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->
⟨fiora⟩ i notice when i make an orbit about 50000km x 350km around earth at 90 inclination, it fairly rapidly decays periapsis-wise, lasting only a few months. why is this? what physical process is going on here, and how does one make a more stable orbit?
<queqiao->
⟨fiora⟩ * orbit with similar properties?
<queqiao->
⟨egg⟩ Hm, could it be the Лидов–古在 mechanism? CC raptop
<queqiao->
⟨fiora⟩ i was trying to google this and i found a mention of the fact that certain satellites avoid going directly over the pole due to orbital stability reasons
<queqiao->
⟨fiora⟩ but no explanations
<queqiao->
⟨fiora⟩ i was trying to google this and i found an uncited, offhand mention of the fact that certain satellites avoid going directly over the pole due to orbital stability reasons
<queqiao->
⟨fiora⟩ 古在.... kozai mechanism?
<queqiao->
⟨egg⟩ ⟪fiora⟫ 古在.... kozai mechanism? ⮪ And the other one is Lidov, yes.
<queqiao->
⟨egg⟩ Лидов’s paper goes in much greater depth than 古在’s IIRC.
<queqiao->
⟨thunkii⟩ i remember running a scenario in some old gravity simulator program where the moon was in a polar orbit. it crashed into the earth in some months.
<queqiao->
⟨egg⟩ ⟪thunkii⟫ i remember running a scenario in some […] ⮪ That would have annoying implications for the Principia release schedule. Don’t do that.
<queqiao->
⟨lamont⟩ so if "cos i" starts near zero then making it bigger would mean "sqrt(1-ecc^2)" got smaller which means ecc got pushed up closer to 1.0
<queqiao->
⟨fiora⟩ i have to say the translation of the Lidov paper i found has truly amazing word choices.
<queqiao->
"The orbit of the Earth satellite, into which the automatic interplanetary station turned after nearing the Moon, evolved in such a way f2s3) that, despite the initial height of perigee of the order of 47 . 103 km, during 11 revolutions the height of perigee, in accordance with the forecast obtained from calculation, became less that the radius of the Earth and the station discontinued its existence;"
<queqiao->
⟨fiora⟩ * *became less that the radius of the Earth and the station discontinued its existence*;"
<queqiao->
⟨fiora⟩ -f2s3)
<queqiao->
⟨egg⟩ yeah that is the Cleaves translation which we cite as [LC61] (we also cite the original as [Лид61]
<queqiao->
⟨egg⟩ The corresponding Russian text is
<queqiao->
⟨thunkii⟩ yeah i would translate the text that way too. a lovely feature of the russian language
<queqiao->
⟨thunkii⟩ or less formally, 'unexisted itself
<queqiao->
⟨thunkii⟩ * itself'
<queqiao->
⟨farrier_ds⟩ It's 'ceased to exist'
<queqiao->
⟨thunkii⟩ yes
<queqiao->
⟨thunkii⟩ that's probably a less hilarious word choice
<queqiao->
⟨egg⟩ ⟪fiora⟫ i have to say the translation of the […] ⮪ _pp_. 741 _sqq_. is where the conserved quantities are discussed btw.
<queqiao->
⟨thunkii⟩ ⟪egg⟫ *pp*. 741 *sqq*. is where the conserved […] ⮪ ...i've only ever seen et seq. for that, but i've been reading too many legal opinions lately
<queqiao->
⟨egg⟩ sqq., short for _sequunturque_ (plural of sq., short for _sequiturque_) might be more of a french style.
<queqiao->
⟨thunkii⟩ yeah that makes sense
<queqiao->
⟨the rocket science kid⟩ so this channel is the cat channel and the languages channel? (and the principia channel but that isn’t important)
<queqiao->
⟨thunkii⟩ yes, we put the moon in polar orbit so we could launch in-plane from Plesetsk and now egg is mad at me for ruining the update schedule
<queqiao->
⟨night_beast⟩ Okay, what am I missing here? I launched when the Lunar Transfer planner told me to, but it's going to take me 11 days and 3800 DV?
<queqiao->
⟨night_beast⟩ I only get to 131Mm with that 3800 DV. I'm really confused
<queqiao->
⟨fiora⟩ ⟪night_beast⟫ Okay, what am I missing here? I […] ⮪ the "launch now" inclination is -29.35, did you launch at that inclination?
