raptop changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Gateaux. We currently target 1.8.1, 1.9.1, and 1.10.1. <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… | <egg> also 4e16 m * 2^-52 is uncomfortably large
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<_whitenotifier-9244> [Principia] Success. Build finished. - http://casanova.westeurope.cloudapp.azure.com:8080/job/Principia/4667/
<_whitenotifier-9244> [Principia] Pending. Building… - http://casanova.westeurope.cloudapp.azure.com:8080/job/Principia/4668/
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<discord-> n​9gaming. — Is anyone aware how long a 119km polar lunar orbit will remain stable? I could see a few days into the future and noticed some degradation already
<discord-> [​experimentalshells?]. — Depends on your parameters, like eccentricity, inclination, etc.
<discord-> [​experimentalshells?]. — I can't predict that for sure, but I do have something that you might like.
<discord-> n​9gaming. — *excite*
<discord-> [​experimentalshells?]. — You don't need to read the whole paper, the only thing that matters is that there's a frozen orbit around the Moon with parameters
<discord-> [​experimentalshells?]. — a = 6541.4 km
<discord-> [​experimentalshells?]. — e = 0.6
<discord-> [​experimentalshells?]. — i = 56.2°
<discord-> [​experimentalshells?]. — ω = 90°
<discord-> [​experimentalshells?]. — You don't need to read the whole paper, the only thing that matters is that there's a frozen orbit around the Moon with parameters
<discord-> [​experimentalshells?]. — a = 6541.4 km
<discord-> [​experimentalshells?]. — e = 0.6
<discord-> [​experimentalshells?]. — i = 56.2°
<discord-> [​experimentalshells?]. — ω = 90° (argument of periapsis) (edited)
<discord-> n​9gaming. — Definitely going to put *something* in that orbit thank you
<discord-> B​utcher. — That's pretty eccentric.
<_whitenotifier-9244> [Principia] 13-potatos-why opened issue #2810: Lighter version of principia. - https://git.io/JIOTO
<umbralraptop> hat's certainly a comment
<umbralraptop> Anyway, obviously one should use dark mode on your local supercomputer
<discord-> T​ransparent_Elemental. — what frame of reference should i use if i'm returning from the moon and want to reenter in the atmosphere? i'm noticing that my periapsis drifts a bit from what the flight plan shows
<discord-> [​experimentalshells?]. — ECI
<discord-> S​tonesmile. — I usually set it uo using MCEA(?) and fine tune it with ECI
<discord-> S​tonesmile. — I usually set it up using MCEA(?) and fine tune it with ECI (edited)
<discord-> T​ransparent_Elemental. — I used KCI i think (kerbal centered inertial), but it still drifted from 24 km to -19
<discord-> S​tonesmile. — I assume no RCS was firing to keep you pointed the right way?
<discord-> T​ransparent_Elemental. — no
<discord-> T​ransparent_Elemental. — I didn't have rcs at all, it was just a capsule-fuel-engine craft and it was happening during timewarp, not that i'm surprised that it drifts it's just that the end result didn't match
<discord-> S​tonesmile. — Maby try it again? I haven't noticed any drift from the prediction in RSS, so should be even better in stock
<discord-> B​utcher. — Me either, I can burn for a 60km pe reentry from moon orbit and not need to correct.
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<discord-> B​uilderbast. — how do I calculate the time a ground station is in contact with a satellite in a molniya orbit, when the apogee is directly above the ground station?
<discord-> B​uilderbast. — not neccesarily principia related, but most orbital mechanics nerds hang out here 🙂
<discord-> S​tonesmile. — Do you assume contact as soon as the satellite is above the horizon for the ground station?
<discord-> B​uilderbast. — @Stonesmile above the horizon
<discord-> B​uilderbast. — basically the time between those two yellow dots
<discord-> B​uilderbast. — I can't remember how to find out at what exact orbital radius the orbit intersects the horizon, or how to calculate the time spent between those points
<discord-> S​tonesmile. — If you can calculate the angle formed by the sat, the center of earth and the ground station, then you can use keplers laws to get an estimate
<discord-> B​uilderbast. — alright lemme see
<discord-> B​uilderbast. — theres en equilateral triangle connecting the sat, the center of (in this case mars) and the ground station
<discord-> B​uilderbast. — not sure how to calculate the rest at that point
<discord-> B​uilderbast. — im gonna grab my notebook real quick
<discord-> S​tonesmile. — The area that the sat sweeps should be a proportional part of the orbital period
<discord-> B​uilderbast. — yeah thats conservation fo angular momentum right?
