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--> <e​gg​> Hmm, why didn’t the notifier message make it through the bridge ?
<egg> meow
<egg> Maybe it doesn’t take notices ?
<raptop> Somehow the git notices are coming through the IRC side, but not the discord one. hrm
<egg> Well they originate from the IRC side.
<egg> _whitenotifier-d365 is actually here.
<raptop> That would help
<egg> meow
<egg> meow this is a notice
<queqiao--> <e​gg​> yeah it does not forward notices
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<queqiao--> <C​XG​28​27​> Is your maneuvering frame set to ECI, and plotting frame in Moon-earth-orbit?
<queqiao--> Reply to "f​lo​ui​d: are there any good resources for learning how to use the flight planner? I’m at the stage..."
<queqiao--> <e​zs​na​ck​> the answer is lunar transfer planner
<queqiao--> Reply to "f​lo​ui​d: are there any good resources for learning how to use the flight planner? I’m at the stage..."
<queqiao--> <J​ak​at​ha​n> Launching to the LAN of the moon is not sufficient with Principia. As ezsnack says, you're going to need to learn how to do out-of-plane transfers with Lunar Transfer Planner
<queqiao--> Reply to "e​zs​na​ck​: the answer is lunar transfer planner"
<queqiao--> <F​lo​ui​d> i didn’t see this, is it accessible from the flight planner (don’t have the game open rn)
<queqiao--> Reply to "C​XG​28​27​: Is your maneuvering frame set to ECI, and plotting frame in Moon-earth-orbit?"
<queqiao--> <F​lo​ui​d> from eci
<queqiao--> Reply to "F​lo​ui​d: i didn’t see this, is it accessible from the flight planner (don’t have the game open rn)"
<queqiao--> <J​ak​at​ha​n> It's a separate mod that is included with the express install. It is the crescent moon icon in the bar on the right.You put in your time of flight, and it will tell you either A.) What inclination you need to launc to right now to be in the proper orbit to reach the moon after the input flight time, or B.) how long until the next time you can launch due east and be in the right orbit to do the same.
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<queqiao--> Reply to "J​ak​at​ha​n: It's a separate mod that is included with the express install. It is the crescent moon ic..."
<queqiao--> <F​lo​ui​d> sweet thanks
<queqiao--> <L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​> Do anyone have the LCM of all planets in solar system's periods?
<queqiao--> <L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​> I wonder if I could get the base time back 1 LCM before so I can use some sort of StartUT stuff to get back to 1920s and don't get bugged out
<queqiao--> <L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​> I knew it should bee some #moddev-help stuff but I think only in this channel I could ask for math's and orbitals
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<queqiao--> <e​zs​na​ck​> Whats lcm
<queqiao--> Reply to "e​zs​na​ck​: Whats lcm"
<queqiao--> <L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​> Least common Multiple of all orbital periods of bodies inside rss
<queqiao--> <e​zs​na​ck​> wtf does that mean
<queqiao--> Reply to "e​zs​na​ck​: wtf does that mean ah i didnt read period, how is that useful anyways"
<queqiao--> <L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​> I can 1951-1-1 minus 1 LCM of UT and keep all planetary alightment the same. And then I can warp a few thousand years and get a 1920s or 30s start.
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> Yeah that’s going to be thousands if not tens of thousands of years in the past
<queqiao--> <G​oF​or​PD​I ​(l​es​s ​dr​ag​=m​or​e ​fa​st​er​)> Especially with the outer planets
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<raptop> egg: the bridge seems to have fallen over again
<egg> Yes, because of roadwork
<egg> I am trying to make it forward notices
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<egg> Bridge test
<egg> Bridge test via NOTICE
<egg> Hm. NOTICE still does not work.
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<egg> This is a notice.
<egg> OK, now it works.
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<raptop> 先輩？
<queqiao--> <e​gg​> Precisely.
<queqiao--> Reply to "L​im​ed​re​ad​_w​it​h_​no​_m​on​ey​: Least common Multiple of all orbital periods of bodies inside rss"
<queqiao--> <Q​ua​dr​up​ol​e🇵🇸🇨🇺> I don't think that's a well-defined quantity. The ratio of periods of any two major bodies in the solar system is a irrational number and a function of time due to perturbations. There can be no lcm.
