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…
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<_whitenotifier>
[Principia] Growflavor edited issue #3039: Grassmann OK but Gröbner crashes with old RetroRendezvous save - https://git.io/JnpCW
<queqiao->
⟨Standecco⟩ it's unfortunate principia will never support that
<queqiao->
⟨Standecco⟩ unless it's _developmentally interesting_ to calculate ejections from an arbitrary starting trajectory (or eventually with some constraints)
<queqiao->
⟨Zeusbeer⟩ I guess it could be interesting to program GMAT in ksp
<queqiao->
⟨§κyℓαr ♀⟩ GMAT?
<queqiao->
⟨Stonesmile⟩ General Mission Analysis Tool, open source mission planning tool from NASA
<queqiao->
⟨Zeusbeer⟩ It seems to have an API though
<queqiao->
⟨Zeusbeer⟩ Sounds like a deep rabbit hole however
<queqiao->
⟨§κyℓαr ♀⟩ Its sad that nasa uses such a stupid license, it has some vague probably accidental restrictions and compatibility issues lol
<queqiao->
⟨§κyℓαr ♀⟩ Having some more clear wording would probably fix that too.
<queqiao->
⟨§κyℓαr ♀⟩ Or just using a more normal license like apache, mit, gpl, ect.
<queqiao->
⟨(ᴇxᴘᴇʀɪᴍᴇɴᴛᴀʟshells)⟩ it does use Apache
<queqiao->
⟨§κyℓαr ♀⟩ Did they release different versions under different licenses?
<queqiao->
⟨(ᴇxᴘᴇʀɪᴍᴇɴᴛᴀʟshells)⟩ perhaps
<queqiao->
⟨(ᴇxᴘᴇʀɪᴍᴇɴᴛᴀʟshells)⟩ R2020a is under Apache, that's all I know
<queqiao->
⟨§κyℓαr ♀⟩ ok interesting
<queqiao->
⟨§κyℓαr ♀⟩ their site says its using their nosa bs while sourceforge is saying another thing
<queqiao->
⟨§κyℓαr ♀⟩ their site says its using their nosa bs while sourceforge is saying apache (edited)
<queqiao->
⟨§κyℓαr ♀⟩ yknow
<queqiao->
⟨§κyℓαr ♀⟩ nasa should probably just have everything literally in the public domain
<queqiao->
⟨§κyℓαr ♀⟩ either public domain or gpl :thonk: either way if its apache its free so thats good
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<queqiao->
⟨egg⟩ Support what: auto-win GTOC for you? not happening, obviously; find high-energy transfers? MechJeb knows how to do that, so I guess it would be a matter of defining an API to import a plan of impulsive manœuvres and have @XKdiver call it, which might be a semidecent starting point to tweak an interplanetary trajectory from a parking orbit (planning from the ground would be nice but I am not sure how
<queqiao->
⟨egg⟩ The GMAT-into-licensing discussion is neither relevant nor interesting; while I am happy being lax with the concept of topic here, can we avoid filling a page of backlog with random daydreaming about integrating with the shiny NASA tool of the day?
<queqiao->
⟨egg⟩ We have our own numerics, and astronomy libraries instead of kludging things together out of, say, boost math and ERFA, it should be quite obvious that we are not interested in building a massive layer of glue with *insert random shiny tooling here*. If there are specific features of GMAT that you would like to see, discussing those might lead somewhere (at least to awareness of the existence of a ne
<queqiao->
⟨egg⟩ The GMAT-into-licensing discussion is neither relevant nor interesting; while I am happy being lax with the concept of topic here, can we avoid filling a page of backlog with random daydreaming about integrating with the shiny NASA tool of the day?
<queqiao->
⟨egg⟩ We have our own numerics and astronomy libraries instead of kludging things together out of, say, boost math and ERFA, it should be quite obvious that we are not interested in building a massive layer of glue with *insert random shiny tooling here*. If there are specific features of GMAT that you would like to see, discussing those might lead somewhere (at least to awareness of the existence of a nee
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<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ If it is entirely a product of work by a government employee as part of their job, then it is, I think
<queqiao->
⟨lamont⟩ cbrt!
