raptop changed the topic of #principia to: READ THE FAQ: http://goo.gl/gMZF9H; The current version is Galois. We currently target 1.8.1, and 1.9.1. <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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Kitten Dispenser. — with principia, does upgrading the mission control to allow flight planning do anything?
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Skylar. — I get that it could take time and effort you would prefer to allocate towards other tasks, but a lot of players (including me) would actually want and benefit from basic stationkeeping
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Skylar. — I get that it could take time and effort you would prefer to allocate towards other tasks, but a lot of players (including me) would actually want and benefit from basic stationkeeping, whether it would be worth it to add relative to the effort might be another story tho. (edited)
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scimas. — @Kitten Dispenser Yes. I don't remember exactly which mission control / tracking station upgrade it is, but one of them enables the maneouvre node tracking ability (showing the node on navball).
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sichelgaita. — @Skylar Whenever someone writes the phrase "simple station keeping" it becomes apparent that they have not thought of the problem for more than 10 seconds. There is a [forum post](https://forum.kerbalspaceprogram.com/index.php?/topic/162200-wip181-191-1101-principia%E2%80%94version-gateaux-released-2020-09-17%E2%80%94n-body-and-extended-body-gravitation-axial-tilt/&do=findComment&comment=363
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sichelgaita. — @Skylar Whenever someone writes the phrase "simple station keeping" it becomes apparent that they have not thought of the problem for more than 10 seconds. There is a forum post (https://forum.kerbalspaceprogram.com/index.php?/topic/162200-wip181-191-1101-principia%E2%80%94version-gateaux-released-2020-09-17%E2%80%94n-body-and-extended-body-gravitation-axial-tilt/&do=findComment&comment=3630
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[Principia] pleroy opened pull request #2723: Tolerances for Linux/macOS - https://git.io/JUE7j
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egg. — @Skylar I have no doubt that having that would benefit the user experience, in much the same way that having a team of astrodynamics postdocs working on Principia (and @lamont’s MechJeb optimizers) full time for the next few years would benefit its development. Neither of those is happening.
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egg. — As @sichelgaita said, just because it is easy to gesture in the general direction of a problem does not mean that solving it is easy.
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egg. —
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egg. — Yes, it is true that the absence of stationkeeping poses artificial constraints on mission design (so does the patched conics experience, just in different places: no lowering your Δv budget via low-energy trajectory in stock, no relays at Lagrange points, etc.).
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egg. — My point was that there are workarounds to those limitations for any given task: plenty of orbits are stable (and I would argue that it can be interesting to learn which ones are and are not, and what the reasons for that are).
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Zeusbeer. — feel like a fix for 2400 would fix the user experience a lot more than stationkeeping
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Zeusbeer. — there isn't really a need for constant station keeping in most missions anyway, only for unstable orbits/lagrange
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Stonesmile. — If the need for someone to have stationkeeping is large, they can write a kOS script to perform the burn themself (and quickly realize why egg isn't implementing stationkeeping)
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Zeusbeer. — I'm afraid to make a suggestion because egg will get angry but it would skip point 2 and 3 made in the forum post in cost of some realism
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Zeusbeer. — ~~where you identify the orbit and there's a button that says stationkeep and it would fix the orbit in place in cost of deltaV that is already known for that type of orbit~~
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Zeusbeer. — ~~note the reason I lined my sentence~~
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Zeusbeer. — ~~because nothing is easy to program~~
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egg. — > I'm afraid to make a suggestion because egg will get angry
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egg. — @Zeusbeer yes, you should have stopped there :-p
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egg. — — Identifying orbits is hard, identifying intentions is impossible;
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egg. — — « fixing an orbit in place » is either underspecified or not at all what stationkeeping does;
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egg. — — subtracting some Δv cost would be one of the hardest parts of the KSP interaction.
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Zeusbeer. — I was afraid of this reaction d-:
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egg. — but it is an opportunity to learn something about what stationkeeping is, or how it works (to paraphrase @Damien, every day is a school day here)
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egg. — taking an Earth orbit as an example, any orbit drifts from what it would do in a Keplerian world (apsidal and nodal precessions). You cannot, and do not, fight those drifts, that would be way too costly. So you have an orbit that moves around in a reasonably simple way, and then you correct from time to time so that things don’t depart too much from this « simply-perturbed » model
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egg. — note that when you perform a correction, your satellite typically is not operational for its mission (telecoms, satnav, whatever)
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Stonesmile. — I just placed a relay sat at EM-L2 - how would you tell a generic script to 'station keep' that?
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egg. — so you don’t just do that at every revolution
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egg. — what you correct, how much, & how often you correct is going to heavily depend on the mission.
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Zeusbeer. — yes
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egg. — On one extreme, the GPS planes are comparatively very poorly kept, you get a couple of degrees between satellites that are nominally part of the same plane, and they are all over the place along the plane, because you don’t really care about what their orbits are, just that they should be far apart, that you should see enough at any time, and that their orbits should be well-known.
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egg. — on the other extreme you have oceanography satellites, e.g., TOPEX/Poséidon, which keep their ground tracks to something like a kilometre
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Stonesmile. — What we in the community can mostly contribute with is finding bugs
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egg. — on the other extreme you have oceanography satellites, e.g., TOPEX/Poséidon, which keep their ground tracks to something below a kilometre (edited)
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egg. — > note that when you perform a correction, your satellite typically is not operational for its mission (telecoms, satnav, whatever)
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egg. — attitude-keeping might come someday, because it is comparatively much simpler: there you do continuously keep some predefined attitude (with some mild fudging around singularities), the corrections are not discrete and you don’t have to worry about perturbed orbital dynamics
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egg. — yes, if the spacecraft is not capable of attitude-keeping you have a problem, and that translates to somehow detecting that on the Principia side.