<raptop> Yep. You can try to get something that almost works with Bode's law or the like, but that's semi-major axis not period...
<raptop> Alternatively, clearly you should go with one of those compact exoplanet systems where they're in resonances with eachother!
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<queqiao--> Reply to "Q​ua​dr​up​ol​e🇵🇸🇨🇺: I don't think that's a well-defined quantity. The ratio of periods of any two major bodie..."
<queqiao--> <C​la​ye​l> irrational? if its a ratio, then by definition it is not irrational
<queqiao--> <C​la​ye​l> i think you mean that its not an integer
<queqiao--> <C​la​ye​l> there IS an lcm for the real solar system, but iirc its several times the duration of the universe due to the ratios not being very clean
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<queqiao--> <F​lo​ui​d> hmm, still confused by what I'm doing wrong with my attempted lunar flyby. I've used the lunar transfer planner and waited until a window where the launch inclination was due east. I launched into a 250km x 250km orbit, and made a flight plan with a 3200 m/s tangent maneuver. Doesn't seem like it's anywhere near reaching the moon
<queqiao--> Reply to "C​la​ye​l: irrational? if its a ratio, then by definition it is not irrational i think you mean that..."
<queqiao--> <e​gg​> > irrational? if its a ratio, then by definition it is not irrational
<queqiao--> <e​gg​> No Clayel, that is not how this works.
<queqiao--> <K​ab​or​l> Hi everyone, in geosynchronous orbits: when both the "Maneuver Frame Selection" and "Plotting Frame Selection" are set to ECEF, the dotted planned orbit looks weird to me. But if I set "Plotting Frame Selection" to ECEF and keep "Maneuver Frame Selection" in ECI, I get a nice geosynchronous orbit around a specific point.This makes me realize I don’t fully understand what "Maneuver Frame Selection" does. Can someone help me
<queqiao--> <e​gg​> The manœuvre frame defines what « forward » means in the manœuvre. Changing it changes the manœuvre. In contrast the plotting frame is just about plotting, it does nothing.
<queqiao--> Reply to "F​lo​ui​d: hmm, still confused by what I'm doing wrong with my attempted lunar flyby. I've used the ..."
<queqiao--> <N​az​fi​b> You don't have your engines active, so it assumes you're going to use RCS for the burn; that means that the burn will take around 1h45m, and that's just too long for an efficient burn (more than a whole orbit).If you can stage to the configuration that will do the burn, do so before you create the flight plan (or rebase afterwards); if you cannot, you'll have to click "instant impulse", which will plan the burn as an instant Δv
<queqiao--> change (same as stock maneuver nodes do), and you'll have to start your burn a little before the timer goes to zero.
<queqiao--> Reply to "e​gg​: The manœuvre frame defines what « forward » means in the manœuvre. Changing it changes t..."
<queqiao--> <K​ab​or​l> Do you mean that the maneuver frame selection changes the reference plane?
<queqiao--> <e​gg​> No.
<queqiao--> <e​gg​> I mean that it changes which direction in space your vessel will point in when you have a purely tangent burn.
<queqiao--> <e​gg​> If you change the manœuvre frame and perform the same burn, something different will happen.
<queqiao--> Reply to "N​az​fi​b: You don't have your engines active, so it assumes you're going to use RCS for the burn; t..."
<queqiao--> <F​lo​ui​d> thank you! this was the key, finally have a plan that looks like it could work (also fixed the plotting frame) https://media.discordapp.net/attachments/480397772248580098/1346966247882887178/image.png?ex=67ca1b92&is=67c8ca12&hm=971f0ee1440941f70e0964d6157ca231cdd9196df00c889621e629b59489fd0a&
<queqiao--> <N​az​fi​b> You don't have your engines active, so it assumes you're going to use RCS for the burn; that means that the burn will take around 1h45m, and that's just too long for an efficient burn (more than a whole orbit).If you can stage to the configuration that will do the burn, do so before you create the flight plan (or rebase afterwards); if you cannot, you'll have to click "instant impulse", which will plan the burn as an instant Δv
<queqiao--> change (same as stock maneuver nodes do), and you'll have to start your burn a little before the timer goes to zero.