<discord-> S​tonesmile. — Might be, I just remember it as Kepler's second law 😅
<discord-> B​uilderbast. — yep thats the one
<discord-> B​uilderbast. — I now know how to calculate the time spent between two true anomalies
<discord-> B​uilderbast. — but I still have no clue how to calculate at what true anomaly the sat will be directly at the horizon for the ground station
<discord-> B​uilderbast. — basically this is the big question now
<discord-> S​tonesmile. — That depends on the specific orbit, not sure about that
<discord-> B​uilderbast. — yeah, if it helps, the peripiapsis is 6821199.986 M
<discord-> B​uilderbast. — apoapsis is 9389500
<discord-> B​uilderbast. — around mars
<discord-> B​uilderbast. — and the apoapsis is right above the ground station
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<discord-> B​uilderbast. — wait I can maybe use circular orbits, that would be easier and that gives the mean anomaly
<discord-> B​uilderbast. — which can be converted to true anoamly
<discord-> B​uilderbast. — gotem
<UmbralRaptor> something something mean anomaly → eggcentric anomaly → true anomaly
<UmbralRaptor> wait, it would go in the other direction for time?
<discord-> B​uilderbast. — orbital mechanics is so fun, but so complicated lol
<UmbralRaptor> It's fine. M = E - e•sin(E) is a famously simple to solve equation
<discord-> B​uilderbast. — no thats what im doing
<discord-> B​uilderbast. — I've gotten the mean anomaly by using a circular orbit, now using that equation to solve for the 🥚centric anomaly, and then using that to solve for true anomaly
<discord-> B​uilderbast. — then using conservation of angular momenten to calculate the time spent between those two true anomalies
<discord-> B​utcher. — Hmm, that's new...
<discord-> B​utcher. — `F1204 15:15:16.804889 9812 orbit_recurrence_body.hpp:27] Check failed: Sign::OfNonZero(??) == sign_C?? (- vs. +) [-2147483648; -2147483648; 62]`
<discord-> B​uilderbast. — when I plug in an eccentric anomaly bigger than pi radians I get a true anomaly still smaller than pi
<discord-> B​uilderbast. — should I just calculate the true anomaly as if im coming from the other side and then subtract that from 2 pi?
<discord-> B​uilderbast. — hmmm, im getting nonsensical answers here
<discord-> B​utcher. — Twice on that crash, time to try journalling.
<discord-> B​uilderbast. — had calculator on degrees 😐
<discord-> S​tandecco. — the superior unit
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<discord-> e​gg. — @n9gaming there is a pinned message with some graphs from a paper about long-lifetime lunar orbits
<discord-> n​9gaming. — *ooooh thank you for bringing that to my attention!*
<discord-> s​cimas. — @Builderbast If you go with the standard ellipse equation, (x^2/a^2 + y^2/b^2 = 1) and the Earth is at (ae, 0); then the horizon points on the orbit are (ae - R, ±√((1 - e^2)(a^2 - (ae - R)^2))) where R is the radius of Earth, a is the semi major axis and e is the eccentricity. I think you can convert them to anomalies and get the time period between them.
<discord-> B​uilderbast. — Yeah thats also a way i think
<discord-> B​uilderbast. — I found the easiest though to use an equilateral triangle with mars' radius and the equivalent circular orbital radius to find the mean anomaly
<discord-> s​cimas. — Yeah, whatever works.
<discord-> B​uilderbast. — In the end the teaching assistent told us we were making it to hard ourselves and told us to just use a circular orbit though
<discord-> B​uilderbast. — But i absolutely did learn a lot so not a waste of time
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<discord-> e​gg. — @Butcher huh, integer overflow in the orbit recurrence code? interesting, can you open an issue with your log?
<discord-> e​gg. — (a journal is even better but I think the crash tells us a lot here already)
<discord-> B​utcher. — I ave a journal.
<discord-> B​utcher. — I have a journal. (edited)
<discord-> B​utcher. — Just recreated it, it's about 50-60% occurance rate.
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<_whitenotifier-9244> [Principia] RCrockford opened issue #2811: Crash while descending towards the surface of a body - https://git.io/JIsmq
<_whitenotifier-9244> [Principia] RCrockford edited issue #2811: Crash while descending towards the surface of a body - https://git.io/JIsmq
<discord-> B​utcher. — @egg 2811 opened.
<discord-> B​utcher. — Do you want the log too, or is the journal sufficient?
<discord-> e​gg. — might as well send the log
<discord-> B​utcher. — Info?
<_whitenotifier-9244> [Principia] RCrockford edited issue #2811: Crash while descending towards the surface of a body - https://git.io/JIsmq
<_whitenotifier-9244> [Principia] RCrockford edited issue #2811: Crash while descending towards the surface of a body - https://git.io/JIsmq
<discord-> B​utcher. — Done.
<discord-> e​gg. — yeah INFO
<discord-> B​uilderbast. — when I point a spacecraft at the sun and point it perfectly still, the moment I go into timewarp it spins rapidly
<discord-> B​uilderbast. — could this be a principia thing?