<queqiao->
⟨lamont⟩ C# now has a Math.Cbrt() but can't use it yet in KSP
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Has the bugging about the issues with native dll in gamedata been fruitful yet?
<queqiao->
⟨§κyℓαr ♀⟩ Nasa has their work published in their own license which has dubious wording so some people making foss tools avoid them while others don't, depending on how it could be interpreted.
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<queqiao->
⟨rocketman⟩ I just managed to get a probe to Duna in principia, not that impressive but it was interesting learning how to do it regardless. Used mechjeb for the general transfer window and then fine tuned with the maneuver planner and duna relative reference frame
<queqiao->
⟨rocketman⟩ yeah yeah yeah I know
<queqiao->
⟨rocketman⟩ my computer can barely handle RP-1 as it is, let alone RP-1 + principia
<queqiao->
⟨rocketman⟩ but I guess I could try bare minimum RSS + principia just to test some things
<queqiao->
⟨Damien⟩ I used to use RSS/SMURFF/principia for practice
<queqiao->
⟨Damien⟩ it's a valid setup
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<queqiao->
⟨Damien⟩ practice all the principia tricks without the handicap of RO
<queqiao->
⟨rocketman⟩ good to know, thanks
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<queqiao->
⟨Damien⟩ np
<queqiao->
⟨Damien⟩ It's good to use to speedrun all the major milestones (orbit, rendezvous, moon transfers, interplanetary etc) to then bring those skills back to RO
<queqiao->
⟨Damien⟩ And you can also use it as a sandbox to do stuff like lagrange points and low energy transfers
<queqiao->
⟨Damien⟩ Once you've mastered it on there you'll be able to use them in RO to flex on people with your skills
<queqiao->
⟨Damien⟩ Or like in my case just do that and forget about RO
<queqiao->
⟨Damien⟩ KSP is a principia mod now
<queqiao->
⟨egg⟩ yeah stock is a good way to learn Principia, with the exception of low-orbit things that are influenced by extended body effects
<queqiao->
⟨Damien⟩ It may have come up before but is it not worth making kerbin oblate by default? I imagine a lot of stock principia players are missing out
<queqiao->
⟨Damien⟩ I know you can write a config for it but most don't know that and I dunt see the harm in having that happen automatically
<queqiao->
⟨Butcher⟩ Give it mascons.
<queqiao->
⟨Damien⟩ That would require a gravity map and egg doesn't like fakery
<queqiao->
⟨Damien⟩ Oblateness is pretty trivial though
<queqiao->
⟨egg⟩ well, either way it requires inventing an internal structure; oblateness depends on what it is
<queqiao->
⟨egg⟩ (is most of the mass in a core, etc)
<queqiao->
⟨egg⟩ it would be nice to have that, but given how implausible the planets are it is a tricky exercise to make up something sensible
<queqiao->
⟨Butcher⟩ The core is made of depleted unobtanium.
<queqiao->
⟨egg⟩ eggsactly
<queqiao->
⟨Damien⟩ I know I used that config once and did something with 0.2 to make an equatorial bulge by my memory eludes me
<queqiao->
⟨Damien⟩ I know I used that config once and did something with 0.2 to make an equatorial bulge but my memory eludes me (edited)
<queqiao->
⟨Butcher⟩ What's the density of kerbin? Wouldn't it need to be solid osmium or something?
<queqiao->
⟨egg⟩ yeah something like that
<queqiao->
⟨Damien⟩ Having sunsync and other precessing orbits possible by default would also feed into kerbalism contracts one day
<queqiao->
⟨egg⟩ and a differentiated body is going to get a different dynamical oblateness from its rotation than a homogeneous one iirc
<queqiao->
⟨egg⟩ true
<queqiao->
⟨egg⟩ (speaking of which, I should poke at that)
<queqiao->
⟨Damien⟩ Aside from the gamedata issue, is 1.12 causing you many problems @egg ?