<queqiao--> <K​ab​or​l> Thanks egg.Then, could you share an example where this specific tool is useful?
<queqiao--> <e​gg​> If the manœuvre frame is the same as the plotting frame, then « forward » for your first manœuvre is « along the purple noodle ».
<queqiao--> <e​gg​> If you are looking at it in any other plotting frame, « forward » does not look like anything meaningful.
<queqiao--> <e​gg​> (But it might be useful, you might be looking at the outcome of a manœuvre that is logically defined in some other frame, but whose result is interesting in a different frame.)
<queqiao--> <N​az​fi​b> For getting to GEO, it is very useful to set the manoeuvre frame to ECEF. In that case, the burn at apogee will be -1850 m/s in the tangent direction. If you're using an ECI manoeuvre frame, you'll have to adjust the tangent and binormal Δv separately to zero-out the east/west and north/south movement of the satellite.
<queqiao--> <e​gg​> For instance, let’s say you circularize at 36000 km after an orbit-raising transfer from LEO, that is a prograde burn in ECI (as in stock), all straightforward. But the result is GEO, so you might want to look at it in ECEF. In ECEF, the direction of the burn might seem weird (in any case, it is not « forward »).
<queqiao--> <N​az​fi​b> For another example where you'd use a different manoeuvre frame and plotting frame: when doing an interplanetary transfer, you'll set the plotting frame as ECI (where the manoeuvre will be almost purely tangent, if you're in a good parking orbit); but you'll use the (Planet)-Sun-Orbit plotting frame to see your approach to the other planet.
<queqiao--> <F​lo​ui​d> this seems like it will be very very difficult to do precisely... Using an xasr-2 aerobee as my impulse engine and despite planning a maneuver with pretty much exactly my delta-v, I way overshot. I brought 70 m/s of correction motors and it didn't even come close to fixing my trajectory. Trying to do this with just a science core (which is why I couldn't stage until just before the maneuver)
<queqiao--> <F​lo​ui​d> I've gotten past this point in normal RP1 before but that was without principia, at least there the plotting was trivial. This has quite the learning curve
<queqiao--> <K​ab​or​l> I'll have to try all this. Thanks for the tips guys.
<queqiao--> <N​az​fi​b> MJ gives a pessimistic estimate of the Δv you'll get from your engines; in practice, it will always be more. Especially for early pressure-fed engines and solids, the variation can be quite large.
<queqiao--> <e​gg​> @but
<queqiao--> Reply to "F​lo​ui​d: hmm, still confused by what I'm doing wrong with my attempted lunar flyby. I've used the ..."
<queqiao--> <e​zs​na​ck​> you are plotting using RCS as you can see on the orange text
<queqiao--> <e​gg​> @Butcher how are the cats
<queqiao--> <e​zs​na​ck​> oh thats a old message lol
<queqiao--> Reply to "N​az​fi​b: MJ gives a pessimistic estimate of the Δv you'll get from your engines; in practice, it w..."
<queqiao--> <F​lo​ui​d> yeah I've realized this as well. I just don't know how to address it reliably at my current tech level. could maybe get slightly less variance with solids but the fact is still that even tiny variations cause a miss, and the upper stage can't just course correct with rcs
<queqiao--> <F​lo​ui​d> in my last playthrough I scaled the burn up to 3400 m/s since variations have less impact, I'll try doing that and swapping out for solids
<queqiao--> <F​lo​ui​d> the pioneer motors for correcting an overshoot were vital last time so I've kept them too
<queqiao--> <e​zs​na​ck​> perform guided tli :v
<queqiao--> <F​lo​ui​d> but avionics capable of that are so heavy my thor clone can't lift them and a 3200+ m/s kick stage to LEO
<queqiao--> <F​lo​ui​d> and this shouldn't require atlas, irl they did it with a stretched redstone
<queqiao--> <e​zs​na​ck​> you cant even plot an unguided burn with principia, you will need to math out the ignition timing and account for variance, as well as correcting the trajectory with correction motors after cutoff
<queqiao--> Reply to "F​lo​ui​d: yeah I've realized this as well. I just don't know how to address it reliably at my curre..."