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Stonesmile. — @egg Would it be possible to add some kind of tool to help with setting the manouvre time to a particular event such as a Pe on the prediction?
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Damien. — Is a dead zone of angular momentum a potential answer? Rotation <x=0
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Damien. — Then it's on you to stabilise it
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egg. — @Stonesmile maybe, though the UI is a mess already so that is a big impediment to moar features
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egg. — tax forms in space
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Stonesmile. — Yeah, I guess it's not a feature that is worth the UI realestate
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egg. — @Damien yeah that does not seem unreasonable
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Standecco. — @egg did anything come out of that guy who was building a new UI with the unity system?
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Standecco. — did you like those mockups? I _could_ (no promises, will probably run out of free time in less than a week when classes start) try reproducing those with the Unity UI system
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Standecco. — did you like those mockups? I _could_ (no promises, will probably run out of free time in less than a week, when classes start) try reproducing those with the Unity prefab UI system (edited)
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[Principia] pleroy commented on issue #2722: Crash during flight planning on Linux - https://git.io/JUEpr
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[Principia] pleroy closed issue #2722: Crash during flight planning on Linux - https://git.io/JU0pV
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Standecco. — (also yes I have read the issue and I know that you have expressed your opinion on those there, but I was wondering if it had changed with time)
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egg. — @Standecco OK but try it with the plotting frame selector, which is one very small (and very ugly) thing, and just try to make that tiny bit work with the new framework. Giant changes out of the blue have negative value.
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scimas. — When replicating real life missions in KSP, what do you guys search for? What I'm looking for is information like what was the launch profile, when the manoeuvres were executed etc. Either search keywords or even specific websites you know would be great.
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Standecco. — @egg alright, I'll let you know how things progress
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Standecco. — you'll probably have to answer a lot of stupid questions on basic things
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Damien. — @scimas NASA NTRS search page is good for historical mission docs
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Kitten Dispenser. — I'm trying to figure out how I should time my launch from Cape Canaveral for my moon impact/flyby probe
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Kitten Dispenser. — any advice on eyeballing it? (i also probably shouldn't have deprived myself of sleep when planning on playing ksp with principia)
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Stonesmile. — For eyeballing it one way is to launch into a polar orbit and try to get that orbit 4 days ahead of the moon, so that you can do TLI and hit the moon
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Kitten Dispenser. — forgot to say, i don't need to do a direct ascent, this thing is for a parking orbit type mission
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Kitten Dispenser. — forgot to say, i don't need to do a direct ascent, this design is for a parking orbit type mission (edited)
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Kitten Dispenser. — should I still try a polar launch?
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Stonesmile. — Same advice
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Stonesmile. — That way there is the least for a brain to figure out
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Kitten Dispenser. — okay, thanks
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Kitten Dispenser. — my problem is that this rocket can't get the spacecraft into a polar orbit... at least, not without loading the solid kick stage with more fuel and doing a direct ascent
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lpg. — I finally managed to wrap my brain around how to eyeball eastward launches. it's essentially the same technique as polar, the orbital plane is just different
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lpg. — put the cape (or any other launch site) right in the middle of the Earth. Your eventual orbital plane is going to be a horizontal line going through it. Extend that line to the moon's orbit, that's where you'll intersect it. Same logic launch when the moon is 3-4 days away from that point
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Kitten Dispenser. — thanks!
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lpg. — put the cape (or any other launch site) right in the middle of the Earth. Your eventual orbital plane is going to be a horizontal line going through it. Extend that line to the moon's orbit, that's where you'll intersect it. Same logic: launch when the moon is 3-4 days away from that point (edited)
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Kitten Dispenser. — so, there's only a few good times to launch in a lunar month, all in the span of a few days? or am i misunderstanding
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lpg. — you get 2 windows a day just like polar
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Kitten Dispenser. — it looks like I have to be really precise with when i launch to be able to impact the lunar surface with 3.2km/s of dV
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Stonesmile. — Another way is to use a kOS script to get the timing correct
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lpg. — err. scratch that. 1 window a day. polar you can launch on either side of the planet (going north vs going south), that's not true for due-east
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scimas. — @egg Why do RSS saves integrate 1 year before game start? I mean - is the reason gameplay related (It is just a choice to start in 1951 and the integration is not needed technically) or is it something necessary for some reason?
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egg. — Ancient confusion on whether RSS should start in 1950 or 1951, we use a data dump that starts in 1950; @NathanKell might recall some of that discussion. This has the unintended but nice side effect of giving you one year of celestial history, instead of giving you bodies with no past like in stock
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NathanKell. — Yes, some of that derived from, before having date/time display being moddable, the conversion of "both years ending in the same digit" being a far easier mental conversion than "KSP year is 1 behind real year"
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egg. — ah yes
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egg. — (which probably gives you a hint on the value of "ancient" here)
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egg. — back when @NathanKell roamed the earth
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NathanKell. — around .28 probably, or .90 at the latest
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NathanKell. — oh lol maybe there wasn't a .28
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scimas. — Okay, but there isn't anything stopping anyone from generating proper ephemeris for a given date and starting the game without additional integration, right?
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egg. — sure
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egg. — you would not get the pretty lines of the past year though
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NathanKell. — Yes, for some notional "present day RSS" you probably want ephemerides of ~2000 or later.
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scimas. — Thanks, got it. I'm thinking of downloading the ephemeris for every 5 years since 1950 while you guys deal with # 2400. Any tips for generating data for multiple bodies in a single request? I figured out how to get the ephemeris from HORIZONS web interface, but it seems to allow only one body at a time.
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egg. — you can send an email and get, uh, dozens of emails back
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egg. — and then you export them and mangle the files