<queqiao->
⟨egg⟩ have yet to look at it
<raptop>
1.12.1 is out apparently
<queqiao->
⟨egg⟩ do we have a change log?
<queqiao->
⟨Damien⟩ this is my surprised face 😐
<raptop>
...not sure what AOORE is and why it breaks saves
<raptop>
Changelog is just a single bugfix
<raptop>
* Fix AOORE breaking saves without Making History DLC installed
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Black hole core
<queqiao->
⟨Butcher⟩ Neutron star material maybe.
<queqiao->
⟨Butcher⟩ Maybe it's a Dyson sphere around a tiny black hole.
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<raptop>
Kerbal planets are scrith shells around naked singularities
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ This is what I always though
<queqiao->
⟨egg⟩ in practice you would probably have to scale it up to a « reasonable size » at constant mass, think for a while what the « reasonably-sized planet » might be made of, get a geopotential model out of that, and then keep the same harmonics as you scale it back down into nonsense
<queqiao->
⟨egg⟩ this would, I think, be the solution that is in keeping with the spirit of KSP
<queqiao->
⟨egg⟩ but it is not necessarily trivial
<queqiao->
⟨egg⟩ (actually at constant surface gravity, not constant mass)
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Kerbal densities are relatively reasonable, but kerbol system densities are weird
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Small scale, the densities in the universe make sense, but not large scale
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Would the observed effects be possible with weird curvatures that make volume much larger than apparent volume the larger apparent volume gets?
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Kerbal densities are relatively reasonable, but kerbol system densities are weird
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Small scale, the densities in the universe make sense, but not large scale
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Would the observed effects be possible with weird curvatures of space that make volume much larger than apparent volume the larger apparent volume gets? (edited)
<queqiao->
⟨egg⟩ no, let’s not try to shoehorn in some differential geometry that has no relation to reality
<queqiao->
⟨egg⟩ the high-density planets thing is mostly designed as « reasonable surface gravities, but made small so things are fast » aiui
<queqiao->
⟨egg⟩ so if we take that interpretation, Kerbin should have coefficients in keeping with an Earth that spins four times faster (thus a bit more oblate than Earth, probably; for the higher coefficients we could stare at the geography to see if there should be interesting features, there are definitely large-scale craters)
<queqiao->
⟨egg⟩ (then again broad features of the gravitational field can be somewhat independent of geography, consider india)
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ I thought that Earth was more oblate than it would be otherwise because of the ice age ice sheet thickness
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Assuming Kerbin did not have that extreme period, how different would its oblateness realistically be compared to if it did?
<queqiao->
⟨egg⟩ yeah glacial rebound is a thing, but I would expect the effect size to be smaller than rotation rate; I would have to actually look up some models though
<queqiao->
⟨egg⟩ TL;DR it would probably be a good idea to have some gravity models for stock, but it’s not completely trivial to come up with semi-reasonable ones.
<raptop>
The stock planets are spheres with topography, rather than oblate.
<raptop>
In practice I think the topography makes some prolate?
<queqiao->
⟨egg⟩ yeah there is the broader problem that the figure doesn’t match, but this is an issue in RSS too
<queqiao->
⟨Butcher⟩ Which figure doesn't match?
<queqiao->
⟨egg⟩ of the earth
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Is that so the atmosphere fits right?
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Since atmospheres are perfect spheres
<queqiao->
⟨egg⟩ and the altitudes, which are just distances from the centre minus the conventional radius, and the ocean, which is at altitude 0, and…
<queqiao->
⟨Butcher⟩ Ksp ocean at 0 is a pain.
<raptop>
Yeah. AFAIK, the underwater parts are in fact below 0 altitude.
<raptop>
Also Eeloo used to have some negative altitude valleys
<queqiao->
⟨Butcher⟩ It means that most other bodies have incorrect relief.