<queqiao--> <N​az​fi​b> A faster transfer means that variations in Δv have less effect on the final trajectory. That means that if you include more Δv in your transfer stage, it will be more likely to hit.There is a way in MJ to measure the actual expended Δv — I believe it's the "Ascent stats" window; press the "MARK" button before executing your manoeuvre. That way, you can use a few simulations to get a better estimate of the actual Δv you
<queqiao--> have in your craft.
<queqiao--> <F​lo​ui​d> I use the early explorer approach of keeping my upper stage avionics and rcs attached to the kick stage until just before the maneuver, already used the instant impulse to correct for the fact it thought RCS was gonna do the burn
<queqiao--> Reply to "N​az​fi​b: A faster transfer means that variations in Δv have less effect on the final trajectory. T..."
<queqiao--> <F​lo​ui​d> didn't know about that last trick, interesting
<queqiao--> <F​lo​ui​d> with a 42 second burn time I start the burn at T-21 seconds, I know that's a piss poor approximation but doing the calculus myself is too much of a headache
<queqiao--> Reply to "F​lo​ui​d: I use the early explorer approach of keeping my upper stage avionics and rcs attached to ..."
<queqiao--> <e​zs​na​ck​> yea thats how you do it but principia wont be able to give you a useful prediction because you will shed mass
<queqiao--> Reply to "F​lo​ui​d: with a 42 second burn time I start the burn at T-21 seconds, I know that's a piss poor ap..."
<queqiao--> <e​zs​na​ck​> its usually 2/3 or at least good enough
<queqiao--> Reply to "e​zs​na​ck​: yea thats how you do it but principia wont be able to give you a useful prediction becaus..."
<queqiao--> <N​az​fi​b> That doesn't matter for an "instant impulse" burn.
<queqiao--> <e​zs​na​ck​> 42s is all but instant xd
<queqiao--> <e​zs​na​ck​> but anyways go for like 3400 actual expended dv and you will be fine with a relatively small correction
<queqiao--> Reply to "e​gg​: @Butcher how are the cats"
<queqiao--> <B​ut​ch​er​> Fine
<queqiao--> Reply to "e​zs​na​ck​: 42s is all but instant xd"
<queqiao--> <N​az​fi​b> In a 5400s orbit, a 42s burn is close enough to instant for the planning to still be accurate enough for most purposes. This is different for a several-minutes long burn, of course.
<queqiao--> <e​zs​na​ck​> at 3400dv 50s i had like 5s+- margin so yea not that important but still you cant be off by too much
<queqiao--> <F​lo​ui​d> also 100kg less than the aerobee version so there's something to be said for solids
<queqiao--> <e​zs​na​ck​> thats insanely hard to make work xd
<queqiao--> <F​lo​ui​d> what's wrong with it?
<queqiao--> <e​zs​na​ck​> 3 stages + decouplers is a ton of variance, even tho the sargent doesnt have much variance on its own
<queqiao--> <F​lo​ui​d> a single 11x cluster even with the upgraded fuel is 3100 m/s, so I'd have to upgrade to something like an altair to do it with a single engine
<queqiao--> <F​lo​ui​d> which ig the altair was the real life thor kick stage so maybe there's merit
<queqiao--> <e​zs​na​ck​> i mean you can try the 3 stager, its not impossible, just not fun
<queqiao--> Reply to "F​lo​ui​d: this seems like it will be very very difficult to do precisely... Using an xasr-2 aerobee..."
<queqiao--> <k​uz​in​at​0r​> Usually you wanna set your manoeuvre frame to the earth centered when you're in leo. This will produce the results as close as possible to the ones you expect when planning an interplanetary burn
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<queqiao--> Reply to "e​gg​: > irrational? if its a ratio, then by definition it is not irrational No Clayel, that is ..."
<queqiao--> <C​la​ye​l> how is it not? the orbital periods are not irrational numbers themselves (well, ok, there is always uncertainly in measurements, but lets assume you go down to the nanometer scale, that should be more than sufficient to get a lcm)