<queqiao->
⟨night_beast⟩ no, the launch now I launched when the timer was at about 5 seconds, so it was at the right time. I may just have to restart because I don't understand how I can in any situation only get to 131Mm with 3.8K DV. I think my flight planning is just borked because none of this makes sense
<queqiao->
⟨night_beast⟩ reloading worked... guess something screwed up flight planning for some reason 🤷♂️
<queqiao->
⟨thunkii⟩ ⟪night_beast⟫ Okay, what am I missing here? I […] ⮪ set the maneuver frame to ECI
<queqiao->
⟨thunkii⟩ 3800 is enough to escape from low orbit
<queqiao->
⟨thunkii⟩ you might be thrusting in the wrong direction
<queqiao->
⟨night_beast⟩ I've already moved on, I reloaded and it was fine
<queqiao->
⟨thunkii⟩ ah
<queqiao->
⟨thunkii⟩ trying to reproduce a crash that's really irritating when playing on linux but i'm not sure how to do it
<queqiao->
⟨thunkii⟩ i'm doing what usually causes it to crash but it's not crashing 😦
<paculino>
Have you updated since it last happened?
<queqiao->
⟨thunkii⟩ nope
<queqiao->
⟨thunkii⟩ it happened a few times last night and i haven't updated
<queqiao->
⟨thunkii⟩ but seemingly not while journaling
<queqiao->
⟨night_beast⟩ Anyone have a good chart on Lagrange point distances? In stock I would put a 3 satellite com network in orbit around the moon, with all of them having the ability to reach earth. Since this is my first time with principia, I'm thinking of putting a com sat in the Earth / Lunar L1 point and giving my lunar orbiter network just enough juice to talk to that sat, but I'm not finding a good resource on how far away from the moon...
<queqiao->
... it is so I'm having trouble antenna planning it
<queqiao->
⟨thunkii⟩ it's about 1.5 Gm from Earth, so 1.1-1.9 Gm from the moon
<queqiao->
⟨the rocket science kid⟩ but the new lagrange frame shows equipotentials, it should be quite evident where the points are in that
<queqiao->
⟨the rocket science kid⟩ for the specific altitude though, that view is slightly less helpful
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<queqiao->
⟨the rocket science kid⟩ I've been fiddling with lunar orbiters, and are the mascons that bad that even 500km perilune results in a crash within days?
<queqiao->
⟨the rocket science kid⟩ This is an unguided probe so I can't quite target an exact frozen orbit (though I do have a liquid capture stage)
<queqiao->
⟨the rocket science kid⟩ * stage so maybe I can)
<queqiao->
⟨Damien⟩ ⟪the rocket science kid⟫ I've been fiddling with lunar orbiters, […] ⮪ tl;dr: yes
<queqiao->
⟨the rocket science kid⟩ anyway the first lunar orbit contract only wants apolune below 5000km and perilune above 20km, so I can have a perilune anywhere in that range
<queqiao->
⟨the rocket science kid⟩ Anyone have a _thing_ for a list of frozen lunar orbits?
<queqiao->
⟨night_beast⟩ My initial probe got sucked in and destroyed. I think the moons gravity is just so weak that the orbit gets thrown out of wack, which is why I'm looking at placing a new one @ L1
<queqiao->
⟨test_account⟩ ⟪the rocket science kid⟫ Anyone have a *thing* for a list of […] ⮪ it's pinned here in this channel, good luck deciphering it though 🙂
<queqiao->
⟨the rocket science kid⟩ oh I looked at the graph and my brain said “nope” and skipped it
<queqiao->
⟨the rocket science kid⟩ what is this e sin w thing
<queqiao->
⟨test_account⟩ i forgot again, e is likely eccentricity and i think w is some kind of sign so it can be ignored
<queqiao->
⟨the rocket science kid⟩ w means argument of periapsis according to wikipedia
<queqiao->
⟨test_account⟩ so yes, 90 or 270
<queqiao->
⟨the rocket science kid⟩ so eccentricity times sin w?
<queqiao->
⟨test_account⟩ hmm actually the argument of periapsis cannot be ignored then
<queqiao->
⟨test_account⟩ just use only circular orbits with e sin w = 0
<queqiao->
⟨the rocket science kid⟩ so any point on the graph is a frozen orbit?
<queqiao->
⟨test_account⟩ yes
<queqiao->
⟨night_beast⟩ Wait, that doesn't take into account inclination... How can that not be part of the equation?