<raptop>
(not sure if it still does)
<queqiao->
⟨Butcher⟩ I tried it with the moon and Mars and you could splash down.
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ The Mun did the last time I played stock
<queqiao->
⟨egg⟩ it’s a problem with Earth too, besides the fact that you can’t have an oblate earth it means high-altitude lakes are in deep pits
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ So that's why they made non-deadly water for the Admin Building
<queqiao->
⟨Butcher⟩ Also death Valley is flooded.
<raptop>
Butcher: I'm blaming climate change for that
<queqiao->
⟨egg⟩ that is easy to solve, we just need to solve it IRL
<queqiao->
⟨egg⟩ that is easy to solve, we just need to flood it IRL (edited)
<queqiao->
⟨egg⟩ lowering the surface of 青海湖 by three kilometres might be a taller order
<queqiao->
⟨Butcher⟩ Mars is all far too high because I had to push everything above 0.
* raptop
should probably not try to read hanzi as if they're kanji
<queqiao->
⟨Butcher⟩ Or you splash into invisible water.
<raptop>
3 km O_o
* raptop
is reminded that Lake Baikal is only like 1.5 km deep
<queqiao->
⟨Butcher⟩ This means that olympus mons is 29km high.
<raptop>
It's fine, what's a 40% error?
<queqiao->
⟨Butcher⟩ 10km is nothing.
* raptop
wants to say that the real Olympus Mons has a 21 or 22 km base-peak height
<queqiao->
⟨Butcher⟩ 19 I thought? But I'm going off memory.
<queqiao->
⟨egg⟩ in principle you should be able to compensate for that by lowering the radius? the altitude readings will be silly either way, but at least the surface will be in the right place
<raptop>
Hrm, does that mean that Rheasilvia has similiar problems?
<queqiao->
⟨Butcher⟩ @egg true, I'm not sure what that will do to orbital stuff though.
<queqiao->
⟨Butcher⟩ I'd rather break the surface than orbits.
<queqiao->
⟨egg⟩ not sure why it would break the orbits?
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<queqiao->
⟨Butcher⟩ Am orbit at a given alt would be different from real life.
<queqiao->
⟨Butcher⟩ Since they are measured from the "radius"
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<queqiao->
⟨egg⟩ right, if you use altitude rather than semimajor axis; but on an oblate body using altitude is dangerous (unless you are trying not to hit terrain, and in that case you are back to surface issues)
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<queqiao->
⟨egg⟩ in any case, shifting things above 0 seems tractable; but when you actually need to have water it gets trickier, and you end up with eight-kilometre slopes down to a lake https://i.imgur.com/cMfV9Bh.png
<queqiao->
⟨egg⟩ (those mountains are a bit too high but that’s nothing compared to the lake being too far down)
<queqiao->
⟨Damien⟩ *oblate kerbin would be nice
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ KSP IS COMPLETELY BROKEN*
<queqiao->
⟨Butcher⟩ A weird effect is ksp's height from terrain stuff doesn't work above about 20km alt, which means it starts working roughly as you hit the terrain on Mars.
<raptop>
hah
<raptop>
I assume that this is a quadtree thing and how terrain resolution works with distance?
<queqiao->
⟨egg⟩ welcome to the wonderful world of KSP modding, how may I take your order? The only thing on the menu here is purple noodles by the way
<queqiao->
⟨Butcher⟩ I think it's just a dumb optimisation.
<queqiao->
⟨Butcher⟩ You can query the pqs directly and get valid terrain height.
<queqiao->
⟨egg⟩ (fuchsia noodles, specifically)
<queqiao->
⟨Damien⟩ this reminds me of the physx bug
<queqiao->
⟨Butcher⟩ I want periwinkle blue.
<queqiao->
⟨Butcher⟩ Which one? 😆
<queqiao->
⟨Damien⟩ *minor issue
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ ...
<queqiao->
⟨Damien⟩ ....
