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…
<paculino>
Out of curiosity, have any linked papers captioned here as ‹things Principia cannot do› predated Principia gaining that feature?
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<sichelgaita> I trust that, if raptop says that Principia cannot do it, there are good reasons. It's possible that some things that "Principia could do" have been implemented, although I must say that I didn't keep track.
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Reply to "paculino: Out of curiosity, have any linked papers captioned here as ‹things Principia cannot do› p..."
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<egg> Principia has not gained new physics in a long time… a long time.
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<ezsnack> solar radiation pressure when
<raptop>
aside from GR the things I list, it would all require something rather out of scope for principia (eg: radiation pressure, photon emission/YORP, tidal effects that consider bodies actively changing shape, outgassing...)
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<konno> 50$ gift https://e.vg/vhwPumjFq Steam Gift Activation: Redeem a Steam Gift Card or Wallet Code
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<Tivec> (also it isn't showing as semisynch right now, since i'm a little out of alignment over the time span, but... yeah
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<Tivec> i'd like to get it back to LAN 0 as quickly as I can, since I have other launches coming up
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<Tivec> only thing i seem to be able to do is a slightly phased orbit by lowering my apogee, can do with just a few m/s at the perigee, which will start moving me "backwards" on the orbital. if i understand it right, does this mean that my craft will, on the next pass of the ascending node (#1) be at 0.6 degrees?
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<Tivec> so if i do this burn, on my next orbit i would do a counter burn to reduce the drift?
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<Tivec> no wait, that's equatorial crossing.. hrm
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<egg> If you want to think about it as a drifting молния orbit, you should not let the analyser autodetect the recurrence. You want to set it to 2 revolutions to 1 day, and see how it drifts with respect to that nominal recurrence.
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<Tivec> hold on a second, i need to understand this. i'll disable the autodetect, 2 revolutions, 1 day
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<Tivec> but is the ascending pass the LAN for that pass? I don't understand that part..
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<Tivec> I mean, ascending nodes are on the equator aren't they?
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<egg> Over six days, the first northbound equatorial crossing that east of Greenwich will be around 97°,63, varying by the amount stated.
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<Tivec> okay, so to move my LAN, I want to get this number moving as I increase to the next odd pass in order?
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<egg> No.
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<egg> Your cycle has two passes, that’s it.
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<egg> They are 180° apart.
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<egg> Pick one, and stick to it.
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<egg> (effectively, the pass number is whether you are looking at the equatorial crossing before you go above Russia or the one before you go about North America.)
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<Tivec> okay, so this has nothing to do with the LAN at all then?
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<egg> But also, you don’t actually care about the LAN
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<egg> (Because LAN is really the celestial longitude, aka the RAAN, and if you care about aligning yourself with ground targets, you care about the terrestrial longitude)
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<egg> You are looking at the correct field if you want to move your ground track east or west.
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<Tivec> okay, so for my use, which is a constellation of four satellites in molniya orbits, I was originally going to launch them at LAN 0, 90, 180, 270, but that doesn't really matter here? I want them spaced out for best reception, so one satellite is always above the US
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Reply to "Tivec: okay, so for my use, which is a constellation of four satellites in molniya orbits, I was..."
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<egg> You want them on the same ground track, spaced out?
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<Tivec> yes that's the goal
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<Tivec> (i wish i could see the ground tracks....)
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<egg> In that case, they should all have the same longitude of ascending pass #1
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<egg> (but different right ascensions of the ascending node.)
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<Tivec> RAAN, which is the LAN readout here?
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Reply to "Tivec: (i wish i could see the ground tracks....)"
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<egg> Well, you can see the ECEF trajectory, which is just the 3D version of that.
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Reply to "Tivec: RAAN, which is the LAN readout here?"
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<egg> Yes.
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Reply to "egg: Well, you can see the ECEF trajectory, which is just the 3D version of that."
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<egg> So they should all be on the same noodle in ECEF.
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<Tivec> oaky, so the thing here is that my satellite was launched to LAN 0, but is now (after 100 days) is at 340. So it has drifted 20 degrees from its original
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<egg> Note the nodal precession field.
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<egg> RAAN is not constant.
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<Tivec> yeah -0.16 per day, so when I launch satellite #2, do I still launch to 90, or do I look at the one I am viewing now to see the original "0"?
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<egg> The latter. They will all precess in the same fashion.
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<Tivec> okay, so for this particular one if I was to launch today, I would not launch to 90, but rather launch to 90 - (360-340), or 70 degrees?
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<Tivec> and then burn at 270 arg.pe at the orbit that places the noodle in the same place
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<egg> I think so (in a teleconference so somewhat distracted.)
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<Tivec> no problems, you've helped me a bunch 🙂 i'll do a sim to see if that works actually 🙂
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<Tivec> oh! can I get principia to read out the numbers in seconds instead of days/hours/minutes/seconds? or do I just have to bring out the calculator
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<egg> Bring out the calculator
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<Tivec> haha okay, fair.
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<egg> Or just work in base 60
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<Tivec> well, was more hoping since they were saying "period for a molniya should be 718 minutes" and then I have to math that 😄
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<Tivec> 11h 58 minutes no?
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<Tivec> another thing i don't quite understand is how to make these orbits match a specific period. i get it that it changes over time, but i just don't know how to know that. like, do i want the mean sidereal period to be close to the target of 11h 58m over a longer period? i can get it there over like a few days, but as soon as i bump the time up to 100 days, it's off by seconds
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<egg> Don’t worry about the period, just make it match the [2 ; +0 ; 1] recurrence
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Reply to "egg: Don’t worry about the period, just make it match the [2 ; +0 ; 1] recurrence"
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<Tivec> oh, so the only numbers i need to watch are the ascending and descending passes, getting the +- down as low as i can?
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<egg> Yes.
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<egg> Over a suitably long analysis period (you want this to stay around for more than 6 days, so crank up that number.)
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<Tivec> yeah, i've put it up to 200 days now
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<Tivec> and it differs by 28 degrees sooooo i need to sort that 😛
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<Tivec> Would love pointers on what type of burn I need for that to be lowered. I’ve tried all directions and nothing really changes the difference over time on the ascending pass, it is sort of locked at 28 degrees
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<Tivec> Im probably not burning at the right spot here either. Been trying from perigee
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<Tivec> ugh, been at this for an hour now, can't get it working lol
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<Tivec> whatever i do i get an ascending pass that is like 24 degrees on the variance over 200 days.. if i go down to 10 days i have really low variance, at like 0.05 degrees, which is fine, that's a 6km variance but.. bump the same up to 200 days, it's 28 degrees and 3149km..