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--> <O​sw​al​d> is there a way to set srbs as "active engines?" or do I have to eyeball it
<queqiao--> <C​la​ye​l> just have to eyeball it ya
<queqiao--> <F​al​co​n> only in 2D unfortunately, but still pretty fun
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<queqiao--> <k​uz​in​at​0r​> How do I make sure my craft's orbit crosses the planets orbit? I'm trying to get to Mercury using gravity assists. Since brute force plane change is not an option, I want to setup a resonant orbit. But I can't (reasonably) do it because no reference frame shows me the distance between the closest points of our trajectories
<queqiao--> <k​uz​in​at​0r​> So, before making requests for new features, I wanna hear your suggestions)
<queqiao--> <N​az​fi​b> Resonant orbits will be very obvious in the Mercury-Sun-Orbit reference frame.
<queqiao--> <N​az​fi​b> I guess if you want to know if your orbit goes closer and further to the Sun than Mercury's orbit, you could compare the perihelia and aphelia of both (does Principia show celestials' apsides? otherwise, you'll need to look those up online), in the Sun-centered Inertial reference frame?
<queqiao--> <k​uz​in​at​0r​> Since our orbits aren't coplanar, my only option is to meet at ascending/descending node. When I adjust my period at one of these points, I see my trajectory passing 20.000km above Mercury. Getting closer requires ridiculous amounts of deltaV. So I think the point where I try to adjust the period doesn't actually touch the mercury's orbit.
<queqiao--> <k​uz​in​at​0r​> But my only way to adjust it is by eyeballing in sun inertial frame
<queqiao--> <e​gg​> > no reference frame shows me the distance between the closest points of our trajectories
<queqiao--> <e​gg​> This is by design, distances are only shown with respect to something fixed. So a mercury-fixed frame is the way to go.
<queqiao--> <e​gg​> (MSO should indeed be appropriate here.)
<queqiao--> <k​uz​in​at​0r​> MSO only shows the distance to Mercury itself, not the trajectory
<queqiao--> Reply to "k​uz​in​at​0r​: Since our orbits aren't coplanar, my only option is to meet at ascending/descending node...."
<queqiao--> <N​az​fi​b> Yeah, you really want to use the MSO reference frame for this. I don't think a maneuver at the relat... https://paste.gg/p/anonymous/4097a1badf714c55915175f1a981d7d2
<queqiao--> <k​uz​in​at​0r​> I don't see how to achieve what I want here.
<queqiao--> <e​gg​> You are phrasing what you want in heliocentric terms (distance between heliocentric trajectories), which is probably making your life difficult.
<queqiao--> <k​uz​in​at​0r​> Picturing heliocentric frame is much easier)
<queqiao--> <N​az​fi​b> I guess the most important thing is this: by the time you're in a solar orbit, it is too late to mak... https://paste.gg/p/anonymous/9523880121674c9c8d1bb6c2c9537cf1
<queqiao--> <k​uz​in​at​0r​> But how to intercept Mercury efficiently? My probe now is in an orbit with PE lower than the mercury's AP. Planes don't match, because I didn't bother waiting for Venus to be in the mercury's an/dn when I arrive.
<queqiao--> <k​uz​in​at​0r​> So my only option is the point where our trajectories intercept
<queqiao--> <e​gg​> It sounds like you may have painted yourself into a corner?
<queqiao--> Reply to "k​uz​in​at​0r​: But how to intercept Mercury efficiently? My probe now is in an orbit with PE lower than ..."
<queqiao--> <N​az​fi​b> After your final Venus flyby, you should have been on a trajectory that (nearly) encounters Mercury. If that's not the case, then you will indeed need enormous amounts of Δv to change that.
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> all of this has to be planned before liftoff because at every flyby you already need to be at the correct speed
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> the time scales are also in the order of years if you mess up so its not really an option xd
<queqiao--> Reply to "e​gg​: It sounds like you may have painted yourself into a corner?"
<queqiao--> <k​uz​in​at​0r​> I really just need to make our trajectories cross each other. If I achieve that, a resonant orbit would do the rest.
<queqiao--> Reply to "N​az​fi​b: After your final Venus flyby, you should have been on a trajectory that (nearly) encounte..."
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> not only it should encounter mercury, but encounter it at a sensible speed that allows the successive encounters, and so on :v
<queqiao--> Reply to "k​uz​in​at​0r​: I really just need to make our trajectories cross each other. If I achieve that, a resona..."