<queqiao->
⟨Damien⟩ PHYSX IS CRAP*
<queqiao->
⟨egg⟩ yeah that was good
<queqiao->
⟨Butcher⟩ I had a marvelous dancing sky crane.
<queqiao->
⟨Damien⟩ was that the universe rotation thing?
<queqiao->
⟨Damien⟩ I can't remember what the original issue was
<queqiao->
⟨egg⟩ no rigid body rotation
<queqiao->
⟨Damien⟩ ah
<queqiao->
⟨egg⟩ when we learned that PhysX does not even try doing rigid body rotation
<queqiao->
⟨Butcher⟩ Physx is not very good at conservation of energy.
<queqiao->
⟨egg⟩ yeah but here it’s not even being bad at conservation laws for numerics reasons, like many engines are because Euler integration, no, it’s not even trying to apply the laws of physics
<queqiao->
⟨Butcher⟩ It's still annoying when you hit the grind and physx says, "you rebound off the ground with 120% of your original energy." 🤡
<queqiao->
⟨Butcher⟩ It's still annoying when you hit the ground and physx says, "you rebound off the ground with 120% of your original energy." 🤡 (edited)
<queqiao->
⟨Butcher⟩ Any ideas on the jump stutter yet?
<raptop>
This is where Orbiter slinks away in embarassment
<queqiao->
⟨Butcher⟩ See also various kraken drives.
<queqiao->
⟨egg⟩ not yet, I made a journal but I have not yet investigated
<queqiao->
⟨Butcher⟩ I saw the update, I too have seen it jumping now.
* queqiao-
⟨egg⟩ imagines Butcher freezing every time a cat jumps
<queqiao->
⟨rocketman⟩ principia isn't using runge-kutta, right? what sort of algorithms is it using at the moment for predictions
* raptop
waits for rocketman to be drowned under a sea of papers
<queqiao->
⟨rocketman⟩ oh hell yeah
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ What do you think the screaming is a result of?
<queqiao->
⟨rocketman⟩ oh hell yeah, this is what I live for (edited)
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ What do you think the screaming is a result of? - paper drowning (edited)
<queqiao->
⟨egg⟩ 𒄿𒈾𒀀𒀊𒁀𒊭𒁾𒎌𒉈𒁍𒌑𒌝 indeed
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ What does that say? The online ancient Akkadian to English translator is wanting me to pay now
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ I see a truncated Sierpinski triangle
<queqiao->
⟨rocketman⟩ is principia switching between the methods for different use cases?
<raptop>
...what do you pay an Akkadian to English translator in, oxen? Barley? Copper bars?
<queqiao->
⟨egg⟩ it says *i-na* A.AB.BA *ša* DUB-MEŠ *ṭè-bu-ú-um*, which reads *ina tâmtim ša ṭuppī ṭebûm*, which roughly translates to « submerged in the sea of tablets »
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ I had just started doing it word by word in wiktionary 😂
<queqiao->
⟨Butcher⟩ @egg I do have a new cat today. Not much jumping.
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ What happened?
<queqiao->
⟨Butcher⟩ Dunno, found with an abscess. Vet has been trying to drain it.
<queqiao->
⟨rocketman⟩ oh no...
<queqiao->
⟨Butcher⟩ So far he's eaten two plates of food in six hours which I think is a good sign.
<queqiao->
⟨Paculino (ŝi/ri/she/they)⟩ Is he underweight?
<queqiao->
⟨egg⟩ we use one fixed-step method for the ephemeris (the planets and moons), one (with a smaller step) for the histories (of the vessels) in free fall, another (adaptize-stepsize) one for bits that are under thrust and recent history, and a different (adaptive-stepsize) method for the flight plan & prediction. Which ones and which step sizes (or tolerances) is, to an extent, configurable; we use different
<queqiao->
⟨Butcher⟩ A little, 3.4kg.
<queqiao->
⟨Butcher⟩ Bad teeth, can't close his mouth properly.