<queqiao->
⟨the rocket science kid⟩ or I can choose some perilune, inclination and argument of perilune, and adjust e using the apoapsis height such that it is a frozen orbit
<queqiao->
⟨the rocket science kid⟩ ⟪night_beast⟫ Wait, that doesn't take into account […] ⮪ inclination is the x axis
<queqiao->
⟨the rocket science kid⟩ so "for any set of e and w, find the inclination that leads to a frozen orbit"
<queqiao->
⟨night_beast⟩ Got it, also it appears that around 85 degrees is good at any of those altitudes in that chart. Are those the only altitudes that are safe?
<queqiao->
⟨Damien⟩ ⟪egg⟫ Or the pinned graphs. ⮪ I'm pretty sure pinning anything other than cat pics is illegal
<raptop>
Well, this is why things like catterplot exist
<queqiao->
⟨Quadrupole⟩ ⟪night_beast⟫ Anyone have a good chart on Lagrange […] ⮪ Why L1? Surely you can get away with a single relay at L2 instead of L1+orbiters?
<queqiao->
⟨night_beast⟩ So, I thought about that, but L2 won't have LOS to L1 or earth, so I would need to put one at L4 or L5 to make the full network and I would have to have those 3 sats be powerful enough to reach each other, so my options are
<queqiao->
L1 with 3 small orbiters
<queqiao->
L2 & L4(or5) with 3 small orbiters
<queqiao->
3 large orbiters
<queqiao->
(I'm classifying large / small here based on if they can call earth themselves)
<queqiao->
⟨thunkii⟩ cant you use a halo orbit around l2?
<queqiao->
⟨night_beast⟩ Is L2 big enough for me to do that where I can just set it and forget it? I thought I would have to be too close to L2 for it to have LoS around the moon
<queqiao->
⟨kingparity⟩ L4 and L5 are stable the rest are not
<queqiao->
⟨kingparity⟩ i.e. for L1, L2, L3 you will need to do correction burns to keep it on track while for L4 and L5 you can just leave it there
<queqiao->
⟨night_beast⟩ for L1, L2, and L3, you need to do correction burns to keep it on the point, but it's my understanding you can "orbit" the point just fine
<queqiao->
⟨night_beast⟩ Very intriguing... It looks like the distance is 61347 km from the moon, do you know if that's "moon space high" or is that outside the bounds for moon science?
<queqiao->
⟨thunkii⟩ it dips in and out of the moon sphere
<queqiao->
⟨Quadrupole⟩ ⟪night_beast⟫ Very intriguing... It looks like the […] ⮪ I did L2 relay in a previous save, and it was in earth high. L2 is by definition on the edge of moon's SOI.
<queqiao->
Also halo orbits can have "huge" amplitudes, like the JWST:
<queqiao->
⟨night_beast⟩ How long did your L2 relay last before you had to course correct it (or it just got thrown from the orbit)?
<queqiao->
⟨Quadrupole⟩ Once per month. Each correction cost around 5 m/s iirc.
<queqiao->
⟨night_beast⟩ welp, no more timewarping 60 days into the future
<queqiao->
⟨Quadrupole⟩ * 1
<queqiao->
⟨night_beast⟩ It appears I don't have the communications tech level yet to do that efficiently. The best I have is the HG-61, and even that would require 41dBm on UHF. I could go S-Band, but then I have to manage targeting (or put 2 antenna on the craft, one targeted at the L2 com sat and 1 pointed at earth)
<queqiao->
⟨Quadrupole⟩ You can use the S-band 1.25 m antenna to simultaneously point to the lander and DSS. That's what I did.
<queqiao->
⟨night_beast⟩ * UHF (for moon to L2 communication).
<queqiao->
⟨Tink⟩ You cant have it lose communications en route until it can reach the l2 commsat?
<queqiao->
⟨Quadrupole⟩ You can use the S-band 1.25 m antenna […] ⮪ Then on the lander I have an S-band HG-5 that talks to the relay. It's more power-hungry than a TL2 antenna, but libration orbits are so cool.
<queqiao->
⟨night_beast⟩ ⟪Quadrupole⟫ You can use the S-band 1.25 m antenna […] ⮪ and then just as I orbit to the backside of the moon switch the targeting over on my lander to the L2 point sat... That shouldn't be too bad, and I guess my science orbiters can just loose connection when they go to the backside of the moon, and can just transmit when in los to earth
<queqiao->
⟨Quadrupole⟩ You can use the S-band 1.25 m antenna to simultaneously point to the lander and DSN. That's what I did.