<queqiao--> <N​az​fi​b> A resonant orbit would mean that your position relative to Mercury is the same every orbit; you'll never get closer to it. I don't think that is what you want.
<queqiao--> Reply to "N​az​fi​b: A resonant orbit would mean that your position relative to Mercury is the same every (cou..."
<queqiao--> <k​uz​in​at​0r​> Maybe I use the wrong term. What I mean is I can adjust the period so we meet at this point several orbits later
<queqiao--> <N​az​fi​b> Yeah, big orbital period changes need a flyby or a large Δv manoeuvre. There's no way around that.
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> this is a quick how to for gravity assists :v
<queqiao--> <k​uz​in​at​0r​> I have deltaV to setup it. And plenty more for consecutive manoeuvres
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> when multiple assists you need to match all the travel times from 1 body to the other
<queqiao--> <k​uz​in​at​0r​> But I need to be able to cross the orbit in the first place.
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> thats not a problem to begin with because you should meet mercury directly after venus :v
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> but what you want is the venus assists to put you in a coplanar but resonant orbit with mercury ig?
<queqiao--> Reply to "e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t: but what you want is the venus assists to put you in a coplanar and resonant orbit with m..."
<queqiao--> <k​uz​in​at​0r​> Venus can't put me in a coplanar orbit whenever I want. It should be in the mercury's an/dn to be able to do it
<queqiao--> Reply to "k​uz​in​at​0r​: Venus can't put me in a coplanar orbit whenever I want. It should be in the mercury's an/..."
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> which is why we use multiple gravity assists planners xd
<queqiao--> Reply to "e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t: which is why we use multiple gravity assists planners xd"
<queqiao--> <k​uz​in​at​0r​> That's not a useful advice. I know how to achieve what I want - I just need the tools to do it.
<queqiao--> Reply to "k​uz​in​at​0r​: But I need to be able to cross the orbit in the first place."
<queqiao--> <N​az​fi​b> Just "crossing" the orbit (i.e. having a lower perihelion and a higher aphelion) is not nearly enough to be able to get to a flyby. You also need your line of nodes to line up with the point where you cross that orbit — this is the part that requires far too much Δv to do. After that, assuming you can wait long enough, getting a flyby should be possible (thoug it may be after many orbits).
<queqiao--> Reply to "k​uz​in​at​0r​: That's not a useful advice. I know how to achieve what I want - I just need the tools to ..."
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> the tools is mercury sun orbit reference frame tho, with a long enough flight plan you will see the encounter
<queqiao--> <N​az​fi​b> In any case, the most efficient place to adjust your orbital altitude is at perihelion. A burn at the relative AN/DN will probably not help.
<queqiao--> <k​uz​in​at​0r​> I feel you just don't understand what I'm talking about. By "crossing the orbit" I mean they're gonna hit each other after long enough time.
<queqiao--> <k​uz​in​at​0r​> So they both have a point in their trajectories with exactly the same coordinates
<queqiao--> Reply to "k​uz​in​at​0r​: I feel you just don't understand what I'm talking about. By "crossing the orbit" I mean t..."
<queqiao--> <N​az​fi​b> In that case, open the MSO reference frame; crank the flight plan duration up to several years; and see if your Mercury approaches get closer or further away. Try a manoeuvre at aphelion or perihelion and see how the trajectory changes.
<queqiao--> <B​ut​ch​er​> My solution to this was to build a bigger rocket. :p
<queqiao--> <B​ut​ch​er​> My Mercury landers were the largest things I launched iirc.
<queqiao--> <k​uz​in​at​0r​> I actually managed to do it) Managed to trick the optimizer into finding the trajectories interception point. https://media.discordapp.net/attachments/480397772248580098/1417522475264118814/image.png?ex=68caca2e&is=68c978ae&hm=e850253beb89bb9701a0f420e01aa46d5bd7e19405f462fe0a2bab4fc5452b10&
<queqiao--> Reply to "k​uz​in​at​0r​: I feel you just don't understand what I'm talking about. By "crossing the orbit" I mean t..."
<queqiao--> <e​gg​> Not if they are resonant. Which is why you want to look at MSO, as Nazfib said.
<queqiao--> <e​gg​> The heliocentric trajectories aren’t any more real than the trajectories in another reference frame, and their apparent intersection when flattening time is meaningless on its own.
<queqiao--> Reply to "e​gg​: Not if they are resonant. Which is why you want to look at MSO, as Nazfib said."