<discord-> B​uilderbast. — hacking gravity makes it not happen
<discord-> e​gg. — yes, because it is not perfectly still, it is just spinning slowly
<discord-> e​gg. — and then if you timewarp, you see time moving faster
<discord-> B​uilderbast. — well it stays still enough that it should be spinning like crazy at 5 x timewarp
<discord-> B​uilderbast. — well it stays still enough that it should not be spinning like crazy at 5 x timewarp (edited)
<discord-> B​uilderbast. — could be a phantom torque thing?
<discord-> l​pg. — maybe it would be helpful to use more specific terms than "like crazy"
<discord-> B​uilderbast. — i'm not sure ksp can show rpm or angular velocity
<discord-> B​uilderbast. — so I'll try to count then
<discord-> B​uilderbast. — is there a way to keep a spacecraft pointed at the sun while timewarping using principia except for spin stabilizing?
<discord-> l​pg. — no
<discord-> e​gg. — not yet
<discord-> l​pg. — well. sort of. with kerbalism, point panels at sun, then leave the vessel
<discord-> e​gg. — yeah but that is cheating :-p
<discord-> l​pg. — we use the tools we're given
<discord-> e​gg. — eventually we may add attitude-keeping, that is relatively tractable
<discord-> e​gg. — until then, spin-stabilization or cheating
<discord-> B​uilderbast. — Alright, well spin stabilization works reasonably
<discord-> l​pg. — The main use case I have where 'no attitude keeping while warping' is a problem is when approaching a maneuver's burn time
<discord-> l​pg. — spin stab isn't a good fit, so I'm stuck having to guess how long ahead of the manuever to stop warping in order to point myself, and then just... waiting
<discord-> l​pg. — spin stab isn't a good fit, so I'm stuck having to guess how long ahead of the maneuver to stop warping in order to point myself, and then just... waiting (edited)
<discord-> B​uilderbast. — Now i did for some reason not crank my antenna up enough to reach the moon when i build this craft 2 months ago 🤦‍♂️
<_whitenotifier-9244> [Principia] pleroy commented on pull request #2809: Fix tolerances for Linux and remove a check - https://git.io/JIssv
<_whitenotifier-9244> [Principia] Pending. Build queued… - 
<_whitenotifier-9244> [Principia] Pending. Building… - http://casanova.westeurope.cloudapp.azure.com:8080/job/Principia/4669/
<discord-> [​experimentalshells?]. — eventually in 2023 or something we'll see the changelog for version Pascal and it just says that stock KSP has been removed and that Principia is a standalone game
<_whitenotifier-9244> [Principia] eggrobin labeled pull request #2809: Fix tolerances for Linux and remove a check - https://git.io/JImNZ
<umbralraptop> Watch Principia have a simulation mode where you can run it and point it at a configuration file in FORTRAN FORMAT
<umbralraptop> *run it from the command line
<discord-> B​utcher. — Principia the text adventure.
<discord-> B​utcher. — "You are in space, there is nothing around, what do you do?"
<umbralraptop> I deploy an interferometer to search for gravity waves
<discord-> [​experimentalshells?]. — ```
<discord-> [​experimentalshells?]. — > orbit
<discord-> [​experimentalshells?]. — Orbiting Earth, a = 6917 km, e = 0.000281, i = 28.47°, Ω = 80.34°, ω = 64.9°
<discord-> [​experimentalshells?]. — Remaining Δv: 1832 m s⁻¹
<discord-> [​experimentalshells?]. — > manœuvre(661, 400, 0, 2.5, CurrentEngines)
<discord-> [​experimentalshells?]. — Enemy Laser Skiff has been disarmed
<discord-> [​experimentalshells?]. — All Enemies Are No Longer a Threat
<discord-> [​experimentalshells?]. — Mission Successful
<discord-> [​experimentalshells?]. — ```
<discord-> [​experimentalshells?]. — ```
<umbralraptop> Children of a Dead Earth?
<discord-> [​experimentalshells?]. — ~$ principia
<discord-> [​experimentalshells?]. — > orbit
<discord-> [​experimentalshells?]. — Orbiting Earth, a = 6917 km, e = 0.000281, i = 28.47°, Ω = 80.34°, ω = 64.9°
<discord-> [​experimentalshells?]. — Remaining Δv: 1832 m s⁻¹
<discord-> [​experimentalshells?]. — > manœuvre(661, 400, 0, 2.5, CurrentEngines)
<discord-> [​experimentalshells?]. — Enemy Laser Skiff has been disarmed
<discord-> [​experimentalshells?]. — All Enemies Are No Longer a Threat
<discord-> [​experimentalshells?]. — Mission Successful
<discord-> [​experimentalshells?]. — ``` (edited)
<discord-> [​experimentalshells?]. — oh wait, the bot doesn't transmit reactions, but yes
<umbralraptop> 🤔
<_whitenotifier-9244> [Principia] Success. Build finished. - http://casanova.westeurope.cloudapp.azure.com:8080/job/Principia/4669/
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