understand how lunar launch windows are calculated?
<queqiao-> ⟨pEdro⟩ i meant put your goal into numbers
<queqiao-> ⟨pEdro⟩ * numbers, numbers are good because math is magic
<queqiao-> ⟨zephyr⟩ tbh im unsure about those too, hence the trial and error + research
<queqiao-> ⟨zephyr⟩ I'd assume ~3 days for the tli from RSS mechanics
<queqiao-> ⟨zephyr⟩ but I have no idea how realistic that is from different launch sites/windows
<queqiao-> ⟨pEdro⟩ 3 days is a good estimate
<queqiao-> ⟨zephyr⟩ so right now I'm just simming out a different number of launch timings to get a good intuition for things
<queqiao-> ⟨pEdro⟩ what you want is the LAN of your parking orbit, the orbit needs to be so that your ascending/decending nodes line up with the position of the moon in 3 days
<queqiao-> ⟨zephyr⟩ I get that part already
<queqiao-> ⟨pEdro⟩ at that point id switch over to excel, run some numbers
<queqiao-> ⟨zephyr⟩ Yeah, but lan already varies by launch azimuth
<queqiao-> ⟨zephyr⟩ +and time of day
<queqiao-> ⟨zephyr⟩ and I'd prefer to just sim that in python
<queqiao-> ⟨Nazfib⟩ Basically, you need to:
<queqiao-> - Determine the vector from the center of the Earth to where the moon will be at (T+3 to 4 days)
<queqiao-> - Determine the vector from the center of the Earth to your launch site at time T
<queqiao-> - The cross product between these two vectors points perpendicular to the plane of your parking orbit
<queqiao-> ⟨zephyr⟩ If the cross product between these vectors is perpendicular to the parking orbit isn't that the same as saying that the parking orbit is in the same plane as the the earth->site and earth->moon vectors?
<queqiao-> ⟨Nazfib⟩ Yes, exactly
<queqiao-> ⟨zephyr⟩ and in this case the inclination is "fixed" at the inclination of my launch site?
<queqiao-> ⟨pEdro⟩ ideally yes
<queqiao-> ⟨zephyr⟩ I'm speed running and my lv can't really do more
<queqiao-> ⟨pEdro⟩ * yes, its whats most efficient
<queqiao-> ⟨zephyr⟩ I assume that launching to a given LAN is dependant on T unless you want to dogleg
<queqiao-> ⟨Nazfib⟩ The inclination is _not_ fixed. At one specific time-of-day the inclination will be equal to the lowest absolute value of (launch site latitude, moon latitude), and at other times it will be higher. However, by varying T, you should be able to find this time where they are equal.
<queqiao-> ⟨Nazfib⟩ +(and the LAN)
<queqiao-> ⟨zephyr⟩ is it not highest?
<queqiao-> ⟨zephyr⟩ * highest(launch site lat, moon lat)?
<queqiao-> ⟨Nazfib⟩ Sorry, yes highest.
<queqiao-> ⟨zephyr⟩ yeah, i meant that in my specific case my LV doesn't really have the margin to send the impactor to any inclination other than the one provided by my launch site
<queqiao-> ⟨zephyr⟩ which is why fixed was in quotes
<queqiao-> ⟨zephyr⟩ If I launch due east is the lan of my orbit the same as the lan of my launch site?
<queqiao-> ⟨zephyr⟩ Or do I have to correct for time til orbit?
<queqiao-> ⟨zephyr⟩ * until
<queqiao-> ⟨Nazfib⟩ If you launch east, the LAN will be (celestial longitude of launch site - 90⁰) (if you're in the northern hemisphere). But the celestial longitude varies by 360⁰ over the course of a day.
<queqiao-> ⟨zephyr⟩ If i use KER's relative lan will the celestial longitude cancel out?
<queqiao-> ⟨zephyr⟩ +Apologies if you don't use ker, I'm currently trying to experiment and figure this out on my end
<queqiao-> ⟨Nazfib⟩ I'm not sure what KER means by relative LAN, sorry.
<queqiao-> ⟨zephyr⟩ Sorry it's actually time to relative ascending node of launch site
<queqiao-> ⟨zephyr⟩ * site?
<queqiao-> ⟨zephyr⟩ It might just be a weird measure that makes no sense
<queqiao-> ⟨zephyr⟩ * sense, but from what I can see I am about 90 degrees out of phase for my tli's
<queqiao-> ⟨zephyr⟩ * tli's, so that might be something I need to correct for
<queqiao-> ⟨Nazfib⟩ Yeah, that will probably not help: it is the time until AN between your current orbit and the target orbit, but on the launch site your "orbit" is basically a very narrow ellipse all the way to the center of the Earth. It won't mean anything until you are actually in orbit.
<queqiao-> ⟨zephyr⟩ It does match with the mechjeb "launch to plane/lan" timer
<queqiao-> ⟨zephyr⟩ * timer, but I found the launchsite lan and the target lan
<queqiao-> ⟨Nazfib⟩ Basically, you need to: - Determine the […] ⮪ In any case, this should allow you to write a quick script to calculate inc and lan for different launch times; plot them and select the LAN at minimum inclination. As far as I know, this is also basically what the kOS script does.
<queqiao-> ⟨zephyr⟩ yeah, I think using the KER time to relative AN/DN timers was throwing me off
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<queqiao-> ⟨zephyr⟩ Ok, now using something resembling the correct values I can now do a 5/6 day tli with about 150m/s less dv
<queqiao-> ⟨zephyr⟩ I think this might just be down to a bad time of transfer as I'm currently just using 3 days