<queqiao--> <k​uz​in​at​0r​> This is MSO. How do I use it to figure out if the Mercury's and the craft's trajectories intersect(except at the encounter itself)?
<queqiao--> <k​uz​in​at​0r​> Also, the highlighted nodes are hardly usable(I'm definitely not in a retrograde orbit) https://media.discordapp.net/attachments/480397772248580098/1417525515706830848/image.png?ex=68cacd03&is=68c97b83&hm=cfda5eafb0fbe9e665d16ed489ae0bcb2de05f5a8a76df0596e5d3a867f40790&
<queqiao--> <e​gg​> > figure out if the Mercury's and the craft's trajectories intersect
<queqiao--> <e​gg​> You don’t, because that is not actually a relevant question.
<queqiao--> <e​gg​> What you care about is hitting Mercury, not being out in space in a place where, in the heliocentric frame, Mercury will be at some other time.
<queqiao--> <e​gg​> So as Nazfib said, you plot for longer in MSO, and you see whether you are getting closer to Mercury (which does not move).
<queqiao--> <e​gg​> as for> (I'm definitely not in a retrograde orbit)
<queqiao--> <e​gg​> Sure, why do you think you are?
<queqiao--> Reply to "e​gg​: So as Nazfib said, you plot for longer in MSO, and you see whether you are getting closer..."
<queqiao--> <k​uz​in​at​0r​> It only really works in coplanar orbits. When in a coplanar orbit, principia is great. But it doesn't help me to setup an encounter when the planes differ.
<queqiao--> Reply to "e​gg​: as for> (I'm definitely not in a retrograde orbit) Sure, why do you think you are?"
<queqiao--> <k​uz​in​at​0r​> 179 degree inclination
<queqiao--> <e​gg​> That angle isn’t the inclination of a Kepler orbit.
<queqiao--> <e​gg​> It’s the angle of your trajectory in that frame, which isn’t an ellipse, with respect to the reference plane.
<queqiao--> <k​uz​in​at​0r​> Maybe. But I don't really know how to use this number)
<queqiao--> Reply to "k​uz​in​at​0r​: I actually managed to do it) Managed to trick the optimizer into finding the trajectories..."
<queqiao--> <e​gg​> This is thinking about it backward. The optimizer finds how to hit the planet. Hitting the planet efficiently will, among other things, cause the heliocentric trajectories to intersect; but that isn’t what it finds, nor is it what you ultimately want.
<queqiao--> <k​uz​in​at​0r​> But you aren't telling me how to setup an encounter when in non-coplanar orbits. "Plotting longer in MSO" doesn't do anything, because you need to setup a close enough encounter to enable optimizer to find it. Without a trick with an auxiliary manoeuvre, optimizer would only find ridiculously expensive manoeuvres.
<queqiao--> <e​gg​> Right, it’s a local optimizer.
<queqiao--> <e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t> Have you considered posting at the very least a screenshot of your current situation?
<queqiao--> <k​uz​in​at​0r​> I'm in a 3/2 resonant orbit. As you can see, it requires some really small adjustments to setup the next encounter) The third pass(not planned yet) should finish the plane adjustment https://media.discordapp.net/attachments/480397772248580098/1417532011744067634/image.png?ex=68cad310&is=68c98190&hm=397f425ac5b907bbc78cfdb0e486b45d85354150b9b164c6f8951f3e47a579e4&
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<raptop> technically this counts as things to do in Principia: https://arxiv.org/abs/2509.10579
<queqiao--> <d​od​ge​th​is​du​ck​> I play stock with OPM. No matter what I do, I can't get a stable polar Mun orbit. Is that normal, or am I doing something wrong?
<queqiao--> <d​od​ge​th​is​du​ck​> I can get a stable orbit below about 70 degree inclination, but not above that.
<queqiao--> Reply to "e​zs​na​ck​ -​ b​oo​st​er​ t​an​k ​ap​ol​og​is​t: Have you considered posting at the very least a screenshot of your current situation?"
<queqiao--> <k​uz​in​at​0r​> I'm back at PC. Here is my trajectory from different points of view. It takes 3 passes to almost match the planes. Gonna start lowering the AP during the next encounters. https://media.discordapp.net/attachments/480397772248580098/1417620668471840891/1.png?ex=68cb25a1&is=68c9d421&hm=b4688f3131ef77b2f059332424041b99b939bb1cea921f8924795078eba32a45&
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